Method and catalyst

Abstract

A method for producing a gaseous product comprising hydrogen, the method comprising exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises: at least one metal species on a support, wherein the metal species is at least one of a nickel species or a cobalt species; and a solid catalyst suitable for use in the method, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

Description

Technical Field

[0001] The present invention relates to a method for producing a gaseous product comprising hydrogen from gaseous hydrocarbons. In particular, the method of the present invention provides a method capable of capturing, storing, and utilizing carbon dioxide in a cyclic process. Furthermore, the present invention provides a solid catalyst for use in the method of the present invention, which serves as both a carbon dioxide source and a carbon capture precursor. Background Art

[0002] To keep global warming below 2°C, carbon capture and storage (CCS), renewable energy development, and end-use energy efficiency improvements are expected to contribute approximately 82% of the cumulative reduction in CO2 emissions by 2050. [1] Among these strategies, CCS is a low-carbon option suitable for large-scale fixed CO2 sources such as coal-fired power plants and energy-intensive industrial sectors. However, the economic potential of CCS processes may not be realized by simply storing CO2 as waste in geological storage. In addition, the potential ecological hazards associated with CO2 storage remain uncertain. [2] .

[0003] Recently, CO2 has been recognized as a suitable carbon source that, once activated for chemical conversion and production, may improve the economic competitiveness of CCS plants and provide a way to close the carbon cycle within human socio-economic systems.

[0004] Currently, only 0.3% of global CO2 emissions are converted into chemicals, and more than 90% of this is used to produce urea, which, when used as fertilizer, ultimately results in the emission of CO2 back into the atmosphere. There are many laboratory methods, such as electrochemical and photocatalytic reduction of CO2, to produce useful organic products from CO2, including alcohols, alkanes, alkenes, and fuels, but methods that can consume and convert large amounts of CO2 are still lacking.

[0005] To date, methane dry reforming (MDR), which reforms CH4 with CO2 to a platform mixture of H2 and CO2, appears to be the only approach close to industrial application for large-scale CO2 utilization. However, there are two major challenges for conventional thermal MDR processes: 1) the energy-intensive capture and purification processes for supplying CO2 as a feedstock; 2) high operating temperatures (≥820°C, calculated by HSC stoichiometry). [3] Therefore, it is attractive to develop a method to capture CO2 in an easier and energy-efficient way and then convert the captured CO2 directly into useful products with fewer steps.

[0006] Recently, CO2 capture and its direct activation in a single system were demonstrated over a Ni / Ca-based composite catalyst. [1,4] .

[0007] Calcium-based absorbents have been extensively studied for CO₂ capture, and calcium cyclic carbonization and calcination processes have been considered promising approaches for capturing high-temperature CO₂ from flue gases. However, in these high-temperature CO₂ capture processes, the CO₂ absorption capacity of calcium absorbents typically declines rapidly after a few cycles due to clogging caused by the formation of CaCO₃ on the surface of the CaO absorbent, which hinders the contact of CO₂ with the CaO absorbent. Furthermore, CO₂ desorption requires very high temperatures and a correspondingly large energy input.

[0008] To overcome the rapid decline in CO2 absorption capacity, many methods, including doping and pre-combustion, have been used to stabilize the microstructure of CaO absorbents, or hydration of CaO with water to form Ca(OH)2 has been employed. [5] Among these methods, almost all processes start with CaO as an absorbent, and calcium salts (calcium nitrate, calcium acetate, etc.) are used as precursors for preparing CaO absorbents, which are accompanied by huge pollutant emissions (such as nitrogen oxides or CO2). Considering the high consumption of CaO absorbents with specific nanostructures in large-scale CO2 processes, it is also desirable to prepare and use absorbents with sufficient CO2 absorption capacity.

[0009] The present invention provides a cyclic process comprising hydrocarbon dry reforming, CO2 capture, and its rapid activation for further hydrocarbon reforming. Rapid and selective heating offers the potential to reform hydrocarbons using carbonates as CO2 carriers at relatively low catalyst bed temperatures, subsequently allowing the formation of a CO2 absorbent without generating significant waste heat.

[0010] In addition to the potential to improve the energy efficiency of carbonate decomposition compared to conventional thermal calcium cycle CO2 capture processes, the lower catalyst bed temperature minimizes the loss of CO2 absorption capacity of the CaO absorbent. The dual-functional catalyst-absorbent system for CO2 capture and conversion expands future application scenarios, including flue gas CO2 capture in CO2-intensive industrial sectors and direct CO2 absorption from the atmosphere (which typically encounters steam and moisture during the CO2 absorption process). Therefore, the present invention helps combat global warming. Summary of the Invention

[0011] In one aspect, the present invention is directed to a method of producing a gaseous product comprising hydrogen, the method comprising exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support, wherein the metal species is at least one of a nickel species or a cobalt species, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0012] In another aspect, the present invention is directed to a solid catalyst comprising one or more metal oxides on a support, wherein the metal oxide is at least one of nickel oxide or cobalt oxide, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0013] In another aspect, the present invention relates to a microwave reactor comprising a heterogeneous mixture comprising a solid catalyst as defined herein in admixture with a gaseous hydrocarbon.

[0014] In another aspect, the invention relates to a fuel cell module comprising (i) a fuel cell and (ii) a heterogeneous mixture comprising a solid catalyst as defined herein mixed with a gaseous hydrocarbon.

[0015] Preferred, suitable and optional features of any particular aspect of the invention are also preferred, suitable and optional features of any other aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The system composition of microwave-induced reforming reaction on metal / carbonate bifunctional catalyst is shown.

[0017] FIG2 shows the methane reforming results on different metal species supported on CaCO 3 powder, including (A) the calculated CaCO 3 conversion and the percentage of CO 2 converted to syngas, and (B) the molar amounts of H 2 and CO produced.

[0018] FIG3 shows the methane reforming results on CaCO3-supported nickel species samples with different Ni / Ca ratios, including (A) the calculated CaCO3 conversion and the percentage of CO2 converted to synthesis gas, and (B) the molar amounts of H2 and CO generated.

[0019] Figure 4 shows the methane reforming results on NiO / CaCO3 (1:18) samples with different CH4 feed flow rates, including (A) the calculated CaCO3 conversion and the percentage of CO2 converted to synthesis gas, and (B) the molar amounts of H2 and CO generated.

[0020] FIG5 shows the time-on-stream (time-on-stream) results for methane reforming over NiO / CaCO3 with a Ni / Ca ratio of 1:18, including (A) the amount of gas produced in each time period; and (B) the microwave power curve and the catalyst bed temperature recorded by an infrared pyrometer.

[0021] FIG6 shows the results of each cycle of the methane reforming reaction, including (A) the calculated CaCO3 and CO2 conversions; and (B) the molar amounts of H2 and CO produced.

[0022] Figure 7 shows the cyclic methane reforming performance on the catalyst (Ni / Ca ratio of 1:18) regenerated by three different carbonate sources (CO2(g), Na2CO3 and NH4HCO3), including (A) the calculated conversion of CaCO3 (solid line) and CO2 (dashed line); (B) the molar amounts of H2 and CO produced.

[0023] Figure 8 Catalyst morphology at different stages of the CO2 capture and methane reforming cycle. (A) to (D) are SEM images. (A) Fresh NiO / CaCO3 sample; (B) NiO / CaCO3 sample after methane reforming reaction; (C) Sample after the first regeneration with CO2 in H2O medium. (D) Sample after the 12th cycle and calcination at 700°C in air to remove deposited carbon. (E) to (H) are corresponding TEM images of the samples shown in (A) to (D), respectively. DETAILED DESCRIPTION

[0024] definition

[0025] As used herein, the term "gaseous product" refers to a product that is gaseous at standard ambient temperature and pressure (SATP), ie, at a temperature of 298.15 K (25°C) and 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm).

[0026] As used herein, the term "gaseous hydrocarbons" refers to hydrocarbons that are gaseous at standard ambient temperature and pressure (SATP), i.e., at a temperature of 298.15 K (25° C.) and 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm). Examples include methane, ethane, propane, and butane.

[0027] As used herein, the term "hydrocarbon" refers to an organic compound composed of carbon and hydrogen.

[0028] For the avoidance of doubt, hydrocarbons include straight and branched chain, saturated and unsaturated aliphatic hydrocarbon compounds, including alkanes, alkenes and alkynes.

[0029] “C n-m Hydrocarbons" or "C n -C m "Cn-Cm hydrocarbons" or "Cn-Cm hydrocarbons", where n and m are integers, are hydrocarbons as defined above having n to m carbon atoms. For example, C 1-4 Hydrocarbons are hydrocarbons as defined above having 1 to 4 carbon atoms.

[0030] As used herein, the term "alkane" refers to a linear or branched saturated hydrocarbon compound. Examples of alkanes include methane, ethane, propane, and butane. Alkanes such as dimethylbutane may represent one or more possible isomers of the compound. Thus, dimethylbutane includes both 2,3-dimethylbutane and 2,2-dimethylbutane. This also applies to all hydrocarbon compounds mentioned herein.

[0031] As used herein, the term "alkene" refers to a straight or branched hydrocarbon compound containing one or more double bonds. Examples of alkene are ethylene, propylene, butene, etc. Alkenes typically contain one or two double bonds. The terms "alkene" and "olefin" can be used interchangeably. One or more double bonds can be located at any position in the hydrocarbon chain. Alkenes can be cis or trans olefins (or as defined using E- and Z-nomenclature). Olefins containing terminal double bonds can be referred to as "alkene-1" (e.g., hex-1-ene), "terminal olefins" (or "terminal olefins"), or "alpha-olefins" (or "alpha-olefins").

[0032] As used herein, a "metal species" is any compound containing a metal. Thus, a metal species includes elemental metals, metal oxides, and other compounds containing metals, i.e., metal salts, alloys, hydroxides, carbides, borides, silicides, and hydrides. When a specific example of a metal species is recited, the term includes all compounds containing that metal. For example, a nickel species includes elemental nickel, nickel oxides, nickel salts, nickel alloys, nickel hydroxides, nickel carbides, nickel borides, nickel silicides, and nickel hydrides.

[0033] As used herein, for example, the term "elemental metal" or a specific example such as "elemental Ni" refers to a metal only when it is in the zero oxidation state.

[0034] Unless otherwise indicated, reference to an element using standard notation refers to the element in any available oxidation state. Similarly, use of the term "metal" without further limitation on oxidation state is not a limitation on available oxidation states.

[0035] As used herein, the term "transition metal" refers to an element in one of three series of elements resulting from the filling of the 3d, 4d, and 5d shells. Unless otherwise indicated, reference to a transition metal in general or by using the standard notation for a particular transition metal refers to that element in any available oxidation state.

[0036] As used herein, the term "alkaline earth metals" refers to elements of Group 2 of the Periodic Table of Elements.

[0037] As used herein, the term "heterogeneous mixture" refers to a physical combination of at least two different substances, wherein the two different substances are not in the same phase at standard ambient temperature and pressure (SATP), i.e., at a temperature of 298.15 K (25° C.) and 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm). For example, one substance can be a solid and one substance can be a gas.

[0038] As used herein, "solid catalyst" refers to a solid material to which reactants or feeds are exposed in order to achieve a catalytic conversion. A solid catalyst is solid at standard ambient temperature and pressure (SATP), i.e., at a temperature of 298.15 K (25° C.) and 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm). The solid catalyst may or may not require activation (e.g., in a preliminary step or under reaction conditions) to provide catalytically active species.

[0039] As used herein, "synthesis gas" (also known as synthesis gas) is a fuel gas mixture consisting essentially of hydrogen and carbon monoxide. However, small amounts of carbon dioxide and hydrocarbons may be present.

[0040] method

[0041] In one aspect, the present invention is directed to a process for producing a gaseous product comprising hydrogen, the process comprising exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support, wherein the metal species is a nickel species or a cobalt species, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0042] In one embodiment, the process produces about 40% or more hydrogen by volume of the total amount of gaseous products. Suitably, about 45% or more hydrogen by volume of the total amount of gaseous products, more suitably, about 50% or more hydrogen by volume, more suitably, about 55% or more hydrogen by volume, more suitably, about 60% or more hydrogen by volume, more suitably, about 65% or more hydrogen by volume, more suitably, about 70% or more hydrogen by volume, more suitably, about 75% or more hydrogen by volume, or more suitably, about 80% or more hydrogen by volume of the total amount of gaseous products.

[0043] In another embodiment, the method produces about 45 volume % to about 90 volume % hydrogen of the total amount of gaseous products. Suitably, about 45 volume % to about 85 volume % hydrogen of the total amount of gaseous products, more suitably, about 45 volume % to about 80 volume % hydrogen, more suitably, about 45 volume % to about 75 volume % hydrogen, more suitably, about 45 volume % to about 70 volume % hydrogen, more suitably, about 45 volume % to about 65 volume % hydrogen, or more suitably, about 45 volume % to about 60 volume % hydrogen, of the total amount of gaseous products.

[0044] In another embodiment, the method produces about 50% to about 99% by volume of hydrogen in the total amount of gaseous products. Suitably, about 55% to about 99% by volume of hydrogen in the total amount of gaseous products, more suitably, about 60% to about 99% by volume of hydrogen, more suitably, about 65% to about 99% by volume of hydrogen, more suitably, about 70% to about 99% by volume of hydrogen, more suitably, about 75% to about 99% by volume of hydrogen, or more suitably, about 80% to about 99% by volume of hydrogen in the total amount of gaseous products.

[0045] In one embodiment, the method produces about 25% or more carbon monoxide by volume of the total amount of gaseous products. Suitably, about 30% or more carbon monoxide by volume of the total amount of gaseous products, more suitably, about 35% or more carbon monoxide by volume of the total amount of gaseous products, more suitably, about 40% or more carbon monoxide by volume of the total amount of gaseous products, more suitably, about 45% or more carbon monoxide by volume of the total amount of gaseous products, more suitably, about 50% or more carbon monoxide by volume of the total amount of gaseous products.

[0046] In one embodiment, the process produces about 10% to about 60% by volume of hydrogen in the total amount of gaseous products. Suitably, about 45% to about 85% by volume of the total amount of gaseous products is hydrogen, more suitably, about 45% to about 80% by volume of the total amount of gaseous products is hydrogen, more suitably, about 45% to about 75% by volume of the total amount of gaseous products is hydrogen, more suitably, about 45% to about 70% by volume of the total amount of hydrogen, more suitably, about 45% to about 65% by volume of the total amount of gaseous products is hydrogen, or more suitably, about 45% to about 60% by volume of the total amount of gaseous products.

[0047] In one embodiment, the gaseous product comprises hydrogen and carbon monoxide. In one embodiment, the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 10:1 to about 1:10. In another embodiment, the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 3:1 to about 1:3, suitably from about 3:1 to about 1:2, more suitably from about 3:1 to about 2:3, more suitably from about 3:1 to about 5:6, and more suitably from about 3:1 to about 10:11.

[0048] In another embodiment, the gaseous product comprises hydrogen and carbon monoxide, wherein the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 2:1 to about 1:2, more suitably from about 2:1 to about 2:3, more suitably from about 2:1 to about 5:6, and more suitably from about 2:1 to about 10:11.

[0049] In another embodiment, the gaseous product comprises hydrogen and carbon monoxide, wherein the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 3:2 to about 1:2, more suitably from about 3:2 to about 2:3, more suitably from about 3:2 to about 5:6, and more suitably from about 3:2 to about 10:11.

[0050] In another embodiment, the gaseous product comprises hydrogen and carbon monoxide, wherein the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 6:5 to about 5:6, more suitably from about 6:5 to about 10:11.

[0051] In another embodiment, the gaseous product comprises hydrogen and carbon monoxide, wherein the molar ratio of hydrogen to carbon monoxide in the gaseous product is from about 1:1 to about 2:1, more suitably from about 1:1 to about 3:2, and even more suitably from about 1:1 to about 6:5.

[0052] In another embodiment, the gaseous product comprises hydrogen and carbon monoxide, wherein the molar ratio of hydrogen to carbon monoxide in the gaseous product is about 1:1.

[0053] In one embodiment, the gaseous product comprises about 50 volume % or more hydrogen and carbon monoxide in the total amount of gaseous product.In another embodiment, the gaseous product comprises about 70 volume % or more hydrogen and carbon monoxide in the total amount of gaseous product.Suitably, about 75 volume % or more hydrogen and carbon monoxide in the total amount of gaseous product, more suitably be about 80 volume % or more hydrogen and carbon monoxide, more suitably be about 85 volume % or more hydrogen and carbon monoxide, more suitably be about 90 volume % or more hydrogen and carbon monoxide, more suitably be about 95 volume % or more hydrogen and carbon monoxide, more suitably be about 98 volume % or more hydrogen and carbon monoxide, more suitably be about 99 volume % or more hydrogen and carbon monoxide, in the total amount of gaseous product.

[0054] In another embodiment, gaseous product comprises hydrogen and carbon monoxide of about 10 volume % to about 100 volume % in the total amount of gaseous product.In another embodiment, gaseous product comprises hydrogen and carbon monoxide of about 60 volume % to about 100 volume % in the total amount of gaseous product.Suitably be hydrogen and carbon monoxide of about 65 volume % to about 100 volume % in the total amount of gaseous product, more suitably be hydrogen and carbon monoxide of about 70 volume % to about 100 volume %, more suitably be hydrogen and carbon monoxide of about 75 volume % to about 100 volume %, more suitably be hydrogen and carbon monoxide of about 80 volume % to about 100 volume %, more suitably be hydrogen and carbon monoxide of about 85 volume % to about 100 volume %, or more suitably be hydrogen and carbon monoxide of about 90 volume % to about 100 volume %, in the total amount of gaseous product.

[0055] In another embodiment, the gaseous product comprises about 60% to about 99% by volume of hydrogen and carbon monoxide, based on the total amount of gaseous products. Suitably, about 65% to about 99% by volume of hydrogen and carbon monoxide, more suitably about 70% to about 99% by volume of hydrogen and carbon monoxide, more suitably about 75% to about 99% by volume of hydrogen and carbon monoxide, more suitably about 80% to about 99% by volume of hydrogen and carbon monoxide, more suitably about 85% to about 99% by volume of hydrogen and carbon monoxide, or more suitably about 90% to about 99% by volume of hydrogen and carbon monoxide, based on the total amount of gaseous products.

[0056] In another embodiment, the gaseous product comprises from about 60% to about 95% by volume of hydrogen and carbon monoxide, based on the total amount of gaseous product. Suitably, from about 65% to about 95% by volume of hydrogen and carbon monoxide, more suitably from about 70% to about 95% by volume of hydrogen and carbon monoxide, more suitably from about 75% to about 95% by volume of hydrogen and carbon monoxide, more suitably from about 80% to about 95% by volume of hydrogen and carbon monoxide, more suitably from about 85% to about 95% by volume of hydrogen and carbon monoxide, or more suitably from about 90% to about 95% by volume of hydrogen and carbon monoxide, based on the total amount of gaseous product.

[0057] In one embodiment, the gaseous product comprises about 5% or less carbon dioxide by volume, suitably about 4% or less carbon dioxide by volume, more suitably about 3% or less carbon dioxide by volume, more suitably about 2% or less carbon dioxide by volume, more suitably about 1% or less carbon dioxide by volume, more suitably about 0.5% or less carbon dioxide by volume, in the gaseous product.

[0058] In one embodiment, the gaseous product comprises from about 0.1% to about 15% by volume of carbon dioxide. Suitably, the gaseous product comprises from about 0.1% to about 12% by volume of carbon dioxide, more suitably from about 0.1% to about 10% by volume of carbon dioxide, more suitably from about 0.1% to about 7% by volume of carbon dioxide, more suitably from about 0.1% to about 6% by volume of carbon dioxide, more suitably from about 0.1% to about 5% by volume of carbon dioxide, more suitably from about 0.1% to about 4% by volume of carbon dioxide, more suitably from about 0.1% to about 3% by volume of carbon dioxide, more suitably from about 0.1% to about 2% by volume of carbon dioxide, more suitably from about 0.1% to about 1% by volume of carbon dioxide, more suitably from about 0.1% to about 0.5% by volume of carbon dioxide in the gaseous product.

[0059] In one embodiment, the gaseous product comprises about 5% or less gaseous hydrocarbons by volume, preferably about 4% or less gaseous hydrocarbons by volume, more preferably about 3% or less gaseous hydrocarbons by volume, more preferably about 2% or less gaseous hydrocarbons by volume, more preferably about 1% or less gaseous hydrocarbons by volume, more preferably about 0.5% or less gaseous hydrocarbons by volume, in the gaseous product.

[0060] In one embodiment, the gaseous product comprises from about 0.1% to about 15% by volume of gaseous hydrocarbons. Suitably, from about 0.1% to about 12% by volume of the gaseous product, more suitably from about 0.1% to about 10% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 7% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 6% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 5% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 4% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 3% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 2% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 1% by volume of gaseous hydrocarbons, more suitably from about 0.1% to about 0.5% by volume of gaseous hydrocarbons in the gaseous product.

[0061] In one embodiment, the gaseous product is suitable for use as a fuel gas. In one embodiment, the gaseous product is synthesis gas.

[0062] In one embodiment, the method is carried out in an atmosphere that is substantially free of oxygen. Suitably, the atmosphere is free of oxygen. In another embodiment, the method comprises exposing a gaseous hydrocarbon to microwave radiation in an atmosphere that is substantially free of oxygen, suitably free of oxygen.

[0063] In another embodiment, the method is performed in an atmosphere that is substantially free of water.In another embodiment, the method comprises exposing a gaseous hydrocarbon to microwave radiation in an atmosphere that is substantially free of water.

[0064] In another embodiment, the method is performed in an atmosphere that is substantially free of oxygen and water. In another embodiment, the method comprises exposing a gaseous hydrocarbon to microwave radiation in an atmosphere that is substantially free of oxygen and water.

[0065] In another embodiment, the method is performed in an inert atmosphere. In another embodiment, the method comprises exposing the gaseous composition to microwave radiation in an inert atmosphere.

[0066] The inert atmosphere can be, for example, an inert gas or a mixture of inert gases. The inert gas or mixture of inert gases typically includes a noble gas, such as argon. In one embodiment, the inert gas is argon. In another embodiment, the inert gas is nitrogen.

[0067] The method may comprise purging the solid catalyst and / or the reaction vessel with an inert gas or a mixture of inert gases prior to exposing the gaseous hydrocarbon to microwave radiation.

[0068] In one embodiment, the method is carried out in the presence of water. In one embodiment, the method is carried out in the presence of oxygen. In one embodiment, the method is carried out in the presence of air. In one embodiment, the method is carried out in the presence of water and oxygen.

[0069] In one embodiment, the gaseous hydrocarbon is exposed to the solid catalyst before, during, or both before and during exposure to microwave radiation.

[0070] The gaseous hydrocarbon may be exposed to the catalyst by any suitable method, for example by continuously feeding the gaseous hydrocarbon over the catalyst, such as by using a fixed bed or a fluidised bed.

[0071] Any suitable space velocity may be used to feed the gaseous hydrocarbon onto the catalyst. For example, the gaseous hydrocarbon may be fed at a space velocity equal to or greater than about 1 hour. -1 For example, the gaseous hydrocarbons may be fed at a weight hourly space velocity (WHSV) of about 10 hr -1 The catalyst is fed at a weight hourly space velocity (WHSV) of about 100 hr. -1 , for example, equal to or greater than about 1000 hr -1 , or for example, equal to or greater than about 2000 hr -1 .

[0072] In one embodiment, the WHSV is about 100 hr -1 to about 500,000 hours-1 For example, WHSV is about 100hr -1 to about 400,000 hours -1 For example, WHSV is about 100hr -1 to about 300,000 hours -1 For example, WHSV is about 100hr -1 to about 200,000 hours -1 For example, WHSV is about 100hr -1 to about 100,000 hours -1 For example, WHSV is about 100hr -1 to about 50,000 hours -1 .

[0073] In one embodiment, the WHSV is about 100 hr -1 to about 500,000 hours -1 In another embodiment, the WHSV is about 1000 hr -1 to about 500,000 hours -1 For example, WHSV is about 1000hr -1 to about 400,000 hours -1 For example, WHSV is about 1000hr -1 to about 300,000 hours -1 For example, WHSV is about 1000hr -1 to about 200,000 hours -1 For example, WHSV is about 1000hr -1 to about 100,000 hours -1 For example, WHSV is about 1000hr -1 to about 50,000 hours -1 .

[0074] In the method of the present invention, gaseous hydrocarbons are exposed to microwave radiation in the presence of a catalyst to achieve or activate the decomposition of the hydrocarbons to produce gaseous products comprising hydrogen. The decomposition may be a catalytic decomposition. Exposing the gaseous hydrocarbons and catalyst to microwave radiation may cause them to heat up. Other possible effects of exposing the gaseous hydrocarbons and catalyst to microwave radiation (which may be electric or magnetic field effects) include, but are not limited to, field emission, plasma generation, and work function modification. For example, the high fields involved can change the catalyst work function and can cause the generation of plasma at the catalyst surface, thereby further changing the characteristics of the chemical process involved. Any one or more of these effects of microwave radiation may be responsible for, or at least contribute to, achieving or activating the catalytic decomposition of the gaseous hydrocarbons to produce gaseous products comprising hydrogen.

[0075] In principle, microwave radiation having any frequency in the microwave range, ie any frequency from 300 MHz to 300 GHz, may be employed in the present invention. However, typically, microwave radiation having a frequency from 900 MHz to 4 GHz or, for example, from 900 MHz to 3 GHz is employed.

[0076] In one embodiment, the microwave radiation has a frequency of from about 1 GHz to about 4 GHz. Suitably, the microwave radiation has a frequency of from about 2 GHz to about 4 GHz, suitably from about 2 GHz to about 3 GHz, suitably about 2.45 GHz.

[0077] The power at which microwave radiation needs to be delivered to the composition in order to achieve decomposition of hydrocarbons to produce hydrogen will vary depending on, for example, the specific hydrocarbon employed, the specific catalyst employed in the reaction, and the size, dielectric constant, particle packing density, shape, and morphology of the catalyst. However, one skilled in the art can readily determine the power level appropriate for achieving the reaction.

[0078] The method of the present invention may, for example, comprise exposing the gaseous hydrocarbon to microwave radiation that delivers at least 1 watt of power per cubic centimeter. However, it may comprise exposing the gaseous hydrocarbon to microwave radiation that delivers at least 5 watts of power per cubic centimeter.

[0079] Typically, for example, the method comprises exposing the gaseous hydrocarbon to microwave radiation delivering at least 10 watts or, for example, at least 20 watts per cubic centimeter. The method of the invention may, for example, comprise exposing the gaseous hydrocarbon to microwave radiation delivering at least 25 watts per cubic centimeter.

[0080] Typically, for example, the method comprises exposing the gaseous hydrocarbon to microwave radiation that delivers a power of from about 0.1 watts to about 5000 watts per cubic centimeter. More typically, the method comprises exposing the gaseous hydrocarbon to microwave radiation that delivers a power of from about 0.5 watts to about 1000 watts per cubic centimeter, or, for example, from about 1 watt to about 500 watts per cubic centimeter, such as from about 1.5 watts to about 200 watts, or, for example, from 2 watts to 100 watts per cubic centimeter.

[0081] In some embodiments, the method comprises exposing the gaseous hydrocarbon to microwave radiation that delivers about 5 watts to about 100 watts per cubic centimeter, or such as about 10 watts to about 100 watts per cubic centimeter, or such as about 20 watts, or about 25 watts to about 80 watts per cubic centimeter.

[0082] Typically, during the methods of the present invention, the power delivered to the gaseous hydrocarbon (or "absorbed power") increases. Thus, the method can include exposing the gaseous hydrocarbon to microwave radiation that delivers a first power to the composition, and then exposing the gaseous hydrocarbon to microwave radiation that delivers a second power to the gaseous hydrocarbon, wherein the second power is greater than the first power. The first power can, for example, be about 2.5 watts to about 6 watts per cubic centimeter of gaseous hydrocarbon. The second power can, for example, be about 25 watts to about 60 watts per cubic centimeter of gaseous hydrocarbon.

[0083] The duration of exposure of the composition to microwave radiation may also vary in the methods of the present invention. For example, embodiments are contemplated in which a given gaseous hydrocarbon is exposed to microwave radiation for a relatively long period of time to achieve a sustained decomposition of the hydrocarbon on a continuous basis to produce a gaseous product comprising hydrogen over a sustained period of time.

[0084] Electromagnetic heating offers a method for rapidly and selectively heating dielectric and magnetic materials. For example, rapid and efficient heating using microwaves, where the non-uniform field distribution and field focusing effects in dielectric mixtures can lead to significantly different product distributions, can result in enhanced reactions and new reaction pathways compared to conventional thermal processes. Furthermore, the high fields involved can alter the catalyst work function and can lead to the generation of plasma at the catalyst surface, further altering the characteristics of the chemical process involved.

[0085] Thus, the gaseous hydrocarbon may only need to be exposed to microwave radiation for a relatively short period of time. Typically, the exposure lasts for a duration of about 1 second to about 24 hours, for example in a batch process. Suitably, the method lasts for a duration of about 1 second to about 3 hours, more suitably for a duration of about 1 second to about 1 hour, more suitably for a duration of about 1 second to about 10 minutes, more suitably for a duration of about 1 second to about 5 minutes, more suitably for a duration of about 1 second to about 4 minutes, more suitably for a duration of about 1 second to about 3 minutes, more suitably for a duration of about 1 second to about 2 minutes, more suitably for a duration of about 1 second to about 1 minute.

[0086] In one embodiment, the method continues for a duration of about 10 seconds to about 3 hours, for example, in a batch process. Suitably, the method continues for a duration of about 10 seconds to about 1 hour, more suitably continues for a duration of about 10 seconds to about 10 minutes, more suitably continues for a duration of about 10 seconds to about 5 minutes, more suitably continues for a duration of about 10 seconds to about 5 minutes, more suitably continues for a duration of about 10 seconds to about 4 minutes, more suitably continues for a duration of about 10 seconds to about 3 minutes, more suitably continues for a duration of about 10 seconds to about 2 minutes, more suitably continues for a duration of about 10 seconds to about 1 minute.

[0087] In another embodiment, the method continues for a duration of about 30 seconds to about 3 hours, for example in a batch process. Suitably, the method continues for a duration of about 30 seconds to about 1 hour, more suitably continues for a duration of about 30 seconds to about 10 minutes, more suitably continues for a duration of about 30 seconds to about 5 minutes, more suitably continues for a duration of about 30 seconds to about 4 minutes, more suitably continues for a duration of about 30 seconds to about 3 minutes, more suitably continues for a duration of about 30 seconds to about 2 minutes, more suitably continues for a duration of about 30 seconds to about 1 minute.

[0088] The process, in particular the step of exposing the gaseous hydrocarbon to microwave radiation, is typically carried out at ambient temperature and pressure.

[0089] In one embodiment, the process of the present invention comprises heating the gaseous hydrocarbon and / or solid catalyst by exposing the gaseous hydrocarbon and / or solid catalyst to microwave radiation.

[0090] In one embodiment of the method, one or more of the following applies:

[0091] a) carrying out the process in the presence of water;

[0092] b) carrying out the process in the absence of any gaseous input other than gaseous hydrocarbons;

[0093] c) carrying out the method at ambient pressure; and

[0094] d) The process is carried out at ambient temperature.

[0095] In one embodiment, (b)-(d) above apply. In another embodiment, (b) and (c) above apply. In another embodiment, (a)-(d) above apply.

[0096] In another embodiment, the method further comprises the step of treating the (spent) catalyst with a source of carbon dioxide (to regenerate the catalyst).

[0097] In one embodiment, the process of the present invention comprises (i) exposing gaseous hydrocarbons to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species, and (ii) treating the (used) catalyst with a carbon dioxide source (thereby regenerating the catalyst).

[0098] As used herein, "used catalyst" refers to a catalyst after use directly in the reforming of gaseous hydrocarbons. In one embodiment, the carbon dioxide source is a gaseous source of CO2 (CO2(g)) (e.g., flue gas, calcined gas, biogas, or air) or a carbonate (suitably a hydrous carbonate).

[0099] For example, in one embodiment, the carbon dioxide source is selected from the group consisting of CO2(g), aqueous sodium carbonate, and aqueous ammonium carbonate.

[0100] In one embodiment, the catalyst regenerated in (ii) is used as a solid catalyst in (i), thereby providing a cycle of CO capture and utilization. In one embodiment, the cycle is repeated. In another embodiment, the cycle is performed up to about 100 times, or up to about 50 times, or up to about 30 times, or up to about 20 times, or up to about 15 times, or up to about 12 times.

[0101] In one embodiment, the process of the present invention comprises (i) exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species, and (ii) treating the spent catalyst with a carbon dioxide source to provide a regenerated solid catalyst; and (iii) exposing the gaseous hydrocarbon to microwave radiation in the presence of the regenerated solid catalyst.

[0102] In one embodiment, steps (i) to (iii) are repeated continuously. In one embodiment, (i) to (iii) are repeated 1 to 20 times, suitably 1 to 15 times, suitably 1 to 12 times, suitably 1 to 10 times, suitably 1 to 8 times, suitably between 1 and 6 times, suitably between 1 and 4 times.

[0103] In one embodiment, the spent catalyst is calcined prior to treatment with the carbon dioxide source.In one embodiment, the spent catalyst is calcined in air at a temperature of 500°C or more, suitably 600°C or more, suitably about 700°C.

[0104] In one embodiment, the spent catalyst is calcined every 4 cycles, suitably every 6 cycles, or every 8 cycles, or every 10 cycles, or every 12 cycles.

[0105] In one embodiment, the process of the present invention comprises (i) exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species, and (ii) optionally calcining the spent catalyst, (iii) treating the optionally calcined spent catalyst with a carbon dioxide source to provide a regenerated solid catalyst; and (iv) exposing a gaseous hydrocarbon to microwave radiation in the presence of the regenerated solid catalyst.

[0106] In one embodiment, the gaseous product is further processed to provide further useful products. For example, those skilled in the art will appreciate that the gaseous product can be subjected to a water gas shift in order to increase the proportion of hydrogen in the gaseous product.

[0107] Gaseous hydrocarbons

[0108] The gaseous hydrocarbons are in the gaseous state at standard ambient temperature and pressure (SATP), i.e., at a temperature of 298.15 K (25° C.) and 100,000 Pa (1 bar, 14.5 psi, 0.9869 atm). The gaseous hydrocarbons will generally also be in the gaseous state under the conditions (i.e., temperature and pressure) under which the process is carried out.

[0109] In one embodiment, the composition comprises only one gaseous hydrocarbon. In another embodiment, the composition comprises a mixture of gaseous hydrocarbons.

[0110] In one embodiment, the gaseous hydrocarbon is substantially free of oxygen-containing species. In another embodiment, the gaseous hydrocarbon is free of oxygen-containing species.

[0111] In one embodiment, the gaseous hydrocarbons consist essentially of one or more C 1-4 In one embodiment, the gaseous hydrocarbons consist essentially of one or more C 1-4 In another embodiment, the gaseous hydrocarbons are composed of one or more C 1-4 In another embodiment, the gaseous hydrocarbon is composed of 1-4 The single hydrocarbon composition of hydrocarbons.

[0112] In another embodiment, the gaseous hydrocarbon is selected from C 1-4 A single hydrocarbon of a hydrocarbon. Suitably, the gaseous hydrocarbon is selected from methane, ethane, propane, butane (e.g., n-butane or isobutane). Suitably, the gaseous hydrocarbon is selected from methane, ethane and propane. Suitably, the gaseous hydrocarbon is selected from methane and ethane.

[0113] Suitably, the gaseous hydrocarbon comprises methane. Suitably, the gaseous hydrocarbon consists essentially of methane. Suitably, the gaseous hydrocarbon consists of methane. Suitably, the gaseous hydrocarbon is methane.

[0114] In one embodiment, the gaseous hydrocarbons comprise about 70% by volume or more methane, suitably about 75% by volume or more methane, more suitably about 80% by volume or more methane, more suitably about 85% by volume or more methane, more suitably about 90% by volume or more methane, more suitably about 95% by volume or more methane, more suitably about 98% by volume or more methane, more suitably about 99% by volume or more methane.

[0115] In another embodiment, the gaseous hydrocarbon comprises from about 60% to about 100% by volume of methane, suitably from about 65% to about 100% by volume of methane, more suitably from about 70% to about 100% by volume of methane, more suitably from about 75% to about 100% by volume of methane, more suitably from about 80% to about 100% by volume of methane, more suitably from about 85% to about 100% by volume of methane, or more suitably from about 90% to about 100% by volume of methane, more suitably from about 100% by volume of methane.

[0116] Solid catalyst

[0117] In another aspect of the present invention, a solid catalyst is provided, comprising at least one metal species on a support, wherein the at least one metal species is a nickel species or a cobalt species, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0118] In one embodiment, the support comprises, consists essentially of, or consists of at least one carbonate salt.

[0119] In another embodiment, the support comprises, consists essentially of, or consists of at least one alkaline earth metal oxide.

[0120] The solid catalyst of the present invention is capable of absorbing microwaves. In one embodiment, the solid catalyst comprises at least one metal oxide on a support, wherein the metal oxide is at least one of nickel oxide or cobalt oxide, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0121] In one embodiment, the solid catalyst comprises at least one metal oxide on a support comprising a carbonate, wherein the metal oxide is at least one of nickel oxide or cobalt oxide.

[0122] In one embodiment, the solid catalyst comprises at least one metal species on a support consisting essentially of carbonate, wherein the metal species is at least one of a nickel species or a cobalt species.

[0123] In another embodiment, the solid catalyst comprises at least one metal species on a support composed of a carbonate, wherein the at least one metal species is a nickel species or a cobalt species.

[0124] In one embodiment, the metal species comprises a nickel species. In another embodiment, the metal species consists essentially of a nickel species. In another embodiment, the metal species consists of a nickel species. In another embodiment, the metal species is a nickel species.

[0125] In one embodiment, the nickel species is selected from nickel simple substance, nickel oxide, nickel salts, nickel alloys, nickel hydroxide and nickel carbide. Suitably, the nickel species is selected from nickel simple substance, nickel alloys, nickel oxide, nickel carbide and nickel hydroxide. Suitably, the nickel species is selected from nickel simple substance, nickel oxide, nickel carbide and nickel alloys. In one embodiment, the nickel species is selected from nickel simple substance, nickel oxide and mixtures thereof. In one embodiment, the nickel species is nickel oxide.

[0126] In one embodiment, the metal species comprises nickel, nickel oxide, or a mixture thereof. In another embodiment, the metal species consists essentially of nickel, nickel oxide, or a mixture thereof. In another embodiment, the metal species consists of nickel, nickel oxide, or a mixture thereof. In another embodiment, the metal species is nickel, nickel oxide, or a mixture thereof.

[0127] In one embodiment, the metal species comprises a cobalt species. In another embodiment, the metal species consists essentially of a cobalt species. In another embodiment, the metal species consists of a cobalt species. In another embodiment, the metal species is a cobalt species.

[0128] In one embodiment, the cobalt species is selected from the group consisting of cobalt, cobalt oxides, cobalt salts, cobalt alloys, cobalt hydroxides, and cobalt carbides. Suitably, the cobalt species is selected from the group consisting of cobalt, cobalt oxides, cobalt carbides, and cobalt alloys. In one embodiment, the cobalt species is selected from the group consisting of cobalt, cobalt oxides, and mixtures thereof.

[0129] In one embodiment, the metal species comprises cobalt, cobalt oxide, or a mixture thereof. In another embodiment, the metal species consists essentially of cobalt, cobalt oxide, or a mixture thereof. In another embodiment, the metal species consists of cobalt, cobalt oxide, or a mixture thereof. In another embodiment, the metal species is cobalt, cobalt oxide, or a mixture thereof.

[0130] In another embodiment, the catalyst comprises at least two metal species. In one embodiment, the catalyst comprises one or two metal species.

[0131] In one embodiment, the catalyst comprises at least one nickel species and at least one additional metal species, such as a metal element or a metal oxide. Suitably, the additional metal species is a transition metal species.

[0132] In one embodiment, the additional metal species is selected from cobalt, manganese, ruthenium, rhodium, palladium or platinum. Suitably, the additional metal species is selected from cobalt or manganese. Suitably, the cobalt species is cobalt, an oxide or a mixture thereof. Suitably, the manganese species is manganese, an oxide or a mixture thereof.

[0133] In one embodiment, the nickel species and the additional metal species are present in a molar ratio of about 1:1 to about 1:50, suitably about 1:1 to about 1:30, suitably about 1:1 to about 1:25, suitably about 1:1 to about 1:20.

[0134] In another embodiment, the nickel species and the additional metal species are present in a molar ratio of about 1:10 to about 1:50, suitably about 1:10 to about 1:30, suitably about 1:10 to about 1:25, suitably about 1:10 to about 1:20.

[0135] In another embodiment, the nickel species and the additional metal species are present in a molar ratio of about 1:15 to about 1:50, suitably about 1:15 to about 1:30, suitably about 1:15 to about 1:25, suitably about 1:15 to about 1:20, suitably about 1:19.

[0136] Typically, the catalyst comprises particles of the metal species. The particles are typically nanoparticles.

[0137] Suitably, where the metal species comprises / consists essentially of / consists of the metal in elemental form, the metal species is present as nanoparticles.

[0138] As used herein, the term "nanoparticle" refers to a microscopic particle whose size is typically measured in nanometers (nm). Nanoparticles typically have a particle size of 0.5 nm to 500 nm. For example, nanoparticles can have a particle size of 0.5 nm to 200 nm. More often, nanoparticles have a particle size of 0.5 nm to 100 nm, or, for example, 1 nm to 50 nm. Particles, such as nanoparticles, can be spherical or non-spherical. Non-spherical particles can, for example, be plate-shaped, needle-shaped, or tubular.

[0139] As used herein, the term "particle size" refers to the particle diameter if the particle is spherical, or the volume-based particle size if the particle is non-spherical. The volume-based particle size is the diameter of a sphere having the same volume as the non-spherical particle in question.

[0140] In one embodiment, the particle size of the metal species can be nanometer-sized. For example, the particle diameter of the metal species can be nanometer-sized.

[0141] As used herein, a nanometer-scale particle diameter refers to a population of nanoparticles having a d(0.5) value of 100 nm or less. For example, the d(0.5) value is 90 nm or less. For example, the d(0.5) value is 80 nm or less. For example, the d(0.5) value is 70 nm or less. For example, the d(0.5) value is 60 nm or less. For example, the d(0.5) value is 50 nm or less. For example, the d(0.5) value is 40 nm or less. For example, the d(0.5) value is 30 nm or less. For example, the d(0.5) value is 20 nm or less. For example, the d(0.5) value is 10 nm or less.

[0142] As used herein, "d(0.5)" (which may also be written as "d(v,0.5)" or volume median diameter) means the particle size (diameter) for which the cumulative volume of all particles in a population smaller than the d(0.5) value is equal to 50% of the total volume of all particles in the population.

[0143] Particle size distribution as described herein (e.g., d(0.5)) can be determined by various conventional analytical methods, such as laser light scattering, laser diffraction, sedimentation methods, pulsed methods, electrical zone sensing, sieve analysis, and optical microscopy (often combined with image analysis).

[0144] In one embodiment, the population of metal species of the catalyst has a d(0.5) value of about 1 nm to about 100 nm. For example, the d(0.5) value is about 1 nm to about 90 nm. For example, the d(0.5) value is about 1 nm to about 80 nm. For example, the d(0.5) value is about 1 nm to about 70 nm. For example, the d(0.5) value is about 1 nm to about 60 nm. For example, the d(0.5) value is about 1 nm to about 50 nm. For example, the d(0.5) value is about 1 nm to about 40 nm. For example, the d(0.5) value is about 1 nm to about 30 nm. For example, the d(0.5) value is about 1 nm to about 20 nm. For example, the d(0.5) value is about 1 nm to about 10 nm.

[0145] In another embodiment, the population of metal species of the catalyst has a d(0.5) value of about 10 nm to about 100 nm. For example, the d(0.5) value is about 10 nm to about 90 nm. For example, the d(0.5) value is about 10 nm to about 80 nm. For example, the d(0.5) value is about 10 nm to about 70 nm. For example, the d(0.5) value is about 10 nm to about 60 nm. For example, the d(0.5) value is about 10 nm to about 50 nm. For example, the d(0.5) value is about 10 nm to about 40 nm. For example, the d(0.5) value is about 10 nm to about 30 nm. For example, the d(0.5) value is about 10 nm to about 20 nm. For example, the d(0.5) value is about 10 nm.

[0146] In another embodiment, the population of metal species of the catalyst has a d(0.5) value of about 20 nm to about 100 nm. For example, the d(0.5) value is about 20 nm to about 90 nm. For example, the d(0.5) value is about 20 nm to about 80 nm. For example, the d(0.5) value is about 20 nm to about 70 nm. For example, the d(0.5) value is about 20 nm to about 60 nm. For example, the d(0.5) value is about 20 nm to about 50 nm. For example, the d(0.5) value is about 20 nm to about 40 nm. For example, the d(0.5) value is about 20 nm to about 30 nm. For example, the d(0.5) value is about 20 nm.

[0147] In another embodiment, the population of metal species of the catalyst has a d(0.5) value of about 30 nm to about 100 nm. For example, the d(0.5) value is about 30 nm to about 90 nm. For example, the d(0.5) value is about 30 nm to about 80 nm. For example, the d(0.5) value is about 30 nm to about 70 nm. For example, the d(0.5) value is about 30 nm to about 60 nm. For example, the d(0.5) value is about 30 nm to about 50 nm. For example, the d(0.5) value is about 30 nm to about 40 nm. For example, the d(0.5) value is about 30 nm.

[0148] In another embodiment, the population of metal species of the catalyst has a d(0.5) value of about 20 nm to about 100 nm. For example, the d(0.5) value is about 40 nm to about 90 nm. For example, the d(0.5) value is about 40 nm to about 80 nm. For example, the d(0.5) value is about 40 nm to about 70 nm. For example, the d(0.5) value is about 40 nm to about 60 nm. For example, the d(0.5) value is about 40 nm to about 50 nm. For example, the d(0.5) value is about 40 nm.

[0149] In another embodiment, the population of metal species of the catalyst has a d(0.5) value of about 50 nm to about 100 nm. For example, the d(0.5) value is about 50 nm to about 90 nm. For example, the d(0.5) value is about 50 nm to about 80 nm. For example, the d(0.5) value is about 50 nm to about 70 nm. For example, the d(0.5) value is about 50 nm to about 60 nm. For example, the d(0.5) value is about 50 nm.

[0150] The metal species of the solid catalyst described herein are supported on a support comprising a carbonate or an alkaline earth metal oxide. Suitably, the support comprises a carbonate.

[0151] In one embodiment, the support comprises one or more carbonates selected from alkali metal carbonates or alkaline earth metal carbonates.

[0152] In one embodiment, the support comprises one or more carbonates selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Cu, and Zn carbonates.

[0153] In one embodiment, the support comprises one or more carbonates selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, and Ba carbonates. Suitably, the support comprises one or more carbonates selected from the group consisting of Mg, Sr, Ba, and Ca carbonates.

[0154] In one embodiment, the carrier comprises calcium carbonate. In another embodiment, the carrier consists essentially of calcium carbonate. In another embodiment, the carrier consists of calcium carbonate. In another embodiment, the carrier is calcium carbonate.

[0155] In one embodiment, the support comprises an alkaline earth metal oxide. Suitably, the alkaline earth metal oxide is selected from one or more of calcium oxide (CaO), magnesium oxide (MgO) and barium oxide (BaO). Suitably, the alkaline earth metal oxide comprises calcium oxide (CaO). Suitably, the alkaline earth metal oxide is calcium oxide (CaO).

[0156] In one embodiment, the molar ratio of the metal species to the carbonate or alkaline earth metal oxide support in the solid catalyst is 1:100 or greater, such as 1:50 or greater, such as 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0157] In another embodiment, the molar ratio of the metal species in the solid catalyst to the carbonate or alkaline earth metal oxide support is from about 1:20 to about 1:5. Suitably, the ratio of the metal species in the solid catalyst to the carbonate or alkaline earth metal oxide support is from about 1:20 to about 1:9, for example from about 1:20 to about 1:12. Suitably, the ratio of the metal species in the solid catalyst to the carbonate is about 1:18.

[0158] In another embodiment, the molar ratio of the metal species to the carbonate or alkaline earth metal oxide support in the solid catalyst is from about 1:18 to about 1:5. Suitably, the molar ratio of the metal species to the carbonate in the solid catalyst is from about 1:18 to about 1:9, for example from about 1:18 to about 1:12.

[0159] In one embodiment, the catalyst has a molar ratio of metal species to carbonate support of about 1 :10 to about 1 :20.

[0160] In one embodiment, the catalyst has a molar ratio of metal species to alkaline earth metal oxide support of about 1:10 to about 1:20.

[0161] In one embodiment, the solid catalyst comprises: a nickel species, which is nickel, nickel oxide, nickel alloy, nickel carbide, or a mixture thereof; and an alkaline earth metal carbonate support. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0162] In one embodiment, the solid catalyst comprises: a nickel species, which is nickel, nickel oxide, or a mixture thereof; and an alkaline earth metal carbonate support. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0163] In one embodiment, the solid catalyst consists essentially of a nickel species, which is nickel, nickel oxide, nickel alloy, nickel carbide, or a mixture thereof; and an alkaline earth metal carbonate support. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0164] In one embodiment, the solid catalyst consists essentially of a nickel species, which is nickel, nickel oxide, or a mixture thereof; and an alkaline earth metal carbonate support. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0165] In one embodiment, the solid catalyst is a nickel element and / or nickel oxide supported on calcium carbonate. Suitably, the ratio of Ni to Ca in the catalyst is 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0166] In one embodiment, the solid catalyst is nickel and / or nickel oxide supported on calcium carbonate. Suitably, the ratio of Ni to Ca in the catalyst is from about 1:20 to about 1:5. Suitably, from about 1:20 to about 1:9, for example, from about 1:20 to about 1:12. Suitably, the ratio of nickel species to carbonate in the solid catalyst is from about 1:18.

[0167] In one embodiment, the solid catalyst is essentially composed of nickel and / or nickel oxide supported on calcium carbonate. Suitably, the ratio of Ni to Ca in the catalyst is 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0168] In one embodiment, the solid catalyst consists essentially of nickel and / or nickel oxide supported on calcium carbonate. Suitably, the ratio of Ni to Ca in the catalyst is from about 1:20 to about 1:5. Suitably, from about 1:20 to about 1:9, for example, from about 1:20 to about 1:12. Suitably, the ratio of nickel species to carbonate in the solid catalyst is from about 1:18.

[0169] In one embodiment, the solid catalyst consists of nickel oxide supported on calcium carbonate. Suitably, the ratio of Ni to Ca is about 1:18.

[0170] In one embodiment, the solid catalyst comprises a cobalt species, which is cobalt, cobalt oxide, cobalt alloy, cobalt carbide or a mixture thereof; and an alkaline earth metal carbonate. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0171] In one embodiment, the solid catalyst comprises a cobalt species, which is cobalt, cobalt oxide, or a mixture thereof; and an alkaline earth metal carbonate. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0172] In one embodiment, the solid catalyst is essentially composed of a cobalt species and an alkaline earth metal carbonate, wherein the cobalt species is cobalt, cobalt oxide, a cobalt alloy, cobalt carbide, or a mixture thereof. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0173] In one embodiment, the solid catalyst is essentially composed of a cobalt species and an alkaline earth metal carbonate, wherein the cobalt species is cobalt, cobalt oxide, or a mixture thereof. Suitably, the alkaline earth metal carbonate is selected from calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate. More suitably, the carbonate is calcium carbonate.

[0174] In one embodiment, the solid catalyst comprises cobalt and / or cobalt oxide supported on calcium carbonate. Suitably, the ratio of Co to Ca in the catalyst is 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0175] In one embodiment, the solid catalyst comprises cobalt and / or cobalt oxide supported on calcium carbonate. Suitably, the ratio of Co to Ca in the catalyst is from about 1:20 to about 1:5. Suitably, from about 1:20 to about 1:9, for example, from about 1:20 to about 1:12. Suitably, the ratio of cobalt species to carbonate in the solid catalyst is from about 1:18.

[0176] In one embodiment, the solid catalyst consists essentially of cobalt and / or cobalt oxide supported on calcium carbonate. Suitably, the ratio of Co to Ca in the catalyst is 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0177] In one embodiment, the solid catalyst consists essentially of cobalt and / or cobalt oxide supported on calcium carbonate. Suitably, the ratio of Co to Ca in the catalyst is from about 1:20 to about 1:5. Suitably, from about 1:20 to about 1:9, for example, from about 1:20 to about 1:12. Suitably, the ratio of cobalt species to carbonate in the solid catalyst is about 1:18.

[0178] In one embodiment, the solid catalyst consists of cobalt oxide supported on calcium carbonate. Suitably, the ratio of Co to Ca is about 1:18.

[0179] In one embodiment, the solid catalyst may comprise additives and / or promoters. Examples of suitable additives and / or promoters include cerium, titanium or zirconium species, such as cerium, titanium or zirconium or their oxides.

[0180] Heterogeneous mixture

[0181] In another aspect, the present invention provides a heterogeneous mixture comprising a solid catalyst in admixture (suitably intimately mixed) with a gaseous hydrocarbon, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species.

[0182] With respect to the solid catalyst, the gaseous hydrocarbon and characteristics thereof, each of the above-described embodiments applies equally to this aspect of the invention.

[0183] The present invention also relates to using the above heterogeneous mixture to provide a gaseous product comprising hydrogen.This can be achieved by exposing the heterogeneous mixture to microwave radiation as described above.

[0184] microwave reactor

[0185] In another aspect, the present invention relates to a microwave reactor comprising a heterogeneous mixture comprising a solid catalyst mixed (suitably intimately mixed) with a gaseous hydrocarbon, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species.

[0186] With respect to the solid catalyst, the gaseous hydrocarbon and characteristics thereof, each of the above-described embodiments applies equally to this aspect of the invention.

[0187] Typically, the reactor is configured to receive the gaseous hydrocarbon and the catalyst to be exposed to the radiation. Thus, the reactor typically includes at least one vessel or inlet configured to contain the gaseous hydrocarbon in a reaction chamber and / or deliver the gaseous hydrocarbon to the reaction chamber, which is the focus of the microwave radiation.

[0188] The reactor is also configured to output gaseous products. Thus, the reactor typically comprises an outlet through which gaseous products produced according to the process of the invention can be released or collected.

[0189] In some embodiments, the microwave reactor is configured to subject the composition to an electric field in TMO10 mode.

[0190] fuel cell module

[0191] In another aspect, the present invention provides a fuel cell module comprising (i) a fuel cell and (ii) a heterogeneous mixture comprising a solid catalyst mixed (suitably intimately mixed) with a gaseous hydrocarbon, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species.

[0192] Fuel cells, such as proton exchange membrane fuel cells, are well known in the art and are therefore readily available to those skilled in the art.

[0193] In one embodiment, the fuel cell module may further comprise (iii) a microwave radiation source. Suitably, the microwave radiation source is adapted to expose the gaseous hydrocarbon and the catalyst to microwave radiation, thereby decomposing the gaseous hydrocarbon or its components into gaseous products comprising hydrogen. The decomposition may be catalytic decomposition.

[0194] Suitably, the source of microwave radiation is a microwave reactor, as described above.

[0195] The present invention will now be further described in the following numbered paragraphs.

[0196] 1. A process for producing a gaseous product comprising hydrogen, the process comprising exposing a gaseous hydrocarbon to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support, wherein the metal species is at least one of a nickel species or a cobalt species, and wherein the support comprises at least one of a carbonate or an alkaline earth metal oxide.

[0197] 2. The method of paragraph 1, wherein the gaseous product comprises about 40% by volume or more of hydrogen, suitably about 70% by volume or more of hydrogen, suitably about 80% by volume or more, suitably about 90% by volume or more of hydrogen.

[0198] 3. The method of paragraph 1, wherein the gaseous product comprises from about 45 vol% to about 75 vol% hydrogen, more suitably from about 45 vol% to about 70 vol% hydrogen, more suitably from about 45 vol% to about 65 vol% hydrogen, or more suitably from about 45 vol% to about 60 vol% hydrogen, based on the total amount of the gaseous product.

[0199] 4. The method according to paragraph 1, wherein the gaseous product further comprises carbon monoxide.

[0200] 5. The method of paragraph 1, wherein the gaseous product comprises about 70% by volume or more of hydrogen and carbon monoxide based on the total amount of gaseous product, suitably about 80% by volume or more of hydrogen and carbon monoxide based on the total amount of gaseous product, more suitably about 90% by volume or more of hydrogen and carbon monoxide based on the total amount of gaseous product, and more suitably about 99% by volume or more of hydrogen and carbon monoxide based on the total amount of gaseous product.

[0201] 6. The method of paragraph 1, wherein the gaseous product comprises from about 60% to about 99% by volume of hydrogen and carbon monoxide based on the total volume of the gaseous product, suitably from about 75% to about 99% by volume of hydrogen and carbon monoxide based on the total volume of the gaseous product, and more suitably from about 80% to about 99% by volume of hydrogen and carbon monoxide based on the total volume of the gaseous product.

[0202] 7. The method according to any of the preceding paragraphs, wherein the gaseous product comprises about 5% by volume or less carbon dioxide.

[0203] 8. The method according to any of the preceding paragraphs, wherein the gaseous product comprises hydrogen and carbon monoxide in a molar ratio of hydrogen to carbon monoxide of about 1:1 to about 2:1.

[0204] 9. The process according to paragraph 1, wherein the gaseous product is synthesis gas.

[0205] 10. The method according to any of the preceding paragraphs, wherein the metal species is a nickel species.

[0206] 11. The method according to any of the preceding paragraphs, wherein the nickel species is selected from nickel element, nickel alloy, nickel oxide, nickel carbide and nickel hydroxide.

[0207] 12. The method according to any of the preceding paragraphs, wherein the nickel species is selected from elemental nickel, nickel oxide, and mixtures thereof.

[0208] 13. The method according to any of the preceding paragraphs, wherein the nickel species is nickel oxide.

[0209] 14. The method according to any of paragraphs 1 to 9, wherein the metal species is a cobalt species.

[0210] 15. The method according to paragraph 14, wherein the cobalt species is selected from the group consisting of elemental cobalt, cobalt alloys, cobalt oxide, cobalt carbide, and cobalt hydroxide.

[0211] 16. The method of paragraph 14, wherein the cobalt species is selected from the group consisting of elemental cobalt, cobalt oxide, and mixtures thereof.

[0212] 17. The method according to paragraph 14, wherein the cobalt species is cobalt oxide.

[0213] 18. The process according to any of the preceding paragraphs, wherein the catalyst comprises one or two metal species.

[0214] 19. The process of paragraph 18, wherein the catalyst comprises at least one nickel species and at least one additional metal species, such as a metal or a metal oxide.

[0215] 20. The method of paragraph 19, wherein the additional metal species is a transition metal species, the transition metal species suitably selected from cobalt or manganese species.

[0216] 21. A method according to any preceding paragraph, wherein the support is a carbonate, suitably an alkali metal carbonate or an alkaline earth metal carbonate.

[0217] 22. The process according to any one of the preceding paragraphs, wherein the support comprises one or more carbonates selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba carbonates, suitably, the support comprises one or more carbonates selected from the group consisting of Mg, Sr, Ba and Ca carbonates.

[0218] 23. The method according to any of the preceding paragraphs, wherein the carrier is calcium carbonate.

[0219] 24. The method according to any of the preceding paragraphs, wherein the molar ratio of metal species to carbonate or alkaline earth metal oxide support in the solid catalyst is 1:24 or greater, such as 1:20 or greater, such as 1:18 or greater, such as 1:12 or greater, such as 1:9 or greater.

[0220] 25. The process according to any of the preceding paragraphs, wherein the catalyst has a molar ratio of metal species to carbonate of about 1:10 to about 1:20.

[0221] 26. The method according to any of the preceding paragraphs, wherein the catalyst has a molar ratio of metal species to carbonate of about 1:18.

[0222] 27. The process according to paragraphs 1 to 9, wherein the solid catalyst comprises a nickel species and an alkaline earth metal carbonate, the nickel species being elemental nickel, nickel oxide or a mixture thereof, the alkaline earth metal carbonate being suitably selected from calcium carbonate, magnesium carbonate, strontium carbonate and barium carbonate.

[0223] 28. The method of paragraphs 1 to 9, wherein the solid catalyst comprises nickel and / or nickel oxide supported on calcium carbonate, suitably, wherein the ratio of Ni to Ca in the catalyst is from about 1:20 to about 1:5, suitably, from about 1:20 to about 1:9, for example from about 1:20 to about 1:12, suitably, the ratio of nickel species to carbonate in the solid catalyst is about 1:18.

[0224] 29. The process according to any of the preceding paragraphs, wherein the catalyst further comprises an additive and / or promoter, such as a cerium additive or promoter.

[0225] 30. The method according to any of the preceding paragraphs, wherein the gaseous hydrocarbon is selected from one or more of methane, ethane, propane and butane.

[0226] 31. The method according to any of the preceding paragraphs, wherein the gaseous hydrocarbon comprises methane.

[0227] 32. A method according to any preceding paragraph, wherein the gaseous hydrocarbons comprise 90% by volume or more methane, suitably about 95% by volume or more methane.

[0228] 33. The method according to any one of the preceding paragraphs, wherein the -1 to about 200,000 hours -1 The gaseous hydrocarbon is fed over the catalyst at a weight hourly space velocity (WHSV) of 1.5 wt %.

[0229] 34. The method of any of the preceding paragraphs, wherein the exposure to microwave radiation is for a duration of from about 10 seconds to about 3 hours, suitably from about 10 seconds to about 10 minutes, suitably from about 10 seconds to about 5 minutes, more suitably from about 10 seconds to about 1 minute.

[0230] 35. The method of any of the preceding paragraphs, wherein one or more of (a) to (d) applies:

[0231] a) carrying out the process in the presence of water;

[0232] b) carrying out the process in the absence of any gaseous input other than gaseous hydrocarbons;

[0233] c) carrying out the method at ambient pressure; and

[0234] d) The process is carried out at ambient temperature.

[0235] 36. The method of any of the preceding paragraphs, further comprising (ii) treating the spent catalyst with a source of carbon dioxide to provide a regenerated catalyst.

[0236] 37. The method of paragraph 36, wherein the carbon dioxide source is gaseous carbon dioxide, sodium carbonate, or ammonium carbonate.

[0237] 38. The process according to paragraphs 36 and 27, wherein the regenerated catalyst is used as the solid catalyst in the process according to any one of paragraphs 1 to 35.

[0238] 39. The method of paragraph 38, wherein the method is repeated one or more times, suitably up to 100 times, or up to 50 times, or up to 30 times, or up to 20 times, or up to 15 times, or up to 12 times.

[0239] 40. The process of any of paragraphs 36 to 39, wherein the spent catalyst is calcined prior to treatment with the carbon dioxide source.

[0240] 41. A solid catalyst comprising one or more metal oxides on a support comprising a carbonate, wherein the metal oxide is selected from nickel oxide or cobalt oxide.

[0241] 42. The solid catalyst according to paragraph 41, wherein the metal oxide comprises nickel oxide, suitably the metal oxide is nickel oxide.

[0242] 43. The solid catalyst according to paragraph 42, wherein the carbonate is calcium carbonate.

[0243] 44. The solid catalyst of paragraph 43, wherein the catalyst has a molar ratio of nickel to calcium carbonate of about 1:10 to about 1:20.

[0244] 45. The solid catalyst of paragraph 43, wherein the catalyst has a molar ratio of nickel to calcium carbonate of about 1:18.

[0245] 46. A heterogeneous mixture comprising a solid catalyst mixed with a gaseous hydrocarbon, wherein the catalyst comprises at least one metal species on a support comprising a carbonate, wherein the metal species is at least one of a nickel species or a cobalt species.

[0246] 47. The heterogeneous mixture according to paragraph 46, wherein the solid catalyst is according to any one of paragraphs 41 to 45.

[0247] 48. A microwave reactor comprising the heterogeneous mixture of any of paragraphs 46 to 47.

[0248] 50. A fuel cell module comprising (i) a fuel cell and (ii) the heterogeneous mixture according to any of paragraphs 46 to 47.

[0249] Example

[0250] Methods and Materials

[0251] Catalyst preparation

[0252] The required amount of carbonate powder was dispersed in 30 mL of deionized water using a magnetic stirrer. Then, the corresponding amount of metal nitrate was added to the carbonate suspension and kept stirring for 30 minutes. The water in the suspension was evaporated at 100 ° C to form a uniform slurry. Subsequently, the slurry was dried in an 80 ° C oven overnight and calcined at 500 ° C for 1 hour. Finally, the obtained metal / carbonate solid (denoted as MO x / carbonate, M represents a metal) is crushed into a fine powder for use.

[0253] In the following preparations, the total weight of CaCO₃ and metal oxides was fixed at 5 g, while the molar ratio of Ca to metal was varied for each sample. CaCO₃ powder and all metal nitrates were received from Sigma-Aldrich and Fisher, respectively. All reagents had a purity greater than 99% and were used without further purification.

[0254] Microwave-induced hydrocarbon reforming

[0255] Microwave reforming was performed on a setup consisting of a single-mode microwave generation system, a custom-made microwave cavity, and a control system. Figure 1Before the microwave reaction, a 0.5 g sample of MOx / carbonate (e.g., NiO / CaCO3) was loaded into an ID=8 mm quartz tube, which was then placed into the microwave cavity with the catalyst bed located in the center of the cavity. After the quartz tube reactor was installed, the flow system was purged with pure hydrocarbon (e.g., methane) at a flow rate of 150 mL / min for 15 minutes, and the hydrocarbon flow was then adjusted to the desired flow rate for the reforming reaction.

[0256] In each experiment, when the microwave was turned on, the outlet gas was immediately collected by measuring the graduated cylinder (the pH of the water was adjusted to 4 using dilute H2SO4 to eliminate CO2 dissolution to ensure data accuracy). After the sample was irradiated for 150 seconds, gas collection and microwave power were stopped simultaneously. The volume of the collected gas was recorded, and the gas composition was determined by gas chromatography (GC, PerkinElmer Clarus 580).

[0257] In this process, for example, when the carbonate is CaCO3, it will decompose to form CaO and CO2, and the released CO2 will be reformed in situ and quickly with hydrocarbons (such as methane) to produce a gaseous product (such as synthesis gas) containing hydrogen. It should also be noted that there is no need to activate MO x The loaded metals on the NH3 / carbonate samples are thus much simpler than the conventional thermal methane dry reforming process, in which the loaded metal oxides need to be pre-reduced to the metallic state.

[0258] CO2 capture (catalyst regeneration)

[0259] The residue of the metal / carbonate catalyst-absorbent system after hydrocarbon reforming was carbonated using 50% CO₂ in water as a medium to simulate direct CO₂ capture from flue gas. Typically, 1 g of the spent catalyst was dispersed in 20 mL of deionized water, and 100 mL / min of CO₂ was passed through the suspension for 3 hours. The regenerated suspension was then filtered and dried in an 80°C oven for the next cycle of the reforming reaction.

[0260] In the nickel / carbonate catalyst regeneration step, aqueous Na2CO3 and NH4HCO3 solutions are also used to carbonate the residue after the reforming reaction. The basic principle of using Na2CO3 and NH4HCO3 as carbonate sources in an H2O medium to regenerate the reacted metal / calcium bifunctional catalyst system lies in reactions (1) to (3). The aqueous solution can then be used for carbon capture (reaction 4).

[0261] Na2CO3+H2O+CaO=CaCO3↓+2NaOH (Reaction 1)

[0262] 2NaOH + CO2 = Na2CO3 + H2O (Reaction 2)

[0263] NH4HCO3+CaO=CaCO3↓+NH3·H2O (Reaction 3)

[0264] NH3·H2O+CO2=NH4HCO3 (Reaction 4)

[0265] Data Analysis

[0266] By measuring the gas volume recorded in the graduated cylinder and using GC, the gas volume composition and the amount of H2, CO and CO2 generated can be calculated. Subsequently, the conversion of carbonates and the released CO2 can be calculated.

[0267] The reactions involved in the methane dry reforming process with CaCO3 as CO2 carrier are listed below:

[0268] CaCO3 → CaO + CO2 (Reaction 5)

[0269] CO2 + CH4 → 2CO + 2H2 (Reaction 6)

[0270] CH4→C+2H2 (Reaction 7)

[0271] (xy)H2+MO x →MO y +(xy)H2O (Reaction 8)

[0272] H2 + CO2 → H2O + CO (Reaction 9)

[0273] In all tested MO x In the / CaCO3 sample, the highest metal to calcium molar ratio is only 1:9, indicating that the portion of reaction (8) that contributes to the overall reforming process is very small. In addition, the amount of water collected in the cold trap during the reaction is negligible. Therefore, the occurrence of reactions (8) and (9) calculated for CaCO3 decomposition and CO2 conversion can be ignored. Therefore, the conversion rate (X) of CaCO3 decomposition and CO2 reforming with CH4 can be calculated as equations (1) and (2). In these equations, n represents the molar amount of each component.

[0274] ·X CaCO3 =(n CO2 +1 / 2n CO ) / n CO2理论 ×100% (Formula 1)

[0275] ·X CO2 =1 / 2n CO / (n CO2 +1 / 2n CO )×100% (Formula 2)

[0276] It can cause excessive cracking of CH4, and when CaCO3 has been deeply decomposed, carbon will be deposited in the formed MO y / CaO, and no further CO2 will be released before the microwave irradiation is stopped at t = 150 seconds, and then the ratio of H2 to CO will be greater than 1.0. Under this condition, the amount of carbon deposition can be calculated as formula (3):

[0277] ·n C =(n H2 -n CO ) / 2 (Formula 3)

[0278] Mass balance (MB) (%) = [(1 / 2n CO +n CO2 )×M CO -1 / 2(n H2 -n CO )×M C ] / (m0-m r )×100% (Formula 4)

[0279] Here, m0 and m r Respectively represent the total weight before and after the methane reforming reaction (including the reactor, sample, quartz wool, etc.).

[0280] Results and discussion

[0281] Methane reforming performance of different metals supported on CaCO3

[0282] Catalyst samples containing Fe, Mn, Ni, and Co oxides supported on CaCO powder were tested. For easier comparison, the metal-to-CaCO molar ratio for the tested samples was fixed at 1:18. In all methane reforming experiments, the CH flow rate and microwave input power were set at 100 mL / min and 750 W, respectively. The reforming results are shown in Figure 2.

[0283] As shown in Figure 2, the best methane reforming results were achieved on nickel oxide supported on CaCO (NiO / CaCO). In the NiO / CaCO bifunctional system, CaCO was almost completely decomposed with a conversion of 92.6%, and the CO released was also effectively reformed with CH in situ to form synthesis gas (CO conversion of 74.7%). The H and CO obtained were 8.32 and 6.58 mmol, respectively (if CaCO was completely decomposed and the released CO could be reformed 100% with CH, the amount of H and CO obtained would be 9.5 mmol).

[0284] The performance of the metal / calcium bifunctional system was modified by loading different metal oxides. All loaded metal oxides enhanced the decomposition of CaCO3 under microwave irradiation. However, the reforming of CH4 with the released CO2 was different. For example, although Fe oxide was able to promote the decomposition of CaCO3 (77.4%), the catalytic reforming ability of Fe oxide was weak and only 7.1% of the released CO2 was converted. It is obvious that loaded Mn, Co and Ni-Mn oxides also promoted the decomposition of CaCO3 and the activation of the released CO2, however the levels of generated H2 and CO were lower than those obtained on NiO / CaCO3.

[0285] Therefore, among all these transition metals tested, nickel is the best for simultaneously enhancing CaCO3 decomposition and reforming CO2 with CH4 under microwave irradiation, although cobalt and Ni / Mn are capable of reforming methane to hydrogen-containing gases.

[0286] Effect of Ni / Ca ratio on reforming performance

[0287] To find the optimal Ni / Ca ratio for the methane reforming reaction and subsequent CO capture step, several CaCO3-supported nickel oxide samples were synthesized and their performance was evaluated under the same experimental conditions as above (CH4 flow rate 100 mL / min, microwave input power 750 W). The reforming results are shown in Figure 3.

[0288] The decomposition of CaCO3 can be significantly enhanced by increasing the NiO loading. Figure 3A ), and when the Ni / Ca ratio is 1:18, the CaCO3 conversion rate can exceed 90%. The CaCO3 conversion rate on the NiO / CaCO3 sample with a Ni / Ca ratio of 1:9 can reach 97.8%, which is slightly higher than the CaCO3 conversion rate on the NiO / CaCO3 (1:18) sample. However, the methane reforming performance on the NiO / CaCO3 sample with a Ni / Ca ratio of 1:9 is not as good as that on the NiO / CaCO3 sample with a Ni / Ca ratio of 1:18.

[0289] like Figure 3B As can be seen in the graph, when the proportion of nickel in the Ni / Ca ratio is higher than 1:24, the H2 / CO ratio in the gaseous product will be greater than 1, which means that the methane cracking reaction (CH4=C+2H2) is more advantageous than carbon gasification (C+CO2=2CO), thus leading to carbon deposition on the sample when the Ni / Ca ratio is higher than a certain level. For the NiO / CaCO3 sample with a Ni / Ca ratio of 1:9, the H2 / CO ratio in the gaseous product is 1.8, which is much higher than the H2 / CO ratio (1.26) on the NiO / CaCO3 (1:18) sample, indicating that carbon deposition occurs on the catalyst when the Ni / Ca ratio is 1:9.

[0290] Carbon deposition will cover the nickel particles and cause the loss of nickel active sites of the catalyst, thus leading to poor methane reforming performance with CO 2. Therefore, it is preferred to control the nickel oxide content loaded on the CaCO 3 powder so that the nickel / calcium bifunctional system can provide almost equal capabilities for methane cracking and carbon gasification.

[0291] On the NiO / CaCO3 sample with a Ni / Ca ratio of 1:18, CaCO3 can be extensively decomposed (92.6% conversion) to CaO, and this extensive CaCO3 decomposition will provide the sample with high CO2 absorption capacity in the subsequent CO2 capture step. In addition, 74.7% of the released CO2 (the highest among the samples tested) can be effectively reformed with CH4 into synthesis gas, achieving overall and excellent performance. Therefore, considering both CaCO3 decomposition and methane reforming with released CO2, the preferred Ni / Ca ratio for the NiO / CaCO3 bifunctional system in these test samples is 1:18.

[0292] Reforming results with different CH4 flow rates

[0293] The effect of CH4 flow rate was studied, and the reforming results were obtained by fixing the CH4 feed flow rate at 50, 100, and 150 mL / min (Figure 4).

[0294] As shown in Figure 4, the preferred CH4 feed flow rate under the operating conditions is 100 mL / min. The appropriate CH4 feed flow rate should provide enough CH4 to reform with the CO2 released in situ from the decomposition of CaCO3 without removing CO2 and heat from the reactor before the reforming reaction is complete.

[0295] Representative "contact time" experiments on NiO / CaCO3 samples with a Ni / Ca ratio of 1:18 were also performed using Figure 1 The “contact time” experiment was performed using the setup shown in .

[0296] Prior to the microwave reaction, a 0.5 g sample of MOx / CaCO3 (e.g., NiO / CaCO3) was loaded into an ID=8 mm quartz tube, which was then placed into the microwave cavity with the catalyst bed located in the center of the cavity. After the quartz tube reactor was properly connected, the flow system was purged with pure methane at a flow rate of 150 mL / min for 15 minutes. The methane flow rate was then adjusted to 100 mL / min, and the system was ready for microwave irradiation. The outlet gas was collected immediately after the microwave power was turned on, and gas samples were collected for 30 seconds each and analyzed by GC. In other words, the gas was collected, stored, and measured in metering cylinder #1 during the 0-30 second time period, and then analyzed by GC. At t=30 seconds, the overflow valve was immediately switched to metering cylinder #2, and gas samples were collected in this cylinder for the 31-60 second time period. Similarly, the outlet gas was collected and measured in separate graduated cylinders for the 61-90, 91-120, and 121-150 second time periods, and then analyzed by GC. (NB. The water pH was adjusted to 4 using dilute H2SO4 to eliminate CO2 dissolution to ensure data accuracy)

[0297] As shown in Figure 5, the methane reforming process can be extremely rapid (within 150 seconds) under microwave irradiation, with CaCO3 decomposition and methane reforming with the released CO2 occurring primarily within the 60 to 150 second time period, and the absorbed microwave power also increasing within this time period. Within the 121 to 150 second time period, we can see that the H2 / CO ratio is above 1, indicating that methane cracking is much stronger than carbon gasification, which can be attributed to the fact that CaCO3 is almost completely decomposed and no additional CO2 can be released for carbon gasification, and therefore more H2 is produced than CO in this time period.

[0298] It should also be noted that the catalyst temperature measured throughout the reforming process was below 200°C, indicating that the reforming reaction was able to complete without generating significant heat. This helps improve the energy efficiency of the methane reforming and CO2 capture process.

[0299] Cyclic Methane Reforming over Ni / Carbonate Catalysts Regenerated with CO2

[0300] As previously described, the spent catalyst after the methane reforming reaction is collected and regenerated using CO2 in a H2O medium. This CO2 regeneration step simulates industrial CO2 capture from flue gas and uses a CaO-based absorbent to absorb CO2 from the atmosphere.

[0301] From the above results, it can be seen that the methane reforming reaction can be directly initiated by nickel oxide supported on CaCO3 under microwave irradiation, thus eliminating the need for H2 pre-reduction of the sample. Therefore, this microwave-assisted methane reforming on NiO / CaCO3 samples is easier than traditional thermal processes starting from CaO for CO2 capture (operated below 650°C) and conversion (usually above 750°C), in which the supported metals require H2 pre-reduction. Therefore, the present method can start directly from the nickel oxide / CaCO3 composite and avoid the use of large amounts of calcium salts such as calcium nitrate and calcium acetate to prepare the CaO absorbent, thereby reducing pollutant emissions (nitrogen oxides or CO2) and making the sample preparation process easier, cheaper, and greener.

[0302] It is also noteworthy that nickel in the oxide state was able to effectively start the methane reforming process with the help of microwaves, indicating that the initial state of the nickel, whether in the oxide or metallic state, is not important. This is beneficial in real-world scenarios such as direct CO2 capture from the atmosphere and flue gases where they will encounter water and oxygen.

[0303] Cyclic methane reforming and CO 2 capture experiments over a catalyst with a Ni / Ca ratio of 1:18 were conducted and the results are shown in FIG6 .

[0304] In this experiment, for every four cycles, the spent catalyst after the methane reforming reaction was calcined in air at 700°C for 2 hours to remove deposited carbon and then regenerated by CO2 treatment for the next methane reforming cycle. In methane reforming, the CaCO3 conversion rate was able to remain above 90% for 12 cycles, and more than 55% of the released CO2 was able to be reformed in situ into synthesis gas with CH4, demonstrating the sufficient stability of the nickel / carbonate system for cyclic methane reforming and CO2 capture.

[0305] Cyclic reforming over catalysts regenerated from different carbonate sources

[0306] For the catalyst regeneration using Na2CO3 and NH4HCO3, 1 g of the spent sample (Ni / Ca ratio of 1:18) after the methane reforming reaction was dispersed in 30 mL of solution (containing 20 mmol of Na2CO3 and 40 mmol of NH4HCO3, respectively) and stirred for 3 hours. The sample regenerated by Na2CO3 was filtered and rinsed 3 times to remove Na + The samples regenerated by Na2CO3 and NH4HCO3 were both dried at 80°C overnight.

[0307] The cyclic methane reforming performance of samples regenerated by CO2 (g), Na2CO3 and NH4HCO3 was tested under the same conditions (100 mL / min CH4 flow, 750 W microwave input power, 0.5 g regenerated sample in each test), and the results are shown in Figure 7.

[0308] As shown in Figure 7, the microwave-induced cyclic methane reforming performance of the samples regenerated by CO (g), Na CO and NH HCO was very similar and was able to remain at a high level for at least four consecutive cycles. In each cycle, CaCO was almost completely decomposed and the calculated conversion was higher than 90%. Although the CO conversion showed a decreasing trend, it can be attributed to carbon deposition on the nickel sites. However, the CO conversion remained at a level higher than 55%.

[0309] The proposed bifunctional nickel / carbonate catalyst is applicable to different regeneration strategies using CO2(g), Na2CO3 or NH4HCO3 as CO2 sources, and these varying CO2 sources can help the nickel / carbonate system be applicable to different CO2 capture situations encountered in industry.

[0310] Sample morphology changes

[0311] The morphological changes of nickel / carbonate catalyst with Ni / Ca ratio of 1:18 before and after methane reforming reaction and after CO2 regeneration were analyzed. Figure 8 Shown in.

[0312] As in Figure 8 A and Figure 8 As seen in B, the nickel / carbonate system has the appearance of cubic particles, and the surface of the particles is covered with hair-like carbon after the methane reforming reaction. Figure 8 E and Figure 8 As confirmed by the TEM image shown in Figure 5, nickel oxide nanoparticles are dispersed on the surface of the CaCO3 cubic support and the nickel nanoparticles are encapsulated by the deposited filamentous carbon, which is consistent with the small decrease in methane reforming performance in the cycling experiments due to carbon deposition on the nickel sites.

[0313] After CO2 regeneration in H2O medium, cubic calcium particles separated into small pieces with much smaller size, and these small pieces aggregated into a flower-like appearance ( Figure 8 C). TEM image ( Figure 8 G) Demonstrates that improved nickel particle dispersion is beneficial for microwave-induced methane reforming.

[0314] exist Figure 8In D and 8H, it can be seen that the nickel / carbonate catalyst after 12 cycles of CO2 capture and methane reforming is still small flakes, and the nickel nanoparticles are well dispersed. At this stage, the CaO absorbent (also as a support for the nickel particles) has a porous nanostructure that can help improve CO2 capture. All these morphological results show that the sample structure changes will not adversely affect the cyclic CO2 capture and methane reforming performance of this nickel / carbonate dual-function system.

[0315] summary

[0316] Metal oxide / carbonate catalysts can be used as catalysts to efficiently and directly reform methane to gaseous products comprising hydrogen under microwave irradiation.

[0317] Carbonate serves as CO carrier and adsorbent precursor.Under microwave radiation, the metal species of load can enhance the CO that carbonate decomposes and in-situ catalysis releases to reform gaseous hydrocarbons into gaseous products comprising hydrogen.The adsorbent formed on carbonate decomposer (for example, when carbonate is CaCO time is CaO) is used as the absorbent of subsequent CO capture.Therefore, realize cyclic in-situ methane reforming and CO capture process.

[0318] Various transition metal (oxide) systems are effective, with nickel being preferred (nickel is effective in both the oxide and metallic states). No H2 pre-reduction of the catalyst is required, and methane reforming can be initiated directly even when the supported metal is in the oxide state.

[0319] Using NiO x The cyclic CO2 capture and methane reforming of the / CaCO3 system extensively decomposes carbonates (typically about 90%) and produces ≥55% CO2 which is reformed with CH4 in one step.

[0320] Various CO2 sources (CO2(g), Na2CO3, and NH4HCO3) can be used to regenerate the catalyst, and the regenerated catalyst showed methane reforming performance similar to that of the fresh sample.

[0321] References

[0322] 1.Tian, S., Yan, F., Zhang, Z., & Jiang, J. (2019). Calcium-looping reforming of methane realizes in situ CO2 utilization with improved energyefficiency. Science advances, 5(4), eaav5077.

[0323] 2.Jie,X.,Gonzalez-Cortes,S.,Xiao,T.,Yao,B.,Wang,J.,Slocombe,D.R.,Edwards,P.P.&Thomas,J.M.(2019).The decarbonisation of petroleum and otherfossil hydrocarbon fuels for the facile production and safe storage ofhydrogen.Energy&Environmental Science,12(1),238-249.

[0324] 3.Pakhare,D.,&Spivey,J.(2014).A review of dry(CO2)reforming ofmethane over noble metal catalysts.Chemical Society Reviews,43(22),7813-7837.

[0325] 4.Sun,H.,Wang,J.,Zhao,J.,Shen,B.,Shi,J.,Huang,J.,&Wu,C.(2019).Dualfunctional catalytic materials of Ni over Ce-modified CaO sorbents forintegrated CO2 capture and conversion.Applied Catalysis B:Environmental,244,63-75.

[0326] 5.Blamey,J.,Anthony,E.J.,Wang,J.,&Fennell,P.S.(2010).The calciumlooping cycle for large-scale CO2 capture.Progress in Energy and CombustionScience,36(2),260-279.

[0327] 6. Zhang,

[0328] All references, including publications, patent applications, and patents, cited herein are incorporated by reference in their entirety to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein (to the maximum extent permitted by law).

[0329] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0330] Unless otherwise specified, the use of any and all examples or exemplary language (e.g., "such as") provided herein is intended merely to better illustrate the invention and does not limit the scope of the invention. No language in this specification should be construed as indicating any non-graphic element as essential to the practice of the invention.

[0331] The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability, and / or enforceability of such patent documents.

[0332] This invention includes all modifications and equivalents of the subject matter recited in the following paragraphs as permitted by applicable law.

Claims

1. A process for producing a gaseous product comprising hydrogen and carbon monoxide, the process comprising exposing gaseous hydrocarbons to microwave radiation in the presence of a solid catalyst, wherein the catalyst comprises at least one metal species on a support, wherein the metal species is at least one of a nickel species or a cobalt species, and wherein the support comprises calcium carbonate, and wherein the solid catalyst temperature is below 200° C. during exposure to microwave radiation.

2. The method according to claim 1, wherein the gaseous product comprises 90% by volume or more of hydrogen and carbon monoxide based on the total amount of the gaseous product.

3. A process according to claim 1 or 2, wherein the gaseous product comprises hydrogen and carbon monoxide in a molar ratio of hydrogen to carbon monoxide of 1:1 to 2:

1.

4. The method according to claim 1 or 2, wherein the metal species is a nickel species.

5. The method according to claim 1 or 2, wherein the nickel species is selected from the group consisting of nickel element, nickel oxide and mixtures thereof.

6. The method according to claim 1 or 2, wherein the carrier is calcium carbonate.

7. The method according to claim 1 or 2, wherein the catalyst has a molar ratio of nickel to calcium carbonate of 1:10 to 1:

20.

8. The method of claim 1 or 2, wherein the catalyst has a molar ratio of nickel to calcium carbonate of 1:

18.

9. The method according to claim 1 or 2, wherein the solid catalyst consists of nickel and / or nickel oxide supported on calcium carbonate.

10. The method according to claim 1 or 2, wherein the gaseous hydrocarbon is selected from one or more of methane, ethane, propane and butane.

11. The process according to claim 1 or 2, wherein the gaseous hydrocarbons comprise at least 90% by volume of methane.

12. The method of claim 1 or 2, further comprising treating the spent catalyst with a source of carbon dioxide.

13. The method of claim 12, wherein the carbon dioxide source is a gaseous carbon dioxide source, a sodium carbonate source, or an ammonium carbonate source.

14. The method according to claim 12, wherein a catalyst treated with a carbon dioxide source is used as the solid catalyst in the method according to any one of claims 1 to 11.

15. The method of claim 12, wherein the spent catalyst is calcined prior to treatment with the carbon dioxide source.

16. Use of a solid catalyst in a process for producing a gaseous product comprising hydrogen and carbon monoxide, wherein the solid catalyst comprises a metal oxide on a support comprising calcium carbonate, wherein the metal oxide is nickel oxide, and wherein the catalyst has a molar ratio of nickel to calcium carbonate of from 1:10 to 1:20, and wherein the process comprises exposing a gaseous hydrocarbon to microwave radiation in the presence of the solid catalyst, and wherein the temperature of the solid catalyst is below 200°C during exposure to microwave radiation.

17. Use according to claim 16, wherein the catalyst has a molar ratio of nickel to calcium carbonate of 1:18.

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