Patent Application
20210171356
This invention generally relates to a process to perform controlled alkaline treatments on inorganic porous solids, yielding superior physico-chemical and catalytic properties, while the particle and crystal size is not negatively influenced. Accordingly, the solids obtained in this fashion can be easily recovered from the alkaline solution.
Zeolites are microporous aluminosilicate oxide structures that have well-defined pore structures due to a high degree of crystallinity. Crystalline aluminosilicate zeolites can have a natural and a synthetic origin. In the protonic form, the crystalline aluminosilicate zeolites are generally represented by the formula, HxAlxSi1-xO2, where “H” is a (exchangeable) proton that balances the electrovalence of the tetrahedra. The amount of exchangeable protons is referred to as the cation exchange capacity (CEC). The exact structure type of an aluminosilicate zeolite is generally identified by the particular silicon to aluminium molar ratio (Si/Al) and the pore dimensions of the cage structures. The size of the micropores (typically in the range of 0.4-1 nm) can be indicated with the number of T-atoms on the smallest diameter, the so called ‘membered rings’ (MRs). Using this definition, most common industrial zeolites feature micropores of 8 MRs, 10 MRs, or 12 MRs. The zeolite structure can also be made using, in addition to silica and alumina, phosphates, giving rise to the class of crystalline microporous silicoaluminophosphates (SAPOs). In addition, when silica is no longer present, crystalline microporous aluminophosphates (AlPOs) are formed. SAPOs and AlPOs possess, like zeolites, unique porous and acidic properties enabling them wide scale industrial application in catalysis, adsorption, and ion exchange.
Recently, hierarchical (mesoporous) zeolites, SAPOs, and AlPOs have attracted substantial attention because of their potential advantages in catalysis due to their high external surface area, reduced diffusion path lengths, and exposed active sites. The introduction of a secondary network of mesopores (typically in the range of 2-50 nm) leads to substantial changes in the properties of materials, which have an impact on the performance of zeolites in traditional application areas such as catalysis and separation. The number of accessible active sites increases rapidly with the enhanced porosity of the material. Additionally, the hierarchical zeolite crystals display reduced diffusion path lengths relative to conventional microporous zeolites, AlPOs, or SAPOs. Accordingly, these materials have attained superior performance in many catalytic reactions, such as cracking, alkylations, and isomerisations.
Hierarchical zeolites can be made using a wide variety of bottom-up and top-down procedures. Bottom-up procedures imply a change in the hydrothermal synthesis of the zeolites, for example by using organic templates or by lengthening the crystallization time. However, the most industrially attractive variant is the (top-down) post-synthetic modification of conventional commercially-available microporous zeolites. A key treatment in the latter category is the application of a base treatment, so called ‘desilication’. This approach entails contacting zeolites in alkaline aqueous solutions, yielding hierarchical zeolites by removing part of the solid to give way to intra-crystalline or inter-crystalline mesopores. Base treatments enable to convert nearly any conventional zeolite into its superior hierarchical analogue. Also, for SAPOs and AlPOs, base treatments enable to yield a superior catalytic counterpart.
Besides the aim of mesopore formation, thereby producing hierarchical crystalline materials, alkaline treatments can also be performed to wash unwanted phases from bi-phasic materials. For example, NaOH leaching can be used to remove undesirable ZSM-5 impurities from ZSM-22 zeolites. In addition, base leaching can be used to selectively leach elements from materials comprising a wide variety of elements. For example, when applied on zeolites, base leaching is selective to silicon. Conversely, when applied to SAPOs, base leaching is mostly selective to phosphorus. Hereby, base treatments enable to tune, besides the (meso)porosity, other physico-chemical properties of the resulting material, such as the bulk composition, distribution of elements in the crystals, and acidity.
Base treatments are performed by directly adding the zeolite to an aqueous solution of base, typically at high pH (>12), hence high base concentration (for example >0.1 M NaOH). This procedure is followed by filtration, typically executed by Buchner filtration. For 10 MR zeolites, for example framework topologies such as MFI, FER, TON, the use of only an inorganic base (typically NaOH) in the alkaline treatment typically suffices. However, for 12 MR zeolites, such as zeolites with the FAU or BEA topology, the addition of organics, such as tetrapropylammonium bromide (TPABr) or diethylamine, to the alkaline solution may be required to maintain the intrinsic zeolite properties, such as crystallinity, acidity, and microporosity. SAPOs and AlPOs are in general more sensitive than zeolites, requiring the use of (inorganic) salt-free alkaline solutions prepared by amines or TPAOH to yield superior solids.
Alkaline (base) treatments are often performed as a single treatment within a sequence of post-synthetic modifications. For example, to prepare a catalytically-superior hierarchical Y zeolite, a sequence of 3 consequent acid-base-acid treatments can be performed. Alternatively, for clinoptilolite (natural zeolite), a sequence of 6 consecutive treatments (acid 4 times, base, acid) was reported. Additionally, for ZSM-5 and ZSM-22 two treatments (base-acid) were reported. Following each individual treatment a filtration and drying step are required. In general, the acid treatment prior to the base treatment effectively removes aluminium from the zeolite framework, hereby enhancing the efficiency of the subsequent base treatment. Conversely, the acid treatment performed after the base treatment has been described as a mild acid wash, and is aimed predominantly at removing ‘Al-debris’ from the external surface. This Al debris has formed during the prior alkaline treatment. The efficiency of the acid wash is therefore closely tied to the efficiency of the prior alkaline treatment.
Besides the aforementioned advantages of the base leaching, it is imperative to highlight several severe disadvantages of base leaching. Firstly, the use of organics should be largely avoided, as they need to be removed by combustion. Not only does this process destruct the costly organics, the formed combustion products need to be carefully taken care of, which is a costly procedure in itself. Simple amines, such as diethylamine, used as base to leach 12 MR zeolites (beta and USY), AlPOs, and SAPOs, may be easily recovered due to their high volatility, enhancing its industrial appeal. However, the use of tetraalkylammonium cations (TAAs), such as TPABr and cetyltrimethylammonium bromide (CTABr), is preferably avoided as these are more costly, and they need to be removed by heat treatment giving rise to undesired streams such as CO2, NOx, H2O, and/or explosive organics. It is therefore of eminent importance to reduce the use of organics, especially TAAs.
Secondly, base leached zeolites, even under reportedly optimal conditions with organic molecules, typically display strongly enhanced mesoporosities. However, more often than not, they also can display undesired reductions of zeolitic properties. Representative examples hereof are the crystallinity, Brønsted acidity, and microporosity. These reductions have been reported for most hierarchical or mesoporous zeolites, as demonstrated in Table A of the example section.
An important recent development has been the realization that besides the amount of secondary porosity, the quality of the pore is of crucial importance too. It has been observed that, especially in high silica zeolites (Si/Al>ca. 10), base leaching may give rise to mesopores that are (partially) cavitated. In this case, the larger the cavitation, the smaller the catalytic benefits. Hence, at a constant mesopore surface or volume, the smallest possible degree of mesopore cavitation is desired.
Finally, base treatment can give rise to a pronounced reduction of the zeolite crystal size. This reduction is related to a fragmentation which may give rise to fragments in the size range of 5-100 nm. These represent colloidally-stable particles that are very hard to separate using conventional filtration techniques over porous filter membranes, and require the use of costly industrial separation techniques, such as high-speed commercial centrifuges. Accordingly, the zeolite suspensions after base leaching are often extremely hard to filter, as demonstrated in Table A of the example sample.
Hence, it is desirable to provide a more efficient process that yields the same base leaching effect (enhanced mesoporosity), but yields solids comprising higher intrinsic zeolitic properties, a reduced degree of cavitation, a reduced amount of organic supplements, and/or preserved crystal size. In addition, such superior process preferably features a similar or reduction of the number of steps involved, the overall process time, and the amount of formed waste water. The obtained materials may have improved properties for the preparation of technical catalysts, or for use in catalysis, adsorptive or ion exchange processes.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to a process to perform alkaline treatment on inorganic porous solids yielding superior physico-chemical (zeolitic) and catalytic properties. These superior properties may the combination of an enhanced mesoporosity with a higher Brønsted acidity, a higher microporosity, a higher mesoporosity, a higher crystallinity, a larger fraction of framework aluminium, a reduced degree of cavitation of the mesopores, a larger crystal size, and/or combinations hereof.
In an aspect, the invention relates to a method for preparing a treated inorganic porous solid, wherein the method comprises a number of separate treatments (z) which are separated by a solid separation step, such as a filtration step, each of the z treatments comprising the steps of:
In some preferred embodiments, the maximum amount of base mb,max of mb(t) at any given time t in step c) is at most than 0.75*mb,total, preferably at most than 0.50*mb,total, preferably at most than 0.25*mb,total.
In some preferred embodiments, the inorganic porous solid comprises a molecular sieve, such as a zeolite or SAPO.
In some preferred embodiments, step a) comprises:
In some preferred embodiments, the method comprises a number of base additions per treatment (x) which are not separated by a solid separation step, such as a filtration step, and an amount of base added per addition (mb,i with i=1 . . . x), characterized in that x is not equal to 1, preferably wherein x is at least 2, preferably at least 3, preferably at least 4.
In some preferred embodiments, z is 1.
In some preferred embodiments, the rate of adding the amount of base over time is at most 3.0 mmol g−1 min−1, preferably at most 1.0 mmol g−1 min−1, preferably at most 0.5 mmol g−1 min−1.
In some preferred embodiments, the base is continuously added to the inorganic porous solid during a time frame Δt, wherein the time frame Δt for adding the total amount of base mb,total is at least 15 s.
In some preferred embodiments, the method is followed by a sequential acid treatment.
In an aspect, the invention relates to a treated inorganic porous solid obtainable by the method according to any one of the aspects and embodiments described herein.
In an aspect, the invention relates to a zeolite with the faujasite topology, preferably prepared according to the method according to any one of the aspects and embodiments described herein, with a unit cell size ranging from 24.375 Å to 24.300 Å with a mesopore volume of at least 0.35 ml/g and one or more of the following features:
a Brønsted acidity of at least 400 μmol g−1, as measured with pyridine;
a fraction of Al in the framework of at least 0.5; and/or,
a crystallinity of at least 75% relative to a standard NaY zeolite, and at least 90% compared to NIST standard alumina (SRM 676).
In an aspect, the invention relates to a zeolite with the faujasite topology, preferably prepared according to the method according to any one of the aspects and embodiments described herein, with a unit cell size of at most 24.300 Å, with a mesopore volume of at least 0.35 ml g−1, and one or more of the following features:
a micropore volume of at least 0.22 ml g−1;
a crystallinity of at least 95% compared to a commercial NaY zeolite, and at least 130% compared to NIST standard alumina (SRM 676);
a mesopore cavitation ratio of at most 1.6, as measured with nitrogen adsorption; and/or,
with a particle size Deff of at least 350 nm.
In an aspect, the invention relates to a zeolite with the MFI topology, preferably prepared according to the method according to any one of the aspects and embodiments described herein, with a molar Si/Al ratio of at most 400, with a mesopore volume of at least 0.30 ml g−1 and a crystallinity of at least 330% compared to NIST standard alumina (SRM 676).
In an aspect, the invention relates to a method for preparing a technical catalyst, the method comprising the steps of:
In an aspect, the invention relates to the use of a treated inorganic porous solid according to any one of the aspects and embodiments described herein, in catalysis, adsorptive or ion exchange processes.
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background of the Invention or the following Detailed Description.
The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents thereof.
Several documents are cited throughout the text of this specification. Each of the documents herein (including any manufacturer's specifications, instructions etc.) are hereby incorporated by reference; however, there is no admission that any document cited is indeed prior art of the present invention.
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.
It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to the devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.
It is intended that the specification and examples be considered as exemplary only.
Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are part of the description and are a further description and are in addition to the preferred embodiments of the present invention.
Each of the claims set out a particular embodiment of the invention.
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.
Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
The following terms are provided solely to aid in the understanding of the invention.
The term “room temperature” as used in this application means a temperature in the range of 12 to 30 deg. C., preferably in the range of 16 to 28 deg. C., more preferably in the range of 17 to 25 deg. C. and most preferably is roughly 20 to 23 deg. C.
The term “molecular sieve” as used herein refers to a solid with pores the size of molecules. It includes but is not limited to microporous and mesoporous materials, AlPOs and (synthetic) zeolites, pillared or non-pillared clays, clathrasils, clathrates, carbon molecular sieves, mesoporous silica, silica-alumina (for example, of the MCM-41-type, with an ordered pore system), microporous titanosilicates such as ETS-10, urea and related host substances, porous metal oxides. Molecular sieves can have multimodal pore size distribution, also referred to as ordered ultramicropores (typically less than 0.7 nm), supermicropores (typically in the range of about 0.7-2 nm) or mesopores (typically in the range of about 2 nm-50 nm).
A particular type of molecular sieve envisaged within the present invention are the silica molecular sieves, more particularly silica zeogrids, zeolites, and/or amorphous microporous silica materials. Among solid substances known thus far, those having uniform channels, such as zeolites represented by porous crystalline aluminium silicates and porous crystalline aluminium phosphates (AlPO) are defined as molecular sieves, because they selectively adsorb molecules smaller than the size of the channel entrance or they allow molecules to pass through the channel. In view of crystallography, zeolites are fully crystalline substances, in which atoms and channels are arranged in complete regularity. These fully crystalline molecular sieves are obtained naturally or synthesized through hydrothermal reactions. The number of fully crystalline molecular sieves obtained or synthesized thus far amounts to several hundreds of species. They play an important role as catalysts or supports in modern chemical industries by virtue of their characteristics including selective adsorption, acidity and ion exchangeability. Molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline silicates. These silicates can be described as a rigid three-dimensional framework of SiO4 and Periodic Table Group 13 element oxide, e.g. AlO4, in which tetrahedra are crosslinked by the sharing of oxygen atoms whereby the ratio of the total Group 13 and Group 14, e.g. silicon, atoms to oxygen atoms is 1:2. Crystalline microporous silicon dioxide polymorphs represent compositional end members of these compositional material families. These silica molecular sieves do not have cation exchange capacity.
A “zeolite” can be defined as a crystalline material of which the chemical composition includes essentially aluminium, silicon and oxygen. Typically, zeolites are described as aluminosilicates with a three dimensional framework and molecular sized pores. Zeolites, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or windows. These cavities and pores are uniform in size within a specific zeolite material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials are known as “molecular sieves” and are utilized in a variety of ways to take advantage of these properties. The term zeolite, as used in disclosing the present invention, can also mean means any member of a group, of structured aluminosilicate minerals comprising cations such as sodium and calcium or, less commonly, barium, beryllium, lithium, potassium, magnesium and strontium; characterized by the equation, HxAlxSi1-xO2, where H can be replaced by any other univalent cation, or (when the x related to H is divided by the valence) a multivalent cation. The term zeolite also refers to an open tetrahedral framework structure capable of ion exchange, and loosely held water molecules, that allow reversible dehydration. The term “zeolite” also includes “zeolite-related materials” or “zeotypes” which are prepared by replacing Si4+ or Al3+ with other elements as in the case of aluminophosphates (e.g., MeAPO, SAPO, ElAPO, MeAPSO, and ElAPSO), gallophosphates, zincophosphates, titanosilicates, etc. The zeolite can be a crystalline porous material with a frame work as described in US2013/0118954 or provided in the Zeolite Framework Types database of the IZA structure commission where under the following structure types (from which also the framework density can be derived), as defined by the International Zeolite Association such as ABW type, ACO type, AEI type, AEL type, AEN type, AET type, AFG AFI type, AFN type, AFO type, AFR type, AFS type, AFT type, AFX type, AFY type, AHT type, ANA type, APC type, APD type, AST type, ASV type, ATN type, ATO type, ATS type, ATT type, ATV type, AWO type, AWW type, BCT type, BEA type, BEC type, BIK type, BOG type, BPH type, BRE type, CAN type, CAS type, CDO type, CFI type, CGF type, CGS type, CHA type, CHI type, CLO type, CON type, CZP type, DAC type, DDR type, DFO type, DFT type, DOH type, DON type, EAB type, EDI type, EMT type, EON type, EPI type, ERI type, ESV type, ETR type, EUO type, EZT type, FAR type, FAU type, FER type, FRA type, GIS type, GIU type, GME type, GON type, GOO type, HEU type, IFR type, IHW type, IMF type, ISV type, ITE type, ITH type, ITW type, IWR type, IWV type, IWW type, JBW type, KFI type, LAU type, LEV type, LIO type, LIT type, LOS type, LOV type, LTA type, LTL type, LTN type, MAR type, MAZ type, MEI type, MEL type, MEP type, MER type, MFI type, MFS type, MON type, MOR type, MOZ type, MSE type, MSO type, MTF type, MTN type, MTT type, MTW type, MWW type, NAB type, NAT type, NES type, NON type, NPO type, NSI type, OBW type, OFF type, OSI type, OSO type, OWE type, PAR type, PAU type, PHI type, PON type, RHO type, RON type, RRO type, RSN type, RTE type, RTH type, RUT type, RWR type, RWY type, SAO type, SAS type, SAT type, SAV type, SBE type, SBN type, SBS type, SBT type, SFE type, SFF type, SFG type, SFH type, SFN type, SFO type, SGT type, SIV type, SOD type, SOS type, SSF type, SSY type, STF type, STI type, STO type, STT type, SZR type, TER type, THO type, TOL type, TON type, TSC type, TUN type, UEI type, UFI type, UOZ type, USI type, UTL type, VET type, VFI type, VNI type, VSV type, WEI type, WEN type, YUG type and ZON type. The term “zeolite” also includes “zeolite-related materials” or “zeotypes” which are prepared by replacing Si4+ or Al3+ with other elements as in the case of aluminophosphates (e.g., MeAPO, AlPO, SAPO, ElAPO, MeAPSO, and ElAPSO), gallophosphates, zincophosphates, titanosilicates, etc.
Generally, porous substances are divided by pore size, for example, pore sizes smaller than 2 nm classified as microporous substances, between 2 and 50 nm classified as mesoporous substances and larger than 50 nm classified as macroporous substances. Non-zeolitic mesoporous silicas, such as MCM-41 and SBA-15, can display substantial microporosity. This type of microporosity is however ‘non-ordered’ and not well-defined, and should not be considered zeolitic. The microporosity as defined within the embodiments of this contribution is derived primarily from the zeolitic micropores related to the framework topologies. For example, for the USY zeolites with faujasite topology the microporosity is derived from the well-defined 0.74 nm micropores, for zeolite beta with BEA topology the microporosity stems from the well-defined 0.6 nm pores, and for zeolite ZSM-5 with MFI topology the microporosity stems from the well-defined 0.55 nm pores.
Of the porous substances, those having uniform channels, such as zeolite, are defined as molecular sieves. Up to hundreds of types of species have been found and synthesized thus far. Zeolites play an important role as catalysts or carriers in modern chemical industries by virtue of their characteristics including selective adsorptivity, acidity and ion exchangeability.
A series of ordered mesoporous materials, including MCM-41 and MCM-48, was reported in U.S. Pat. Nos. 5,057,296 and 5,102,643. These ordered materials show a structure in which mesopores uniform in size are arranged regularly. MCM-41, has a uniform structure exhibiting hexagonal arrangement of straight mesopores, such as honeycomb, and has a specific surface area of about 1000 m2/g as measured by ordinary BET. Existing molecular sieves have been produced by using inorganic or organic cations as templates, whereas those ordered mesoporous materials are synthesized through a liquid crystal template pathway by using surfactants as templates. These ordered mesoporous materials have the advantage that their pore sizes can be adjusted in a range of 1.6 nm to 10 nm by controlling the kinds of surfactants or synthesis conditions employed during the production process. Ordered mesoporous materials designated as SBA-1, -2 and 3 were reported in Science (1995) 268:1324. Their channels are regularly arranged, while the constituent atoms show an arrangement similar to that of amorphous silica. Ordered mesoporous materials have regularly arranged channels larger than those of existing zeolites, thus enabling their application to adsorption, isolation or catalytic conversion reactions of relatively large molecules.
In general, the present invention concerns a process of controlled treatment of alkaline treatment to treat inorganic porous solids, for instance crystalline solid particles, without a negative influence on the particle or crystal size, and to obtain an end product of solids with superior physico-chemical and catalytic properties. The process of the present invention may yield solids which are easily recovered from the alkaline solution after treatment. In a particular embodiment the process comprises the stepwise contacting of the solid to the base, hereby largely preventing fragmentation. As a result, particle and crystal pore sizes may be obtained which are more similar to the starting solid. In addition to the superior physico-chemical properties, superior catalytic properties, and the enhanced filtration behaviour, this invention may enable to reduce the amount of organics required in order to preserve the microporosity, crystallinity, and acidity during the alkaline leaching.
As used herein, the term “Al in the framework” refers to tetrahedral coordinated Al. Within the examples on multiple occasions reference is made to the filtration time, defined as ‘tF’. It is to be understood that this quantity refers to the time it takes to separate a solid from 97 vol. % of the alkaline solution using standard Buchner filtration. More specifically, this refers to filtration of the solid suspension using a Buchner step up equipped with a paper filter (Whatman filter #4 or #5, 9 cm in diameter). The filtration time is affected by both the process conditions (reaction time, reaction temperature, solid-to-liquid ratio, amount of base, type of base, additives such as TPABr, conventional or inventive base treatment), the scale of the treatment, and the used filter (Whatman #4 or #5). Accordingly, these parameters are therefore in all examples given. Process time (tP) relates to cumulative time it takes to execute the alkaline treatment and the subsequent filtration. In the case of a multistep treatment, the total treatment and filtration time is complemented with the required drying step in between the filtration and subsequent alkaline treatment.
The properties of the solids may be assessed using nitrogen adsorption at 77 K as it is a well-established technique to quantify the intrinsic zeotypical properties (relevant for crystalline microporous solids), as well as the amount of mesoporous in the solid. The first descriptor that is derived from the nitrogen isotherm is the total surface area (SBET). The latter is obtained by application of the BET model, and gives an indication of the overall porosity (micropores and mesopores) of the solids. The intrinsic zeotypical properties can be examined using the microporosity (Vmicro), which is derived from application of the t-plot to the adsorption branch of the isotherm, preferably applied within the range 0.35-0.50 nm thickness. Since the active sites (Brønsted sites, described below) are located in the micropores, it is preferred that upon alkaline post-synthetic modification the micropore volume remains as close to the starting zeolite as possible.
Nitrogen-sorption measurements were executed at −196° C. with a Micromeritics TriStar 3000 instrument, controlled by TriStar 3000 software (Micromeritics) version 6.03. Prior to the sorption experiment, the samples were degassed overnight under a flow of N2 with heating to 300° C. (5° C. min−1). The t-plot method, as described in Microporous Mesoporous Mater. 2003, 60, 1-17, was used to distinguish between micro- and mesopores (thickness range=0.35-0.50 nm, using thickness equation from Harkins and Jura, and density conversion factor=0.0015468). To accurately compare the microporosity derived from the t-plot among solids, it is preferred that the same t-plot method and thickness range and thickness equation are used. For example, if the t-plot is applied in a narrow range at high relative pressures (for example at p/p0=0.30-0.35) the resulting microporosity can be an overestimation. The t-plot method simultaneously yields an external surface (referred to ‘Smeso’) which is used as an indication for the degree of secondary porosity.
For the pore size distribution, the BJH model, as also described in Microporous Mesoporous Mater. 2003, 60, 1-17 was applied to the adsorption branch of the isotherm. The total pore volume (Vpore) was determined at relative pressure (p/p0=0.98). The mesopore volume (Vmeso) is defined as Vmeso=Vpore−Vmicro. The occlusion or cavitation ratio is defined as the ratio of the slopes of the points measured at the adsorption- and the desorption-branch (slopeads/slopedes) between relative pressures p/p0 of 0.82 and 0.87 of the nitrogen isotherms. The further away the desorption branch deviates from the adsorption branch, the higher the ratio becomes. Therefore high hysteresis/occlusion can be related to a high cavitation ratio, which is unfavourable in catalytic applications. It is therefore desired that the cavitation ratio is as small as possible.
In the case the inorganic porous solids are crystalline, zeolites, SAPOs, AlPOs, the preservation of the intrinsic properties can be examined using X-ray diffraction (XRD). This technique results in a topology-specific reflection pattern. The relative crystallinity, indicative for the overall intrinsic zeotypical properties, can be assessed by integration of several characteristic peaks using methods such as described in ASTM D3906 (for faujasite zeolites) and ASTM 5758 (for ZSM-5 zeolites). It is preferred that the alkaline-treated sample displays a crystallinity as high as possible relative to the starting crystalline inorganic solid. In the case of faujasites the relative crystallinity is compared to industrial standard NaY zeolite provided by Zeolyst (supplier code ‘CBV 100’). In addition, the relative crystallinities of the zeolites are quantified by comparison to a NIST standard alumina (SRM 676). This is achieved by comparing the area of the peak at 25.7 degrees 2theta of the NIST standard to the area of the peak at 15.7 degrees 2theta for zeolites with FAU topology, or to the area of the peak at 7.7 degrees 2theta for zeolites with the BEA topology, or the area of the peaks in the range from 23.1 to 24.3 degrees 2theta for ZSM-5 zeolites. XRD is also a useful characterization technique as it enables to determine the unit cell size. Particularly in the case of faujasites, the unit cell size is relevant as it gives an indication of the composition (atomic Si/Al ratio) of the framework. The unit cell size is derived using established methods as specified in ASTM 3942. X-Ray diffraction was measured on a Siemens D5000 diffractometer with Bragg-Brentano geometry and Ni-filtered Cu Kα radiation (λ=0.1541 nm). Data were recorded in the range 5-50 degrees 2theta with an angular step size of 0.05 degrees and a counting time of 8 s per step.
Another method to monitor the influence of a post-synthetic treatment is by means of magic angle scanning nuclear magnetic resonance (MAS NMR) spectroscopy. This technique probes the coordination of the T-atoms (Al and Si). In the case of aluminium, it is generally assumed that zeolitic framework tetrahedrally-coordinated species occur in the range of 40 ppm to 80 ppm, whereas partly-framework pentahedrally-coordinated species occur in the 10 ppm to 40 ppm range, and extra-framework octahedrally-coordinated species occur in the range 10 ppm to −40 ppm (Angewandte Chemie, 1983, 22, 259-336). It is accordingly important that, to attain the highest degree of zeolitic properties during post-synthetic modifications, the relative amount of tetrahedrally-coordinated species are highest. In the case of silicon coordination, the MAS NMR technique enables to assess the number of Al atoms the average Si atom is coordinated with (Angewandte Chemie, 1983, 22, 259-336). This varies from 0 (no Al neighbours, indicated as ‘Si(0Al)’) to a full coordination of Al (4 Al neighbours, indicated as ‘Si(4Al)’). In the alkaline treatment of USY zeolites it is most favourable to maintain the highest amount of Si(0Al) species as in this manner the desired hydrothermal stability of the framework is preserved.
Experimental: 29Si and 27Al magic-angle spinning (MAS) NMR spectra were acquired on Bruker Avance III 400 and 700 MHz spectrometers operating at 9.4 and 16.4 T, respectively, and 29Si and 27Al Larmor frequencies of 139.1 and 182.4 MHz, respectively. All samples were packed into 4 mm (27Al) and 7 mm (29Si) ZrO2 rotors. 29Si MAS NMR spectra were recorded in a double resonance probe at a spinning rate of 5 kHz using a pulse width (45° flip angle) of 3.4 μs, corresponding to a radio-frequency (rf) field strength of ˜37 kHz. The recycle delay was set to 60 s and a number of scans between 500 and 1000 was employed in all samples. 27Al MAS NMR spectra were recorded in a double resonance probe at a spinning rate of 14 kHz. Quantitative spectra were obtained using a π/18 short rf pulse (˜0.3 μs) calibrated using an aqueous solution of Al(NO3)3, corresponding to an rf field strength of 104 kHz. The recycle delay was set to 1 s and a number of scans between 9 k and 15 k was employed in all samples. Chemical shifts are quoted in ppm from octakis(trimethylsiloxy)silsesquioxane (−109.68 ppm, for the farthest downfield frequency peak) and aqueous solution of Al(NO3)3 (0 ppm) for 29Si and 27Al, respectively.
The majority of applications of the inorganic porous solids described herein comprise acid-catalyzed conversions. Herein, the acid-site type and quantity is crucial. To quantitatively monitor the acidic properties of solids, a routinely-applied technique is the Fourier-transform infrared (FTIR) spectroscopy of pyridine adsorbed onto the solids. This method enables to quantify the number of strong Brønsted sites (B) and weaker Lewis acid sites (L) present within the solid. In catalytic applications of zeolites and SAPOs, particularly the amount of Brønsted acid sites, are key to their effective operation. Since the main goal of the modification by alkaline treatment is porous enhancement, it is imperative that particularly the Brønsted site density is maintained upon alkaline treatment. In addition, the Brønsted acidity can be measured using temperature programmed desorption of NH3-TPD.
Pyridine FTIR measurements were performed by using a Nicolet 6700 spectrometer equipped with a DTGS detector. Samples were pressed into self-supporting wafers and degassed at 400° C. for 1 h in vacuo before measurements. Brønsted and Lewis acid sites were analyzed by using a pyridine probe. After evacuation, the samples were subjected to 4-5 pulses of at least 25 mbar of pyridine at 50° C. for 1 min (until saturation), after which the system was heated to 150° C. in 40 min, followed by the acquisition of the spectra at the same temperature. The absorptions at 1550 and 1450 cm−1 corresponded to the amount of Brønsted and Lewis acid sites, respectively. The extinction coefficients were determined by Emeis, J. Catal. 1993, 141, 347-354.
NH3 temperature-programmed desorption (TPD) signals of the solids were attained using a custom set-up in which 100 mg of the sample was first pre-treated at 400° C. under He (20 cm3 min−1) for 1 h (ramp 10° C. min−1). Next 5% NH3 in He (20 cm3 min−1) was adsorbed at 200° C. for 30 min followed by purging with He for 30 min at the same temperature (20 cm3 min−1). The desorption was monitored on a Pfeiffer Omnistar quadrupole mass spectrometer in a range from 200-700° C. (10° C. min−1) under He flow (10 cm3 min−1).
The catalytic performance was monitored in the isomerization of α-pinene, as it represents a suitable model reaction in which both the function of the intrinsic zeotypical properties and that of the external surface is probed. In this reaction the activity (A) refers to the degree of conversion, while the productivity (P) is the yield of useful products (limonene, camphene, α-terpinene, γ-terpinene, terpinoline, p-cymene). The P/A ratio enables to compare selectivities: higher P/A values indicate lower amounts of unwanted side products such as cokes (polymers and oligomers of α-pinene). The value P/Vmeso relates the productivity to the secondary porosity. It is accordingly a measure for the efficiency of the secondary porosity.
Experimental catalysis: The isomerization reactions were carried out in a 50 cm3 Parr reactor with a sampling device at 150° C. under 6-8 bar of nitrogen with a stirring speed of 750 rpm. A mixture of substrate (20 g; a-pinene) and catalyst (0.1 g) was heated to 100° C., after which time the first liquid sample was taken. The reaction mixture was then further heated to 150° C. and more samples were taken 10, 30, and 60 min after the first sample. The samples were then analyzed on a gas chromatograph (HP 5890, Hewlett Packard) equipped with an HP1 column and a flame ionization detector (FID). Tetradecane was used as an external standard. Unidentified products were analyzed by GC-MS (6890N, Agilent Technologies). The activity of the samples was determined by using the slope of the linear part of the conversion of a-pinene versus the contact time graph.
Besides the physical chemical properties and associated catalytic performance, the recoverability of zeolites from aqueous solutions is a key descriptor to the economic viability of solids, especially those prepared (and modified) in aqueous solutions. Therefore, when applying post-synthetic modifications in aqueous solutions, such as alkaline treatment, it is imperative that, besides the desired physico-chemical enhancements, the particle size distribution is not negatively influenced. Thus far, the implication of alkaline treatments on the particle and crystal size distribution, and associated recoverability, are not known in the state of the art. The inventors have found that alkaline treatments on porous inorganic solids, such as zeolites, SAPOs, AlPOs, and ordered mesoporous materials such as MCM-41 and SBA-15, have a severe influence on the particle and crystal size of the inorganic solid. The alkaline treatments strongly lower the average particle and crystal size, complicating their recoverability. As a result, the filtration of inorganic porous solids using membrane-based techniques, such as Buchner set-ups, can take up to 100 times more time. The latter is economically rather unattractive and limits the commercial potential of alkaline-treated zeolites of the prior art.
Particle size measurements were performed by putting part of the suspension obtained after alkaline treatment in a standard polystyrene cuvette (2.5 ml) and subjecting them to dynamic light scattering (DLS) analysis. Accordingly, the supernatant of the centrifuged (15 min at 12,000 rpm) suspension was measured in polystyrene cuvettes on a 90Plus Particle Size Analyzer (Brookhaven) equipped with 659 nm laser, under a detection angle of 90°. Fluctuations in the scattered light intensity were correlated between 10 ms and 5 s. Correlation functions were analyzed with Igor Pro 6.2, using the Clementine package for modeling of decay kinetics based on the Maximum Entropy method. The decay time was converted to a hydrodynamic diameters using the Stokes-Einstein equation. The resulting criterion for size is expressed as the effective diameter (Deff), which represents a weighted average of the hydrodynamic diameter of the particles in the sample. These are calculated from the measured diffusion coefficient by DLS.
According to a first aspect, the invention relates to a method for preparing a treated inorganic porous solid wherein the method comprises a number of separate treatments (z) which are separated by a solid separation step, such as a filtration step, each of the z treatments comprising the steps of:
In addition to the superior physico-chemical properties, superior catalytic properties, and the enhanced filtration behaviour, this invention enables to reduce the amount of organics required in order to preserve the microporosity and crystallinity during the alkaline leaching.
The ratio mb,max/ms may be considered to be the maximum amount of base brought into contact with the solid at any time. In the state of the art (where y, x, z=1), the time of adding the base to the solvent during a treatment (tmb) is before the time of adding the inorganic porous solid (tms) to the solvent during the same treatment is added. Hence in the state of the art tmb<tms. The zeolite powder takes several minutes to be suspended in an aqueous solution. This implies that when the zeolite is added after the base (tmb<tms), the initially suspended zeolite fraction is exposed to the entire base quantity, whereby mb,max/ms>>mb,total/ms.
In some preferred embodiments, the maximum amount of base mb,max of mb(t) at any given time t in step c) is at most than 0.75*mb,total, preferably at most than 0.50*mb,total, preferably at most than 0.25*mb,total.
In some preferred embodiments, the inorganic porous solid comprises a molecular sieve, such as a zeolite or SAPO.
In some embodiments, the inorganic porous solid is a zeolitic material, preferably of structure type MWW, BEA, MFI, CHA, MOR, MTW, RUB, LEV, FER, MEL, RTH AEL, AFI, CHA, DON, EMT, CFI, CLO, TON, FER, ERI, MEL, MTW, MWW, HEU, EUO, RHO, LTL, LTA, MAZ, and most preferably to MOR, MFI, BEA, FAU topology, this zeolitic material having a mesoporosity after the treatment. This method or process can start from crystalline silicates, in particular those having zeolitic structure, which are subjected to an alkaline treatment and the new material with zeolitic properties and with mesoporosity is obtainable without high-speed commercial centrifuges or omitting filtration steps in between sequences of treatments. These zeolitic materials with mesoporosity may thereby be prepared in an ecologically and economically advantageous manner.
In some embodiments, this method or process can start from an amorphous silicate, such as fumed silica, and/or ordered silicas such as MCM-41 or SBA-15.
In some preferred embodiments, step a) comprises:
Preferably the solvent is water. In some embodiments, other solvents are used, such as alcohols (methanol, ethanol, or isopropanol). Typical solutions are in water with pH varying from at least 10 to at most 14, which relates to concentrations of NaOH of 0.0001 M to 1 M. The solid-to-liquid ratio (inorganic porous solid to liquid of base) can vary from very low 1 g L−1 to very high 100 g L−1, but in the examples is typically chosen to be typically 33 g L−1. The temperature may range from at least room temperature to at most 100° C., preferably from at least 50° C. to at most 70° C.
By adding the base to a suspension of zeolite, for example in water (tmb>tms), the non-instantaneous mixing/dissolution of the base implies that the initial value of mb,max/ms<mb,total/ms.
In some embodiments, the base is added in multiple discrete steps. The inorganic porous solid is not separated in between these steps. In some preferred embodiments, the method comprises a number of base additions per treatment (x) which are not separated by a solid separation step, and an amount of base added per addition (mb,i with i=1 . . . x), characterized in that x is not equal to 1, preferably wherein x is at least 2, preferably at least 3, preferably at least 4.
In some preferred embodiments, z is 1. This means that there is only one treatment, followed by a solid separation step, preferably a filtration step. During this treatment, the base is added in multiple steps (x≠1), or gradually. In some preferred embodiments, z is more than 1, for example at least 2, at least 3, or at least 4.
In some embodiments, the base is added gradually or continuously. The inorganic porous solid is not separated during this gradual addition. In some preferred embodiments, the rate of adding the amount of base over time is at most 3.0 mmol g−1 min−1, preferably at most 1.0 mmol g−1 min−1, preferably at most 0.5 mmol g−1 min−1.
The rate of adding the amount of base over time may depend on the used treatment. However, very good solids can be obtained by keeping this value below 3.0 mmol of base per gram of zeolite per minute (mmol g−1 min−1), preferably below 1.0 mmol g−1 min−1, and most preferably below 0.5 mmol g−1 min−1.
The base addition rate as mentioned in some of the examples may be scale sensitive as it is not normalized to the zeolite quantity. This could be normalized to a unit expressed in mol of base per gram of zeolite per hour. In some embodiments, for example as demonstrated in Example 17 (3.3 g zeolite in 90 ml solvent, to which 10 ml of 2 M NaOH is added using the syringe pump), the suitable range is 5-150 ml h−1, preferred range 10-50 ml h−1, and most preferred 15-30 ml h−1.
In some preferred embodiments, the base is continuously added to the inorganic porous solid during a time frame Δt, wherein the time frame Δt for adding the total amount of base mb,total is at least 15 s, preferably at least 30 s, for example at least 60 s, for example at least 2 min, for example at least 4 min, for example at least 8 min, for example at least 15 min, for example about 30 min. In some embodiments, Δt is at least 8 min and at most 60 min, preferably at least 15 min and at most 45 min, for example about 30 min.
In some preferred embodiments, the method is followed by a sequential acid treatment. This has the advantage that it enhances mesopore surface and volume, micropore volume, crystallinity, and acidity in a superior fashion than when applied in the state of the art.
In some embodiments, additives can be added, like the base in above-described fashion, in similar gradual fashion. Such additives can be metal salts, such as Al(NO3)3 and Ga(NO3)3, and organic compounds such as TPABr.
The impact of the invention, as compared to the state of the art, may depend on the nature of the samples. Among others, the largest influence may be the density of the zeolite's framework topology. In this case, a lower topological density yields a larger advantage. Therefore, the benefits on the zeolites with the FAU framework (density 13.3 T-atoms/1000 Å3), are larger compared to those obtained on zeolites with BEA framework (density 15.3 T-atoms/1000 Å3). Similarly, the benefits on BEA may therefore be larger compared to zeolites of the MFI framework (18.4 T-atoms/1000 Å3).
In addition, in the case of zeolites, the Si/Al ratio in the framework (and bulk) may have an influence. For example, in the case of preventing fragmentation and associated prolonged filtration times, the effect is optimal when the atomic Si/Al ratio is 5 or higher, preferably 10 or higher, and most preferably 20 and higher. This is demonstrated in Table A, where the filtration time of alkaline-treated USY zeolites increases rapidly with an increase of the Si/Al ratio of the starting zeolite.
In some embodiments, the invention comprises a process to perform alkaline treatment on inorganic porous solids yielding superior physico-chemical and catalytic properties, without a negative influence (or with only a limited influence) on the particle or crystal size. The application of the invention yields solids which may be easily recovered from the alkaline solution after treatment. In some embodiments, the process comprises the stepwise contacting of the solid to the base, hereby largely preventing fragmentation. As a result, particle and crystal pore sizes are obtained which are similar to the starting solid. In addition to the superior physico-chemical properties, superior catalytic properties, and the enhanced filtration behaviour, this invention enables to reduce the amount of organics required in order to preserve the microporosity and crystallinity during the alkaline leaching.
As illustrated by various examples, the inventive process can performed by multiple treatments of lower alkalinity, by dosing the base stepwise during the alkaline treatment, or by pumping a dilute alkaline solution through a solid-containing membrane. After such treatments, filtration time may be reduced substantially, thereby enhancing the overall productivity of the leaching process.
In some embodiments, afterwards, the reactor is quenched, the solid filtered off (using a lab-scale Buchner set-up), and washed.
In order to highlight the value of the invention, it is essential to describe the state of the art in the experimental procedures of alkaline leaching of solids. In the state of the art, a fixed amount of porous solid (typically 33 g L−1), is contacted with an aqueous solution with a fixed alkalinity. This is achieved by a direct immersion of the solid in a heated alkaline solution (typically using NaOH, at 0.24 mb,total/ms, at 65° C.), after which it is left to react (typically for 30 min).
In some embodiments, the alkaline treatment is executed exactly as in the state of the art, for example as described above, with the exception than the alkalinity is reduced, and the treatment is repeated to achieve the desired effect of the leaching. This could be, for example, that instead of one reaction 0.24 mb,total/ms, two reactions of 0.12 mb,total/ms are executed. The inventors have found that the filtration time of these two treatments combined can be significantly shorter than the filtration time following the single direct treatment at higher concentration. In
In some embodiments, the base is added, as solid or highly concentrated form, slowly during the course of the treatment. The inventors have found that this can be easily achieved using a pump, such as a syringe or peristaltic pump. On larger scales industrial pumps or solid dispersers may be used. This approach has as advantage that only one treatment is required, while acquiring the same significantly reduced filtration times. Particularly in this embodiment, the efficiency of the use of TPABr or DEA to preserve the intrinsic zeolitic properties is greatly enhanced. The invention goes beyond the state of the art based on several arguments. First, the solid is added prior to the addition of the base. Secondly (see
In some embodiments, the method comprises the stepwise contacting of a solid to a base using continuous configuration. In this configuration, the porous solid can be located on a membrane and the (dilute) basic solution is contacted to it by flowing (f) it through the solid-covered membrane (
In a second aspect, the invention relates to an inorganic porous solid obtainable by the method according to the first aspect, or any embodiment thereof. Preferred embodiments of these treated inorganic porous solids are as defined above.
In a third aspect, the invention relates to a zeolite with the faujasite topology, preferably prepared according to the method of the first aspect or any embodiment thereof, with a unit cell size ranging from 24.375 Å to 24.300 Å with a mesopore volume of at least 0.35 ml/g. Typically, the unit cell gets smaller when framework Al is removed. This type of zeolite is commonly referred to as an USY-I zeolite.
In some preferred embodiments, the zeolite according to the third aspect has a Brønsted acidity of at least 400 μmol g−1, as measured with pyridine; preferably 425 μmol g−1 or higher, and most preferably 500 μmol g−1 or higher, as measured with pyridine.
In some preferred embodiments, the zeolite according to the third aspect has a fraction of Al in the framework of at least 0.5, preferably 0.55 or higher, and most preferably 0.60 or higher.
In some preferred embodiments, the zeolite according to the third aspect has a crystallinity of at least 70%, preferably 75% or higher, and most preferably 80% or higher, relative to a standard NaY zeolite, and at least 80%, preferably 90% or higher, and most preferably 100% or higher, compared to NIST standard alumina (SRM 676).
In some preferred embodiments, the zeolite according to the third aspect has a microporosity of at least 0.18 ml g−1, preferably 0.21 ml g−1 or higher, and most preferably 0.24 ml g−1 and higher.
In a fourth aspect, the invention relates to a zeolite with the faujasite topology, preferably prepared according to the method of the first aspect or any embodiment thereof, with a unit cell size of at most 24.300 Å, preferably with a mesopore volume of at least 0.35 ml g−1. This type of zeolite is commonly referred to as an USY-III zeolite.
In some preferred embodiments, the zeolite according to the fourth aspect has a micropore volume of at least 0.21 ml g−1, preferably 0.22 ml g−1 or higher, and most preferably 0.23 ml g−1 and higher.
In some preferred embodiments, the zeolite according to the fourth aspect has a crystallinity of at least 95%, preferably 100% or higher, and most preferably 105% or higher, relative to a standard NaY zeolite, and at least 130%, preferably 137% or higher, and most preferably 142% or higher, compared to NIST standard alumina (SRM 676).
In some preferred embodiments, the zeolite according to the fourth aspect has a mesopore cavitation of at most 1.6, preferably 1.5 and lower, most preferably 1.4 and lower, as measured with nitrogen adsorption.
In some preferred embodiments, the zeolite according to the fourth aspect has a particle size Deff of at least 300 nm, preferably 350 nm and higher, most preferably 400 nm and higher.
In a fifth aspect, the invention relates to a zeolite with an MFI topology, preferably prepared according to the method of the first aspect or any embodiment thereof, with a molar Si/Al ratio of at most 400, with a mesopore volume of at least 0.30 ml g−1 and a crystallinity of at least 330%, preferably 340% and higher, and most preferably 350% and higher, compared to NIST standard alumina (SRM 676).
In an aspect, the invention relates to a zeolite with a BEA topology, preferably prepared according to the method of the first aspect or any embodiment thereof, with a mesopore volume of at least 0.50 ml g−1 and a crystallinity of at least 500%, preferably 515% and higher, and most preferably 530% and higher, compared to NIST standard alumina (SRM 676).
For industrial large-scale application, zeolite powders (as described in the examples) typically require to be transformed into technical catalysts. Technical catalysts are typically designed to provide the required mechanical strength and chemical stability to withstand demanding industrial catalytic unit operations. The transformation of a zeolite powder into a technical catalyst is preferably performed by mixing the zeolite with several other ingredients (such as fillers, pyrogens, binders, lubricants, etc.) and the subsequent shaping into macroscopic forms. The resulting technical catalysts can be multi-component bodies with sizes from the micrometres to the centimetre range.
In a sixth aspect, the invention relates to a method for preparing a technical catalyst, the method comprising the steps of:
The inventors have found that the solids as described above, particularly those of the second, third, fourth, and fifth aspects, as well as preferred embodiments thereof, are ideal intermediate compounds for the preparation of a technical catalyst as described above.
In a seventh aspect, the invention relates to the use of a treated inorganic porous solid according to any one of the aspects described herein or prepared in a method according to any one of the aspects, and embodiments thereof, in catalysis, adsorptive or ion exchange processes. Preferred embodiments of this use are as defined above.
Some embodiments of the invention are set forth below. These embodiments are also combinable with any of the embodiments described above.
In some embodiments the invention relates to a process of alkaline leaching of a porous solid whereby the method comprises a number of base additions per reaction (x), an amount of base added per addition (mb), a number of solid additions per reaction (y), an amount of solid added per addition (ms), a number of treatments (z), characterized in that x and z are not equal to 1, for example in that x, y, and z are not equal to 1.
In some embodiments, when x is equal to 1, z is 2 (or higher). In addition, x*mb*z may be adapted to an overall amount of base contacted with the porous solid, to ensure the desired effect of the leaching but to avoid fragmentation.
In some embodiments, the process is so designed by controlling y, z or x, preferably z or x, preferably x, so that although the porous solid is subjected to a same overall amount of base or that a same overall amount of base is contacted with the porous solid (which is preferred to ensure the desired effect of the leaching), the alkaline leaching is less drastic than subjecting the porous solid of 20-40 g L−1 in an aqueous solution contacted with a fixed alkalinity of 0.1 to 0.2 M NaOH, typically for about 20 to 40 min.
In some embodiments, the process is so designed that although the porous solid is subjected to a same overall amount of base by controlling y, z or x, preferably z or x, preferably x, the alkaline leaching is less drastic than subjecting porous solid of 20-40 g L−1 in an aqueous solution contacted with a fixed alkalinity of 0.1 to 0.2 M NaOH, typically for about 20 to 40 min. at a temperature of 45 to 85° C.
In some embodiments, the process is so designed that although the porous solid is subjected to a same overall amount of base by controlling y, z or x, preferably z or x, preferably x, so that no fragmentation of components of the porous solid occurs.
In some embodiments, the process is so designed that although the porous solid is subjected to a same overall amount of base by controlling y, z or x, preferably z or x, preferably x, so that basically no fragmentation of components of the porous solid occurs.
In some embodiments, the porous solid is crystalline and the process is so designed that although the porous solid is subjected to a same overall amount of base by controlling y, z or x preferably z or x, preferably x, basically no crystal fragmentation occurs.
In some embodiments, the process comprises alkaline leaching on porous solid at 5 to 60 g L−1, preferably 20 to 40 g L−1, and whereby the process comprises subjecting the porous solid to a treatment regime several reaction of mild conditions of NaOH at a temperature between 40 to 70° C., preferably a temperature between 60 to 75° C. and a reaction time of 10 to 50 min., preferably 20 to 40 min whereby the treatment regime comprises z treatments of mb amounts of NaOH to have the same amount of NaOH consumed as one treatment of 0.15 to 0.25 M NaOH.
In some embodiments, the porous solid is a porous silicate solid.
In some embodiments, the silicate solid is a material with a topology of the group consisting of MWW, BEA, MFI, CHA, MOR, MTW, RUB, LEV, FER, MEL, RTH AEL, AFI, CHA, DON, EMT, CFI, CLO, TON, FER, ERI, MEL, MTW, MWW, HEU, EUO, RHO, LTL, LTA and MAZ.
In some embodiments, the silicate solid is a material with a topology of the group consisting of MOR, MFI, BEA and FAU.
In some embodiments, the silicate solid is a porous crystalline silicate.
In some embodiments, the silicate solid is a porous crystalline silicate having zeolitic structure.
In some embodiments, the silicate solid is amorphous, such as fumed silica or silica gel.
In some embodiments, the porous solid is an amorphous alumino-silicate.
In some embodiments, the silicate solid is a porous ordered silicate (e.g. MCM-41 or SBA-15).
In some embodiments, the porous solid is an ordered alumino-silicate (e.g. MCM-41).
In some embodiments, the porous solid is a porous amorphous (silico)aluminophosphate.
In some embodiments, the porous solid is a porous crystalline (silico)aluminophosphate (e.g. AlPO-5, SAPO-11, SAPO-34).
In some preferred embodiments, the invention comprises any one the following numbered statements. These numbered statements may be combined with any other embodiment in the claims and the description. Reference to statement 1 in statements 2-43 may also be replaced by reference to the first aspect of the invention. Reference to statement 44 in statements 45-51 may also be replaced by reference to the second, third, fourth, and fifth aspect of the invention. References in statements 52-55 may also be replaced by reference to the seventh aspect of the invention.
The following comparative examples 1-15 are used to demonstrate the state of the art and serve as comparison highlighting the value of the invention. The starting zeolites were not dissolved and were not contacted with any base prior to executing the comparative examples.
The following examples are according to preferred embodiments of the invention. The starting zeolites were not dissolved and were not contacted with any base prior to executing the inventive examples.
aMesoporosity (Smeso) and microporosity (Vmicro) as measured by nitrogen adsorption.
bCrystallinity as measured by XRD,
cFiltration time (tF) following the alkaline treatment.
dProduced waste water during the alkaline treatment per gram of initial zeolite.
eProcess time (tP) relates to the cumulative time it takes to execute the alkaline treatment and the subsequent filtration. In the case of a multistep treatment, the total treatment and filtration time is complemented with the required drying step in between the filtration and subsequent alkaline treatment.
fBrønsted (B) and Lewis (L) acidity as measured with pyridine adsorption.
gActivity (A) and productivity (P) of the catalyst (after a standard ion exchange and calcination) in the conversion of α-pinene. The unit of A is gram of α-pinene converted per gram of catalyst per hour. The unit of P is gram of useful products (limonene, camphene, α-terpinene, γ-terpinene, terpinoline, p-cymene) formed per gram of catalysts per hour.
hP/A is a measure for the selectivity to desired products of the zeolite catalysts.
aPorosity, crystallinity, and acidity data were obtained from ACS Catalysis 2015, 5, 734.
bFiltration times were obtained by reproduction of the experiments from ACS Catalysis 2015, 5, 734 on a 100 ml scale, and filtration using a Buchner set-up with Whatman filter #5 paper (9 cm in diameter). The filtration time of the non-treated conventional zeolites was obtained by filtration of a suspension of 3.3 g of zeolite in 100 ml distilled water using a Buchner set-up with Whatman filter #5 paper (9 cm in diameter).
%
aBase treatments were performed accordingly to Example 34. All base-treated samples were washed afterwards using a standard acid treatment as defined in Example 34.
bNitrogen adsorption.
cXRD, compared the parent USY-I zeolite (‘parent’), to a NIST standard alumina (SRM 676) (‘NIST’), or a standard NaY (CBV 100 provided by Zeolyst) (‘NaY’).
dFTIR of pyridine adsorbed.
eNH3-TPD.
fProductivity of the catalyst (after a standard ion exchange and calcination) in the conversion of a-pinene, in gram of useful products (limonene, camphene, α-terpinene, γ-terpinene, terpinoline, p-cymene) formed per gram of catalysts per hour.
gThe value P/Vmeso relates the productivity to the secondary porosity. It is accordingly a measure for the efficiency of the secondary porosity.
hvalues in brackets indicate the change induced compared to the starting conventional USY-I zeolite.
Following novel materials were prepared using the methods according to embodiments of the invention. The properties of these materials are given in
For USY-I: Crystallinity (
aTetrahedral species (80 to 40 ppm), pentahedral (40 to 10 ppm), and octahedral (10 to −40 ppm).
bThe base treatment (mb, total/ms = 0.24 g g−1) was complemented with a standard acid wash as described in Example 34.
aSi(0Al) at −108 ppm, Si(1Al) at −102 ppm, Si(2Al) at −96 ppm, Si(3Al) at −92 ppm.
bThe base treatment (mb, total/ms = 0.24 g g−1) was complemented with a standard acid wash as described in Example 34.
Difference of the faujasites (USY): Among the available USY zeolites, the most critical difference is the framework Si/Al ratio. The latter is quite different compared to the bulk Si/Al ratio as measured by elemental analysis (due to the presence of extra-framework Si and Al species entrapped in the samples). The Si/Al ratio of the framework strongly dictates its acidity, its stability, and the type and nature of the applied post-synthetic protocol. As the Si/Al of the framework is hard to measure by elemental analysis, it is derived from the XRD pattern (using standardized methods specified by ASTM 3942). As the amount of Al in the framework make the zeolite framework expand, the amount of Al in the framework can be derived from evaluation of the unit cell size. The unit cell sizes of the parent materials are freely available from the zeolite supplier (Zeolyst). For USY-I (CBV 712) it is 24.35 Å, whereas for USY-III (CBV 760) it is 24.24 Å.
The new material USY-I can be uniquely described as:
The new material USY-III can be uniquely described as:
The new material MFI can be uniquely described as:
The new material BEA can be uniquely described as:
| Number | Date | Country | Kind |
|---|---|---|---|
| 1603487.8 | Feb 2016 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/054482 | 2/27/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62438693 | Dec 2016 | US |
