BI-REFORMING OF HYDROCARBONS TO PRODUCE SYNTHESIS GAS

Abstract

Disclosed are catalysts, methods, and systems for the bi-reforming of hydrocarbons. The method includes contacting a catalyst material with a reactant feed that includes hydrogen (H.sub.2), carbon monoxide (CO), carbon dioxide (CO.sub.2), methane (CH.sub.4), and water (H.sub.2O) to produce a product stream that has a H.sub.2/CO molar ratio of 1.4:1 to 2:1. The catalyst can have a metal oxide core, a redox metal oxide layer deposited on a surface of the metal oxide core, and a catalytically active metal deposited on the surface of the redox metal oxide layer. A dopant can be included in the redox metal oxide layer. The catalyst can have a corm-shell type structure.

Claims

1. A method of producing synthesis gas from methane, the method comprising contacting a reactant gas stream that includes hydrogen (H.sub.2), carbon monoxide (CO), carbon dioxide (CO.sub.2), methane (CH.sub.4), and water (H.sub.2O) with a catalyst material under conditions sufficient to produce a gaseous product stream comprising H.sub.2 and CO in a H.sub.2/CO molar ratio of 1.4 to 2.0, wherein the catalyst material comprises: a chemically inactive metal oxide core; a redox metal oxide layer deposited on a surface of the metal oxide core, the redox metal oxide layer comprising a dopant; and a catalytically active metal deposited on the surface of the redox metal oxide layer.

2. The method of claim 1, wherein the reaction conditions include a temperature of 700° C. to 1000° C., a pressure of about 0.1 MPa to 2 MPa, and a gas hourly space velocity of 500 h.sup.−1 to 100,000 h.sup.−1.

3. The method of claim 1, wherein the reactant stream comprises 25 vol. % to 40 vol. % H.sub.2, 5 vol. % to 30 vol. % CO, 5 vol. % to 20 vol. % CO.sub.2, 10 vol. % to 30 vol. % CH.sub.4, and 10 vol. % to 30 vol. % H.sub.2O.

4. The method of claim 3, wherein the reactant stream comprises 30 vol. % to 35 vol. % H.sub.2, 10 vol. % to 20 vol. % CO, 10 vol. % to 15 vol. % CO.sub.2, 15 vol. % to 20 vol. % CH.sub.4, and 15 vol. % to 20 vol. % H.sub.2O.

5. The method of claim 1, wherein the H.sub.2/CO molar ratio is 1.6 to 2.0, preferably 1.85.

6. The method of claim 1, wherein the conditions comprise contacting the catalyst at a temperature of at least 550° C. with a CO.sub.2 stream comprising at least 50 vol. % CO.sub.2 for at least 6 hours prior to contacting the catalyst with the gaseous reactant stream.

7. The method of claim 6, further comprising replacing a portion of the CO.sub.2 in the CO.sub.2 stream with CH.sub.4, H.sub.2O, CO, and H.sub.2 to produce the gaseous reactant stream.

8. The method of claim 7, wherein replacing a portion of the CO.sub.2 in the CO.sub.2 stream comprises: introducing CH.sub.4 to the CO.sub.2 stream and contacting the heated catalyst with the CO.sub.2/CH.sub.4 stream at a temperature of at least 600° C. for at least 1 hour; increasing the concentration of CH.sub.4 in the CO.sub.2/CH.sub.4 stream relative to the amount of CO.sub.2 over time to produce a CO.sub.2/CH.sub.4 stream comprising about equal amounts of CO.sub.2 and CH.sub.4; introducing H.sub.2O to the CO.sub.2/CH.sub.4 stream at temperature of at least 700° C. to form a CO.sub.2/CH.sub.4/H.sub.2O stream; and introducing CO and H.sub.2 to the CO.sub.2/CH.sub.4/H.sub.2O stream, forming the gaseous reactant stream comprising H.sub.2, CO, CO.sub.2, CH.sub.4, and H.sub.2O at a temperature of at least 700° C.

9. The method of claim 8, wherein step (b) further comprises increasing the temperature from 600° C. to at least 700° C. at a rate of about 5 to 10° C. per hour.

10. The method of claim 1, wherein coke formation on the catalyst is substantially or completely inhibited.

11. The method of claim 1, wherein the pressure remains constant for at least 600 hours, or at least 1200 hours.

12. The method of claim 1, further comprising providing the product stream to a direct reduced iron unit and reducing iron oxide to iron.

13. The method of claim 1, wherein catalyst has a core/shell structure where the redox-metal oxide layer surrounds the core, and preferably the core is an alumina or alkaline earth metal aluminate core.

14. The method of claim 13, wherein the alkaline earth metal aluminate core is magnesium aluminate, calcium aluminate, strontium aluminate, barium aluminate, or any combination thereof.

15. The method of claim 14, wherein the alkaline earth metal aluminate core is magnesium aluminate, the redox-metal oxide layer is a cerium oxide layer, the metal dopant is niobium (Nb), indium (In), lanthanum (La), gallium (Ga), or any combination thereof, and the active metal is nickel (Ni).

16. The method of claim 1, wherein: the chemically inactive metal oxide core is alumina or magnesium aluminate; the redox-metal oxide layer is cerium oxide (CeO.sub.2) and the metal dopant is niobium (Nb), indium (In), lanthanum (La), gallium (Ga), or alloy thereof, or any combination thereof; and the active metal is nickel.

17. The method of claim 16, wherein chemically inactive metal oxide core contains 65 wt. % to 85 wt. % alumina or magnesium aluminate; the redox-metal oxide layer contains 10 wt. % to 20 wt. % cerium oxide; and the nickel is present in an amount of 5 wt. % to 10 wt. %.

18. The method of claim 17, wherein 0.5 wt. % to 2 wt. % of niobium or indium is incorporated into the lattice framework of the cerium oxide layer.

19. The method of claim 1, wherein the redox-metal oxide layer has a thickness of 1 nanometer (nm) to 500 nm, preferably 1 nm to 100 nm, or more preferably 1 nm to 10 nm.

20. A system for direct reduction of iron ore, the system comprising: a reforming unit capable of producing synthesis gas comprising hydrogen (H.sub.2) and carbon monoxide (CO) in a H.sub.2/CO molar ratio of 1.6 to 2.0 from a gaseous reactant stream comprising H.sub.2, CO, carbon dioxide (CO.sub.2), methane (CH.sub.4), and water (H.sub.2O), the reforming unit comprising: a reaction zone comprising the gaseous reactant feed and a catalyst material, the catalyst material comprising: a chemically inactive metal oxide core; a redox metal oxide layer deposited on a surface of the metal oxide core, the redox metal oxide layer comprising a dopant; and a catalytically active metal deposited on the surface of the redox metal oxide layer; and a furnace in fluid communication with the reformer, the furnace capable of reducing iron ore using the synthesis gas received from the reformer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] FIG. 1 depicts a schematic of the catalyst core-shell structure.

[0026] FIGS. 2A-2C depict a reaction schematic of oxidation of carbon residuals by the catalyst of the present invention.

[0027] FIG. 3 is a schematic of a direct reduction iron system that includes the catalyst of the present invention.

[0028] FIG. 4A and FIG. 4B show (FIG. 4A) Scanning Transmission electron microscopic (STEM) images of γ-Al.sub.2O.sub.3 and (FIG. 4B) Energy dispersive X-ray diffraction spectrum EDX spectrum of γ-Al.sub.2O.sub.3 with the electron beam targeted at a point shown in FIG. 4A as “beam”.

[0029] FIG. 5A and FIG. 5B show (FIG. 5A) STEM images of 1 wt. % In+25 wt. % CeO.sub.2/γ-Al.sub.2O.sub.3 and (FIG. 5B) EDX spectrum of the sample with the electron beam targeted at a point shown in FIG. 5A as “beam”.

[0030] FIG. 6A and FIG. 6B show (FIG. 6A) STEM images of 8 wt. % Ni/i wt. % InO.sub.2+25 wt. % CeO.sub.2/γ-Al.sub.2O.sub.3 and (FIG. 6B) EDX spectrum of the sample with the electron beam targeted at a point shown in FIG. 6A as “beam”.

[0031] FIG. 7 shows % CO.sub.2 converted in different feed, Step number, and feed composition listed in Table 2.

[0032] FIG. 8 shows % CH.sub.4 converted in different feed, Step number, and feed composition listed in Table 2.

[0033] FIG. 9 shows H.sub.2/CO ratio obtained with different feed composition, Step number, and feed composition listed in Table 2.

[0034] FIG. 10 shows X-ray diffraction (XRD) patterns for spent catalysts (a) commercial catalyst, (b) Ni/In—CeO.sub.2—MgAl, (c) Ni/Nb—CeO.sub.2—MgAl, and (d) Ni/La—CeO.sub.2—MgAl core-shell catalysts.

[0035] FIG. 11 shows temperature programmed oxidation profiles of spent catalysts.

[0036] FIG. 12 shows accelerated coking studies conducted over commercial as well as Ni/In—CeO.sub.2—MgAl and Ni/La—CeO.sub.2—MgAl core-shell catalysts.

[0037] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The currently available catalysts used to bi-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 and ultimately with its use for reducing iron ore to iron.

[0039] A discovery has been made that avoids problems associated with deactivation and mechanical degradation of bi-reforming catalysts. The discovery is based on the use of a catalyst that has a particular core-shell structure. The core includes a chemically inert or substantially inert material (e.g., metal oxide core, a clay core, or a zeolite core, or any combination thereof). The shell surrounds the core and has a redox-metal oxide phase that includes a metal dopant incorporated into the lattice framework of the redox-metal oxide phase. An active/catalytic metal is deposited on the surface of the shell. Without wishing to be bound by theory, it is believed that the catalyst having such a core-shell structure as described throughout the specification can oxidize carbon formed on its surface due to methane decomposition and carbon monoxide disproportion. Such a catalyst has a minimal loss of catalytic activity over more than 300 hours of usage. Further, the catalysts of the present invention have increased mechanical strength and decreased costs during the preparation process when compared with currently available bi-reforming of methane-based catalysts. Still further, and in some particular instances wherein the core material is an alkaline aluminate core (e.g., magnesium aluminate MgAl.sub.2O.sub.4)), it is believed that such a core has a high affinity towards CO.sub.2, thereby adsorbs more carbon dioxide and helping to oxidize carbon formed on the catalysts to further reduce the incidence of coking and sintering. The catalyst can be used in the bi-reforming of methane reaction to produce a product stream having a H.sub.2/CO molar ratio of 1.4:1 to 2.0:1, preferably about 1.85:1. This product stream can be used for the direct reduction of iron without further purification.

[0040] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst and Catalyst Structure

[0041] The catalyst material can include chemically inactive metal oxide core (e.g., Al.sub.2O.sub.3, alkaline earth metal aluminate, SiO.sub.2, TiO.sub.2, zeolites, amorphous silica alumina, clays, olivine sand, spinels, perovskites, MgO, or ZrO.sub.2, preferably Al.sub.2O.sub.3 or gamma-Al.sub.2O.sub.3 or alkaline earth metal aluminate (e.g., magnesium aluminate, calcium aluminate, strontium aluminate, barium aluminate)); a redox metal oxide (e.g., cerium oxide (CeO.sub.2)) layer deposited on a surface of the metal oxide core, the redox metal oxide layer comprising a dopant (niobium (Nb), indium (In), or lanthanum (La), gallium (Ga), or any combination thereof); and a catalytically active metal (e.g., nickel, rhodium, ruthenium, platinum, or any combination thereof), deposited on the surface of the redox metal oxide layer. In some embodiments, the catalyst can include an alumina or magnesium aluminate core, a CeO.sub.2 redox-metal oxide layer with Nb, In, and/or La as the metal dopant, and Ni as the active metal. In some embodiments, the catalyst includes 65 wt. % to 85 wt. % alumina or magnesium aluminate, 10 wt. % to 20 wt. % cerium oxide; and 5 wt. % to 10 wt. % nickel. In certain aspects, 0.5 wt. % to 2 wt. % of niobium or indium can be incorporated into the lattice framework of the cerium oxide layer. The redox-metal oxide layer can have a thickness of 1 nanometer (nm) to 500 nm, preferably 1 nm to 100 nm, or more preferably 1 nm to 10 nm. In some aspects, the catalyst can have a core/shell structure where the redox-metal oxide layer surrounds the alumina or alkaline earth metal aluminate core. In a preferred embodiment, the catalyst includes a magnesium aluminate core, a cerium oxide layer, a Nb, In, La, Ga, or any combination thereof dopant, and Ni as the active metal.

[0042] In some instances, the catalyst does not include a metal dopant, but includes two or more metals deposited on the surface of the redox-metal oxide shell. The core can be chemically inert during the bi-reforming of methane reaction and can also provide sufficient mechanical support for the reactive shell of the catalyst. The shell can have a redox-metal oxide phase that includes a metal dopant (e.g., indium, niobium, or both) incorporated into the lattice framework of the redox-metal oxide phase. The shell can have a greater oxygen mobility when compared with the core. In one particular aspect, the core is Al.sub.2O.sub.3, the redox-metal oxide phase is cerium dioxide, the metal dopant is indium or niobium or both, and the metal deposited on the surface of the shell is nickel, rhodium, ruthenium, or platinum or any combination thereof (e.g., nickel, nickel and platinum or nickel and rhodium). The shell can have a thickness of one atomic monolayer to 100 atomic multilayers (e.g., 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 atoms thick). In some aspects, the catalyst includes 5 to 50 wt. %, preferably 7 to 20 wt. %, and more preferably from 9 to 15 wt. % of the redox metal oxide phase, 0.1 to 5 wt. %, preferably, 0.75 to 4 wt. %, or more preferably 1 to 3 wt. % of the metal dopant, 1 to 40 wt. %, preferably, 2 to 15 wt. %, or more preferably 5 to 12 wt. % of the metal deposited on the surface of the shell, or combinations thereof. The catalyst can be in particulate form. In some instances, the catalyst has a mean particle size of 100 to 1000 μm, preferably, 200 to 800 μm, or more preferably from 250 to 550 μm. In certain aspects of the invention, the catalyst is self-supporting, however, the catalyst can be supported by a substrate (e.g., glass, a polymer bead, or a metal oxide).

[0043] FIG. 1 is a schematic of a core-shell structure of a catalyst of the present invention. Catalyst 100 includes core 102, shell 104, and active metal 106. Core 102 can be a substantially chemically inert material described throughout the specification. Core 102 can provide mechanical strength to the shell 104. Shell 104 can be a material (e.g., a metal oxide) that is capable of undergoing shifts in electronic states (e.g., reduction and oxidation states (redox). Such materials are described throughout the specification. Shell 104 can be formed on the core. In a preferred embodiment, shell 104 substantially or completely surrounds the core. In some aspects, shell 104 can be attached to the outer surface of the core 102. One or more dopants (not shown) described throughout the specification can be included in the crystal lattice of the shell 104. Active metals 106 described throughout the specification can be deposited on top of the shell 104 layer. Active metals 106 are catalytically active during the dry reformation of methane reaction process. The core-shell structure of catalyst 100 can provide an economical, mechanically strong, and highly efficient catalyst for use during a dry reformation of methane reaction. Catalyst 100 can be in any form or shape. In a preferred embodiment, the catalyst is in particulate form. The particulates can have a mean particle size of 100 to 1000 μm, preferably, 200 to 800 μm, or more preferably from 250 to 550 μm, or from 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 950, 960, 970, or 1000 μm or any value or range there between. Surface area can be measured using Brunauer, Emmett, and Teller (BET) method. In some embodiments, the catalyst is supported by a substrate. Non-limiting examples of a substrate include glass, a polymer bead or metal oxide. The metal oxide can be the same or a different metal oxide as the core material or the shell material.

[0044] 1. Core

[0045] Core 102 can be a metal oxide, a clay, a zeolite, or any combination thereof. The core 102 can be a porous material, a chemically inert material, or both. Non-limiting examples of metal oxides include refractory oxides, alpha, beta or theta alumina (Al.sub.2O.sub.3), activated Al.sub.2O.sub.3, alkaline earth metal aluminate, silicon dioxide (SiO.sub.2), titanium dioxide (TiO.sub.2), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), zirconium oxide (ZrO.sub.2), zinc oxide (ZnO), lithium aluminum oxide (LiAlO.sub.2), magnesium aluminum oxide (MgAlO.sub.4), manganese oxides (MnO, MnO.sub.2, Mn.sub.2O.sub.4), lanthanum oxide (La.sub.2O.sub.3), silica gel, aluminosilicates, amorphous silica-alumina, magnesia, spinels, perovskites, or any combination thereof. Non-limiting examples of alkaline earth metal aluminates includes magnesium aluminate, calcium aluminate, strontium aluminate, barium aluminate, or any combination thereof, with magnesium aluminate being particularly preferred. Non-limiting examples of clays include kaolin, diatomaceous earth, activated clays, smectites, palygorskite, sepiolite, acid modified clays, thermally-modified clays, chemically treated clays (e.g., ion-exchanged clays), or any combination thereof. Examples of zeolites include Y-zeolites, beta zeolites, mordenite zeolites, ZSM-5 zeolites, and ferrierite zeolites. All of the materials used to make the supported catalysts of the present invention can be purchased or made by processes known to those of ordinary skill in the art (e.g., precipitation/co-precipitation, sol-gel, templates/surface derivatized metal oxides synthesis, solid-state synthesis, of mixed metal oxides, microemulsion technique, solvothermal, sonochemical, combustion synthesis, etc.). Non-limiting examples of commercial manufacturers of core materials include Zeolyst (U.S.A.), Alfa Aesar® (USA) CRI/Criterion Catalysts and Technologies LP (U.S.A.), and Sigma-Aldrich® (U.S.A.), BASF (Germany), and UNIVAR® (U.S.A.). The core materials can be any shape or form. Non-limiting examples of shapes and forms include a spherical shape, a cylindrical shape (e.g., extrudates, pellets), a hollow cylindrical shape, a pellet shape, or is shaped to have 2-lobes, 3-lobes, or 4 lobes, or is a monolith. The core material can be cylindrical particles having a diameter of about 0.10 to 0.5 centimeters (cm), 0.15 to 0.40 cm, or 0.2 to 0.3 cm in diameter. The surface area of the core material can range from 5 to 300 m.sup.2/g, 10 to 280 m.sup.2/g, 20 to 270 m.sup.2/g, 30 to 250 m.sup.2/g, 40 to 240 m.sup.2/g, 50 to 230 m.sup.2/g, 60 to 220 m.sup.2/g, 70 to 210 m.sup.2/g, 80 to 200 m.sup.2/g, 100 to 150 m.sup.2/g, or any range or value there between. In a preferred embodiment, the support material is gamma-alumina extrudates having a diameter of about 0.32 cm (⅛ inch) with a BET surface area of about 230 m.sup.2/g. The support material can have a Barrett-Joyner-Halenda (BJH) adsorption cumulative volume of pores between 1.7000 nm and 300.0000 nm of 0.557 cm.sup.3/g and BJH Adsorption average pore diameter (4V/A) of 6.78 nm. In some particularly preferred instances where the core includes magnesium aluminate, the core can include 5 wt. % to 60 wt. % MgO, or 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50 wt. %, 55 wt. %, 60 wt. % or any range or value there between.

[0046] 2. Shell

[0047] Shell 104 can be a layer that includes a metal oxide that is able to assume multiple oxidation states depending on the chemical conditions or its redox capability. The reductant and oxidant can be redox couple (e.g., M.sup.+/M.sup.2+). Shell 104 can have a thickness of one atomic monolayer to 100 atomic multilayers, or 5 to 80 atomic multilayers, 10 to 60 atomic multilayers, or 20 to 5 atomic multilayers, or 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 100 atomic multilayers or any range or value there between. Non-limiting examples of metal oxides that can have a redox-metal oxide phase (e.g., redox couple) include cerium (Ce) oxide, an iron (Fe) oxide, a titanium (Ti) dioxide, a manganese (Mn) oxide, a niobium (Nb) oxide, a tungsten (W) oxide, or a zirconium (Zr) oxide, preferably a cerium oxide. Such metal oxides can form a cerium oxide phase, an iron oxide phase, a titanium dioxide phase, a manganese oxide phase, a niobium oxide phase, a tungsten oxide phase, or a zirconium oxide phase under certain chemical conditions (e.g., heat). The amount of redox-metal oxide can range from 5 to 50 wt. %, 7 to 20 wt. %, 9 to 15 wt. %, or 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50% by weight based on the total weight of catalyst. The metal oxide phase (or metal oxide layer) can include one or more metal dopants. The metal dopant can be incorporated into the crystal lattice of the metal oxide. A dopant can provide mechanical strength to the metal oxide lattice, decrease the amount of energy required to remove an oxygen anion from the metal oxide crystal lattice, or both. Non-limiting examples of metal dopants include indium (In), gallium (Ga), niobium (Nb), lanthanum (La), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), thallium (Tl), or lead (Pb), or any combination thereof, preferably indium. The amount of redox-metal oxide can range from 0.1 to 5 wt. %, 0.75 to 4 wt. %, 1 to 3 wt. %, or 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%. 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9% or 5.0% by weight based on the total weight of catalyst. The metal oxides and metal dopants can be purchased from commercial manufactures such as Sigma-Aldrich®.

[0048] The redox-metal oxide phase can change oxidation states. Therefore, the oxygen anions bonded to the crystal lattice can be released and other oxygen compounds (e.g., molecular oxygen, superoxides, and ozone) can be absorbed, thereby the oxygen in shell 104 has mobility. Due to the redox capability of the metal oxide, shell 104 can have a greater oxygen mobility than core 102. Due to the structure of the metal redox phase, the removal of the oxygen anion can occur without disrupting or destroying the crystal lattice of the metal oxide. As more oxygen atoms are abstracted, the concentration of vacancies can increase, thereby leaving behind two electrons to be shared between the metal atoms. The oxygen atoms can be abstracted from any surface or subsurface of the metal oxide. In a similar manner, the metal can absorb molecular oxygen (O.sub.2) into the vacancy which oxidizes some of the metals due to the increase in available electrons. Without wishing to be bound by theory, it is believed that the ability of the shell to store and release oxygen anions through this redox process assists in oxidizing carbon deposited on the surface of the catalyst to a carbon monoxide. For example, the carbon atom can deposit on the absorbed oxygen on the surface of the metal oxide and be released as carbon monoxide as shown in FIG. 2. FIG. 2 is a schematic of the oxidation of carbon by contact with the redox-metal oxide phase of the catalyst 100. In FIG. 2, for simplicity, active metal 106 and the core 102 are not depicted. Referring to FIG. 2A, carbon atom 202 is attracted to oxygen atom 204 that is bound to metal atom 206 of metal-redox phase of shell 104. As shown in FIG. 2B, carbon atom 202 bonds to the oxygen atom 204 to form carbon monoxide 208. In FIG. 2C, carbon monoxide 208 can diffuse from shell 104 and molecular oxygen 210 can be absorbed into a vacancy 212 to continue the oxidation of carbon residual process.

[0049] 3. Active Metals

[0050] Catalyst 100 can include one or more active (catalytic) metals to promote the reforming of methane to carbon dioxide. The active metals 106 can be attached to the surface of shell 104 (See, FIG. 1). The active metal(s) 106 can include one or more metals from Columns 7-11 of the Periodic Table (Groups VIIB, VIII, and IB). 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 or alloy thereof, preferably nickel, rhodium, ruthenium, or platinum, or any combination or alloy thereof. The amount of active metal on the shell 104 depends, inter alia, on the catalytic (metal) activity of the catalyst. In some embodiments, the amount of catalyst present on the shell ranges from 1 to 40 wt. %, 2 to 15 wt. %, 5 to 12 wt. %, or 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19.sup.0/a, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40% by weight based on the total weight of catalyst. In some instances, the active metal can be a binary alloy (M1M2) or a tertiary alloy (M1M2M3), where M1 is nickel (Ni), and M2 and M3 are each rhodium (Rh), ruthenium (Ru), iridium (Ir), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), cobalt (Co), manganese (Mn), copper (Cu), zinc (Zn), iron (Fe), molybdenum (Mo), or zirconium (Zr). In a particular instance, the active metal can be binary alloy (M1M2) where M1 is nickel and M2 is rhodium (Rh) or platinum (Pt) (e.g., NiRh, or NiPt).

B. Preparation of Core-Shell Catalysts

[0051] The catalyst of the present invention can be made by processes that provide for a core-shell structure. As further illustrated in the Examples, the catalyst can be made using known catalyst preparation methods (e.g., dry or wet impregnation, spraying methods, homogeneous deposition precipitation, atomic layer deposition techniques, dip coating, etc.). In a non-limiting example, a first metal salt (e.g., redox-metal salt) and a second metal salt (e.g., salt of the metal dopant) can be solubilized in a solution (e.g., water). Examples of the first metal salt includes nitrates, ammonium nitrates, carbonates, oxides, hydroxides, halides of Ce, Fe, Ti, Mn, Nb, W, or Zr. Examples of the second metal salt include nitrates, ammonium nitrates, carbonates, oxides, hydroxides, halides of Column 7-12 metals. In a particular embodiment, NbCh.sub.5, or InCl.sub.3.4H.sub.2O, and (NH.sub.4).sub.2Ce(NO.sub.3).sub.6, can be solubilized in deionized water. The weight ratio of the first metal salt to the second metal salt present in the solution can be at least 5:1, 5:1 to 30:1, 7:1 to 20:1, 10:1 to 15:1, or 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 to 1 or any range or value there between. In some embodiments, the second metal salt (metal dopant is not used). The solution can be pro volume impregnated with the core material (e.g., a metal oxide core). In a particular embodiment, the solution is pore volume impregnated with magnesium aluminate extrudates. The impregnated material can be dried an average temperature of 50 to 150° C., 75 to 100° C., 80 to 90° C., or 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150° C. for 2, 3, 4, 5, 6, 7, 8, 9, 10 hours or until the impregnated material is deemed to be dry. The dried impregnated material can be calcined (converted to the metal oxide) at an average temperature of 500 to 800° C., 600 to 700° C., or 500, 525, 550, 575, 600, 625, 650, 675, 700, 725, 750, 775, or 800° C. at 2, 3, 4 hours or until the impregnated material is deemed to be sufficiently calcined to obtain a core-shell structure where the shell surrounds the core and the shell has a redox-metal oxide phase formed from the first metal salt and metal dopant formed from the second metal salt incorporated into the lattice framework of the redox-metal oxide phase. This process can be repeated to obtain a shell having a desired amount of dopants to tune the oxygen mobility of the catalytic material.

[0052] In some embodiments, the solutions can be impregnated with the core material in a stepwise manner. For example, the redox metal-salt can be pore volume impregnated with the core material, dried and calcined and, then dopant metal can be pore volume impregnated with the core material, dried and calcined to form the core-shell material. This process can be repeated to obtain a shell having a desired amount of dopants to tune the oxygen mobility of the catalytic material. The redox metal oxide layer thickness can be increased by repeating the redox metal-salt impregnated step. Incorporation of the dopant in the redox metal oxide (e.g., CeO.sub.2) phase can be determined using X-ray diffraction methods. By way of example, a catalyst containing CeO.sub.2 and dopant will show a slight shifting in diffraction patterns related to CeO.sub.2 due to the incorporation of dopant. Some of dopant can be dispersed in the core, however, a majority of the dopant remains in shell and disperses homogeneously in shell during calcination.

[0053] One or more active metals can be deposited on the surface of the shell using known metal deposition methods (e.g., impregnations, spraying, chemical vapor depositing, etc.). In a non-limiting example, the core-shell structure can be slowly impregnated with an aqueous solution of active metal. For example, the active metal solution can be added dropwise to the metal oxide extrudates which were under constant mechanical stirring. The impregnated material can be dried at an average temperature of 50 to 120° C., 75 to 110° C., 80 to 90° C., or 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120° C. for 0.5, 1, or 2 hours or until the impregnated material is deemed to be dry. The dried impregnated core-shell material can be calcined (converted to the metal oxide) at an average temperature of 500 to 850° C., 600 to 800° C., or 500, 525, 550, 575, 600, 625, 650, 675, 700, 725, 750, 775, 800, 825, or 850° C. at 0.5, 1, or 2 hours or until the impregnated material is deemed to be sufficiently calcined to obtain the catalyst having a core-shell structure with active metal deposited on the surface of the shell (e.g., catalyst 100 in FIG. 1). The resulting core-shell catalyst can be crushed and sieved to a desired size, e.g., 300 to 500 μm.

[0054] The redox oxide precursor and active metal precursor impregnation can be performed on either powder or pre-shaped structures such as cylindrical hollow disc, cylindrical disc, sphere, 4- to 10-holes cylindrical disc shaped structure or 0.4 mm to 4 mm extrudates. If impregnation is performed on powders, the final catalyst can be pressed into different forms using pelletizing tools.

[0055] As illustrated in the Examples section, the produced core-shell catalysts of the invention are sinter and coke resistant materials at elevated temperatures, such as those typically used in syngas production or dry 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 0.1 MPa, and/or at a gas hourly space velocity (GHSV) range from 500 to 10000 h.sup.−1, preferably a temperature of 800° C., a pressure of 0.1 MPa, and a GHSV of 75,000 h.sup.−1.

C. Bi-Reforming of Methane

[0056] Also disclosed is a method of producing hydrogen and carbon monoxide (syngas) from a bi-reforming of methane reaction. In a particular instance, syngas can be produced from a methane, water, carbon monoxide, hydrogen, nitrogen and carbon dioxide containing reactant gas mixture feed. The method can include contacting the reactant gas mixture with any one of the catalysts of the present invention under sufficient conditions to produce hydrogen and carbon monoxide with a methane conversion of at least 50%, 60%, 70% 80% or more. Such conditions sufficient to produce the gaseous mixture can include a temperature range of 700° C. to 1000° C., from 750° C. to 950° C. or from 725° C., 750° C., 775° C., 800° C., 900° C., 1000° C., at pressure range of 0.1 MPa to 2.0 MPa, and/or a gas hourly space velocity (GHSV) ranging from 500 to 100,000 h.sup.−1 or a range from 500 h.sup.−1, 1000 h.sup.−1, 5000 h.sup.−1, 10,000 h.sup.−1, 20,000 h.sup.−1, 30,000 h.sup.−1, 40,000 h.sup.−1, 50,000 h.sup.−1, 60,000 h.sup.−1, 70,000 h.sup.−1, 80,000 h.sup.−1, 90,000 h.sup.−1, to 100,000 h.sup.−1. In a particular instance, an average temperature from 750 to 800° C., a pressure of 0.1 MPa, and a GHSV of 70,000 to 75,000 h.sup.−1 is used. Under such conditions, the methane conversion is 60 to 98%, preferably 80 to 95. The H.sub.2/CO ratio can be at least 1.4:1 to 2.0:1, or 1.5:1 to 1.95:1, 1.7:1 to 1.90:1, or at least, equal to, or between any two of 1.4:1, 1.45:1, 1.5:1, 1.55:1, 1.6:1, 1.65:1, 1.7:1, 1.75:1, 1.8:1, 1.85:1, 1.9:1, 1.95:1 and 2, or about 1.85:1. In particular instances, the hydrocarbon includes methane and the oxidants are water and carbon dioxide. In certain aspects, the carbon residual formation or coking is reduced or does not occur on the core-shell structured catalyst and/or sintering is reduced or does not occur on the core-shell structured catalyst. In particular instances, carbon residuals formation or coking and/or sintering is reduced or does not occur when the core-shell structured 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 1000° C. at a pressure of 0.1 to 0.2 MPa. Without wishing to be bound by theory it is believed that no or substantially little sintering occurs because the oxygen mobility is enhanced in the lattice of the catalyst, thus oxidizing coke from hydrocarbon decomposition, thereby, making the active sites available for a longer period. In instances when the produced catalytic material is used in bi-reforming methane reactions, the water and carbon dioxide in the gaseous feed mixture can be obtained from various sources. In a direct reduced iron system, carbon dioxide and water can be produced during reduction of iron ore in shaft furnace. Carbon monoxide converts to carbon dioxide and hydrogen converts to water in reduction process. The reactant gas mixture can include natural gas or methane, 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. 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).

D. Direct Reduced Iron System

[0057] In some embodiments, the bi-reformer unit used for bi-reforming of methane can be used in a direct reduced iron (DRI) system. Referring to FIG. 3, a DRI system is depicted. DRI system can include bi-reformer unit 302, shaft furnace 304, heat recovery system 306, scrubber 308, and cooling unit 310. Other heating and/or cooling devices (e.g., insulation, electrical heaters, jacketed heat exchangers in the wall) or controllers (e.g., computers, flow valves, automated values, etc.) that are necessary to control the reaction temperature and pressure of the reaction mixture. While only one unit is shown, it should be understood that multiple units can be housed in one unit. In system 300, reactant gaseous feed stream 312 can enter bi-reforming unit 302. Reactant gaseous feed stream 312 can include hydrocarbons (e.g., methane, ethane, propane, etc., preferably natural gas), water, carbon monoxide, hydrogen, carbon dioxide, and optional inert gas. In one preferred aspect, the feed stream can have a composition of 14 to 16 vol. % CO, 12 to 14 vol. % CO.sub.2, 32 to 36 vol. % H.sub.2, 16.5 to 19.5 vol. % H.sub.2O, 14 to 18 vol. % CH.sub.4, and 3.5 to 4.5 vol. % N.sub.2. Bi-reforming unit 302 can include a reaction zone 314, which includes catalyst 316 of the present invention. In reaction zone 314, reactant feed 312 can contact catalyst 316 and produce product stream 318. Product stream 318 can have a H.sub.2/CO molar ratio of 1.4:1 to 2:0:1, or about 1.85:1. Product stream 318 can exit bi-reforming unit 302 and enter shaft furnace 304. Iron oxide stream 320 can enter shaft furnace 304 and contact product stream 318. Contact of iron oxide stream 320 with product stream 318 can produce direct reduced iron stream 322 and recycle stream 324. Contact temperatures in furnace 304 can be at temperatures necessary to reduce the iron oxide. Recycle stream 324 can exit furnace 304, pass through scrubber 308 to remove particulates and/or by-products of the iron reduction process, and then pass cooling unit 310 (e.g., compressor or a series of compressors) and be combined with reactant feed stream 312. The amount of hydrocarbon, CO.sub.2, CO, and hydrogen can be adjusted based to control the molar ratio of H.sub.2/CO. The combined stream can pass through heat recovery system 306, and then enter bi-reformer unit 302 to continue the cycle. As shown in the FIG. 3, the fuel value depleted gas (recycle stream 324) is recycled to the reformer along with additional natural gas. Along the path, the excess moisture in the depleted gas is removed to obtain the feed desired composition of 14 to 16 vol. % CO, 12 to 14 vol. % CO.sub.2, 32 to 36 vol. % H.sub.2, 16.5 to 19.5 vol % H.sub.2O, 14 to 18 vol. % CH.sub.4, and 3.5 to 4.5 vol. % N.sub.2.

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 Catalysts

[0059] Metal precursor salts used for the catalyst of the present invention include, RhCl.sub.3, H.sub.2PtCl.sub.6, NiCl.sub.3.6H.sub.2O, La(NO.sub.3).sub.3.6H.sub.2O, NbCl.sub.3, InCl.sub.3.4H.sub.2O, (NH.sub.4).sub.2Ce(NO.sub.3).sub.6. All chemicals were purchased from SigmaMillipore (USA) and used as received. MgAl.sub.2O.sub.4 extrudates 2 mm diameter and 5 mm long and with various amount of MgO were supplied by Pacific Industrial Development Company (PIDC) (Germany). All gases used has a purity of 99.999 vol. %.

[0060] Step 1: Cerium ammonium nitrate (2.38 g) and niobium chloride (0.0872 g) were dissolved in deionized water (2.83 mL). The resultant solution was impregnated with MgAl.sub.2O.sub.4 extrudates (5.0 g). 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 h followed by calcination at 550° C. for 3 h. The resultant material was yellowish in color.

[0061] Step 2: Nickel chloride hexahydrate (0.911 g) was weighed and dissolved in deionized water (1.63 mL). The resultant solution was slowly impregnated with material (3 g) obtained in Step 1. The material was dried at 120° C. for 2 h and calcined at 850° C. for 4 h.

[0062] Catalysts with 1 wt. % In, 1 wt. % Ga, and 1 wt. % La dopants were prepared by following similar protocols as explained above, with the dopant metal salt added in Step 1. Catalyst with active metals Pt or Rh were prepared by replacing rhodium chloride with chloroplatinic acid. Table 1 is a list of catalysts prepared and tested, where MgAl stands for MgAl.sub.2O.sub.4.

TABLE-US-00001 TABLE 1 Catalyst Composition Ni/Nb—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % Nb + 7.5 wt. % Ni + 76.5 wt. % MgAl.sub.2O.sub.4 Ni/Ga—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % Ga + 7.5 wt. % Ni + 76.5 wt. % MgAl.sub.2O.sub.4 Ni/La—CeO.sub.2 15 wt. % CeO.sub.2 + 1 wt. % La + 7.5 wt. % Ni + 76.5 wt. % MgAl.sub.2O.sub.4 Ni/In—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 7.5 wt. % Ni + 76.5 wt. % MgAl.sub.2O.sub.4 Ni/CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 7.5 wt. % Ni + 77.5 wt. % MgAl.sub.2O.sub.4 NiRh/Nb—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Nb + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiRh/Bi—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Bi + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiRh/Ga—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Ga + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiRh/La—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % La + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiRh/In—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % In + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiRh/CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 2.5 wt. % Rh + 7.5 wt. % Ni + 75 wt. % MgAl.sub.2O.sub.4 NiPt/Nb—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Nb + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiPt/Bi—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Bi + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiPt/Ga—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % Ga + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiPt/La—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % La + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiPt/In—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.43 wt. % In + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % MgAl.sub.2O.sub.4 NiPt/CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 2.5 wt. % Pt + 7.5 wt. % Ni + 75 wt. % MgAl.sub.2O.sub.4 Ni0.1Pt/In—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.0 wt. % In + 0.1 wt. % Pt + 15 wt. % Ni + 68.9 wt. % MgAl.sub.2O.sub.4 Ni15/In—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1.0 wt. % In + 15 wt. % Ni + 69 wt. % MgAl.sub.2O.sub.4 Ni/InLa—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1 wt. % La 7.5 wt. % Ni + 75.5 wt. % MgAl.sub.2O.sub.4 Ni/InNb—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1% Nb 7.5 wt. % Ni + 75.5 wt. % MgAl.sub.2O.sub.4 Ni/InZr—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1% Zr 7.5 wt. % Ni + 75.5 wt. % MgAl.sub.2O.sub.4 Ni/InSn—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1% Sn 7.5 wt. % Ni + 75.5 wt. % MgAl.sub.2O.sub.4 Ni/Nb—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1 wt. % Nb + 7.5 wt. % Ni + 76.5 wt. % Al.sub.2O.sub.3 Ni/Ga—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1 wt. % Ga + 7.5 wt. % Ni + 76.5 wt. % Al.sub.2O.sub.3 Ni/La—CeO.sub.2 15 wt. % CeO.sub.2 + 1 wt. % La + 7.5 wt. % Ni + 76.5 wt. % Al.sub.2O.sub.3 Ni/In—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1 wt. % In + 7.5 wt. % Ni + 76.5 wt. % Al.sub.2O.sub.3 Ni/CeO.sub.2—Al 15 wt. % CeO.sub.2 + 7.5 wt. % Ni + 77.5 wt. % Al.sub.2O.sub.3 NiRh/Nb—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Nb + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiRh/Bi—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Bi + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiRh/Ga—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Ga + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiRh/La—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % La + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiRh/In—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % In + 2.5 wt. % Rh + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiRh/CeO.sub.2—Al 15 wt. % CeO.sub.2 + 2.5 wt. % Rh + 7.5 wt. % Ni + 75 wt. % Al.sub.2O.sub.3 NiPt/Nb—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Nb + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiPt/Bi—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Bi + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiPt/Ga—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % Ga + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiPt/La—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % La + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiPt/In—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.43 wt. % In + 2.5 wt. % Pt + 7.5 wt. % Ni + 73.57 wt. % Al.sub.2O.sub.3 NiPt/CeO.sub.2—Al 15 wt. % CeO.sub.2 + 2.5 wt. % Pt + 7.5 wt. % Ni + 75 wt. % Al.sub.2O.sub.3 Ni0.1Pt/In—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.0 wt. % In + 0.1 wt. % Pt + 15 wt. % Ni + 68.9 wt. % Al.sub.2O.sub.3 Ni15/In—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1.0 wt. % In + 15 wt. % Ni + 69 wt. % Al.sub.2O.sub.3 Ni/InLa—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1 wt. % In + 1 wt. % La 7.5 wt. % Ni + 75.5 wt. % Al.sub.2O.sub.3 Ni/InNb—CeO.sub.2—Al 15 wt. % CeO.sub.2 + 1 wt. % In + 1 wt. % Nb 7.5 wt. % Ni + 75.5 wt. % Al.sub.2O.sub.3 Ni/InZr—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1 wt. % Zr 7.5 wt. % Ni + 75.5 wt. % Al.sub.2O.sub.3 Ni/InSn—CeO.sub.2—MgAl 15 wt. % CeO.sub.2 + 1 wt. % In + 1 wt. % Sn 7.5 wt. % Ni + 75.5 wt. % MgAl.sub.2O.sub.4

Example 2

Characterization of Catalysts

[0063] FIGS. 4A and 4B show the Scanning transmission electron micrograph (STEM) of γ-Al.sub.2O.sub.3 calcined at 850° C. for 4 hours and Energy dispersive X-ray diffraction spectrum (EDX). The analysis showed that sample contains only ‘Al’ and ‘O’ elements. The analysis was extended to sample containing 1 wt. % In/25 wt. % CeO.sub.2/γ-Al.sub.2O.sub.3 and found that multi-layer of CeO.sub.2 has covered Al.sub.2O.sub.3(FIGS. 5A and 51B). Presence of the CeO.sub.2 layer was indicated via increased brightness as molecular weight of Ce is more than that of Al. In addition, the presence was confirmed by EDX analysis. 10-15 wt. % CeO.sub.2 loading was not enough to distinguish between CeO.sub.2 and Al.sub.2O.sub.3 via brightness, but about 25 wt. % was sufficient to form multi-layer of CeO.sub.2, which enabled distinction between two different oxide layers, i.e., CeO.sub.2 and Al.sub.2O.sub.3. Moreover, due to low loading of ‘In’ in the CeO.sub.2, phase it was not identifiable in spot EDX analysis. FIGS. 6A and 6B show STEM and EDX for of 8 wt. % Ni/25 wt. % CeO.sub.2/7-Al.sub.2O.sub.3 catalyst sample. The image showed that the Ni particle are sitting on the CeO.sub.2 layer and difficult to identify by mere comparing brightness. However, EDX analysis on the spherical particles confirmed the particles were indeed metallic ‘Ni’ and located specifically on CeO.sub.2 layer.

Example 3

Bi-Reforming of Methane

[0064] Catalysts testing was performed in a high throughput reactor system supplied by Avantium BV (Netherlands). Reactors were of plug flow type and made up of steel, with an inner quartz liner. The quartz liner with 4 mm in inner diameter and 60 cm in length was used to avoid coking due to methane cracking on steel surface. Catalyst pellets were crushed and sieved between 300-500 μm. Catalyst sieve fraction was placed on top of inert material inside the quartz liner. A feed gas mixture of 13% CO.sub.2+16% CH.sub.4+34% H.sub.2+18% H.sub.2O+15% CO+4% Ar was made by mixing pure gases and evaporating water. Argon was used as an internal standard for Mass spectrometric analysis. The catalyst in oxidized state was heated to 800° C. in the presence of 100% Ar and they actual gas mixture feed was passed over the catalyst bed. A mass spectrometer from Thermo Scientific Model Thermo BT was used for gas analysis. Methane conversion was calculated as follows.

[00001]$\mathrm{Methane}\mathrm{conversion}=\frac{\mathrm{mol}\mathrm{of}\mathrm{methane}\mathrm{converted}}{\mathrm{mol}\mathrm{of}\mathrm{methane}\mathrm{in}\mathrm{feed}}\times 100$

The ratio of hydrogen to carbon monoxide is calculated as follows,

[00002]$H2/\mathrm{CO}=\frac{\mathrm{mol}\mathrm{of}\mathrm{Hydrogen}\mathrm{in}\mathrm{product}}{\mathrm{mol}\mathrm{of}\mathrm{carbon}\mathrm{monoxide}\mathrm{in}\mathrm{product}}\times 100$

[0065] During the plant start up, usually a mixture of N.sub.2 and CO.sub.2 flows through the catalyst bed while temperature in the latter ramps up. Usually the fresh catalyst was in oxidized state, which reduced to metallic state during initial stages of reforming when CH.sub.4 gas replaces portion of CO.sub.2 and N.sub.2. It was crucial that catalyst withstands high concentration of CO.sub.2 and adjusts to changing redox gas atmosphere during start-up phase. Table 2 gives the variation of feed composition at different stages of temperature ramp. Three catalysts were chosen for study and were subjected to same feed and reaction conditions. Experiments were started from 550° C. with 60% CO.sub.2 in the feed. Gradually, temperature was increased to 600° C., 650° C., 700° C., 750° C. and 800° C. with incremental addition of CH.sub.4 in the feed, while replacing CO.sub.2. In addition, at 800° C. as a final check, actual reformer feed was fed and catalyst performance was monitored. As expected, all three catalysts underwent in-situ reduction and activation. Ni/In—Ce/Al.sub.2O.sub.3 showed better performance than commercial catalysts in all conditions (FIGS. 7 and 8), the H.sub.2/CO ratio was also better for former than latter (FIG. 9). Ni/In—Ce/MgAl.sub.2O.sub.4 showed sluggish performance as the catalyst activation takes place only around 780° C., whereas both Commercial and (Ni/In—Ce/Al.sub.2O.sub.3) activate around 400° C. At higher temperature>850° C. the performance of both (Ni/In—Ce/Al.sub.2O.sub.3) and (Ni/In—Ce/MgAl.sub.2O.sub.4) was expected to be same since both catalyst activate below 800′° C.

TABLE-US-00002 TABLE 2 Feed gas composition Time, Temp., CO.sub.2, CH.sub.4, He, H.sub.2, CO, H.sub.2O, Steps h ° C. Vol %. Vol. % Vol. % Vol. % Vol. % Vol % 1 2 550 60 0 40 2 4 550 60 0 40 3 6 550 60 0 40 4 8.5 600 50 10 40 5 10.5 600 50 10 40 6 11.5 600 50 10 40 7 14 650 40 20 40 8 16 650 40 20 40 9 18 650 40 20 40 10 20.5 700 30 30 40 11 23.5 700 30 30 40 12 25.5 700 30 30 40 13 28 800 20 20 40 20 14 30 800 20 20 40 20 15 32 800 20 20 40 20 16 34.5 800 11 13 18 28 12 18 17 36.5 800 11 13 18 28 12 18 18 38.5 800 11 13 18 28 12 18

[0066] Table 3 gives the % CH.sub.4 conversion, H.sub.2/CO ratio obtained with different catalysts after 600 hours of time on stream (TOS). Commercial and core-shell catalyst possess almost same conversion. H.sub.2/CO ratio in the product gas is in acceptable range and can be varied by varying reaction parameters. Ni/In—CeO.sub.2—MgAl and Ni/Nb—CeO.sub.2—MgAl based catalyst did not show carbon over 1200 hours time on stream. At similar conditions Ni/La—CeO.sub.2—MgAl based and Commercial catalyst showed the presence of coke.

TABLE-US-00003 TABLE 3 Catalyst GHSV, h.sup.−1 H.sub.2/CO % CH.sub.4 conversion Commercial Catalyst 56000 1.86 94 Ni—NbCeO.sub.2—MgAl 56000 1.93 96 Ni—LaCeO.sub.2—MgAl 56000 1.78 86 Ni—InCeO.sub.2—MgAl 29146 1.70 85

[0067] The quality of syngas further tested and compared with commercial and Ni—InCeO.sub.2—Al catalyst at 800° C. and 70,000 h-1 space velocity and the results are given in Table 4. The performance and quality of syngas was found to be better in case core-shell catalyst than commercial catalyst probably because of better metal dispersion and interaction of Ni with CeO.sub.2 due to strong metal-support interaction effects.

TABLE-US-00004 TABLE 4 Syngas composition Feed Commercial conc. catalyst Ni—InCeO.sub.2—Al H.sub.2 34 26.2 42.4 CO 15 19.9 29.2 CO.sub.2 13 4.5 0.4 Ar 4 22.4 18.9 CH.sub.4 16 13.3 4.6 H.sub.2O 18 13.7 4.4 H.sub.2/CO 1.3 1.5 % X(CH.sub.4) 16.9 71.1

Example 4

Characterization of Spent Catalysts and Coke Evaluation

[0068] Spent catalysts were characterized by powder X-ray diffraction. FIG. 10 shows X-ray diffraction patterns of spent catalysts from the bi-reforming reaction. The dotted line gives the peak for carbon/coke in the catalysts. It is obvious from the diffraction patterns that commercial catalyst and Ni/La—CeO.sub.2—MgAl catalysts contain carbon however; Ni/In—CeO.sub.2—MgAl catalyst is free from any carbon. This is also supported by TPO studies mentioned in earlier section. To ascertain the coke formation, the spent catalysts from bi-reforming reaction were analyzed using temperature programmed oxidation process. The samples were analyzed using TPD Autochem II 2920 instrument supplied by Micromertics. Samples were temperature ramped at 10° C./min in 20% O.sub.2+80% N.sub.2 gas atmosphere. Thermal conductivity analyzer analyzed the difference thermal conductivity that is in present case directly proportional to amount of CO.sub.2+CO formed due to oxidation of coke on the catalysts. As shown in FIG. 10, the commercial spent catalyst showed a peak around 600° C. while Ni deposited on InCeO.sub.2-shell, MgAl.sub.2O.sub.4-core catalyst did not show any peak, which proves that latter is free from any coke demonstrating that the Ni deposited on CeO.sub.2-shell-MgAl.sub.2O.sub.4-core is superior. This is because MgAl.sub.2O.sub.4 is fully covered by CeO.sub.2 and Ni is deposited solely on CeO.sub.2 layer.

[0069] Accelerated coking studies were conducted to ascertain the de-coking capacity of the core-shell and commercial catalysts. Two core-shell nature catalysts and one commercial catalyst have been considered and subjected to reformer reaction conditions. The feed composition was H.sub.2=34%, CO=15%, CO.sub.2=13%, Ar=4%, CH.sub.4=16%, H.sub.2O=18%. Initially catalysts were exposed to reformer feed conditions at 800° C. and 1 bar (0.1 MPa) pressure for 300 hours, then the temperature was decreased to 700° C. and reaction was continued. At about 470 h the temperature was further decreased to 600° C. and reactor pressure was monitored. After about 510 h the pressure inside the reactor started to increase as shown in the FIG. 12. The pressure drop is directly proportional to amount of coke formed and restriction caused by coke for gas flow. It is clear from graph in FIG. that commercial catalyst cokes faster than core-shell catalyst. Moreover, Ni/In—CeO.sub.2—MgAl catalyst showed almost negligible amount of pressure drop, however, Ni/La—CeO.sub.2—MgAl did show pressure drop but much lesser than commercial catalyst.

[0070] In summary, the catalysts of the present invention based on core-shell structure (example Ni/InCeO.sub.2/Al) showed better performance than Commercial catalysts in all conditions, the H.sub.2/CO ratio was also better for former than latter. Catalyst supported on MgAl.sub.2O.sub.4 (example: Ni/InCe/MgAl.sub.2O.sub.4) possess higher activation i.e., −780° C. temperature than supported on Al.sub.2O.sub.3 example: Ni/InCeO.sub.2/Al.sub.2O.sub.3 activate around 400° C. At higher temperature (>850° C.) the performance of both (Ni/InCeO.sub.2/Al) and (Ni/InCeO.sub.2/MgAl.sub.2O.sub.4) was expected to be same since both catalyst activated below 800° C. Under actual bi-reformer conditions, over 1200° C., coking was observed in the Commercial catalyst, both visually and TPO studies. Coking was not observed in catalyst of the present invention.