CN1711212A - Use of metal supported copper catalysts for reforming alcohols - Google Patents

Abstract

This invention is directed to a process for reforming an alcohol. The process comprises contacting an alcohol with a reforming catalyst comprising copper at the surface of a metal supporting structure, preferably a metal sponge supporting structure comprising nickel. In a certain preferred embodiment, hydrogen produced by the reforming process is used as a fuel source for a hydrogen fuel cell to generate electric power, particularly for driving a vehicle.

Description

Use of metal-supported copper catalysts for reforming alcohols

Technical Field

The present invention relates generally to the dehydrogenation or reforming of alcohols. More particularly, the present invention relates to a process for dehydrogenating a primary alcohol, such as methanol or ethanol, to produce hydrogen, particularly for fuel cells for the production of electrical energy. The dehydrogenation process uses a copper-containing catalyst comprising a metal support structure.

Background

It is well known that contacting primary alcohols with a suitable catalyst at elevated temperatures (e.g., above 200 ℃) results in the decomposition of the alcohol, producing hydrogen gas and carbonaceous material. This process is commonly referred to as "alcohol reforming". For example, as shown in equation 1 below, methanol reforming produces hydrogen and carbon monoxide:

(1)

the hydrogen formed in the reforming process may then be provided to a fuel cell to produce electrical power. The reforming process is endothermic and requires sufficient heat transfer to the catalyst, especially in transportation applications (e.g., electric vehicles) that require high peak power, especially at start-up. Methanol reforming has been described, for example, by Gunter et al, J.Catal.203, 133-49 (2001); breen et al, j.chem.soc.chem.comm., 2247-48 (1999); european Chemical News, page 22 (11/5/1998); and Jiang et al, appl. Cat.97A, 145-58 (1993). Methanol reforming and specific applications of methanol reforming as a hydrogen source for fuel cells have been described, for example, by Agrell et al, Catalysis-specialty chemical Reports, vol 16, pp 67-132 (edited by j.j. spivy, Royal Society of Chemistry, Cambridge, UK, 2002).

It is important to note that carbon monoxide is generally toxic to the electrodes of fuel cells. For example, when the carbon monoxide content of the hydrogen feed exceeds 20ppm, the performance and power savings of the fuel cell typically decrease. See, Pettersson et al, Int' l J. hydrogen Energy, Vol.26, p.246 (2001). It is therefore desirable to convert carbon monoxide to carbon dioxide by reacting with steam according to equation 2 below:

(2)

this shift is known as the water gas shift reaction and has been widely practiced commercially. Descriptions of catalysts, processes and applications for the water gas shift reaction can be found, for example, in Catalyst Handbook, p 283-339 (2 nd edition, edited by m.v. twigg, Manson press, london, 1996).

Under conditions similar to those described above with respect to methanol, ethanol reforming first produces acetaldehyde, which can then be decomposed (i.e., decarbonylated) to carbon monoxide and methanol as shown in equation 3 below:

(3)

like methanol reforming, ethanol reforming is preferably combined with the water-gas shift reaction to convert carbon monoxide to carbon dioxide and produce additional hydrogen. For example, the water-gas shift reaction combined with ethanol reforming produces carbon dioxide, methane, and hydrogen as shown in equation 4 below:

(4)

the most common catalysts for alcohol dehydrogenation and low temperature water gas shift reactions comprise copper with zinc oxide, sometimes with other promoters, on a refractory support structure, typically alumina or silica. Copper-zinc oxide catalysts, while exhibiting excellent stability to methanol synthesis, have been reported to have insufficient stability to methanol reforming as described by Cheng, appl.cat.a, 130, pages 13-30 (1995), and Amphlett et al, stud.surf.sci.calt., 139, pages 205-12 (2001).

Many other catalysts that are reported to be active for the reforming of alcohols consist of metal oxides, typically containing a catalytic metal. Yee et al J.Catal.186, 279-95(1999) and Sheng et al J.Catal.208, 393-403(2002) reported in CeO₂CeO by itself or with rhodium, platinum or palladium₂In the above-mentioned secondReforming alcohol. However, these articles indicate that ethanol can be decomposed into a variety of undesirable by-products, such as acetone, ketene, and butylene.

Copper-nickel catalysts are known to have high activity for the dehydrogenation of ethanol. For example, copper-nickel catalysts supported on alumina are active for ethanol reforming. The reforming of ethanol over a copper-nickel catalyst has been described by Marino et al in stud.surf.sci.catal.130c, 2147-52(2000) and Freni et al in fact.kinet.catal.lett.71, 143-52 (2000). Although these references indicate that the catalyst provides good selectivity for the dehydrogenation of acetaldehyde, each reference suffers from incomplete conversion and minimal water gas shift activity at 300 ℃. In addition, conventional ethanol reforming catalysts tend to deactivate rapidly due to carbon deposition on the surface (a process known as coking). At temperatures above 400 ℃, coking is accelerated by the presence of acid sites on the catalyst surface, which promotes dehydration of ethanol to form ethylene which is then polymerized. Coking problems involving ethanol reforming catalysts have been described, for example, in Haga et al, Nippon Kagaku Kaishi, 33-6(1997) and Freni et al, React.Kinet.Catal.Lett., 71, pp 143-52 (2000).

Thus, there remains a need for improved alcohol dehydrogenation catalysts and processes capable of performing alcohol reforming at moderate reaction temperatures with adequate conversion.

Summary of The Invention

It is therefore a particular object of the present invention to provide a novel and improved process for the dehydrogenation of alcohols to form hydrogen, in particular a process using a catalyst having a higher density than prior art alcohol reforming catalysts; an improved process for using a reforming catalyst that provides better thermal conductivity to support endothermic reactions; an improved process using a catalyst without acid sites; an improved process using a catalyst having high activity and increased stability for the conversion of acetaldehyde to methane and carbon monoxide at moderate temperatures; an improved method of producing a hydrogen-containing product mixture suitable for use in a fuel cell for the production of electrical energy; and a novel and practical method of generating electrical energy from ethanol at reforming temperatures below about 400 ℃, which enables a simplified power system requiring less expensive hydrogen fuel cell units and improved energy efficiency.

Briefly, therefore, the present invention is directed to a process for reforming an alcohol. The process comprises contacting an alcohol with a reforming catalyst comprising copper at the surface of a metal supporting structure. In a preferred embodiment, the reforming catalyst comprises copper at the surface of the metal sponge supporting structure, wherein a metal sponge comprising nickel or a metal sponge comprising nickel and copper is preferred.

The invention further relates to a process for reforming ethanol. The process includes contacting a feed gas mixture comprising ethanol with a reforming catalyst at a temperature of less than about 400 ℃ to produce a reformate mixture comprising hydrogen. The reforming catalyst comprises copper at the surface of a metal support structure. In a preferred embodiment, the process comprises contacting a feed gas mixture comprising ethanol with a catalyst comprising copper on the surface of a nickel support at a temperature of less than about 350 ℃.

The invention further relates to a method of generating electrical energy from a fuel cell. The process includes contacting a feed gas mixture comprising ethanol with a dehydrogenation catalyst in a dehydrogenation reaction zone to produce a product mixture comprising hydrogen. The dehydrogenation catalyst comprises copper at the surface of a metal support structure. Introducing hydrogen and oxygen from the product mixture into a fuel cell to produce electrical energy and a fuel cell effluent comprising methane. The fuel cell effluent is introduced into a combustion chamber and combusted in the presence of oxygen.

In other embodiments, the present invention relates to an improved copper plating process for preparing a dehydrogenation catalyst.

Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.

Brief description of the drawings

FIG. 1 is a schematic diagram of a power system in which a hydrogen-containing product mixture produced in alcohol reforming is introduced as fuel to a hydrogen fuel cell to produce electrical energy, in accordance with one embodiment of the present invention.

Fig. 2 is a schematic diagram of a power system in accordance with another embodiment of the invention in which a hydrogen-containing product mixture produced in alcohol reforming is introduced as fuel into a hydrogen fuel cell to produce electrical energy, and in which the effluent from the hydrogen fuel cell is sent to an internal combustion engine that is also supplied with an independent alcohol feedstock.

Description of the preferred embodiments

According to the invention, mixtures of copper and other metals, in particular mixtures of copper and nickel, are used as catalysts for the dehydrogenation (i.e. reforming) of alcohols. It has been found that copper-containing catalysts comprising a metal support structure, for example catalysts prepared by depositing copper onto a nickel sponge support structure, show improved activity as catalysts for reforming primary alcohols, such as methanol and ethanol, in the gas phase. The catalysts used in the practice of the present invention are more stable to, and particularly active for, the thermal decomposition of ethanol to hydrogen, methane, carbon monoxide and carbon dioxide at moderate temperatures. The hydrogen produced may be utilized, for example, to produce energy by converting the hydrogen to water in a fuel cell and by combusting the methane along with any residual hydrogen in the gas stream exiting the fuel cell. The combustion process may either drive a generator to produce additional electrical energy or be utilized in an internal combustion engine to produce mechanical energy. Such a power system provides a convenient way of obtaining energy from ethanol, with other advantages: the combustion can minimize undesirable emissions while providing heat to the reforming catalyst bed. More broadly, the product mixture produced in the reforming of primary alcohols according to the present invention can be used as a source of hydrogen and/or carbon monoxide in chemical processing applications (e.g., carbonylation, hydrogenation, and hydroformylation) and in material processing applications. In addition, the alcohol reforming catalyst described herein may be used to produce a product mixture comprising hydrogen and carbon monoxide, referred to as syngas from an alcohol feedstock.

A. Catalyst and process for preparing same

In one embodiment of the invention, the alcohol dehydrogenation or reforming catalyst comprises a copper-containing active phase at the surface of a metallic support structure comprising copper and/or one or more non-copper metals. The catalyst generally comprises at least about 10% by weight copper, preferably from about 10% to about 90% by weight copper, and more preferably from about 20% to about 45% by weight copper. The catalyst may comprise a substantially homogeneous structure such as a copper sponge, a single phase alloy containing copper, or a multiphase structure having more than one discontinuous phase. For example, the copper-containing active phase may be present as a discontinuous phase on the surface of the supporting structure, such as a copper coating or outer layer; as part of a surface layer or homogeneous catalyst structure. In the case where the copper-containing active phase comprises a discontinuous phase at the surface of the support structure, the metal support structure may be wholly or partially coated with the copper-containing active phase. For example, as in the particularly preferred embodiments described below, the catalyst comprises a copper-containing active phase on the surface of a metal sponge supporting structure comprising nickel. Such catalysts comprise from about 10 wt.% to about 80 wt.% copper, and more preferably from about 20 wt.% to about 45 wt.% copper. The balance of the catalyst preferably consists of nickel and less than about 10 weight percent aluminum or other metal. Furthermore, in the preferred embodiment where the metal supporting structure comprises nickel, it is important to note that copper is miscible with nickel in all ratios. In this way, a catalyst comprising a copper-containing active phase at the surface of a nickel support structure may not necessarily have a phase boundary between the copper-containing active phase and the support structure.

The activity of the dehydrogenation catalyst can be increased by increasing the surface area, as is conventional in catalysis. Thus, it is generally preferred for the freshly prepared catalyst to have a particle size of at least about 10m²Surface area in g, said value being determined by the Brunauer-Emmett-Teller (BET) method. More preferably, the catalyst has about 10m²G to about 100m²BET surface area per g, even more preferably about 25m²G to about 100m²A BET surface area of/g, and still more preferably about 30m²G to about 80m²BET surface area in g.

In reforming ofIn a certain preferred embodiment of the alcohol, the surface of the catalyst preferably comprises nickel atoms in an amount that promotes decarbonylation of an aldehyde, such as acetaldehyde. Preferably, the surface comprises from about 5 to about 100 μmol/g of nickel, wherein the value is determined by the method described in Schmidt, "Surfaces of Raney^®Catalysts, "in Catalysis of Organic Reactions, pages 45-60 (M.G.Scarosand M.L.Pruner, eds., Dekker, New York, 1995). More preferably, the surface nickel concentration is from about 10 to about 80. mu. mol/g, most preferably from about 15 to about 75. mu. mol/g.

1. Load structure

The support structure of the alcohol dehydrogenation catalyst comprises a metal. Suitable metal supporting structures may include various structures and components. Preferably, the load bearing structure comprises a metal having a tensile strength and/or yield strength higher than copper. Thus, according to a preferred embodiment, the supporting structure comprises a non-copper metal. The non-copper metal can comprise a single metal or multiple metals. In this preferred embodiment, at least about 10% by weight of the metal supporting structure is non-copper metal. In a particularly preferred embodiment, at least about 50% (more preferably at least about 65%, at least about 80%, at least about 85% or even at least about 90%) by weight of the metal supporting structure is non-copper metal. In another particularly preferred embodiment, the supporting structure comprises at least about 10% by weight non-copper metal and at least about 50% (more preferably from about 60% to about 80%) by weight copper.

The metal or alloy from which the metal supporting structure is made preferably has a higher tensile strength and/or yield strength than copper alone. The composition particularly preferably has a yield strength of at least about 70MPa, more preferably at least about 100MPa, and even more preferably at least about 110 MPa. The composition also particularly preferably has a tensile strength of at least about 221MPa, more preferably at least about 275MPa, and even more preferably at least about 300 MPa. For example, a composition comprising 90 wt% copper and 10 wt% nickel is reported to have a yield strength of 110MPa and a tensile strength of 303 MPa; a composition comprising 70 wt% copper and 30 wt% nickel is reported to have a yield strength of 138Mpa and a tensile strength of 372 Mpa; a composition comprising 70 wt% copper and 30 wt% zinc is reported to have a yield strength of 124Mpa and a tensile strength of 331 Mpa. See Krisher and Siebert, Perry's Chemical Engineers' Handbook, pages 23-42 to 23-49 (6 th edition, McGraw Hill, New York, NY 1984).

Preferably, the non-copper metal of the metal supporting structure is selected from the group consisting of nickel, cobalt, zinc, silver, palladium, gold, tin, iron and mixtures thereof. More preferably, the metal supporting structure comprises nickel. Nickel is generally most preferred because, for example: (1) nickel is relatively inexpensive compared to other suitable metals such as palladium, silver and cobalt, (2) nickel in combination with copper has been shown to promote the decarbonylation of acetaldehyde to methane and carbon monoxide, and (3) copper is generally less difficult to deposit on a support structure containing nickel than copper on a support structure containing significant amounts of other suitable metals. For example, copper can be deposited on a nickel-containing support structure using a simple electrochemical displacement deposition process. Other techniques exist for depositing copper on a supporting structure containing other suitable non-copper metals (e.g., electroless plating and metal-organic chemical vapor deposition).

It is often desirable to deposit copper on the surface of the metal supporting structure using electrochemical displacement deposition (also described in the prior art as "immersion plating") described in detail below. In that case, the metal supporting structure preferably comprises the following metals: the reduction potential for this metal is lower than that for metallic copper, i.e., the reduction potential for this metal is below about +343 mv relative to NHE (standard hydrogen electrode). Non-copper metals having such a reduction potential include, for example, nickel, zinc, tin, iron, and cobalt. The presence of such a metal near the surface of the support structure allows copper metal to be deposited simply on the surface of the support structure by contacting the surface with a solution of a copper salt, typically a cu (ii) salt. More specifically, during electrochemical displacement deposition, such metals near the surface of the support structure tend to be oxidized (and enter the solution as ions) upon contact with a copper ion solution. When this occurs, copper ions in solution near the surface of the support structure are reduced to copper metal, which in turn deposits on the surface of the support structure. This reaction occurs, for example, when a supported structure comprising nickel is contacted with a copper salt solution, as shown in equation 5 below:

(5)

as previously mentioned, when preparing a catalyst by depositing copper on the surface of the support structure using electrochemical displacement deposition, it is particularly preferred to use a support structure comprising nickel, since nickel has at least four desirable characteristics: (1) the reduction potential for this metal is lower than that for copper metal, (2) is more stable under the alcohol dehydrogenation reaction conditions of the present invention, (3) has higher mechanical strength and wear resistance than copper, and (4) the nickel/copper catalyst promotes the decarbonylation of acetaldehyde to carbon monoxide and methane.

When the support structure comprises more than one metal, it is preferred that at least about 80 wt.% (more preferably at least about 85 wt.%, even more preferably at least about 90 wt.%, even more preferably substantially all) of the metals in the support structure are in the form of an alloy. In a particularly preferred embodiment, the metals form a replacement alloy (also referred to as a "single phase alloy"), wherein the alloy has a single, continuous phase. Multi-phase alloys (i.e., alloys containing at least 2 discontinuous phases) may also be used as load bearing structures. In embodiments where the copper-containing active phase is deposited on a copper-containing multi-phase support structure, the copper tends to preferentially coat the copper-rich portions of the surface of the multi-phase support structure relative to the copper-poor surface portions. Whether the alloy is single-phase or multi-phase depends on the composition of the alloy and their concentrations. Generally, for example, a metallic load structure consisting essentially of nickel and copper is a single phase at any nickel concentration. However, for example, when the load bearing structure consists essentially of copper and zinc, there are many zinc concentrations (typically greater than about 35 wt.% concentration) that result in the alloy being biphasic.

It should be appreciated that the supporting structure may contain non-metal atoms (e.g., boron, carbon, silicon, nitrogen, phosphorus, etc.) in addition to metal atoms. Alloys containing such non-metals are generally described in the art as "interstitial alloys". Load bearing structures comprising such alloys may have various advantages, such as enhanced mechanical strength. However, catalysts comprising interstitial alloys typically contain at least about 70 weight percent metal.

In a particularly preferred embodiment, the support structure is a metal sponge comprising copper and/or one or more of the above-mentioned suitable non-copper metals. As used herein, the term "metal sponge" means having a thickness of at least about 10m²(ii) a porous form of metal or metal alloy per gram BET surface area. Preferred metal sponge supporting structures have a thickness of at least about 20m²BET surface area per gram, more preferably at least about 35m²A/g, even more preferably at least about 50m²A/g, and even more preferably at least about 70m²(ii) in terms of/g. It has been found in accordance with the present invention that the copper-containing active phase at the surface of the metal sponge supporting structure produces a material of the sponge supporting structure that exhibits mechanical strength, high surface area, high thermal conductivity and density, combined with the desired copper catalytic activity.

The metal sponge support and the formed catalyst may be in powder or pellet form. Moreover, the alcohol dehydrogenation catalyst may be used in the form of a monolith prepared by mixing the catalyst of the present invention into the surface of a suitable porous substrate (e.g., a honeycomb). Generally, in order to minimize back pressure in the reformers described below, catalysts in pellet and monolith forms are preferred. Furthermore, monolithic catalysts may be more stable to mechanical damage due to vibration (e.g., in vehicular applications) and/or chemical attack in the reaction medium.

It is to be noted that when the catalyst of the present invention is used in the form of pellets or monolith, it is desirable that only a portion of the pellets or monolith may comprise the metal sponge used to support the copper-containing active phase. That is, the alcohol reforming catalyst may comprise a non-porous matrix providing strength and shape to a fixed bed or monolith catalyst, while still providing one or more copper-containing active phases having a thickness of at least 10m for supporting the copper-containing active phase²Porous (i.e., metal sponge) region of BET surface area. Non-porous materials suitable for use as a fixed bed or monolith substrate may generally include any thermally stable and chemically stable under electroplating and reforming conditionsA stable material. While non-metallic substrates may be used, metallic substrates such as stainless steel, copper, nickel, cobalt, zinc, silver, palladium, gold, tin, iron, and mixtures thereof are generally more preferred.

When the metal sponge support is in powder form, the metal sponge preferably has an average particle size of at least about 0.1 μm, preferably from about 0.5 to about 100 μm, more preferably from about 15 to about 100 μm, even more preferably from about 15 to about 75 μm, and still more preferably from about 20 to about 65 μm. When the catalyst is in pellet or monolith form, the size of the pellets or monolith substrate into which the catalyst of the present invention is incorporated, as well as the size of the openings in any such monolith structure, can be varied as desired for the reformer design, as will be appreciated by those skilled in the art.

The metal sponge supporting structure may be prepared by techniques generally known to those skilled in the art. See generally Lieber and Morritz, adv.cat., 5, 417(1953) (for a review of metal sponges). Reference may also be made to Hawley's Condensed Chemical Dictionary, 13 th edition, page 621 (Rev. by Richard J. Lewis, Sr., Van Nostrand Reinhold, New York, NY 1997) (describing the process for preparing iron sponges).

References describing the preparation of nickel sponges include, for example, Augustine, Robert l., catalysis Hydrogenation Techniques and Applications in organic synthesis, annexes at pages 147-49 (Marcel Dekker, inc., 1965). Reference may also be made to Hawley's Condensed Chemical Dictionary, 13 th edition, page 955 (Rev. by Richard J. Lewis, Sr., Van Nostrand Reinhold, New York, NY 1997) (describing the well-known technique for preparing nickel sponge by leaching aluminum from an alloy containing 50 wt% nickel and 50 wt% aluminum using a 25 wt% caustic soda solution). In the case of nickel sponge production, the metal supporting structure is preferably substantially free of unactivated regions and has been washed substantially free of alumina. Unreacted aluminum tends to react with steam under reforming conditions to form alumina that can impede diffusion and provide acid sites for ethanol dehydration.

References describing the preparation of copper/zinc sponges include, for example, Bridgewater et al, appl.Catal., 7, 369 (1983). Such references also include, for example, m.s. wainwright, raney copper and raney copper-zinc catalysts, chem.ind. (Dekker), 68, 213-30 (1996).

References describing the preparation of nickel/iron sponges include, for example, Becker and Schmidt, raney nickel-iron catalyst, ger.

References describing the preparation of nickel/cobalt sponges include, for example, orcard et al, raney nickel-cobalt catalyst preparation and performance, j.cat., 84, 189-99 (1983).

According to a preferred embodiment, the supporting structure comprises a nickel/copper sponge (i.e., a copper-doped nickel sponge or a nickel-doped copper sponge), as described in co-assigned U.S. patent No. 6,376,708. References describing the preparation of nickel/copper sponges also include, for example, Young et al, j.cat., 64, 116-23(1980), and Wainwright and Anderson, j.cat., 64, 124-31 (1980).

Suitable metal sponges include materials available under the trade name RANEY from w.r.grace & Co. (davison division, Chattanooga, TN), as well as materials from any source that are described in the art as "RANEY metals. Raney metals may be obtained, for example, by leaching aluminum from an alloy of aluminum and a base metal (e.g., nickel, cobalt, copper) with a caustic soda solution. Various metal sponges are also commercially available from: for example, Gorwara Chemical Industries (Udaipur, India); activated Metals & Chemicals, Inc (Sevierville, TN); Degussa-Huls Corp. (Ridgefield Park, NJ); engelhard Corp. (Iselin, NJ) and Aldrich chemical co. (Milwaukee, WI).

According to another preferred embodiment of the invention, the supporting structure comprises a nickel sponge. Examples of suitable commercially available nickel sponges include, for example, RANEY 2800 (manufacturer designation: having at least 89 wt% Ni; no greater than 9.5 wt% Al; no greater than 0.8 wt% Fe; average particle size 20-60 μm; specific gravity about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal) based on catalyst slurry weight containing 56% solids in water), RANEY4200 (manufacturer designation: having at least 93 wt% Ni; no greater than 6.5 wt% Al; no greater than 0.8 wt% Fe; average particle size of 20-50 μm; about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal) based on catalyst slurry weight containing 56% solids in water), RANEY 4310 (manufacturer designation: having at least 90 wt% Ni; no greater than 8 wt% Al; 0.5-2.5 wt% Mo; no greater than 0.8 wt% Mo; no greater than 0.5 wt% Mo in water) Fe of (2); the average grain diameter is 20-50 μm; a specific gravity of about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal) based on the weight of the catalyst slurry containing 56% solids in water, RANEY 3110 (manufacturer designates: has at least 90 wt% Ni; 0.5-1.5 wt% Mo; not more than 8.0 wt.% Al; not more than 0.8 wt.% Fe; the average grain diameter is 25-65 μm; a specific gravity of about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal) based on catalyst slurry weight containing 56% solids in water, RANEY 3201 (manufacturer designates: has at least 92 wt% Ni; not more than 6 wt.% Al; not more than 0.8 wt.% Fe; 0.5-1.5 wt% Mo; the average grain diameter is 20-55 μm; a specific gravity of about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal) based on the weight of a catalyst slurry containing 56% solids in water, RANEY 3300 (features described in U.S. Pat. No. 5,922,921 are as follows: contains 90-99.1 wt% of Ni; not more than 8.0 wt.% Al; not more than 0.8 wt.% Fe; 0.5-1.5 wt% Mo; the average grain diameter is 25-65 μm; a specific gravity of about 7; bulk density of 1.8-2.0kg/l (15-17lbs/gal), based on catalyst slurry weight containing 56% solids in water, RANEY 2724 (Cr-promoted) and RANEY 2724 (Cr-promoted); catalysts sold by gorwara chemical Industries described as "raney nickel"; a-4000 and A-5000 sold by Activated metals & Chemicals, Inc.; nickel ABMC sold by Degussa-Huls corp. and "raney nickel" sold by Aldrich Chemical Co under number 22, 167-8.

Examples of fixed bed matrices containing metal sponge supporting structures include nickel sponge pellets as described in european patent No. EP0648534a1 and U.S. patent No. 6,284,703, the disclosures of which are incorporated herein by reference. Nickel sponge pellets, particularly those used as fixed bed catalysts, are commercially available, for example, from w.r.grace & Co. (Chattanooga, TN) and Degussa-Huls Corp. (ridgfield Park, NJ).

2. Deposition of copper-containing active phases

The copper-containing active phase may be deposited onto the surface of the metal-bearing structure using a variety of techniques for depositing metals onto metal surfaces that are well known in the art. These techniques include, for example, liquid phase methods such as electrochemical displacement deposition and electroless plating; and vapor deposition methods such as physical deposition and chemical deposition. Suitable methods for depositing copper on the surface of a metal-loaded structure are described in co-assigned U.S. patent No. 6,376,708 and co-assigned co-pending U.S. patent application No. 09/832,541, published as US-2002-. U.S. patent No. 6,376,708 and U.S. application No. US-2002-0019564-a1 are incorporated by reference herein in their entirety.

It is important to note that copper is at least partially miscible with most of the supported structural metals and is completely miscible with nickel. Thus, it has been found that the copper deposition process can produce a catalyst having copper, or more particularly, a copper-containing active phase, at the surface of the support structure as part of a discontinuous phase, such as an outer layer or coating, at the surface of the support structure as part of a surface layer, or copper can migrate from the surface of the support structure into the bulk of the support structure. Without being bound to a particular theory, it is believed that the catalyst surface may move, sinter, or otherwise structurally reform during the deposition and reaction of the alcohol reforming process, resulting in these changes in form in the copper-containing active phase. Nevertheless, it has been found that the copper deposition process results in an overall increase in the copper content of the catalyst, with the deposited copper being predominantly present at or near the surface of the freshly prepared catalyst, which is more copper-rich than before deposition.

a. Electrochemical displacement deposition of copper

As previously described, copper may be deposited onto the surface of the metallic supporting structure by electrochemical displacement deposition, wherein copper ions in a copper salt solution in contact with the supporting structure are reduced to metallic copper, while non-copper metal near the surface of the supporting structure is oxidized. The metallic copper forms a coating on the surface of the load structure, and non-copper ions enter the solution. A general description of electrochemical displacement deposition can be found, for example, in Krulik and Mandich, "Metallic Coatings (Survey)", Kirk-Othmer encyclopedia of Chemical Technology 4 th edition, volume 16, pages 258-91 (J.I. Kroschwitz and M.Howe-Grant, eds., Wiley, New York, NY, 1995). More specific description of the electrochemical displacement deposition of copper on a metal sponge supporting structure can be found in co-assigned U.S. patent No. 6,376,708, the contents of which are incorporated herein by reference.

In a particularly preferred method for depositing copper on a metallic support structure, the electrochemical displacement deposition is first carried out under alkaline conditions, followed by the electrochemical displacement deposition under acidic conditions. In a similar, particularly preferred embodiment, no copper is added in the acidic step, but copper redeposition can occur, since the monovalent copper which has been deposited on the support in the alkaline step dissolves and redeposits. This procedure is described in example 6 below. Preferably, the metal supporting structure is substantially free of surface oxidation during copper deposition. In the case where the metal support structure has an oxidized surface (e.g., when the support structure is exposed to air (even underwater) for 6 months or longer), it is particularly preferred to pretreat the support structure with a reducing agent. For example, the support structure may be stirred in a sodium borohydride solution, which preferably contains at least 1g of sodium borohydride per 25g of metal support structure, and has a pH of at least about 10. Typically, contact of the support structure with the reducing agent for about 5 minutes to about 2 hours at room temperature is sufficient to substantially remove the surface oxidized support structure.

To start the two-step, basic/acidic electrochemical displacement deposition, the metal support structure is slurried in an aqueous or alcoholic solution, preferably in water, and the pH is adjusted to 7. Copper salts are added to the metal support structure slurry, preferably in a solution comprising the copper salt and a chelating agent, especially an amine chelating agent such as EDTA. Preferably, the copper salt solution comprises about 10 wt% to about 30 wt% copper relative to the metal supporting structure. Suitable copper salts for displacement deposition include, for example (not provided for an exhaustive list) the nitrates, sulfates, hydrochlorides and acetates of copper. Salts containing copper in the divalent state (i.e., cu (ii)) are generally most preferred. Although salts containing monovalent and trivalent copper may also be used, they are generally less preferred because they are generally unstable, not readily available, and/or insoluble in alkaline mixtures.

Then, an alkali metal hydroxide (e.g., NaOH) or another suitable base is slowly added to the slurry, preferably while continuously stirring and bubbling with nitrogen. The alkali metal hydroxide solution preferably comprises at least 1 molar equivalent of alkali metal hydroxide relative to the copper salt, more preferably from about 1.1 to about 1.6 molar equivalents of alkali metal hydroxide relative to the copper salt. Although this step involves a displacement deposition reaction, the partially oxidized metal from the support structure remains tightly bound to and bound to the support structureIs removed in the next acidic step. In addition, the first step alkaline displacement deposition reaction results in cuprous oxide (Cu)₂O) and metallic copper are deposited on the surface of the supporting structure.

After the alkaline displacement deposition, the supernatant is removed by decantation or other methods, and copper is further deposited on the surface of the catalyst support structure under acidic conditions. After decantation, the metal-loaded structure is slurried again in an alcohol or aqueous solution. An acid buffer is added to the metal-loaded structure slurry to lower the pH to below about 4. The temperature of the buffer is preferably between about 40 ℃ and about 90 ℃. The acid buffer may comprise any suitable chelating agent capable of controlling residual metals in solution and subsequently lowering the pH. More preferably, the acid buffer preferably has a pKa of about 1 to about 4 to maintain the pH of the plating bath at about 1 to about 4. Preferably, the acid buffer is a gluconic acid/gluconate buffer. Gluconic acid is preferred for depositing copper on the surface of the nickel containing metal supporting structure, as gluconic acid is a good chelator of residual aluminum ions present in solution. In addition, it is necessary to point out that the use of buffers based on phosphoric acid is generally less preferred, because of the risk of forming insoluble phosphate precipitates. The above copper salt (preferably as a copper salt solution) may then be added to the metal support structure slurry over a period of about 5 to about 40 minutes with continuous stirring and nitrogen sparging. Preferably, about 0.2 to about 0.4 molar equivalents of sulfuric acid are added in place of the copper salt solution, as described in example 6. This step increases the activity of the catalyst for the water gas shift reaction. The agitation can then be stopped to allow the catalyst to settle so that the supernatant can be removed by decantation or other means.

It is important to note that when the catalyst structure is in pellet or monolith form, the copper plating may be different from that described above. For example, commercially available pelletized metal sponge supports are often incompletely activated. Activation of commercially available pelletized supports typically involves removal of most to the deep layer, typically up to about 200 μm, of aluminum to produce a metal sponge-type structure. However, the core of the pellet typically still contains a significant concentration of the non-activated alloy enriched in zero valent aluminum. In this way, the aluminum at the core may react with steam and ethanol under reforming conditions, forming cracks and compromising mechanical integrity. Therefore, a fully activated metal sponge is preferred. An example of a fully activated material is hollow sphere activated nickel described in U.S. patent No. 6,284,703.

In addition, diffusion can limit plating inside the fixed bed carrier. Thus, it is preferable to carry out the plating of the fixed bed support at room temperature or below because the ratio of the diffusion rate to the plating reaction rate is more suitable at low temperatures. To avoid excessive consumption of copper concentration inside the carrier, which would occur if a large portion of the copper were consumed by deposition outside the carrier, it is also preferred to use an elevated copper concentration in the plating bath. Example 10 describes an example of a preferred fixed bed carrier plating step.

Another preferred embodiment for preparing a mechanically robust catalyst under reforming conditions is to first deposit a layer of a nickel-aluminum alloy on a substrate that is thermally and chemically stable under electroplating and reforming conditions, typically by thermal spraying. Suitable substrates may generally comprise steel or another metal, but non-metallic substrates may also be used. The thickness of the layer is preferably between 5 and 500 μm, more preferably between 10 and 150 μm. The preparation of supported metal sponge films is described in U.S. Pat. No. 4,024,044 and Silitto et al, Mat.Res.Soc.Sym.Proc., Vol.549, pp.23-29 (1999). The nickel-aluminum alloy layer provides a metal support structure and is preferably activated prior to copper plating.

b. Electroless copper plating

Electroless plating can also be used to deposit copper-containing active phases onto the surface of the metal supporting structure. Similar to electrochemical displacement deposition, electroless plating involves the reduction of copper ions to copper metal in solution in contact with a supporting structure. However, unlike electrochemical displacement deposition, substantially all of the copper ions are reduced by the external reducing agent rather than the support structure itself. When copper ions are reduced to copper metal in solution, the copper metal forms a coating on the surface of the supporting structure. The use of electroless plating to deposit copper on the surface of a metal supporting structure is described in detail in co-assigned U.S. patent No. 6,376,708, the contents of which are incorporated herein by reference.

3. Integrated copper-containing active phase

In another embodiment of the invention, the catalyst does not comprise copper coated on a metal support structure (i.e., no discontinuous copper-containing active phase is deposited or coated on the catalyst surface). Instead, copper is mixed with other metals that provide desirable properties in a catalyst composition having a copper-containing active phase at the surface. The catalyst composition may be substantially homogeneous. Preferably, such catalysts are in the form of copper-containing metal sponges (e.g., nickel/copper sponges).

4. Optional auxiliary metal

The catalyst may optionally contain one or more auxiliary metals in addition to the copper and non-copper metals comprising the catalyst mass as described above. Suitable auxiliary metals are selected from the group consisting of chromium, titanium, niobium, tantalum, zirconium, vanadium, molybdenum, manganese, tungsten, cobalt, nickel, bismuth, antimony, germanium and zinc. For example, the use of auxiliary metals, particularly zinc and chromium, to extend the useful life of copper catalysts and to maintain or enhance their activity for the water gas shift reaction is well known in the art and has been described by Lloyd et al at Catalyst Handbook, p.309-312 (2 nd edition, M.V.Twig eds., Manson Press, London, 1996). The presence of one or more such metals generally extends the life of the catalyst, i.e., extends the period of time during which the catalyst is available for alcohol reforming before its activity decreases to an unacceptable level. Among the above elements, vanadium, chromium, molybdenum, zinc and combinations thereof are particularly preferable, and are preferably present in the form of oxides on the surface of the catalyst.

The amount of auxiliary metal may vary within wide limits. Preferably, the total concentration of the auxiliary metal in the catalyst is at least about 10 parts by weight per million parts by weight of copper. More preferably, the total concentration of the auxiliary metal in the catalyst is from about 0.002 wt% to about 5 wt%, more preferably from about 0.002 wt% to about 2.5 wt%, even more preferably from about 0.005 wt% to about 2 wt%, and even more preferably from about 0.5 wt% to about 1.5 wt%. Typically, the total concentration of auxiliary metals does not exceed about 5 wt.%. Although higher concentrations of the auxiliary metal may be used, no additional benefit is obtained by exceeding this concentration, and the activity of the catalyst generally decreases.

The one or more auxiliary metals may be contained in the metal supporting structure and/or in the copper-containing active phase at the surface of the supporting structure. Where it is desired to include an auxiliary metal in the alloy-metal support structure, the auxiliary metal is preferably mixed into the alloy at the same time as the alloy is formed. Where it is desired to include an auxiliary metal in the copper-containing active phase of the surface of the support structure, the auxiliary metal may in some cases be deposited simultaneously with the copper. However, in the case where copper is deposited by displacement deposition or electroless plating (as described above), the auxiliary metal is preferably added to the catalyst after copper deposition, because the auxiliary metal may dissolve under displacement deposition conditions and inhibit electroless plating. The auxiliary metal can generally be added to the surface of the catalyst simply by contacting the catalyst with a solution containing a salt of the auxiliary metal (e.g., sulfate, nitrate, hydrochloride, etc.). Methods of depositing an oxide of an auxiliary metal onto a copper sponge are also suitable for deposition onto the surface of the metal-supporting structure of the present invention after the electroplating process is complete and can be found in U.S. Pat. No. 5,292,936 to Franczyk et al, the entire disclosure of which is incorporated herein by reference.

B. Preferred alcohol reforming reaction conditions and power systems

The alcohol reforming process of the present invention generally comprises contacting a feed gas mixture comprising an alcohol reactant with a catalyst bed comprising a copper-containing catalyst as described above in a dehydrogenation reaction zone.

The dehydrogenation reaction zone preferably comprises a continuous flow system configured to ensure low back pressure and sufficient heat transfer to initiate and sustain the endothermic reaction. Reformer designs that achieve adequate heat transfer are well known and described, for example, in U.S. patent No. 3,522,019 to Buswell et al and U.S. patent nos. 5,935,277 and 5,928,614 to autenieth et al. Each patent describes a catalytic reforming alcohol reactor that provides heat by exchanging heat with a heat source through a heat transfer wall. The preferred heat source for heating the dehydrogenation reaction zone most often comprises exhaust gas from the partial oxidation of partially reformed alcohol or from a separate combustion reaction using alcohol or another fuel source. As described below, a particularly preferred embodiment of the present invention is to use the exhaust gas from a combustion chamber, preferably downstream of the dehydrogenation reaction zone, as the heat source for the dehydrogenation reaction zone.

For example, as described by Gersten et al in "The Physics and Chemistry of Materials," Wiley, New York, 2001, page 144, copper and nickel have thermal conductivities of 401W/m.K and 91W/m.K. respectively at 300K, whereas conventional reforming catalyst Materials such as α -alumina have a thermal conductivity of 36W/m.K, silica is 1.4W/m.K, and magnesium oxide is 36W/m.K. at 300K, copper-containing catalysts comprising The metal-supported structures of The present invention preferably have a thermal conductivity of at least about 50W/m.K, more preferably at least about 70W/m.K, and especially at least about 90W/m.K. at 300K.

The alcohol reforming reaction is generally carried out in the gas phase at a temperature above about 100 ℃. However, in accordance with the present invention, it is preferred to reform the alcohol in the feed gas mixture at a temperature of less than about 400 ℃. More preferably, the reforming reaction is carried out at a temperature of from about 150 ℃ to about 400 ℃, more preferably at a temperature of from about 200 ℃ to about 375 ℃, and most preferably at a temperature of from about 250 ℃ to about 325 ℃. For example, it has been found that when a copper-plated metal sponge catalyst, particularly a copper-plated metal sponge comprising nickel or copper-doped nickel, is used in the process of the present invention, ethanol reforming can be carried out at a sufficiently high conversion rate at a temperature of from about 250 ℃ to about 300 ℃.

Because the reforming reaction is endothermic, additional heat must be supplied to maintain the desired temperature in the dehydrogenation zone. Generally, during the alcohol reforming reaction, the temperature of the reforming reaction in the catalyst bed can be controlled by any means known in the art. Preferably, the temperature of the catalyst bed is controlled to be isothermal or to have a positive temperature gradient over its length (i.e. the temperature increases gradually from the inlet to the outlet of the bed). For example, the alcohol reaction gas may be introduced into the catalyst bed at a temperature from about 10 ℃ to about 50 ℃ below the desired catalyst bed outlet temperature while providing the necessary additional heat to the dehydrogenation reaction zone to maintain the desired temperature regime in the catalyst bed.

When reforming ethanol, it is important to note that operating within a narrow temperature range and avoiding excessive temperatures reduces the formation of excessive methane by-product. The formation of methane (i.e., "methanation") is undesirable because the reaction consumes expensive hydrogen product at a rate that requires 3 moles of hydrogen per 1 mole of methane produced. Operating at low pressure can also avoid excessive methanation. Thus, the pressure at the catalyst bed inlet is preferably less than about 30psig, more preferably less than about 10 psig.

The dehydrogenation reaction produces a gaseous product mixture containing hydrogen that can be introduced into a hydrogen fuel cell to produce electrical energy. Thus, a particularly preferred embodiment of the present invention is the dehydrogenation of primary alcohols such as methanol, ethanol or mixtures thereof to produce hydrogen for the production of electrical energy in fuel cells. For example, suitable applications for the hydrogen produced in the product mixture of the invention include its use as a hydrogen fuel source in polymer dielectric fuel cells, alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. For polymer dielectric fuel cells, particularly Proton Exchange Membrane (PEM) fuel cells, hydrogen is generally the most preferred fuel source. PEM fuel cells typically operate at temperatures of about 80 ℃ or less. Thus, the present invention enables alcohol reforming at low temperatures, which has the advantage of simplifying the design of the power system and improving energy efficiency.

When the alcohol reforming product mixture of the present invention is used as a hydrogen source for a fuel cell, the dehydrogenation reaction is preferably carried out in combination with the water gas shift reaction described above to minimize the amount of carbon monoxide in the product mixture. Therefore, it is often preferred to mix an alcohol with water in the feed gas mixture fed to the dehydrogenation reaction zone to facilitate the removal of carbon monoxide from the product stream by the water-gas shift reaction. For example, the alcohol is preferably mixed with at least 1 molar equivalent of water, most preferably from about 1.05 to about 1.2 molar equivalents of water, prior to introduction into the dehydrogenation reaction zone.

In general, the catalysts of the invention described above have some activity for the water gas shift reaction. However, in certain embodiments, it may be preferred to use additional water-gas shift reaction catalysts in order to achieve lower concentrations of carbon monoxide in the product mixture. When an additional water gas shift catalyst is used, the water gas shift catalyst may be mixed with the reforming catalyst in the reforming catalyst bed, or placed downstream of the reforming catalyst in the same or a separate catalyst bed.

For embodiments of the invention using a separate water gas shift catalyst, it is important to note that most conventional water gas shift reactions are typically run at about 200 ℃ lower than the typical operating temperature of the reforming catalyst of the invention. Thus, it may be necessary or desirable to cool the reformate mixture prior to contact with the water-gas shift catalyst. Generally, any means for cooling the product known in the art may be used, including heat exchangers. In one embodiment, water may be introduced into the reformate gas between the reformer and the water-gas shift reactor. In this embodiment, introducing water after the reformer can reduce or remove the amount of water in the alcohol-water feed gas mixture fed to the reformer.

Although not necessary or critical to the present invention, it may be desirable in certain embodiments of the present invention to reduce, or otherwise control, the carbon monoxide in the reformate stream exiting the dehydrogenation reaction zone, the water-gas shift catalyst bed, and/or the fuel cell using one or more additional measures. Examples of suitable means of controlling or reducing carbon monoxide have been widely described, for example by Pettersson et al, Int' l J. hydrogen Energy, Vol.26, pp.243-64 (2001), and include selective oxidation of carbon monoxide, methanation of carbon monoxide and implementation of anode blow-by.

In the preferred embodiment wherein the hydrogen produced in the dehydrogenation zone is fed to a fuel cell to produce electrical power, the dehydrogenation reaction is preferably conducted in a fixed bed reactor containing a packed bed of the copper-containing catalyst described above. Measures are preferably taken to minimize back pressure, for example by adding an inert solid diluent to the catalyst bed to separate the catalyst particles and maintain spacing between them. The diluent is preferably a material that does not contain acidic sites capable of catalyzing the dehydration of ethanol to ethylene and is thermally stable under the reaction conditions. Silicon carbide and activated carbon that has not been acid activated are examples of preferred diluents.

Alternatively, backpressure can also be minimized by using a copper-containing catalyst comprising a metal sponge supporting structure in the form of pellets rather than powder. Such shaped load bearing structures include nickel sponge pellets as described in european patent EP0648534a1 and U.S. patent No. 6,284,703, the disclosures of which are incorporated herein by reference. Nickel sponge pellets, particularly for use as fixed bed catalysts, are commercially available from, for example, w.r.grace & Co. (Chattanooga, TN) and Degussa-Huls Corp. (ridgfield Park, NJ). In other alternative preferred embodiments, the catalyst may be used in a monolith form prepared by mixing the catalyst of the present invention into the surface of a suitable porous substrate (e.g., honeycomb) in order to minimize back pressure within the reforming reactor.

An embodiment of a system for generating electrical energy from the reforming of ethanol according to the present invention is described with reference to fig. 1. Although the following description is disclosed with specific reference to the dehydrogenation of ethanol using the above copper-containing catalyst, it should be recognized that the principles described are generally applicable to the dehydrogenation of other primary alcohols including methanol or mixtures of ethanol and methanol.

An alcohol/water feedstock comprising a mixture of ethanol and water is introduced into a dehydrogenation reaction zone containing a packed bed 101 of a copper-containing dehydrogenation catalyst comprising a metal-supported structure. The feedstock comprising an ethanol/water mixture is preferably introduced into the dehydrogenation reaction zone in the form of a gaseous feedstock mixture, for example, after vaporization in a vaporizer (not shown) as is well known in the alcohol reforming art. The catalyst bed 101 is heated with a heating jacket 102 to maintain the desired temperature in the dehydrogenation zone. Reforming of the ethanol/water mixture in the catalyst bed 101 produces a product mixture comprising hydrogen, carbon monoxide, carbon dioxide, water, and methane. The product mixture is then passed to an additional catalyst bed 103 containing a suitable water gas shift catalyst to selectively oxidize carbon monoxide to carbon dioxide. Compact water gas shift modules have been developed and are commercially available from, for example, the Hydrogen Source (South Windsor, CT). The product mixture exiting the catalyst bed 103 is then cooled to a suitable temperature (typically 80 ℃ or less) and introduced into a hydrogen fuel cell 105 (e.g., a proton exchange membrane fuel cell) along with an oxygen source (e.g., air) to generate electrical energy. Electrical energy is produced by the reaction of hydrogen with oxygen to produce water in a fuel cell. It should be understood that the fuel cell may contain a plurality of fuel cells (i.e., a fuel cell stack), as is customary for fuel cell applications.

The fuel cell effluent, which contains water vapor, methane and carbon dioxide, is then combusted with air in a combustor 107 supplied with a source of oxygen (e.g., air). Suitable combustors may include gas turbines, heat engines, internal combustion engines, or other devices for driving an electrical generator 109 that generates additional electrical energy. The hot combustion effluent from the generator 109 can be recycled to the heating jacket 102 as a heat source for heating the dehydrogenation zone reforming catalyst bed 101.

The combustion of the fuel cell effluent also provides a convenient method of treating power system emissions. Undesirable components in the fuel cell effluent, such as acetaldehyde, carbon monoxide, residual alcohol, and/or methane, will be largely converted to carbon dioxide by combustion in the combustion chamber 107. The residual hydrogen will be oxidized to water. There have been recent reports of the potential for evolved hydrogen emissions to be a threat to the ozone layer. (see Tromp et al, Science, 300, 1740-2, (2003)). In addition, the exhaust gas from the internal combustion engine (unlike the exhaust gas of a conventional PEM fuel cell power system) is hot enough to allow the catalytic converter to function effectively, further reducing harmful emissions.

In vehicle power applications, it is preferred to introduce fuel cell effluents, primarily carbon dioxide, methane, and trace amounts of hydrogen, water vapor, and carbon monoxide, into a combustion system capable of providing electrical and/or mechanical energy. In such applications, the combustion system may include an internal combustion engine that produces torque to propel the vehicle, or an internal combustion engine in combination with an electrical generator that produces additional electrical energy.

In a particularly preferred embodiment, a power system comprising a variable fuel internal combustion engine capable of combusting alcohol, methane, or a mixture thereof is used to combust the fuel cell effluent and provide a mechanical power source to propel the vehicle. The additional energy is provided by one or more electric motors supplied with direct current generated by a fuel cell, similar to the configuration used for hybrid vehicles. Such a preferred power system is shown in FIG. 2 using ethanol as the fuel.

Referring to fig. 2, a water-ethanol feedstock mixture (with a slight molar excess of water) is introduced into a hydrogenation reaction zone containing a packed bed 201 containing a copper-plated nickel sponge reforming catalyst and a water-gas shift catalyst 201B and heated by a heating jacket 202. As previously described, the alcohol is reformed in the packed bed, producing a reformate comprising hydrogen, carbon dioxide and methane. The reformate from the dehydrogenation zone is fed to a hydrogen fuel cell 205 at a suitable temperature along with a source of oxygen (e.g., air) to produce direct current electrical power. Methane and carbon dioxide do not degrade the performance of PEM fuel cells. The effluent of the fuel cell 205 is primarily methane and carbon dioxide, which are combusted with a source of oxygen (e.g., air) in an internal combustion engine 207. The hot exhaust gases from the internal combustion engine are then used as a heat source for heating jacket 202, preferably by a catalytic converter (not shown), before exiting the system as exhaust gases. In this way, waste heat from the internal combustion engine is utilized to provide the heat required for the endothermic ethanol reforming reaction. The design of reformers capable of exchanging heat between a separate hot gas stream and a reforming catalyst bed is well known in the art.

A significant disadvantage of operating fuel cells in vehicular transport applications occurs at start-up due to the endothermic nature of the alcohol reforming reaction. In particular, the fuel cell is unable to "cold start" the vehicle (i.e., there is a time delay in starting until the reformer and fuel cell reach their design operating temperatures before sufficient energy is generated to drive the vehicle). Thus, in a particularly preferred embodiment of the invention, the combustion driven power system's internal combustion engine 207 described with reference to FIG. 2 is a variable fuel internal combustion engine that can be operated using an alcohol feedstock or another source of cold start fuel 211 separate from the fuel cell effluent. The alcohol feedstock of the internal combustion engine is preferably anhydrous and thus separated from the ethanol-water feedstock of the reforming reactor. At start-up, the engine is operated using alcohol as fuel from an independent cold start fuel source 211 to provide similar cold start performance as a vehicle powered using a conventional internal combustion engine. In normal operation, after the reformer and fuel cell reach their design operating temperatures, the vehicle may be powered primarily by an electric motor supplied with direct current electricity generated by a hydrogen fuel cell. The internal combustion engine continues to function to compensate for part of the base power required by the vehicle, but the internal combustion engine is primarily fueled with methane from the fuel cell effluent, rather than alcohol from a separate cold start fuel source 211. If the driving conditions require additional transient power, the vehicle may generate additional torque using the internal combustion engine. Additionally, the methane in the fuel cell effluent entering the internal combustion engine may be supplemented with alcohol from the independent cold start fuel source 211 to produce this additional torque. Additional supplemental power may also be provided by the battery.

In addition to providing better cold start and transient power performance, the preferred configuration allows the power system to be constructed at a very low cost. Hydrogen fuel cells are typically the most expensive component in fuel cell based vehicle power systems. The power system described herein requires significantly less fuel cell capacity than conventional designs because the peak power is supplemented by the internal combustion engine. The design only requires fuel cell capacity sufficient to provide a portion of the base power, the remainder being provided by an internal combustion engine operating with alcohol and/or methane.

Examples

The following examples are intended only to further illustrate and explain the present invention. Therefore, the present invention should not be limited to any details of these examples.

Other examples of preparation for copper-plated metal catalysts are described in co-assigned U.S. patent No. 6,376,708 and co-assigned co-pending U.S. patent application Ser. No. 09/832,541, publication No. US-2002-0019564-A1. U.S. patent No. 6,376,708 and U.S. publication No. US-2002-0019564-A1 are incorporated herein by reference in their entirety.

EXAMPLE 1 preparation of copper-nickel plated sponge catalyst

This example illustrates the preparation of a copper nickel plated sponge catalyst using displacement deposition.

In a glass beaker, a nickel sponge supported structure (68.7g, RANEY4200, from W.R. Grace, Chattamooga, TN) was suspended in nitrogen-bubbled water (400 ml). Add 12% NaBH in 14M NaOH with stirring₄(50g) And (3) solution. Intense foaming was observed for 1 minute. After stirring for 10 minutes, the catalyst was allowed to settle and the supernatant decanted. An additional portion of nitrogen sparged water (400ml) was added and stirred briefly. The catalyst was allowed to settle again before decanting the supernatant.

A third portion of nitrogen sparged water (250ml) was added to the catalyst. Glacial acetic acid (ca. 8ml) was added to lower the pH to 5. The catalyst suspension was then bubbled with nitrogen-bubbled CuSO₄·5H₂O (54.0g, copper content 20% by weight with respect to the catalyst) and a solution of ethylenediaminetetraacetic acid (EDTA) tetrasodium dihydrate (108.0g) in water (300ml) were contacted. NaOH (2.5N, 73.0ml) was added over 103 minutes with continuous stirring and nitrogen sparging. The pH of the suspension increased from 6.8 to 11.3. The catalyst was allowed to settle, the beaker wrapped with electrically heated tape, and the blue supernatant decanted.

Mixing CuSO₄·5H₂O (67.5g, 25 wt% copper relative to catalyst) was dissolved in nitrogen sparged water (200ml) to form a copper solution. A suspension of catalyst was formed by adding a hot mixture (74 ℃) of 50% gluconic acid (159.0g), 2.5N NaOH (54ml) and nitrogen sparged water (250ml) to the catalyst. The copper solution was then added to the catalyst suspension with stirring over 95 minutes while applying heat to the beaker with an electric heating tape (final temperature 72 ℃). The pH value is reduced from 3.8 to 3.1. The catalyst was allowed to settle and the green supernatant decanted.

The catalyst was washed with nitrogen-sparged water (700 ml). The wash was decanted and 75.6g of dark copper catalyst was recovered and stored under water. The composition of the catalyst was 66.1% Ni, 30.4% Cu and 3.5% Al.

When a small sample (about 1g) of the catalyst was suspended in water, the catalyst was found to consist of two parts. These two parts consist of a lower layer of copper and an upper layer of grey. After drying with hydrogen at 130 ℃ by Schmidt, "Surfaces of Raney^®BET surface area and surface nickel concentration were determined by the methods described in Catalysis ", Catalysis of organic reactions, pages 45-60 (M.G.Scaros and M.L.Pruner, eds., Dekker, New York, 1995). The analytical results are shown in Table 1. Data for the RANEY4200 matrix are also presented for comparison.

TABLE 1

Test specimen	BET surface area	Surface nickel
			RANEY 4200	70m2/g	700-800μmole/g
Upper part of the upper part	36.8m2/g	54.8μmole/g
			Lower layer part	40.1m2/g	32.1μmole/g

Example 2 ethanol reforming with a copper-nickel plated sponge catalyst

This example illustrates the use of a copper-plated nickel sponge catalyst for reforming ethanol.

The experiment was carried out in a stainless steel reactor containing a stainless steel 304 tube (457.2 mm long, 12.7mm internal diameter) wound with a spiral cable heater. A pipe for preheating the ethanol feedstock was connected to the top of the reactor. The catalyst is distributed on a glass fibre plug placed on a hollow insert located at the bottom of the tubular reactor. A thermocouple was placed at the bottom of the catalyst bed and the reaction temperature was monitored and controlled using a spiral cable heater. The effluent was analyzed by gas chromatography using a thermal conductivity detector. The outlet of the reactor was at atmospheric pressure.

The reactor was packed as follows. After insertion of the fresh glass fiber plugs, an aqueous slurry of 325 mesh silicon carbide (1.0g) (obtained from Alfa Aesar, Ward Hill, MA) was passed through the reactor to form the basis of a catalytic bed located on top of the glass fibers. A slurry of silicon carbide (1.5g) and the catalyst of example 1 (2.02g) was then passed through the reactor. No breakthrough was observed, indicating that all of the catalyst loaded remained in the reactor. The catalyst was dried in the reactor under nitrogen at 120 ℃ overnight before use.

Table 2 shows the results of ethanol reforming using different temperatures, flow rates and water concentrations in the feed. The catalyst was used for ethanol reforming for a total of about 30 hours before the data in table 2 was collected. Note that the methane yield and methane-based mass balance can exceed 100% due to analytical error and methanation of CO as shown in equation 6:

(6)

also note that table 2 and the examples below omit the hydrogen yield. Although hydrogen is measured directly in a gas chromatograph, the thermal conductivity detector is less sensitive to hydrogen than carbon-containing molecules, thus resulting in more scatter in the data. Thus, the hydrogen yield can be more accurately calculated from the yields of carbon-containing compounds such as carbon monoxide, carbon dioxide, and methane.

TABLE 2

Ethanol product distribution under different conditions, reported as molar yield relative to the amount of ethanol feedstock

In the raw materials H of (A) to (B)2O1 (wt.％)	Temperature of (℃)	Raw materials (ml/min)	CH3CH2OH％	CH3C(O)H％	CH4％	CO2％
							50％	250	0.15	Trace amount of	4.3	95.1	6.5
	0.30	21.7	26.7	52.2	4.5
								0.40	42.3	29.6	25.7	1.5
	0.80	62.8	27.9	9.2	0.2
								1.20	74.7	20.9	4.5	Trace amount of
50％	280	0.20	0	0	101.0								24.5
							0.40	14.2	19.6	66.8	6.0
		0.80	50.4	26.2	22.9							2.1
								64.2	21.9	14.0	1.1
	30％	250	0.30	44.2	14.8							40.8	1.5
280						0.30	12.9	9.6	76.9	3.7
		300	0.30	0	2.9						97.5	6.7
300						0.20	0	0	102.0	15.1
		320	0.20	0	0						104.6	42.0
10％						250	0.20	22.2	8.3	69.5			1.3
	250	0.30	47.1	12.1	40.8						0.5
						280	0.20	6.2	3.9	90.5		2.1
	0％	250	0.20	0	0						104.4		3.5
						0.25	9.9	3.9	87.5	0.8
			0.40	33.3	9.0						58.3	0.3
						0.60	50.9	11.1	38.3	0.1
			0.90	78.3	9.0						11.8	Trace amount of

¹The remainder of the feedstock is ethanol.

Example 3 methanol reforming with a copper-nickel plated sponge catalyst

This example illustrates the reforming of methanol using a copper-plated nickel sponge catalyst.

The experiment was carried out as in example 2 above, but using a feedstock consisting of 70 wt% methanol and 30 wt% water. The results are shown in Table 3 below.

Table 3 methanol reformate distribution obtained by reforming 70% methanol

Temperature of	Flow rate of raw material (ml/min)	Methanol	Methane	CO	CO2
						300℃	0.40	13.3％	3.2％	81.2％	2.3％
300℃	0.20	2.4％	3.7％	86.9％	7.0％
						320℃	0.20	1.7％	5.5％	75.5％	17.9％

Example 4 ethanol reforming over extended run cycle

This example illustrates the ability of the catalyst of the present invention to support high conversion rates over extended ethanol reforming cycles.

The experiment was carried out under essentially the same conditions as in example 2, but the reactor was first packed by depositing silicon carbide (1.0g) and then with a slurry comprising the catalyst of example 1 (2.50g) and silicon carbide (5.0 g). The temperature was monitored by a thermocouple inserted down the interior cavity of the reactor to a point about 10.2cm above the bottom of the catalyst bed.

The reactor was operated in such a way that the temperature of the product mixture leaving the catalyst bed was kept at 280 ℃. The temperature of the upper thermocouple was maintained relatively constant at about 430 ℃. An ethanol/water feed mixture (ethanol/water weight ratio 70: 30) was introduced into the dehydrogenation zone at a rate of 0.3ml/min with 100sccm of nitrogen. The reactor was run for 44 hours during which time the pressure in the reactor was increased from 28psig to 80 psig. During this time, no ethanol or acetaldehyde was detected in the product mixture and the methane conversion was 100% within analytical error. Table 4 below gives the CO and CO values during the experiment₂Selectivity of (2).

TABLE 4

Ethanol reformate yield using 70% ethanol feedstock at 280 ℃

Time (hours)	CO％	CO2％
			2	34	66
5	60	40
			12	81	19
20	85	15

25	85	15
			31	88	12
35	88	12
			40	88	12
44	87	13

Example 5 ethanol reforming in a packed bed with thermal gradient

This example illustrates that high conversion and low methanation are achieved by reforming ethanol with a copper-coated nickel sponge catalyst at low pressure, a thermal gradient with an outlet temperature of 300 ℃ or less, and an inlet temperature below the outlet temperature.

A vertically mounted stainless steel tubular reactor (457.2 mm long, 12.7mm internal diameter) wound with a spiral cable heater similar to example 2 was used, but the ethanol feed stream was introduced at the bottom of the reactor and the catalyst bed was placed at the top of the reactor between two glass fiber plugs. Thermocouples were placed upstream and downstream of the catalyst bed. The catalyst prepared in example 1 (2.50g) was used. A mixture of 70% ethanol/30% water by weight was fed to the reactor at a rate of 0.1ml/min and the reactor was heated at a controlled rate to give an outlet temperature of the catalyst bed effluent of 275 ℃. The temperature upstream of the catalyst bed was stabilized at 245 ℃ for the duration of the experiment. The pressure upstream of the reactor does not exceed 5 psig.

Table 5 shows the high conversion achieved during continuous operation over 200 hours. After 286 hours of production, the outlet temperature was raised to 300 ℃. The data collected at this temperature are shown in Table 6. No acetaldehyde or ethanol was detected in the product mixture. The conversion rate also increases to 100% when the temperature is raised to 300 ℃. No detectable methanation was found throughout the experiment.

TABLE 5

Example 5 product yield at 275 deg.C

Time (hours)	CO％	CO2％	CH4％	CH3C(O)H％	Ethanol%
						10	96.1	2.0	101.9	ND	ND
20	97.1	1.8	101.1	ND	ND
						40	96.3	2.5	101.2	ND	ND
60	96.5	2.5	101.0	ND	ND
						80	96.3	2.7	101.0	ND	ND
100	95.4	3.4	101.1	ND	ND
						120	96.5	2.6	100.9	ND	ND
140	96.6	2.4	100.8	0.05	ND
						160	96.8	2.2	100.9	ND	ND
180	97.1	2.1	100.8	ND	ND
						201	96.6	2.2	101.1	ND	ND
220	95.8	2.2	100.8	0.57	ND
						265	96.1	2.4	99.5	0.71	0.31％
285	95.3	2.1	99.3	1.03	0.62％

ND is not detected

TABLE 6

Example 5 product yield after increasing the outlet temperature to 300 deg.C

Time (hours)	CO％	CO2％	CH4％	CH3C(O)H％	Ethanol%
						290	91.4	8.2	100.4	ND	ND
295	91.2	8.2	100.6	ND	ND
						300	91.9	7.7	100.3	ND	ND
306	91.5	8.2	100.3	ND	ND
						310	91.5	7.7	100.5	ND	ND

EXAMPLE 6 preparation of copper-nickel plated sponge catalyst

This example illustrates a plating process for a metal sponge substrate that provides similar conversion and better carbon dioxide levels and requires less copper sulfate than the process of morgensten et al (U.S. patent No. 6,376,708) or in example 1. The process also uses high solids concentrations, thus minimizing waste volume. In this example, the matrix and catalyst mass were determined by the water displacement method, assuming a density coefficient of 1.16.

The nickel sponge supported structure (48.3g, RANEY4200 from Grace Davison, Chattarooga, TN) was transferred to a 1L beaker of water with nitrogen sparge and the excess water was decanted off. Mixing CuSO₄·5H₂O (47.45g) and Na₄EDTA·2H₂A nitrogen sparged solution of O (94.92g) in water (400ml) was added to the catalyst and the slurry was stirred while 2.5N NaOH (91ml) was added over 48 minutes. The pH increased from 8.4 to 11.4. The blue clear solution was decanted and the beaker was wrapped with electrical heating tape.

A hot mixture of 50% gluconic acid (11g) and water (400ml) was added to the catalyst. Heat was applied and a mixture of concentrated sulfuric acid (5.70g) and water (50ml) was added over 43 minutes. The temperature stabilized between 59 ℃ and 60 ℃ and the pH dropped from 5.2 to 2.2. The mixture was stirred for an additional 45 minutes. The final pH was 2.8.

The blue clear solution was decanted and nitrogen sparged water (500ml) was added and the pH adjusted to 7 with sodium hydroxide. This step helps to remove the remaining nickel and EDTA. The catalyst was allowed to settle and the supernatant removed by decantation. 51.3g of a catalyst having the following composition was recovered: 76.8% Ni, 19.9% Cu, 3.2% Al and 0.2% Fe.

Example 7 ethanol reforming Using a copper-nickel plated sponge catalyst

This example illustrates ethanol reforming in the presence of a catalyst comprising copper on the surface of a nickel sponge supporting structure.

The catalyst (2.50g) prepared according to example 6 was placed in a reactor having the same configuration as in example 2 above. An alcohol feedstock comprising 70 wt% ethanol and 30 wt% water was introduced into the reactor at a rate of 0.1 ml/min. The outlet temperature was gradually increased to 300 ℃ over the first 24 hours of the experiment. Note that the conversion is slightly lower than in example 5, but the CO is converted to CO₂To a much greater extent. The degree of methanation is also higher, but it decreases over time as seen in the next example.

TABLE 7

Example 7 effluent composition

Time of day (hours)	Outlet temperature	CO％	CO2％	CH4％	CH3C(O)H％	Ethanol%
							7	270℃	81.7	14.3	103.5	0.2	ND
15	270℃	80.7	15.2	101.8	0.6	0.5％
							20	270℃	68.5	26.8	104.0	0.3	ND
31	300℃	44.1	49.8	106.1	ND	ND
							35	300℃	47.2	46.9	105.9	ND	ND
40	300℃	43.7	51.0	105.1	ND	ND
							45	300℃	47.2	48.6	104.2	ND	ND

Example 8 ethanol reforming over extended run cycle

This example illustrates isothermal reforming of ethanol over an extended period of time. This example further illustrates the gradual decline in methanation using the catalyst of example 6 while maintaining a high CO₂And (4) conversion rate.

The same reactor installation as described in example 2 was charged with the catalyst prepared according to example 6 (2.50g) and operated at a flow rate of 0.1ml/min using a feed comprising 70 wt% ethanol/30 wt% water, as in example 7 above. The outlet temperature of the catalyst bed was maintained at 300 ℃. No acetaldehyde or ethanol was detected in the product mixture during the run. As shown in table 8, methanation steadily decreased during the experiment.

TABLE 8

Example 8 effluent composition

Time (hours)	CO％	CO2％	CH4％
				10	57.6	37.5	104.8
20	64.0	31.9	104.1
				32	64.1	32.5	103.3
41	66.4	30.8	102.8
				50	70.9	27.1	102.0
61	76.9	21.8	101.3
				70	77.8	20.8	101.3
85	60.3	37.2	102.5
				91	69.6	28.9	101.5
100	68.6	30.5	100.9
				110	77.9	21.8	100.3

Example 9 methanol reforming Using a copper-nickel plated sponge catalyst

This example illustrates the activity and stability of the catalyst of the invention for reforming methanol under mild, near isothermal conditions.

The catalyst prepared in example 1 (2.52g) was mixed with polymer pellet diluent (1.0g, Tenax TA, 80-100 mesh, from Alltech Associates, Deerfield, IL) and charged to a reactor as described in example 2, which was horizontal in this experiment. A60% methanol/40% water mixture (0.1ml/min, water: methanol molar ratio 1.19: 1) was added to the reactor at a rate of 0.1ml/min, with the exit temperature maintained at 320 ℃. The pressure was maintained below 5psig throughout the run. The temperature upstream of the catalyst bed was about 335 ℃ and varied from 309 ℃ to 369 ℃ during the experiment.

Table 9 shows the results. Temperatures higher than those required for ethanol are required to achieve methanol conversions above 90%. The methane yield is generally about 1%, similar to the value for ethanol.

TABLE 9

Example 9 effluent

Time (hours)	CO％	CO2％	CH4％	Methanol%
					10	70.5	25.6	2.9	1.0
20	79.5	17.1	1.8	1.6
					30	83.4	13.3	1.8	1.5
40	84.7	11.5	1.7	2.2
					50	85.5	9.7	1.4	3.3
60	84.1	5.8	0.4	9.7
					70	83.1	4.7	0.5	11.8
80	84.7	6.4	0.6	8.3
					90	83.3	5.0	0.6	11.1
100	80.3	9.1	1.0	9.6
					110	79.5	8.1	0.9	11.5

Example 10 preparation of copper-coated nickel sponge catalyst for fixed bed operation

This example describes the preparation of a fixed bed catalyst by plating copper onto a nickel sponge fixed bed supported structure.

Will be distributed in the pellet matrix (45 pellets, containing 6.79g of methylalst)^®α -1401-X018, commercially available from Degussa AG, Hanau, Germany), nickel sponge supporting structures were dried under vacuum at 120 ℃ overnight, purged with nitrogen, the pellets were loaded in a nitrogen atmosphere along the length of a plastic tube (internal diameter 9.525), between glass fibre plugs, andso as to contain CuSO₄·5H₂O (10.67g) and Na₄EDTA·2H₂A bath of a solution of O (21.34g) in water (300ml) was circulated over the catalyst at room temperature while a mixture of 2.5N NaOH (26ml) and water (50ml) was added dropwise over 124 minutes. During plating, the bath solution was kept in a stirred tank under nitrogen atmosphere and circulated between the catalyst and the tank using a peristaltic pump. The pH increased from 10.0 to 12.0. The catalyst was then washed with water.

Then, adding CuSO₄·5H₂A mixture of O (6.67g), gluconic acid (5.2g), 2.5N NaOH (2.7g) and water (300ml) was added to the cell and circulated over the catalyst at room temperature for 2 hours. The catalyst was washed with water, then dried under vacuum at 120 ℃ overnight, purged with nitrogen. 6.65g (98%) of catalyst were recovered.

Example 11 ethanol reforming under isothermal conditions

This example illustrates the performance of a catalyst for reforming ethanol under near isothermal conditions (compared to ethanol reforming with a temperature gradient in the reactor described in example 7).

The experiment involved reforming ethanol using the catalyst prepared in example 6, and the catalyst bed was kept near isothermal at 280 ℃. To eliminate the temperature gradient, a modified reactor was used. The feed gas mixture (70 wt% ethanol/30 wt% water) was pumped at 0.10ml/min through a stainless steel tube (1.58 mm outer diameter) into a preheater consisting of a vertical stainless steel tube (457.2 mm long, 9.525mm inner diameter, 12.7mm outer diameter) filled with stainless steel balls (3 mm and 4mm diameter) and wrapped with a cable heater. The feed tube is wound in a spiral fashion around the cable heater and is connected to the preheater at the bottom.

The top (outlet) of the preheater was attached to a stainless steel tube (177.8 mm long, 9.525mm inner diameter, 12.7mm outer diameter) containing the catalyst (2.49g) prepared in example 6, which was packed between two passivated glass fibre plugs. The upper tube (reactor) was wrapped with a separate cable heater. A thermocouple at the connection of the preheater to the reactor tube was used to control the preheater and maintain the upstream temperature of the catalyst bed constant, while a thermocouple at a position just above the catalyst bed (downstream of the catalyst bed) controlled the cable heater and maintained the downstream (outlet) temperature of the catalyst bed at 280 ℃. These two temperatures were stable and held constant within two hours with fluctuations within 1 ℃. All components were thermally insulated and the downstream system for gas chromatography was the same as described in example 2.

Table 10 shows that high conversion and stability are achieved by operating at near isothermal conditions. The pressure upstream of the preheater was maintained below 15psi throughout the experiment. Note that under isothermal conditions, excess methane formation decayed to a steady state value of about 2% after 8 hours. Traces of ethanol were found, but below the quantitative limit. Acetaldehyde only reached a quantifiable level at the end of the run. Both were less than 1% throughout the experiment.

Watch 10

Product yield from example 11 reforming at 280 ℃ isothermal conditions

Time (hours)	H2	CO	CH4	CO2	Acetaldehyde
						0.6	149.6％	10.3％	111.7％	78.0％	0.0％
1.2	103.9％	81.6％	103.7％	14.7％	0.0％
						2.0	97.2％	90.2％	102.4％	7.4％	0.0％
4.0	94.9％	90.1％	103.0％	6.9％	0.0％
						5.9	96.8％	90.3％	102.8％	6.9％	0.0％
8.2	96.3％	91.4％	102.0％	6.6％	0.0％
						10.3	95.2％	92.9％	101.9％	5.2％	0.0％
15.3	97.3％	91.3％	102.0％	6.7％	0.0％
						19.8	98.7％	90.7％	101.8％	7.5％	0.0％
25.8	99.6％	91.6％	101.5％	6.8％	0.0％
						30.3	96.9％	92.5％	101.7％	5.8％	0.0％
40.8	98.9％	91.3％	101.5％	7.2％	0.0％
						60.3	99.0％	92.2％	101.5％	6.3％	0.0％
79.5	101.5％	86.4％	101.9％	11.6％	0.0％
						100.5	99.5％	90.6％	101.4％	8.0％	0.0％
120.1	104.6％	88.9％	101.0％	10.0％	0.0％
						141.1	97.7％	94.1％	101.3％	4.5％	0.0％
149.1	97.5％	95.4％	100.5％	2.9％	0.6％

EXAMPLE 12 ethanol reforming on a copper-nickel-plated sponge fixed bed catalyst

This example illustrates the performance of a copper nickel plated sponge fixed bed catalyst in reforming ethanol.

The experiment involved reforming ethanol using the catalyst prepared in example 10 (1.46g, 10 pellets) at 300 ℃ under isothermal conditions in the same facility as described in example 11. A feed gas mixture comprising 70 wt% ethanol and 30 wt% water was introduced at a flow rate of 0.06ml/min to provide a ratio between flow rate and catalyst comparable to the previous example using 2.50g catalyst and a 0.10ml/min feed gas mixture.

As shown by the data in table 12 below, the fixed bed material achieved high conversion (> 85%) at 300 ℃. The fixed bed catalyst also differs from the powdered catalyst in that the decrease in methanation occurs more slowly and continuously, taking about 20 hours at 300 ℃.

TABLE 12

Results of example 12

Time (hours)	H2	CO	CH4	CO2	Acetaldehyde	Ethanol
							0.9	27.0％	0.7％	147.3％	52.0％	0.0％	0.0％
1.8	43.6％	1.1％	140.4％	58.5％	0.0％	0.0％
							3.8	53.0％	7.5％	134.6％	58.0％	0.0％	0.0％
6.1	66.9％	27.0％	124.5％	48.5％	0.0％	0.0％
							8.1	78.2％	49.6％	116.4％	34.0％	0.0％	0.0％
10.1	85.4％	61.3％	111.9％	26.6％	0.1％	0.0％
							14.8	92.6％	74.6％	105.8％	17.7％	1.0％	0.0％
20.2	96.4％	79.2％	98.4％	12.6％	2.4％	2.5％
							30.2	98.6％	78.0％	89.3％	10.0％	4.7％	6.6％
40.3	98.4％	78.5％	85.1％	7.8％	5.1％	9.2％
							60.7	107.0％	86.0％	92.7％	9.4％	2.6％	3.3％
80.2	102.4％	76.3％	76.9％	6.3％	6.5％	13.8％
							99.8	99.9％	70.6％	70.5％	5.8％	7.9％	18.7％
120.0	95.5％	67.0％	67.4％	5.9％	8.1％	21.7％

EXAMPLE 13 ethanol reforming over fixed bed catalyst at different temperatures

This example describes the use of a fixed bed catalyst to reform ethanol at different temperatures.

This experiment was continued with the experiment described in example 12 above, with changes in flow rate and temperature. Isothermal conditions were maintained. Table 13 summarizes the performance of the catalyst at 300 ℃ and 320 ℃ at different flow rates.

Watch 13

Ethanol reforming with temperature and flow rate variation as described in example 12

Temperature of (℃)	Flow rate of flow (ml/min)	H2	CO	CH4	CO2	CH3C(O)H	CH3CH2OH
								300	0.01	100.5％	64.1％	106.1％	29.5％	0.2％	0.0％
300	0.02	118.9％	83.4％	90.9％	16.9％	1.7％	2.7％
								300	0.03	111.3％	82.1％	86.0％	11.5％	3.3％	6.9％
320	0.02	104.0％	64.8％	105.5％	29.7％	0.0％	0.0％
								320	0.03	109.3％	78.2％	100.3％	20.7％	0.2％	0.2％
320	0.045	118.2％	87.9％	93.5％	15.3％	0.7％	1.0％
								320	0.06	126.1％	92.2％	89.1％	13.3％	1.4％	1.3％

After the experiment was completed, many catalysts were found to be reduced to powders. This loss of structural integrity is due to the unactivated aluminum in the center of the matrix reacting with water vapor under the reaction conditions to form alumina.

The present invention is not limited to the above-described embodiments and may be variously modified. The above description of the preferred embodiments is intended only to acquaint others skilled in the art with the invention, its principles and its practical application so that others skilled in the art may modify and apply the invention in various ways, to better suit the requirements of a practical application.

In respect of the use of the words "comprise", "comprises", "comprising", and the like (in the english language "comprises", "comprising", and the like) throughout this specification (including the following claims), it is noted that, unless the context clearly dictates otherwise, these words are used on a basic and clear understanding that: they should be interpreted as "including" the listed items, rather than "excluding" the listed items, and it is intended that each term should be so interpreted upon analysis of the entire text.

Claims (87)

1. A method of reforming an alcohol, the method comprising: a feed gas mixture comprising an alcohol is contacted with a reforming catalyst comprising copper at the surface of a metal sponge supporting structure to produce a reformate mixture comprising hydrogen.

2. A process as set forth in claim 1, wherein the feed gas mixture comprises a primary alcohol selected from the group consisting of methanol, ethanol, and mixtures thereof.

3. The process of claim 2 further comprising introducing hydrogen and oxygen from the reforming product mixture into a fuel cell to produce electrical energy.

4. A process as set forth in claim 1, wherein the reforming catalyst has a mass of about 10m as measured by the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

5. A process as set forth in claim 4, wherein the reforming catalyst has a mass of about 25m as measured by the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

6. A process as set forth in claim 5, wherein the reforming catalyst has a mass of about 30m as measured by the Brunauer-Emmett-Teller method²G to about 80m²Surface area in g.

7. A process as set forth in claim 1, wherein the reforming catalyst comprises at least 10% by weight copper.

8. A process as set forth in claim 1, wherein the reforming catalyst comprises from about 10% to about 90% by weight copper.

9. A process as set forth in claim 1, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 10m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

10. A process as set forth in claim 9, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 50m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

11. A process as set forth in claim 10, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 70m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

12. A process as set forth in claim 9, wherein the metal sponge supporting structure comprises nickel.

13. A process as set forth in claim 12, wherein the metal sponge supporting structure comprises at least 50% by weight nickel.

14. A process as set forth in claim 13, wherein the metal sponge supporting structure comprises at least 85% by weight nickel.

15. A process as set forth in claim 12, wherein the reforming catalyst comprises from about 10% to about 80% by weight copper.

16. A process as set forth in claim 15, wherein the reforming catalyst comprises from about 20% to about 45% by weight copper.

17. A process as set forth in claim 12, wherein the reforming catalyst comprises from about 5 to about 100 μmol/g nickel at the surface of said catalyst.

18. A process as set forth in claim 17, wherein the reforming catalyst comprises from about 10 to about 80 μmol/g nickel at the surface of said catalyst.

19. A process as set forth in claim 18, wherein the reforming catalyst comprises from about 15 to about 75 μmol/g nickel at the surface of said catalyst.

20. A process as set forth in claim 12, wherein the feed gas mixture comprises a primary alcohol selected from the group consisting of methanol, ethanol, and mixtures thereof.

21. The process of claim 12 further comprising introducing hydrogen and oxygen from the reforming product mixture into a fuel cell to produce electrical energy.

22. A process as set forth in claim 1, wherein said feed gas mixture is contacted with said reforming catalyst at a temperature of less than about 400 ℃.

23. A process as set forth in claim 1, wherein said feed gas mixture is contacted with said reforming catalyst at a temperature of from about 200 ℃ to about 375 ℃.

24. A process as set forth in claim 23, wherein said feed gas mixture is contacted with said reforming catalyst at a temperature of from about 250 ℃ to about 325 ℃.

25. The process of claim 1 wherein the reforming catalyst is incorporated onto the surface of a pellet or monolith substrate.

26. A process as set forth in claim 25, wherein the reforming catalyst comprises a nickel sponge supporting structure.

27. A process for reforming ethanol, the process comprising contacting a feed gas mixture comprising ethanol with a reforming catalyst at a temperature of less than about 400 ℃ to produce a reforming product mixture comprising hydrogen, the reforming catalyst comprising copper at the surface of a metal supporting structure.

28. A process as set forth in claim 27, wherein said feed gas mixture is contacted with said reforming catalyst at a temperature of from about 250 ℃ to about 300 ℃.

29. The process as set forth in claim 27 wherein the reforming catalyst has a thermal conductivity of at least about 50W/m-K at 300K.

30. The process as set forth in claim 29 wherein the reforming catalyst has a thermal conductivity of at least about 70W/m-K at 300K.

31. The process as set forth in claim 30 wherein the reforming catalyst has a thermal conductivity of at least about 90W/m-K at 300K.

32. A process as set forth in claim 27, wherein said process further comprises introducing hydrogen and oxygen from the reforming product mixture into a fuel cell to produce electrical energy.

33. A process as set forth in claim 27, wherein the reforming catalyst has a mass of about 10m, as measured by the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

34. A process as set forth in claim 33, wherein the reforming catalyst has a mass of about 25m, as measured by the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

35. A process as set forth in claim 34, wherein the reforming catalyst has a mass of about 30m, as measured by the Brunauer-Emmett-Teller method²G to about 80m²Surface area in g.

36. A process as set forth in claim 27, wherein the reforming catalyst comprises at least about 10% by weight copper.

37. A process as set forth in claim 36, wherein the reforming catalyst comprises from about 10% to about 90% by weight copper.

38. The method of claim 27, wherein the metal supporting structure comprises a metal sponge.

39. A process as set forth in claim 38, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 10m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

40. A process as set forth in claim 39, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 50m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

41. A process as set forth in claim 40, wherein the metal sponge supporting structure of the reforming catalyst has a thickness of at least about 70m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

42. A process as set forth in claim 38, wherein the metal sponge supporting structure comprises nickel.

43. A process as set forth in claim 42, wherein the metal sponge supporting structure comprises at least 50% by weight nickel.

44. A process as set forth in claim 43, wherein the metal sponge supporting structure comprises at least 85% by weight nickel.

45. A process as set forth in claim 42, wherein the reforming catalyst comprises from about 10% to about 80% by weight copper.

46. A process as set forth in claim 45, wherein the reforming catalyst comprises from about 20% to about 45% by weight copper.

47. A process as set forth in claim 42, wherein the reforming catalyst comprises from about 5 to about 100 μmol/g nickel at the surface of said catalyst.

48. A process as set forth in claim 47, wherein the reforming catalyst comprises from about 10 to about 80 μmol/g nickel at the surface of said catalyst.

49. A process as set forth in claim 48, wherein the reforming catalyst comprises from about 15 to about 75 μmol/g nickel at the surface of said catalyst.

50. A process as set forth in claim 42, further comprising introducing hydrogen and oxygen from the reforming product mixture into a fuel cell to produce electrical energy.

51. The method of claim 27 wherein the reforming catalyst is incorporated onto the surface of a pellet or monolith substrate.

52. A process as set forth in claim 51, wherein the reforming catalyst comprises a nickel sponge supporting structure.

53. A method of generating electrical energy from a fuel cell, the method comprising:

contacting a feed gas mixture comprising ethanol with a dehydrogenation catalyst in a dehydrogenation reaction zone to produce a product mixture comprising hydrogen, wherein the dehydrogenation catalyst comprises copper at the surface of a metal support structure;

introducing hydrogen and oxygen from the product mixture to a fuel cell to produce electrical energy and a fuel cell effluent comprising methane;

introducing the fuel cell effluent and oxygen into a combustion chamber; and is

Combusting the fuel cell effluent in the combustion chamber.

54. A process as set forth in claim 53, wherein said feed gas mixture further comprises water.

55. The process of claim 54, wherein said dehydrogenation zone further comprises a water-gas shift catalyst effective to catalyze a water-gas shift reaction between carbon monoxide produced by the dehydrogenation of ethanol and water to form carbon dioxide and hydrogen.

56. The method of claim 55, wherein the water gas shift catalyst is separated from a dehydrogenation catalyst.

57. The method of claim 53, further comprising transferring heat of combustion generated in the combustion chamber to the dehydrogenation reaction zone.

58. The method of claim 53, further comprising capturing combustion energy to produce mechanical energy and/or additional electrical energy.

59. The method of claim 58, wherein the combustion energy from the combustion chamber is used to drive a generator to produce additional electrical energy.

60. The method of claim 58 wherein the dehydrogenation zone and the combustion chamber are part of a vehicle powertrain and the generated electrical and/or mechanical energy is used to power the vehicle.

61. The method of claim 53, further comprising introducing a separate cold start fuel source into the combustion chamber and combusting the separate cold start fuel source in the presence of oxygen.

62. The method of claim 61, wherein the fuel cell effluent and cold start fuel source are introduced into a variable fuel source internal combustion engine capable of combusting methane and/or a separate cold start fuel source.

63. The method of claim 62, wherein the dehydrogenation zone and variable fuel source internal combustion engine are part of a vehicle powertrain, the method further comprising capturing combustion energy for producing mechanical energy and/or additional electrical energy, and using the mechanical energy and/or the electrical energy to propel the vehicle.

64. A process as set forth in claim 53, wherein said feed gas mixture is contacted with said dehydrogenation catalyst at a temperature of less than about 400 ℃.

65. A process as set forth in claim 64, wherein said feed gas mixture is contacted with said dehydrogenation catalyst at a temperature of from about 250 ℃ to 300 ℃.

66. The process of claim 53, wherein the dehydrogenation catalyst has a thermal conductivity of at least about 50W/m-K at 300K.

67. The process of claim 66, wherein the dehydrogenation catalyst has a thermal conductivity of at least about 70W/m-K at 300K.

68. The process of claim 67, wherein the dehydrogenation catalyst has a thermal conductivity of at least about 90W/m-K at 300K.

69. As in claimThe process of claim 53, wherein the dehydrogenation catalyst has a mass of about 10m as measured according to the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

70. A process as set forth in claim 69, wherein the dehydrogenation catalyst has a mass of about 25m as measured by the Brunauer-Emmett-Teller method²G to about 100m²Surface area in g.

71. A process as set forth in claim 70, wherein the dehydrogenation catalyst has a mass of about 30m as measured by the Brunauer-Emmett-Teller method²G to about 80m²Surface area in g.

72. A process as set forth in claim 53 wherein said dehydrogenation catalyst comprises at least about 10% by weight copper.

73. The process of claim 72, wherein said dehydrogenation catalyst comprises from about 10% to about 90% by weight copper.

74. A process as set forth in claim 53, wherein the metal supporting structure of the dehydrogenation catalyst comprises a metal sponge.

75. A process as set forth in claim 74, wherein the metal sponge supporting structure of the dehydrogenation catalyst has a thickness of at least about 10m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

76. A process as set forth in claim 75, wherein the metal sponge supporting structure of the dehydrogenation catalyst has a thickness of at least about 50m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

77. A process as set forth in claim 76, wherein the metal sponge supporting structure of the dehydrogenation catalyst has a thickness of at least about 70m as measured by the Brunauer-Emmett-Teller method²Surface area in g.

78. A process as set forth in claim 74, wherein the metal sponge supporting structure comprises nickel.

79. A process as set forth in claim 78, wherein the metal sponge supporting structure comprises at least about 50% by weight nickel.

80. A process as set forth in claim 79, wherein the metal sponge supporting structure comprises at least about 85% by weight nickel.

81. The process of claim 78, wherein said dehydrogenation catalyst comprises from about 10% to about 80% by weight copper.

82. The process of claim 81, wherein said dehydrogenation catalyst comprises from about 20% to about 45% by weight copper.

83. A process as set forth in claim 81, wherein the dehydrogenation catalyst comprises from about 5 to about 100 μmol/g nickel at the surface of said catalyst.

84. A process as set forth in claim 83 wherein the dehydrogenation catalyst comprises from about 10 to about 80 μmol/g nickel at the surface of said catalyst.

85. A process as set forth in claim 84 wherein the dehydrogenation catalyst comprises from about 15 to about 75 μmol/g nickel at the surface of said catalyst.

86. A process as set forth in claim 53, wherein the dehydrogenation catalyst is incorporated onto the surface of the pellet or monolith substrate.

87. A process as set forth in claim 39, wherein the dehydrogenation catalyst comprises a nickel sponge supporting structure.