WO2012079179A1 - Methods, systems and catalysts for supercritical water reforming feedstock into methane - Google Patents

Abstract

The present application pertains to the methods, systems and catalysts for supercritical water reforming of feedstocks, such as ethanol, into methane. A bimetallic nickel and ruthenium catalyst and method of making the catalyst is also disclosed as well as the use of the catalyst in supercritical water reforming of feedstocks. The methods, systems and catalysts are useful in batch and continuous generation of methane for various applications including for use as a raw material, in power plants as a combustible fuel, in combustion engine for vehicle and power generation as well as in gas turbines.

Description

METHODS, SYSTEMS AND CATALYSTS FOR SUPERCRITICAL WATER REFORMING FEEDSTOCK INTO METHANE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit and priority to U.S. provisional patent application No. 61/424,400, filed December 17, 2010, and Canadian patent application No. 2,733,459, filed March 8, 2011, which are incorporated herein in its entirety as though set forth explicitly herein.

FIELD OF THE INVENTION

[0002] The present invention pertains to the methods, systems and catalysts for supercritical water reforming of feedstock, such as ethanol, into methane. More particularly, the present invention pertains to Ruthenium and Nickel catalysts useful in supercritical water reforming ethanol, processes for making such catalysts, and systems using the Ruthenium and Nickel catalysts for generating methane from feedstock, such as ethanol, using supercritical water.

BACKGROUND

[0003] Due to the limitation of light crude oil supplies and the increasing concern over greenhouse gas emission and climate change, there is worldwide interest in the use of ethanol as a renewable alternative fuel and in the production of electricity in conjunction with fuel cells. Ethanol has proved to be a better and cleaner transportation fuel, and it can be a promising substitute for methyl tert-butyl ether (MTBE) as an additive in gasoline fuels. Ethanol can be used directly as a gasoline substitute by simply blending at 5-15 vol% with gasoline, and at up to 85 vol% for flexible-fuel vehicles with modified engines.

[0004] Ethanol is currently produced on a commercial scale by traditional starch fermentation processes, but this process has been heavily criticized as it competes with food production in feedstock. There is rapidly growing interest in producing ethanol from non-food cellulosic materials such as agricultural residues, energy crops and wood wastes, through integrated bio-conversion processes involving enzymatic hydrolysis of cellulose to fermentable sugars followed by fermentation of sugar to ethanol, at a higher cost of approximately $1.5-2.0 per gallon. ^l'².

[0005] Ethanol as an alternative liquid fuel however suffers from several limitations due to its low energy density (23 MJ/L) and fuel efficiency (ethanol-fueled vehicles have only about 66% of efficiency compared with gasoline (energy density of 35 MJ/L) fuelled vehicles), high ethanol volatility and readiness to absorb water from the atmosphere. Furthermore, ethanol can only displace a fraction of light duty gasoline, while there is an increasing demand of renewable heavy duty/diesel substitutes to displace the diesel and jet fuels. In this regard, many research teams are exploring conversion technologies to transform ethanol and other alcoholic fuels into fuels with higher energy contents.

[0006] A significant fraction of the cost of producing ethanol as a fuel additive/substitute

(which requires complete removal of water) is associated with the costly operations of distillation and water separation from the azeotrope using zeolite adsorption. The economics of cellulosic ethanol can be significantly improved if crude ethanol (non-purified ethanol) can be used directly as a fuel. In this regard, catalytic steam/supercritical- water reforming of low-purity ethanol (such as 50%) into hydrogen has attracted a lot of interest, catalyzed by the development of fuel cell technologies. ^"

[0007] Stoichiometric steam reforming of ethanol into hydrogen may be presented by the following reaction:

CH₃CH₂OH (g) + 3 H₂0 (g)→ 2C0₂ (g) + 6H₂ (g) ΔΗ° = 172 kJ/mol (1)

This is a highly endothermic reaction, and is thermodynamically favourable at temperatures above 600°C. ' A variety of catalysts, mainly the oxides-supported Ni, Co and noble metals (Ir, Rh, Ru, Pt and Pd)^10"21, have been developed to enhance hydrogen productivity and selectivity. For example, >95% conversion of ethanol and ~100% hydrogen selectivity were obtained by reforming of ethanol over Rh/Ce0₂ catalyst at 800°C or over Ni/Zr0₂ at 650°C.²¹ However, severe catalyst deactivation due to coke deposition during ethanol reforming at high temperatures 1 0 1 1 1 ή 1 8 0

has been reported. ' ' ^~ ' ' The coke formation mainly results from polymerization of ethylene (a reaction intermediate in the reforming process) formed by dehydration reaction of ethanol, and catalyzed by acidic sites on the catalyst support.²⁴

[0008] Recently, supercritical water (SCW), highly compressed water at above its critical temperature of 374°C and critical pressure of 22 MPa, has been investigated for ethanol reforming. This is because SCW has the potential to reduce coking on the catalyst surface due to its increased solubility for non-polar organics (such as ethylene, a coke-precursor in ethanol reforming) and light inorganic gases. Arita et al.²⁵ investigated ethanol reforming in an autoclave reactor in SCW at 400-500°C without catalyst, producing a gas product rich in hydrogen, methane and C0₂, as well as acetaldehyde. Byrd et al.⁵² performed SCW-reforming of ethanol in a flow-type reactor at 700-800°C using a Ru/Al₂0₃ catalyst. A high hydrogen yield (up to 5.5 mol/mol-ethanol-fed) was obtained at 800°C and 22.1 MPa with a feed of 5 wt% ethanol-water solution, and no significant coke deposition over the catalyst was observed.

[0009] To address the problem of catalyst deactivation due to coking in the high- temperature steam reforming processes, low-temperature steam reforming of ethanol may be an

01

effective solution. Morgenstern and Fornango reported low-temperature reforming of ethanol over a novel Cu-Ni catalyst. The catalyst exhibited a high activity for low-temperature (250- 300°C) reforming of ethanol to methane, carbon monoxide, and hydrogen via the following reaction:

CH₃CH₂OH (g) + H₂0 (g)→ CFf₄ + C0₂ + 2H₂ ΔΗ° = 8.9 kJ/mol (2)

[0010] Although the low-temperature ethanol reforming pathway leads to formation of only 2 mol of hydrogen per mol of ethanol-fed versus 6 mol of hydrogen in the traditional high- temperature reforming processes (as per reaction 1), capturing the energy value of the methane produced by low-temperature reforming, combined with use of the waste heat to heat the reformer, could close the energy efficiency gap between the two pathways.²⁷ Low-temperature ethanol reforming processes may be particularly preferable for the proton exchange membrane (PEM) fuel cells currently constrained to operate at <200°C. [0011] Cellulosic ethanol can displace part of light duty gasoline fraction, however there is an increasing demand for renewable heavy duty/diesel substitutes to displace diesel and jet fuels. Moreover, the technology development for cellulosic ethanol has been facing a great challenge with respect to its high production cost, making it less competitive against the falling oil prices since July 2008. As a consequence, for instance, Global Energy Holdings (formerly Xethanol Corp) recently announced abandonment of its cellulosic ethanol business, and a shift to methane generation.²

[0012] Methane, as the major component of natural gas, is a clean fuel substitute for gasoline and diesel that can be used in internal combustion engines, as well as in power generation and in chemical plants as a raw material. Compressed natural gas (CNG) can be directly used in traditional gasoline internal combustion engine for vehicles and electricity generation. Natural gas vehicles have been used increasingly in Europe (Italy), South America (Argentina, Brazil) and Asia (Pakistan, India, China) due to high gasoline prices. Worldwide, there are more than 7 million natural gas fueled vehicles (NGVs) as of 2008, and the number of NGVs was projected by the International Association of Natural Gas Vehicles to climb to 65 million by 2020. In North America, the Canadian industry has developed CNG-fueled truck and bus engines. In the United States, CNG is available at 30-60% less than the cost of gasoline, and federal tax credits are available for buying a new CNG vehicle.

[0013] However, the CNG-fueled vehicles require a greater amount of space for fuel storage than the conventional gasoline powered vehicles, since CNG is a compressed gas, rather than a liquid like gasoline. To resolve this problem, there is a need for technology for on-board generation of methane from a liquid fuel (such as bio-ethanol). On-board generation of renewable methane from ethanol would be a promising technology towards the development of ethanol-fueled internal combustion engine vehicles, which could not only address the above space issue associated with CNG, but the issue of long-term fuel security.

[0014] In addition to IC engines, methane can be used as a fuel for electricity generation in a gas turbine or steam boiler. Compared to other hydrocarbon fuels, burning methane produces less C0₂ for each unit of heat released. Methane can be piped into homes for domestic heating and cooking purposes. Methane is also widely used in the chemical industry, through conversion into syngas - CO and H₂ by stream reforming using Ni-based catalysts at around 700-1100 °C: C¾ + 2 H₂0→ C0₂ + 4 H₂. An example of methane applications for chemical synthesis is the production of ammonia.

[0015] Ethanol can be effectively reformed into H₂ and CH₄ over a variety of catalysts, such as supported Ni, Co and noble metals (Ir, Rh, Ru, Pt and Pd) at a high temperature of over 650°C in steam⁵¹ or supercritical water (SCW)⁵². Ru and Ni are considered the best and the most commonly used catalysts for ethanol steam reforming towards hydrogen production. Ni, M et al. reviewed ethanol reforming using different catalysts with different supports. A study by Cai et al. ⁵⁴ showed that Rh/Ce0₂ catalyst exhibited stable activity and selectivity in converting ethanol to hydrogen during 70 h on-stream operation at 823-923 without obvious deactivation.

[0016] Liguras et al.⁵⁵ explored ethanol steam reforming with Rh, Ru, Pd, and Pt supported on A1₂0₃ at 873-1123K with metal loading of 0-5 wt%. Rh showed excellent catalytic performance in terms of ethanol conversion and hydrogen production. Although inactive at low loading, Ru showed comparable catalytic activity with Rh at a high loading. The Ru/Al₂0₃ with 5 wt% loading could completely convert ethanol into syngas with hydrogen selectivity above 95%. High dispersion of catalyst particles on the surface of a support material (such as A1₂0₃) was found to enhance the activity of catalysts. Acidic A1₂0₃ support induced ethanol dehydration to produce ethylene, which could be a source of coke formation on catalyst surface, a possible cause of catalyst deactivation.

[0017] A variety of non-noble metals were also investigated for ethanol and other alcohol gasification. Among them, Ni was found to be most effective. Second metal can have synergistic effect for alcohol gasification with Ni as the main catalyst. Youn et al.⁴⁹ investigated the effects of second metals (Ce, Co, Cu, Mg and Zn) in Νΐ/γ-Α1₂0₃ catalyzed auto-thermal reforming of ethanol with 0₂. Among the second metals tested, Cu was found to be the most efficient promoter for the Νΐ/γ-Α1₂0₃ catalyst for hydrogen production. It was revealed that Cu species are active in the water-gas shift reaction to produce hydrogen from CO and H₂0, and furthermore, Cu species can serve as a barrier for preventing the growth of Ni particles which can lead to catalyst aggregation and reactor plugging. In particular, the addition of Cu decreases the interaction between Ni-species and γ-Α1₂0₃, leading to the facile reduction of Ni-Cu/ γ-Α1₂0₃ catalyst. According to a study by Voll et al. , where Gibbs free energy minimization was used to calculate the equilibrium composition for supercritical water reforming of methanol, ethanol, glycerol, glucose and cellulose, it was found that higher temperatures, lower alcohol

concentrations, and lower pressure favour hydrogen formation, while lower temperatures, higher alcohol concentrations, and higher pressure favour methane formation.

[0018] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.

SUMMARY OF THE INVENTION

[0019] An object of the present invention is to provide methods, systems and catalysts for supercritical water reforming feedstock, such as ethanol, into methane.

[0020] In accordance with one aspect, there is provided a A process for reforming a hydrocarbon feedstock to produce methane comprising:

(a) mixing supercritical water and the hydrocarbon feedstock to form a liquid reactant

mixture;

(b) contacting the liquid reactant mixture with a catalyst;

(c) maintaining the mixture formed in step (a) in a supercritical state in a heated reactor; and

(d) recovering methane produced in step (b),

wherein the catalyst is a Ru-based catalyst in a reduced form, a Ru-based catalyst in an oxide form, a Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst and wherein the feedstock is methanol, ethanol, butanol, acetane or any combination thereof..

[0021] In accordance with one embodiment the catalyst comprises a solid support, such as alumina, zeolite, silica, titania, zirconia, activated carbon or another carbon material. In accordance with a specific embodiment, the feedstock is ethanol and the catalyst is a bi-metallic Ru-based and Ni-based catalyst on a γ-alumina support.

[0022] In accordance with another aspect there is provided a system for reforming a feedstock into methane comprising: (a) a water feed and a feedstock feed, wherein the feedstock is methanol, ethanol, butanol, acetane or any combination thereof; (b) a supercritical water (SCW) reactor in fluid communication with the water feed and the feedstock feed, wherein the SCW reactor contains a catalyst that is a Ru-based catalyst in a reduced form, a Ru-based catalyst in an oxide form, a Ni-based catalyst in a reduced form, or a combined Ru-based and Ni- based catalyst; and (c) a methane capturing device.

[0023] In one embodiment, the system is a continuous-flow system.

[0024] In accordance with another aspect, there is provided a A process for converting an organic feedstock to methane, comprising: reforming the organic feedstock using supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni- based catalyst, at a temperature in a range from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture comprising at least 34% methane; and capturing the gas mixture.

[0025] In accordance with another aspect, there is provided a process of fuelling a motorized vehicle having an ethanol-fuelled internal combustion engine, comprising: reforming ethanol using supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst, at a temperature from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture including at least 40% methane; and capturing the methane produced in the reactor and feeding said methane to the internal combustion engine

[0026] In accordance with another aspect, there is provided a process for conversion of ethanol to methane, comprising: reforming ethanol by contacting thet ethanol with supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni- based catalyst, at a temperature in a range from about 400°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce methane gas, carbon dioxide gas and water vapor according to reaction (1) CH₃CH₂OH + 3H₂0 - 1.5 C¾ + 0.5 C0₂ + 3H₂0 (1).

[0027] In accordance with another aspect, there is provided a process of converting ethanol to methane, comprising: reforming ethanol by contacting the ethanol with supercritical water in the presence of a catalyst comprising Fe, Co, Ni, Ru, Rh, Pd, Pt, or any combination thereof at a temperature from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture including at least 40% methane.

[0028] In accordance with another aspect, there is provided a bi-metallic catalyst comprising between about 5 - 25% Ni and between about 1 - 5% Ru supported on alumina, such as γ-alumina.

[0029] In accordance with another aspect, there is provided a method for producing a bimetallic Ni-Ru catalyst comprising:

(a) adding a solid support to an aqueous solution of a water soluble salt of Ni and an aqueous solution of a water soluble salt of Ru, wherein the solid support is thermally/chemically stable in supercritical water;

(b) mixing the suspension resulting from step (a);

(c) heating the mixed suspension from step (b) under reduced pressure to remove the water;

(d) drying the product of step d) in an oven; and

(e) calcining the solid product of step (d).

[0030] In accordance with another aspect, there is provided a method for producing a bimetallic Ni-Ru catalyst comprising:

(a) adding a solid support to an aqueous solution of one of a water soluble salt of Ni or an a water soluble salt of Ru , wherein the solid support is thermally/chemically stable in supercritical water;

(b) mixing the suspension resulting from step (a);

(c) heating the mixed suspension from step (b) under reduced pressure to remove the water;

(d) adding the solid support impregnated with Ni or Ru to an aqueous solution of the other of the water soluble salt of Ni or the a water soluble salt of Ru that was not already mixed with the solid support; (e) mixing the suspension resulting from step (d);

(f) heating the mixed suspension from step (f) under reduced pressure to remove the water;

(g) drying the product of step (f) in an oven; and

(h) calcining the solid product of step (g).

[0031] In accordance with another aspect, there is provided a use of a bi-metallic catalyst comprising about 5-25% Nickel and about 1-5% Ruthenium loaded on a solid support for reforming methanol, ethanol, butanol, acetane or a combination thereof into methane. In one embodiment, the feedstock is ethanol.

BRIEF DESCRIPTION OF THE FIGURES

[0032] For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0033] Figure 1 is a plot showing yields of gaseous products in reforming of ethanol in supercritical water (W/E molar ratio of 3.0) at 400°C for 60 min without and with various catalysts;

[0034] Figure 2 is a plot showing yields of gaseous products in reforming of ethanol in

SCW (W/E molar ratio of 3.0) at 400°C with Ru0₂ catalyst for various lengths of time;

[0035] Figures 3 A and 3B show the effects of reaction temperature on yields of gaseous products in reforming of ethanol in sub- and super-critical water (W/E molar ratio of 3.0) for 60 min without catalyst (3 A) and with Ru0₂ catalyst (3B);

[0036] Figure 4 is a plot showing the yields of gaseous products in reforming of ethanol in supercritical water (W/E molar ratio of 3.0) at 500°C for 60 min without and with Ru0₂ catalyst;

[0037] Figure 5 shows the effects of reaction temperature on the gaseous carbon yield in reforming of ethanol (W/E molar ratio of 3.0) for 60 min with and without Ru0₂ catalyst; [0038] Figures 6A and 6B show the effects of water-to-ethanol molar ratio on yields of gaseous products in reforming of ethanol in SCW at 500°C without catalyst (6A) and with Ru0₂ catalyst (6B) for 60 min;

[0039] Figure 7 shows an example of a schematic process flow diagram (PFD) of an onboard SCW reforming system for an internal combustion (IC) engine vehicle;

[0040] Figure 8 is a schematic process flow diagram (PFD) of the supercritical water reforming process;

[0041] Figures 9 A and 9B are plots showing the gas yields for ethanol reforming with 10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa (9 A) and with 5 wt% Ru/Al₂0₃ catalyst at 500°C and 25 MPa (9B);

[0042] Figures 10A and 10B are plots showing the gas yields for ethanol reforming with

10 wt% Ru/Al₂0₃ catalyst at 500°C and 25 MPa (10A) and with 1.72 wt% Ru-10 wt%Ni/Al₂0₃ catalyst at 500°C and 25 MPa (10B);

[0043] Figures 1 1 A and 1 IB are plots showing the gas yields for ethanol reforming with

3.44 wt% Ru-10 wt%Ni//Al₂0₃ catalyst at 500°C and 25 MPa (11A) and with 3.44 wt% Ru-20 wt%Ni//Al₂0₃ catalyst at 500°C and 25 MPa (1 IB);

[0044] Figure 12 is a plot showing the gas yield for ethanol reforming with the regenerated 1.72 wt% Ru- 10 wt%Ni//Al₂0₃ catalyst at 500°C and 25 MPa;

[0045] Figures 13A and 13B are plots showing the gas yields for methanol reforming with 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa: two replicate runs (A) and (B);

[0046] Figure 14A is a plot showing the gas yields for butanol reforming with 1.72 wt%

Ru-10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa and Figure 14B is a plot showing the gas yields for acetone reforming with 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa;

[0047] Figure 15 is a plot showing the gas yields for ABE reforming with 1.72 wt% Ru-

10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa; and [0048] Figure 16 is an BR spectrum of the original and spent catalysts of 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst after ethanol reforming at 500°C and 25 MPa.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Definitions

[0050] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0051] As used in the specification and claims, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0052] As used herein, the term "about", when used in conjunction with ranges of dimensions of particles, compositions of mixtures, ppm, space, velocity, concentrations, temperatures, pressures, times, or other physical properties or characteristics, is meant to cover slight variations that may exist in the upper and lower limits of the ranges of dimensions so as to not exclude embodiments where, on average, most of the dimensions are satisfied but where statistically dimensions may exist outside this range. It is not the intention to exclude

embodiments such as these from the present invention.

[0053] The term "comprising" as used herein will be understood to mean that the list following is non-exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s), step(s) and/or ingredient(s) as appropriate.

[0054] As used herein, the phrase "weight hourly space velocity (h^"1)", denoted as

"WHSV (h^"1)" or "WHSV", is calculated by dividing the hourly feeding rate (g/h) by the mass of the catalyst in the reactor (g). WHSV measures the residence time of the feed inside the reactor.

[0055] As used herein, the phrase "reforming" means rearranging the molecular structure of a hydrocarbon or a compound (e.g. ethanol as described herein) into other products with altered properties via reacting with H₂0 or hydrogen. Herein, an alcohol is reformed into CH₄ by supercritical water (a conversion reaction and a gasification).

[0056] As used in the art, the phrase "supercritical water" refers to water at a temperature above its critical temperature, where "critical temperature" is defined as the temperature above which a gas cannot be liquefied, the temperature above which a substance cannot exhibit distinct gas and liquid phases. The term "supercritical water" encompasses water that is at the critical temperature, above the critical temperature, and just below the critical temperature. The last of these is sometimes termed in the art "near-critical" water. That is, slight deviation below the precise critical temperature which does not substantially affect the reforming reaction is encompassed in the use of the term "supercritical water" with respect to aspects of this application. In the examples described hereinbelow, the phrase "supercritical water" refers to highly compressed water at above its critical temperature of 374°C and critical pressure of 22 MPa.

[0057] As used herein, the phrase "reaction time" means the residence time of reactants inside a reactor at the specific reaction temperature. Residence time is the inverse of the weight hourly space velocity (h^"1).

[0058] As used herein, the term "calcination" or "calcining" is used to refer to a thermal treatment process at an elevated temperature applied to solid materials, such as supported catalysts, to remove the volatile fraction via thermal decomposition and to obtain metal oxides.

[0059] To date, most research on alcohol reforming/gasification has been focused on hydrogen production. Described herein are catalysts, systems and processes of reforming ethanol and other feedstock into methane.

[0060] Catalyst

[0061] The present application provides a catalyst for supercritical water reforming of a feedstock to produce methane as the predominant product.

[0062] In the experimental work using a batch reactor, the inventors have demonstrated that neat Ru0₂ catalyst, without a solid support, was very active for converting ethanol to methane via supercritical water reforming. Furthermore, the alumina-supported Ru and Ni metals proved to be very effective for the reaction conducted with a continuous-flow tubular reactor. Without wishing to be bound by theory, in the supported metal catalysts described herein for ethanol reforming, the solid support was believed to provide a matrix to disperse the metal particles to allow a higher surface area and more accessibility of the active metal particles than was possible using the non-supported material.

[0063] Although the results provided herein were based on the use of alumina as a solid support, as would be well appreciated by a worker skilled in the art, other suitable catalyst support materials are those solid support materials having a high surface area and high thermal/reaction stability in supercritical water can be. Non-limiting examples of suitable catalyst support materials include: alumina, zeolite, silica, titania, zirconia, activated carbon and other carbon materials.

[0064] Similarly, although reduced Ni metal (10 wt% loading) promoted by Ru (1.72 wt% loading) as a co-catalyst or promoter was prove to be the most active catalyst among the catalysts tested, other catalysts prepared from groups 8-11 metals are expected to have activity for the supercritical water reforming process. For example, the transition metals (e.g., Fe, Ni, Co, etc.) and noble metals (e.g., Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au, etc.) can be used in catalysts for supercritical water reforming of feedstock, such as ethanol, to produce methane.

[0065] Specific, non-limiting, examples of catalysts useful in the reforming of ethanol into methane are Ruthenium and Nickel-based catalysts. While the present application focuses on the use of ruthenium catalysts in either oxide form or reduced form, the process can also be performed using other catalysts. Thus, the present application does not exclude reforming ethanol, or other feedstock, with supercritical water in the presence of a catalyst selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Pt, and any combination thereof at a temperature in a range from about 350°C to about 600°C and for a selected residence time, under which conditions the ethanol reacts with the supercritical water to produce methane, hydrogen, carbon dioxide, and wherein a resulting product gas mixture includes at least 40% methane.

[0066] The solid supported catalysts can be prepared by a wet impregnation method or co-impregnation for those containing more than one metal). This method involves the preparation of a solution of a water-soluble metal salt or salts, and combining the solutions with a support material. The mixture can then be shaken in an ultrasonic bath to assist metal salt dissolution and incorporation with the solid support. The mixture is heated to evaporation, which can occur under reduced pressure, to completely remove the water, and subsequently oven dried. Some examples of solid supports are alumina, silica, zeolite, activated carbon, or combinations thereof. One preferable support material for a wet impregnation method as presently described is γ-Α1₂0₃.

[0067] After the metal solution and solid support have been dried, the mixture is then calcinated at high temperature (for example, around 550°C). The catalyst is then prepared for use by crushing and sieving to obtain granules of acceptable size in the present application. Nominal diameters of the particulate catalyst range between 300-850 μπι.

[0068] Catalysts can be prepared with various compositions, various metals, and with different percentage metal loadings onto the solid support. Percentage loading can be varied by increasing the amount of metal salt in the metal salt solutions. Preferable total metal loading on the described catalysts is between about 1-30%, preferably 5-15% for the primary metal component and 1-5% for the secondary (co-catalyst or promoter). As well, the soluble metal salt used to prepare the catalyst can be varied, as well as the metal and/or combination of metals.

[0069] Process

[0070] The present application provides a catalytic process for reforming a feedstock to produce methane. For example, the feedstock can be an alcohol, including industrial grade alcohol feeds with impurities, such as methanol, butanol, ABE (acetone-butanol-ethanol), and others. Other organic feedstock such as methanol, acetone and butanol can be used in the process. To date, ethanol and methanol proved to be most desirable feedstock in terms of the conversion efficiency and the costs. Use of these feedstocks has been successfully demonstrated to generate methane, while maintaining an extended catalyst life.

[0071] In one embodiment of the present process, reforming ethanol into methane can be achieved with both a batch reactor and a tubular fixed-bed reactor. Reactions are generally carried out under high pressure (3000-6000 psi) and at high temperature (for example, between about 350°C to about 600°C). In a typical run a watery ethanol sample is fed to the reactor. This can also be accomplished by adding an amount of pure ethanol to distilled water, or by adding watery ethanol (industrial grade ethanol) with a known percentage ethanol. Preferably, the water-to-ethanol (W/E) molar ratio is between about 2-4, and preferably about 3.0 (equivalently 46 wt% ethanol in water).

[0072] In a batch reactor, the selected catalyst is added into the solution at a catalyst-to- ethanol molar ratio of 2%. In a continuous or flow-type reactor, the catalyst can be added to a catalyst bed support inside a reactor chamber at 25.2 h^"1 (WHSV - weight hourly space velocity) where WHSV was defined by the ratio of mass flow (g/h) of ethanol in the feed in relation of the amount of the catalyst (g) loaded in the reactor). The air inside the reactor is then displaced with nitrogen by repetitive vacuuming and N₂-purging.

[0073] In a batch reactor, the reactor is then pressurized with N₂ (in order to prevent boiling of the reaction medium during heating), and was heated to the specified reaction temperature (for example, in the range of 350 - 500^°C). The in situ reactor pressures can be in the range of 25-40 MPa, depending on the reaction conditions (such as temperature, reaction time, W/E ratio and type of catalyst). In a flow-type reactor, the catalyst was in-situ reduced by heating the reactor to 500°C with a constant H₂ (99.999%) flow at the rate of 30 mL/min for 2 h. After catalyst activation, the system was charged with nitrogen to 6.9 MPa (1000 psi). Ethanol (or other substrates) water solution (46/54, wt./wt. for ethanol) was pumped at 1.0 mL/min with an HPLC pump. The reactor was pressurized to 7 MPa (1000 psi) with nitrogen initially. The pressure of the reaction system was controlled at designated pressure in the range of 25-40 MPa.

[0074] It has been found that the following stoichiometric reaction can take place in

SCW at 500°C with W/E molar ratio of 3.0 in the presence of Ruthenium and Nickel catalysts, leading to complete conversion of ethanol into CH₄ and C0₂ at a yield of 1.5 mol/mol-ethanol- fed and 0.5 mol/mol-ethanol-fed, respectively.

CH₃CH₂OH + 3H₂0 - 1.5 CH₄ + 0.5 C0₂ + 3H₂0 ΔΗ° = -74 kJ/mol (3)

[0075] Reaction (3) is highly exothermic. Thus, the SCW-ethanol reforming process can be a self-sustaining auto-thermal process, compared with the highly endothermic process for high-temperature steam reforming of ethanol according to reaction (2). Therefore, the low- temperature SCW-ethanol reforming process is promising for on-board reforming of ethanol to methane for internal combustion engine vehicles. In addition, high diffusivity and solubility of SCW using catalysts as presently described can prohibit the formation of coke precursors (such as ethylene). In this regard, the present SCW-reforming process is advantageous over the conventional high-temperature steam reforming processes that suffer from severe problems of catalyst deactivation due to coke formation.^10,12'^16"18

[0076] Batch reactors for reforming of ethanol in sub-/supercritical water at 350-500°C with and without catalyst demonstrated that Ru and Ni-based catalysts were highly active for conversion of ethanol into CH₄ in supercritical water at >400°C. A complete conversion of ethanol was achieved in supercritical water at 500°C for 60 min with Ru catalysts, producing approximately 1.5 moles of methane and 0.5 mole of C0₂ per mole of ethanol- fed, according to the stoichiometric reaction (3) described above.

[0077] In one embodiment, the supercritical water reactor is a continuous-flow tubular fixed-bed reactor. The continuous-flow reactor can be preferable as it is more practical and economical for the proposed applications of the technology in IC engines for vehicles and power generation.

[0078] Alumina-supported Ni, Ru and Ru-Ni catalysts are effective at reforming ethanol in supercritical water in a continuous plug-flow reactor at 500°C. These catalysts (particularly in the reduced form) show high activities for reforming of ethanol into methane, leading to approximately 1.3 mol-methane/mol-ethanol plus 0.1-0.2 mol H₂/mol-ethanol and ~100% carbon gasification efficiency. Although ethylene and acetaldehyde have been considered as important intermediates in the H₂ formation from steam reforming of ethanol,^17"20 in the present work ethylene was detected in the gas products at an extremely low amount (<0.01 mol/mol-ethanol), and acetaldehyde was not detected in any of the gas products.

[0079] Application

[0080] In terms of volume energy density, methane (889KJ/mol) has a much higher energy density than hydrogen (286KJ/mol). Methane products of reforming of alcohol and bio- waste can be, for example, burned directly in internal combustion engines for vehicles, used as fuel in power generation, or used as chemical starting materials. Methane is also a common feedstock used in industrial processes.

[0081 ] Natural gas can be used as a source of electricity generation through the use of gas turbines and steam turbines. Some power plants and generators can be run on natural gas. Natural gas burns more cleanly than other hydrocarbon fuels and produces less carbon dioxide per unit of energy released. Further, with a fuel of pure methane as provided by the methane generation systems described, the resulting emissions will be relatively free of contaminants and toxic biproducts.

[0082] To gain a better understanding of the invention described herein, the following example is set forth. It should be understood that these examples are for illustrative purposes only. Therefore, they should not limit the scope of this invention in any way.

EXAMPLES

[0083] EXAMPLE 1 : Preparation of Ruthenium and Nickel Catalysts

[0084] The catalysts were prepared by a wet impregnation method (or co-impregnation for those containing more than one metal) using water-soluble metal salts including, for example, nickel (II) nitrate hexahydrate (Ni(N0₃)₂.6H₂0) and ruthenium (III) nitrosyl nitrate solution in dilute nitric acid (HN₄O₁₀Ru), all supplied by Sigma-Aldrich. The support material used was γ- A1₂0₃. All the metal impregnated catalysts was first oven-dried at 105°C for 12 h and then calcined for 6.5 h at 550°C in air, followed by crushing and sieving to obtain granules with nominal diameters ranging between 300-850 μηι.

[0085] The catalysts were prepared by incipient wetness impregnation on γ-Α1₂0₃ with different loading of metal compounds of Ni and Ru, targeting at different net metal contents (wt./wt.) (as shown in Table 1 in Example 2). A typical procedure is described in brief as follows. A pre-weighed amount of the metal nitrate compound was first dissolved in distilled water or mixed with pre-weighed amount of Ru solution, and a pre-weighed amount alumina was added. The mixture was shaken for 3h in an ultrasonic bath. The resulting suspension was subject to evaporation under reduced pressure at 80°C to completely remove the water. The impregnated mass was dried 2 h at 120°C in an oven, and finally calcinated at 550°C in a muffle furnace for 5 h.

[0086] EXAMPLE 2: Catalytic Reforming of Ethanol

[0087] The ethanol used in the tests was anhydrous ethyl alcohol from Commercial

Alcohol Ltd (>99.5% purity). The catalysts used in this work were A.C.S. reagent-grade ruthenium (IV) oxide, potassium carbonate ( ₂C0₃), calcium hydroxide (Ca(OH)₂), and sulphate heptahydrate (FeS0₄ ^* 7H₂0), all supplied from Sigma- Aldrich. In addition, some y-Al₂0₃- supported ruthenium-based and nickel-based catalysts were also prepared by incipient wetness impregnation with a 10 wt% loading.

[0088] The process was investigated with both a batch reactor and a tubular fixed-bed reactor. The batch studies were carried out in a 75 mL Parr high pressure reactor (Pan- Instrument, N4740), made of Hastelloy alloy, with maximum working pressure of 6000 psi at 600°C. In a typical run, 8.520 g of the ethanol sample was weighed into the reactor, followed by adding a precisely controlled amount of distilled water, corresponding to the water-to-ethanol (W/E) molar ratio of 3.0 if not otherwise specified. Various W/E molar ratios from 3.0 to 10.0 were also investigated in the study. The selected catalyst (i.e., Ca(OH)₂, K₂C0₃, FeS0₄, or Ru0₂) was added into the solution at a catalyst-to-ethanol molar ratio of 2%. The air inside the reactor was displaced with high purity nitrogen by repetitive vacuuming and N₂-purging.

[0089] The reactor was then pressurized with N₂ to 2.0 MPa (in order to prevent boiling of the reaction medium during heating), and was heated at 10°C/min up to the specified reaction temperature (in the range of 350 - 500°C). The in situ reactor pressures, self-generated by temperature and formation of gaseous products, were recorded during operation and were in the range of 25-40 MPa, depending on the reaction conditions (such as temperature, reaction time, W/E ratio and type of catalyst). [0090] After the desired reaction temperature was reached, the reactor was maintained at that temperature for 30-120 min before being cooled rapidly to room temperature. Once the reactor was cooled to room temperature, the gas inside was released through a condenser (in a cold bath of salt-water solution at < -10°C) into a gas-collecting vessel. The liquid products and solid residue (from some catalysts such as Ru0₂) inside the reactor and the condenser were rinsed completely with distilled water and acetone. After filtration through a pre-weighed Whatman No. 5 filter paper, the solid residue and catalyst (for Ru0₂) was separated and dried at 105°C for 4 h in an oven.

[0091] The gaseous products were analyzed using an Agilent 3000 Micro-GC equipped with dual columns (Molecular Sieve and PLOT-Q) and thermal conductivity detectors. The gas chromatograph (GC) system employed in this work enabled analysis of gas species up to C₃, including 0₂, N₂, H₂, CO, C0₂, CH₄, C₂H₄, C₂H₆, C₃¾, C₃H₆, while gas species of higher molecular weights (C₄) were not detectable by the GC used. Most of the experimental runs were repeated 2-3 times, and the maximum relative difference in the gas yields between the runs under the same conditions fell within a reasonable range of +5% of the average yields.

[0092] In addition to the above batch tests, the performance of four catalysts, all supported on γ-Α1₂0₃, were further investigated for supercritical water gasification of ethanol in a tubular fixed-bed reactor (Inconel 625 tubing, 9.55 mm OD, 6.34 mm ID, 472 mm length). Two of the catalysts were ruthenium-based (Ru-R and Ru-C), and two were nickel-based (Ni-R and Ni-C), where "R" and "C" represent "reduced" and "calcinated", respectively. The catalysts were prepared by incipient wetness impregnation with a 10 wt% loading as described in Example 1.

[0093] Each catalyst was tested under identical conditions of temperature (500°C), pressure (3600 psi), and weight hourly space velocity (25.2 h^"1). The feed concentration was fixed at 46 wt% ethanol in distilled water, which corresponds to a 1 :3 molar ratio of ethanol to water. The results are presented in Table 1. Table 1

Catalyst¹ Reaction CH₄ yield C0₂ yield H₂ yield Reactor

Temperature/time (mol/mol (mol/mol (mol/mol configuration ethanol)² ethanol) ethanol)²

K₂C0₃ 0.005 0.024 0.167

Ca(OH)₂ <0.001 0.001 0.023

FeS0₄ 400°C/60min <0.001 <0.001 0.005 Batch reactor Ru0₂ 1.19 0.439 0.113

RuC-2 500°C/60min 1.43 0.516 0.144

Ru/Al₂0₃-C 500°C 1.33 0.51 0.14

Ru/Al₂0₃-C 1.30 0.49 0.14 Fixed bed flow-type Ni/Al₂0₃-R 1.30 0.55 0.16

reactor, Ni/Al₂0₃-C 0.00 0.00 0.02

¹ The results are average values from steady state data approximately in the first 2.5 h on-stream.

² Yield of gas, defined by moles of the gaseous species per mole of ethanol fed.

[0094] The results in Table 1 show that Ru-R, Ru-C, and Ni-R catalysts are all suitable catalysts for methane production by supercritical water gasification of ethanol in a continuous flow reactor, producing approximately 1.3 mol CH₄, 0.15 mol H₂ and 0.5 mol C0₂ from each mol of ethanol fed into the reactor. The yields of methane, carbon dioxide, and hydrogen obtained from the continuous process are close to the stoichiometric yields as predicted from equation (3), i.e., 1.5 mol C¾ and 0.5 mol C0₂ per mole of ethanol.

[0095] Figure 1 shows a comparison of yields of gaseous products in reforming of ethanol in supercritical water with a W/E molar ratio of 3.0 at 400°C for 60 min without and with various catalysts. Yields of all individual gaseous species are also presented in the Table within Figure 1. Without catalyst at this temperature, ethanol reforming in SCW was very inefficient, generating negligibly small yields (mol/mol-ethanol-fed) of all gaseous products, e.g., 0.003 for ¾, O.001 for all the other gases (C¾, CO, C0₂, C₂ and C₃).

[0096] The catalytic effects of all the catalysts (i.e., Ca(OH)₂, K₂C0₃, FeS0₄, and Ru0₂) were evident, in particular with K₂C0₃ and Ru0₂. The H₂ yield with K₂C0₃ attained 0.167 mol/mol-ethanol, roughly 56 times that from the operation without catalyst. The use of Ru0₂ significantly increased H₂ yield too, as observed previously in steam reforming of ethanol, but it was extraordinary effective for the formation of CH₄ and C0₂. Reforming of 1 mol of ethanol in SCW at 400°C with Ru0₂ catalyst produced 1.19 mole CH₄ and 0.439 mole C0₂, more than 1190 times and 439 times those from the operation without catalyst.

[0097] Effect of Reaction Time

[0098] Effect of reaction time was investigated by reacting ethanol in SCW water (with

W/E molar ratio of 3) at 400°C for various lengths of time (from 30 min to 120 min) with Ru0₂ catalyst. Figure 2 shows variations of product yields with reaction time. There were negligible increases in the yields of H₂, CO, C0₂ and C₂+C₃ gases as the reaction time increased from 30 to 120 min. However, there was a rapid increase in methane formation between 30 and 60 minutes, but the methane yield levelled off after 60 min. This levelling off suggests that the reforming reactions at 400°C tend to attain equilibrium in about 60 min.

[0099] Effect of Temperature

[00100] Figure 3 shows the gaseous product yields from reforming of ethanol in sub- /super-critical water at a temperature from 350°C to 500°C for 60 min with and without Ru0₂ catalyst, where the W/E molar ratio was fixed at 3.0. Without catalyst, a very small amount of gas was formed at a low temperature < 420°C, and the yields of H₂, CH₄ and CO all climbed gradually with increasing temperatures, in particularly from 420°C to 500°C, as shown in Figure 3 A. As observed from Figure 3B, in the presence of Ru0₂ the yields of H₂, CO and C0₂ did not increase significantly as the temperature increased from 350°C to 500°C, which is consistent with the literature results with commercial supported Ru catalysts. ^" For instance, steam reforming of ethanol with Ru/Al₂0₃ did not lead to a significant increase in hydrogen yield as the reaction temperature increased to 500°C, and a high yield of hydrogen could be only obtained at

70 1

temperatures above 700°C.

[00101] In contrast, in the present example, the yield of CH₄ climbed rapidly as temperature increased from 350°C to 500°C, although it appeared to level off at >400°C. The yield of C¾ attained as high as 1.43 mol/mol-ethanol-fed in SCW reforming of ethanol at 500°C with Ru0₂, accompanied by a C0₂ yield of 0.52 mol/mol-ethanol-fed. The extraordinary performance of the Ru0₂ in reforming ethanol into methane can be clearly seen in Figure 4, where the yields of the major gaseous species are plotted in comparison with those from the operations without catalyst.

[00102] Effect of Catalysts on Reaction Time

[00103] In the process of reforming of ethanol for the generation of methane in sub- /super-critical water at 350-500°C without catalyst, very small yields (all < 0.1 mol/mol-ethanol) of the major gaseous products of CH₄, H₂, CO, C0₂, and C₂ and C₃ were obtained even at 500°C. Alkaline catalysts such as K₂C0₃ and Ca(OH)₂ catalyzed H₂ formation, however they were less active for methane generation.

[00104] Ru-based catalysts (in either a reduced or oxide form) and reduced Ni-based catalyst were found to be highly active for conversion of ethanol into CH₄ in supercritical water at >400°C, and optimal reaction conditions were found to be at 500°C, 60 min with a water-to- ethanol molar ratio of 3.0. A complete conversion of ethanol was achieved under these conditions with Ru0₂ in a batch process, producing approximately 1.5 moles of methane and 0.5 mole of C0₂ per mole of ethanol-fed, suggesting stoichiometric decomposition of ethanol into methane in accordance with equation (3) above.

[00105] Effect of Water-to-Ethanol Molar Ratio

The effects of water-to-ethanol (W/E) molar ratio on the SCW-ethanol reforming reaction were studied by varying the W/E molar ratio from 1.0 to 10.0 with and without Ru0₂ catalyst at 500°C for 60 min, where the yields of the major gaseous species are presented vs. W/E in Figures 6A and 6B. Without catalyst, varying the W/E molar ratio from 1.0 to 10.0 led to a negligible change in the yields of all gaseous species, as shown in Figure 6A. With Ru0₂, however, the yields of gaseous products varied greatly with the W/E molar ratio. As the W/E molar ratio increased from 1.0 to 3.0, the CH₄ yield increased from approximately 1.0 to 1.43 mol/mol-ethanol-fed, accompanied by a slight increase in C0₂ yield and a negligible change in H₂ and CO. These results suggest that a higher conversion of ethanol could be expected by increasing the amount of water in the system in accordance to the reaction (3) due to equilibrium shift. [00106] The yield of CH₄ declined as the W/E ratio further increased from 3.0 to 10.0, accompanied by a rapid increase in H₂ yield. Similar observations were reported in many previous studies on ethanol steam/SCW reforming with various supported metal catalysts including Ru/Al₂0₃ where the formation of H₂ was enhanced by increasing the steam-to-ethanol

26 31 33

ratio. ' ^" The enhanced hydrogen-formation by increasing the concentration of water in the reaction medium may be explained by the equilibrium shift of the steam methane reforming reaction and water-gas-shift reaction.

[00107] EXAMPLE 3: Evaluating Ethanol Conversion Efficiency

[00108] To evaluate the ethanol conversion efficiency, the gaseous carbon yield (mol/mol- ethanol-fed) was defined as the moles of C in the gaseous products in relation to moles of ethanol fed to the reactor. For the steam/SCW reforming of ethanol, the gaseous carbon yield can represent the conversion efficiency of ethanol into gaseous products. For example, the theoretical gaseous carbon yield would be 2.0 mol/mol-ethanol-fed for the complete conversion of C₂H₅OH.

[00109] Figure 5 provides gaseous carbon yields at various temperatures with and without Ru0₂ catalyst. Without catalyst, the carbon yield remained almost zero until 400°C, and it attained only approximately 0.36 mol/mol-ethanol-fed at 500°C, implying that about 18% of ethanol was converted into gaseous products. In the presence of Ru0₂ catalyst, a high gaseous carbon yield was achieved, even at 350°C, where the carbon yield reached 1.48 mol/mol-ethanol- fed, suggesting an ethanol conversion of 74% at this temperature. At 500°C with Ru0₂, the gaseous carbon yield attained approximately 2.0 mol/mol-ethanol-fed, suggesting complete gasification of ethanol. In contrast, in steam reforming of ethanol in the presence of commercial Ru/Al₂0₃, a very low ethanol conversion (<5%) was reported at 500°C, and a complete conversion of ethanol in steam reforming was only obtained at temperatures > 700°C.^29,30

[00110] EXAMPLE 4: System for Fuelling Vehicles with Renewable Methane

[00111] Typical internal combustion (IC) engines have an efficiency of about 20%, depending on the road conditions, air-to-fuel ratio in combustion, and the compression ratio. The efficiency could be improved to, for example, 35% in some hybrid gasoline-electric vehicles. [00112] Compressed natural gas (CNG) is a fossil fuel substitute for gasoline and diesel. Although the combustion of CNG does produce greenhouse gases, it is a more environmentally clean alternative to those fuels. Specifically, CNG-powered engines produce significantly lesser emissions of pollutants like C0₂, HCs, CO, NO_x, SO_x and particulate matter (PM), as compared to the gasoline engines. For example, an engine running on petrol for lOOkms emits 22kg C0₂, whereas covering the same distance on CNG emits only 16.3 kg C0₂. CNG may also be mixed with renewable methane (biogas, produced from landfills or wastewater), which does not increase the concentration of carbon in the atmosphere.

[00113] CNG is made by compressing natural gas (methane), to less than 1 % of its volume at standard atmospheric pressure. It is normally distributed in hard cylindrical containers, at a normal pressure of 20-25 MPa. CNG can be used in traditional gasoline internal combustion engine cars, which can also be converted into bi-fuel vehicles (e.g., gasoline/CNG). Two main advantages of vehicles fueled by CNG include: (1) the lead/soot fouling of spark plugs is substantially eliminated due to the absence of any lead or benzene content in CNG; and (2) CNG-powered vehicles have lower maintenance costs when compared with other fuel-powered vehicles. However, a major drawback of a CNG powered vehicle is that they require a greater amount of space for fuel storage than conventional gasoline power vehicles.

[00114] Using the process and catalyst as described, the economics of cellulosic ethanol can be significantly improved if crude ethanol (non-purified ethanol) is used directly as a transportation fuel. This provides an alternative to bio-diesel and bio-ethanol.

[00115] A schematic process flow diagram (PFD) of an on-board supercritical water (SCW) reforming system for an internal combustion (IC) engine vehicle is shown generally at 10 in Figure 7. SCW system 10 includes an ethanol feed container 12 connected to a high pressure pump 16, and a water feed container 14 which is connected to a high pressure pump 30. Pumps 16 and 30 pump the ethanol and water respectively through a valve 40 wherein the mixture of highly pressurized ethanol and water are pumped into a preheater 22. After the mixture is preheated it is pumped into a reactor 20 which in turn is heated by an electric heater 32.

[00116] In operation, ethanol solution is pumped with a high pressure pump 16 from the ethanol fed container 12. The ethanol stream is mixed with a water stream pumped with another high pressure pump 30 from water feed container 14. The mixture is pumped into a preheater 22 and then fed into a reactor 20 operating at 500°C and 24.5 MPa. The products flow through the pre-heater 22 to recover some heat, and a cooling unit 24. The cooled product stream is de- pressurized via a back-pressure controller 34, and separates into two streams: water and gaseous products in a gas-liquid separator 26. The water, collected in a water collection vessel 28, is then recycled via a discharge valve 38 and a pump 18 to the water feed container 14. The produced gas (with theoretical composition of 75 vol CH₄ and 25 vol% C0₂) will be sent to the IC engine.

[001 17] As the reaction can attain 100% conversion, the mass balance of the reforming system is shown simply on the PFD. A part of the water in the product stream will be recycled (8.4 kg/h) to the stream-2 of the reactor feed.

[001 18] EXAMPLE 5: Preparation of Bi-metallic Ruthenium/Nickel catalysts

[001 19] The raw materials and chemicals used include: anhydrous ethanol (99.9%), methanol (99.9%), Ni(N0₃)₂.6¾0, Ru(NO)(N0₃)_x(OH)_y solution with 1.5% ruthenium, alumina. All of these were ACS reagent-grade chemicals from Sigma- Aldrich and were used as received without further treatment.

[00120] The bi-metallic catalysts were prepared by incipient wetness impregnation on γ- A1₂0₃ with different loading of metal compounds of Ni and Ru, targeting at different net metal contents (wt./wt.) (as shown in Table 2, below). A typical procedure is described in Example 1 , and in brief as follows.

[00121] A pre-weighed amount of the metal nitrate compound was first dissolved in distilled water or mixed with pre-weighed amount of a Ru solution, and pre-weighed amount alumina was added. The mixture was shaken for 3h in an ultrasonic bath. The resulting suspension was subjected to evaporation under reduced pressure at 80°C to completely remove the water. The impregnated mass was dried 2 h at 120°C in an oven, and finally calcinated at 550°C in a muffle furnace for 5 h. [00122] EXAMPLE 6: SCW reforming tests on Mono and Bi-metallic Catalysts

[00123] A continuous reaction process and an active bi-metallic catalyst (RuNi/Al₂0₃) with improved catalyst stability (life time) over the mono-metallic catalysts has been developed for supercritical water reforming of alcohols (ethanol and methanol) into methane. Optimal conditions were achieved in the present example at 500°C, 25 MPa, and 25.2 h^"1 (WHSV) with 46 wt% substrate-water solution.

[00124] A diagram of the supercritical water reforming reactor system used in the present study is shown in Figure 8. This is a continuous reactor including a feedstock reservoir 40 connected to a high pressure pump 42. Pump 42 pumps the organic feedstock through a valve 44 and a pressure relief valve 46 into a tubular reactor 50, which is heated by an electric heater 52. The effluent is cooled by a water cooling jacket 48, passes through a filter 54 and is collected in a high-pressure liquid-gas separator 56 whose pressure is controlled by a back pressure regulator 58.

[00125] An Inconel 625™ tube (3/8-in OD, ¼-in ID, and 18.6-in long) with cooling jackets 48 on both ends was used as the tubular reactor 50. In a typical run, a metal disc 60 supported with a metal rod, on which certain amount of quartz wool was packed, was used to hold the catalyst bed 62. In order to preheat the feed and achieve a more homogeneous flow inside the catalyst bed, silica sand as the bed materials were packed in the following sequence: 1 g of sand, 1.00 g of the above calcinated catalyst mixed with 2.00 g sand, 1 g sand, and certain amount of quartz wool on the top. Tubular reactor 50 was completely sealed and tested for leak proof with pressurized nitrogen.

[00126] The catalyst was in-situ reduced by heating the reactor to 500°C with a constant H₂ (99.999%) flow supplied from a hydrogen cylinder 41 at the rate of 30 mL/min controlled by a mass low controller 43 for 2 h . After catalyst activation, the system was charged with nitrogen supplied from a N₂ cylinder 38 to 6.9 MPa (1000 psi). Ethanol (or other substrates) water solution (46/54, wt./wt. for ethanol) was pumped from the feedstock reservoir 3 at 1.0 mL/min with an Eldex™ 2SM-1/8 pump 42. The reactor was pressurized to 7 MPa (1000 psi) with nitrogen initially. The pressure of the reaction system was controlled between 24.8 MPa (3600 psi) to 26.2 MPa (3800 psi) with backpressure regulator 58. [00127] The reaction mixture was cooled by the cooling jacket 48 at the reactor exit and then the water-cooled gas-liquid separator 56. Gas and liquid were separated at the gas-liquid separator. The gas was collected at different time intervals with a pre-evacuated gas cylinder 59 equipped with a pressure gauge and was analyzed with Agilent 3000 Micro-GC equipped with dual columns (Molecular Sieve and PLOT-Q) and a thermal conductivity detector (TCD). A standard calibration file was generated by using a refinery standard gas sample (containing H₂, 0₂, N₂, CO, C0₂, CH₄, C₂H₂, C₂¾, C₂H₆, C₃H₆). The liquid product was collected at the bottom of the gas-liquid separator. Following the same procedures, methanol, butanol, acetone, and a simulated ABE (the mixture of 5 wt.% acetone, 5 wt.% butanol, and 90 wt.% ethanol) were also tested with a same substrate concentration (46 wt.% in water). Table 2 shows the steady-state gas yields (moles of gas per mole of ethanol fed) with different catalyst compositions at different temperatures and pressures.

Table 2 - Reforming of ethanol at various conditions

Reactor was plugged after 4 h on-stream

[00128] Table 2 shows the steady-state gas yields (moles of gas per mole of ethanol fed) with different catalyst compositions at different temperatures and pressure. The gas yields in Table 2 are the yields when the pressure of the reactor reached the set-point pressure (e.g., 25 MPa for most runs). It usually took 1-1.5 hours to reach the desired pressure. The gas yields were calculated by dividing the moles of gas produced per minute in average by the moles of ethanol fed to the reactor per minute. As per the equilibrium equation (3), the complete conversion of ethanol will theoretically yield 1.5 mol methane, 0.5 mol carbon dioxide.

[00129] As shown from Table 1, in most runs at 500°C and 25 MPa, the complete conversion of ethanol was obtained, producing theoretical yields of CH₄ and C0₂ plus relatively small amounts of H₂ and C₂H₆ as well as trace amount of C₂HU. The total carbon balances (the total yield of CH , C0₂ and C₂¾ were at 2-2.3 mol-C/mol C₂H₅OH fed) were close to or slightly higher than 100% (owing to the unavoidable experimental errors in the experiments and gas analyses), in accordance with reaction (3), copied below:

C₂H₅OH + 3 H₂0→ 1.5 CH₄ + 0.5 C0₂ + 3 H₂0 (3)

[00130] It took about 1 hour for the reactor to reach the pressure set-point (in most runs, 25 MPa), so there was no gas sample collected before lh on-stream. The liquid phase (mainly water) collected from the bottom of the gas-liquid separator was most clear without smelling of any odour.

[00131] Effect of Catalyst Composition

[00132] In Table 2, from runs 1 and 2, it is evident that when Ni metal at a loading of 10 wt.% and 20 wt.% on A1₂0₃ was used as the catalyst, the gas yields were very high, close to the theoretical yields expressed in equation (3). As shown in Figure 9 A, all gas yields remain stable before 4 h on-stream, when significant decreases in all yields were observed, suggesting deactivation of the catalysts. Namely, the 10 wt.%Ni/Al₂0₃ and 20 wt.%Ni/Al₂0₃ catalysts have a life time of about 4 h. A higher content of Ni (20%) did not increase either the gas yields or catalyst life time.

[00133] Runs 3 and 4 in Table 2 give the results of 5 wt% and 10 wt% Ru catalyst supported on A1₂0₃. The gas compositions during the course of the tests are shown in Figures 9B and 10A. The gas yields were all very low and the reactor pressure could only reach about 10 MPa. The liquid effluent was light yellowish color with apparent alcohol odour, indicating incomplete conversion of ethanol. The activities of the catalysts decreased after approx. 3h on- stream (see Figures 9B, 10A), suggesting deactivation of the catalysts, which might be due to coke deposition resulted from polymerization of ethylene (a reaction intermediate in the reforming process) formed by dehydration reaction of ethanol, catalyzed by acidic sites on the catalyst support^{47, 48}.

[00134] When combining Ni and Ru, a strong synergistic effect emerged. Run 5 in Table 2 and Figure 10B show the results of 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst (RuNi//Al₂0₃). Ethanol conversion was complete and the gas yields for CH₄, C0₂, H₂, and C₂H₆ were at the similarly high levels as those of 10% Ni/Al₂0₃ catalyst. Further, the lifetime of the Ru-Ni bimetallic catalyst is observed to be about 9 h, more than double of the lifetime of the Ni monometallic catalyst. Comparing with Runs 1-4, one may speculate that the main active metal for ethanol reforming is Ni. Addition of Ru in Ni catalyst may further significantly increase the catalyst lifetime.

[00135] If Ru content is increased to 3.44% (Run 6 in Table 2 and Figure 11 A), almost similar gas yields were produced, but the catalyst lifetime decreased from 9h to 6h. When the Ni metal content was further increased to 20% Ni with 3.44% Ru (Run 7 in Table 1 and Figure 6), the reactor was plugged after 4 h on-stream likely due to the coke/tar formation. As reported in the literature⁴⁹, a similar synergistic effect was found between Cu and Ni in auto-thermal reforming of ethanol over Νί/γ-Α1₂0₃ catalysts for hydrogen production. Cu was found to be the most efficient promoter for the Ni/γ- A1₂0₃ catalyst for hydrogen production. It was revealed that Cu species are active in the water-gas shift reaction to produce hydrogen from CO and H₂0, and furthermore, Cu species can serve as a barrier for preventing the growth of Ni particles which can lead to catalyst aggregation and reactor plugging. In particular, the addition of Cu decreases the interaction between Ni-species and γ-Α1₂0₃, leading to the facile reduction of Ni-Cu/ γ-Α1₂0₃ catalyst. The synergistic effect of Ru and Ni may result from a similar mechanism as described above.

[00136] Effects of Pressure, Temperature and Alcohol Concentration

[00137] Comparing the results of Runs 5 and 8 in Table 1, it is observed that the reaction pressure had significant influence on the gas composition. With the 1.72 wt% Ru-10

wt%Ni//Al₂0₃ catalyst at 500°C, reducing reactor pressure from 25 MPa to 14 MPa decreased the CH₄ yield from 1.6 to 1.1 mol/mol, while it increased the ¾ yield markedly from 0.2 to 0.9 mol/mol. One may thus conclude that higher pressure favours the formation of methane, while low pressure promotes hydrogen production.

[00138] The ethanol reforming tests were performed at two reaction temperatures, i.e., 500°C and 400°C with the 1.72 wt% Ru-10 wt%Ni/Al₂0₃ catalyst (Runs 5 and 9 in Table 1). It was found that at 400°C, the methane concentration in gas product was high, but the overall gas yield was low suggesting lower ethanol conversion. As such, a higher temperature favours the ethanol reforming, resulting in a higher total gas yield but reduced methane selectivity. The results as reported in this work were obtained at ethanol-water ratio of 46/54 (w/w) which is corresponding to 1/3 mole ratio of ethanol/water.

[00139] The effect of pressure, temperature, and feed composition may be explained by thermodynamic equilibrium calculations, as reported previously by Voll et al.⁵⁰, where it was found that higher temperatures, lower alcohol concentrations, and lower pressure

thermodynamically favour hydrogen formation, while lower temperatures, higher alcohol concentrations, and higher pressure favour methane formation.

[00140] EXAMPLE 7: Non-ethanol feedstocks

[00141] The Ru and Ni-based catalysts as described were found to be useful for the production of renewable methane from non-ethanol feedstocks. Specifically, other alcohols can be utilized, as well as industrial grade alcohol feeds with impurities such as methanol, acetone, butanol, ABE (acetone-butanol-ethanol), and others, while maintaining an extended catalyst life.

[00142] Methanol Reforming

[00143] Two replicate tests were conducted for methanol reforming at 25 MPa using a feed of 46 wt% methanol in water at a feed rate of 1 mL/min. The gas yields from the two replicate tests are displayed in Figures 13 (A) and (B). Except the two data points at 7 and 8h (Figure 13 A), caused by a sudden discharge of the backpressure regulator, in average the gas product has composition of CH₄: C0₂: H₂ = 3: 1 : 0. 5 (v/v/v), suggesting the following reforming reaction: 4 CH₃OH + H₂0→ 3CH₄ + C0₂ + ½ H₂ + 2¾0 (4)

[00144] Reforming methanol in SCW at similar conditions with the RuNi/Al₂0₃ catalyst produced 100% conversion of methanol and theoretical yield of methane (0.75 mole mol of methanol fed). The catalyst was stably active after 10-12 h on-stream in methanol without any indication of deactivation.

[00145] Butanol Reforming

[00146] Figure 14A shows the gas yields for butanol reforming with 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa. The overall gas compositions are CH₄: C0₂: H₂ = 2: 1 : 0.5. Besides methane, carbon dioxide and hydrogen, considerable amount of ethylene was detected. The yield of CEU was less than 0.6 mol/mol. Compared with ethanol and methanol, the C0₂ concentration in the product gas was also relatively higher. The total carbon conversion to gases was calculated to be only about 22%. Reforming a higher alcohol (e.g., butanol) is thus successful but more difficult than lower alcohols such as methanol and ethanol.

[00147] Acetone Reforming

[00148] Figure 14B shows the gas yields for acetone reforming with 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst at 500°C and 25 MPa. Similar to butanol reforming, the overall gas compositions are CH₄: C0₂: H₂ = 2: 2: 1. Considerable amount of ethylene were formed. The yield of CH₄ was lower than 0.3 mol/mol.

[00149] Compared with ethanol and methanol as well as butanol, the C0₂ concentration in the product gas was much higher. The overall carbon conversion was less than 20%, that it is more difficult to gasify/reform acetone than alcohols. One reason for this may be because the carbonyl group in acetone is more stable than the hydroxyl group in alcohols.

[00150] ABE Reforming

[00151] Figure 15 presents the test result of reforming the simulated acetone-butanol- ethanol ("ABE") ethanol containing 5 wt% butanol and 5 wt% acetone. The overall gas compositions are C¾: CO?: H₂ = 3: 1 : 0.1. Comparing the gas yields of ABE with those of reforming the individual feed components, the gas yields results from reforming of the mixture of ethanol, butanol and acetone as shown in Figure 11 can be predicted by the addition effects. For instance, the CH₄ yield in reforming ABE was approximately 1.3 mol/mol, lower than that of ethanol (1.5-1.6 mol/mol) but high than that of butanol (0.5-0.6 mol/mol) or acetone (0.2-0.3 mol/mol). Compared with that of ethanol and methanol as well as butanol, the C0₂ concentration in the product gas was much higher, which is due to the decomposition of acetone. The overall carbon conversion was high but slightly lower than 100%, suggesting SCW reforming of ABE into methane is viable.

[00152] EXAMPLE 8: Mechanism of Alcohol Reforming in Supercritical Water

[00153] For gasification of biomass with SCW at high temperature of (well above the critical temperature of water of 374 °C) and a relatively low pressure of 25-30 MPa (but still above the critical pressure 22.1 MPa), free-radical mechanisms may dominant in the system ⁵⁶

[00154] The following free radical mechanism for ethanol and methanol reforming in SCW are proposed:

C₂H₅OH -→~ ^eCH₃ +^*CH₂OH

CH₂OH + H₂0 ► CH₃OH +^*OH

C₂H₅OH—^► CH₃CHO + H₂

CH₃CHO ► CH₄ + CO

C₂H₅OH—^► CH₄ + CO + H₂

CO + H₂ CH₂0

CO + H₂0 ► C0₂ + H₂

CH₂0 + H₂ CH₃OH

C₂H₅OH -→^■ CH₂=CH₂ + H₂0

CH₂=CH₂ + H₂ —► C₂H₆

CH₂=CH₂ ^► (CH₂CH₂ ) _n

CH₂=CH₂ ► C₂H₂ + H₂ [00155] For the methanol SCW reforming, the flowing radical reactions are proposed.

CH₃OH *^{*" e}CH₃ + OH

^*CH₃ + H₂0 ► CH₄ + OH

CH₃OH »^► CO + 2H₂

CO + H₂0 ► C0₂ + H₂

"OH + H₂ ^► H₂0 + Ff

CH₃ + H *- CH₄

CH₃ + H₂ *- CH₄ + Η·

'OH +^*0H ► H₂0 + l/₂ 0₂

[00156] EXAMPLE 9: Catalyst Deactivation and Regeneration

[00157] As shown in Table 2 and Figures 9A-12, all the metal catalysts suffered from deactivation after 3-9 hours on-stream. Without wishing to be bound by theory, possible reasons for the catalyst deactivation could be (1) carbon deposition on the catalyst surface, (2) the oxidation of Ni by water (Ni + H₂0→ H₂ + NiO), and (3) sintering/aggregation of the catalyst. Carbon deposition may be due to the acidity property of A1₂0₃ support which dehydrates ethanol to form ethylene [14, 15]. This is also probably why catalyst deactivation was not observed in the methanol reforming after 9-10 h reaction (Figure 8).

[00158] Carbon deposition may be demonstrated by TGA analysis (in 30 niL/min air, heated at 50°C/min from room temperature to 800°C). It was found that there was about 2% weight loss between 500 and 800°C in the spent 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst after ethanol reforming at 500°C and 25 MPa. Carbon deposition was also evidenced by FTIR in the spent catalysts, as shown in Figure 16. In Figure 16, the top curve is the IR spectrum of the fresh 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst, and the lower curve is the spent catalyst after the 500°C ethanol reforming test. On the lower IR curve for the spent catalyst, the absorbance around 1100cm^"1 is C-H bond, suggesting carbon deposition may play an important role in catalyst deactivation process. [00159] In-situ generated fine Ni particles are very reactive. It may be reasonably hypothesized that the fresh surface of the Ni after in-situ reduction may be quickly oxidized once exposed in water during the reaction. Nevertheless, CH₄ and H₂ can be continuously generated during the course of the reforming process.

[00160] The oxidation of metal particles during the reaction can be prevented or retarded. To probe the above three mechanisms, catalyst regeneration and an ethanol reforming test using regenerated catalyst was performed. The regeneration process was conducted in-situ by heating the spent catalyst with a 100 mL/min air at 600°C for 2 h, followed by 550°C hydrogen reduction for 2 h. As shown in Table 2 and Figure 12, the regenerated catalyst regained activity and had a lifetime of 8 h on-stream. The regeneration likely resulted in burn off the carbon deposit to free the Ni surface.

[00161] The results of the above regeneration-reforming tests suggest that that carbon deposition may be the main cause of the catalyst deactivation. The catalyst regeneration results also suggest that the third deactivation mechanism, i.e.sintering/aggregation of the metal particles, is not significant at the process conditions where the reaction temperature was relatively low (less than 500°C) using the 1.72 wt% Ru-10 wt% Ni/Al₂0₃ catalyst. The sintering/aggregation mechanism is, however, more likely for a Ni catalyst with a higher metal loading (20 wt.%). For example, with the 3.44 wt% Ru-20 wt%Ni /A1₂0₃ catalyst (Run 7 in Table 2 and Figure 1 IB), reactor plugging occurred after 4 h on-stream, which was caused by sintering/aggregation of Ni particles. It was also found that long-time catalyst regeneration also caused reactor plugging.

[00162] The spent catalyst could be regenerated in-situ with air followed by hydrogen reduction at >500°C to regain its activity. The regenerability for the RuNi/Al₂0₃ catalyst not only demonstrates its promise in application, but also suggests that carbon deposition may be the main cause of the catalyst deactivation. [00163] EXAMPLE 10: Considerations for SCW reforming of Ethanol for Methane generation for IC Engines - Mass and Energy Balance Analysis

[00164] Mass and energy balance analysis, costs and reduction in greenhouse gases for an exemplary system for fueling vehicles with renewable methane produced on-board by supercritical water reforming of ethanol are given in Table 3. The performance comparison is shown between the IC engine vehicles powered by gasoline, natural gas (methane), and renewable CH₄ from ethanol, (calculation basis: 100 km travelling distance on a highway at a speed of 100 km/h for 1 h)

Table 3

Fuel Electricity Energy Greenhouse Cost Greenhouse consumption consumption cost³ gas emission^b saving⁰ gas

(kg) (kwh) ($) (kg) (%) reduction⁰

(%)

Gasoline 6 0 7.8 18.5 - -

Natural gas 4.6 0 4.1 12.7 47 31

(Methane)

Renewable 10.8 0.69 5.5 8.7 29 53

CH₄ from

170 proof

ethanol (82

wt%)

a Including the costs of fuel and electricity;

b Non-renewable C0₂ emission;

⁰ Calculated based on energy cost of the gasoline-powered vehicle;

d Calculated based on greenhouse gas emission from the gasoline-powered vehicle.

[00165] Compared with an IC engine vehicle powered by gasoline, an IC engine vehicle fueled with renewable methane produced on-board by catalytic supercritical water reforming of bio-ethanol (crude 170 proof corn ethanol) may have superior performance in both fuel economics and environmental effects, leading to approximately 30% cost saving and >50% greenhouse gas reduction.

[00166] Mass and heat balances are estimated below with the following assumptions. In the calculations, the selected scenarios are that IC engine vehicles powered by different fuels (gasoline, CNG, and renewable methane produced on-board by supercritical water reforming of bio-ethanol using the method disclosed herein) are travelling on a highway at a speed of 100 km/h. Further assumptions and procedures used in the calculations are given as follows:

1. The heating value of gasoline is on average 43 MJ/kg.

2. The heating value of methane (CH₄) is on average 56 MJ/kg.

3. The fuel consumption for a gasoline-fueled vehicle is 8L/100km, with an average gasoline density of 0.75kg/L, the fuel consumption for a gasoline-fueled vehicle is 6kg/100km.

4. The fuel consumption for a natural gas (CEL^-fueled vehicle is 8.4m³/ 100km, with an average methane density of 0.55kg/m³at 1 atm and 21°C. The fuel consumption for a methane- fueled vehicle is 4.6kg/100km.

5. Gasoline (Cs-Cg) contains 84 wt% C, at a price of 1 $/liter = $ 1.3/kg; The greenhouse C0₂ emission is 3.08 kg-C0₂/kg-fuel.

6. C¾ contains 75 wt% C, at a residential price of $0.49/m³ = $0.89/kg; The greenhouse C0₂ emission is 2.75 kg-C0₂/kg-fuel.

(http://www.hydro.mb.ca/regulatory_affairs/energy_rates/natural_gas/current_rates.shtml)

7. It is assumed that reaction (3) (supercritical water reforming of ethanol into methane) achieves 100% conversion with the proposed catalyst in a supercritical water reformer (SCW reformer) at 500°C and 25 MPa, generating a CH₄-rich gas product (75 vol% C¾ + 25 vol% C0₂) that can be fed into the IC engine directly without further treatment.

8. It is assumed that an engine fueled by methane (75 vol% CH₄ + 25 vol% C0₂) from SCW reforming of ethanol has the same efficiency as that fueled by pure methane.

9. The ethanol consumption of the SCW reformer is thus calculated at 8.8 kg/100km, the density of ethanol is 800 kg/m³.

10. If using 170 proof (or 85 vol% or 82 wt%) industrial ethanol as the ethanol source feed, the 170 proof ethanol consumption is approximately 10.8 kg/ 100km. 11. The greenhouse gas emission from the fuel-carbon in a renewable fuel (e.g., renewable methane from bio-ethanol) is zero as renewable fuels are regarded as "carbon neutral"; however, there is a certain amount of greenhouse gas emission released in the corn-ethanol production life cycle (crop planting, harvesting, transportation and ethanol production itself). It is estimated that the C02 emission from the bio-ethanol, associated with the life-cycle of the corn-ethanol production in a Conventional Dry Mill Ethanol Plant, is 43% of that of gasoline on the basis of the same energy output. (Cheminfo Services Inc., Ethanol Production in Alberta. Final Report, April 2000, prepared for Interdepartmental Ethanol Committee, Government of Alberta).

12. The price of the 170 proof industrial ethanol is assumed to be 2$/gallon or ~0.5$/kg

(http://www.agmrc.org/renewable_energy/ethanol/the_relationship_of_ethanol_gaso- line_and_oil_prices . cfm)

[00167] From equation (3), the stoichiometric water-to-ethanol molar ratio is 3: 1, i.e., the overall reactor feed is a 46 wt% ethanol water solution. To obtain the overall reactor feed of a 46 wt% ethanol water solution , the following two feeding streams are designed:

Stream- 1 : 10.8 kg/100km 82 vol% ethanol, and

Stream-2 : 8.4 kg/ 100km pure water

[00168] It should be noted that the above two streams are examples to demonstrate the process only. In practice, stream- 1 could include industrial grade alcohols (with impurities) and ABE (acetone, butanol and ethanol) from industrial fermentation processes and butanol.

Depending on stream- 1, the flow rate of stream-2 will be adjusted accordingly to obtain a 46 wt% alcohol solution.

[00169] From equation (3), the SCW reforming of ethanol to methane is exothermic (ΔΗ° = -74 kJ/mol). Accordingly, in theory, the reaction could be energy self-sufficient, i.e., no additional energy would be needed for the reaction. In an exemplary practical engineering design of the SCW reformer system, preheating of the reactor feed occurs via a heat exchanger to recover the sensible heat of the hot product stream, as indicated in the above PFD. Nevertheless, in a real process with energy loss and limited heat exchanger efficiency, a small amount of electric energy may still be needed to preheat the reactant streams and start the reactor system. [00170] As shown in the heat exchanger of Figure 7, the product stream (500°C) will preheat the feed stream from 21 °C/0.1 MPa to 480°C/25 MPa, and the electric heater 32 will heat the mixture of ethanol-water (46 wt% ethanol-H₂0) further from 480°C/25 MPa to

500°C/25 MPa under supercritical conditions of both water and ethanol. The average heat capacity of liquid water (C_V,H₂O): 4.2 kJ/K kg. The average heat capacity of supercritical water (sc-H₂0) at 500°C and 25 MPa (C_v,_sc-H2o): 2.5 kJ/K/kg (Marcus, 2000). The average heat capacity of liquid ethanol (C_v,Et-oH): 2.4 kJ/K/kg. The average heat capacity of supercritical ethanol (sc-Et-OH) at 500°C and 25 MJ (C_v,_sc-Et-OH): ~4.0 kJ/K/kg (Polikhronidi et al. 2007). For convenience, it is assumed that the electric heater has 100% efficiency (i.e., is well insulated). = m_Et__OHC ,Et-OH (500 - 480) + m_H20C_PtH20 (500 - 480)

(5)

Where q is the required power for the electric heater; rh_El__0H and m_H20 are the mass flow rate of ethanol and water, respectively; C _Et__0H and C_{p H20} are the constant-pressure heat capacity for ethanol and water, respectively, herewith approximating the average C_p values using the average values. kg Ih kJ

q = 8.8 (500 - 480 )

h 3600 s kgK

f kg Ih kJ_

+ 10 .4 2.5 (500 - 480 )

V h 3600 kgK

In addition to preheating the reactor feed, electric power will also be required by the two high- pressure pumps 16 and 30, pumping/compressing 10.8 kg/h 85 vol% (or 82 wt%) ethanol-water and 8.4 kg/h H₂0 from 0.1 MPa to 25 MPa. Assuming an efficiency of η = 80% for both pumps, the total shaft pump power is calculated as follows.

P_s = qi ΔΡ/ (3.6^χ10⁶)/η + q2 ΔΡ/ (3.6^χ10⁶)/η (5) where

P_s = Total pump shaft power (kW) qi =Volumetric flow rate of stream- 1 (10.8 kg/h 85 vol% ethanol- water)

₌ (10.8 x 0.82)te //, ₊ (₁Q.8 x 0.18fe //, _{= 0 01 1 + 0 001 9 = 0 0 1 29m} 3 _/ ,

S00kg/m³ 1000kg /m³

(8 )ks/h

q₂=Volumetric flow rate of stream-2 (8.4 kg/h water) = ^{' } s}— - = 0.0084m³ Ih .

lOOOkg/m

ΔΡ = (25-0.1) = 24.9MPa = 24.9 l0⁶Pa. η = pump efficiency = 0.8

Substitute the above into Eq. (5),

P_s = (0.0129 m³/h) x24.9 l0⁶Pa / (3.6xl0⁶)/0.8+ (0.0084 m³/h) x24.9 l0⁶Pa / (3.6xl0⁶)/0.8 = 0.18 kW

Therefore, for this example using the above assumptions, the total electric power requirement is (0.51+0.18) = 0.69 kW.

[00171] Regarding the economics/environmental effects of the electricity consumption, two more assumptions are made as follows:

13. It is assumed that the residential electricity price is 8 cent/kWh

(ht1p://www.energyshop.com/es/prices/ON/eleON.cfm?ldc_id=291&).

14. It is assumed the electricity is produced from lignite coal (18 MJ/kg and 60 wt% C on a dry basis) with 40% efficiency. The C02 emission per 1 kwh (3.6 MJ) is thus estimated at 1.1 kg- C02/kwh.

[00172] All publications, patents and patent applications mentioned in this Specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference to the same extent as if each individual publication, patent, or patent applications was specifically and individually indicated to be incorporated by reference. [00173] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for reforming a hydrocarbon feedstock to produce methane comprising:

(a) mixing supercritical water and the hydrocarbon feedstock to form a liquid reactant mixture;

(b) contacting the liquid reactant mixture with a catalyst;

(c) maintaining the mixture formed in step (a) in a supercritical state in a heated reactor; and

(d) recovering methane produced in step (b),

(e) wherein the catalyst is a Ru-based catalyst in a reduced form, a Ru-based catalyst in an oxide form, a Ni-based catalyst in a reduced form, or a combined Ru-based and Ni- based catalyst and wherein the feedstock is methanol, ethanol, butanol, acetane or any combination thereof.

2. The process of claim 1, wherein the catalyst comprises a solid support, such as alumina, zeolite, silica, titania, zirconia, activated carbon or another carbon material.

3. The process of claim 1 or 2, wherein the reaction mixture in the reactor is maintained at a temperature in a range of from about 350°C to about 600°C.

4. The process of claim 3, wherein the reaction mixture in the reactor is maintained at a temperature of about 500°C.

5. The process of any one of claims 1 - 4, wherein the reforming of the hydrocarbon feedstock produces a product mixture comprising at least about 34% methane or at least about 60% methane.

6. The process of claim 5, wherein step (d) comprises separating the methane from the product mixture.

7. The process of any one of claims 1 - 6, wherein the hydrocarbon feedstock is ethanol.

8. The process of any one of claims 1 - 7, wherein the ratio of supercritical water to hydrocarbon feedstock is from about 1 : 1 to about 5: 1 , or about 2: 1 to about 4: 1.

9. The process of claim 8, wherein the ratio of supercritical water to ethanol is about 3: 1.

10. The process of any one of claims 1 - 9, which is a batch process or a continuous process.

1 1. The process of any one of claims 1 - 10, wherein the molar ratio of catalyst-to-feedstock is in a range from about 0.5 % to about 20 % or the catalyst-to-ethanol molar ratio is about 2%.

12. The process according to any one of claims 1 - 11, wherein the process is a continuous- flow process and the weight hourly space velocity is in a range from about 1 h^"1 to about 500 h^"1 or is about 25.2 h^"1.

13. The process of claim 2, wherein the catalyst comprises the support material with a metal loading from about 5 to about 30 wt% or at a metal loading of about 10 wt%.

14. The process according to claim 13, wherein the support material is alumina, such as γ- alumina, silica, zeolite, activated carbon, or a combination thereof.

15. The process according to any one of claims 1 - 14, wherein the catalyst is a combined Ru-based and Ni-based catalyst.

16. The process according to any one of claims 1 - 15, wherein the pressure in the heated reactor is from about 22 MPa to about 50 MPa.

17. A system for reforming a feedstock into methane comprising:

(a) a water feed and a feedstock feed, wherein the feedstock is methanol, ethanol, butanol, acetane or any combination thereof;

(b) a supercritical water (SCW) reactor in fluid communication with the water feed and the feedstock feed, wherein the SCW reactor contains a catalyst that is a Ru-based catalyst in a reduced form, a Ru-based catalyst in an oxide form, a Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst; and a methane capturing device.

18. The system of claim 17, wherein the methane capturing device is within an internal combustion engine, a storage system, or a power generating system.

19. The system of claim 17 or 18, wherein the catalyst comprises a solid support, such as alumina, zeolite, silica, titania, zirconia, activated carbon or another carbon material.

20. The system of any one of claims 17 - 19, wherein the reactor is maintained at an internal temperature in a range of from about 350°C to about 600°C.

21. The system of claim 20, wherein the internal temperature of the SCW reactor is about 500°C.

22. The system of any one of claims 17 - 21, wherein the system produces a product mixture comprising at least about 34% methane or at least about 60% methane.

23. The system of claim 22, wherein the methane capturing device comprises a separator for separating methane from the product mixture.

24. The system of any one of claims 17 - 23, wherein the feedstock comprises ethanol.

25. The system of any one of claims 17 - 24, wherein the ratio of supercritical water to hydrocarbon feedstock in the SCW reactor is from about 1 : 1 to about 5: 1.

26. The system of claim 25, wherein the ratio of supercritical water to ethanol is about 3:1.

27. The system of any one of claims 17 - 22, which is a continuous system or a batch system.

28. The system of any one of claims 17 - 27, wherein the molar ratio of catalyst-to-feedstock is in a range from about 0.5 % to about 20 % or the catalyst-to-ethanol molar ratio is about 2%.

29. The system according to any one of claims 17 - 27, wherein the weight hourly space velocity in the system is in a range from about 1 h^"1 to about 500 If¹ or is about 25.2 h^"1.

30. The system according to claim 19, wherein the catalyst comprises the support material with a metal loading from about 5 to about 30 wt% or at a metal loading of about 10 wt%.

31. The system according to claim 30, wherein the support material is alumina, such as γ- alumina, silica, zeolite, activated carbon, or a combination thereof.

32. The system according to any one of claims 17 - 31, wherein the catalyst is a combined Ru-based and Ni-based catalyst.

33. The system of any one of claims 17 - 32, wherein the pressure in the SCW reactor is from about 22 MPa to about 50 MPa.

34. The system of any one of claims 17 - 33, wherein one or both of the water feed and the feedstock feed comprise a preheater.

35. A process for converting an organic feedstock to methane, comprising:

(a) reforming the organic feedstock using supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst, at a temperature in a range from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture comprising at least 34% methane; and

(b) capturing the gas mixture.

36. The process of claim 35, wherein the organic feedstock is ethanol, acetone, methanol, butanol or a combination thereof.

37. The process of claim 36, wherein the organic feedstock is ethanol.

38. The process of any one of claims 35 - 38, wherein the catalyst is a combined Ru-based and Ni-based catalyst or a combined Ru-based and Ni-based catalyst on a γ-alumina support.

39. The process of claim 38, wherein the catalyst comprises between about 5 - 25% Ni by weight and between about 1 - 5% Ru by weight.

40. A process of fuelling a motorized vehicle having an ethanol-fuelled internal combustion engine, comprising: (a) reforming ethanol using supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst, at a temperature from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture including at least 40% methane; and

(b) capturing the methane produced in the reactor and feeding said methane to the internal combustion engine.

41. A process for conversion of ethanol to methane, comprising: reforming ethanol by contacting thet ethanol with supercritical water in the presence of a catalyst that is a Ru-based catalyst in a reduced form, Ru-based catalyst in an oxide form, Ni-based catalyst in a reduced form, or a combined Ru-based and Ni-based catalyst, at a temperature in a range from about 400°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce methane gas, carbon dioxide gas and water vapor according to reaction (1)

CH₃CH₂OH + 3H₂0→ 1.5 CH₄ + 0.5 C0₂ + 3H₂0 (1).

42. The process according to claim 41 wherein a catalyst-to-ethanol molar ratio is about 2%.

43. The process according to claim 41 wherein the ethanol and the supercritical water are contained in a heated reactor further containing the catalyst, and wherein a pressure in the heated reactor is in a range from about 22 MPa to about 50 MPa.

44. A process of converting ethanol to methane, comprising: reforming ethanol by contacting the ethanol with supercritical water in the presence of a catalyst comprising Fe, Co, Ni, Ru, Rh, Pd, Pt, or any combination thereof at a temperature from about 350°C to about 600°C and for a selected reaction time so that the ethanol and the supercritical water react to produce a gas mixture including at least 40% methane.

45. A bi-metallic catalyst comprising between about 5 - 25% Ni and between about 1 - 5% Ru supported on alumina, such as γ-alumina.

46. The catalyst of claim 45 comprising about 10% Ni and about 1.7% Ru.

47. The catalyst of claim 45 or 46, which is calcinated.

48. A method for producing a bi-metallic Ni-Ru catalyst comprising:

(a) adding a solid support to an aqueous solution of a water soluble salt of Ni and an aqueous solution of a water soluble salt of Ru, wherein the solid support is thermally/chemically stable in supercritical water;

(b) mixing the suspension resulting from step (a);

(c) heating the mixed suspension from step (b) under reduced pressure to remove the water;

(d) drying the product of step d) in an oven; and

(e) calcining the solid product of step (d).

49. The method of claim 48, wherein in step (a), the aqueous solution of a water soluble salt of Ni and the aqueous solution of a water soluble salt of Ru are mixed prior to addition of the solid support.

50. A method for producing a bi-metallic Ni-Ru catalyst comprising:

(a) adding a solid support to an aqueous solution of one of a water soluble salt of Ni or an a water soluble salt of Ru , wherein the solid support is thermally/chemically stable in supercritical water;

(b) mixing the suspension resulting from step (a);

(c) heating the mixed suspension from step (b) under reduced pressure to remove the water; (d) adding the solid support impregnated with Ni or Ru to an aqueous solution of the other of the water soluble salt of Ni or the a water soluble salt of Ru that was not already mixed with the solid support;

(e) mixing the suspension resulting from step (d);

(f) heating the mixed suspension from step (f) under reduced pressure to remove the water;

(g) drying the product of step (f) in an oven; and

(h) calcining the solid product of step (g).

51. The method of any one of claims 48 - 50, wherein the solid support is alumina, zeolite, silica, titania, zirconia, activated carbon or another carbon material.

52. The method of claim 51, wherein the solid support is γ-alumina.

53. The method of any one of claims 48 - 51, wherein the bi-metallic catalyst comprises between about 5-25% Ni and between about 1-5% Ru on a solid support.

54. The method of claim 53, wherein the bi-metallic catalyst comprises about 1.72% Ru and 10% Ni.

55. Use of a bi-metallic catalyst comprising about 5-25% Nickel and about 1-5% Ruthenium loaded on a solid support for reforming methanol, ethanol, butanol, acetane or a combination thereof into methane.

56. The use according to claim 55 wherein the catalyst comprises about 1.72% Ru and 10% Ni.

57. The use according to claim 55 or 56, wherein the catalyst is produced according to the method of any one of claims 48 - 56.

58. The use according to any one of claims 55 - 57, wherein the feedstock is ethanol.