METHODS FOR PROCESSING HYDROCARBON FEEDSTOCKS

Abstract

Methods for processing a hydrocarbon feedstock may include cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a modified zeolite in the presence of hydrogen to form an intermediate cracked product and steam cracking at least a portion of the intermediate cracked product to form a steam cracked product. The intermediate cracked product may include at least 30 wt. % of one or more linear alkanes. The modified zeolite may include a microporous framework. The microporous framework may include at least silicon atoms and oxygen atoms. The modified zeolite also includes a plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms, wherein each of the bridging oxygen atoms bonded to the Group 4-6 metal atoms bridges one of the plurality of the Group 4-6 metal atoms and a silicon atom of the microporous framework.

Description

TECHNICAL FIELD

The present disclosure generally relates to methods for processing hydrocarbons, more specifically, methods for cracking hydrocarbons.

BACKGROUND

Alkenes, such as ethylene are valuable chemical materials. Ethylene, also known as ethene, is a colorless and odorless hydrocarbon gas with the chemical formula C₂H₄. It is one of the most important building blocks in the chemical industry, with a global annual production exceeding 170 million metric tons. Ethylene is widely used as a raw material for the manufacture of a wide range of products, including plastics, solvents, fibers, and many other chemical intermediates.

BRIEF SUMMARY

Alkenes may be produced commercially by various processes, including steam cracking of hydrocarbons. In steam cracking, these hydrocarbons are heated in the presence of steam, which breaks the carbon-carbon bonds and produces a mixture of hydrocarbon gases, including ethylene. Linear alkanes may be used as feedstock for steam cracking processes as they may be more selective to produce ethylene. Branched alkanes may be less selective for producing ethylene. Some conventional hydrocracking products may include a significant portion of branched alkanes. Such conventional hydrocracking products may be used as feedstock at a cost of decreased ethylene production. Additionally, such conventional hydrocracking products may undergo reverse isomerization before being used as a feedstock for a steam cracking process to increase the proportion of linear alkanes being fed to the steam cracking process.

It has been presently discovered that using the modified zeolites described herein as a cracking catalyst may result in a product comprising a significant portion of linear alkanes, such that the product may be used as a feedstock for a steam cracking process without first undergoing reverse isomerization. Without being bound by any particular theory, it is believed that the zeolites presently disclosed, which include Group 4-6 metal atoms bonded to four bridging oxygen atoms, may have enhanced selectivity for linear alkanes when used as a cracking catalyst. Such embodiments may allow for processing of relatively long-chained alkanes into alkenes without the need for a reverse isomerization reaction, since a reduced yield of branched alkanes are formed in the initial cracking reaction upstream of the steam cracking.

According to one or more embodiments of the present disclosure, a method for processing a hydrocarbon feedstock may comprise cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a modified zeolite in the presence of hydrogen to form an intermediate cracked product and steam cracking at least a portion of the intermediate cracked product to form a steam cracked product. The hydrocarbon feedstock may comprise at least 20 wt. % of one or more alkanes. The intermediate cracked product may comprise at least 30 wt. % of one or more linear alkanes. The modified zeolite may comprise a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm. The microporous framework may comprise at least silicon atoms and oxygen atoms. The modified zeolite also comprises a plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms, wherein each of the bridging oxygen atoms bonded to the Group 4-6 metal atoms bridges one of the plurality of the Group 4-6 metal atoms and a silicon atom of the microporous framework.

Additional features and advantages of the described embodiments will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the described embodiments, including the detailed description which follows, the claims, as well as the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

FIG. 1A depicts a transmission electron microscopy (TEM) micrograph of the zeolite comprising mesopores ordered with cubic symmetry of Example 1;

FIG. 1B depicts a TEM micrograph of the zeolite comprising mesopores ordered with cubic symmetry of Example 1;

FIG. 1C schematically depicts a FAU unit cell schematic and their arrangement to provide mesopores with cubic symmetry according to one or more embodiments described herein;

FIG. 2A depicts the low angle x-ray diffraction (XRD) pattern of the zeolite comprising mesopores ordered with cubic symmetry of Example 1;

FIG. 2B depicts a high angle XRD pattern of the zeolite comprising mesopores ordered with cubic symmetry of Example 1;

FIG. 3 depicts a Fourier-transform infrared spectroscopy (FTIR) spectrum of the titanium modified zeolite of Example 3;

FIG. 4A depicts a ¹H MAS NMR spectrum of the intermediate zeolite of Example 2;

FIG. 4B depicts the two-dimensional ¹H-¹H double-quantum and triple-quantum spectra of the intermediate zeolite of Example 2;

FIG. 5 depicts a ¹³C CP/MAS NMR spectrum of the intermediate zeolite of Example 2;

FIG. 6 depicts a 2D HETCOR spectrum of the intermediate zeolite of Example 2;

FIG. 7 depicts a ¹H MAS NMR spectrum of the intermediate zeolite of Example 2; and

FIG. 8 depicts a FTIR spectrum of the titanium modified zeolite of Example 3.

Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.

DETAILED DESCRIPTION

According to some embodiments, the present disclosure is directed to methods for processing hydrocarbon feedstocks. The methods include cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a modified zeolite in the presence of hydrogen to form an intermediate cracked product. The intermediate cracked product comprises one or more linear alkanes. The intermediate cracked product may be steam cracked to form a steam cracked product. Without intending to be bound by theory, the modified zeolites described herein may be used to produce an intermediate cracked product comprising linear alkanes, such that the intermediate cracked product may be used as a feedstock for a steam cracking process without undergoing a reverse isomerization process prior to steam cracking.

In one or more embodiments, the methods for processing hydrocarbon feedstocks may comprise cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a catalyst containing modified zeolite in the presence of hydrogen to form an intermediate cracked product. In one or more embodiments, the hydrocarbon feedstock may comprise one or more alkanes and one or more aromatic hydrocarbons. In one or more embodiments, the alkanes may be one or more alkanes selected from linear alkanes, branched alkanes, and cyclic alkanes. For example, without limitation, the hydrocarbon feedstock may comprise paraffinic hydrocarbons, naphthenic hydrocarbons, or both.

In one or more embodiments, the hydrocarbon feedstock may comprise at least 20 wt. % alkanes. For example, the hydrocarbon feedstock may comprise at least 20 wt. % alkanes, at least 30 wt. % alkanes, at least 40 wt. % alkanes, or at least 50 wt. % alkanes. In one or more embodiments, the hydrocarbon feedstock may comprise from 20 wt. % to 60 wt. % paraffinic hydrocarbons. For example, the hydrocarbon feedstock may comprise paraffinic hydrocarbons from 20 wt. % to 60 wt. %, from 30 wt. % to 60 wt. %, from 40 wt. % to 60 wt. %, from 50 wt. % to 60 wt. %, from 20 wt. % to 50 wt. %, from 20 wt. % to 40 wt. %, from 20 wt. % to 30 wt. %, or any range or combination of ranges formed from these endpoints. In one or more embodiments, the hydrocarbon feedstock may comprise from 20 wt. % to 60 wt. % naphthenic hydrocarbons. For example, the hydrocarbon feedstock may comprise naphthenic hydrocarbons from 20 wt. % to 60 wt. %, from 30 wt. % to 60 wt. %, from 40 wt. % to 60 wt. %, from 50 wt. % to 60 wt. %, from 20 wt. % to 50 wt. %, from 20 wt. % to 40 wt. %, from 20 wt. % to 30 wt. %, or any range or combination of ranges formed from these endpoints.

In one or more embodiments, the hydrocarbon feedstock may comprise from 1 wt. % to 10 wt. % aromatic hydrocarbons. For example, the hydrocarbon feedstock may comprise aromatic hydrocarbons from 1 wt. % to 10 wt. %, 3 wt. % to 10 wt. %, 5 wt. % to 10 wt. %, 7 wt. % to 10 wt. %, 9 wt. % to 10 wt. %, 1 wt. % to 8 wt. %, 1 wt. % to 6 wt. %, 1 wt. % to 4 wt. %, 1 wt. % to 2 wt. %, or any range or combination of ranges formed from these endpoints.

In one or more embodiments, the hydrocarbon feedstock may comprise C₁₅ to C₁₀₀ alkanes. The C₁₅ to C₁₀₀ alkanes may be linear alkanes, branched alkanes, cyclic alkanes, or any combination of these. In one or more embodiments, the hydrocarbon feedstock may comprise at least 90 wt. % C₁₅ to C₁₀₀ alkanes. For example, the hydrocarbon feedstock may comprise at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % C₁₅ to C₁₀₀ alkanes. In some embodiments, the hydrocarbon feedstock may comprise C₂₀ to C₅₀ alkanes. The hydrocarbon feedstock may comprise at least 90 wt. %, at least 95 wt. %, at least 99 wt. % C₂₀ to C₅₀ alkanes in some embodiments.

In one or more embodiments, at least 90% of the hydrocarbon feedstock may have a boiling point of greater than or equal to 270° C. For example, at least 90% of the hydrocarbon feedstock may have a boiling point of greater than or equal to 270° C., 290° C., 310° C., 330° C., 340° C., 350° C., 360° C. or 370° C. In one or more embodiments, at least 90% of the hydrocarbon feedstock may have a boiling point of less than or equal to 570° C. In embodiments, at least 90% of the hydrocarbon feedstock may have a boiling point from 270° C. to 570° C., from 340° C. to 570° C., or from 370° C. to 570° C.

In one or more embodiments, contacting the hydrocarbon feedstock with the modified zeolite occurs at a temperature from 100° C. to 450° C. For example without limitation, contacting the hydrocarbon feedstock with the modified zeolite may occur at a temperature from 100° C. to 450° C., from 120° C. to 450° C., from 140° C. to 450° C., from 160° C. to 450° C., from 180° C. to 450° C., from 200° C. to 450° C., from 220° C. to 450° C., from 240° C. to 450° C., from 260° C. to 450° C., from 280° C. to 450° C., from 300° C. to 450° C., from 320° C. to 450° C., from 340° C. to 450° C., from 360° C. to 450° C., from 380° C. to 450° C., from 400° C. to 450° C., from 420° C. to 450° C., from 440° C. to 450° C., from 100° C. to 440° C., from 100° C. to 420° C., from 100° C. to 400° C., from 100° C. to 380° C., from 100° C. to 360° C., from 100° C. to 340° C., from 100° C. to 320° C., from 100° C. to 300° C., from 100° C. to 280° C., from 100° C. to 240° C., from 100° C. to 220° C., from 100° C. to 200° C., from 100° C. to 180° C., from 100° C. to 160° C., from 100° C. to 140° C., from 100° C. to 120° C., or any range or combination of ranges formed from these endpoints.

In one or more embodiments, contacting the hydrocarbon feedstock with the modified zeolite may occur under a partial pressure of hydrogen from 0.5 mbar to 1.5 mbar. For example, without limitation the partial pressure of hydrogen may be from 0.5 mbar to 1.5 mbar, from 0.7 mbar to 1.5 mbar, from 0.9 mbar to 1.5 mbar, from 1.1 mbar to 1.5 mbar, from 1.3 mbar to 1.5 mbar, from 0.5 mbar to 1.3 mbar, from 0.5 mbar to 1.1 mbar, from 0.5 mbar to 0.9 mbar, from 0.5 mbar to 0.7 mbar, or any range or combination of ranges formed from these endpoints. In one or more embodiments, contacting the hydrocarbon feedstock with the modified zeolite may occur at or near atmospheric pressure.

In one or more embodiments, the hydrocarbon feedstock and the modified zeolite may be contacted in a reactor having a liquid hour space velocity (LHSV) from 0.02 hr⁻¹ to 10 hr⁻¹. For example, hydrocarbon feedstock and the modified zeolite may be contacted in a reactor having a LHSV from 0.02 hr⁻¹ to 10 hr⁻¹, from 0.05 hr⁻¹ to 10 hr⁻¹, from 0.1 hr⁻¹ to 10 hr⁻¹, from 0.5 hr⁻¹ to 10 hr⁻¹, from 1 hr⁻¹ to 10 hr⁻¹, from 2 hr⁻¹ to 10 hr⁻¹, from 3 hr⁻¹ to 10 hr⁻¹, from 4 hr⁻¹ to 10 hr⁻¹, from 5 hr⁻¹ to 10 hr⁻¹, from 6 hr⁻¹ to 10 hr⁻¹, from 7 hr⁻¹ to 10 hr⁻¹, from 8 hr⁻¹ to 10 hr⁻¹, from 9 hr⁻¹ to 10 hr⁻¹, from 0.02 hr⁻¹ to 9 hr⁻¹, from 0.02 hr⁻¹ to 8 hr⁻¹, from 0.02 hr⁻¹ to 7 hr⁻¹, from 0.02 hr⁻¹ to 6 hr⁻¹, from 0.02 hr⁻¹ to 5 hr⁻¹, from 0.02 hr⁻¹ to 4 hr⁻¹, from 0.02 hr⁻¹ to 3 hr⁻¹, from 0.02 hr⁻¹ to 2 hr⁻¹, from 0.02 hr⁻¹ to 1 hr⁻¹, from 0.02 hr⁻¹ to 0.5 hr⁻¹, from 0.02 hr⁻¹ to 0.1 hr⁻¹, from 0.02 hr⁻¹ to 0.05 hr⁻¹, or any range or combination of ranges formed from these endpoints.

According to embodiments described herein, contacting the hydrocarbon feedstock with the modified zeolite in the presence of hydrogen may form an intermediate cracked product. The intermediate cracked product may comprise one or more linear alkanes. In one or more embodiments, the intermediate cracked product may comprise at least 30 wt. % linear alkanes. For example, without limitation, the intermediate cracked product may comprise at least 30 wt. %, at least 35 wt. %, at least 40 wt. %, at least 45 wt. %, at least 50 wt. %, at least 55 wt. %, at least 60 wt. %, at least 65 wt. %, at least 70 wt. %, at least 75 wt. %, at least 80 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. % linear alkanes. In some embodiments, the intermediate cracked product may comprise C₄ to C₂₀ linear alkanes. In one or more embodiments, the intermediate cracked product may comprise at least 30 wt. % C₄ to C₂₀ linear alkanes. Without intending to be bound by theory, when the intermediate cracked product comprises at least 30 wt. % linear alkanes, the intermediate cracked product may be used as a feedstock for a steam cracking process without having to undergo reverse isomerization prior to steam cracking.

The methods for processing hydrocarbon feedstocks described herein may comprise steam cracking at least a portion of the intermediate cracked product to form a steam cracked product. The steam cracking may be achieved by any suitable steam cracking process. In one or more embodiments, the steam cracked product may comprise one or more olefins. For example, the steam cracked product may comprise ethylene. In one or more embodiments, the steam cracked product may comprise from 20 wt. % to 75 wt. % ethylene. For example, the steam cracked product may comprise ethylene from 20 wt. % to 75 wt. %, from 30 wt. % to 75 wt. %, from 40 wt. % to 75 wt. %, from 50 wt. % to 75 wt. %, from 60 wt. % to 75 wt. %, from 70 wt. % to 75 wt. %, from 20 wt. % to 65 wt. %, from 20 wt. % to 55 wt. %, from 20 wt. % to 45 wt. %, from 20 wt. % to 35 wt. %, from 20 wt. % to 25 wt. %, or any range or combination of ranges formed from these endpoints.

In one or more embodiments, the at least a portion of the intermediate cracked product may be steam cracked without undergoing any intermediate process steps or reactions to change its composition. For example, the intermediate cracked product may be steam cracked without first undergoing reverse isomerization. In one or more embodiments, the entirety of the intermediate cracked product may be steam cracked. In some embodiments, the entirety of the intermediate cracked product may be steam cracked without undergoing any intermediate process steps or reactions.

The modified zeolites used in the methods for processing hydrocarbon feedstocks are now described in detail. As referred to herein, “modified zeolites” refer to zeolites that include metal atoms bonded to four bridging oxygen atoms, where each of the bridging oxygen atoms bonded to the metal atoms bridges one of the metal atoms and a silicon atom of the framework structure of the zeolite, which are now described in greater detail.

In one or more embodiments, the metal atoms may be Group 4-6 metal atoms. As described herein, “Group 4-6 metal atoms” refer to those elements under International Union of Pure and Applied Chemistry (IUPAC) nomenclature. Group 4 metal atoms include titanium atoms, zirconium atoms, hafnium atoms, and rutherfordium atoms. Group 5 metal atoms include vanadium atoms, niobium atoms, tantalum atoms, and dubnium atoms. Group 6 metal atoms include chromium atoms, molybdenum atoms, tungsten atoms, and seaborgium atoms. In one or more embodiments, the metal atoms may be titanium atoms, hafnium atoms, zirconium atoms or a combination of these. In some embodiments, the metal atoms may comprise titanium atoms.

According to embodiments disclosed herein, the modified zeolites may be formed by a process that includes dehydroxylating an initial zeolite that comprises mesopores ordered with cubic symmetry, grafting organometallic chemicals to the dehydroxylated zeolite, reacting the organometallic chemicals with hydrogen to form a zeolite comprising metal hydride moieties and mesopores ordered with cubic symmetry, and reacting the zeolite comprising metal hydride moieties to form a modified zeolite comprising a plurality of Group 4-6 metal atoms bonded to four bridging oxygen atoms and mesopores ordered with cubic symmetry. While embodiments of modified zeolites prepared by this procedure are disclosed herein, embodiments of the present disclosure should not be considered to be limited to modified zeolites made by such a process. Embodiments, of zeolites modified with titanium atoms bonded to four bridging oxygen atoms are depicted in Chemical Structure #1.

Without intending to be bound by theory, the modified zeolites comprising mesopores ordered with cubic symmetry and comprising a plurality of Group 4-6 metal atoms bonded to four bridging oxygen atoms may have enhanced functionality as catalysts used for cracking reactions. According to one or more embodiments described herein, the modified zeolites comprising mesopores ordered with cubic symmetry and comprising a plurality of metal atoms bonded to four bridging oxygen atoms may have an improved selectivity for linear alkanes when used as a cracking catalyst. Without intending to be bound by theory, modified zeolites described herein may have a low total acidity, which may contribute to the selectivity of the modified zeolite for linear alkanes. If the modified zeolite were more acidic, then linear alkanes may isomerize to produce branched alkanes, which are a less desirable feedstock for steam cracking reactions.

As presently described, “initial” zeolites may be supplied or produced, as is presently disclosed. According to one or more embodiments described herein, initial zeolites comprise a plurality of mesopores that are ordered with cubic symmetry. As described herein, the characterization of the structure and material of the zeolite may equally apply to the initial zeolite as well as the dehydroxylated zeolite and/or modified zeolite. In one or more embodiments, the structure and material composition of the initial zeolite does not substantially change through the dehydroxylation steps, organometallic grafting steps, metal hydride moiety formation steps, and/or metal moiety formation steps (aside from the introduction of the described functionalities formed by the dehydroxylation, organometallic moiety grafting, metal hydride moiety formation steps, and metal moiety formation steps). For example, the framework type and general material constituents of the framework may be substantially the same in the initial zeolite and the modified zeolite aside from the addition of the metal atoms bonded to bridging oxygen atoms. Likewise, mesoporosity of the initial zeolite may be carried into the modified zeolite. Accordingly, when a “zeolite” is described herein with respect to its structural characterization, the description may refer to the initial zeolite, the dehydroxylated zeolite, and/or the modified zeolite.

As used throughout this disclosure, “zeolites” may refer to micropore-containing inorganic materials with regular intra-crystalline cavities and channels of molecular dimension. Zeolites generally comprise a crystalline structure, as opposed to an amorphous structure such as what may be observed in some porous materials such as amorphous silica. Zeolites generally include a microporous framework that may be identified by a framework type. The microporous structure of zeolites (e.g., 0.3 nm to 2 nm pore size) may render large surface areas and desirable size-/shape-selectivity, which may be advantageous for catalysis. The zeolites described may include, for example, aluminosilicates, titanosilicates, or pure silicates. In embodiments, the zeolites described may include micropores (present in the microstructure of a zeolite), and additionally include mesopores. As used throughout this disclosure, micropores refer to pores in a structure that have a diameter of less than or equal to 2 nm and greater than or equal to 0.1 nm, and mesopores refer to pores in a structure that have a diameter of greater than 2 nm and less than or equal to 50 nm. Unless otherwise described herein, the “pore size” of a material refers to the average pore size, but materials may additionally include mesopores having a particular size that is not identical to the average pore size and thus contain a distribution of pores.

Generally, zeolites may be characterized by a framework type, which defines their microporous structure. The zeolites described presently, in one or more embodiments, are not particularly limited by framework type. Framework types are described in, for example, “Atlas of Zeolite Framework Types” by Ch. Baerlocher et al., Fifth Revised Edition, 2001, which is incorporated by reference herein.

According to one or more embodiments, the zeolites described herein may include at least silicon atoms and oxygen atoms. In some embodiments, the microporous framework may include substantially only silicon and oxygen atoms (e.g., silica material). However, in additional embodiments, the zeolites may include other atoms, such as aluminum. Such zeolites may be aluminosilicate zeolites. In one or more embodiments, the microporous framework may consist of silica and alumina. In additional embodiments, the microporous framework may include titanium atoms, and such zeolites may be titanosilicate zeolites. In one or more embodiments, the microporous framework may be substantially free from titanium atoms. It should be understood that, as described herein, not all titanium atoms of the zeolite are necessarily included in the plurality of titanium atoms that are each bonded to four bridging oxygen atoms. For example, contemplated herein are zeolites that comprise titanium atoms in the microstructure of the zeolite as well as a plurality of titanium atoms that are each bonded to four bridging oxygen atoms, as described herein.

In one or more embodiments, the zeolite may comprise an aluminosilicate microstructure. The zeolite may comprise at least 99 wt. % of the combination of silicon atoms, oxygen atoms, and aluminum atoms. The molar ratio of Si/Al may be from 1.5 to 10,000. For example, without limitation, the molar ratio of Si/Al may be from 1.5 to 10,000, from 1.5 to 5,000, from 1.5 to 2,000, from 1.5 to 1,000, from 1.5 to 800, from 1.5 to 600, from 1.5 to 400, from 1.5 to 200, from 1.5 to 100, from 5 to 10,000, from 5 to 5,000, from 5 to 2,000, from 5 to 1,000, from 5 to 800, from 5 to 600, from 5 to 400, from 5 to 200, from 5 to 100, 10 to 10,000, from 10 to 5,000, from 10 to 2,000, from 10 to 1,000, from 10 to 800, from 10 to 600, from 10 to 400, from 10 to 200, from 10 to 100, 50 to 10,000, from 50 to 5,000, from 50 to 2,000, from 50 to 1,000, from 50 to 800, from 50 to 600, from 50 to 400, from 50 to 200, or from 50 to 100, or any combination of these ranges.

In embodiments, the zeolites may comprise microstructures (which include micropores) characterized by, among others as *BEA framework type zeolites (such as, but not limited to, zeolite Beta), FAU framework type zeolites (such as, but not limited to, zeolite Y or ultra-stable zeolite Y), MOR framework type zeolites, MFI framework type zeolite (such as, but not limited to, ZSM-5 or Silicalite-1), CHA framework type zeolite (such as, but not limited to chabazite zeolite), LTL framework type zeolite (such as but not limited to zeolite L), LTA framework zeolite (such as but not limited to zeolite A), AEI framework type zeolite, or MWW framework type zeolite (such as but not limited to MCM-22). It should be understood that *BEA, MFJ, MOR, FAU, CHA, LTL, LTA, AEI, and MWW refer to zeolite framework types as identified by their respective three letter codes established by the International Zeolite Association (IZA). Other framework types are contemplated in the presently disclosed embodiments.

In one or more embodiments, the zeolite may comprise an FAU framework type zeolite, such as zeolite Y or ultra-stable zeolite Y (USY). As used herein, “zeolite Y” and “USY” refer to a zeolite having a FAU framework type according to the IZA zeolite nomenclature and consisting majorly of silica and alumina, as would be understood by one skilled in the art. In one or more embodiments, USY may be prepared from zeolite Y by steaming zeolite Y at temperatures above 500° C. The molar ratio of silica to alumina may be at least 3. For example, the molar ratio of silica to alumina in the zeolite Y may be at least 5, at least 12, at least 30, or even at least 200, such as from 5 to 200, from 12 to 200, or from about 15 to about 200. The unit cell size of the zeolite Y may be from about 24 Angstrom to about 25 Angstrom, such as 24.56 Angstrom.

Along with micropores, which may generally define the framework type of the zeolite, the zeolites may also comprise mesopores. As used herein, a “mesoporous zeolite” refers to a zeolite that includes mesopores, and may have an average mesopore pore size of from 2 to 50 nm. The presently disclosed mesoporous zeolites may have an average mesopore pore size of greater than 2 nm, such as from 4 nm to 16 nm, from 6 nm to 14 nm, from 8 nm to 12 nm, or from 9 nm to 11 nm. In some embodiments, the majority of the mesopores may be greater than 8 nm, greater than 9 nm, or even greater than 10 nm. The mesopores of the mesoporous zeolites described may range from 2 nm to 40 nm, and the median pore size may be from 4 to 12 nm. The mesoporous zeolites described may be generally silica-containing materials, such as aluminosilicates, pure silicates, or titanosilicates.

The mesoporous zeolites described in the present disclosure may have enhanced catalytic activity as compared to non-mesoporous zeolites. Without being bound by theory, it is believed that the microporous structures provide for the majority of the catalytic functionality of the mesoporous zeolites described. The mesoporosity may additionally allow for greater catalytic functionality because more micropores are available for contact with the reactant in a catalytic reaction. The mesopores generally allow for better access to microporous catalytic sites on the mesoporous zeolite, especially when reactant molecules are relatively large. For example, larger molecules may be able to diffuse into the mesopores to contact additional catalytic microporous sites.

Additionally, mesoporosity may allow for additional grafting sites on the zeolite where metal atoms may be bound. As is described herein, organometallic chemicals may be grafted to the microstructure of the zeolite and subsequently treated to form metal atoms bonded to bridging oxygen atoms. Mesoporosity may allow for additional grafting sites, allowing for greater amounts of metal functionalities as compared with non-mesoporous zeolites.

In one or more embodiments, the mesoporous zeolites may have a surface area of from 200 m²/g to 1500 m²/g, from 400 m²/g to 1500 m²/g, from 600 m²/g to 1500, from 800 m²/g to 1500 m²/g, from 1000 m²/g to 1500, from 1200 m²/g to 1500 m²/g, from 1400 m²/g to 1500 m²/g, from 200 m²/g to 1300 m²/g, from 200 m²/g to 1100 m²/g, from 200 m²/g to 900 m²/g, from 200 m²/g to 700 m²/g, from 200 m²/g to 500 m²/g, from 200 m²/g to 300 m²/g or any combination of ranges formed from these endpoints. In one or more other embodiments, the mesoporous zeolites may have pore volume from 0.01 cm³/g to 1.5 cm³/g, 0.05 cm³/g to 1.5 cm³/g, from 0.1 cm³/g to 1.5 cm³/g, from 0.3 cm³/g to 1.5 cm³/g, from 0.5 cm³/g to 1.5 cm³/g, from 0.7 cm³/g to 1.5 cm³/g, from 0.9 cm³/g to 1.5 cm³/g, from 1.1 cm³/g to 1.5 cm³/g, from 1.3 cm³/g to 1.5 cm³/g, 0.01 cm³/g to 1.4 cm³/g, 0.01 cm³/g to 1.2 cm³/g, 0.01 cm³/g to 1.0 cm³/g, 0.01 cm³/g to 0.8 cm³/g, 0.01 cm³/g to 0.6 cm³/g, 0.01 cm³/g to 0.4 cm³/g, 0.01 cm³/g to 0.2 cm³/g, 0.01 cm³/g to 0.1 cm³/g, 0.01 cm³/g to 0.05 cm³/g, or any combination of ranges formed from these endpoints. In further embodiments, the portion of the surface area contributed by mesopores may be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, or even greater than or equal to 65%, such as between 20% and 70% of total surface area. In additional embodiments, the portion of the pore volume contributed by mesopores may be greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, or even greater than or equal to 75%, such as between 20% and 80% of total pore volume. Without intending to be bound by theory, when mesopores dominate the overall porosity of the modified zeolite as a percentage of the total porosity, it may be easier for large reactant molecules to diffuse into the modified zeolite and react. Surface area, average pore size, and pore volume distribution may be measured by N₂ adsorption isotherms performed at 77 Kelvin (K) (such as with a Micrometrics ASAP 2020 system). As would be understood by those skilled in the art, Brunauer-Emmett-Teller (BET) analysis methods may be utilized.

In one or more embodiments, mesoporous zeolites comprise a plurality of mesopores that are ordered with cubic symmetry. In one or more embodiments, the mesopores may be ordered with cubic symmetry having an Ia-3d, Fm-3m, Pm-3n, Pn-3m or Im-3m space group. As described herein, space groups describe combinations of the 32 crystallographic point groups with the 14 Bravais Lattices taking into account symmetries of reflection, rotation and improper rotation, screw axis symmetry, and glide plane symmetry. There are 230 space groups describing possible symmetries. In one or more embodiments, the mesoporous zeolite may comprise mesopores ordered with cubic symmetry having an Ia-3d space group. In one or more embodiments, the mesoporous zeolite may comprise mesopores ordered with cubic symmetry having a Fm-3m space group. Without intending to be bound by theory, the mesopores ordered with cubic symmetry may allow for improved diffusion of reactants to the active sites (e.g., the hafnium hydride moieties) of the modified zeolite and improved diffusion of products away from the active sites. The cubic ordering of the mesopores may result in mesopores being interconnected throughout the modified zeolite in an interconnected, ordered mesoporous system. Interconnected mesopores may make it easier for large reactant molecules to diffuse into the modified zeolite and react. Additionally, cubic ordering of mesopores may impart size and shape selectivity for reactants and products to the modified zeolite because molecules of different sizes and shapes may have different efficiencies for diffusing through the cubic ordered mesopores of the modified zeolite. Furthermore, the inclusion of mesopores ordered with cubic symmetry may provide additional accessibility for organometallic moieties to graft to the zeolite at a greater loading.

The presence of mesopores ordered with cubic symmetry in a mesoporous zeolite may be determined by the presence of secondary peaks in a low angle X-ray diffraction (XRD) pattern and/or by observing the cubic symmetry by microscopy. Cubic symmetry of the mesopores may be identified by transmission electron microscopy (TEM) using selected area electron diffraction (SAED) patterns and fast Fourier transform (FFT) patterns. Additionally, mesopore symmetry may be observed by analyzing the mesopore arrangement from multiple orientations, as various types of mesopore symmetry may have distinctive pore-arrangement patterns in one or multiple orientations. In one or more embodiments, mesopores ordered with cubic symmetry having an Ia-3d space group may also be observable by microscopy viewing an electron beam down a [311], [111], or [110] zone axis. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having an Fm-3m space group may be observable by microscopy viewing an electron beam down a [001] or [110] zone axis.

Without intending to be bound by theory, XRD peaks for each cubic symmetry are distinctive with respect to the two theta values, peak patterns, and peak intensities; however, in the case of broad XRD patterns with overlapped peaks, additional characterization techniques may also be used to confirm the symmetry. Ordered cubic mesoporosity may be identified from Bragg's reflections observed in the low-angle XRD region. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having an Ia-3d space group may exhibit peaks in an XRD spectrum at one or more of the (220), (321), (400), (420), or (322) reflections. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having a Fm-3m space group may exhibit peaks in an XRD spectrum at one or more of the (111), (220), (311), (331), or (442) reflections. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having a Pm-3n space group may exhibit peaks in an XRD spectrum at one or more of the (200), (210), (211), (300), (310), (411), or (331) reflections. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having a Pn-3m space group may exhibit peaks in an XRD spectrum at one or more of the (110), (111), (200), (211), (220), or (221) reflections. In one or more embodiments, a mesoporous zeolite comprising mesopores ordered with cubic symmetry having an Im-3m space group may exhibit peaks in an XRD spectrum at one or more of the (110), (200), (211), or (220) reflections.

According to one or more embodiments, the mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry may be produced as described herein. The mesoporous zeolites may be synthesized using base-mediated reassembly, which include dissolution of the zeolite and reassembly of the zeolite in the presence of a supramolecular template to produce a mesoporous zeolite comprising a plurality of mesopores ordered with cubic symmetry.

In one or more embodiments, the rate and extent of the zeolite dissolution may be controlled by employing urea as an in situ base, and by mediating hydrothermal temperature to control urea hydrolysis and by tuning the pH of the solution. The extent of dissolution of the zeolite may be controlled by interactions between the zeolite and supramolecular templating agent during the initial stages of dissolution, where influence of ion-specific interactions (the anionic Hofmeister effect) on supramolecular self-assembly directs formation of mesopores with cubic symmetry.

In one or more embodiments, a zeolite is included in an aqueous suspension with an alkaline reagent and a supramolecular templating agent. The aqueous suspension may include an ionic co-solute as an additional anion that is separate from the anion that is paired with the cation of the supramolecular templating agent. The system may be maintained under conditions to induce incision of the zeolite into oligomeric units of the zeolite, with only a minor portion of monomeric units, and to induce reassembly of the oligomeric units into mesostructures. System conditions, including temperature and time of crystallization, selection and concentration of the supramolecular template, and selection and concentration of the alkaline reagent are tailored to control incision of the zeolite into oligomeric units and to control reassembly of those oligomeric units around the shapes of supramolecular template micelles. Dissolution of the zeolite may be encouraged to the extent of oligomer formation while minimizing monomer formation, which is controlled by selection of supramolecular template, alkaline reagent, optional ionic co-solute and hydrothermal conditions (temperature and time). In one or more embodiments, at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, or even at least 95 wt. % of the zeolite is cleaved into oligomeric units. In embodiments, a remaining portion of the zeolite may be in the form of monomeric units or even atomic constituents of the zeolite. In one or more embodiments, interface curvature of the micelles of the supramolecular template and the oligomeric units under reassembly may be tuned to a desired mesostructured and mesporosity with the aid of the ionic co-solute and the Hofmeister effect.

Under effective crystallization conditions and time, and using effective types of supramolecular template and alkaline reagent at effective relative concentrations, the zeolite may be incised into oligomeric units that rearrange around the shaped micelles formed by the supramolecular templates to form mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry.

According to one or more embodiments, the curvature or shape of the micelles may result in the cubic symmetry of the mesopores of the mesoporous zeolite. Formation of the supramolecular template molecules into micelles is dependent upon factors such as the supramolecular template type, supramolecular template concentration, the presence or absence of an ionic co-solute, the zeolite material, the crystallization temperature, the type of alkaline reagent, the concentration of the alkaline reagent, the pH of the system, and/or the presence or absence of other reagents. In general, at concentrations less than a threshold micelle concentration, supramolecular templates exist as discrete entities. At concentrations greater than the threshold micelle concentration, micelles of the supramolecular template form. The hydrophobic interactions in the system including the supramolecular template alters the packing shape of the supramolecular templates into, for example, spherical, prolate, or cylindrical micelles, which can thereafter form thermodynamically stable two-dimensional or three-dimensional liquid crystalline phases of ordered mesostructures.

In one or more embodiments, the Hofmeister series, ion specific effect, or lyotropic sequence is followed for selection of supramolecular templates and ionic co-solute to control curvature or shape (e.g., spherical, ellipsoid, cylindrical, or unilamellar structures) of the micelles. In embodiments, distinct mesostructures are formed based on the anionic Hofmeister effect and supramolecular self-assembly. Anions of different sizes and charges possess different polarizabilities, charge densities, and hydration energies in aqueous solutions. When paired with a positive supramolecular template head group, these properties can affect the short-range electrostatic repulsions among the head groups and hydration at the micellar interface, thus changing the area of the head group. Such ion-specific interactions can be a driving force in changing the micellar curveature and inducing the mesophase transition. Based on the Hoffmeister series (SO₄²⁻>HPO₄²⁻>OAc⁻>Cl⁻>Br⁻>NO₃⁻>ClO₄⁻>SCN⁻), strongly hydrated ions can increase the micellar curvature, whereas weakly hydrated ions can decrease the micellar curvature. A surfactant packing parameter can be used to describe the mesophase transitions. The surfactant packing parameter is give in Equation 1:

$\begin{array}{cc}g=\frac{V}{a_{0}l}& \mathrm{Equation}1\end{array}$

In Equation 1, g is the surfactant packing parameter, V is the total volume of surfactant tails, a₀ is the area of the head group, and l is the length of the surfactant tail.

In one or more embodiments, suitable alkaline reagents include one or more basic compounds to maintain the system at a pH level of greater than about 8. In one or more embodiments, the alkaline reagent is provided at a concentration in the aqueous suspension of about 0.1 M to about 2.0 M. In one or more embodiments, the alkaline reagent is provided at a concentration in the aqueous suspension of about 0.1 wt. % to 5 wt. %. The alkaline reagent may comprise urea, ammonia, ammonium hydroxide, sodium hydroxide, or combinations of these. In one or more embodiments, the alkaline reagent comprises alkali metal hydroxides including hydroxides of sodium, lithium, potassium, rubidium, or cesium.

In one or more embodiments, the alkaline reagent is effective to enable controlled hydrolysis; for example, urea can be used as an alkaline agent, and during hydrolysis urea reacts to form ammonium hydroxide. For example, higher urea concentration can be used in an initial step and basicity may be maintained by gradual urea hydrolysis. In such embodiments, pH is increased relatively slowly to a maximum pH as a function of time, which is beneficial to the process, rather than adding an amount of another alkaline reagent such as ammonium hydroxide in the initial solution to the maximum pH. Unlike conventional bases, which act swiftly, urea is pH neutral at ambient conditions and can disperse uniformly throughout the zeolitic micropores without affecting them.

In one or more embodiments, the alkaline reagent comprises alkylammonium cations, having the general formula R_xH_4-xN+[A−], wherein at X=1 to 4 and R₁, R₂, R₃ and R₄ can be the same or different C1-C30 alkyl groups, and wherein [A-] is a counter anion can be OH⁻, Br⁻, Cl⁻, or I⁻. In one or more embodiments, the alkaline reagent comprises quaternary ammonium cations with alkoxysilyl groups, phosphonium groups, an alkyl group with a bulkier substituent or an alkoxyl group with a bulkier substituent. In one or more embodiments, the alkylammonium cations used in this regard function as a base rather than as a surfactant or template.

In one or more embodiments, suitable surfactants as supramolecular templates are provided to assist the reassembly and recrystallization of dissolved components (oligomers) by covalent and/or electrovalent interactions. Supramolecular templates may be included in the aqueous suspension in a concentration of about 0.01 M to 0.5 M. In one or more embodiments, suitable supramolecular templates are provided at a concentration in the aqueous suspension of about 0.5 wt. % to 10 wt. %. Suitable supramolecular templates may be characterized by constrained diffusion within the micropore channels of zeolite. Diffusion of supramolecular template molecules into micropore channels or cavities encourages dissolution of the zeolite. This is minimized in the top-down methods for synthesis of the mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry described herein, wherein effective supramolecular templates minimize diffusion or partial diffusion thereof into zeolite pore-channels, cavities or window openings. Such supramolecular templates may possess suitable dimensions to block such diffusion. The suitable dimensions can be a based on dimensions of a head group and/or a tail group of a supramolecular template. In certain embodiments suitable dimensions can be based on a co-template having one or more components with suitable head and/or tail groups, or being a template system arranged in such a way, as to minimize or block diffusion into zeolite pore-channels, cavities, or window openings. By minimizing diffusion of templates into the zeolite pore channels, zeolite dissolution into oligomers and comprehensive reorganization and assembly into the mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry disclosed herein is encouraged. In certain embodiments, a supramolecular template is one in which at least a portion of the surfactant does not enter into pores and/or channels of the zeolite. For example, organosilanes (˜0.7 nm) are relatively large compared to quaternary ammonium surfactants without such bulky groups including cetyltrimethylammonium bromide (CTAB) (˜0.25 nm). In one or more embodiments, a supramolecular template contains a long chain linear group (>˜0.6 nm). In one or more embodiments, a supramolecular template contains an aromatic or aromatic derivative group (>˜0.6 nm). In one or more embodiments, supramolecular templates contain one or more bulky groups having a dimension based on modeling of molecular dimensions as a cuboid having dimensions A, B and C, using Van der Waals radii for individual atoms, wherein one or more, two or more, or all three of the dimensions A, B and C are sufficiently close in dimension, or sufficiently larger in dimension, that constrains diffusion into the micropores of the zeolite.

In one or more embodiments, an effective surfactant as a supramolecular template contains at least one moiety, as a head group or a tail group, selected from organosilanes, hydroxysilyls, alkoxysilyls, aromatics, branched alkyls, sulfonates, carboxylates, phosphates and combinations of these moieties. In one or more additional embodiments, an effective supramolecular template is an organosilane that comprises at least one hydroxysilyl as a head group moiety. In one or more embodiments, an effective supramolecular template is an organosilane that comprises at least one hydroxysilyl as a tail group moiety. In one or more further embodiments, an effective supramolecular template is an organosilane that comprises at least one alkoxysilyl as a head group moiety. In one or more embodiments, an effective supramolecular template is an organosilane that comprises at least one alkoxysilyl as a tail group moiety. In one or more additional embodiments, an effective supramolecular template comprises at least one aromatic as a head group moiety. In one or more further embodiments, an effective supramolecular template comprises at least one aromatic as a tail group moiety. In one or more additional embodiments, an effective supramolecular template comprises at least one branched alkyl as a head group moiety. In one or more embodiments, an effective supramolecular template comprises at least one branched alkyl as a tail group moiety. In one or more embodiments, an effective supramolecular template comprises at least one sulfonate as a head group moiety. In one or more further embodiments, an effective supramolecular template comprises at least one sulfonate as a tail group moiety. In one or more additional embodiments, an effective supramolecular template comprises at least one carboxylate as a head group moiety. In one or more embodiments, an effective supramolecular template comprises at least one carboxylate as a tail group moiety. In one or more embodiments, an effective supramolecular template comprises at least one phosphate as a head group moiety. In one or more additional embodiments, an effective supramolecular template comprises at least one phosphate as a tail group moiety. These moieties are characterized by one or more dimensions that constrain diffusion into pores of a zeolite. In certain embodiments, in which the zeolite is characterized by pores of various dimensions, the selected moieties are characterized by one or more dimensions that constrain diffusion into the largest pores the zeolite.

In one or more embodiments, an effective supramolecular template comprises at least one cationic moiety. In one or more further embodiments, an effective supramolecular template comprises at least one cationic moiety selected from a quaternary ammonium moiety and a phosphonium moiety. In one or more additional embodiments, an effective supramolecular template comprises at least one quaternary ammonium group having a terminal alkyl group with 6 to 24 carbon atoms. In one or more embodiments, an effective supramolecular template comprises two quaternary ammonium groups wherein an alkyl group bridging the quaternary ammonium groups contains 1 to 10 carbon atoms. In one or more additional embodiments, an effective supramolecular template comprises at least one quaternary ammonium group, and at least one constituent group, a head group moiety as described above. In one or more further embodiments, an effective supramolecular template comprises at least one quaternary ammonium group, and at least one constituent group, a tail group moiety as described above. In one or more embodiments, an effective supramolecular template contains at least one quaternary ammonium group, at least one constituent group, a head group moiety as described above, and an alkyl group that contains 1 to 10 carbon atoms bridging at least one of the quaternary ammonium groups and at least one of the head groups. In one or more further embodiments, an effective supramolecular template contains at least one quaternary ammonium group, at least one constituent group, a tail group moiety as described above, and an alkyl group that contains 1 to 10 carbon atoms bridging at least one of the quaternary ammonium groups and at least one of the tail groups.

In one or more embodiments, an effective supramolecular template comprises a quaternary ammonium compound and a constituent group comprising one or more bulky organosilane or alkoxysilyl substituents. In one or more additional embodiments, an effective supramolecular template comprises a quaternary ammonium compound and a constituent group comprising one or more long-chain organosilane or alkoxysilyl substituents. In certain embodiments an effective supramolecular template cation comprises dimethyloctadecyl(3-trimethoxysilyl-propyl)-ammonium or derivatives of dimethyloctadecyl(3-trimethoxysilyl-propyl)-ammonium. In one or more embodiments, an effective supramolecular template cation comprises dimethylhexadecyl(3-trimethoxysilyl-propyl)-ammonium or derivatives of dimethylhexadecyl(3-trimethoxysilyl-propyl)-ammonium. In one or more additional embodiments, an effective supramolecular template cation comprises a double-acyloxy amphiphilic organosilane such as [2,3-bis(dodecanoyloxy)-propyl](3-(trimethoxysilyl)propyl)-dimethylammonium or derivatives of [2,3-bis(dodecanoyloxy)-propyl](3-(trimethoxysilyl)propyl)-dimethylammonium.

In one or more embodiments, an effective supramolecular template comprises a quaternary phosphonium compound and a constituent group comprising one or more bulky aromatic substituents. In one or more embodiments, an effective supramolecular template comprises a quaternary phosphonium compound and a constituent group comprising one or more bulky alkoxysilyl or organosilane substituents.

In one or more embodiments, an effective supramolecular template contains a tail group moiety selected from the group consisting of aromatic groups containing 6 to 50, 6 to 25, 10 to 50 or 10 to 25 carbon atoms, alkyl groups containing 1 to 50, 1 to 25, 5 to 50, 5 to 25, 10 to 50 or 10 to 25 carbon atoms, aryl groups containing 1 to 50, 1 to 25, 5 to 50, 5 to 25, 10 to 50 or 10 to 25 carbon atoms, or a combination of aromatic and alkyl groups having up to 50 carbon atoms. In one or more embodiments, an effective supramolecular template comprises a head group moiety selected from the group consisting of aromatic groups containing 6 to 50, 6 to 25, 10 to 50 or 10 to 25 carbon atoms, alkyl groups containing 1 to 50, 1 to 25, 5 to 50, 5 to 25, 10 to 50 or 10 to 25 carbon atoms, aryl groups containing 1 to 50, 1 to 25, 5 to 50, 5 to 25, 10 to 50 or 10 to 25 carbon atoms, or a combination of aromatic and alkyl groups having up to 50 carbon atoms. In one or more embodiments, an effective supramolecular template contains co-templated agents selected from the group consisting of quaternary ammonium compounds (including for example quaternary alkyl ammonium cationic species) and quaternary phosphonium compounds.

In one or more embodiments, effective supramolecular templates comprise (a) at least one of: aromatic quaternary ammonium compounds, branched alkyl chain quaternary ammonium compounds, alkyl benzene sulfonates, alkyl benzene phosphonates, alkyl benzene carboxylates, or substituted phosphonium cations; and (b1) and a constituent group comprising at least one of organosilanes, hydroxysilyls, alkoxysilyls, aromatics, branched alkyls, sulfonates, carboxylates or phosphates, as a head group; or (b2) and a constituent group comprising at least one of organosilanes, hydroxysilyls, alkoxysilyls, aromatics, branched alkyls, sulfonates, carboxylates or phosphates, as a tail group. In one or more embodiments, effective supramolecular templates include a sulfonate group (a non-limiting example is sulfonated bis(2-hydroxy-5-dodecylphenyl)methane (SBHDM). In one or more further embodiments, effective supramolecular templates include a carboxylate group (a non-limiting example is sodium 4-(octyloxy) benzoate). In one or more additional embodiments, effective supramolecular templates include a phosphonate group (a non-limiting example is tetradecyl(1,4-benzene)bisphosphonate). In one or more embodiments, effective supramolecular templates include an aromatic group (a non-limiting example is benzylcetyldimethylammonium chloride). In one or more additional embodiments, effective supramolecular templates include an aliphatic group (a non-limiting example is tetraoctylammonium chloride).

The supramolecular template is provided as a cation/anion pair. In one or more embodiments, a cation of a supramolecular template is as described above is paired with an anion, such as Cl⁻, Br⁻, OH⁻, P⁻, and I⁻. In one or more further embodiments, a cation of a supramolecular template is as described above is paired with an anion such as Cl⁻, Br⁻, and OH⁻. In one or more embodiments, an effective supramolecular template comprises dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (commonly abbreviated as “TPOAC”) or derivatives of dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride. In one or more additional embodiments, an effective supramolecular template comprises dimethylhexadecyl[3-(trimethoxysilyl)propyl] ammonium chloride or derivatives of dimethylhexadecyl[3-(trimethoxysilyl)propyl] ammonium chloride. In one or more further embodiments an effective supramolecular template comprises [2,3-bis(dodecanoyloxy)-propyl](3-(trimethoxysilyl)propyl)-dimethylammonium iodide or derivatives of [2,3-bis(dodecanoyloxy)-propyl](3-(trimethoxysilyl)propyl)-dimethylammoniumiodide.

In one or more embodiments, the system includes an effective amount of an ionic co-solute (that is, in addition to the anion paired with the supramolecular template). In one or more embodiments in which an ionic co-solute is used, the ionic co-solute is provided at a concentration in the aqueous suspension of about 0.01 M to about 0.5 M. In one or more embodiments in which an ionic co-solute is used, the ionic co-solute is provided at a concentration in the aqueous suspension of about 0.01 wt. % to about 5 wt. %. In one or more embodiments, an ionic co-solute is selected from the group consisting of CO₃²⁻, SO₄²⁻, S₂O₃²⁻, H₂PO₄⁻, F⁻, Cl⁻, Br⁻, NO₃⁻, I⁻, ClO₄⁻, SCN⁻, and C₆H₅O₈³⁻ (citrate). In one or more embodiments, an ionic co-solute is selected based on the Hofmeister series/Lyotropic series to control the curvature/shape of the micelles to yield the desired cubic mesophase symmetry. In one or more embodiments a nitrate (NO₃⁻) is an ionic co-solute selected based on the Hofmeister series/Lyotropic series to control the curvature/shape of the micelles to yield mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry. In one or more embodiments using nitrate as an ionic co-solute, a nitrate salt is used, such as ammonium nitrate or a metal nitrate, wherein the metal can be an alkali metal, an alkali earth metal, a transition metal, a noble metal or a rare earth metal.

According to one or more embodiments described herein, the method of forming mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry comprises base-mediated dissolution/incision of zeolite into oligomeric components, and reorganization of the oligomeric components by supramolecular templating, and in certain embodiments by the Hofmeister effect. The zeolite is provided in crystalline form. An effective amount of an alkaline reagent and an effective amount of a surfactant for supramolecular templating are added to form an aqueous suspension, and that suspension is maintained under hydrothermal conditions to form oligomeric units of the zeolite. The supramolecular template molecules form into shaped micelles and oligomeric zeolite units reassemble and crystallize around the shaped micelles as an ordered mesostructured having mesopores of cubic symmetry and mesopore walls formed of the oligomeric zeolite units, thereby retaining micropores of the underlying zeolite structure. In one or more embodiments, the shaped micelles may be removed, for example by: chemical methods such as solvent extraction, chemical oxidation, or ionic liquid treatment; or physical methods such as calcination, supercritical CO₂, microwave-assisted treatment, ultrasonic assisted treatment, ozone treatment, or plasma technology. Without being bound by theory, it is believed that the removal of the micelles forms at least a portion of the mesopores of the mesoporous zeolite, where the mesopores are present in the space once inhabited by the micelles.

An effective amount of a solvent may be used in the process. In one or more embodiments, the solvent comprises water. In one or more embodiments, the solvent is water in the presence of co-solvents selected from the group consisting of polar solvents, non-polar solvents and pore swelling agents (such as 1,3,5-trimethylbenzene). In one or more embodiments, the solvent selected from the group consisting of polar solvents, non-polar solvents and pore swelling agents (such as 1,3,5-trimethylbenzene), in the absence of water. In an embodiment, mixture components are added with water to the reaction vessel prior to heating. Without intending to be bound by theory, water allows for adequate mixing to realize a more homogeneous distribution of the suspension components, which ultimately produces a more desirable product because each crystal is more closely matched in properties to the next crystal.

According to embodiments, the suspension components may be combined in any suitable sequence and are sufficiently mixed to form a homogeneous distribution of the suspension components. The suspension can be maintained in an autoclave under autogenous pressure (from the components or from the components plus an addition of a gas purge into the vessel prior to heating), or in another suitable vessel, under agitation such as by stirring, tumbling and/or shaking. Mixing of the suspension components is conducted between about 20° C. and about 60° C.

The steps of incision and reassembly may occur during hydrothermal treatment to form a solid product (mesoporous zeolite comprising a plurality of mesopores ordered with cubic symmetry) suspended in a supernatant (mother liquor). Hydrothermal treatment may be conducted: for a period of about 4 hrs. to 168 hrs., 12 hrs. to 168 hrs., 24 hrs. to 168 hrs., 4 hrs. to 96 hrs., 12 hrs. to 96 hrs. or 24 hrs. to 96 hrs.; at a temperature of about 70° C. to 250° C., 70° C. to 210° C., 70° C. to 180° C., 70° C. to 150° C., 90° C. to 250° C., 90° C. to 210° C., 90° C. to 180° C., 90° C. to 150° C., 110° C. to 250° C., 110° C. to 210° C., 110° C. to 180° C., or 110° C. to 150° C.; and at a pressure of about atmospheric to autogenous pressure. In one or more embodiments, hydrothermal treatment occurs in a vessel that is the same as that used for mixing, or the suspension is transferred to another vessel (such as another autoclave or low-pressure vessel). In one or more embodiments, the vessel used for hydrothermal treatment is static. In one or more embodiments, the vessel used for hydrothermal treatment is under agitation that is sufficient to suspend the components.

The solid product, the mesoporous zeolite comprising a plurality of mesopores ordered with cubic symmetry) are recovered using techniques such as centrifugation, decanting, gravity settling, vacuum filtration, filter press, or rotary drums. The recovered solid product is dried, for example at a temperature of about 50° C. to 150° C., at atmospheric pressure or under vacuum conditions, for a time of about 0.5 hrs. to 96 hrs.

In one or more embodiments, the solid product is calcined to remove supramolecular templates that remain in the mesopores and other constituents from the mesopores and/or the discrete zeolite cell micropores. The conditions for calcination, in embodiments in which it is carried out, can include temperatures in the range of about 350° C. to 650° C., 350° C. to 600° C., 350° C. to 550° C., 500° C. to 650° C., 500° C. to 600° C., or 500° C. to 550° C., atmospheric pressure or under vacuum, and a time period of about 2.5 hrs. to 24 hrs., 2.5 hrs. to 12 hrs., 5 hrs. to 24 hrs., or 5 hrs. to 12 hrs. Calcining can occur with ramp rates in the range of from about 0.1 to 10° C. per minute. In one or more embodiments, calcination can have a first step ramping to a temperature of between about 100° C. and 150° C. with a holding time of from about 1 to 12 hours at ramp rates of from about 0.1 to 5° C. per min. before increasing to a higher temperature with a final holding time in the range of about 1 to 12 hours.

According to one or more embodiments disclosed herein, the mesoporous zeolites comprising a plurality of mesopores ordered with cubic symmetry may serve as an “initial zeolite” which is then dehydroxylated, forming a dehydroxylated zeolite. In general, the initial zeolite may refer to a zeolite, which is not substantially dehydroxylated and includes at least a majority of vicinal hydroxyl groups. Dehydroxylation, as is commonly understood by those skilled in art, involves a reaction whereby a water molecule is formed by the release of a hydroxyl group and its combination with a proton. The initial zeolite may primarily comprise vicinal silanol functionalities. In one or more embodiments, dehydroxylating the initial zeolite may form isolated terminal silanol functionalities comprising hydroxyl groups bonded to silicon atoms of the microporous framework of the dehydroxylated zeolite. Such isolated silanol functionalities may be expressed as ≡Si—O—H.

As described herein “silanol functionalities” refer to ≡Si—O—H groups. Silanol groups generally include a silicon atom and a hydroxyl group (—OH). As described herein, “terminal” functionalities refer to those that are bonded to only one other atom. For example, the silanol functionality may be terminal by being bonded to only one other atom such as a silicon atom of the microporous framework. As described herein, “isolated silanol functionalities” refer to silanol functionalities that are sufficiently distant from one another such that hydrogen-bonding interactions are avoided with other silanol functionalities. These isolated silanol functionalities are generally silanol functionalities on the zeolite that are non-adjacent to other silanol functionalities. Generally, in a zeolite that includes silicon and oxygen atoms, “adjacent silanols” are those that are directly bonded through a bridging oxygen atom. Isolated silanol functionalities may be identified by FT-IR and/or ¹H-NMR, as would be understood by those skilled in the art. For example, isolated silanol functionalities may be characterized by a sharp and intense FT-IR band at about 3747 cm⁻¹ and/or a ¹H-NMR shift at about 1.8 ppm. In the embodiments described herein, peaks at or near 3747 cm⁻¹ in FT-IR and/or at or near 1.8 ppm in ¹H-NMR may signify the existence of the dehydroxylated zeolite, and the lack of peaks at or near these values may signify the existence of the initial zeolite.

Isolated silanol functionalities can be contrasted with vicinal silanol functionalities, where two silanol functionalities are “adjacent” one another by each being bonded with a bridging oxygen atom. Chemical Structure #2A depicts an isolated silanol functionality and Chemical Structure #2B depicts a vicinal silanol functionality. Hydrogen bonding occurs between the oxygen atom of one silanol functionality and the hydrogen atom of an adjacent silanol functionality in the vicinal silanol functionality. Vicinal silanol functionality may show a different and broad band in FT-IR and ¹H-NMR, such as 3520 cm⁻¹ or 3720 cm⁻¹ in FT-IR, and 3 ppm in ¹H-NMR.

As described herein, a “dehydroxylated zeolite” refers to a zeolitic material that has been at least partially dehydroxylated (i.e., H and O atoms are liberated from the initial zeolite and water is released). Without being bout by theory, it is believed that the dehydroxylation reaction forms a molecule of water from a hydroxyl group of a first silanol and a hydrogen of a second silanol of a zeolite. The remaining oxygen atom of the second silanol functionality forms a siloxane group in the zeolite (i.e., (≡Si—O—Si≡), sometimes referred to as a strained siloxane bridge. Generally, strained siloxane bridges are those formed in the dehydroxylation reaction and not in the formation of the initial zeolite.

In one or more embodiments, the initial zeolite (as well as the dehydroxylated zeolite) comprises aluminum in addition to silicon and oxygen. For example, ZSM-5 zeolite may include such atoms. In embodiments with aluminum present, the microporous framework of the dehydroxylated zeolite may include Bronsted acid silanol functionalities. In the Bronsted acid silanol functionalities, each oxygen atom of the Bronsted acid silanol functionality may bridge a silicon atom and an aluminum atom of the microporous framework. Such Bronsted acid silanol functionalities may be expressed as [≡Si—O(H)→Al≡].

Chemical Structure #3 depicts an example of an aluminosilicate zeolite framework structure that includes the isolated terminal silanol functionalities and Bronsted acid silanol functionalities described herein.

According to one or more embodiments, the dehydroxylation of the initial zeolite may be performed by heating the initial zeolite at elevated temperatures under vacuum, such as from 700° C. to 1100° C. It is believed that according to one or more embodiments described herein, heating at temperatures below 650° C. may be insufficient to form terminal isolated silanol functionalities. However, heating at temperatures greater than 1100° C. may result in the elimination of terminal isolated silanol functionalities, or the production of such functionalities in low enough concentrations that further processing by contact with organometallic chemicals to form organometallic moieties is not observed, as is described subsequently herein.

According to embodiments, the temperature of heating may be from 650° C. to 700° C., from 700° C. to 750° C., from 750° C. to 800° C., from 800° C. to 850° C., from 850° C. to 900° C., from 900° C. to 950° C., from 950° C. to 1000° C., from 1000° C. to 1050° C., from 1050° C. to 1100° C., or any combination of these ranges. For example, temperature ranges from 650° C. to any named value are contemplated, and temperature ranges from any named value to 1100° C. are contemplated. As described herein, vacuum pressure refers to any pressure less than atmospheric pressure. According to some embodiments, the pressure during the heating process may be less than 10⁻² mbar, less than 10^−2.5 mbar, less than 10⁻³ mbar, less than 10^−3.5 mbar, less than 10⁻⁴ mbar, or even less than 10^−4.5 mbar. The heating times may be sufficiently long such that the zeolite is brought to thermal equilibrium with the oven or other thermal apparatus utilized. For example, heating times of greater than 8 hours, greater than 12 hours, or greater than 18 hours may be utilized. For example, 24 hours of heating time may be utilized.

Without being bound by any particular theory, it is believed that greater heating temperatures during dehydroxylation correlate with reduced terminal silanols present on the dehydroxylated zeolite. However, it is believed that greater heating temperatures during dehydroxylation correlate with greater amounts of strained siloxanes. For example, when the initial zeolite is heated at 700° C. during dehydroxylation, the concentration of isolated terminal silanol groups may be at least 0.4 mmol/g, such as approximately 0.45 mmol/g in some embodiments, as measured by methyl lithium titration. Dehydroxylating at 1100° C. may result in much less isolated terminal silanol and much less isolated Bronsted acid silanol. In some embodiments, less than 10% of the isolated terminal silanol groups present at 700° C. dehydroxylation are present when 1100° C. dehydroxylation heating is used. However, it is believed that strained siloxane groups are appreciably greater at these greater dehydroxylation temperatures.

According to one or more of the embodiments disclosed herein, the dehydroxylated zeolite is reacted with an organometallic chemical. This process may be referred to as the organometallic moiety grafting step. As presently described, an “organometallic chemical” refers to any chemical comprising both metal and organic constituents, as would be understood by one skilled in the art. The organometallic moieties grafted to the zeolitic framework structure comprise a portion of the organometallic chemical. The organometallic chemical, as described herein, can be thought of as a precursor to the grafted organometallic moiety. According to embodiments, the organometallic chemical reacts with the dehydroxylated zeolite to form the organometallic moiety. The reacting of the organometallic chemical with the dehydroxylated zeolite may form an intermediate zeolite comprising organometallic moieties. Each of the organometallic moieties may be bonded to an oxygen atom of the modified zeolite. As presently described, the “organometallic moiety” may be any chemical group comprising a metal atom and some organic constituent. Generally, the metal atom of the organometallic moiety may be bonded to a bridging oxygen atom. The organometallic moieties, as described herein, may be derived from an organometallic chemical that is reacted with the dehydroxylated zeolite.

Chemical Structure #4, shown below, generally depicts one reaction which is contemplated to take place when the dehydroxylated zeolite is contacted by the organometallic chemical. In Chemical Structure #4, MR₁R₂R₃R₄ is representative of an organometallic chemical, where M is a metal atom and R₁, R₂, R₃, and R₄ are ligands bonded to the metal. It should be understood that, depending upon the metal, less than four or greater than four ligands may be present in the organometallic chemical. Still referring to Chemical Structure #4, the organometallic chemical is reacted with the dehydroxylated zeolite and the resulting intermediate zeolite includes the organometallic moiety. The organometallic moiety is generally shown as -MR₂R₃R₄. In the grafting reaction of Chemical Structure #4, the R₁ ligand is bonded with a hydrogen atom of a hydroxyl group of the dehydroxylated zeolite and forms a bi-product depicted in Chemical Structure #4 as R₁—H. As depicted, the intermediate zeolite may include the organometallic moiety each bonded to bridging oxygen atoms. The bridging oxygen atom may bridge the metal atom of the organometallic moiety and a silicon atom of the microporous framework of the intermediate zeolite. As described herein, “bridging” atoms are those which are bonded to at least two other atoms. For example, the bridging oxygen atoms described herein may be bonded with a silicon atom of the microporous framework as well as the metal atom of the organometallic moiety. Bridging atoms may be contrasted with terminal atoms or moieties, which are only bonded to a single other atom. As used herein, “bridging” refers to direct bonding to the two or more other atoms or moieties.

According to one or more of the embodiments disclosed herein, the organometallic moiety grafting step, as depicted in Chemical Structure #4, may take place by liquid impregnation of the organometallic chemical. The organometallic chemical may be in a solution with a dry solvent such as n-pentane. In some embodiments, the impregnation process may be performed at or near room temperature under stirring for several hours, such as from 3 to 10 hours. Following impregnation, the modified zeolite may be washed and dried. Other grafting methods are contemplated besides wet impregnation, and the grafting technique should not be necessarily limiting on the modified zeolite structure or methods of making such. For example, in one or more embodiments, the organometallic moiety grafting step may take place by sublimation of the organometallic compound if the organometallic compound is sufficiently volatile.

Without being bound by theory, it is believed that the organometallic moiety grafting described herein, where organometallic moieties are bonded to bridging oxygen atoms, may take place only when isolated terminal silanol groups are present on the zeolite. Thus, it is believed that methods which do not utilize a dehydroxylation step which promotes the formation of isolated terminal silanol functionalities will not be successful in organometallic moiety grafting as presently disclosed.

In one or more embodiments, substantially all of the isolated terminal silanol groups of the dehydroxylated zeolite may be reacted. For example, if the concentration of isolated terminal silanol groups is at least 0.4 mmol/g, the concentration of organometallic moieties may be at least 0.4 mmol/g. It is also contemplated that, according to some embodiments, not all isolated terminal silanol groups are reacted. According to embodiments, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of isolated terminal silanol groups of the dehydroxylated zeolite are reacted in the organometallic grafting step. According to one or more embodiments, the modified zeolite may comprise at least 0.25 mmol/g, at least 0.3 mmol/g, at least 0.35 mmol/g, at least 0.4 mmol/g, or even at least 0.45 mmol/g of the organometallic moieties.

In one or more embodiments, since the organometallic moiety of the intermediate zeolite is bonded with an oxygen from an isolated terminal silanol group of the dehydroxylated zeolite, dehydroxylation conditions that form relatively greater amounts of isolated terminal silanol groups may be desired. For example, as described herein, temperatures near 700° C. (such as 650° C. to 900° C.) for dehydroxylation may be utilized to form greater amounts of isolated terminal silanol groups. In one or more embodiments, dehydroxylation heating temperatures may be less than or equal to 900° C., less than or equal to 850° C., less than or equal to 800° C., or less than or equal to 750° C.

In some embodiments, the organometallic moieties may grafted to both isolated terminal silanol groups and Bronsted acid silanol groups. Without intending to be bound by theory when the molar ratio of organometallic chemical to isolated terminal silanol groups is 1 to 1 or less, the organometallic moieties will form on the isolated terminal silanol groups; however, if the molar ratio of organometallic chemical to isolated terminal silanol groups is greater than 1 to 1, the organometallic moieties may form on both isolated terminal silanol groups and Bronsted acid silanol groups.

In one or more embodiments, the organometallic moieties may comprise a Group 4-6 metal atom. In one or more embodiments, the organometallic moieties may comprise a metal compound that may have a chemical formula of MR₁R₂R₃, where M is a Group 4-6 metal atom. In one or more embodiments, M may be titanium, hafnium, or zirconium. In some embodiments, M may be titanium. In one or more embodiments, R₁ may be a functional group. For example, R₁ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group. In one or more embodiments, R₂ may be a functional group. For example, R₂ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group. In one or more embodiments, R₃ may be a functional group. For example, R₃ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group.

In one or more embodiments, each of R₁, R₂, and R₃ may be an alkyl group. In one or more embodiments, each of R₁, R₂, and R₃ may be the same alkyl group. In one or more embodiments, R₁, R₂, and R₃ may be a neopentyl group. In one or more embodiments, the organometallic moieties may comprise tris(neopentyl)titanium.

In one or more embodiments, organometallic moieties and organometallic chemicals may comprise one or more functional groups. As described herein, a “parent” atom or molecule refers to the atom or molecule to which a described functional group or other moiety is bonded. In one or more embodiments, the parent atom or molecule may comprise a Group 4-6 metal.

As described herein, an “alkyl group” may be a functional group derived from an alkane. Generally, alkanes may be saturated hydrocarbons that may contain carbon-carbon single bonds. In one or more embodiments, an alkyl group may derive from an alkane comprising one or more carbon atoms. For example, the alkyl group may comprise a methyl, ethyl, propyl, butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, or n-decyl group. In one or more embodiments, the alkyl group may be derived from a branched alkane of at least three carbon atoms. For example, the alkyl group may comprise an isopropyl, isobutyl, tertbutyl, isopentyl, or neopentyl group. In one or more embodiments, alkyl groups may have one or more isomers and, any isomers of an alkyl group may be bound to the parent atom. In one or more embodiments, the alkyl group may comprise a cycloalkane. For example, the alkyl group may comprise a cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, cyclononyl, or cyclodecyl group.

As described herein, a “hydride group” may be a hydrogen atom with a negative formal charge. In one or more embodiments the hydride group may have nucleophilic, reducing, or basic properties.

As described herein, a “hydroxyl group” may be a functional group that may comprise oxygen bonded to hydrogen. In one or more embodiments, a hydroxyl group may have the chemical formula OH. In one or more embodiments, the oxygen atom of the hydroxyl group may be bonded to the parent atom or molecule.

As described herein, an “alkoxy group” may be a functional group with the chemical formula OR, where R comprises an alkyl group. In one or more embodiments, the oxygen atom of the alkoxy group may be bonded to the parent atom or molecule.

As described herein, an “allyl group” may be a functional group comprising a methylene bridge between a vinyl group and the parent atom or molecule. In one or more embodiments, an allyl group may have the chemical formula H₂C═CH—CH₂R, where R is the parent atom or molecule.

As described herein, a “cyclopentadienyl group” may be a functional group comprising an aromatic with the chemical formula [C₅H₅]⁻. In one or more embodiments, one or more of the hydrogen atoms of the cyclopentadienyl group may be replaced by one or more functional groups. For example, the cyclopentadienyl group may be a pentamethyl cyclopentadienyl group or substituted cyclopentadienyl group. In one or more embodiments, the parent atom or molecule may replace one of the hydrogen atoms in the cyclopentadienyl group. In one or more embodiments, the parent atom or molecule may comprise a metal and may form an organometallic complex with the cyclopentadienyl group without replacing one of the hydrogen atoms of the cyclopentadienyl group.

As described herein, an “amino group” may be a functional group comprising a nitrogen atom where the nitrogen atom is bonded to the parent atom or molecule. In one or more embodiments, the amino group may have a chemical formula of NR₁R₂, where R₁ may be an organic functional group or a hydrogen atom and R₂ may be an organic functional group or a hydrogen atom. In one or more embodiments, R₁ and R₂ may be methyl groups. In one or more embodiments, R₁ and R₂ may be hydrogen atoms.

As described herein, an “amido group” may be a functional group having a chemical formula of C(═O)NR₁R₂, where R₁ may be an organic functional group or a hydrogen atom and R₂ may be an organic functional group or a hydrogen atom. In one or more embodiments, R₁ and R₂ may be methyl groups. In one or more embodiments, R₁ and R₂ may be hydrogen atoms. In one or more embodiments, the carbon atom may be bonded to the parent atom or molecule.

As described herein, an “imido group” may be a functional group comprising a nitrogen atom bonded to two acyl groups. As described herein, an “acyl group” may be a functional group comprising an oxygen atom bonded to an alkyl group by a double bond. In one or more embodiments, the nitrogen atom of the imido group may be bonded to the parent atom or molecule. In one or more embodiments, the imido group may be a cyclic functional group.

As described herein, a “nitrido group” may be a functional group comprising a nitrogen atom that may have an oxidation state of −3. In one or more embodiments, the nitrogen atom may be bonded to the parent atom or molecule. In one or more embodiments, the nitrido group may comprise a nitrogen atom bonded only to transition metals.

As described herein, a “carbene group” may be a functional group comprising a carbon atom with two unshared valence electrons. In one or more embodiments, the carbon atom with two unshared valence electrons may be bonded to the parent atom or molecule by a single covalent bond. In one or more embodiments, the carbon atom with two unshared valence electrons may be bonded to the parent atom or molecule by a double covalent bond.

As described herein, a “carbyne group” may be a functional group comprising a carbon atom with three non-bonded electrons. In one or more embodiments, the carbon atom may be bonded to the parent atom or molecule by a single covalent bond.

As described herein, a “halogen group” may be a functional group comprising fluorine, chlorine, bromine, iodine, or astatine. In one or more embodiments, a halogen comprising fluorine, chlorine, bromine, iodine, or astatine may be bonded to the parent atom or molecule.

As described herein, a “benzyl group” may be a functional group comprising a benzene ring attached to a CH₂ group. In one or more embodiments, a benzyl group may have the chemical formula C₆H₅CH₂. In one or more embodiments, one or more of the hydrogen atoms of the benzyl group may be replaced by one or more functional groups. In one or more embodiments, the CH₂ group may be bonded to the parent atom or molecule.

As described herein, a “phenyl group” may comprise a benzene ring. In one or more embodiments, a phenol group may have a chemical formula of C₆H₅. In one or more embodiments, one or more of the hydrogen atoms of the phenyl group may be replaced by one or more functional groups. In one or more embodiments, a carbon atom of the phenyl group may be bonded to the parent atom or molecule.

As described herein, an “oxide group” may be a functional group that may comprise oxygen. In one or more embodiments, the oxide group may have a chemical formula of R═O, where R is the parent atom or molecule.

In one or more embodiments, the organometallic chemical may comprise a Group 4-6 metal atom. In one or more embodiments, the organometallic chemical may comprise a compound that may have a chemical formula of MR₁R₂R₃R₄, where M is a Group 4-6 metal atom. In one or more embodiments, M may be titanium, hafnium, or zirconium. In some embodiments, M may be titanium. In one or more embodiments, R₁ may be a functional group. For example, R₁ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group. In one or more embodiments, R₂ may be a functional group. For example, R₂ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group. In one or more embodiments, R₃ may be a functional group. For example, R₃ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group. In one or more embodiments, R₄ may be a functional group. For example, R₄ may be an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, or an oxide group.

In one or more embodiments, each of R₁, R₂, R₃ and R₄ may be an alkyl group. In one or more embodiments, each of R₁, R₂, R₃ and R₄ may be the same alkyl group. In one or more embodiments, R₁, R₂, R₃ and R₄ may be a neopentyl group. In one or more embodiments, the organometallic chemical may comprise tetrakis(neopentyl)titanium.

In one or more embodiments, the organometallic chemical may be any of the chemical structures disclosed in Chemical Structures #5-#12. For example, in one or more embodiments, the organometallic chemical may comprise alkoxy groups as displayed in Chemical Structures #5-#7 and #9. In yet further embodiments, the organometallic chemical may comprise cyclopentadienyl groups, as displayed in Chemical Structures #8-#10. In one or more embodiments, the organometallic chemical may comprise acetylacetonate groups, as displayed in Chemical Structure #11. Additionally, in one or more embodiments, the organometallic chemical may comprise alkyl groups, as displayed in Chemical Structures #8 and #12.

Additionally, as previously disclosed herein, the modified zeolite, as well as the zeolitic precursors, comprise mesopores ordered with cubic symmetry. The mesopores may allow for grafting of the organometallic chemicals throughout the interior of the intermediate zeolite. In order to access such interior sites, the mesopores may be at least as large as the organometallic chemical. For example, the average pore size of the modified zeolite (dehydroxylated zeolite or initial zeolite) may be at least 0.5 nm, at least 1 nm, at least 2 nm, at least 3 nm, at least 4 nm, at least 5 nm, or even at least 10 nm greater than the size of the organometallic chemical.

According to one or more embodiments disclosed herein, the intermediate zeolite comprising organometallic moieties may be reacted with hydrogen to form a second intermediate zeolite comprising metal hydride moieties. This process may be referred to as the metal hydride moiety formation step. According to embodiments, the metal hydride moiety formation step may convert organometallic moieties of the intermediate zeolite to metal hydride moieties of the second intermediate zeolite.

In one or more embodiments, where the organometallic moieties have the general structure MR₂R₃R₄, as described hereinabove, at least one of the R₂, R₃, and R₄ moieties may be replaced by hydrogen (H) during the metal hydride moiety formation step. In one or more embodiments, the metal atom of the organometallic moiety may be bonded to at least one additional bridging oxygen atom during the metal hydride moiety formation step. For example, without limitation, the metal atom of the organometallic moiety may be bonded to one or two additional bridging oxygen atoms during the metal hydride moiety formation step. In one or more embodiments, the second intermediate zeolite may comprise at least one metal hydride moiety where the metal atom is bonded to two hydrogen atoms and two bridging oxygen atoms. In one or more embodiments, the second intermediate zeolite may comprise at least one metal hydride moiety where the metal atom is bonded to one hydrogen atom and three bridging oxygen atoms.

In embodiments where the metal atom of the organometallic moiety is bonded to an additional bridging oxygen atom, a silicon hydride moiety may form. The silicon hydride moiety may comprise a silicon atom bonded to at least one bridging oxygen atom and at least one hydrogen atom. In one or more embodiments, the second intermediate zeolite may comprise silicon hydride moieties, where at least one silicon hydride moiety comprises a silicon atom bonded to one hydrogen atom and three bridging oxygen atoms. In one or more embodiments, the second intermediate zeolite may comprise silicon hydride moieties, where at least one silicon hydride moiety comprises a silicon atom bonded to two hydrogen atom and two bridging oxygen atoms.

According to one or more embodiments disclosed herein, the metal hydride moiety formation step may take place by contacting the intermediate zeolite comprising organometallic moieties with hydrogen to form a second intermediate zeolite comprising metal hydride moieties. The contacting may take place in any suitable reaction vessel. In one or more embodiments, the contacting may take place at a temperature of 20° C. to 220° C. For example, without limitation, contacting the intermediate zeolite with hydrogen may take place at a temperature from 20° C. to 220° C., from 30° C. to 220° C., from 40° C. to 220° C., from 50° C. to 220° C., from 60° C. to 220° C., from 270° C. to 220° C., from 80° C. to 220° C., from 90° C. to 220° C., from 100° C. to 220° C., from 110° C. to 220° C., from 120° C. to 220° C., from 130° C. to 220° C., from 140° C. to 220° C., from 150° C. to 220° C., from 160° C. to 220° C., from 170° C. to 220° C., from 180° C. to 220° C., from 190° C. to 220° C., from 200° C. to 220° C., from 210° C. to 220° C., from 20° C. to 210° C., from 20° C. to 200° C., from 20° C. to 190° C., from 20° C. to 180° C., from 20° C. to 170° C., from 20° C. to 160° C., from 20° C. to 150° C., from 20° C. to 140° C., from 20° C. to 130° C., from 20° C. to 120° C., from 20° C. to 110° C., from 20° C. to 100° C., from 20° C. to 90° C., from 20° C. to 80° C., from 20° C. to 70° C., from 20° C. to 60° C., from 20° C. to 50° C., from 20° C. to 40° C., from 20° C. to 30° C., or any combination of ranges formed from these endpoints.

In one or more embodiments, the pressure of hydrogen contacted with the intermediate zeolite may be any suable pressure. For example, without limitation, the pressure of hydrogen contacted with the intermediate zeolite may be from 0.5 bar(a) 1 bar(a), from 0.6 bar(a) 1 bar(a), from 0.7 bar(a) 1 bar(a), from 0.8 bar(a) 1 bar(a), from 0.9 bar(a) 1 bar(a), from 0.5 bar(a) 0.9 bar(a), from 0.5 bar(a) 0.8 bar(a), from 0.5 bar(a) 0.7 bar(a), from 0.5 bar(a) 0.6 bar(a), or any combination of ranges formed from these endpoints.

In one or more embodiments, the intermediate zeolite may be contacted with hydrogen for any suitable period of time to form the modified zeolite. For example, the intermediate zeolite may be contacted with hydrogen for a time from 1 hour to 20 hours, from 3 hours to 20 hours, from 5 hours to 20 hours, from 7 hours to 20 hours, from 9 hours to 20 hours, from 11 hours to 20 hours, from 13 hours to 20 hours, from 15 hours to 20 hours, from 17 hours to 20 hours, from 19 hours to 20 hours, from 1 hour to 18 hours, from 1 hour to 16 hours, from 1 hour to 14 hours, from 1 hour to 12 hours, from 1 hour to 10 hours, from 1 hour to 8 hours, from 1 hour to 6 hours, from 1 hour to 4 hours, from 1 hour to 2 hours, or any combination of ranges formed from these endpoints. In one or more embodiments, the intermediate zeolite may be contacted with hydrogen for a time from 8 hours to 20 hours.

Chemical Structure #16, shown below, generally depicts one reaction which is contemplated to take place when the intermediate zeolite is contacted with hydrogen to form the second intermediate zeolite comprising titanium hydride moieties. In Chemical Structure #16, the organometallic moiety is represented as TiR₂R₃R₄, and the organometallic moiety is bonded to a single bridging oxygen atom. The intermediate zeolite is contacted with hydrogen, which results in the formation of titanium hydride moieties and silicon hydride moieties. As shown in Chemical Structure #16, the titanium atom of a titanium hydride moiety may be bound to two bridging oxygen atoms and two hydrogen atoms, or the titanium atom of a titanium hydride moiety may be bound to three bridging oxygen atoms and one hydrogen atom.

In one or more embodiments, substantially all of the organometallic moieties of the intermediate zeolite may be reacted to form metal hydride moieties as described hereinabove. According to embodiments, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the organometallic moieties may be reacted to form metal hydride moieties. It is contemplated that some organometallic moieties may comprise metals other than titanium. In some embodiments, substantially all of the organometallic moieties may comprise titanium. As described herein, in embodiments where “substantially all” of the organometallic moieties comprise titanium, no organometallic moieties comprising other metals are intentionally grafted onto the initial zeolite.

In one or more embodiments, the second intermediate zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g of Group 4-6 metal, from 0.05 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.10 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.15 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.20 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.25 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.30 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.35 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.40 mmol/g to 0.45 mmol/g Group 4-6 metal, or any combination of ranges formed from these endpoints. In one or more embodiments, the second intermediate zeolite may comprise from 0.35 mmol/g to 0.45 mmol/g Group 4-6 metal. In one or more embodiments, the second intermediate zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g titanium, hafnium, or zirconium. In some embodiments, the second intermediate zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g titanium.

According to one or more embodiments disclosed herein, the second intermediate zeolite comprising metal hydride moieties may be reacted to form a modified zeolite comprising a plurality of Group 4-6 metal atoms each bonded to bridging oxygen atoms. This process may be referred to as the Group 4-6 metal moiety formation step. According to embodiments, the Group 4-6 metal moiety formation step may convert metal hydride moieties of the second intermediate zeolite to a plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms. Each of the bridging oxygen atoms bonded to the Group 4-6 metal atoms may bridge one of the plurality of Group 4-6 metal atoms and a silicon atom of the microporous framework. In one or more embodiments, the Group 4-6 metal atom may be bound only to bridging oxygen atoms.

In one or more embodiments, at least one of the hydrogen atoms of the metal hydride moiety may be removed from the metal atom such that the metal atom bonds with a bridging oxygen atom. In one or more embodiments, all of the hydrogen atoms of the metal hydride moiety may be removed from the metal atom such that the metal atom bonds with four bridging oxygen atoms. It is contemplated that while hydrogen atoms may be removed from the metal hydride moieties during the Group 4-6 metal moiety formation step, that at least a portion of the silicon hydride moieties may remain intact during the formation of the Group 4-6 metal moieties. In such embodiments, the modified zeolite may comprise Group 4-6 metal atoms bonded to four bridging oxygen atoms and silicon hydride moieties.

According to one or more embodiments described herein, the Group 4-6 metal moiety formation step may take place by heating the second intermediate zeolite comprising metal hydride moieties to form the modified zeolite comprising a plurality of Group 4-6 metal atoms bonded to four bridging oxygen atoms. In one or more embodiments, the second intermediate zeolite may be heated to a temperature from 250° C. to 500° C. to form the modified zeolite comprising Group 4-6 metal atoms bonded to four bridging oxygen atoms. For example, the second intermediate zeolite may be heated to a temperature from 250° C. to 500° C., from 300° C. to 500° C., from 350° C. to 500° C., from 400° C. to 500° C., from 450° C. to 500° C., from 250° C. to 450° C., from 250° C. to 400° C., from 250° C. to 350° C., from 250° C. to 300° C., or any combination of ranges formed from these endpoints.

In one or more embodiments, the heating may take place under a vacuum. For example, the second intermediate zeolite may be heated to form the modified zeolite comprising Group 4-6 metal atoms bonded to bridging oxygen atoms under a pressure of from 2×10⁻⁵ mbar to 5.6×10⁻⁵ mbar, from 3×10⁻⁵ mbar to 5.6×10⁻⁵ mbar, from 4×10⁻⁵ mbar to 5.6×10⁻⁵ mbar, from 5×10⁻⁵ mbar to 5.6×10⁻⁵ mbar, from 2×10⁻⁵ mbar to 5×10⁻⁵ mbar, from 2×10⁻⁵ mbar to 4×10⁻⁵ mbar, from 2×10⁻⁵ mbar to 3×10⁻⁵ mbar, or any combination of ranges formed from these endpoints.

In one or more embodiments, the second intermediate zeolite may be heated for any suitable period of time to form the modified zeolite comprising Group 4-6 metal atoms bonded to four bridging oxygen atoms. In one or more embodiments, the second intermediate zeolite may be heated for a time from 1 hour to 20 hours, from 3 hours to 20 hours, from 5 hours to 20 hours, from 7 hours to 20 hours, from 9 hours to 20 hours, from 11 hours to 20 hours, from 13 hours to 20 hours, from 15 hours to 20 hours, from 17 hours to 20 hours, from 19 hours to 20 hours, from 1 hour to 18 hours, from 1 hour to 16 hours, from 1 hour to 14 hours, from 1 hour to 12 hours, from 1 hour to 10 hours, from 1 hour to 8 hours, from 1 hour to 6 hours, from 1 hour to 4 hours, from 1 hour to 2 hours, or any combination of ranges formed from these endpoints. In one or more embodiments, the second intermediate zeolite may heated for a time from 8 hours to 20 hours, and in some embodiments from 15 hours to 18 hours.

Chemical Structure #17, shown below, generally depicts one reaction that is contemplated to take place when the second intermediate zeolite is heated under vacuum to form the modified zeolite comprising a plurality of titanium atoms each bonded to four bridging oxygen atoms. In Chemical Structure #17, the hydrogen atoms of the titanium hydride moieties are removed and the titanium atom bonds to four bridging oxygen atoms during the reaction.

In one or more embodiments, substantially all of the metal hydride moieties of the second intermediate zeolite may be reacted to form the plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms, as described hereinabove. According to embodiments, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the metal hydride moieties may be reacted to form the plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms.

In one or more embodiments, the modified zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.05 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.10 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.15 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.20 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.25 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.30 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.35 mmol/g to 0.45 mmol/g Group 4-6 metal, from 0.40 mmol/g to 0.45 mmol/g Group 4-6 metal, or any combination of ranges formed from these endpoints. In one or more embodiments, the modified zeolite may comprise from 0.35 mmol/g to 0.45 mmol/g Group 4-6 metal. In one or more embodiments, the modified zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g titanium, hafnium, or zirconium. In some embodiments, the the modified zeolite may comprise from 0.01 mmol/g to 0.45 mmol/g or from 0.35 mmol/g to 0.45 mmol/g titanium.

In one or more embodiments, the modified zeolite may have a total acidity from 0.1 mmol/g to 0.8 mmol/g. As described herein, “total acidity” refers to the sum of the Bronsted acidity and the Lewis acidity of the modified zeolite. For example without limitation, the modified zeolite may have a total acidity from 0.1 mmol/g to 0.8 mmol/g, from 0.2 mmol/g to 0.8 mmol/g, from 0.3 mmol/g to 0.8 mmol/g, from 0.4 mmol/g to 0.8 mmol/g, from 0.5 mmol/g to 0.8 mmol/g, from 0.6 mmol/g to 0.8 mmol/g, from 0.7 mmol/g to 0.8 mmol/g, from 0.1 mmol/g to 0.7 mmol/g, from 0.1 mmol/g to 0.6 mmol/g, from 0.1 mmol/g to 0.5 mmol/g, from 0.1 mmol/g to 0.4 mmol/g, from 0.1 mmol/g to 0.3 mmol/g, from 0.1 mmol/g to 0.2 mmol/g, or any range or combination of ranges formed from these endpoints

Without intending to be bound by theory, the modified zeolites comprising a plurality of Group 4-6 metal atoms bonded to four bridging oxygen atoms may have enhanced functionality as catalysts used for cracking reactions. According to one or more embodiments described herein, the modified zeolites comprising a plurality of Group 4-6 metal atoms bonded to four bridging oxygen atoms may have an improved selectivity for linear alkanes when used as a cracking catalyst when the total acidity of the catalyst is from 0.15 mmol/g to 0.55 mmol/g. Without intending to be bound by theory, modified zeolites described herein may have a low total acidity, which may contribute to the selectivity of the modified zeolite for linear alkanes. If the modified zeolite were more acidic, then linear alkanes may isomerize to produce branched alkanes, which are a less desirable feedstock for steam cracking reactions.

Without intending to be bound by theory, when the Group 4-6 metal atoms are bonded to four bridging oxygen atoms the modified zeolite has improved stability. Specifically, the Group 4-6 metal moieties of the modified zeolite may have increased stability and the modified zeolite may be less sensitive to exposure to air and moisture. Also, without intending to be bound by theory, when the modified zeolite comprises both mesopores ordered with cubic symmetry and a plurality of Group 4-6 metal atoms each bonded to the framework structure of the zeolite by four bridging oxygen atoms, the modified zeolite may exhibit bi-functional catalysis due to the vicinity of the Group 4-6 metal atoms to acid sites and the accessibility of the Group 4-6 metal atoms and acid sites to the guest species undergoing reactions.

As previously described herein, zeolites generally comprise crystalline atomic arrangements, as opposed to amorphous arrangement. Without being bound by theory, it is believed that isolated silanol moieties may not be formed on non-crystalline materials when heated. As such, it is believed that the grafting of the organometallic chemical to form the organometallic moiety on the intermediate zeolite and the subsequent formation of metal hydride moieties on the modified zeolite may not occur on non-crystalline materials.

It should be understood that, according to one or more embodiments, presently disclosed, the various functional groups of the zeolites may be identified by FT-IR and/or ¹H-NMR methods. When a zeolite “comprises” such a moiety, such inclusion may be evidenced by a peak at or near the bands in FT-IR and/or ¹H-NMR corresponding to such moiety. Such detection methods would be understood by those skilled in the art.

EXAMPLES

The various embodiments of methods and systems for forming modified zeolites will be further clarified by the following examples. The examples are illustrative in nature and should not be understood to limit the subject matter of the present disclosure.

Example 1—Synthesis of a Zeolite Comprising Mesopores Ordered with Cubic Symmetry

A quantity of 1.2 grams of urea was dissolved in 60.0 g of water to form a homogeneous solution. To this mixture, 0.2 g of ammonium nitrate (NH₄NO₃) was added to the mixture, and the mixture was stirred to form a homogeneous solution. 2.0 g of zeolite Y (obtained from Zeolyst International, product name CBV 720) was added to the mixture, and the mixture was stirred for 10 minutes. Subsequently, 3.0 milliliters of an organosilane, dimethyloctadecyl(3-trimethoxysilyl-propyl)-ammonium chloride (42.0 wt. % in methanol), was added to the mixture. The resulting solution was stirred for 0.5 hours, followed by hydrothermal treatment at 130° C. for 72 hours. The resulting mixture was filtered, washed with water and dried at 120° C. for 24 hours. The synthesized product was calcined in air at 550° C. for 6 hours with a ramp rate of 60° C./hour to yield a zeolite comprising mesopores ordered with cubic symmetry.

The zeolite comprising mesopores ordered with cubic symmetry of Example 1, was analyzed by transmission electron microscopy (TEM) using a PEI-Titan ST electron microscope operated at 300 kV. FIGS. 1A and 1B are TEM micrographs of the zeolite comprising mesopores ordered with cubic symmetry of Example 1, showing cubic mesoporous channels in the [110] and [111] directions with FAU micropore channels in the walls of the mesostructure. FIG. 1A shows the TEM micrograph at a scale of 100 nanometers, and FIG. 1B shows the TEM micrograph in the [110] direction and in the [111] direction at a scale of 20 nanometers. Additionally, FIG. 1C depicts a FAU unit cell schematic and their arrangement to provide mesopores with cubic symmetry.

The zeolite comprising mesopores ordered with cubic symmetry of Example 1 was analyzed by powder X-ray diffraction (XRD) using a Bruker D8 twin diffractometer, operating at 40 kV and 40 mA, having Cu Kα radiation (λ=0.154 nm) and a step size of 0.02°. FIG. 2A depicts the low angle XRD pattern of the zeolite comprising mesopores ordered with cubic symmetry of Example 1. As shown in FIG. 2A, the XRD pattern exhibits reflections at 211, 220, 321, 400, 420, and 332, which are characteristic of cubic mesopore symmetry of an Ia-3d space group. In FIG. 2A, the reflections at 321, 400, 420, and 332 are shown at 8 times magnification. FIG. 2B depicts a high angle XRD pattern of the zeolite comprising mesopores ordered with cubic symmetry of Example 1 (Diffractogram 201) and a high angle XRD pattern of the zeolite Y (Diffractogram 202). The retention of the underlying zeolite structure is apparent from FIG. 2B, where the peaks of the zeolite comprising mesopores ordered with cubic symmetry of Example 1 are consistent with those of the zeolite Y.

Example 2—Synthesis of a Titanium Hydride Modified Zeolite Comprising Mesopores Ordered with Cubic Symmetry

A quantity of 1.0 g of the zeolite comprising mesopores ordered with cubic symmetry of Example 1 was dehydroxylated at 700° C. to form a dehydroxylated zeolite. The dehydroxylated zeolite was placed in a double Schlenk tube. An amount of 0.502 g (1.56 mmol) of tetrakis(neopentyl)titanium was placed into the other side of the double Schlenk tube. 20 mL of dry and degassed pentane was added to the double Schlenk tube to dissolve the tetrakis(neopentyl)titanium. Then, the solution was mixed with the dehydroxylated zeolite at room temperature. The reaction continued for four hours. At the end of the reaction, the product was filtered. The product was washed three times with 20 mL of dry and degassed pentane during each wash. The product was dried under vacuum to obtain a grey powder. The product was a zeolite comprising mesopores ordered with cubic symmetry that was modified with tetrakis(neopentyl)titanium, referred to herein as the intermediate zeolite.

A quantity of 250 mg of the intermediate zeolite and pure H₂ (1 bar) were added to a batch reactor having a volume of 250 mL. The reaction mixture was heated to a temperature of 150° C. at a rate of 1° C./min. The heating was maintained at 150° C. for 15 hours. At the end of the reaction, the reactor was cooled to room temperature and then evacuated under a vacuum of 10⁻⁵ mbar to remove gaseous components from the reactor. The product was a grey solid. The product was a titanium hydride modified zeolite comprising mesopores ordered with cubic symmetry, referred to herein as the titanium hydride modified zeolite.

The dehydroxylated zeolite, the intermediate zeolite, and the titanium hydride modified zeolite were analyzed by Fourier-transform infrared spectroscopy (FTIR) in the range from 4000 to 1200 cm⁻¹. FIG. 3 depicts the FTIR spectrum of the dehydroxylated zeolite 310, the FTIR spectrum of the intermediate zeolite 320, and the FTIR spectrum of the titanium hydride modified zeolite 330. The FTIR band corresponding to single silanols appears at 3747 cm⁻¹ while two bands at 3631 cm⁻¹ and 3566 cm⁻¹ correspond to the two main kinds of OH groups in Si—O(H)—Al and bridging OH groups in sodalite cages. The band at 3597 cm⁻¹ corresponds to HF groups polarized by Lewis acid extraframework Al species. The less intense band at 3680 cm⁻¹ can be attributed to the acid Al—O(H)—Al groups.

The FTIR spectrum of the intermediate zeolite 320 shows a decrease in the single silanol band at 3747 cm⁻¹. New bands were observed in the region from 2964 cm⁻¹ to 2712 cm⁻¹ and new peaks were observed at 1362 cm⁻¹ and 1472 cm¹, which indicate the neopentyl titanium groups were grafted onto the zeolite on both single silanol moieties and Si—O(H)—Al moieties on the dehydroxylated zeolite.

The FTIR spectrum of the titanium hydride modified zeolite 330 shows a decrease of about 90% in the bands of the neopently groups (2964 cm⁻¹, 2712 cm⁻¹, 1472 cm⁻¹, and 1362 cm⁻¹, assigned respectively to ν_as(CH₃), ν_s(CH₂), δ_as(CH₃), and δ_s(CH₃)). The formation of titanium hydride groups is shown by the presence of a band at 1690 cm⁻¹ and a band at 1640 cm⁻¹. The FTIR spectrum of the titanium hydride modified zeolite 330 also shows the formation of silicon hydride moieties, characterized by two ν(Si—H) bands in the 2100 cm⁻¹ and 2300 cm⁻¹ range. The presence of the silicon hydride moieties may be due to the oxophillic character of titanium in the titanium hydride moieties, which may react with adjacent ≡Si—O—Si≡ moieties, leading to the formation of new Si—O—Ti and Si—H bonds. As a result of this process, the silicon hydride moieties may be in relatively close proximity to the titanium hydride moieties.

The intermediate zeolite and the titanium hydride modified zeolite were analyzed by solid-state nuclear magnetic resonance (NMR) spectroscopy. A one-dimensional ¹H magic-angle spinning (MAS) NMR spectrum of the intermediate zeolite was acquired on a 400 MHz NMR spectrometer (9.4 T) with a 10 kHz MAS spinning frequency, a repetition delay of 5 s, and 64 scans. The ¹H MAS NMR spectrum of the intermediate zeolite is depicted in FIG. 4A. Two-dimensional ¹H-¹H double-quantum (DQ) experiments were recorded on a Bruker AVANCE III spectrometer operating at 400 MHz with a conventional double resonance 3.2 mm CP/MAS probe, according to the following general scheme: excitation of DQ coherences, t₁ evolution, z-filter, and detection. The spectra (FIG. 4B) were recorded in a rotor-synchronized fashion in t₁ by setting the t₁ increment equal to one rotor period (45.45 ρs). One cycle of the standard back-to-back (BABA) recoupling sequences was used for the excitation and reconversion period. Quadrature detection in w₁ was achieved using the States-TPPI method. An MAS frequency of 22 kHz was used. The 900 proton pulse length was 2.5 ρs, while a recycle delay of 5 s was used. A total of 128 t₁ increments with 128 scans per increment were recorded. The DQ frequency in the w₁ dimension corresponds to the sum of two single quantum (SQ) frequencies of the two coupled protons and correlates in the w₂ dimension with the two corresponding proton resonances. The ¹H-¹H DQ NMR spectrum of the intermediate zeolite is depicted in FIG. 4B.

A ¹³C CP/MAS NMR spectrum of the intermediate zeolite was acquired on a 400 MHz NMR spectrometer (9.4 T) with a 10 kHz MAS frequency, 5K scans, a 4 s repetition delay, and a 2 ms contact time. Exponential line broadening of 80 Hz was applied before Fourier transformation. The ¹³C CP/MAS NMR spectrum of the intermediate zeolite is depicted in FIG. 5. A 2D 1H-¹³C CP/MAS dipolar HETCOR spectrum of the intermediate zeolite was acquired on a 400 MHz NMR spectrometer (9.4 T) with a 10 kHz MAS frequency, 2000 scans per t₁ increment, a 4 s repetition delay, 64 individual t1 increments and a 0.2 ms contact time. The 2D HETCOR spectrum of the intermediate zeolite is depicted in FIG. 6.

The MAS NMR spectrum of the intermediate zeolite depicted in FIG. 4A shows two signals at 2.2 ppm and 1.34 ppm for a methylene proton and a signal at 0.95 ppm for a methyl proton. To further verify, Double-quantum (DQ) and Triple-quantum (TQ) NMR studies were conducted and the spectra are depicted in FIG. 4B. The ¹H-¹H DQ NMR spectrum of the intermediate zeolite depicted in FIG. 4B displays two broad signals at 2.2 ppm and 1.34 ppm that are found to be auto-correlated in a double quantum (DQ) experiment to protons from a methylene group. The ¹H-¹H DQ NMR spectrum of the intermediate zeolite depicted in FIG. 4B displays a third peak at 0.95 ppm that correlates in a Triple quantum (TQ) experiment to protons from a methyl carbon at 20 kHz MAS.

Similarly, the ¹³C CP/MAS NMR spectrum of the intermediate zeolite depicted in FIG. 5 shows a peak at 31 ppm corresponding to the carbon atom of the —CH₃ of the neopentyl group bonded to Ti and Al, a peak at 35 ppm corresponding to the —CH₂ of the neopently group, and three peaks at 113, 119 and 124 ppm corresponding to the —CH₂ of the monopodal, bipodal and cationic Ti complex, this type of observation is already reported in the literature (Organometallics 2020, 39, 4608). To further confirm, the 2D HETCOR spectrum of the intermediate zeolite depicted in FIG. 6 shows a correlation between the methyl proton at 0.96 ppm and the carbon peak at 31 ppm confirming the carbon-proton pairs to be methyl groups. The proton at 1.34 ppm correlates with the carbon peak at 113 and 119 ppm and the peak at 2.2 ppm correlates with the carbon at 124 ppm allowing the assignment of the carbon-proton pairs to be methylene groups of titanium.

A ¹H MAS NMR spectrum of the titanium hydride modified zeolite was acquired on a 400 MHz NMR spectrometer (9.4 T) with a 10 kHz MAS frequency, a repetition delay of 5 s, and 64 scans. The ¹H MAS NMR spectrum of the titanium hydride modified zeolite is depicted in FIG. 7. The ¹H MAS NMR spectrum of the titanium hydride modified zeolite includes six signals at 0.9 ppm, 1.9 ppm, 4.1 ppm, 4.5 ppm, 8.5 ppm, and 13.5 ppm. These peaks correspond to supported titanium hydride moieties, silicon hydride moieties, and residual neopentyl groups present on the support, as shown in FIG. 7.

Example 3—Synthesis of a Modified Zeolite Comprising Titanium Atoms Each Bonded to Four Bridging Oxygen Atoms and Mesopores Ordered with Cubic Symmetry

A quantity of 70 mg of the titanium hydride modified zeolite of Example 2 was added to a batch reactor having a volume of 250 mL. The titanium hydride modified zeolite of Example 2 was heated to 300° C. at a rate of 100° C./hr under a vacuum of 10⁻⁵ mbar. The temperature and pressure were maintained at 300° C. and 10⁻⁵ mbar for 15 hours. At the end of the reaction, the reactor was cooled to room temperature. The product was a modified zeolite comprising titanium atoms bonded to four bridging oxygen atoms and mesopores ordered with cubic symmetry, referred to herein as the titanium modified zeolite.

The titanium modified zeolite was analyzed by FTIR spectroscopy in the range from 4000 to 1200 cm⁻¹. The FTIR spectrum of the titanium modified 340 zeolite is also depicted in FIG. 3. Referring again to FIG. 3, the typical vibrational bands of titanium hydride groups at 1690 cm⁻¹ and 1640 cm⁻¹ disappeared in the FTIR spectrum of the titanium modified 340. This is indicative of the conversion of the titanium hydride moieties to titanium atoms bonded to four bridging oxygen atoms.

The acid properties of the zeolite comprising mesopores ordered with cubic symmetry of Example 1, the dehydroxylated zeolite of Example 2, and the titanium modified zeolite of Example 3, the were determined by analyzing the FTIR spectrum of each zeolite. FIG. 8 depicts the FTIR spectra in the range from 1700 cm⁻¹ to 1400 cm⁻¹ for the zeolite comprising mesopores ordered with cubic symmetry of Example 1 (Spectrum 830), the dehydroxylated zeolite of Example 2 (Spectrum 820), the titanium modified zeolite of Example 3 (Spectrum 810). The peak corresponding to Bronsted acidity (1545 cm⁻¹) is labeled with a “B′ in FIG. 8 and the peak corresponding to Lewis acidity (1455 cm⁻¹) is labeled with an “L” in FIG. 8. The acid properties for each of the zeolites is listed in Table 1.

	TABLE 1
		Bronsted	Lewis	Total
		Acidity	Acidity	Acidity
	Zeolite	(mmol/g)	(mmol/g)	(mmol/g)
	Mesoporous Zeolite of	0.13	0.07	0.2
	Example 1
	Dehydroxylated Zeolite	0.08	0.06	0.14
	of Example 2
	Ti Modified Zeolite of	0.08	0.31	0.39
	Example 3

Example 4—Cracking of Eicosane Using the Titanium Hydride Modified Zeolite of Example 2

The titanium hydride modified zeolite of Example 2 was used as a catalyst for hydrogenolysis (cracking) of eicosane (C₂₀H₄₂). 50 mg (0.0145 mmol) of the titanium hydride modified zeolite of Example 2 was mixed with 500 mg (1.766 mmol) of eicosane in a batch reactor inside a glovebox. The weight of titanium metal in the 50 mg of titanium hydride modified zeolite of Example 2 was 0.7 mg, as determined by an inductively coupled plasma mass spectrometry analysis. The weight ratio of reactant to titanium metal in the catalyst was 714. The reaction mixture was connected to a vacuum socket, the socket was closed, and the reactor was removed from the glovebox. The reactor was connected to a high vacuum line and evacuated to a pressure of 10⁻⁵ mbar. Grade 5 hydrogen gas was passed into the reactor to maintain a pressure of 1 atm. The reactor was connected to a condenser to avoid the release of low boiling point compounds, such as pentane. The reactor was heated to a temperature of 180° C. for a time of 48 hours. At the end of the reaction, the reaction mixture was cooled and then the reaction was quenched with 4 mL of toluene. After quenching the reaction, the product was filtered and analyzed by gas chromatography and mass spectrometry. A 100% conversion of eicosane to C₅ to C₁₂ alkanes and a gaseous product was observed. Without intending to be bound by theory, a synergistic effect between the titanium hydride moieties (Lewis sites) and Al—OH moieties (Bronsted sites) may enhance the C—C bond cleavage of waxes into lower alkanes, which may contribute to the observed 100% conversion. Additionally, a considerable amount of branched alkanes was observed among the linear alkanes of the product.

Example 5—Cracking of Eicosane Using the Titanium Modified Zeolite of Example 3

The titanium modified zeolite of Example 3 was used as a catalyst for hydrogenolysis (cracking) of eicosane (C₂₀H₄₂). 50 mg (0.02 mmol) of the titanium modified zeolite of Example 3 was mixed with 500 mg (1.766 mmol) of eicosane in a batch reactor under an inert atmosphere inside a glovebox. The reaction was performed as described in Example 4. After quenching the reaction, the product was filtered and analyzed by gas chromatography and mass spectrometry. A 96% conversion of eicosane to C₁ to C₁₉ alkanes. The reaction was selective to linear alkanes and a very low amount of branched alkanes were observed. Without intending to be bound by theory, the low acidity of the titanium modified zeolite of Example 3 contributed to the selectivity of the titanium modified zeolite for linear alkanes because there were fewer acid sites at which branched alkanes may be produces through isomerization.

In a first aspect of the present disclosure, a method for processing a hydrocarbon feedstock comprises cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a modified zeolite in the presence of hydrogen to form an intermediate cracked product and steam cracking at least a portion of the intermediate cracked product to form a steam cracked product. The hydrocarbon feedstock comprises at least 20 wt. % of one or more alkanes. The intermediate cracked product comprises at least 30 wt. % of one or more linear alkanes. The modified zeolite comprises a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm. The microporous framework comprises at least silicon atoms and oxygen atoms. The modified zeolite also comprises a plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms, wherein each of the bridging oxygen atoms bonded to the Group 4-6 metal atoms bridges one of the plurality of the Group 4-6 metal atoms and a silicon atom of the microporous framework.

A second aspect of the present disclosure may include the first aspect, wherein the intermediate cracked product is not processed as to change its composition before being steam cracked.

A third aspect of the present disclosure may include either the first or second aspect, wherein the intermediate cracked product is not reverse isomerized before being steam cracked.

A fourth aspect of the present disclosure may include any of the first through third aspects, wherein the hydrocarbon feedstock comprises at least 90 wt. % C₁₅ to C₁₀₀ alkanes.

A fifth aspect of the present disclosure may include any of the first through fourth aspects, wherein the hydrocarbon feedstock comprises from 20 wt. % to 60 wt. % paraffinic hydrocarbons; from 20 wt. % to 60 wt. % naphthenic hydrocarbons; and from 1 wt. % to 10 wt. % aromatic hydrocarbons.

A sixth aspect of the present disclosure may include any of the first through fifth aspects, wherein contacting the hydrocarbon feedstock with the modified zeolite occurs at a temperature from 100° C. to 450° C.

A seventh aspect of the present disclosure may include any of the first through sixth aspects, wherein contacting the hydrocarbon feedstock with the modified zeolite occurs under a partial pressure of hydrogen from 0.5 mbar to 1.5 mbar.

An eighth aspect of the present disclosure may include any of the first through seventh aspects, wherein the hydrocarbon feedstock and the modified zeolite are contacted in a reactor at a liquid hour space velocity from 0.02 hr⁻¹ to 10 hr⁻¹.

A ninth aspect of the present disclosure may include any of the first through eighth aspects, wherein the intermediate cracked product comprises at least 50 wt. % linear alkanes.

A tenth aspect of the present disclosure may include any of the first through ninth aspects, wherein the steam cracked product comprises from 20 wt. % to 75 wt. % ethylene.

An eleventh aspect of the present disclosure may include any of the first through tenth aspects, wherein the Group 4-6 metal atoms are selected from titanium, hafnium, zirconium, and combinations thereof.

A twelfth aspect of the present disclosure may include any of the first through eleventh aspects, wherein the Group 4-6 metal atoms comprise titanium.

A thirteenth aspect of the present disclosure may include any of the first through twelfth aspects, wherein the modified zeolite comprises a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm.

A fourteenth aspect of the present disclosure may include the thirteenth aspect, wherein the plurality of mesopores are ordered with cubic symmetry.

A fifteenth aspect of the present disclosure may include any of the first through fourteenth aspects, wherein the modified zeolite has a total acidity from 0.15 mmol/g to 0.55 mmol/g.

A sixteenth aspect of the present disclosure may include any of the first through fifteenth aspects, wherein the modified zeolite comprises from 0.01 mmol/g to 0.45 mmol/g of the Group 4-6 metal.

A seventeenth aspect of the present disclosure may include any of the first through sixteenth aspects, wherein the mesopores are ordered with cubic symmetry having an Ia-3d, Fm-3m, Pm-3n, Pn-3m or Im-3m space group.

An eighteenth aspect of the present disclosure may include any of the first through seventeenth aspects, wherein the microporous framework further comprises aluminum atoms, and a ratio of silicon atoms to aluminum atoms is from 1.5 to 1500.

A nineteenth aspect of the present disclosure may include any of the first through eighteenth aspects, wherein a surface area of the modified zeolite is from 200 m²/g to 1500 m²/g and a total pore volume of the modified zeolite is from 0.01 to 1.5 cm³/g.

A twentieth aspect of the present disclosure may include any of the first through nineteenth aspects, wherein the modified zeolite further comprises silicon hydride moieties each bonded to bridging oxygen atoms.

The subject matter of the present disclosure has been described in detail and by reference to specific embodiments. It should be understood that any detailed description of a feature of an embodiment does not necessarily imply that the feature is essential to the particular embodiment or to any other embodiment. Further, it should be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

For the purposes of describing and defining the present disclosure it is noted that the terms “about” or “approximately” are utilized in this disclosure to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms “about” and/or “approximately” are also utilized in this disclosure to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

It should be understood that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure.

It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.” It should be understood that where a first component is described as “comprising” a second component, it is contemplated that, in some embodiments, the first component “consists” or “consists essentially of” that second component. The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim, and the transitional phrase “consisting essentially of” is a limitation to the specified materials or steps and those that do not materially affect the basic and novel characteristics of the claimed embodiment.

Claims

1. A method of processing a hydrocarbon feedstock, the method comprising: cracking at least a portion of the hydrocarbon feedstock by contacting the hydrocarbon feedstock with a modified zeolite in the presence of hydrogen to form an intermediate cracked product, wherein: the hydrocarbon feedstock comprises at least 20 wt. % of one or more alkanes;the intermediate cracked product comprises at least 30 wt. % of one or more linear alkanes; andthe modified zeolite comprises: a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm, wherein the microporous framework comprises at least silicon atoms and oxygen atoms; anda plurality of Group 4-6 metal atoms each bonded to four bridging oxygen atoms, wherein each of the bridging oxygen atoms bonded to the Group 4-6 metal atoms bridges one of the plurality of the Group 4-6 metal atoms and a silicon atom of the microporous framework; andsteam cracking at least a portion of the intermediate cracked product to form a steam cracked product.

2. The method of claim 1, wherein the intermediate cracked product is not processed as to change its composition before being steam cracked.

3. The method of claim 1, wherein the intermediate cracked product is not reverse isomerized before being steam cracked.

4. The method of claim 1, wherein the hydrocarbon feedstock comprises at least 90 wt. % C15 to C100 alkanes.

5. The method of claim 1, wherein the hydrocarbon feedstock comprises from 20 wt. % to 60 wt. % paraffinic hydrocarbons; from 20 wt. % to 60 wt. % naphthenic hydrocarbons; and from 1 wt. % to 10 wt. % aromatic hydrocarbons.

6. The method of claim 1, wherein contacting the hydrocarbon feedstock with the modified zeolite occurs at a temperature from 100° C. to 450° C.

7. The method of claim 1, wherein contacting the hydrocarbon feedstock with the modified zeolite occurs under a partial pressure of hydrogen from 0.5 mbar to 1.5 mbar.

8. The method of claim 1, wherein the hydrocarbon feedstock and the modified zeolite are contacted in a reactor at a liquid hour space velocity from 0.02 hr−1 to 10 hr−1.

9. The method of claim 1, wherein the intermediate cracked product comprises at least 50 wt. % linear alkanes.

10. The method of claim 1, wherein the steam cracked product comprises from 20 wt. % to 75 wt. % ethylene.

11. The method of claim 1, wherein the Group 4-6 metal atoms are selected from titanium, hafnium, zirconium, and combinations thereof.

12. The method of claim 1, wherein the Group 4-6 metal atoms comprise titanium.

13. The method of claim 1, wherein the modified zeolite comprises a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm.

14. The method of claim 13, wherein the plurality of mesopores are ordered with cubic symmetry.

15. The method of claim 1, wherein the modified zeolite has a total acidity from 0.15 mmol/g to 0.55 mmol/g.

16. The method of claim 1, wherein the modified zeolite comprises from 0.01 mmol/g to 0.45 mmol/g of the Group 4-6 metal.

17. The method of claim 1, wherein the mesopores are ordered with cubic symmetry having an Ia-3d, Fm-3m, Pm-3n, Pn-3m or Im-3m space group.

18. The method of claim 1, wherein the microporous framework further comprises aluminum atoms, and a ratio of silicon atoms to aluminum atoms is from 1.5 to 1500.

19. The method of claim 1, wherein a surface area of the modified zeolite is from 200 m2/g to 1500 m2/g and a total pore volume of the modified zeolite is from 0.01 to 1.5 cm3/g.

20. The method of claim 1, wherein the modified zeolite further comprises silicon hydride moieties each bonded to bridging oxygen atoms.