Use of olivine catalysts for carbon dioxide reforming of methane

Abstract

Disclosed are metal oxide catalysts, and methods for their use, that includes a bulk metal oxide catalyst composed of at least two metals and nesosilicate. The catalyst is capable of catalyzing the carbon dioxide reforming of methane to produce hydrogen and carbon monoxide.

Claims

1. A bulk metal oxide catalyst capable of producing hydrogen (H.sub.2) and carbon monoxide (CO) from methane (CH.sub.4) and carbon dioxide (CO.sub.2), wherein the bulk metal oxide catalyst consists of an olivine structure having a crystal lattice that has discrete SiO.sub.4 anions and two metals (M.sup.1, M.sup.2) or three metals (M.sup.1, M.sup.2, M.sup.3) in the crystal lattice, where each SiO.sub.4.sup.4 has a Si cation and four O.sup. anions M.sup.2 is a dry reforming of methane catalytic metal, and the O.sup. anions are coordinated with the metals in the crystal lattice, and wherein the bulk metal oxide catalyst does not include a carrier or a support.

2. The bulk metal oxide catalyst of claim 1, wherein M.sup.1 comprises at least one metal from Groups IIA, VIB, VIIB, VIII, and Group IB or at least one compound thereof, and M.sup.2 comprises at least one metal from Group IIIB, IVB, VIB, VIII or at least one compound thereof, or at least one lanthanide or at least one compound thereof, wherein M.sup.1 and M.sup.2 are different.

3. The bulk metal oxide catalyst of claim 1, wherein M.sup.2 comprises nickel (Ni), scandium (Sc), zirconium (Zr), molybdenum (Mo), chromium (Cr), ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), platinum (Pt), copper (Cu), palladium (Pd), dysprosium (Dy), thulium (Tm), ytterbium (Yb), lutetium (Lu), cerium (Ce), or any compound thereof.

4. The bulk metal oxide catalyst of claim 1, wherein M.sup.1 comprises manganese (Mn), magnesium (Mg), calcium (Ca) or any compound thereof.

5. The bulk metal oxide catalyst of claim 1, wherein M.sup.1 comprises Mg or a compound thereof, or Ca or a compound thereof, and M.sup.2 comprises Ni or a compound thereof.

6. The bulk metal oxide catalyst of claim 1, wherein M.sup.3 comprises a metal from Group VIII or a compound thereof, Group IB or a compound thereof, or both, and wherein M.sup.1, M.sup.2 and M.sup.3 are different.

7. The bulk metal oxide catalyst of claim 6, wherein M.sup.3 comprises Pt, Ru, Rh, Ir, Au, Ag, Pd or any compounds thereof.

8. The bulk metal oxide catalyst of claim 1, wherein the bulk metal oxide catalyst is represented by the formula of (M.sup.1.sub.(1-x)M.sup.2.sub.x).sub.2SiO.sub.4, where 0<x0.5, and M.sup.1 and M.sup.2 are different.

9. The bulk metal oxide catalyst of claim 8, wherein M.sup.1 is Mg or Ca, and M.sup.2 is Ni.

10. The bulk metal oxide catalyst of claim 9, wherein the bulk metal oxide catalyst is (Mg.sub.0.5Ni.sub.0.5).sub.2SiO.sub.4, or (Ca.sub.0.5Ni.sub.0.5).sub.2SiO.sub.4.

11. The bulk metal oxide catalyst of claim 1, wherein the bulk metal oxide catalyst is represented by the formula of (M.sup.1.sub.(1-x)M.sup.2.sub.xM.sup.3.sub.y).sub.2SiO.sub.4, where 0<x0.5, 0<y0.05 and (x+y)0.5, and M.sup.1, M.sup.2, and M.sup.3 are different.

12. The bulk metal oxide catalyst of claim 11, wherein M.sup.1 is Mg or Ca, M.sup.2 is Ni, and M.sup.3 is Pt, Ru, Rh, or Ir.

13. The bulk metal oxide catalyst of claim 12, wherein the bulk metal oxide catalyst has the formula of (Ni.sub.0.5Mg.sub.0.5M.sup.3.sub.0.01).sub.2SiO.sub.4, where M.sup.3 is Pt, Ru, Rh, or Ir.

14. The bulk metal oxide catalyst of claim 11, wherein the bulk metal oxide catalyst crystal structure comprises a hexagonal closest packed arrays of the O.sup., a octahedral interstices, and a tetrahedral interstices, wherein one-half of the octahedral interstices are occupied by M.sup.1 cations, M.sup.2 cations, and/or M.sup.3 cations, and one-eighth of the tetrahedral interstices are occupied by Si cations (Si.sup.+).

15. The bulk metal oxide catalyst of claim 1, wherein M.sup.2 is Ni.

16. A method of making a bulk metal oxide catalyst of claim 1, the method comprising: (a) mixing M.sup.1, M.sup.2, and silicon dioxide (SiO.sub.2) to form a mixture; and (b) subjecting the mixture to conditions such that M.sup.1, M.sup.2, and SiO.sub.2 form the bulk metal oxide catalyst.

17. The method of claim 16, wherein the mixture is molded to form a molded mixture, and wherein conditions comprise: (a) heating the molded mixture to a temperature of about 1300 C. at a rate of 1 C.; (b) holding the molded mixture at temperature of about 1300 C. for about 24 hours; (c) cooling the hot molded mixture at a rate of about 1 C. to room temperature; (d) crushing and grinding the molded mixture from step (c); and (e) repeating steps (a) to (d).

18. A method of producing a gaseous mixture comprising contacting a reactant gas mixture comprising methane and an oxidant with the bulk metal oxide catalyst of claim 1 at a temperature of at least 800 C. to produce a gaseous mixture comprising hydrogen and carbon monoxide, wherein the catalyst is resistant to coke formation.

19. The method of claim 18, wherein the oxidant is carbon dioxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts a polyhedral structure of an olivine structure that includes nesosilicate and two metal cations.

(2) FIG. 2 shows X-Ray Diffraction (XRD) patterns of various bulk metal oxide catalysts of the invention.

(3) FIG. 3 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMg catalyst.

(4) FIG. 4 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgPt catalyst.

(5) FIG. 5 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgRu catalyst.

(6) FIG. 6 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgIr catalyst.

DETAILED DESCRIPTION OF THE INVENTION

(7) The currently available catalysts used to reform hydrocarbons into syngas are prone to sintering and coking, 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.

(8) A discovery has been made that avoids the sintering issues described above. The discovery is based on the use of bulk metal oxide catalysts and/or a supported catalyst containing forsterite, liebenbergite, monticelite, or any combination thereof. Without wishing to be bound by theory, it is believed that the solid state synthesis method and special calcination conditions to produce a catalyst having an olivine lattice can reduce or prevent agglomeration of the catalytic material and/or the support material at elevated temperatures, thereby reducing or preventing sintering of the materials.

(9) These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

(10) A. Nesosilicates

(11) The silicates used in the context of this invention are nesosilicates, SiO.sub.4.sup.4 anions. In a nesosilicate compound, counter ions (cationic metals) are coordinated by the four silicate oxygen atoms. The coordination with the cationic metals with the four oxygen atoms provides a nesosilicate (i.e., an olivine) crystal structure. In an olivine crystal structure, the SiO.sub.4.sup.4 anions are isolated from each other (i.e., the Si cations do not share oxygen atoms). The olivine structure is characterized by hexagonal close packed arrays of O.sup. anions in that one-half of the octahedral interstices are occupied by the cations of the metals of the invention, and one-eighth of the tetrahedral interstices are occupied by Si cations. FIG. 1 depicts a polyhedral structure of an olivine structure that includes nesosilicate and two metal cations. Nesosilicates of the invention can be prepared by heating silicon dioxide at high temperatures in the presence of other metal oxides. In another aspect of the invention, naturally occurring olivine minerals can be used as supports for the metals of the invention. Examples of olivine minerals that can be used as supports include, but are not limited to, the minerals of forsterite (Mg.sub.2SiO.sub.4), monticelite (CaMgSiO.sub.4), and combinations thereof. In a particular aspect of the invention, the support does not include iron or iron compounds.

(12) B. Metals

(13) The metals that can be used in the context of the present invention to create bulk metal oxides or supported catalysts include a metal from Group HA or compound thereof, a metal from Group IB or compound thereof, a metal from Group IIIB or compound thereof, a metal from Group IVB or compound thereof, a metal from Group VIB or compound thereof, a metal from Group VIII or compound thereof, at least one lanthanide or compound thereof, or any combination thereof. The metals or metal compounds can be purchased from any chemical supplier such as Sigma-Aldrich, Alfa-Aeaser, Strem, etc. Group HA metals (alkaline-earth metals) and Group IIA metal compounds include, but are not limited to, Mg, MgO, Ca, CaO, Ba, BaO, or any combinations thereof. Group IB metals and Group IB metal compounds include, but are not limited to, Cu and CuO. Group IIIB metals and Group IIIB metal compounds include, but are not limited to, Sc, Sc.sub.2O.sub.3, the lanthanides or lanthanide compounds, or any combination thereof. Lanthanides that can be used in the context of the present invention to create lanthanide oxides include La, Ce, Dy, Tm, Yb, Lu, or combinations of such lanthanides. Non-limiting examples of lanthanide oxides include CeO.sub.2, Dy.sub.2O.sub.3, Tm.sub.2O.sub.3, Yb.sub.2O.sub.3, Lu.sub.2O.sub.3, or La.sub.2O.sub.3, or any combination thereof. Lanthanide oxides can be produced by methods known in the art such as by high temperature (e.g., >500 C.) decomposition of lanthanide salts or by precipitation of salts into respective hydroxides followed by calcination to the oxide form. Group IVB metals and Group IV metal compounds include, but are not limited to, Zr and ZrO.sub.2. Group VIB metals and Group VI metal compounds include, but are not limited to, Cr, Cr.sub.2O.sub.3, Mo, Mo.sub.2O.sub.3, or any combination thereof. Group VIII metals and metal compounds include, but are not limited to, Ru, RuO.sub.2, Os, OsO.sub.2, Co, Co.sub.2O.sub.3, Rh, Rh.sub.2O.sub.3, Ir, Ir.sub.2O.sub.3, Ni, Ni.sub.2O.sub.3, Pd, Pd.sub.2O.sub.3, Pt, Pt.sub.2O.sub.3, or combinations thereof.

(14) Metal catalysts for the production of hydrogen and carbon monoxide from hydrocarbons and carbon dioxide include two or more of the above described metal or metals compounds in combination with nesosilicate. Catalytic material can be mixed with the nesosilicate. Catalytic material includes a catalytic metal, such as Sc, Zr, Mo, Cr, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, La, Ce, Dy, Tm, Yb, or Lu or any combination thereof. Base metals can include Mg, Ca, Ba, or any combination thereof. Metal compounds used in the catalysts of the invention include, for example, Sc.sub.2O.sub.3, ZrO.sub.2, Mo.sub.2O.sub.3, Cr.sub.2, O.sub.3, RuO.sub.2, OsO.sub.2, CO.sub.2O.sub.3, Rh.sub.2O.sub.3, Ir.sub.2O.sub.3, Ni.sub.2O.sub.3, Pd.sub.2O.sub.3, Pt.sub.2O.sub.3, La.sub.2O.sub.3, CeO.sub.2, Dy.sub.2O.sub.3, Tm.sub.2O.sub.3, Yb.sub.2O.sub.3, Lu.sub.2O.sub.3 MgO, CaO, BaO, or CuO. At least two metals, or at least three metals used in the catalyst can be combined such that the overall formula of the catalyst is
(M.sup.1.sub.1-xM.sup.2.sub.x).sub.2SiO.sub.4(I) where x=0x0.5 and M.sup.1 and M.sup.2 are different;
or
(M.sup.1.sub.1-x,M.sup.2.sub.x,M.sup.3.sub.y).sub.2SiO.sub.4(II) where 0x0.5, 0y0.5 and (x+y)0.5, and M.sup.1, M.sup.2, and M.sup.3 are different.

(15) As shown in formula (II), the ratio of M.sup.1, M.sup.2, to M.sup.3 is adjusted to compensate for the third metal. The third metal can be a noble metal. In preferred embodiments, M.sup.1 is calcium or magnesium or manganese, M.sup.2 is nickel, and M.sup.3 is a noble metal (e.g., Pt, Ru, Rh, Pd, or Ir). If four or more metals are contemplated, for example a mixture of Ni, Ca, Mg and Pt, the amount of M.sup.1 and M.sup.2 is adjusted to account for the fourth metal. It should be understood, that the number of metals can be varied as long as the empirical formula for the olivine structure of (AB).sub.2SiO.sub.4, where A and B are metals, is preserved.

(16) C. Preparation of Catalysts

(17) The bulk metal oxide catalyst of the present invention can be made by processes known in the art that provide an olivine lattice structure, for example, a solid state reaction with catalytic and/or base metals, and silicon oxide. A non-limiting example includes, mixing stoichiometric molar amounts of reactants until a homogeneous powder is formed. In embodiments when a noble metal is added as a third metal, the amount of at least one other catalytic material (for example, M.sup.2, when M.sup.2 is nickel) is adjusted such that the overall formula for the catalyst is (M.sup.1.sub.1-x, M.sup.2.sub.x, M.sup.3.sub.y).sub.2SiO.sub.4 where 0x0.5, 0y0.5 and (x+y)0.5, and M.sup.1, M.sup.2, and M.sup.3 are different. The powdered mixture can be dried at temperatures at about 115 C. to about 125 C. for 8 to 12 hours. The dried mixture can be mixed with force (for example, grinding, milling, or crushing), and then molded under a pressure of about 10 Tons-force/sq.inch to about 12 Tons-force/sq.inch (154 MPa to 185 MPa) to form pellets. The pellets may be any shape or size (for example, cylindrical, rods, round, elliptical, etc.). The pellets can be calcined by heating the pellets to a temperature between 1250 C. and 1350 C. at a rate of 1 C. per minute and holding at between 1250 C. and 1350 C. for 24 hours, and then cooled at a rate of about 1 C. per minute to ambient temperature (about 72 C.). The calcined pellets are then powdered using force (for example, crushed and ground). The resulting catalyst has an olivine structure that has discrete SiO.sub.4.sup.4 anions in the crystal lattice, where the O.sup. anions of the silicate are coordinated with the metals of the invention.

(18) The supported metal catalyst of the present invention can be made by generally known catalyst preparation techniques. In some embodiments, the support may be combined with metal to form a catalyst. The support can include forsterite, monticelite, liebenbergite, or any combination thereof. In some aspects of the invention, the support is heat-treated at temperatures prior to combining with a metal of the invention. In some embodiments, impregnation aids may be used during preparation of the catalyst. In certain embodiments, the support may be combined with a metal solution. The metal solution may be mixed with the support and/or sprayed on the support. The metal solution can include Group VIII metals or Group VIII metal compounds, for example, Ni. In some aspects, the metal solution includes Group VIII metals or metal compounds in combination with noble metals, such as Pt and/or Pd. In certain aspects, the metal solution includes Ni, Pt, Pd, Sc, Zr, Mo, Cr, Ru, Os, Rh, Ir, La, Ce, Dy, Tm, Yb, Lu, Co, or any combination thereof. The amount of metal or metal precursor is chosen such that supported catalyst has a total metal content of from 5-15 wt. %. In a non-limiting example, the catalyst is prepared using an incipient impregnation technique. The metal impregnated support can be dried at 80 to 120 C. for about 1 to 3 hours. The dried catalyst can be heat treated (e.g., calcined) at a temperature ranging from 800 C. to about 900 C. for about 3 hours or a time determined to be sufficient to oxide the metals impregnated on the support.

(19) As illustrated in the Examples section, the produced bulk metal oxide catalyst and supported metal catalysts of the invention are sinter and coke resistant materials at elevated temperatures, such as those typically used in syngas production or methane reformation reactions (e.g., 700 C. to 950 C. or a range from 725 C., 750 C., 775 C., 800 C., 900 C., to 950 C.). Further, the produced catalysts can be used effectively in carbon dioxide reforming of methane reactions at a temperature range from 700 C. to 950 C. or from 800 C. to 900 C., a pressure range of 1 bara, and/or at a gas hourly space velocity (GHSV) range from 1000 to 10000 h.sup.1.

(20) D. Carbon Dioxide Reforming of Methane

(21) Also disclosed is a method of producing hydrogen and carbon monoxide from methane and carbon dioxide. The method includes contacting a reactant gas mixture of a hydrocarbon and oxidant with any one of the bulk metal oxide catalysts and/or or supported metal oxide catalysts 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 700 C. to 950 C. or a range from 725 C., 750 C., 775 C., 800 C., to 900 C., or from 700 C. to 950 C. or from 750 C. to 900 C., 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 bulk metal oxide catalyst or the supported catalyst and/or sintering is reduced or does not occur on the bulk metal oxide catalyst or the supported catalyst. In particular instances, carbon formation or coking and/or sintering is reduced or does not occur when the bulk metal oxide catalyst and/or supported catalyst 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.

(22) 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 gaseous feed mixture has is substantially devoid of water or steam. In a particular aspect of the invention the gaseous feed contains 0.1 wt. % or less of water, or 0.0001 wt. % to 0.1 wt. % water. 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, etc.

(23) 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, etc.), 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.

(24) 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

(25) 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 Catalysts

(26) All materials for the synthesis of the bulk metal oxide catalysts were obtained from Sigma Aldrich Chemical Company.

(27) (Mg.sub.0.5Ni.sub.0.5).sub.2SiO.sub.4 Bulk Metal Oxide Catalyst.

(28) Nickel oxide (4.26 g 0.057 moles), magnesium oxide (2.30 g, 0.057 moles) and silicon dioxide (3.43 g, 0.057 moles) were mixed together to form a homogeneous powder of NiO, MgO and SiO.sub.2. The homogeneous powder was dried at 120 C. for 10 hours. The dried material was ground to a fine powder, and then pelletized (i.e., molded) with an infrared press at a pressure of about 10 tons to form cylindrical pellets. The formed pellets were calcined at 1300 C. at a ramp rate of 1 C. per minute, held at 1300 C. for 24 hours, and then cooled slowly to room temperature. The calcined pellets were crushed and ground to form a fine crystalline powder of (Ni.sub.0.5Mg.sub.0.5).sub.2SiO.sub.4, hereinafter NiMg catalyst. FIG. 2 are X-Ray Diffraction (XRD) spectra of various bulk metal oxide catalysts of the invention. As shown in FIG. 2, the NiMg catalyst has diffraction patterns relevant for olivine phases. These patterns are similar to an XRD spectra of natural olivine mineral.

(29) (Ca.sub.0.5Ni.sub.0.5).sub.2SiO.sub.4 Bulk Metal Oxide Catalyst.

(30) Nickel oxide (3.91 g 0.052 moles), calcium oxide (2.94 g, 0.052 moles) and silicon dioxide (3.15 g, 0.052 moles) were mixed together to form a homogeneous powder of NiO, CaO and SiO.sub.2. The homogeneous powder was dried at 120 C. for 10 hours. The dried material was ground to a fine powder, and then pelletized with an infrared press at a pressure of about 10 tons to form cylindrical pellets. The formed pellets were calcined at 1300 C. at a ramp rate of 1 C. per minute, held at 1300 C. for 24 hours, and then cooled slowly to room temperature. The calcined pellets were crushed and ground to form a fine crystalline powder of (Mg.sub.0.5Ni.sub.0.5).sub.2SiO.sub.4, hereinafter NiCa catalyst.

(31) Synthesis of Bulk Metal Oxide Catalysts Containing Noble Metals (Mg.sub.0.5Ni.sub.0.49M.sup.3.sub.0.01).sub.2SiO.sub.4, where M.sup.3 is a Pt, Ru, Rh, Ir.

(32) Nickel oxide, noble metal (II) salt, magnesium oxide, and silicon dioxide were mixed together in a molar ratio of 0.98(Ni):1(Ca):0.02(noble metal):1(SiO.sub.2 to form a homogeneous powder. The homogeneous powder was dried at 120 C. for 10 hours. The dried material was ground to a fine powder, and then pelletized with an infrared press at a pressure of about 10 tons to form cylindrical pellets. The formed pellets were calcined at 1300 C. at a ramp rate of 1 C. per minute, held at 1300 C. for 24 hours, and then cooled slowly to room temperature. The calcined pellets were crushed and ground to form a fine crystalline powder of (Mg.sub.0.5Ni.sub.0.49M.sup.3.sub.0.01).sub.2SiO.sub.4, hereinafter NiMgPt, NiMgRu, NiMgRh, and NiMgIr catalysts. As shown in FIG. 2, the NiMgPt, NiMgRu, NiMgRh, and NiMgIr catalysts have diffraction patterns relevant for olivine phases.

(33) Synthesis of Bulk Metal Oxide Catalysts Containing Noble Metals (Ca.sub.0.5Ni.sub.0.49M.sup.3.sub.0.01).sub.2SiO.sub.4, where M.sup.3 is a Pt, Ru, Rh, Ir.

(34) Nickel oxide, a noble metal (II oxidation state) salt, calcium oxide, and silicon dioxide were mixed together in a molar ratio of 0.98:1:0.02:1 to form a homogeneous powder. The homogeneous powder was dried at 120 C. for 10 hours. The dried material was ground to a fine powder, and then pelletized with an infrared press at a pressure of about 10 tons to form cylindrical pellets. The formed pellets were calcined at 1300 C. at a ramp rate of 1 C. per minute, held at 1300 C. for 24 hours, and then cooled slowly to room temperature. The calcined pellets were crushed and ground to form a fine crystalline powder of (Ca.sub.0.5Ni.sub.0.49M.sup.3.sub.0.01).sub.2SiO.sub.4, hereinafter NiCaPt, NiCaRu, NiCaRh, and NiCaIr catalysts.

(35) Synthesis of Supported Catalysts.

(36) Different supported catalysts were prepared by incipient wetness impregnation or pore filling method by dissolving the known amount of respective metal precursors in pore volume equivalent of deionized water and impregnating the solution with Olivine support by dropwise addition of metals precursor solution. After the impregnation, the impregnated material was dried at 80 C. in an oven under the flow of air. Drying was continued at 120 C. for 2 hours followed by calcination at 850 C. for 3 hours.

Example 2

Dry Reforming of Methane with Bulk Metal Catalysts of the Invention

(37) General Testing Procedure.

(38) The effectiveness of catalysts of the invention towards carbon dioxide reforming of methane (CDRM, dry reforming of methane) were tested using a high throughput reactor system (hte, GmbH, Heidelberg, Germany). The reactors were of a plug flow design and constructed of steel with ceramic liners. The ceramic liner was 5 mm in diameter and 60 cm in length. The ceramic liner is considered to be inert and used to inhibit steel catalyzed cracking of methane. Catalyst pellets were crushed and sieved to a particle size of 300-500 micrometers. A required amount of catalyst sieve fraction was placed on top of inert material inside the ceramic liner. The catalyst in its oxidized state was heated to about 800 C. in the presence of 90% nitrogen (N.sub.2) and 10% Ar. A mixture of 45% CO.sub.2+45% CH.sub.4+10% Argon (Ar) was used as feed. The mixture was provided to the reactor in 4 steps with 5 minute intervals, replacing the feed with equivalent amounts of nitrogen during the interludes. The reaction conditions are specified in the individual Examples. Gas chromatography was used for gas analysis with Ar being the internal standard. Methane and CO.sub.2 conversion was calculated as follows:

(39) ${\mathrm{CH}}_4\mathrm{conversion}=\frac{\mathrm{moles}\mathrm{of}\mathrm{methane}\mathrm{converted}}{\mathrm{moles}\mathrm{of}\mathrm{methane}\mathrm{in}\mathrm{feed}}100$${\mathrm{CO}}_2\mathrm{conversion}=\frac{\mathrm{moles}\mathrm{of}\mathrm{carbon}\mathrm{dioxide}\mathrm{converted}}{\mathrm{moles}\mathrm{of}\mathrm{carbon}\mathrm{dioxide}\mathrm{in}\mathrm{feed}}100$
The ratio of hydrogen (H.sub.2) to carbon monoxide (CO) was calculated as follows

(40) $H_2\text{/}\mathrm{CO}\mathrm{ratio}=\frac{\mathrm{moles}\mathrm{of}{H}_2\mathrm{in}\mathrm{product}}{\mathrm{moles}\mathrm{of}\mathrm{CO}\mathrm{in}\mathrm{product}}100$

(41) CDRM Using Bulk NiMg Catalyst.

(42) The bulk NiMg catalyst was tested at 800 C. at 1 bara, and a gas hourly space velocity (GSHV) of 83,500 h.sup.1 for 155 hours of operation. After 80 hours of operation, the percent conversion of methane was greater than 10%, the percent conversion of carbon dioxide was between 10 and 15%, and the H.sub.2/CO ratio was greater than about 0.5. FIG. 3 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours.

(43) CDRM Using Bulk NiMgPt Catalyst.

(44) The bulk NiMgPt catalyst was tested at 800 C. at 1 bara, and a gas hourly space velocity (GSHV) of 25,000 h.sup.1 for 155 hours of operation. After 20 hours of operation, the percent conversion of methane was between 80 and 90%, the percent conversion of carbon dioxide was between 70 and 80%, and the H.sub.2/CO ratio was greater than about 0.8. FIG. 4 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgPt catalyst.

(45) CDRM Using Bulk NiMgRu Catalyst.

(46) The bulk NiMgRu catalyst was tested at 800 C. at 1 bara, and a gas hourly space velocity (GSHV) of 83,500 h.sup.1 for 155 hours of operation. After 20 hours of operation, the percent conversion of methane was between 30 and 40%, the percent conversion of carbon dioxide was between 40 and 50%, and the H.sub.2/CO ratio was about 0.8. FIG. 5 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgRu catalyst.

(47) CDRM Using Bulk NiMgIr Catalyst.

(48) The bulk NiMgIr catalyst was tested at 800 C. at 1 bara, and a gas hourly space velocity (GSHV) of 83,500 h.sup.1 for 155 hours of operation. After about 30 hours of operation, the percent conversion of methane was between 20 and 30%, the percent conversion of carbon dioxide was between 30 and 40%, and the H.sub.2/CO ratio was about 0.7. FIG. 6 is a graphical depiction of % methane or % carbon dioxide conversion and the ratio of hydrogen to carbon monoxide versus time, in hours for the bulk NiMgRu catalyst.

(49) The H.sub.2/CO ratio obtained from all the reactions was greater than 0.5 (See, FIGS. 3-6), with the catalysts containing noble metals having a H.sub.2/CO of greater than 0.7. The reactions using bulk metal oxide catalysts containing a noble metal provided higher % conversion of methane and carbon dioxide in a shorter period of time than bulk metal oxide catalyst without noble metals. Further, the catalyst was found to be stable without any deactivation for 155 hours of duration. Notably, no sintering or coke formation was observed (no appearance of dark black color on catalysts) in any of these catalysts 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. Sintering was studied by powder X-ray diffraction. Moreover, in general, catalyst which was synthesized at very high temperature (1100-1300 C.) will not sinter when applied at lower temperature (in present case 800 C.). Based on these results, the bulk metal oxide catalysts of the invention provide solutions to coking and sintering problems encountered during dry reforming of hydrocarbons.