WO2018203836A1

WO2018203836A1 - Method of preparing a metal-silicon oxide catalyst

Info

Publication number: WO2018203836A1
Application number: PCT/SG2018/050222
Authority: WO
Inventors: Sibudjing Kawi; Ashok Jangam; Zhoufeng BIAN; Zhigang Wang
Original assignee: National University Of Singapore
Priority date: 2017-05-05
Filing date: 2018-05-04
Publication date: 2018-11-08

Abstract

A method for preparing a metal-silicon oxide catalyst is provided, wherein said metal-silicon oxide catalyst is in one or more of the following forms: a) metal on silicon dioxide; b) metal phyllosilicate on silicon dioxide; c) metal on metal phyllosilicate; d) metal phyllosilicate on metal phyllosilicate; and e) metal phyllosilicate. The method comprises a) mixing a metal precursor with a silicon oxide precursor in an aqueous mixture comprising ammonia and having a pH of at least 12 to form a reaction mixture, and b) hydrothermally treating the reaction mixture. A metal-silicon oxide catalyst, and use of the metal-silicon oxide catalyst in reforming of light hydrocarbon reactions for the production of synthesis gas are also provided.

Description

METHOD OF PREPARING A METAL-SILICON OXIDE CATALYST

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of US provisional application No. 62/501,751 filed on 5 May 2017, the content of which is incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

[0002] Various embodiments relate to a method for preparing a metal-silicon oxide catalyst, a metal-silicon oxide catalyst, and use of the catalyst in reforming of light hydrocarbon reactions for the production of synthesis gas.

BACKGROUND

[0003] Synthesis gas, otherwise known as "syngas", is a gaseous combination of hydrogen and carbon monoxide which is a very important feedstock of many petrochemical processes, such as the synthesis of ammonia and methanol, and the Fischer- Tropsch synthesis of liquid hydrocarbons.

[0004] Syngas may be converted from feedstock of natural gas and/or other hydrocarbon gases in catalytic reactors termed as fuel reformers via processes of steam reforming, dry reforming (using C0₂), autothermal operations, or partial oxidation. In a typical steam methane reformer operation for the production of syngas, for example, natural gas may be pretreated to remove sulfur. The desulfurized feed may then be mixed with steam and reformed in the steam methane reformer (SMR) to produce syngas. Dry reforming, on the other hand, uses carbon dioxide instead of steam for the production of syngas.

[0005] Catalysts used in the fuel reformers are prone to carbon deposition which may, for example, be in the form of fouling on support, carbon encapsulation of active metal, and carbon fiber/nanotube formation. This results in loss of active sites on the catalysts, which shortens their life-span. Nickel-based catalysts, for example, suffer from problems relating to catalyst deactivation caused by carbon deposition and metal sintering. Although cobalt-based catalysts have shown improved tolerance to carbon deposition, oxidation of the metallic cobalt results in rapid deactivation of the catalyst. Catalysts containing noble metals such as ruthenium (Ru), rhodium (Rh) and platinum (Pt) have shown high conversion and good resistance to carbon deposition. However, they are not practical for use on an industrial level due to their high costs.

[0006] In view of the above, there exists a need for improved catalysts and methods of preparing catalysts that address or at least alleviate one or more of the above-mentioned problems.

SUMMARY

[0007] In a first aspect, a method for preparing a metal-silicon oxide catalyst is provided. The method comprises a) mixing a metal precursor with a silicon oxide precursor in an aqueous mixture comprising ammonia and having a pH of at least 12 to form a reaction mixture, and b) hydrothermally treating the reaction mixture.

[0008] In a second aspect, a metal-silicon oxide catalyst is provided. The metal is present in an elemental weight percent of 5 % to 35 % and silicon is present in an elemental weight percent of 15 % to 65 % of the catalyst.

[0009] In a third aspect, use of a metal-silicon oxide catalyst prepared by a method according to the first aspect or a metal- silicon oxide catalyst according to the second aspect in reforming of light hydrocarbon reactions for the production of synthesis gas is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

[0011] FIG. 1 is a graph depicting steam reform of methane (CH₄) (SRM) activity over 15 wt% Ni-SiC -MgO catalyst, measured in terms of methane conversion (%) and hydrogen gas/carbon monoxide ratio (H₂/CO) against time on stream (h). Conditions: CH₄ = 20 mL/min, helium (He) = 30 mL/min, steam-to-carbon ratio (S/C) = 1.5, reactant gas flow rate/reactor volume (GHSV) = 140 L/h.g and reaction temperature = 750 °C.

[0012] FIG. 2A is a graph depicting SRM performances of 15 wt% Ni-Si -MgO catalyst at various steam-to-carbon ratio (S/C) conditions of 1.2, 1.5 and 2.0 for methane conversion (%) against time on stream (h). Conditions: CH₄ = 20 mL/min, He = 30 mL/min, and reaction temperature = 750 °C. [0013] FIG. 2B is a graph depicting SRM performances of 15 wt% Ni-Si h-MgO catalyst at various steam-to-carbon ratio (S/C) conditions of 1.2, 1.5 and 2.0 for H₂/CO values against time on stream (h). Conditions: CH₄ = 20 mL/min, He = 30 mL/min and reaction temperature = 750 °C.

[0014] FIG. 3 is a graph depicting SRM performances of Ni-Si02-MgO(x) catalysts, measured in terms of methane conversion (%) against time on stream (h). Conditions: CH₄ = 20 mL/min, He = 30 mL/min, S/C = 1.5, GHSV = 140 L/h.g, and reaction temperature = 750 °C.

[0015] FIG. 4 is a graph depicting steam reforming of methane activity over 20 wt% Ni- SiC -MgO catalyst, measured in terms of methane conversion (%) and H2/CO against time on stream (h). Conditions: CH₄ = 20 mL/min, He = 30 mL/min, S/C = 1.5, GHSV = 194 L/h.g, and reaction temperature = 750 °C.

[0016] FIG. 5A is a graph depicting differential thermal analysis (DTA) profile (rate of weight loss, dm/dT) and thermogravimetric analysis (TGA) profile (weight loss, mg) against temperature (°C) of spent Ni-Si -MgO catalysts after steam reforming of methane as in FIG. 1.

[0017] FIG. 5B is a graph depicting DTA profile (rate of weight loss, dm/dT) and TGA profile (weight loss, mg) against temperature (°C) of spent Ni-Si -MgO catalysts after steam reforming of methane as in FIG. 4.

[0018] FIG. 6 is a graph depicting combined reforming of methane activity over 15 wt% Ni-Si02-MgO catalyst, measured in terms of methane conversion (%), carbon dioxide (CO2) conversion (%), and H2/CO against time on stream (h). Conditions: CH₄ = 20 mL/min, CO2 = 10 mL/min, He = 30 mL/min, S/C = 1.0, GHSV = 140 L/h.g, and reaction temperature = 750 °C.

[0019] FIG. 7 is a graph depicting combined reforming of methane over Ni-Si -MgO (3.5) catalyst, measured in terms of methane conversion (%), CO2 conversion (%), and H2/CO against time on stream (h). Conditions: CH₄ = 20 mL/min, CO2 = 10 mL/min, He = 30 mL/min, S/C = 1.0, GHSV = 96 L/h.g, and reaction temperature = 750 °C.

[0020] FIG. 8 is a graph depicting combined reforming of methane over Ni-Si -MgO (1) catalyst, measured in terms of methane conversion (%), CO2 conversion (%), and H2/CO against time on stream (h). Conditions: CH₄ = 20 mL/min, CO2 = 10 mL/min, He = 30 mL/min, S/C = 1.0, GHSV = 192 L/h.g, and reaction temperature = 750 °C. [0021] FIG. 9A is a graph depicting DTA profile (rate of weight loss, dm/dT) and TGA profile (weight loss, mg) against temperature (°C) of spent Ni-Si0₂-MgO catalysts after steam reforming of bio-gas as in FIG. 6.

[0022] FIG. 9B is a graph depicting DTA profile (rate of weight loss, dm/dT) and TGA profile (weight loss, mg) against temperature (°C) of spent Ni-Si0₂-MgO catalysts after steam reforming of bio-gas as in FIG. 7.

[0023] FIG. 10 is a graph depicting temperature-programmed reduction (TPR) profiles of Ni/MgO ("Ni-MgO") and Ni-Si0₂-MgO catalysts of lONi-Ps-Mg, 15Ni-Ps-Mg, and 20Ni-Ps- Mg.

[0024] FIG. 11 is a graph depicting C0₂ reforming of methane activity over 15 wt% Ni- Si0₂ catalyst, measured in terms of methane conversion (%), C0₂ conversion (%), and H₂/CO ratio against time on stream (h). Conditions: CH₄ = 10 mL/min, C0₂ = 10 mL, He = 30 mL/min, GHSV = 194 L/h.g and reaction temperature = 750 °C.

[0025] FIG. 12 is a graph depicting C0₂ reforming of methane activity over 7 wt% Ni-3 wt% C0-S1O2 catalyst, measured in terms of methane conversion (%), C0₂ conversion (%), and H2/CO ratio against time on stream (h). Conditions: CH₄ = 10 mL/min, C0₂ = 10 mL, He = 30 mL/min, GHSV = 194 L/h.g and reaction temperature = 750 °C.

[0026] FIG. 13 is a graph depicting DTA/TGA profiles of spent Ni-Co-Si0₂ catalysts after C0₂ reforming of methane as in FIG. 12.

[0027] FIG. 14A is a transmission electron microscopy (TEM) image of freshly calcined catalysts of lONi. Scale bar denotes 30 nm.

[0028] FIG. 14B is a TEM image of freshly calcined catalysts of 7Ni3Co. Scale bar denotes 20 nm.

[0029] FIG. 14C is a TEM image of freshly calcined catalysts of 5Ni5Co. Scale bar denotes 30 nm.

[0030] FIG. 14D is a TEM image of freshly calcined catalysts of 3Ni7Co. Scale bar denotes 30 nm.

[0031] FIG. 14E is a TEM image of freshly calcined catalysts of lOCo. Scale bar denotes 30 nm.

[0032] FIG. 15 are TEM images of spent 7 wt% Ni-3 wt% C0-S1O2 catalyst after C0₂ reforming of methane as in FIG. 12. Scale bar in left figure denotes 50 nm; scale bar in right figure denotes 40 nm. [0033] FIG. 16 is a graph depicting H₂-temperature programmed reduction (H₂-TPR) profiles of freshly calcined Ni-Co-Si0₂ catalysts of lONi, 7Ni3Co, 5Ni5Co, 3Ni7Co, and lOCo.

[0034] FIG. 17 is a graph depicting X-ray diffraction profile (XRD) profiles of Cu/Si0₂ catalysts prepared via a conventional impregnation route for comparison purposes, and a phyllosilicate route according to an embodiment disclosed herein. Referring to the figure, the Cu/Si0₂ catalyst prepared using the impregnation method has intense diffractions at around 2theta = 35 and 39, which shows that the crystallite size of CuO is very big. On the other hand, for Cu/Si0₂ catalyst prepared using ammonia evaporation method, it does not have such intense diffractions, which means the crystallite size of CuO is very small and well distributed.

[0035] FIG. 18 is a TEM image of as- synthesized Cu-PS catalyst prepared via a phyllosilicate route according to an embodiment disclosed herein.

[0036] FIG. 19 are TEM images of NiCo-Si0₂ and NiCo-Si0₂-Ce0₂.

[0037] FIG. 20A is a graph depicting toluene conversion and production rate of H₂, CO, C0₂ and CH₄.

[0038] FIG. 20B is a graph depicting TGA result.

[0039] FIG. 21A is a TEM image of Ni-Ps.

[0040] FIG. 21B is a TEM image of Ni-Ps .

[0041 ] FIG. 21C is a TEM image of Ni-Ps-Ce0₂.

[0042] FIG. 21D is a TEM image of Ni-Ps-Ce0₂.

[0043] FIG. 22A is a graph depicting X-ray photoelectron spectrum (XPS) of Ni@NiPhy and Ni@NiPhy@Ce0₂ for Ce 3d.

[0044] FIG. 22B is a graph depicting X-ray photoelectron spectrum of Ni@NiPhy and Ni@NiPhy@Ce0₂ for O Is.

[0045] FIG. 22C is a graph depicting X-ray photoelectron spectrum of Ni@NiPhy and Ni@NiPhy@Ce0₂ for Ni 2p.

[0046] FIG. 22D is a graph depicting X-ray photoelectron spectrum of Ni@NiPhy and Ni@NiPhy@Ce0₂ for Si 2p.

[0047] FIG. 23A is a graph depicting C0₂ and CH₄ specific activities of different catalysts for dry reforming reaction of methane (DRM) reaction under different reaction conditions. Reaction conditions: 700 °C, GHSV = 1880 L-g^cat-h ¹, W_cat = 0.01 g, C0₂:CH₄:He = 1: 1: 1.

[0048] FIG. 23B is a graph depicting H₂/CO ratio of different catalysts for DRM reaction under different reaction conditions. Reaction conditions: 700 °C, GHSV = 1880 L-g^-1cat-h^-1, Wcat = 0.01 g, C0₂:CH₄:He = 1: 1: 1.

[0049] FIG. 23C is a graph depicting C0₂ and CH₄ specific activities of different catalysts for DRM reaction under different reaction conditions. Reaction conditions: 600 °C, GHSV = 36 L-g^cat-h ¹, Wcat = 0.05 g, C0₂:CH₄:He = 1: 1: 1.

[0050] FIG. 23D is a graph depicting H₂/CO ratio of different catalysts for DRM reaction under different reaction conditions. Reaction conditions: 600 °C, GHSV = 36 L-g^cat-h ¹, Wcat = 0.05 g, C0₂:CH₄:He = 1: 1: 1.

[0051] FIG. 24 is a graph depicting TGA-DTA profiles for different catalysts after DRM reaction. Reaction conditions: 700 °C, GHSV = 1880 L-g^cat-h ¹, Wcat = 0.01 g, C0₂:CH₄:He = 1: 1: 1.

DETAILED DESCRIPTION

[0052] Various embodiments relate to mono-metallic or bi-metallic silicon oxide catalysts, mono-metallic or bi-metallic silicon oxide-metal oxide catalysts, methods of preparing the catalysts, and use of the catalysts in reforming of light hydrocarbon reactions for the production of synthesis gas.

[0053] In various embodiments, the metal-silicon oxide catalyst comprises a metallic species in the form of metal and/or metal phyllosilicate on a silicon oxide support. The silicon oxide support may comprise or consist of a silicon oxide, such as silicon oxide (SiO), silicon dioxide (Si0₂) and/or a metal phyllosilicate. In various embodiments, the silicon oxide support comprises or consists of silicon dioxide and/or metal phyllosilicate. Accordingly, the metal-silicon oxide catalyst disclosed herein may be in one or more of the following forms: metal on silicon dioxide; metal phyllosilicate on silicon dioxide; metal on metal phyllosilicate; metal phyllosilicate on metal phyllosilicate; metal phyllosilicate. The metal and/or the metal phyllosilicate may constitute an active phase of the catalyst. In embodiments wherein the silicon oxide support comprises metal phyllosilicate, the metal phyllosilicate that is comprised in the silicon oxide support may also function as an active phase of the catalyst, and which may be activated by reduction in hydrogen gas. [0054] Physico-chemical characteristics based on tests carried out on the fresh and reduced catalysts disclosed herein have shown that the metallic species have strong interactions with the silicon oxide, which translates into stabilization of the metallic species on the silicon oxide support. This stabilization enables the metallic species which may be in the form of metal and/or metal phyllosilicate to perform efficiently in dry reforming of hydrocarbon for syngas production. In some embodiments, highly active and stable Ni-based anti-coking catalyst for steam reforming of methane/bio-gas reaction is provided.

[0055] In embodiments wherein the silicon oxide support further comprises a metal oxide, the metallic species may have strong interactions with the metal oxide as well. The metallic species may be stabilized within the matrix of silicon oxide-metal oxide, such as Si -MgO or CaO composite sub-surface. This stabilization enables the metallic species which may be in the form of metal and/or metal phyllosilicate to perform efficiently in both dry reforming and steam reforming of hydrocarbon for syngas production. As demonstrated herein, the mono-metallic or bi-metallic silicon oxide-metal oxide catalysts are highly active and stable for steam reforming, dry reforming, or combined reforming of light hydrocarbons and biogas reactions for syngas production with negligible carbon deposition.

[0056] The catalysts disclosed herein may also be highly active and stable for high- temperature water-gas-shift reaction for hydrogen-rich syngas production.

[0057] Advantageously, the catalysts according to embodiments disclosed herein involve use of metallic species formed from metals such as nickel (Ni), cobalt (Co), copper (Cu), and/or iron (Fe) which are cheap and widely available as active phase, thereby avoiding use of noble metals which are high in cost. Uniform bi-metallic catalysts, such as Ni-Co, Ni-Fe, Ni-Cu, Co-Cu, Co-Fe, Cu-Fe-based bi-metallic catalysts, may be prepared using a method disclosed herein thereby widening catalytic applications via use of the bi-metallic catalysts. Furthermore, the catalysts disclosed herein are able to mitigate the high steam to carbon ratio requirements of conventional steam reforming processes, as they have demonstrated good performance at lower steam to carbon ratios of almost 2/3 to half of that used presently. Mid to low reforming temperatures of 750 °C or less may be used for the reforming processes such as steam reforming, dry reforming, or combined reforming of light hydrocarbons. These translate into more energy efficient reforming processes, which greatly reduce costs of production. [0058] With the above in mind, various embodiments refer in a first aspect to a method for preparing a metal-silicon oxide catalyst.

[0059] As used herein, the term "catalyst" refers to a substance which increases a rate of reaction thereby promoting the reaction without itself being consumed in the reaction. The active phase, meaning the catalytically active component, of the metal-silicon oxide catalyst may be formed from metallic species such as a metal and/or a metal phyllosilicate. The metallic species may be present on a silicon oxide support comprising or consisting of a silicon oxide, such as silicon dioxide and/or a metal phyllosilicate. The silicon dioxide and/or metal phyllosilicate may function as a carrier for the metallic species, which may be affixed onto or embedded within the silicon oxide support.

[0060] Accordingly, the metal-silicon oxide catalyst disclosed herein may assume one or more of the following forms: metal on silicon dioxide; metal phyllosilicate on silicon dioxide; metal on metal phyllosilicate; metal phyllosilicate on metal phyllosilicate; metal phyllosilicate.

[0061] In embodiments wherein the metallic species and the silicon oxide are independently metal phyllosilicates, the metal phyllosilicate making up the metallic species and the metal phyllosilicate making up the silicon oxide support may be the same or different. Accordingly, the metal-silicon oxide catalyst may be in the form of a metal phyllosilicate when the metal phyllosilicates of the metallic species and the silicon oxide are the same. In embodiments wherein the metal phyllosilicate making up the metallic species and the metal phyllosilicate making up the silicon oxide support are different, the metal-silicon oxide catalyst may be in the form of a metal phyllosilicate as metallic species on a metal phyllosilicate as a silicon oxide support. Advantageously, the metal phyllosilicate comprised in the silicon oxide support may also function as an active phase of the catalyst.

[0062] As mentioned above, the metallic species may be selected from the group consisting of a metal, a metal phyllosilicate, and a combination thereof. In various embodiments, the metal and/or metal of the metal phyllosilicate may be selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), and a combination thereof. The metal and/or metal of the metal phyllosilicate may, for example, be an alloy of the afore-mentioned metals, such as an alloy of Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, or Cu- Fe. Accordingly, in embodiments wherein the metal and/or metal of the metal phyllosilicate comprises two different metals, the metal-silicon oxide catalyst may be a bi-metallic silicon oxide catalyst.

[0063] In various embodiments, the metal and/or metal of the metal phyllosilicate is selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe. Accordingly, the metal may be selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe, while the metal phyllosilicate may be selected from the group consisting of NiPs, CoPs, CuPs, FePs, NiCuPs, NiCoPs, NiFePs, CoCuPs, CoFePs, and CuFePs, whereby "Ps", alternatively termed herein as "PS" or "Phy", denotes phyllosilicate.

[0064] The method may comprise mixing a metal precursor with a silicon oxide precursor in an aqueous mixture comprising ammonia and having a pH of at least 12 to form a reaction mixture, and hydrothermally treating the reaction mixture.

[0065] The term "precursor" as used herein refers to a compound that may be treated or further processed to form the target material. Accordingly, the term "metal precursor" refers to a compound that may further processed to form the metallic species, and the term "silicon oxide precursor" refers to a compound that may be further processed to form the silicon oxide.

[0066] In various embodiments, the metal precursor comprises a metal selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), and a combination thereof. In some embodiments, the metal precursor comprises a metal selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe. The metal precursor may, for example, be a salt of the above-mentioned metals, and may be provided in the form of an aqueous solution having the salt dissolved therein. The salt may be completely or at least substantially dissolved in the aqueous solution. Generally, any salt of the above- mentioned metals that is able to dissolve in an aqueous solution may be used. In various embodiments, the metal precursor is selected from the group consisting of an acetylacetonate salt, a halide salt, a nitrate salt, a carbonate salt, and mixtures thereof.

[0067] The silicon oxide precursor, on the other hand, may be selected from the group consisting of silica sol, colloidal silica, tetraethoxysilane, zeolite, and a combination thereof. As mentioned above, the silicon oxide may function as a carrier for the metallic species, which may be affixed onto or embedded within the silicon oxide. The silicon oxide may, for example, be silicon oxide (SiO), silicon dioxide, otherwise termed herein as silica (S1O2), or a silicate such as a phyllosilicate. In various embodiments, the silicon oxide support comprises or consists of silica and/or a metal phyllosilicate. The metal phyllosilicate comprised in the silicon oxide support may, for example, be NiPs, CoPs, CuPs, FePs, NiCuPs, NiCoPs, NiFePs, CoCuPs, CoFePs, or CuFePs.

[0068] In mixing the metal precursor with the silicon oxide precursor in an aqueous mixture comprising ammonia and having a pH of at least 12 to form a reaction mixture, the metallic species may be precipitated from the aqueous mixture via an ammonia evaporation method, otherwise termed herein as a phyllosilicate route. Using the method, the ammonia may react with the metal precursor to form a metal complex. By subsequently removing the ammonia via evaporation, a pH decrease of the aqueous mixture may result, with effect that the metallic species may be precipitated from the aqueous mixture, and be deposited on the silicon oxide precursor. As mentioned above, the metallic species may be in the form of a metal and/or a metal phyllosilicate. Some or most of the metal complex in the aqueous mixture may react with the silicon oxide precursor to form metal phyllosilicate while ammonia is being removed via evaporation, whereas some of the metal complex in aqueous mixture may be precipitated as metal nanoparticles on the silicon oxide precursor. Advantageously, uniformly distributed mono or bi-metallic-Si material may be prepared relatively simply via the ammonia evaporation method.

[0069] Although evaporation of ammonia from the aqueous mixture may take place at ambient temperature, mixing the metal precursor with the silicon oxide precursor may be carried out under heating to accelerate the evaporation process. In various embodiments, mixing the metal precursor with the silicon oxide precursor is carried out at a temperature in the range of about 50 °C to about 100 °C, such as about 60 °C to about 100 °C, about 70 °C to about 100 °C, about 80 °C to about 100 °C, about 50 °C to about 90 °C, about 50 °C to about 80 °C, about 50 °C to about 70 °C, about 50 °C to about 60 °C, about 60 °C to about 90 °C, or about 70 °C to about 80 °C.

[0070] The method disclosed herein may further comprise hydrothermally treating the reaction mixture. As used herein, the term "hydrothermal" refers to treatment conditions in a sealed system involving water as the reaction medium and with temperatures and pressures higher than ambient, and usually significantly higher than ambient. The hydrothermal treatment may be carried out to convert all the metallic species in the reaction mixture to metal and/or metal phyllosilicate comprised in the metal-silicon oxide catalyst. [0071] In various embodiments, hydrothermally treating the reaction mixture is carried out at a temperature in the range of about 80 °C to about 200 °C, such as about 100 °C to about 200 °C, about 120 °C to about 200 °C, about 140 °C to about 200 °C, about 160 °C to about 200 °C, about 80 °C to about 180 °C, about 80 °C to about 160 °C, about 80 °C to about 140 °C, about 80 °C to about 120 °C, about 80 °C to about 100 °C, about 100 °C to about 150 °C, or about 120 °C to about 160 °C.

[0072] Hydrothermally treating the reaction mixture may be carried out for at least 12 hours. For example, hydrothermally treating the reaction mixture may be carried out for at least 14 hours, at least 16 hours, at least 18 hours, at least 20 hours, or for a time period in the range of about 12 hours to about 24 hours, such as about 12 hours to about 18 hours, about 12 hours to about 16 hours, or about 12 hours to about 14 hours.

[0073] Hydrothermal treating the reaction mixture may be carried out at a pressure of at least 1 bar, such as at least 2 bars, at least 3 bars, or at least 4 bars, or at a pressure in the range of about 1 bar to about 5 bars, about 1 bar to about 4 bars, about 1 bar to about 3 bars, or about 2 bars to about 4 bars. In various embodiments, hydrothermal treating the reaction mixture is carried out at a pressure of more than 1 bar.

[0074] Following the hydrothermal treatment, a metal-silicon oxide catalyst may be formed. The metal-silicon oxide catalyst may be further reduced in hydrogen gas following hydrothermal treatment to activate the metallic species and/or metal phyllo silicate comprised in the silicon oxide support, or to render the catalyst active for use in a reforming process. The reduction in hydrogen gas may, for example, be carried out during manufacturing of the metal-silicon oxide catalyst, or be carried out in a catalyst reformer prior to use in a reforming process. Accordingly, the metal-silicon oxide catalyst may be activated on-site at a client's reforming plant, for example. The reduction in hydrogen gas may be carried out at a temperature in the range of about 700 °C to about 1000 °C, such as about 750 °C to about 1000 °C, about 800 °C to about 1000 °C, about 850 °C to about 1000 °C, about 700 °C to about 900 °C, about 700 °C to about 800 °C, or about 750 °C to about 850 °C. A metal- silicon oxide catalyst comprising a metallic species as active phase on a silicon oxide support may accordingly be obtained using a method as described above.

[0075] In various embodiments, the method further comprises adding a metal oxide precursor to the reaction mixture before hydrothermally treating the reaction mixture. In so doing, the metal oxide precursor may be reacted with the silicon oxide precursor, so that a metal-silicon oxide-metal oxide catalyst comprising a metallic species as active phase on a silicon oxide-metal oxide support may be obtained. The metal oxide that is in the silicon oxide-metal oxide support may form a solid solution with the silicon oxide. For example, the metal oxide may be uniformly dispersed with the silicon oxide in the silicon oxide-metal oxide support.

[0076] Metal of the metal oxide precursor may be selected from the group consisting of Mg, Ca, Ce, Zr, Al and a combination thereof. The metal oxide precursor may, for example, be selected from the group consisting of an acetylacetonate salt, a halide salt, a nitrate salt, a carbonate salt, and mixtures thereof. The metal oxide precursor may react with the metal- silicon oxide composite to form a metal-silicon oxide-metal oxide composite, or the metal oxide may encapsulate the metal-silicon oxide composite.

[0077] The metal oxide precursor may be added along with an urea salt. During hydrothermal treatment, such as at temperatures of at least 60 °C, ammonia may be produced from the urea salt to render pH of the resultant mixture basic.

[0078] As in the case for the metal-silicon oxide catalyst, the metal-silicon oxide-metal oxide catalyst may be reduced in hydrogen gas to render the catalyst active for use in a reforming process. The reduction in hydrogen gas may be carried out at similar conditions as that used for metal-silicon oxide catalyst as mentioned above. The metal oxide comprised in the silicon oxide-metal oxide support may remain as metal oxide form even after reduction in hydrogen gas, while the metallic species may be reduced or converted to metal. A metal- silicon oxide-metal oxide catalyst comprising a metallic species as active phase on a silicon oxide-metal oxide support may accordingly be obtained using a method as described above.

[0079] Various embodiments refer in a further aspect to a metal-silicon oxide catalyst, or a metal-silicon oxide-metal oxide catalyst prepared by a method disclosed herein.

[0080] Various embodiments refer in further aspects to a metal-silicon oxide catalyst, wherein the metal is present in an elemental weight percent of 5 % to 35 % and silicon is present in an elemental weight percent of 15 % to 65 % of the catalyst. The elemental weight percent may not add up to 100 % since other elements such as oxygen may also be present.

[0081] Suitable metallic species and silicon oxide have already been described above.

[0082] In various embodiments, the metal-silicon oxide catalyst is in one or more of the following forms: metal on silicon dioxide; metal phyllosilicate on silicon dioxide; metal on metal phyllosilicate; metal phyllosilicate on metal phyllosilicate; metal phyllosilicate. [0083] The metallic species may, for example, be selected from the group consisting of a metal, a metal phyllosilicate, and a combination thereof. As mentioned above, the metal and/or the metal phyllosilicate may constitute an active phase of the catalyst. In various embodiments, the metal and/or metal of the metal phyllosilicate is selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), and a combination thereof. The metallic species may, for example, comprise an alloy of the afore-mentioned metals, such as an alloy of Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, or Cu-Fe. Accordingly, in embodiments wherein the metallic species comprises two different metals, the metal- silicon oxide catalyst may be a bi-metallic silicon oxide catalyst.

[0084] In various embodiments, the metal and/or metal of the metal phyllosilicate is selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe. Accordingly, the metal may be selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe, while the metal phyllosilicate may be selected from the group consisting of NiPs, CoPs, CuPs, FePs, NiCuPs, NiCoPs, NiFePs, CoCuPs, CoFePs, and CuFePs.

[0085] In various embodiments, the metallic species is present on the support in the form of nanoparticles. The nanoparticles may have a size in the range of about 3 nm to about 10 nm, such as about 5 nm to about 10 nm, about 7 nm to about 10 nm, about 3 nm to about 8 nm, about 3 nm to about 6 nm, about 5 nm to about 8 nm, or about 4 nm to about 7 nm. The nanoparticles may be regularly or irregularly shaped, and size of each nanoparticle may be characterized by the maximal length of a line segment passing through the center and connecting two points on the periphery of the nanoparticle.

[0086] The silicon oxide may function as a carrier for the metallic species, which may be affixed onto or embedded within the silicon oxide. The silicon oxide may, for example, be silicon oxide (SiO), silicon dioxide, otherwise termed herein as silica (S1O2), or a silicate such as a phyllosilicate. In various embodiments, the silicon oxide support comprises or consists of silica and/or a metal phyllosilicate. The metal phyllosilicate comprised in the silicon oxide support may, for example, be NiPs, CoPs, CuPs, FePs, NiCuPs, NiCoPs, NiFePs, CoCuPs, CoFePs, or CuFePs.

[0087] Generally, the silicon oxide support is porous to provide a greater surface area upon which the metallic species active phase is dispersed. The surface area of the silicon oxide support may range from about 100 m²g^_1 to about 1000 m²g^_1, such as about 100 m²g^_1 to about 800 m²g^_1, about 100 m²g^_1 to about 600 m²g^_1, about 100 m²g^_1 to about 400 m²g^_1, about 200 m²g^_1 to about 500 m²g^_1, about 200 m²g^_1 to about 400 m²g^_1, about 400 m2g-l, about 300 m²g^_1, or about 200 m²g^_1.

[0088] Porosity of the silicon oxide support may be characterized by the size of the pores. According to the definition of the International Union of Pure and Applied Chemistry (IUPAC), the term "mesopore/mesoporous" refers to pore size in the range of 2 nm to 50 nm; while a pore size below 2 nm is termed a micropore range, and a pore size that is greater than 50 nm is termed a macropore range. In various embodiments, the silicon oxide support comprises or consists essentially of mesopores.

[0089] In various embodiments, the silicon oxide support further comprises a metal oxide, wherein metal of the metal oxide is different from the metal and/or the metal of the metal phyllosilicate, and wherein the metal of the metal oxide is present in an elemental weight percent of 85 % or less. Suitable metal oxides have already been described above.

[0090] In various embodiments, metal of the metal oxide is selected from the group consisting of Mg, Ca, Ce, Al, Zr, and a combination thereof.

[0091] In various embodiments, the metal-silicon oxide catalyst is selected from the group consisting of Ni-Si0₂, Ni-Co-Si0₂, and Cu-Si0₂, Ni-Si0₂-MgO, Ni-Co-Si0₂, Ni-Si0₂-Ce0₂, and NiCo-Si0₂-Ce0₂.

[0092] Various embodiments in a further aspect to use of a metal-silicon oxide catalyst prepared by a method disclosed herein, or a metal-silicon oxide catalyst disclosed herein in reforming of light hydrocarbon reactions for the production of synthesis gas.

[0093] As used herein, the term "light hydrocarbon" refers to CI to C7 hydrocarbons. For example, the Ci to C₇ hydrocarbons may comprise or consist of CI to C3 hydrocarbons, C4 to C7 hydrocarbons, or a hydrocarbon fraction such as a C6 fraction, a C7 fraction, a C8 fraction, a C6-C7 fraction, a C7-C8 fraction, a C6-C8 fraction. As mentioned above, reforming of the light hydrocarbon reactions for the production of synthesis gas may be one of steam reforming, dry reforming or a combined reforming. Advantageously, the reforming may be carried out at a temperature in the range of about 650 °C to about 850 °C, such as about 700 °C to about 850 °C, about 750 °C to about 850 °C, about 650 °C to about 800 °C, about 650 °C to about 750 °C, about 650 °C to about 700 °C, or about 700 °C to about 750 °C. [0094] In various embodiments, the reforming is steam reforming or combined reforming, and the steam reforming or combined reforming is carried out at a steam to carbon ratio in the range of about 1 to about 3. In some embodiments, the reforming is dry reforming, and the dry reforming is carried out at a carbon dioxide to carbon ratio in the range of about 1 to about 1.5.

[0095] Advantageously, catalysts disclosed herein may be highly active in steam reforming of methane at low steam to carbon ration (S/C) of 1.5, with negligible carbon deposition. There is lower S/C as compared to conventional values which are usually above 2, and with negligible carbon deposition showing the lower operational costs required to promote activity and overcome carbon deposition. Economical synthesis procedures may be carried out in a facile manner, which is important for large scale production.

[0096] As used herein, the terms "about" and "approximately", in the context of concentrations of components of the formulations, or where applicable, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

[0097] Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that, the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0098] The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0099] Other embodiments are within the following claims and non- limiting examples. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

EXPERIMENTAL SECTION

[00100] Various embodiments relate to a facile route for the synthesis of highly active mono (Ni, Co, Cu, Fe) and bi-metallic (Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, Cu-Fe) catalysts for CC /steam reforming of light hydrocarbon reaction applications. A novel metal supported catalyst, a method of making the catalyst and the process of using the catalyst for synthesis gas production reaction via industrially important steam, dry (C0₂), and combined (steam + CO2) reforming of light hydrocarbon processes, according to various embodiments are disclosed herein.

[00101] Various embodiments relate to Si02-(MgO/CaO) catalysts, as well as mono and bimetallic-based S1O2 catalysts. The former are highly active and stable for both steam and CO2 reforming of light hydrocarbons and biogas reactions for syngas production with negligible carbon deposition. The catalysts without base metal oxides were also presented for CO2 reforming reaction. Additionally, this kind of catalysts can also be highly active and stable for high-temperature water-gas-shift reaction for hydrogen -rich syngas productions.

[00102] The catalyst may be of general formula M-S1O2-B, where M is a metallic species disclosed herein, and B is nothing or a metal oxide. The synthesis method may be carried out in an aqueous medium via an ammonia evaporation method followed by hydrothermal treatment. During ammonia evaporation step, precursors for M species may be used, and a source of S1O2 may be in basic medium solution. pH of the basic medium solution should be above 12. The ammonia evaporation may typically be carried out at temperatures between 50 °C and 100 °C. The hydrothermal treatment should be carried out at a temperature between 80 °C and 200 °C for at least 12 h in a sealed vessel. B species precursors with base solution may be added to the solution obtained after ammonia evaporation method, and before hydrothermal treatment.

[00103] The M, Si, and B elemental weight percentages for the prepared catalysts may range from 5 % to 35 %, 15 % to 65 %, and 0 % to 85 % respectively.

[00104] The M species may be either mono-metallic (such as, Ni, Co, Cu, Fe) or combination of two metal species (such as, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, Cu-Fe).

[00105] The B species may be either MgO or CaO, or a combination of both species. [00106] The catalyst prepared from a process disclosed herein may be used for steam, C0₂ and combined (steam and CO2) reforming of light hydrocarbon reactions for the production of synthesis gas.

[00107] The steam to carbon ratio for steam reforming reaction using a catalyst prepared from a process disclosed herein may be 1 to 3 and but should not exceed 3 in order to obtain optimum catalytic performance.

[00108] The steam to carbon ratio for combined reforming of light hydrocarbon reaction may be less than or equal to 2.

[00109] The CO2 to carbon ratio for a CO2 reforming process disclosed herein may be 1 to 1.5 and but should not exceed 1.5 in order to obtain optimum catalytic performance.

[00110] The processes of steam, CO2 and combined (steam and CO2) reforming of light hydrocarbon reactions for the production of synthesis gas may be carried out between 650 °C and 850 °C.

[00111] FIG. 1 shows the catalytic performance of 15 wt% Ni-Si h-MgO catalyst for steam reforming of methane reaction at reaction temperature of 750 °C. It is clear from FIG. 1 that 15 wt% Ni-Si02-MgO gave a stable methane conversion of around 85 % with H2/CO value of around 4 for a reaction time of 220 h. The influence of steam-to-carbon ratio is also investigated over 15 wt% Ni-SiC -MgO catalyst and the thus obtained results are depicted in Figure 2.

[00112] FIG. 2A shows the methane conversion values and FIG. 2B shows H2/CO values obtained over 15 wt% Ni-SiC -MgO catalyst at various S/C ratios. It is observed that a relatively S/C of 1.5 is enough to obtain an optimum steam reforming catalytic performance over 15 wt% Ni-Si h-MgO catalyst.

[00113] FIG. 3 shows the steam reforming of methane performance of 15 wt% Ni-SiC - MgO catalysts having various Si/Mg wt. ratios. It is observed that all catalysts showed methane conversion values between 75 % and 85 % for a reaction time of 26 h at 750 °C of reaction time. FIG. 4 shows the steam reforming of methane performance of 20 wt% Ni- SiC -MgO catalyst for 52 h reaction time and reaction temperature of 750 °C at relatively lower S/C ratio of 1.5. The GHSV value for this catalytic test is relatively high at 194 L/g.h. It is observed that 20 wt% Ni-SiC -MgO catalyst gave a stable methane conversion value of 80 % with H2/CO value around 3.5. FIG. 5 shows the DTA/TGA analysis for the catalysts tested after steam reforming of methane at 750 °C with relatively lower S/C ratio of 1.5. FIG. 5A is the DTA/TGA analysis profiles of 15 wt% Ni-Si -MgO catalyst after steam reforming of methane reaction as in FIG. 1, and shows deposition of carbon during the steam reforming reaction for about 220 h is almost negligible. Similar result was also observed for 20 wt% Ni- SiC -MgO catalyst (FIG. 5B) tested for steam reforming of methane reaction for 53 h at S/C ratio of 1.5 as shown in FIG. 4.

[00114] These Ni-Si -MgO catalysts are also tested for combined (steam + C0₂) reforming of methane reaction for the synthesis of syngas production. FIG. 6 depicted the reforming performance of 15wt% Ni-SiC -MgO catalyst. It shows that the stable conversions for CH₄ and CO2 are 88 % and 78 % respectively with H2/CO value is around 2 for a reaction time of 140 h. Similarly, FIG. 7 shows the combined reforming of methane activity over 10 wt% Ni-SiC -MgO catalyst for a reaction period of 70 h, it gave a CH₄ and CO2 conversions are 90 % and 83 % respectively. The combined reforming of methane reaction for 26 h reaction time over 20 wt% Ni-SiC -MgO catalyst is depicted in FIG. 8. It shows that the CH₄ and CO2 conversions are 78 % and 73 % respectively. The obtained H7CO value from FIG. 6 to FIG. 8 are nearly 2 (Metgas, CO-2H2), which is an important ratio for downstream applications in Fischer Tropsch synthesis. These combined reforming activities were carried out at a reaction temperature of 750 °C and CH₄:C02:H20 = 1:0.5: 1. It is noteworthy to mention here that the carbon deposition rates for all these catalysts during reforming of methane reaction appears to be negligible. The DTA/TGA profiles of spent 10 wt% Ni-SiC - MgO (activity profiles as in FIG. 7) and 15 wt% Ni-Si h-MgO (in FIG. 6) catalysts are presented in FIG. 9.

[00115] FIG. 10 shows the TPR profiles of Ni-SiC -MgO catalysts together with Ni/MgO catalyst as a reference catalyst. The reduction profile of Ni/MgO catalyst typically shows two-stage reduction, a low temperature reduction peak around 550 °C is ascribed to the reduction of bulk NiO species and a high temperature reduction peak centered around 850 °C is due to reduction of Ni-MgO composite material. All Ni-SiCh-MgO catalysts showed a similar reduction behavior of single reduction peak centered at 700 °C with a shoulder near 800 °C. The reduction at around 700 °C is ascribed to the reduction of Ni species with strong interaction with S1O2 species, which could be established during the first step of catalyst preparation method. The shoulder around 800 °C is due to the weaker interaction between Ni species and MgO species, which might be established during second stage of preparation method. From these reduction profiles of Ni-SiCh-MgO catalysts, it can be concluded that the reducibility of Ni species present in these catalysts are quite uniform and also have significantly stronger interactions with S1O2 and MgO species present in the catalyst material. This led to stabilization within the matrixes of support materials and thus confers the ability to perform catalytically well in both steam and CO2 reaction environments simultaneously.

[00116] The mono-metallic Ni-Si and bi-metallic Ni-Co-SiC catalysts were also tested for CO2 reforming of methane reaction. FIG. 11 shows the catalytic performance of 15 wt% Ni-Si02 catalyst for CO2 reforming of methane reaction at 750 °C of reaction temperature. It is clear from FIG. 11 that 15 wt% Ni-Si gave a stable CO2 and CH₄ conversions of around 81% and 80%, respectively with H2/CO value of around 0.87 for a reaction time of 100 h. This catalyst also shows negligible carbon formation during 100 h of reaction time.

[00117] FIG. 12 shows the CO2 reforming of methane activity over 7 wt% Ni-3 wt% Co- S1O2 catalyst at 750 °C. It is clear from the figure that the catalyst gave stable methane and CO2 conversions of around 84 % and 86 %, respectively for 100 h reaction time. The DT/TGA analysis as in FIG. 13 for this 7 wt% Ni-3 wt% C0-S1O2 catalyst shows there is a negligible carbon is deposited during reforming reaction. The needle-like characteristic bimetallic structures supported over S1O2 support is evident from the TEM image of freshly calcined Ni-Co-Si catalysts. These needle-like structures upon ¾ reduction at 800 °C were decomposed to form well dispersed and stabilized metal supported catalysts. The TEM image of 7 wt% Ni-3 wt% C0-S1O2 catalyst spent in reforming reaction for 100 h was depicted in FIG. 15. The absence of any kind of carbon species is clearly observed from this image. FIG. 16 shows the reducibility profiles for freshly calcined Ni-Co-Si catalysts with varying Ni/Co ratio. From Figure, it seems as the nickel loading going up, the main reduction peak shifts to lower temperature, indicating nickel phyllosilicate (PS) is easier to be reduced than cobalt phyllosilicate. Besides, the integrated reduction peak, instead of multiple separated peaks, implies the formation of Ni-Co alloy.

[00118] The claimed method of preparation was further extended to the synthesis of Cu- based catalysts. The appearance of peaks in the XRD profile (FIG. 17) for Cu/SiC catalyst shows that the crystallinity and the size of the Cu species are higher in the catalyst prepared via conventional impregnation method. The absence of these peaks for CuPS/SiC confirms the size of Cu species is low and is possibly well dispersed.

[00119] The TEM image of Cu-PS catalyst in FIG. 18 shows the appearance of needle like structures, which is a characteristic of formation of Cu-containing phyllosilicates. [00120] Ni-Co-Si02-Ce02 catalysts according to embodiments disclosed herein were prepared for steam reforming of lower hydrocarbon. FIG. 19 are TEM images of NiCo- S1O2 and NiCo-Si0₂-Ce0₂. It can be seen from the figure that uniform characteristic needle like NiCo-containing phyllosilicate phases have been successfully synthesized. After that, a layer of base metal oxide (Ce0₂) was coated using a precipitation method such as a hydrothermal treatment process disclosed herein.

[00121] NiCo-PS-Ce0₂ catalysts were tested for steam reforming of toluene. It can be seen from FIG. 20A and FIG. 20B that a relatively stable toluene conversion of around 70 % was achieved within 20 h and less than 5 % weight loss was found for Ni-Co-Si0₂-Ce0₂ catalyst, indicating its high carbon resistant property. Furthermore, about 15 % decrease in toluene conversion was observed within 20 h. This result suggests that the catalyst stability may be further improved.

[00122] Mono-metallic Ni-Ps-Ce0₂ catalysts according to embodiments disclosed herein were developed for C0₂ reforming of methane at relatively lower temperature. TEM images as in FIG. 21 A to FIG. 21D show the formation of needle like structures are due to the Ni- containing phyllosilicate structures are uniformly coated by base metal oxide (Ce0₂). It can be seen from FIG. 21D that the Ce0₂ shell was assembled by small Ce0₂ nanoparticles with size of 7.7 nm. Finally, upon reduction under H₂, Ni@Ni-Ps@Ce0₂ with uniform distribution of both Ni and Ce0₂ were obtained.

[00123] FIG. 22A to FIG. 22D demonstrate the chemical states of Ni and Ce for Ni@Ni- Ps and Ni@Ni-Ps@Ce0₂. Ce 3d spectrum was fitted and deconvoluted with eight components labelled as u and v, representing Ce³⁺ ( u' and v') and Ce⁴⁺ (other six peaks) respectively. The Ce³⁺/(Ce³⁺ + Ce⁴⁺) ratio which has been reported to relate to surface oxygen vacancies was calculated based on the peak areas of u and v. This ratio was 0.45, which was much higher than the value of other Ni-Ce based catalysts, indicating that much more oxygen vacancies were formed. Three peaks centered at 530.3 eV, 531.8 eV, and 533.1 eV in O Is spectrum may be assigned to lattice oxygen, chemisorbed oxygen by Ce³⁺ in the form of -OH and C-0 species or oxygen vacancies and oxygen bond in Ni-Ps structures respectively. The ratio of chemisorbed oxygen accounted for 32 % of the surface oxygen species calculated from the peak areas, which was comparable to that of other Ni-Ce based catalysts and which further proved the existence of high concentration of oxygen vacancies. [00124] It can be found from FIG. 23A that under such a harsh reaction condition, even though both the C0₂ and CH₄ conversion continuously decreased within the testing time of 20 h, Ni-PS-CeC showed a higher and more stable CO2 specific activity with a decrease of 14.2 % compared with 47.8 % for Ni-Ps. Further, it is interesting to observe that Ni-Ps had a comparable CH₄ conversion with that of Ni-PS-CeC . This may be attributed to the predominance of CH₄ decomposition side reaction for Ni-Ps which led to its much higher carbon deposition amount (47.5 % weight loss, FIG. 23A to FIG. 23D). The high carbon deposition of Ni-Ps lead to its lower catalytic activity and worse stability. The stable catalytic performance of Ni-Ps-CeC may also be seen from its much more stable H2/CO ratio compared with Ni-Ps (FIG. 23B).

[00125] To further show the high carbon resistant property of Ni-Ps-Ce , DRM reaction at a low temperature of 600 °C when the carbon deposition problem was known to be more serious was tested together with Ni-Ps for comparison as shown in FIG. 23C and FIG. 23D. It can be seen that Ni-Ps-Ce showed a more stable and higher specific activity for both CO2 and CH₄ as well as H2/CO ratio within the testing time of 50 h. Specifically, there is only a drop of 5.3 % and 5.8 % for CO2 and CH₄ for Ni-Ps-Ce0₂ compared with 33.3 % and 38.5 % for Ni-Ps respectively. In addition, it should be noted that the CO2 specific activity for Ni- Ps-Ce02 was much higher than that of Ni-Ps, indicating the high ability of the former to activate CO2 to react with the deposited carbon because of its high concentration of oxygen vacancies. This also led to the relative lower H2/CO ratio of Ni-Ps-Ce in addition to the reverse water gas shift reaction as can be seen from FIG. 23D.

[00126] The spent catalysts for DRM reaction at 700 °C were also characterized by TGA- DTA and TEM characterizations as shown in FIG. 24. From FIG. 24, it may be observed that Ni-Ps-CeC exhibited much better carbon resistant property with a weight loss of 10.6 % due to its high concentration of oxygen vacancies as discussed from the XRD, XPS and H2- TPR characterizations earlier, which were active to chemisorb oxygen species from CO2 thereby activating CO2 to react with the deposited carbon species. The exothermal peaks of carbon oxidation centered at 585 °C and 645 °C for Ni-Ps-CeC and Ni-Ps may be assigned to a-type and β-type carbon respectively. The former was active to produce syngas; while the latter was inactive and led to catalyst deactivation. This accounted for the sharply decreased catalytic performance of Ni-Ps compared with Ni-Ps-CeC . The morphologies of these two catalysts after 20 h reaction were found to be stable without sintering of Ni and CeC . However, tremendous carbon nanotubes were observed for Ni-Ps compared with Ni-Ps-CeC , which coincides with the TGA-DTA results.

[00127] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

A method for preparing a metal- silicon oxide catalyst, the method comprising a) mixing a metal precursor with a silicon oxide precursor in an aqueous mixture comprising ammonia and having a pH of at least 12 to form a reaction mixture, and b) hydrothermally treating the reaction mixture.

The method according to claim 1, wherein mixing the metal precursor with the silicon oxide precursor is carried out at a temperature in the range of about 50 °C to about 100 °C.

The method according to claim 1 or 2, wherein the metal precursor comprises a metal selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), and a combination thereof.

The method according to any one of claims 1 to 3, wherein the metal precursor comprises a metal selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni- Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe.

The method according to any one of claims 1 to 4, wherein hydrothermally treating the reaction mixture is carried out at a temperature in the range of about 80 °C to about 200 °C.

The method according to any one of claims 1 to 5, wherein hydrothermally treating the reaction mixture is carried out for at least 12 hours.

The method according to any one of claims 1 to 6, further comprising adding a metal oxide precursor to the reaction mixture before hydrothermally treating the reaction mixture.

The method according to claim 7, wherein metal of the metal oxide precursor is selected from the group consisting of Mg, Ca, Ce, Al, Zr, and a combination thereof.

The method according to any one of claims 1 to 8, wherein the reaction mixture following the hydrothermal treatment is reduced in hydrogen gas.

A metal-silicon oxide catalyst, wherein the metal is present in an elemental weight percent of 5 % to 35 % and silicon is present in an elemental weight percent of 15 % to 65 % of the catalyst.

The metal-silicon oxide catalyst according to claim 10, wherein the metal-silicon oxide catalyst is in one or more of the following forms:

a) metal on silicon dioxide;

b) metal phyllosilicate on silicon dioxide;

c) metal on metal phyllosilicate;

d) metal phyllosilicate on metal phyllosilicate;

e) metal phyllosilicate.

The metal-silicon oxide catalyst according to claim 10 or 11, wherein the metal and/or metal of the metal phyllosilicate is selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), and a combination thereof.

The metal-silicon oxide catalyst according to any one of claims 10 to 12, wherein the metal and/or metal of the metal phyllosilicate is selected from the group consisting of Ni, Co, Cu, Fe, Ni-Cu, Ni-Co, Ni-Fe, Co-Cu, Co-Fe, and Cu-Fe.

The metal-silicon oxide catalyst according to any one of claims 10 to 13, wherein the metal-silicon oxide catalyst further comprises a metal oxide, wherein metal of the metal oxide is different from the metal and/or the metal of the metal phyllosilicate, and wherein the metal of the metal oxide is present in an elemental weight percent of 85 % or less.

15. The metal-silicon oxide catalyst according to claim 14, wherein metal of the metal oxide is selected from the group consisting of Mg, Ca, Ce, Al, Zr, and a combination thereof.

16. The metal-silicon oxide catalyst according to any one of claims 10 to 15, wherein the metal-silicon oxide catalyst is selected from the group consisting of Ni-Si0₂, Ni-Co- Si0₂, and Cu-Si0₂, Ni-Si0₂-MgO, Ni-Co-Si0₂, Ni-Si0₂-Ce0₂, and NiCo-Si0₂-Ce0₂.

17. The metal-silicon oxide catalyst according to any one of claims 10 to 16, wherein the metal and/or the metal phyllosilicate constitute an active phase of the catalyst.

18. Use of a metal-silicon oxide catalyst prepared by a method according to any one of claims 1 to 9, or a metal-silicon oxide catalyst according to any one of claims 10 to 17 in reforming of light hydrocarbon reactions for the production of synthesis gas.

19. The use according to claim 18, wherein the reforming is carried out at a temperature in the range of about 650 °C to about 850 °C.

20. The use according to claim 18 or 19, wherein the reforming is

a) steam reforming or combined reforming, wherein the steam reforming or combined reforming is carried out at a steam to carbon ratio in the range of about 1 to about 3, or

b) dry reforming, wherein the dry reforming is carried out at a carbon dioxide to carbon ratio in the range of about 1 to about 1.5.