USE OF HOLLOW ZEOLITES DOPED WITH BIMETALLIC OR TRIMETALLIC PARTICLES FOR HYDROCARBON REFORMING REACTIONS

Abstract

Catalysts useful for hydrocarbon reforming reactions are described. A catalyst can include 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.

Claims

1. A supported catalyst comprising a bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanostructure, or oxides thereof, and a hollow zeolite support, wherein: (a) M.sup.1, M.sup.2, and if present, M.sup.3, are different, with the proviso that if M.sup.1 is Ni, then M.sup.2 is not platinum (Pt) in the bimetallic (M.sup.1M.sup.2) 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 (M.sup.1M.sup.2) or tri-metallic (M.sup.1M.sup.2M.sup.3) nanostructure, or oxides thereof, is comprised in the hollow space.

2. The supported catalyst of claim 1, wherein the hollow zeolite support is a silicate-1, MFI, FAU, ITH BEA, MOR, LTA, MWW, CHA, MRE, MFE, or a VFI support.

3. The supported catalyst of claim 1, wherein the nanostructure is a bimetallic (M.sup.1M.sup.2) nanoparticle.

4. The supported catalyst of claim 3, wherein M.sup.1 is Ni and M.sup.2 is either Co or Ru.

5. The supported catalyst of claim 4, wherein M.sup.1 and M.sup.2 are each 45 to 55 molar % of the total moles of the bimetallic nanostructure.

6. The supported catalyst of claim 5, wherein the hollow zeolite support is 80 to 99.5 wt. % of the supported catalyst.

7. The supported catalyst of claim 1, wherein the hollow space comprises only one bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanoparticle, or oxides thereof, or the hollow space comprises a plurality of the bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanoparticles, or oxides thereof.

8. The supported catalyst of claim 1, wherein the bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanoparticle, or oxides thereof, is deposited on the interior surface of the hollow zeolite support.

9. The supported catalyst claim 1, further comprising at least one additional bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanoparticle, or oxides thereof, deposited on the exterior surface.

10. The supported catalyst of claim 1, wherein the size of the hollow space and the bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) nanoparticle, or oxides thereof, are larger than the average pore size of the pores in the hollow zeolite support.

11. The supported catalyst of claim 10, wherein the average particle size of the bimetallic (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) 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%.

12. The supported catalyst of claim 1, wherein M.sup.1 and M.sup.2 are each 1 to 20 weight % of the total weight of the bimetallic nanostructure or wherein M.sup.1, M.sup.2, and M.sup.3 are each 1 to 20 weight % of the total weight of the trimetallic nanostructure.

13. The supported catalyst of claim 1, wherein the hollow zeolite support is 80 to 99.5 wt. % of the supported catalyst.

14. The supported catalyst of claim 1, wherein the catalyst is configured to catalyze a hydrocarbon reformation reaction.

15. The supported catalyst of claim 14, wherein the reformation reaction is a dry reformation of methane reaction or a steam reformation reaction, preferably a steam reformation reaction.

16. A method of producing H.sub.2 and CO comprising contacting a reactant gas stream that includes hydrocarbons and CO.sub.2 or H.sub.2O with the supported catalyst of claim 1 sufficient to produce a product gas stream comprising H.sub.2 and CO.

17. The method of claim 16, wherein coke formation on the supported nanostructure catalyst is substantially or completely inhibited.

18. The method of claim 16, wherein the reactant gas stream comprises C.sub.1 to C.sub.8 hydrocarbons, preferably methane, and CO.sub.2 or the reactant gas stream comprises C.sub.1 to C.sub.8 hydrocarbons, preferably methane, and H.sub.2O and optionally O.sub.2, or the reactant gas stream comprises C.sub.1 to C.sub.8 hydrocarbons, preferably methane, and H.sub.2O and CO.sub.2 and H.sub.2O.

19. The method of claim 16, 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.sup.1.

20. A method of making the supported catalyst of claim 1, the method comprising: (a) obtaining a zeolite support; (b) obtaining a first suspension by suspending the zeolite support in an aqueous solution having a M.sup.1 precursor material, a M.sup.2 precursor material, and optionally a M.sup.3 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, preferably tetrapropylammonium hydroxide (TPAOH), and thermally treating the suspension to obtain a templated support; and (d) calcining the templated support to obtain the supported catalyst of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] FIG. 1A is an illustration of an embodiment of cross-sectional view of an encapsulated nanostructure in a hollow zeolite with the nanostructure contacting the inner surface of the hollow space.

[0032] FIG. 1B is an illustration of an embodiment of cross-sectional view of an encapsulated nanostructure in a hollow zeolite with the nanostructure not contacting the inner surface of the hollow space.

[0033] FIG. 1C is an illustration of an embodiment of cross-sectional view of encapsulated nanostructures in a hollow zeolite with the nanostructure.

[0034] FIG. 2 is an illustration of a method of making the encapsulated nanostructure in a hollow zeolite.

[0035] FIG. 3 shows isothermal plots of silicate-1 and hollow silicate-1.

[0036] FIGS. 4A-C are transmission electron microscope (TEM) images of hollow zeolite (silicate-1) at various magnifications.

[0037] FIG. 4D is a TEM image of nickel oxide (NiO) in a hollow zeolite.

[0038] FIG. 4E is a TEM image of the bimetallic NiCo in a hollow zeolite.

[0039] FIG. 4F is a TEM image of bimetallic NiRu in a hollow zeolite.

[0040] FIG. 5 shows graphs of methane conversion in percent versus time of stream in hours for comparative samples and NiCo/HZ and NiRu/HZ catalysts of the present invention (HZ referring to hollow zeolite).

[0041] FIG. 6 shows graphs of percent carbon dioxide conversion in percent versus time of stream in hours for comparative samples and NiCo/HZ and NiRu/HZ catalysts of the present invention (HZ referring to hollow zeolite).

[0042] FIG. 7 shows graphs of hydrogen/carbon dioxide ratios versus time of stream in hours for comparative samples and NiCo/HZ and NiRu/HZ catalysts of the present invention (HZ referring to hollow zeolite).

[0043] 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.

DETAILED DESCRIPTION OF THE INVENTION

[0044] 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 NiPt catalysts. The catalyst is based on encapsulating a bimetallic (M.sup.1M.sup.2) or a trimetallic (M.sup.1M.sup.2M.sup.3) nanostructure in a hollow space of a zeolite. Notably, the catalyst does not rely on the presence of Pt such as NiPt 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.

[0045] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst Structure

[0046] 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. FIGS. 1A through 1C are cross-sectional illustrations of catalyst material 10 having an encapsulated metal nanostructure/hollow zeolite structure. The catalyst material 10 has a zeolite shell 12, a bimetallic or trimetallic nanostructure 14 and hollow space 16. In some embodiments, a portion of the nanostructure 14 (e.g., M.sup.1 and M.sup.2 and/or M.sup.3) can be deposited on the surface of the zeolite (not shown). As discussed in detail below, the hollow space 16 can be formed by removal of a portion of the zeolite core during the making of the catalyst material. As shown in FIG. 1A, the bimetallic or trimetallic nanostructure 14 contacts a portion of the inner wall of hollow space 16. As shown in FIG. 1B, the bimetallic or trimetallic nanostructure 14 does not contact the walls of the hollow space 16. As shown in FIG. 1C, multiple bimetallic or trimetallic nanostructures 14 are in hollow space 16 with some bimetallic or trimetallic nanostructures touching the inner wall of the hollow space. In certain aspects, 1% to 99%, 10% to 80%, 20% to 70%, 30% to 60%, 40% to %0% or any range or value there between of the nanostructures fills the hollow space 16. A diameter of the bimetallic or trimetallic nanostructure 14 can range from 1 nm to 100 nm, preferably 1 nm to 50 nm, or more preferably 1 nm to 5 nm or any value or range there between. In some embodiments, 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%. The pore size of the catalyst is the same or similar to the pore size of the starting zeolite (e.g., about 5.5 ). A volume space of the hollow space can be about 30 to 80%, 40 to 70%, or 50 to 60% of the zeolite particle volume or 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or any value or range there between.

[0047] 1. Bimetallic or Trimetallic Nanostructure

[0048] 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., NiCo or NiRu). 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).

[0049] 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. M.sup.1 and M.sup.2 are each 1 to 20 weight % of the total weight of the bimetallic nanostructure or wherein M.sup.1, M.sup.2, and M.sup.3 are each 1 to 20 weight % of the total weight of the trimetallic nanostructure. A molar amount of each metal (e.g., M.sup.1 and M.sup.2 or M.sup.1, M.sup.2, and M.sup.3) 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 (M.sup.1M.sup.2) or trimetallic (M.sup.1M.sup.2M.sup.3) 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%.

[0050] 2. Zeolite Material

[0051] 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 SiO.sub.4 and AlO.sub.4 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.).

B. Preparation Encapsulated Nanoparticle/Hollow Zeolite Material

[0052] 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).

[0053] FIG. 2 is a schematic of an embodiment of a method to make the encapsulated metal nanoparticle/hollow shell zeolite material. In method 20, step 1, the zeolite material 22 can be obtained either through a commercial source or prepared using the methods described in the Examples section. An aqueous solution of the M.sup.1 precursor material (e.g., a nickel precursor), a M.sup.2 precursor material (e.g., ruthenium or cobalt precursors), and optionally a M.sup.3 precursor material can be contacted with the zeolite material to allow impregnation of the zeolite material with the precursor materials 24. The amount of solution of metal precursor material is the same or substantially the same as the pore volume of the zeolite material. The impregnated zeolite material can be dried to obtain a bimetallic or trimetallic impregnated zeolite material 26. Drying conditions can include heating the impregnated zeolite material 26 from 30 C. to 100 C., preferably 40 C. to 60 C., for 4 to 24 hours. In step 2, the impregnated zeolite material 26 can be contacted (suspended) with an aqueous solution of a templating agent (e.g., a quaternary ammonium hydroxide compound) and the resulting suspension is subjected to a dissolution-recrystallization process to produce the encapsulated nanoparticle/zeolite composite material 28 having metal nanostructures 24 positioned in hollow 30. In some embodiments, the zeolite is subjected to a vacuum prior to impregnation (e.g., 100 to 300 C. for 6 h under 10.sup.6 bar) to facilitate metal diffusion through the pores. The dissolution-recrystallization process under hydrothermal conditions can include techniques of heating aqueous solutions of the aqueous templated zeolite suspension at high vapor pressures. In a particular embodiment, the suspension is heated to 100 C. to 250 C., preferably 150 C. to 200 C., for 12 to 36 hours, preferably 18 to 30 hours under autogenous pressure. Dissolution-recrystallization can performed in a pressure vessel, such as an autoclave, by a temperature-difference method, temperature-reduction method, or a metastable-phase technique. Without wishing to be bound by theory, it is believed that during the dissolution-recrystallization process, the hollow is formed in the zeolite framework through dissolution of some of the silicon core by the templating agent. The removed silica species can recrystallize on the outer surface upon cooling. During the hydrothermal process, the metal precursors can form a bimetallic or trimetallic nanostructure in the hollow space. Since the bimetallic or trimetallic particles are too large to migrate through the microporous zeolite walls, they remain in the hollow space. In some instances, small nanostructures come together and form a larger nanostructure or a single nanostructure in the hollow space. In step 3, the resulting metal-zeolite composite material 28 can be heated in the presence of air (e.g., calcined) to remove the template and any organic residues to form encapsulated bimetallic or trimetallic nanostructure/hollow zeolite material 10. Calcination conditions can include a temperature of 350 C. to 550 C., preferably 400 C. to 500 C. and a time of 3 to 10 hours, preferably 4 to 8 hours. In step 4, the encapsulated bimetallic or trimetallic nanostructure/hollow zeolite material 28 can be subjected to conditions sufficient to reduce the metals to their lowest valence and form bimetallic or trimetallic nanostructure 32. In one instance, the catalyst material 10 can be heated under a hydrogen atmosphere to form a zero valent (e.g., Ni(0)Co(0) or Ni(0)Ru(0)) nanostructure. Without wishing to be bound by theory, it is believed that treating the metal nanostructure with hydrogen can generate larger metal particles from smaller metal oxide particles in the hollow zeolite.

C. Reformation of Hydrocarbons

[0054] Also disclosed is a method of producing hydrogen and carbon monoxide from hydrocarbons under reforming conditions to produce hydrogen (H.sub.2) 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 (CO.sub.2), oxygen (O.sub.2), oxygen enriched air, or any combination thereof) water (H.sub.2O), 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.sup.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.

[0055] 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.

[0056] The reactant gas mixture can include natural gas, liquefied petroleum gas comprising C.sub.2-C.sub.5 hydrocarbons, C.sub.6+ heavy hydrocarbons (e.g., C.sub.6 to C.sub.24 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.

[0057] 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).

EXAMPLES

[0058] 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.

Example 1

Synthesis of Silicate-1

[0059] Silicalite-1 is obtained by mixing tetraethylorthosilicate (TEOS, 98% purity, Sigma-Aldrich, USA) and tetrapropylammonium hydroxide (TPA(OH), 1.0 M, in H.sub.2O, Sigma-Aldrich, USA) with water. The gel composition is: SiO.sub.2:0.4 TPA(OH):35H.sub.2O. 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.

Example 2

Synthesis of Ni/Hollow-Silicate-1 (HZ) Comparative Catalyst Material

[0060] Silicalite-1 from Example 1 was impregnated with aqueous solution of Ni(NO.sub.3).sub.2.6H.sub.2O (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 H.sub.2O). 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.

Example 3

General Synthesis Method of Metal Hollow-Silicate-1 Catalyst Material

[0061] Silicalite-1 from Example 1 was impregnated silicalite-1 was impregnated with aqueous solution of Ni(NO.sub.3).sub.2.6H.sub.2O (Sigma-Aldrich, USA) and Co(NO.sub.3)2.6H.sub.2O (Aldrich) or RuCl.sub.3H.sub.2O (Aldrich) to produce 5.5 wt % of NiM.sup.2 (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 H.sub.2O). 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.

TABLE-US-00001 TABLE 1 Sample No. Catalysts Compositions 1 Ni/HZ 1.8 wt % of Ni HZ 2 Ni/HZ 5.5 wt % of Ni HZ 3 NiCo/HZ 5.5 wt % of Ni/Co (50/50) HZ 4 NiRu/HZ 5.5 wt % of Ni/Ru (50/50) HZ

Example 4

Characterization of Catalyst Samples 1-4

[0062] Isothermal Analysis.

[0063] Nitrogen Isotherms of the HZ-1 and silicate-1 using a ASAP 2020 Micromeritics instrument (Micromeritics, USA) were obtained. FIG. 3 are isothermal graphs of the silicate-1 and HZ-1. Table 2 lists the BET surface area and pore volumes of each sample. Data line 32 is for the hollow silicate-1 samples and data line 34 is for the HZ-1 samples. The surface area for the HZ-1 catalyst was lower than the surface area for silicate-1 (237 m.sup.2g.sup.1 vs. 326 m.sup.2g.sup.1). The pore volume for the HZ-1 sample was greater than the pore volume of the silicate-1 sample (0.25 cm.sup.3g.sup.1 vs. 36 cm.sup.3g.sup.1). Without wishing to be bound by theory, it is believed that the lower BET surface area was due to the dissolution of the silicate-1 core, while the higher pore volume was due to the formation of the hollow.

[0064] Transmission Electron Microscopy (TEM).

[0065] TEM analysis was performed on comparative sample 2 and inventive catalyst samples 3 and 4. FIG. 4 are TEM images of the comparative catalysts, inventive catalysts and the HZ-1. FIGS. 4A-C are images of the HZ-1. From the image in FIG. 4A a particle size of the HZ-1 was about 150*150*200 nm. FIGS. 4B-C show the homogeneity of the hollow formation on the MFI zeolite structure. FIG. 4D is an image of the Ni/HZ comparative sample, FIG. 4E is an image of the NiCo/HZ catalyst and FIG. 4E is an image of the NiRu/HZ catalyst. The presence of the metals were confirmed by the EDX analysis. From the EDX analysis, it was observed that some metallic oxide on the external surface of the particle.

Example 5

Carbon Dioxide Reforming of Methane Reaction (CDRM)

[0066] 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.sup.1 for a gas composition of 10% Argon/5% CO.sub.2/45% methane for 30 hours of operation. The reactor flow was 50 cc.min.sup.1.

[0067] FIG. 5 depicts the CH.sub.4 conversion at different temperatures. Data line 52 is comparative sample 1 (1.8 wt. % Ni/HZ), data line 54 is comparative sample 2 (5.5 wt. % Ni/HZ), data line 56 is inventive catalyst sample 3 (NiCo/HZ), and data line 58 is inventive catalyst sample 4 (NiRu/HZ). FIG. 6 depicts the CO.sub.2 conversion at different temperatures. Data line 62 is comparative sample 1 (1.8 wt. % Ni/HZ), data line 64 is comparative sample 2 (5.5 wt. % Ni/HZ), data line 66 is inventive catalyst sample 3 (NiCo/HZ), and data line 68 is inventive catalyst sample 4 (NiRu/HZ). FIG. 7 depicts the H.sub.2/CO ratio of the different HZ at different temperatures. Data line 72 is comparative sample 1 (1.8 wt. % Ni/HZ), data line 74 is comparative sample 2 (5.5 wt. % Ni/HZ), data line 76 is inventive catalyst sample 3 (NiCo/HZ), and data line 78 is inventive catalyst sample 4 (NiRu/HZ).

[0068] 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 H.sub.2/CO ratio, FIG. 7, it was determined that CO and H.sub.2 was generated. Thus, it was concluded that Ni catalysts in the absence of Co or Ru performed at 850 C. but the yield was very low. When the NiCo/HZ was used, the CH.sub.4 conversion reached 20% at 850 C. and decreased to 3% at 750 C., with little to no production of CO and H.sub.2 at 650 C. It was concluded that Co addition improved the efficiency of the single metal based catalyst at metal loading was very low. In the case of the RuNi system, the CH.sub.4 conversion reached 65% at 850 C., 50% at 750 C. and 35% at 650 C. These results correlated with the H.sub.2/CO ratio equal to 0.9, 0.8 and 0.5 respectively.

[0069] The H.sub.2/CO ratio obtained from the NiRu/HZ was greater than 0.5 (See, FIG. 7). The reactions using bimetallic/HZ catalysts provided higher % conversion of methane and carbon dioxide in a shorter period of time than single metal/HZ catalysts. Further, the NiRu/HZ catalyst was found to be stable without any deactivation for 30 hours of duration. Notably, no sintering or coke formation was observed (no appearance of dark black color on catalysts) in any of the catalysts of the present invention at temperatures above 800 C. The lack of coking was confirmed by performing a loss on ignition test of the used catalysts in an open atmosphere at 800 C.