Patent Application
20180311651
A. Field of the Invention
The invention generally concerns a catalyst for chemical applications (e.g., hydrocarbon reforming reactions such as dry or steam reforming of methane). In particular, the invention concerns a catalyst that includes a bimetallic (M1M2) or trimetallic (M1M2M3) nanostructure, or oxides thereof, and a hollow zeolite support. The hollow space in the zeolite support includes the bi-metallic (M1M2) or tri-metallic (M1M2M3) nanostructure, or oxides thereof.
B. Description of Related Art
Synthesis gas or “syngas” is a gas mixture that includes carbon monoxide and hydrogen. Syngas is typically used as an intermediary gas to produce a wide range of various products, such as mixed alcohols, hydrogen, ammonia, i-C4 hydrocarbons, mixed alcohols, Fischer-Tropsch products (e.g., waxes, diesel fuels, olefins, gasoline, or the like), methanol, ethanol, aldehydes, alcohols, dimethoxy ethane, methyl tert-butyl ether, acetic acid, gas-to-liquids, butryaldehyde, or the like. Syngas can also be used as a direct fuel source, such as for internal combustible engines.
One of the more common methods of producing syngas is by oxidizing hydrocarbon gases such as methane. For instance, the controlled oxidation of methane can be carried out using carbon dioxide, water, oxygen, or a combination of such materials. For industrial scale applications, methane can be reformed into syngas by using steam, as shown in the following reaction:
CH4+H2O→CO+3H2
The ratio of CO/H2 obtained in steam reforming process is about 0.33. Many applications, however, require a CO/H2 of about 1.0. Such applications include production of aldehydes, alcohols, acetic anhydride, acetic acid, ethers, and ammonia. Therefore, the current solution is to remove excess H2 from the produced syngas using separation techniques, which can decrease efficiency while simultaneously increasing associated costs. Alternatively, the ratio of CO/H2 may be increased to about 1.0 by utilizing the dry reforming of methane reaction. In dry reforming of methane, methane is reacted with carbon dioxide or a mixture of carbon dioxide and oxygen as shown in the following equations:
CH4+CO2→2CO+2H2
2CH4+CO2+O2→3CO+3H2+H2O
Several metals, example Pt, Pd, Au, Ag, Ir, Ni, Co, Rh, Ru, La, Mg, Ca, Sr, Ba, Li, Na, K and Mn supported on different metal oxides, for example, Al2O3, SiO2, ZrO2, TiO2, CeO2, MgO, ZSM-5, MCM-41, MgAl2O4 have been used reforming processes. Of these catalysts, noble metal catalysts for CO2 reforming are based on Ni, Pt, Rh and Ru supported on Al2O3. One problem associated with dry reforming (using carbon dioxide) of methane is that current catalysts are prone to sintering, which reduces the active surface of the catalyst. Other problems associated with steam reforming and dry methane reforming reactions include growth of carbon residuals (e.g., encapsulating carbon, amorphous carbon, carbon whisker, filamentous carbon, and graphite) on the surface of the supported catalyst. Carbon growth can lead to deactivation of the catalyst due to blockage of catalytic sites (e.g., metal sites, coking), degradation of the catalyst, reactor plugging or combinations thereof.
Several recent disclosures have focused on improving the activity and life of reforming catalysts by attempting to reduce the particle size of the catalytic metal, use of promoters, or encapsulating the catalytic metal in a metal oxide by forming core@shell type structures. In some instances, single metal encapsulated hollow zeolites have been developed for use in various chemical applications. By way of example, Li et al., “Ultimate size control of encapsulated gold nanoparticles,” Chem. Commun. 2013, 49, describes encapsulating a single gold nanoparticle in a hollow zeolite. Still further, Li, “Metal nanoparticles encapsulated in membrane-like zeolite single crystals: application to selective catalysis,” Ph.D. Thesis, L'Universite Claude Bernard Lyon 1, HAL Id: tel-1163661, June 2015, describes the encapsulation of single metals such as cobalt, nickel, and copper in hollow zeolites for use as hydrogenation catalysts. Dai et al., “Hollow zeolite encapsulated Ni—Pt bimetals for sintering and coking resistant dry reforming of methane”, J. Materials of Chemistry A, 2015, 3, 16461-16468, describes encapsulating nickel—platinum nanoparticles in hollow zeolite for us in dry reforming of methane reactions.
Despite all of the currently available research on encapsulated metal hollow zeolite catalysts, many of the resulting catalysts include expensive noble metals, which can unfavorably impact costs for commercial applications.
A solution to the problems associated with the costs, deactivation, and degradation of reforming catalysts has been discovered. The solution lies in the production of alternatives to the Ni/Pt bimetallic catalysts, which can be expensive and can have limited efficiencies in hydrocarbon reforming reactions. In particular, the solution of the present invention concerns catalysts having bimetallic or trimetallic nanostructures encapsulated in a hollow zeolite structure that can be used in all types of hydrocarbon reforming reactions. As show in non-limiting embodiments in the Examples, NiCo bimetallic and NiRu bimetallic particles encapsulated in the hollow zeolite structure provide good stability and efficiency in hydrocarbon reforming reactions. Even further, the use of trimetallic nanostructures provides another class of catalysts that can be used in these types of reactions. Without wishing to be bound by theory, it is believed that certain combinations of bimetallic and trimetallic nanostructures that are encapsulated in the hollow zeolite structure offer increased catalytic stability and efficiency in producing syngas from either dry or steam reforming reactions of hydrocarbons (e.g., dry or steam reforming of methane). The size of the bimetallic or trimetallic particles are believed to be sufficiently small to prevent coking yet sufficiently large enough to be retained inside the hollow zeolite structure and prevent sintering with other metallic particles.
In a particular aspect of the present invention, there is disclosed a supported catalyst that can include a bimetallic (M1M2) or trimetallic (M1M2M3) nanostructure, or oxides thereof, encapsulated in a hollow zeolite support where M1, M2, and if present, M3, are different, with the proviso that if M1 is Ni, then M2 is not Pt in the bimetallic (M1M2) nanostructure. The catalyst can be used to catalyst reformation of hydrocarbons (e.g., CO2 reformation (dry reformation) or steam reformation of hydrocarbons (e.g., methane). The hydrocarbons can include 1, 2, 3, 4 6, 7, or 8 carbon atoms. In preferred aspects, the hydrocarbon can be methane. The supported catalyst includes at least two metals from Columns 1-16 of the Periodic Table. In a particular instance, when the catalyst includes a bimetallic nanostructure or oxide thereof, M1 is cobalt (Co) and M2 is ruthenium (Ru). Non-limiting examples of trimetallic catalysts can include (M1M2M3) nickel/cobalt/ruthenium (Ni/Co/Ru), nickel/cobalt/rhodium (Ni/Co/Rh), nickel/cobalt/platinum (Ni/Co/Pt), nickel/cobalt/cerium Ni/Co/Ce, or any combination thereof. The hollow zeolite support can include an exterior surface and an interior surface that defines and encloses a hollow space within the interior of the support and the bi-metallic (M1M2) or tri-metallic (M1M2M3) nanostructure, or oxides thereof, can be included in the hollow space. The hollow zeolite support can be made from any zeolite support (e.g., silicate-1, MFI, FAU, ITH BEA, MOR, LTA, MWW, CHA, MRE, MFE, or a VFI support). In one embodiment, MFI is used as the hollow support. In some aspects, the hollow zeolite support is 80 to 99.5 wt. % of the supported catalyst. The hollow space in the zeolite and the bi-metallic (M1M2) or tri-metallic (M1M2M3) nanostructure, or oxides thereof, included in the hollow space can be larger than the average pore size of the pores in the hollow zeolite support. The hollow space can include only one or a plurality of the bimetallic (M1M2) or trimetallic (M1M2M3) nanostructures, or oxides thereof. An average particle size of the bimetallic (M1M2) or trimetallic (M1M2M3) nanostructure, or oxides thereof, can range least 1 to 100 nm, preferably 1 to 30 nm, more preferably 3 to 15 nm, most preferably ≤10 nm with a size distribution having a standard deviation of ±20%. In certain aspects, the bimetallic (M1M2) or trimetallic (M1M2M3) nanostructures, or oxides thereof can be deposited on the interior surface of the hollow space. Additional bimetallic (M1M2) or trimetallic (M1M2M3) nanostructures, or oxides thereof can be deposited on the exterior surface. An amount of M1 and M2 are each 1 to 20 weight % of the total weight of the bimetallic nanostructure or M1, M2, and M3 are each 1 to 20 weight % of the total weight of the trimetallic nanostructure.
Methods of reforming hydrocarbons are disclosed. In one method, hydrogen (H2) and carbon monoxide (CO) can be produced by contacting a hydrocarbon feed stream with the catalyst described above in the presence of carbon dioxide (CO2) or H2O. Coke formation on the supported nanostructure catalyst is substantially or completely inhibited. In some embodiments, the reactant stream can include methane and CO2, methane, water and, optionally O2, or methane, CO2, and water. Reformation reaction conditions can include a temperature of about 700° C. to about 950° C., a pressure of about 0.1 MPa to 2.5 MPa, and a gas hourly space velocity (GHSV) ranging from about 500 to about 100,000 h−1.
In another aspect, a method to make the supported catalyst described above can include (a) obtaining a zeolite support, (b) obtaining a first suspension by suspending the zeolite support in an aqueous solution having a M1 precursor material, a M2 precursor material, and optionally a M3 precursor material for a sufficient period of time to impregnate the support with the precursor material and drying the first suspension to obtain an impregnated support, (c) obtaining a second suspension by suspending the impregnated support from step (b) in an aqueous solution that includes a templating agent and heat treating the suspension to obtain a templated support, and (d) calcining the templated support to obtain the supported catalyst described above. Drying the first suspension to obtain the impregnated support in step (b) can include subjecting the first suspension to a temperature of 30° C. to 100° C., preferably 40° C. to 60° C., for 4 to 24 hours, preferably 6 to 12 hours. The calcining step (d) can include subjecting the templated support to a temperature of 350° C. to 550° C., preferably 400° C. to 500° C., for 3 to 10 hours, preferably 4 to 8 hours. M1, M2, and M3 precursor materials can each be a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, or combination thereof. Tetrapropylammonium hydroxide (TPAOH) can be used as the templating agent. The calcined catalyst can be subjecting to reducing conditions to convert the metal oxide to the metal having a zero valence.
Systems for producing a chemical product are also described. A system can include (a) an inlet for a reactant feed, (b) a reaction zone (e.g., a continuous flow reactor selected from a fixed-bed reactor, a fluidized reactor, or a moving bed reactor) that is configured to be in fluid communication with the inlet, and (c) an outlet configured to be in fluid communication with the reaction zone and configured to remove a product stream from the reaction zone. The reaction zone can include the supported catalyst of the present invention. The reactant feed can include C1 to C8 hydrocarbons (e.g., methane, C1 to C3 hydrocarbons, C1 to C4 hydrocarbons, or the like) and an oxidant (e.g., carbon dioxide, oxygen or air), water or both.
In the context of the present invention 35 embodiments are described. Embodiment 1 is a supported catalyst that includes a bimetallic (M1M2) or trimetallic (M1M2M3) nanostructure, or oxides thereof, and a hollow zeolite support, wherein: (a) M1, M2, and if present, M3, are different, with the proviso that if M1 is Ni, then M2 is not platinum (Pt) in the bimetallic (M1M2) nanostructure; and (b) the hollow zeolite support comprises an exterior surface and an interior surface that defines and encloses a hollow space within the interior of the support, wherein the bi-metallic (M1M2) or tri-metallic (M1M2M3) nanostructure, or oxides thereof, is comprised in the hollow space. Embodiment 2 is the supported catalyst of embodiment 1, wherein the hollow zeolite support is a silicate-1, MFI, FAU, ITH BEA, MOR, LTA, MWW, CHA, MRE, MFE, or a VFI support, preferably an MFI support. Embodiment 3 is the supported catalyst of any one of embodiments 1 to 2, wherein the nanostructure is a bimetallic (M1M2) nanoparticle. Embodiment 4 is the supported catalyst of embodiment 3, wherein M1 is Ni and M2 is either Co or Ru. Embodiment 5 is the supported catalyst of embodiment 4, wherein M1 and M2 are each 45 to 55 molar % of the total moles of the bimetallic nanostructure. Embodiment 6 is the supported catalyst of embodiment 5, wherein the hollow zeolite support is 80 to 99.5 wt. % of the supported catalyst. Embodiment 7 is the supported catalyst of any one of embodiments 1 to 6, wherein the hollow space comprises only one bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof. Embodiment 8 is the supported catalyst of any one of embodiments 1 to 6, wherein the hollow space comprises a plurality of the bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticles, or oxides thereof. Embodiment 9 is the supported catalyst of any one of embodiments 1 to 8, wherein the bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof, is deposited on the interior surface. Embodiment 10 is the supported catalyst of any one of embodiments 1 to 9, further comprising at least one additional bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof, deposited on the exterior surface. Embodiment 11 is the supported catalyst of any one of embodiments 1 to 10, wherein the size of the hollow space and the bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof, are larger than the average pore size of the pores in the hollow zeolite support. Embodiment 12 is the supported catalyst of embodiment 11, wherein the average particle size of the bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof, is 1 to 100 nm, preferably 1 to 30 nm, more preferably 3 to 15 nm, most preferably ≤10 with a size distribution having a standard deviation of ±20%. Embodiment 13 is the supported catalyst of any one of embodiments 1 to 4 and 7 to 12, wherein M1 and M2 are each 1 to 20 weight % of the total weight of the bimetallic nanostructure or wherein M1, M2, and M3 are each 1 to 20 weight % of the total weight of the trimetallic nanostructure. Embodiment 14 is the supported catalyst of any one of embodiments 1 to 4 and 7 to 13, wherein the hollow zeolite support is 80 to 99.5 wt. % of the supported catalyst. Embodiment 15 is the supported catalyst of any one of embodiments 1 to 14, wherein the catalyst is configured to catalyze a hydrocarbon reformation reaction. Embodiment 16 is the supported catalyst of embodiment 15, wherein the reformation reaction is a dry reformation of methane reaction or a steam reformation reaction. Embodiment 17 is the supported catalyst of embodiment 15, wherein the reformation reaction of methane reaction is a steam reformation reaction.
Embodiment 18 is a method of producing H2 and CO that includes contacting a reactant gas stream that includes hydrocarbons and CO2 or H2O with the supported catalyst of any one of embodiments 1 to 17 sufficient to produce a product gas stream comprising H2 and CO. Embodiment 19 is the method of embodiment 18, wherein coke formation on the supported nanostructure catalyst is substantially or completely inhibited. Embodiment 20 is the method of any one of embodiments 18 to 19, wherein the reactant gas stream comprises C1 to C8 hydrocarbons, preferably methane, and CO2. Embodiment 21 is the method of any one of embodiments 18 to 19, wherein the reactant gas stream comprises C1 to C8 hydrocarbons, preferably methane, and H2O and optionally O2. Embodiment 22 is the method of any one of embodiments 18 to 19, wherein the reactant gas stream comprises C1 to C8 hydrocarbons, preferably methane, and H2O and CO2 and H2O. Embodiment 23 is the method of any one of embodiments 18 to 22, wherein the reaction conditions include a temperature of about 700° C. to about 950° C., a pressure of about 0.1 MPa to 2.5 MPa, and a gas hourly space velocity (GHSV) ranging from about 500 to about 100,000 h−1.
Embodiment 24 is a method of making the supported catalyst of any one of embodiments 1 to 17. The method can include: (a) obtaining a zeolite support; (b) obtaining a first suspension by suspending the zeolite support in an aqueous solution having a M1 precursor material, a M2 precursor material, and optionally a M3 precursor material for a sufficient period of time to impregnate the support with the precursor material and drying the first suspension to obtain an impregnated support; (c) obtaining a second suspension by suspending the impregnated support from step (b) in an aqueous solution comprising a templating agent and thermally treating the suspension to obtain a templated support; and (d) calcining the templated support to obtain the supported catalyst of any one of embodiments 1 to 17. Embodiment 25 is the method of embodiment 24, wherein drying the first suspension to obtain the impregnated support in step (b) comprises subjecting the first suspension to a temperature of 30° C. to 100° C., preferably 40° C. to 60° C., for 4 to 24 hours, preferably 6 to 12 hours. Embodiment 26 is the method of any one of embodiments 24 to 25, wherein thermally treating the second suspension to obtain the templated support comprises subjecting the second suspension to a temperature of 100° C. to 250° C., preferably 150° C. to 200° C., for 12 to 36 hours, preferably 18 to 30 hours. Embodiment 27 is the method of any one of embodiments 24 to 26, wherein calcining step (d) comprises subjecting the templated support to a temperature of 350° C. to 550° C., preferably 400° C. to 500° C., for 3 to 10 hours, preferably 4 to 8 hours. Embodiment 28 is the method of any one of embodiments 24 to 27, wherein the M1, M2, and M3 precursor materials are each a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, or combination thereof. Embodiment 29 is the method of any one of embodiments 24 to 27, wherein the templating agent is tetrapropylammonium hydroxide (TPAOH).
Embodiment 30 is a system for producing a chemical product. The system can include: (a) an inlet for a reactant feed; (b) a reaction zone that is configured to be in fluid communication with the inlet, wherein the reaction zone comprises the supported catalyst of any one of embodiments 1 to 17; and (c) an outlet configured to be in fluid communication with the reaction zone and configured to remove a product stream from the reaction zone. Embodiment 31 is the system of embodiment 30, wherein the reaction zone is a continuous flow reactor selected from a fixed-bed reactor, a fluidized reactor, or a moving bed reactor. Embodiment 32 is the system of any one of embodiments 30 to 31, wherein the reactant feed is a gas stream comprising CH4 and CO2. Embodiment 33 is the system of any one of embodiments 30 to 31, wherein the reactant feed is a gas stream comprising CH4, CO2, and H2O. Embodiment 34 is the system of any one of embodiments 30 to 31, wherein the reactant feed is a gas stream comprising CH4 and H2O and optionally O2. Embodiment 35 is the system of any one of claims 30 to 34, wherein the product stream is a gas stream comprising H2 and CO.
The following includes definitions of various terms and phrases used throughout this specification.
“Nanostructure” refers to an object or material in which at least one dimension of the object or material is equal to or less than 1000 nm (e.g., one dimension is 1 to 1000 nm in size). In a particular aspect, the nanostructure includes at least two dimensions that are equal to or less than 1000 nm (e.g., a first dimension is 1 to 1000 nm in size and a second dimension is 1 to 1000 nm in size). In another aspect, the nanostructure includes three dimensions that are equal to or less than 1000 nm (e.g., a first dimension is 1 to 1000 nm in size, a second dimension is 1 to 1000 nm in size, and a third dimension is 1 to 1000 nm in size). The shape of the nanostructure can be of a wire, a particle (e.g., having a substantially spherical shape), a rod, a tetrapod, a hyper-branched structure, a tube, a cube, or mixtures thereof “Nanostructures” include particles having an average diameter size of 1 to 1000 nanometers. In a particular instance, the nanostructure is a nanoparticle.
The term “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.
The term “substantially” and its variations are defined to include to ranges within 10%, within 5%, within 1%, or within 0.5%.
The terms “inhibiting” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.
The term “effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.
The use of the words “a” or “an” when used in conjunction with any of the terms “comprising”, “including”, “containing”, or “having” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”
The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
The catalysts of the present invention can “comprise,” “consist essentially of,” or “consist of” particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase “consisting essentially of,” in one non-limiting aspect, a basic and novel characteristic of the catalysts of the present invention are (1) the use of bimetallic or trimetallic nanostructures that are encapsulated in a hollow zeolite structure and (2) their use in catalyzing hydrocarbon reforming reactions.
Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.
Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale.
The currently available commercial catalysts used to reform hydrocarbons into syngas are prone to growth of carbon residuals (e.g., coke and carbon whiskers) and sintering which can lead to inefficient catalyst performance and ultimately failure of the catalyst after relatively short periods of use. This can lead to inefficient syngas production as well as increased costs associated with its production. A discovery has been made that avoids problems associated with deactivation of reforming catalysts and the expense of using platinum or Ni—Pt catalysts. The catalyst is based on encapsulating a bimetallic (M1M2) or a trimetallic (M1M2M3) nanostructure in a hollow space of a zeolite. Notably, the catalyst does not rely on the presence of Pt such as Ni—Pt nanostructures. The catalyst design allows for low loading of less expensive catalytic metals and provides catalytic activity at lower temperatures (e.g., 650° C.). The nanostructure used in the catalyst can be selected for a desired result (e.g., catalytic metals can be included in the hollow to catalyze a given reformation reaction). The method of making the catalyst allows for creation of a hollow space in the zeolite and subsequent encapsulation of the metal nanostructure in the hollow zeolite. The method also allows control of the size the metal nanostructure. Without wishing to be bound by theory it is believed that because the metal nanostructure size is larger than the pore size of the zeolite, the metal nanostructure cannot diffuse out of the zeolite so they remain inside the hollow space of the zeolite created. Thus, the particle cannot grow or sinter, and hence size is maintained (i.e., sintering is prevented or inhibited). Moreover, because the size of the metal nanostructure is reduced, the formation of coke can be inhibited. Furthermore, the methods used to prepare the catalysts of the present invention allow tuning of the size of the bimetallic or trimetallic nanostructures as well as the type of metals that can be used. Further, the thickness of the hollow zeolite shell can also be tuned as desired.
These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.
The metal nanostructure/hollow zeolite structure of the present invention includes a metal nanostructure contained within a hollow space that is present in the zeolite.
1. Bimetallic or Trimetallic Nanostructure
Nanostructure(s) 14 can include one or more two or more active (catalytic) metals to promote the reforming of methane to carbon dioxide. The nanostructure(s) 14 can include one or more metals from Columns 1-16 of the Periodic Table (Groups IA, IIA, IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, IIB, IIIA, IVA, VA or VIA of the Chemical Abstracts Periodic Table). Non-limiting examples of the active metals include nickel (Ni), rhodium (Rh), ruthenium (Re), iridium (Ir), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), cobalt (Co), manganese (Mn), copper (Cu), or any combination thereof, preferably combinations of nickel, cobalt and ruthenium (e.g., Ni—Co or Ni—Ru). The metals can be obtained from metal precursor compounds. For example, the metals can be obtained as a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, metal complex, or any combination thereof. Examples of metal precursor compounds include, nickel nitrate hexahydrate, nickel chloride, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt phosphate hydrate, or ruthenium chloride, diammonium hexachorouthenate, hexammineruthenium trichloride, pentaammineruthenium dichloride, or the like. These metals or metal compounds can be purchased from any chemical supplier such as Sigma-Aldrich (St. Louis, Mo., USA), Alfa-Aeaser (Ward Hill, Mass., USA), and Strem Chemicals (Newburyport, Mass., USA).
The amount of nanostructure catalyst depends, inter alia, on the use of the catalysts (e.g., steam reforming or dry reforming of hydrocarbons). In some embodiments, the amount of catalytic metal present in the particle(s) in the hollow ranges from 0.01 to 100 parts by weight of catalyst per 100 parts by weight of catalyst, from 0.01 to 5 parts by weight of catalyst per 100 parts by weight of catalyst. M1 and M2 are each 1 to 20 weight % of the total weight of the bimetallic nanostructure or wherein M1, M2, and M3 are each 1 to 20 weight % of the total weight of the trimetallic nanostructure. A molar amount of each metal (e.g., M1 and M2 or M1, M2, and M3) in the nanostructure 14 ranges from 1 to 95 molar %, or 10 to 80 molar %, 50 to 70 molar % of the total moles of the bimetallic nanostructure. An average particle size of the bimetallic (M1M2) or trimetallic (M1M2M3) nanoparticle, or oxides thereof, is 1 to 100 nm, preferably 1 to 30 nm, more preferably 0.7 to 10 nm, most preferably ≤10 nm with a size distribution having a standard deviation of ±20%.
2. Zeolite Material
The zeolite shell 12 can be any porous zeolite or zeolite-like material. Zeolites belong to a broader material category known as “molecular sieves” and are often referred as such. Zeolites have uniform, molecular-sized pores, and can be separated based on their size, shape and polarity. For example, zeolites may have pore sizes ranging from about 0.3 nm to about 1 nm. The crystalline structure of zeolites can provide good mechanical properties and good thermal and chemical stability. The zeolite material can be a naturally occurring zeolite, a synthetic zeolite, a zeolite that have other materials in the zeolite framework (e.g., phosphorous), or combinations thereof. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) may be carried out to determine the properties of zeolite materials, including their crystallinity, size and morphology. The network of such zeolites is made up of SiO4 and AlO4 tetrahedra which are joined via shared oxygen bridges. An overview of the known structures may be found, for example, in W. M. Meier, D. H. Olson and Ch. Baerlocher, “Atlas of Zeolite Structure Types”, Elsevier, 5th edition, Amsterdam 2001. Non-limiting examples of zeolites include ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ATN, ATO, ATS, ATT, ATV, AWO, AWW, *BEA, BIK, BOG, BPH, BRE, CAN, CAS, CFI, CGF, CGS, CHA, CHI, -CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, EUO, *EWT, FAU, FER, GIS, GME, GOO, HEU, IFR, ISV, ITE, ITH, ITG, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MSO, MTF, MTN, MTT, MTW, MWW, NAT, NES, NON, OFF, OSI, PAR, PAU, PHI, RHO, RON, RSN, RTE, RTH, RUT, SAO, SAT, SBE, SBS, SBT, SFF, SGT, SOD, STF, STI, STT, TER, THO, TON, TSC, VET, VFI, VNI, VSV, WIE, WEN, YUG and ZON structures and mixed structures of two or more of the abovementioned structures. In some embodiments, the zeolite includes phosphorous to form a AIPOx structure. Non-limiting examples of AIPOx zeolites include AABW, AACO, AAEI, AAEL, AAEN, AAET, AAFG, AAFI, AAFN, AAFO, AAFR, AAFS, AAFT, AAFX, AAFY, AAHT, AANA, AAPC, AAPD, AAST, AATN, AATO, AATS, AATT, AATV, AAWO, AAWW, ABEA, ABIK, ABOG, ABPH, ABRE, ACAN, ACAS, ACFI, ACGF, ACGS, ACHA, ACHI, A-CLO, ACON, ACZP, ADAC, ADDR, ADFO, ADFT, ADOH, ADON, AEAB, AEDI, AEMT, AEPI, AERI, AESV, AEUO, A*EWT, AFAU, AFER, AGIS, AGME, AGOO, AHEU, AIFR, AISV, AITE, AITH, AITG, AJBW, AKFI, ALAU, ALEV, ALIO, ALOS, ALOV, ALTA, ALTL, ALTN, AMAZ, AMEI, AMEL, AMEP, AMER, AMFI, AMFS, AMON, AMOR, AMSO, AMTF, AMTN, AMTT, AMTW, AMWW, ANAT, ANES, ANON, AOFF, AOSI, APAR, APAU, APHI, ARHO, ARON, ARSN, ARTE, ARTH, ARUT, ASAO, ASAT, ASBE, ASBS, ASBT, ASFF, ASGT, ASOD, ASTF, ASTI, ASTT, ATER, ATHO, ATON, ATSC, AVET, AVFI, AVNI, AVSV, AWIE, AWEN, AYUG and AZON structures and mixed structures of two or more of the abovementioned structures. In particular embodiments, the zeolite is a porous zeolite in pure silica (Si/Al=∞) form or with a small amount of Al, for example, MFI, MEL, ITH, MOR, MWW or BEA framework type zeolites. Non-limiting examples of specific zeolites include L-zeolite, X-zeolite, Y-zeolite, omega zeolite, beta zeolite, silicate-1, TS-1, beta, ZSM-4, ZSM-5, ZSM-10, ZSM-12, ZSM-20, REY, USY, RE-USY, LZ-210, LZ-20-A, LZ-20-M, LZ-20-T, SSZ-24, ZZA-26, SSZ-31, SSZ-33, SSZ-35, SSZ-37, SSZ-41, SSZ-42, SSZ-44, MCM-58, mordenite, faujasite, or combinations thereof. Zeolites may be obtained from a commercial manufacturer such as Zeolyst (Valley Forge, Pa., U.S.A.).
Catalytic materials exist in various forms and their preparation can involve multiple steps. The catalysts can be prepared by processes known to those having ordinary skill in the art, for example the catalyst can be prepared by any one of the methods comprising liquid-liquid blending, solid-solid blending, or liquid-solid blending (i.e any of precipitation, co-precipitation, impregnation, complexation, gelation, crystallization, microemulsion, sol-gel, solvothermal, dissolution-recrystallization, hydrothermal, sonochemical, or combinations thereof).
Also disclosed is a method of producing hydrogen and carbon monoxide from hydrocarbons under reforming conditions to produce hydrogen (H2) and carbon monoxide (CO). Reforming includes steam reforming, partial oxidation of hydrocarbon reactions, dry reforming and any combination thereof. Reformation conditions can include contacting the catalyst material 10 with a hydrocarbon feed stream in the presence of an oxidant (e.g., carbon dioxide (CO2), oxygen (O2), oxygen enriched air, or any combination thereof) water (H2O), or both. The water can be in the form of high or low pressure steam. The method includes contacting a reactant gas mixture of a hydrocarbon and oxidant with any one of the supported catalyst materials 10 discussed above and/or throughout this specification under sufficient conditions to produce hydrogen and carbon monoxide at a ratio of 0.35 or greater, from 0.35 to 0.95, or from 0.6 to 0.9. Such conditions sufficient to produce the gaseous mixture can include a temperature range of 600° C. to 950° C. from 750° C. to 950° C. or from 750° C. to 850° C. or from 600° C., 625° C., 650° C., 675° C., 700° C., 725° C., 750° C., 775° C., 800° C., to 900° C., or any value there between and a pressure range of about 1 bara, and/or a gas hourly space velocity (GHSV) ranging from 1,000 to 100,000 h−1. In particular instances, the hydrocarbon includes methane and the oxidant is carbon dioxide. In other aspects, the oxidant is a mixture of carbon dioxide and oxygen. In certain aspects, the carbon formation or coking is reduced or does not occur on the catalyst material 10 and/or sintering is reduced or does not occur on the catalyst material 10. In particular instances, carbon formation or coking and/or sintering is reduced or does not occur when the catalyst 10 is subjected to temperatures at a range of greater than 700° C. or 800° C. or a range from 725° C., 750° C., 775° C., 800° C., 900° C., to 950° C. In particular instances, the range can be from 700° C. to 950° C. or from 750° C. to 900° C.
In instances when the produced catalytic material is used in dry reforming methane reactions, the carbon dioxide in the gaseous feed mixture can be obtained from various sources. In one non-limiting instance, the carbon dioxide can be obtained from a waste or recycle gas stream (e.g. from a plant on the same site, like for example from ammonia synthesis) or after recovering the carbon dioxide from a gas stream. A benefit of recycling such carbon dioxide as starting material in the process of the invention is that it can reduce the amount of carbon dioxide emitted to the atmosphere (e.g., from a chemical production site). The hydrogen in the feed may also originate from various sources, including streams coming from other chemical processes, like ethane cracking, methanol synthesis, or conversion of methane to aromatics. The gaseous feed mixture comprising carbon dioxide and hydrogen used in the process of the invention may further contain other gases, provided that these do not negatively affect the reaction. Examples of such other gases include oxygen and nitrogen. The hydrocarbon material used in the reaction can be methane. The resulting syngas can then be used in additional downstream reaction schemes to create additional products. Such examples include chemical products such as methanol production, olefin synthesis (e.g., via Fischer-Tropsch reaction), aromatics production, carbonylation of methanol, carbonylation of olefins, the reduction of iron oxide in steel production, or the like.
The reactant gas mixture can include natural gas, liquefied petroleum gas comprising C2-C5 hydrocarbons, C6+ heavy hydrocarbons (e.g., C6 to C24 hydrocarbons such as diesel fuel, jet fuel, gasoline, tars, kerosene, or the like), oxygenated hydrocarbons, and/or biodiesel, alcohols, or dimethyl ether. In particular instances, the reactant gas mixture has an overall oxygen to carbon atomic ratio equal to or greater than 0.9.
The method can further include isolating and/or storing the produced gaseous mixture. The method can also include separating hydrogen from the produced gaseous mixture (such as by passing the produced gaseous mixture through a hydrogen selective membrane to produce a hydrogen permeate). The method can include separating carbon monoxide from the produced gaseous mixture (such as passing the produced gaseous mixture through a carbon monoxide selective membrane to produce a carbon monoxide permeate).
The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.
Silicalite-1 is obtained by mixing tetraethylorthosilicate (TEOS, 98% purity, Sigma-Aldrich®, USA) and tetrapropylammonium hydroxide (TPA(OH), 1.0 M, in H2O, Sigma-Aldrich®, USA) with water. The gel composition is: SiO2:0.4 TPA(OH):35H2O. Then, the mixture is transferred into a Teflon-lined autoclave and heated at 170° C. under static condition for 3 days. The solid was recovery by centrifugation and washed with water, this operation was repeated 3 times. The resulting solid was dried overnight at 110° C. and then calcined at 525° C. in air for 12 h.
Silicalite-1 from Example 1 was impregnated with aqueous solution of Ni(NO3)2.6H2O (Sigma-Aldrich®, USA) to produce 1.8 wt % of Ni or 5.5 wt. % or Ni on the silicalite-1. The suspension was dried at 50° C. under air over the night. The impregnated silicalite-1 (1 g) was suspended with an aqueous TPA(OH) solution (4.15 in 3.33 mL of H2O). The mixture was transferred into a Teflon-lined autoclave and heated at 170° C. under static conditions for 24 h. Finally, the 1.8NiHZ was calcined in air at 450° C. for 6 h. Table 1 lists the compositions of the samples.
Silicalite-1 from Example 1 was impregnated silicalite-1 was impregnated with aqueous solution of Ni(NO3)2.6H2O (Sigma-Aldrich®, USA) and Co(NO3)2.6H2O (Aldrich) or RuCl3×H2O (Aldrich) to produce 5.5 wt % of NiM2 (NiCo or NiRu) on the silicalite-1 in a 50/50 mole ratio. The suspension was dried at 50° C. under air over the night. The impregnated silicalite-1 (1 g) was suspended with an aqueous TPA(OH) solution (4.15 in 3.33 mL of H2O). The mixture is transferred into Teflon-lined autoclave and heated at 170° C. under static conditions for 24 h. Finally, the NiCo/HZ is calcined in air at 450° C. for 6 h. Table 1 lists the compositions of the samples.
Isothermal Analysis.
Nitrogen Isotherms of the HZ-1 and silicate-1 using a ASAP 2020 Micromeritics® instrument (Micromeritics®, USA) were obtained.
Transmission Electron Microscopy (TEM).
TEM analysis was performed on comparative sample 2 and inventive catalyst samples 3 and 4.
The catalyst (60 g) from Examples 1-3, Table 1, were tested at three 650° C., 750° C., and 800° C. at a pressure of 5 bara, and a gas hourly space velocity (GSHV) of 73,000 h−1 for a gas composition of 10% Argon/5% CO2/45% methane for 30 hours of operation. The reactor flow was 50 cc.min−1.
Even at 850° C., the comparative samples 1 and 2, 1.8 wt. % Ni/HZ and 5.5 wt. % Ni/HZ, did not show any conversion. However, from the H2/CO ratio,
The H2/CO ratio obtained from the NiRu/HZ was greater than 0.5 (See,
This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/248,665, filed Oct. 30, 2015, which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2016/056478 | 10/27/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62248665 | Oct 2015 | US |
