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WO2003051493A2 - Catalyseur d'oxydation a base de cuivre dope par un metal du groupe platine et procedes de biorestauration du monoxyde de carbone - Google Patents

Catalyseur d'oxydation a base de cuivre dope par un metal du groupe platine et procedes de biorestauration du monoxyde de carbone Download PDF

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Publication number
WO2003051493A2
WO2003051493A2 PCT/US2002/035545 US0235545W WO03051493A2 WO 2003051493 A2 WO2003051493 A2 WO 2003051493A2 US 0235545 W US0235545 W US 0235545W WO 03051493 A2 WO03051493 A2 WO 03051493A2
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Prior art keywords
oxidation catalyst
preferential oxidation
platinum
support
oxide
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WO2003051493A3 (fr
Inventor
Lawrence Shore
Wolfang F. Ruettinger
Robert J. Farrauto
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BASF Catalysts LLC
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Engelhard Corp
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Priority claimed from US10/035,575 external-priority patent/US20020131915A1/en
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Priority to AU2002364694A priority Critical patent/AU2002364694A1/en
Publication of WO2003051493A2 publication Critical patent/WO2003051493A2/fr
Publication of WO2003051493A3 publication Critical patent/WO2003051493A3/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/894—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0248—Coatings comprising impregnated particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
    • C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
    • C01B3/58—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction
    • C01B3/583—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction the reaction being the selective oxidation of carbon monoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0205—Impregnation in several steps
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0283—Processes for making hydrogen or synthesis gas containing a CO-shift step, i.e. a water gas shift step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0435—Catalytic purification
    • C01B2203/044—Selective oxidation of carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/047—Composition of the impurity the impurity being carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/06—Integration with other chemical processes
    • C01B2203/066—Integration with other chemical processes with fuel cells
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/14—Details of the flowsheet
    • C01B2203/146—At least two purification steps in series
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
    • H01M8/0668—Removal of carbon monoxide or carbon dioxide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to preferential oxidation catalysts and methods for the selective oxidation of carbon monoxide in gas streams containing high concentrations of hydrogen. More particularly, the invention relates to copper catalysts that contain low levels of platinum group metals that stabilize the catalyst composition against deactivation that typically occurs in copper-based catalysts at lower temperatures e.g., below about 140 °C.
  • the catalysts and methods of the invention are useful, for example, for removing carbon monoxide in hydrogen feed streams supplied to fuel cells, particularly to proton exchange membrane (PEM) fuel cells.
  • PEM proton exchange membrane
  • Fuel cells directly convert chemical energy into electricity thereby eliminating the mechanical process steps that limit thermodynamic efficiency, and have been proposed as a power source for many applications.
  • the fuel cell can be two to three times as efficient as the internal combustion engine with little, if any, emission of primary pollutants such as carbon monoxide, hydrocarbons and nitric oxides.
  • Fuel cell-powered vehicles which reform hydrocarbons to power the fuel cell generate less carbon dioxide (green house gas) and have enhanced fuel efficiency.
  • Fuel cell processors (also known as fuel cell reformers) supply a hydrogen- containing gas stream to the fuel cell.
  • Fuel cell processors include reactors that steam reform hydrocarbon feedstocks (e.g., natural gas, LPG) and hydrocarbon derivatives (e.g., alcohols) to produce a process stream enriched in hydrogen.
  • hydrocarbon feedstocks e.g., natural gas, LPG
  • hydrocarbon derivatives e.g., alcohols
  • Other by-products from the steam reforming of hydrocarbon include carbon monoxide and carbon dioxide.
  • Fuel cell processors further include shift reactors where the hydrogen content of the process stream is further enriched by reaction of carbon monoxide in the water-gas shift reaction:
  • Fuel cells including PEM fuel cells [also called solid polymer electrolyte or (SPE) fuel cells], generate electrical power in a chemical reaction between a reducing agent (hydrogen) and an oxidizing agent (oxygen) which are fed to the fuel cells.
  • a PEM fuel cell includes an anode and a cathode separated by a membrane which is usually an ion exchange resin membrane.
  • the anode and cathode electrodes are typically constructed from finely divided carbon particles, catalytic particles supported on the carbon particles and proton conductive resin intermingled with the catalytic and carbon particles.
  • hydrogen gas is electrolytically oxidized to hydrogen ions at the anode composed of platinum reaction catalysts deposited on a conductive carbon electrode.
  • the protons pass through the ion exchange resin membrane, which can be a fluoropolymer of sulfonic acid called a proton exchange membrane.
  • H 2 O is produced when protons then combine with oxygen that has been electrolytically reduced at the cathode.
  • the electrons flow through an external circuit in this process to do work, creating an electrical potential across the electrodes. Examples of membrane electrode assemblies and fuel cells are described in United States Patent No. 5,272,017.
  • the platinum electrodes at the anode are extremely sensitive to carbon monoxide in the hydrogen feed stream supplied to the fuel cell. Even levels below 100 ppm of carbon monoxide can cause deterioration of the platinum and consequently, adversely affect fuel cell performance. It is therefore desirable to reduce the levels of carbon monoxide in the hydrogen feed stream supplied to the fuel cell to as low a level as practical.
  • the level of carbon monoxide in the hydrogen feed stream ultimately supplied to the fuel cell is below 100 ppm, more preferably below 10 ppm. Levels of carbon monoxide as low as these are difficult to achieve by using the water-gas shift reactor alone, and so additional carbon monoxide purifying measures are typically used.
  • One well-known method utilized to lower the levels of carbon monoxide in hydrogen feed streams includes treatment with "preferential oxidation catalysts” (also known as “Prox” catalysts). These catalysts selectively oxidize residual carbon monoxide in hydrogen gas streams according to the following reaction:
  • the preferential oxidation process be as selective as possible for the oxidation of carbon monoxide.
  • Some of the factors that influence the selectivity of the oxidation process include the composition of the input gas stream used in the process, the temperature of the reaction, the space velocity of the input gas stream and the composition of the preferential oxidation catalyst.
  • An alternative preferential oxidation catalyst is a catalyst containing ruthenium as a catalytic agent, e.g., ruthenium on an alumina support.
  • the ruthenium-based catalyst does not catalyze the reverse water-gas shift reaction, and hydrogen feed streams with levels of carbon monoxide below 10 ppm can be achieved.
  • the temperatures at which the selective oxidation processes using a ruthenium-based catalyst are operated, however, are also favorable for the methanation reaction that occurs with carbon monoxide as shown below
  • a copper/cerium oxide catalyst composition has been described in WO 01/60738 to catalyze the selective oxidation of carbon monoxide in hydrogen feed streams.
  • the performance characteristics of the catalyst are not described in the presence of steam in this publication, however, a paper [Avgouropoulis et al. Catalysis Letters 2001, 73, 33] described the effect of 10% steam on the performance of these catalysts.
  • a 20-40 °C increase in operating temperature was needed under dry conditions. Exposure to high steam conditions are an intrinsic part of fuel cell processor operation.
  • these copper-based catalyst typically operate at higher temperatures however, which typically result in lower selectivity.
  • the selectivity of the reduction can be improved by decreasing the reaction temperature, however, the catalyst is prone to deactivation when the temperature drops below about 140 °C.
  • Such temperature drops are common in fuel cell applications since power demands for fuel cells vary considerably depending on the application.
  • Preferential oxidation catalysts for incorporation into fuel cell processors are therefore preferably designed to withstand such temperature drops that are characteristic of transient operation.
  • the invention relates to a preferential oxidation catalyst for the oxidation of carbon monoxide to carbon dioxide in the presence of excess hydrogen.
  • the preferential oxidation catalyst has at least 50 wt.% of an oxide support that contains activated alumina, zirconia, titania, silica, zeolites and combinations thereof.
  • Preferred supports include activated alumina.
  • Dispersed on the oxide support is copper or an oxide thereof, a platinum group metal and a reducible metal oxide.
  • the platinum group metal is selected from the group consisting of platinum, palladium, rhodium, osmium, iridium, ruthenium and combinations thereof; and is preferably in a concentration range of 0.01 to 0.5 wt.% of the catalyst composition.
  • a preferred platinum group metal is platinum.
  • the reducible metal oxide is preferably selected from the group consisting of oxides of chromium, vanadium, molybdenum, cerium, praseodymium, neodymium, titanium, nickel, manganese, cobalt, and combinations thereof.
  • Preferred preferential oxidation catalysts contain cerium oxide in the composition.
  • the preferential oxidation catalysts preferably contain at least 10 wt.% of the reducible metal oxide.
  • the preferential oxidation catalyst has at least 65 wt.% of an alumina support. Dispersed on the support are: 5 to 14 wt.% of copper or an oxide thereof, 0.01 to 0.5 wt.% of platinum, and 10 to 25 wt.% of cerium oxide.
  • the catalyst is in the form of support particles having a mesh size of 12 or greater, and a BET surface area of 10 m 2 /g or greater.
  • the support particles preferably are durable and possess high mechanical strength.
  • the preferential oxidation catalyst is in the form of a washcoat composition deposited on a monolith substrate.
  • the catalyst can also take the form of extrudates or tablets.
  • the invention in another aspect, relates to a preferential oxidation catalyst having a cerium oxide support on which is dispersed copper or an oxide thereof; and 0.2 wt.% or more of a platinum group metal.
  • the cerium oxide support is in the form of a washcoat composition deposited on a monolith substrate, although other forms such as tablets and extrudates can be used.
  • the platinum group metal is selected from the group consisting of platinum, palladium, rhodium, osmium, iridium, ruthenium and combinations thereof.
  • Preferred preferential oxidation catalysts contain platinum.
  • a particularly preferred embodiment of this copper-based, cerium oxide-supported preferential oxidation catalyst has 5 to 14 wt.% of copper or an oxide thereof dispersed on the cerium oxide support; and 0.2 to 5 wt. % platinum dispersed on the cerium oxide support.
  • the invention relates to a process for selectively oxidizing carbon monoxide from an input gas stream containing carbon monoxide, oxygen and hydrogen. The process includes the step of contacting the input gas stream with a preferential oxidation catalyst.
  • the input gas stream composition can additionally include ⁇ steam.
  • the process is typically conducted using O 2 /CO ratio in the input gas stream of about 0.25 to 5 at a temperature of about 80 to 160 °C.
  • the preferential oxidation catalyst used in the process contains an oxide support on which is dispersed copper or an oxide thereof, a platinum group metal, and a reducible metal oxide.
  • Preferred oxide supports, platinum group metals, reducible metal oxides, and preferred concentrations are as described above.
  • the catalyst used in the process is preferably in the form of particles having a mesh size of 12 or greater, and a BET surface area of 10 m /g or greater, having high mechanical strength.
  • the process is conducted with the preferential oxidation catalyst containing a cerium oxide support, on which is dispersed copper or an oxide thereof and 0.2 wt.% or more of a platinum group metal.
  • the catalyst composition is preferably in the form of a washcoat composition deposited on a monolith substrate.
  • an input gas stream is contacted with an article containing two preferential oxidation catalysts.
  • the input gas stream is first contacted with an upstream catalyst to give a first outlet gas stream.
  • the first outlet gas stream contains less than 1000 ppm of carbon monoxide.
  • the first outlet gas stream is then contacted with a downstream catalyst to give a second outlet gas stream.
  • the second outlet gas stream contains less than 10 ppm of carbon monoxide.
  • the upstream catalyst of the article can be any preferential oxidation that provides carbon monoxide levels of less than 1000 ppm in the first outlet gas stream.
  • the downstream catalyst contains an oxide support (e.g., activated alumina) on which is dispersed copper or an oxide thereof, a platinum group metal (e.g., platinum), and a reducible metal oxide (e.g., cerium oxide).
  • the downstream catalyst contains a cerium oxide support, on which is dispersed copper or an oxide thereof and 0.2 wt.% or more of a platinum group metal.
  • the invention relates to an apparatus for supplying hydrogen to a PEM fuel cell that incorporate the preferential oxidation catalysts of the invention.
  • the apparatus has a hydrocarbon reformer reactor, a water-gas shift reactor, and a preferential oxidation reactor.
  • the hydrocarbon reformer reactor is upstream and in train with the water-gas shift reactor, and the preferential oxidation catalyst is downstream and in train with the water-gas shift reactor.
  • the preferential oxidation reactor contains the preferential oxidation catalysts with oxide supports on which are dispersed copper or an oxide thereof, a platinum group metal, and a reducible metal oxide.
  • the preferential oxidation reactor contains the preferential oxidation catalysts with a cerium oxide support, on which is dispersed copper or an oxide thereof and a platinum group metal.
  • Figure 1 is a depiction of one embodiment of fuel processor unit for supplying hydrogen to a fuel cell.
  • Figure 2 is a graphic representation of test results for the reverse water-gas shift properties of an embodiment of Catalyst B.
  • Figure 3 is a graphic representation of test results obtained for the carbon monoxide conversion percentage with temperature for a conventional copper-based catalyst.
  • activated alumina means a high BET surface area alumina, for example greater than
  • Catalyst A refers to a catalyst of the invention that includes a refractory inorganic oxide support (e.g., alumina), a copper catalytic agent, a reducible metal oxide (e.g., cerium oxide) and one or more platinum group metals.
  • Catalyst B refers to a catalyst of the invention that includes a cerium oxide support, a copper catalytic agent and one or more platinum group metals
  • Catalytically effective amount means that the amount of material present is sufficient to affect the rate of the carbon monoxide oxidation in the sample being treated
  • cerium oxide includes all oxides of cerium including ceria (Ce0 2 ).
  • cerium oxide support refers to a particulate support material wherein cerium oxide is present, preferably in at least a concentration of 50 wt.% of the total catalyst weight.
  • cerium oxide including for example, other rare earth oxides (e.g., oxides of lanthanum, praseodymium, neodymium), zirconium oxide and gallium oxide.
  • rare earth oxides e.g., oxides of lanthanum, praseodymium, neodymium
  • zirconium oxide zirconium oxide and gallium oxide.
  • copper-based catalyst refers to a catalyst that includes a copper catalytic agent.
  • high heat capacity support means support materials with a heat capacity that is approximately equal to or, preferably, greater than that of the reducible metal oxide in the catalyst
  • high surface area support means support materials with a BET surface area that is approximately greater than 10 m 2 /g, preferably greater than 150 m 2 /g.
  • incipient wetness impregnation means the impregnation of the catalyst support with a volume of metal salt solution substantially equal to the pore volume of the support material
  • inlet temperature shall mean the temperature of the hydrogen, water, and carbon monoxide stream, test gas, fluid sample or fluid stream being treated immediately prior to initial contact of the hydrogen stream, test gas, fluid sample or fluid stream with a catalyst composition
  • input gas stream means a gas stream prior to passing through a catalytic region or prior to initial contact with a catalyst composition.
  • “in the presence of excess hydrogen” shall mean in the presence of at least 10% by volume hydrogen, “percent by volume” refers to the amount of a particular gas component of a gas stream, unless otherwise indicated, means the mole percent of the gas component of the gas stream as expressed as a volume percent. "wt.%.” or “percent by weight”, means weight percent based on the weight of an analyte as a percentage of the total catalyst weight, including the support and any material impregnated therein, including without limitation the copper catalytic agent and any metal oxide material impregnated therein. The calculation does not include the monolith substrate in embodiments where the catalyst is in the form of a washcoat composition deposited on a monolith substrate.
  • “selectivity” refers to the preferential oxidation of carbon monoxide in favor of hydrogen
  • “supports” or “catalyst support” refer to particulate materials that are part of the catalyst composition used to maintain the surface area of the catalyst.
  • Supports include oxide supports selected from the group consisting of activated alumina, zirconia, titania, silica, zeolites and combinations thereof for Catalyst A.
  • Cerium oxide serves as an effective support for Catalyst B.
  • VHSV means volume hourly space velocity; that is, the flow of a reactant gas in liter per hour per liter of catalyst volume at standard temperature and pressure. In embodiments of the invention that include a monolith, the determination includes the total volume of monolith substrate.
  • WHSV means weight hourly space velocity; that is the flow of a reactant gas in liter per hour per kilogram of catalyst.
  • Applicants have found copper-based catalysts that selectively catalyze the oxidation of carbon monoxide in preference to the oxidation of hydrogen in a gas stream.
  • the catalysts of the invention maintain their catalytic oxidation activity at lower temperatures, e.g., below 140 °C, unlike conventional copper-based catalysts.
  • the catalysts also achieve higher carbon monoxide conversions at lower temperatures than conventional copper-based catalysts, widening the effective temperature window where effective selective oxidation of carbon monoxide can be conducted.
  • the activation temperatures of the catalysts of the invention are lower than conventional copper-based catalysts.
  • the carbon monoxide content of hydrogen containing gas streams can be lowered, using the methods of the invention, to achieve levels below 100 ppm, and in some cases, below 10 ppm.
  • the catalysts of the invention may be used in any application where it is desirable to remove carbon monoxide from a hydrogen gas stream, their incorporation into fuel processors that supply hydrogen to a fuel cell provides significant advantages.
  • the catalysts of the invention successfully operate as effective preferential oxidation catalysts under conditions typically utilized in fuel processors.
  • the copper-based catalysts of the invention also remain active after temperature drops. This property is desirable for the transient operation of processors that would be used, for example, in residential or vehicular fuel cell applications, where power demands vary considerably.
  • platinum group metals can serve as effective preferential oxidation catalytic agents themselves, their inclusion in the catalysts compositions is believed to serve primarily as a stabilizing species to the copper catalytic agents.
  • the relatively low concentrations of the platinum group metal components in the catalysts of the invention as compared to the higher concentrations utilized in platinum metal-based preferential oxidation catalysts reflect this function.
  • the utilization of a base metal, copper, in the catalysts of the invention offers significant cost advantages over platinum-based preferential oxidation catalysts.
  • the catalysts of the invention include a catalyst support, copper or an oxide thereof, as a catalytic agent, and one or more platinum group metals.
  • the catalyst can be in any form, including tablets, extrudates, washcoat compositions deposited on monolith substrates and high-strength, high heat capacity particulate catalysts.
  • the invention relates to a preferential oxidation catalyst that includes a refractory inorganic oxide support (e.g., alumina), a copper catalytic agent, a reducible metal oxide (e.g., cerium oxide) and one or more platinum group metals.
  • a refractory inorganic oxide support e.g., alumina
  • copper catalytic agent e.g., copper catalytic agent
  • a reducible metal oxide e.g., cerium oxide
  • platinum group metals platinum group metals
  • the invention relates to a preferential oxidation catalyst that has a cerium oxide support, a copper catalytic agent and one or more platinum group metals.
  • this catalyst will be referred to herein as "Catalyst B”.
  • Catalyst A contains a refractory inorganic oxide support (e.g., alumina). Dispersed on the support are a copper catalytic agent, a reducible metal oxide (e.g., cerium oxide) and one or more platinum group metals.
  • the catalyst can be in any form including extrudates, tablets, washcoat compositions deposited on monolith substrates and high mechanical strength, high heat capacity, particulate catalysts. Preferred forms of the catalyst are as high strength, high-heat capacity particulate catalysts.
  • the copper catalytic agent can be in the form of copper (II) oxide (CuO), copper (I) oxide (Cu 2 O) or as metallic copper depending on the conditions that the catalyst is exposed to.
  • the copper is generally dispersed on the inorganic oxide support by contacting the support with a water-soluble or water- dispersible salt of copper for sufficient time to impregnate the support, followed by a drying step.
  • the support material containing the copper is then calcined, preferably at a temperature above about 400 °C.
  • the catalysts of the invention include a platinum group metal as a stabilizing species, which is selected from the group consisting of platinum, palladium, rhodium, iridium and ruthenium.
  • the platinum group metal is platinum, palladium or rhodium, with platinum being particularly preferred.
  • the platinum group metals are typically dispersed on the support by contacting the support with a water-soluble or water-dispersible salt of the platinum group metal for sufficient time to impregnate the support.
  • Non-limiting examples of such platinum group metal salts include nitrates, acetates, alkali-free amine-solubilized platinum hydroxide, palladium and rhodium nitrate.
  • the supported platinum group metal is then calcined to fix it to the support as the metal or as an oxide.
  • the amount of the platinum group metal salts is chosen so that the final concentration of the platinum group metal on the support is about 0.01 to about 0.5 wt.%, more preferably 0.05 wt.% to about 0.25 wt.%.
  • Suitable reducible metal oxides for Catalyst A include the oxides of chromium, vanadium, molybdenum, cerium, praseodymium, neodymium, titanium, nickel, manganese, cobalt , as well as combinations thereof. Typically, there is at least 10 wt.% of the reducible metal oxide in the catalyst composition, with levels of 10 to 25 wt.% being preferred.
  • a preferred reducible metal oxide is cerium oxide. While cerium oxide alone serves as the reducible metal oxide component, in some applications it is desired to include certain composite materials of cerium oxide. These cerium oxide composites additionally contain other rare earth metal oxides component such as oxides of lanthanum, praseodymium, and neodymium. In addition to these rare earth metal oxide composites, other composite materials such as zirconia-cerium oxide, gallium oxide- cerium oxide, titania-cerium oxide are also useful as a reducible metal oxide components in Catalyst A. In both types of composite materials, it is believed that the additional component acts as a stabilizer for the cerium oxide component, although in some cases, the additional component may also serve to promote the selective oxidation reaction. In composites comprising cerium oxide with the additional components, the additional ⁇ :
  • the reducible metal oxide component may comprise up to about 30 wt.% of the reducible metal oxide component of the composition.
  • Inorganic oxide supports for Catalyst A include high surface area, refractory oxide supports. These refractory oxide supports include, for example, activated alumina, zirconia, titania, silica, and zeolites. These supports also include combinations of these inorganic oxides such as stabilized forms of alumina including composites of zirconia, or silica with alumina, for example, alumina-zirconia, silica-alumina, and alumino-silicates.
  • the support is substantially comprised of alumina which preferably includes the members of the gamma or activated alumina family, such as gamma and eta aluminas, and, if present, a minor amount of other refractory oxides, e.g., up to about 20 wt.% of silica, zirconia, and titania.
  • the activated alumina has a specific surface area of at least 10 m 2 /g. More preferably, the activated alumina has a specific surface area of at least 150 m 2 /g.
  • the catalyst supports possess high heat capacity and high mechanical strength. Copper-based water catalysts are prone to extremely rapid temperature rises due to the rapid and exothermic oxidation of carbon monoxide and hydrogen. Such rapid temperature rises can result in a reduced selectivity for carbon monoxide oxidation. The reduced selectivity at higher temperatures in turn results in lower levels of hydrogen in the output stream.
  • reactors are equipped with sophisticated process controls and protocols that can control the temperature rise that occurs upon oxidation. In fuel cell processors in residential or vehicular applications, however, such controls and protocols are impractical to implement. The incorporation into fuel processors of copper-based preferential oxidation catalysts less prone to these temperature rises is therefore desirable.
  • the high mechanical strength of these preferred supports yields a system that is resistant to attrition that may occur due to vibration and other wear mechanisms.
  • the high heat capacity, high mechanical strength catalysts in this embodiment comprise a structurally strong support of any suitable durable high heat capacity material, such as alumina, which is in a particulate form preferably having a longest dimension of about 1/32-inch (0.78 mm) to about 1/2 inch (1.25 cm) in cross section.
  • the support particle is at least 1/16-inch (1.56 mm) in cross section or, in other terms, has a mesh size of 12 (sieve opening of 1.52 mm) or above.
  • the support particle preferably has a mesh size of 12, 11, 10, etc.
  • the catalytic supports in this embodiment are impregnated, with a suitable precursor of a reducible metal oxide, the copper catalytic agent and one or more platinum group metals.
  • Preferred support materials have a heat capacity that is preferably higher than that of the reducible metal oxide. Examples of supports are silica, zeolites, zirconia, titania and alumina. Activated alumina is a particularly preferred support.
  • the high heat capacity particulate support in this preferred embodiment can take the form of any suitable high strength support such as a particle, pellet, extrudate, tablet and the like.
  • the support is preferably in a durable, rigid form.
  • a number of supports that are suitable for preparing the catalysts of the invention and practicing the methods of the invention are readily commercially available. For example, 1 /8-inch diameter alumina particles available from ALCOA as DD-443 (with 327 m 2 /g BET surface area measured as received) can be used to practice the invention.
  • Desirable characteristics for preferred supports include: having a high mechanical strength (resistance to crumbling), being readily available; having the capacity for being impregnated to high loadings with copper catalytic agents, reducible metal oxides and other catalyst additives; and possessing a high heat capacity.
  • Supports with a heat capacity of at least the heat capacity of the reducible metal oxide are preferred.
  • Supports with a heat capacity greater than the heat capacity of the reducible metal oxide are particularly preferred.
  • Catalyst A Due to their low pyrophoricity, high strength particulate catalysts having a high heat capacity supports are preferred forms of Catalyst A. These catalysts can be prepared by first impregnating the particulate support with the reducible metal oxide precursor, followed by drying and calcination. For example, in a preferred preparation calcined 1/8-inch alumina support particles are impregnated in an aqueous solution of cerium nitrate (or any other suitable CeO 2 precursor such as cerium acetate, chloride, etc.). The particles are then dried and calcined at 500 °C in air to prepare the cerium oxide-impregnated alumina support (or "CeO 2 /alumina particles").
  • the support can be impregnated with a precursor of the copper catalytic agent.
  • the CeO 2 /alumina particles are impregnated with an aqueous solution of a water-soluble copper salt, e.g., copper (II) nitrate, at a weakly acidic pH.
  • the particles are then dried and calcined to provide CuO/CeO /alumina particles.
  • the CuO/Ce0 2 /alumina particles are similarly impregnated with a desired concentration of a water-soluble salt of the platinum group metal [e.g., alkali-free amine-solubilized platinum hydroxide] followed by a calcination step to provide the CuO/CeO 2 /alumina particles impregnated with platinum.
  • a water-soluble salt of the platinum group metal e.g., alkali-free amine-solubilized platinum hydroxide
  • the catalyst is in the form of washcoat compositions, extrudates and tablets, the catalyst is preferably formed from powdered supports impregnated with the copper catalytic agent, the platinum group metal and reducible metal oxide.
  • the impregnated, powdered supports can be prepared by incipient wetness impregnation of the oxide support (e.g., activated alumina) with soluble salts of the reducible metal (e.g., cerium).
  • the oxide support e.g., activated alumina
  • soluble salts of the reducible metal e.g., cerium
  • soluble salt forms of the reducible metal such as acetates, halides, nitrates, sulfates and the like can be utilized. This step is followed by drying and calcination steps to fix the reducible metal component as its oxide to the refractory oxide support.
  • the calcined support is then impregnated in analogous fashion with a desired concentration of a water-soluble salt of the copper (e.g., copper (II) nitrate) followed by drying and calcination steps. Finally, the resulting oxide support is impregnated with a desired concentration of a water-soluble salt of the platinum group metal (e.g., platinum nitrate) followed by a calcination step.
  • the calcined, impregnated powdered oxide support containing the copper catalytic agent, the platinum group metal, and reducible metal oxide can then be formed into either an extrudate, tablet, or washcoat composition for deposition on a monolith substrate.
  • the calcined, powdered oxide support containing the copper catalytic agent, the platinum group metal, and reducible metal oxide is typically mixed with a binder and extrudated through a die of the desired shape.
  • Typical useful binders include hydrated forms of alumina (e.g., pseudoboehmite), silica binders, clay binders, zirconia binders and the like.
  • Tablets can be prepared by: (1) combining the calcined, powdered oxide support with a binder; (2) shaping the combined powder and binder into the desired shape which could include tablets, pellets, beads, cylinders or hollow cylinders; and (3) calcining the shaped catalyst.
  • Washcoat compositions of the catalyst for deposition on monolith substrates are prepared using methods known in the art.
  • the impregnated oxide support is ball milled as a suspension using sufficient water to prepare a slurry of a desired concentration.
  • concentration of the solids in the washcoat slurry can be used as a method to control the thickness of the catalyst coating ultimately deposited on the monolith substrate. For example, increasing the weight percentage of solids in the aqueous slurry will result in a thicker catalytic coat.
  • binders are optionally included in the slurries to improve adherence of the washcoat to the monolith substrate walls.
  • washcoat slurries are deposited on the monolith substrate by methods well- known to those of ordinary skill.
  • a layer of the supported copper catalyst can be prepared by dipping the substrate in a reservoir containing a sufficient volume of the slurry so that the substrate is fully immersed.
  • the coated substrate can be subsequently dried and calcined.
  • the washcoat catalyst compositions of the invention are disposed on monolith substrates to form coated monolith substrates.
  • the monolith substrate is preferably of the type with one or more monolithic bodies having a plurality of finely divided gas flow passages (channels) extending therethrough.
  • the monolith substrate is of the type having a plurality of fine, parallel gas flow passages extending across the longitudinal axis of the substrate from an inlet or an outlet face, so that the channels are open to fluid flow therethrough (often referred to as a "honeycomb substrate").
  • the passages which are essentially straight from the inlet and outlet of the substrates, are defined by walls on which the catalyst composition can be coated in washcoat compositions so that the gases flowing through the passages contact the catalyst material.
  • Monolith substrates are commercially available in various sizes and configurations.
  • the flow passages of the monolithic substrate are thin-walled channels which can be of any suitable cross-sectional shape and size such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular.
  • Such monolithic substrates may contain up to about 700 or more flow channels ("cells") per square inch of cross section, although far fewer may be used.
  • the substrate can have from about 60 to 600, more usually from about 200 to 400, cells per square inch (“cpsi").
  • the monolith substrate can be made from a variety of materials, including metal or ceramic monoliths.
  • the monolith substrate can be made from a ceramic porous material composed of one or more metal oxides, e.g., alumina, alumina- silica, alumina-silica-titania, mullite, cordierite, zirconia, zirconia-ceria, zirconia-spinel, zirconia-mullite, silicon-carbide, and like.
  • Ceramic monoliths can include those made of: zirconium, barium titanate, porcelain, thorium oxide, magnesium oxide, steatite, boron or silicon carbonates, cordierite-alpha alumina, silicon nitride, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, alpha alumina and aluminosilicates.
  • a commercially available material for use as the substrate for the present invention is cordierite, which is an alumina-magnesia-silica material.
  • the metallic monolith substrate can be a honeycomb substrate made of a refractory metal such as a stainless steel or other suitable iron-based corrosion resistant alloys (e.g., iron-chromium alloy).
  • Metal monoliths can be produced, for example, from alloys of chromium, aluminum and cobalt, such as those marketed under the trademark KANTHAL, or those produced from alloys of iron, chromium, aluminum and yttrium, marketed under the trademark of FECRALLOY.
  • the metal can also be carbon steel or simple cast iron.
  • Monolith substrates are typically fabricated from such materials by placing a flat and a corrugated metal sheet one over the other and rolling the stacked sheets into a tubular configuration about an axis parallel to the configurations, to provide a cylindrical-shaped body having a plurality of fine, parallel gas flow passages, which can range, typically, from about 200 to about 1,200 per square inch of face area.
  • Heat exchangers which are typically formed from metallic materials, can also be used as the monolith structures.
  • the monolith substrate can be made of a ceramic or metal foam.
  • Monolith substrates in the form of foams are well known in the prior art, e.g., see US Patent 3,111,396 and SAE Technical Paper 971032, entitled “A New Catalyst Support Structure For Automotive Catalytic Converters” (February, 1997).
  • Catalyst B contains a copper catalytic agent and one or more platinum group metals dispersed on a cerium oxide support
  • the catalyst can be formed as extrudates, tablets and washcoat compositions deposited on monolith substrates.
  • Preferred forms of Catalyst B are as washcoat compositions deposited on monolith substrates.
  • the copper is preferably dispersed on the inorganic oxide support by contacting the cerium oxide support with a water-soluble or water-dispersible salt of copper for sufficient time to impregnate the cerium oxide, followed by a drying step.
  • the support material containing the copper can then be calcined, preferably at a temperature above about 400 °C.
  • Catalyst B of the invention includes a platinum group metal, which is selected from the group consisting of platinum, palladium, rhodium, iridium and ruthenium.
  • the platinum group metal is platinum, palladium or rhodium, with platinum being particularly preferred.
  • the platinum group metals are typically dispersed on the cerium oxide support by impregnation followed by calcination.
  • the amount of the platinum group metal salts is chosen so that the final concentration of the platinum group metal on the support is about 0.2 wt.% to about 5 wt.%, although lower concentrations of platinum group metals, e.g., 0.2 to 1 wt.%, are more preferred for reduced material costs.
  • Cerium oxide serves as the support of Catalyst B. While cerium oxide alone can be used for the support, in certain applications it may be desirable to include additives to the cerium oxide that stabilize the support. For example, certain composite materials of cerium oxide that additionally contain other rare earth metal oxides component such as oxides of lanthanum, praseodymium, and neodymium are useful.
  • certain composite materials such as zirconia-cerium oxide, gallium oxide-cerium oxide, titania-cerium oxide are also useful as composite cerium-oxide support materials for Catalyst B.
  • the additional component acts as a stabilizer for the cerium oxide support, although in some cases, the additional component may also serve to promote the carbon monoxide oxidation.
  • the stabilizing component may comprise up to about 30 wt.%, but preferably less than 25 wt.% of the cerium oxide support of the composition.
  • Washcoat compositions, extrudates and tablets of Catalyst B are preferably formed from powdered cerium oxide impregnated with the copper catalytic agent and platinum group metal.
  • Catalyst B is prepared by impregnating cerium oxide powder with a solution of a water-soluble salt of copper, e.g., copper (II) nitrate, followed by drying at, for example 120 °C, and calcination at, for example, 500 °C.
  • the impregnation is accomplished using incipient wetness impregnation wherein minimal volumes of copper salt solutions are employed to soak the cerium oxide support.
  • the resulting cerium oxide support is then impregnated with a water-soluble salt of a platinum group metal, e.g., platinum nitrate.
  • a drying and a calcination step follow to provide powdered Catalyst B.
  • the powdered Catalyst B composition can be formed into extrudates, tablets and washcoat compositions using the methods described above for forming the Catalyst A compositions.
  • catalyst B can also be prepared utilizing an aqueous solution containing a mixture of a water-soluble cerium salt, e.g., cerium nitrate, and a water-soluble copper salt, e.g., copper (II) nitrate.
  • a base e.g., sodium carbonate
  • the solution is stirred during the precipitation step.
  • the resulting coprecipitate is collected, dried and calcined to provide mixed metal oxide material comprising copper oxide and cerium oxide. Impregnation of the mixed metal oxide material with a platinum group salt followed by a calcining of the material can be used to incorporate the platinum group metal component into the Catalyst B composition.
  • the invention also relates to processes for using the catalysts of the invention, i.e., Catalysts A and B.
  • the catalysts of the invention are used as preferential oxidation catalysts in processes for the selective oxidation of carbon monoxide in a hydrogen gas stream.
  • the catalysts of the invention can be incorporated in a reactor that is charged with an input gas stream containing hydrogen and carbon monoxide to produce an output hydrogen stream that contains substantially lower levels of carbon monoxide. For example, levels below 10 ppm in the output hydrogen gas stream can be achieved using the selective oxidation processes of the invention.
  • the preferential oxidation catalysts of the invention are reduced (activated) prior to their use in the selective oxidation reaction.
  • the process gas itself containing carbon monoxide and hydrogen, serve as the reducing gas stream for the catalysts of the invention.
  • the composition of the input gas stream for the process can vary depending on the source of the hydrogen gas stream.
  • the input gas stream for the process could include carbon dioxide, steam, and nitrogen in addition to hydrogen and carbon monoxide. Minor amounts of hydrocarbon may also be present.
  • the selective oxidation processes of the invention can accommodate a range of carbon monoxide concentrations in the input hydrogen stream, depending on the output CO concentration requirements of a particular application. In fuel cell applications the concentration of CO in the input hydrogen stream is generally from 0.05 to 3% by volume.
  • the process of the invention can conducted by staging into two or more catalyst beds.
  • the input gas stream containing hydrogen and a level of carbon monoxide would contact the first catalyst bed to produce an intermediate gas stream that would contain a reduced level of carbon monoxide.
  • the intermediate gas stream would then contact a second catalyst bed to produce an outlet gas stream containing still lower levels of carbon monoxide. Additional catalyst stages could be provided until the desired carbon monoxide threshold is achieved.
  • Multi-bed embodiments of the process are described in the Examples section.
  • the input gas streams typically contain at least 10% by volume of hydrogen , and more typically from about 40 to 70% on a dry basis in addition to the carbon monoxide.
  • the molar ratio of oxygen to carbon monoxide in the input gas stream (O 2 /CO ratio) to the process can be adjusted to optimize carbon monoxide conversion and the 5 selectivity of the oxidation reaction.
  • O 2 /CO ratio molar ratio of oxygen to carbon monoxide in the input gas stream
  • reaction temperature of the inventive, selective oxidation process can be adjusted to optimize the reaction rate, carbon monoxide conversion and selectivity. For instance, lower reaction temperatures favor increased selectivity for carbon monoxide oxidation for a gas compositions at the same space velocity and O 2 /CO ratio. Higher
  • preferred operating temperatures for the process of the invention are from about 80 to 160 °C, with a more preferred range of from about 80 to 130 °C.
  • Reaction zone pressure is preferably maintained below the dew point pressure of
  • reaction zone pressures can be used such as from atmospheric up to about 500 psig.
  • the selective oxidation process is carried out in a continuous mode with the reactants being passed over the catalyst contained in one or more reaction zones.
  • the basis of dry gas under standard conditions are particularly suitable for most fuel cell operations.
  • the catalysts are in the form of washcoat compositions deposited on monolith substrates, space velocities of up to 100,000 hr "1 VHSV can be accommodated. Preferred operating ranges wherein the catalyst compositions are deposited on a monolith substrate are 5 to 30,000 hr "1 .
  • the preferential oxidation catalysts of the invention can be used in any application where it is desired to remove carbon monoxide from a hydrogen-containing gas stream, a particularly useful application is in apparatus such as fuel processors that supply hydrogen to fuel cells.
  • These processors typically comprise a series of reactors that convert hydrocarbon fuels (e.g., natural gas, gasoline, fuel oil, liquid petroleum gas, and the like) into hydrogen fuel.
  • the conversions that take place in the reactors typically include reforming reactions and water-gas shift reactions to produce hydrogen.
  • Other reactors and trapping devices can also be included in the apparatus that reduce unwanted components in the hydrogen feed streams (e.g., sulfur components), that are ultimately supplied to the fuel cell.
  • Preferential oxidation reactors where the selective oxidation of carbon monoxide is conducted, is typically performed as a finishing step to polish the hydrogen feed stream of residual carbon monoxide.
  • the hydrocarbon reformer reactor (2) converts hydrocarbons (e.g., methane) and steam into hydrogen, carbon monoxide, and carbon dioxide.
  • hydrocarbons e.g., methane
  • steam e.g., hydrogen
  • carbon monoxide e.g., hydrogen
  • carbon dioxide e.g., hydrogen
  • methane methane
  • the hydrocarbon, methane is converted by the two reactions below:
  • Example 1 Preparation of a Copper Ceria-supported Preferential Oxidation Catalyst Impregnated with 0.5 wt.% Pt. (Exemplifies Preparation of Catalyst B deposited on a Monolith Substrate, Catalyst B B2 and C) 205 g of cerium oxide powder (HSA-15 cerium oxide available from Rhodia,
  • the intermediate powder was then impregnated with an aqueous solution of alkali-free amine-solubilized platinum hydroxide containing 1.08 g of platinum. After 1 hour, acetic acid was added to immobilize the platinum on the cerium oxide support. The resulting material was calcined using the two step procedure described above to yield cerium oxide support impregnated with 8 wt.% copper oxide and 0.5 wt.% platinum. This composition is used to prepare Catalyst B 1.
  • a second portion of the intermediate cerium oxide powder (281 g) impregnated with 8 wt.% copper oxide was prepared as described above. This portion was impregnated with an aqueous solution that contained 0.70 g of platinum in the amine- solubilized platinum hydroxide salt solution, treated with acetic acid (15.15 g), and calcined using the two step calcination procedure to provide cerium oxide powder impregnated with 8 wt.% copper oxide and 0.25 wt.% platinum. This composition is used to prepare Catalyst B2.
  • the monolith substrate coated with the catalyst composition containing 0.5 wt.% Pt is Catalyst Bl.
  • the monolith substrate coated with the catalyst composition containing 0.25 wt.% Pt is Catalyst B2.
  • the monolith substrate coated with the catalyst composition without any platinum metal is Catalyst C.
  • Example 2 Determination of CO Conversion using Catalyst Bl (Single Bed)
  • Catalyst B 1 of Example 1 was tested for its carbon monoxide conversion and selectivity when exposed to a test gas composition that modeled a reformate gas stream.
  • the test gas had a dry gas composition of 0.3% CO, 15% CO 2 , 50% H 2 and the balance was N 2 . 25% steam was added as a diluent. Air was added as a source of oxygen.
  • the catalyst was placed in a quartz tube reactor, exposed to the test gas, and oxidation began at the minimum temperature measured, 90 °C. The space velocity of the test gas composition was 15k/hr.
  • the inlet temperature and the O 2 /CO ratio was adjusted to yield a product gas stable with respect to CO concentration.
  • the catalyst reached at an inlet temperature of 140 °C and an O 2 /CO ratio of 1.5.
  • the product gas contained 550 ppm of CO, which is equivalent to a CO conversion of 82%. 27% of the added O reacted with the CO.
  • Example 3 Determination of CO Conversion from an Input gas Stream Containing 1.5% CO using the Catalyst of Catalyst Bl (Two Sequential Beds)
  • the temperature of the first bed was 125 °C, while the temperature of the second catalyst bed was 128 °C.
  • the test gas composition in this example contained 1.5 % CO, 15% C0 2 , 50% H 2 and the balance was N 2 . 25% steam was added as a diluent. Air was added as a source of oxygen.
  • the monolith space velocity of the gas stream was 15k/hr over the first catalyst bed and 30k/hr over the second catalyst bed.
  • the O 2 /CO ratio of the initial gas stream was 0.75. After contact with the first catalyst bed, the CO concentration in the intermediate gas stream was 5440 ppm.
  • a preferred aspect of the invention is a reliable low-temperature catalyst for achieving ⁇ 10 ppm of CO in the presence of levels of both hydrogen and carbon monoxide found in fuel cell processors.
  • This experiment was designed to simulate the conditions that a single catalyst bed would be exposed to as a last bed (also referred to as a "polishing bed") in a multi-bed system.
  • a last bed also referred to as a "polishing bed”
  • Experiments were conducted to determine conditions necessary to achieve a final CO concentration in the output gas of ⁇ 10 ppm over a wide range of flow conditions.
  • the inlet gas concentration of CO was kept at 500 ppm.
  • the test gas composition also contained 15% C0 2 , 50% H 2 and the balance was N 2 . 25% steam was added as a diluent. Air was added as a source of oxygen.
  • Table 1 summarizes the effects of temperature, space velocity and O 2 /CO Ratio on the Catalyst B 1 performance as measured by CO detected in the outlet gas stream.
  • the data shows that the catalyst performs optimally at low temperature (115 °C) at low space velocity because of the improved selectivity.
  • space velocity 25 k hr
  • a higher temperature is preferred.
  • O 2 /CO ratio is required to compensate for operating in a regime with lower selectivity for CO oxidation.
  • the extent of the catalytic activity for the reverse water-gas shift was determined using the monolith Catalyst Bl of Example 1.
  • the monolith catalyst was placed in a quartz reactor tube and heated to 200 °C.
  • the catalyst was cooled with a test gas stream containing 50% H 2 , 15% CO 2 , and the balance N 2 at a space velocity of 17 k/hr. 25% steam was added a diluent. No CO or oxygen was added to the test gas stream. Any CO formed was measured in the outlet gas.
  • the data is graphically presented in Figure 2.
  • the catalyst exhibits minimal reverse water-gas shift activity at temperature ranges useful for the preferential oxidation of CO in hydrogen feed streams. For example at 140 °C, only 5 ppm of CO was detected in the output gas stream.
  • Example 6 Comparative Example for Operating Ranges with Conventional Copper- Containing Preferential Oxidation Catalyst (Catalyst C) Using the Catalyst C , containing copper oxide (8 wt.% CuO) on a support of cerium oxide (without any platinum group metal in the composition, prepared in Example 1), the "T 50 " or temperature at which the CO conversion achieves 50% of the total input CO was determined. The T 5 0 was determined using a test gas stream containing 0.6% CO, 15% CO , 50% H 2 , and the balance was N 2 . Steam (25%) was added as a diluent. The determination of the T 50 was conducted using an inlet temperature range of 110-200 °C.
  • the catalyst performance of the Catalyst C as a function of O 2 /CO ratio and temperature was also determined using a test gas composition of 0.5% CO, 15% CO 2 , 50% H 2 , and the balance was nitrogen. Steam (25%) was added as a diluent. The optimal operating temperature was around 150 °C. At this temperature, at an O 2 /CO ratio of 1, about 95% of the CO was oxidized. The catalytic activity, however, dropped to almost nil if the temperature decreased below 135 °C. It is believed that the deactivation is due to the re-oxidation of the catalyst. The CO oxidation activity would only return if the catalyst was reheated in the test gas composition to effect reduction. The example highlights the narrow temperature window of this conventional copper- based catalyst relative to the catalysts of the invention.
  • Example 7 Comparative Example for Operating Ranges with an Iron-Promoted
  • Catalyst B2 (impregnated with 0.25 wt.% Pt) was prepared according to Example 1. The influence of temperature was evaluated first. At an 0 2 /CO ratio of 3, good activity (>90% CO conversion) was observed above 115 °C at 17 k/hr. The catalyst became stable with a CO concentration of 6 ppm in the outlet gas stream at an 0 /CO ratio of 6.7 at 135 °C. At 130 °C with 0 2 /CO ratios of 5.4 and 6.1, some degree of upward shift in the outlet CO concentration was observed, a phenomenon normally associated with catalyst inhibition.
  • Example 2 Another copper-based catalyst was prepared according to Example 1, with 0.125 wt.% platinum impregnated in the catalyst. This is catalyst B3. The experiment with the same test gas composition was repeated with Catalyst B3. At this level, the platinum was basically innocuous, and activation occurred slowly at -140 °C, similar to the data shown in Figure 2.
  • Ce0 2 in an aqueous solution of cerium nitrate (i.e., Ce(N0 3 ) 3 , ; 33.44 g Ce(N0 3 ) 3 dissolved in 55 g water, per 100 g alumina).
  • Ce(N0 3 ) 3 aqueous solution of cerium nitrate
  • the particles were then dried at 120 °C for 8 hours.
  • the sample was then calcined at 500 °C for 2 hours.
  • the ceria/alumina particles were subsequently impregnated (i.e., impregnated at 44%> incipient wetness to obtain 8.25 wt.% CuO) with Cu-nitrate solution (i.e., 26.6 mL of 5M Cu(N0 ) 2 solution in 32 mL deionized water) at a pH of 6, dried at 120 °C for 8 hours and then calcined at 500 °C for 2 hours to prepare catalyst precursor particles (CuO/ceria/alumina particles).
  • Cu-nitrate solution i.e., 26.6 mL of 5M Cu(N0 ) 2 solution in 32 mL deionized water
  • the CuO/ceria alumina particles were then impregnated with alkali-free amine- solubilized platinum hydroxide.
  • 0.357 g of salt solution was diluted with 15.75 mL of water and used to impregnate 51.15 g of precursor particles of water was used to prepare a catalyst containing 0.125 wt.% Pt.
  • the beads were treated with 6.9 mL of acetic acid to immobilize the platinum. After impregnation, the catalysts was dried at 120 °C for 2 hours then calcined at 500 °C for 2 hours.
  • the resulting alumina particles contained 8.25 wt.% CuO, 15 wt.% Ce0 2 , and 0.125 wt.% Pt. This is catalyst Al.
  • Alumina particles of the same material were also impregnated above to obtain a catalyst with a higher Pt concentration, i.e. 0.25 wt.%.
  • This catalyst contained 8.25 wt.% CuO, 15 wt.% Ce0 2 , and 0.25 wt.% Pt. This is catalyst A2.
  • a control catalyst of the same material was prepared without any added platinum.
  • This catalyst contained 8.25 wt.% CuO, 15 wt.% Ce0 2 , and contained no platinum. This is catalyst D.
  • Example 10 Determination of CO Conversion using Catalyst of Example 1 (Exemplifies Catalyst Performance of of High Heat Capacity, High-Mechanical Strength Embodiments of Catalyst A)
  • Catalyst Al catalyst of Example 9 was evaluated using a test gas composition containing 5000 ppm CO, 15% C0 2 , 50% H , and the balance N 2 . Steam (25%) was added as a diluent. The catalyst beads were placed in a quartz tube reactor and exposed to the test gas. Oxidation began at the minimum temperature measured, 90 °C. The catalyst performance was determined as the WHSV was varied from 10-20k L/kg-hr. The inlet temperature and the 0 2 inlet concentration was adjusted to yield a product gas stable with respect to outlet CO concentration . 51 -
  • Table 3 exemplifies the locus of conditions (temperature and space velocity) that are characteristic of Catalyst AT s performaice. For example, at 110 °C and a space velocity of 10k L/kg-hr, >95% conversion of the inlet CO can be achieved.
  • Example 11 Comparative Catalyst Performance of Catalyst A with a Conventional Platinum-based Catalyst (0.5 wt.% Platinum, 0.03 wt.% iron on Alumina)
  • the catalyst performance of a 0.5 wt.% platinum, 0 03 wt.% iron on alumina tablets was evaluated for comparative purposes.
  • a two bed arrangement of the catalyst was used. The first bed operated at 105 °C near 10k L/hr-kg with an inlet gas composition containing 0.5% CO, 0.63% 0 2 , 50% H 2 , 15% C0 2 and the balance was N 2 . Steam (25%) was added as a diluent.
  • the second bed ran at 85 °C and 10k L/hr-kg with 0.3 % 0 2 added.
  • the concentration of C0 2 in the output gas stream from the first bed was -170 ppm, while the C0 2 concentration in the output gas from the second bed was 6-10 ppm.
  • Example 11 The experiment of Example 11 was repeated using a single bed of Catalyst D of
  • Example 9 (containing no platinum), with only 0.5% 0 2 added to the input gas stream.
  • Catalyst D had no activity until 140 °C. The activity increased with temperature, but CO conversion never surpassed 60%, compared with the 97%+ obtained for catalyst Al
  • Example 13 Comparative Catalyst Performance of Catalyst Al versus Conventional Platinum-Based Catalysts at Higher CO Inlet Percentages (i.e., 2 % CO)
  • a two bed catalyst arrangement was tested using 0.5 wt.% platinum, 0.03 wt.% iron on alumina tablets in each bed.
  • Steam (25 %) was added as a diluent.
  • the space velocity for the first bed was I lk L/kg-hr and 13 k L/kg-hr for the second bed.
  • Air was added so that the inlet 0 2 /CO ratio for the first bed was about 0.45.
  • the inlet temperature was increased incrementally from 120 to 160 °C, primarily because of evidence of catalyst inhibition at lower temperatures.
  • the outlet concentration of the first bed was -1.2% CO, equal to a 40% conversion.
  • the 0 2 entering the second bed both from unreacted 0 and freshly injected air, was 0.43%.
  • the CO was further reduced to 4500 ppm in the outlet gas from the second bed at a temperature of 140 °C.
  • the overall CO reduction for the two beds was -77%. Better selectivity was achieved at lower inlet temperatures, but the catalyst passed increasing amounts of CO, a sign that the catalyst performance was decaying.
  • the experiment was repeated using the Catalyst Al of Example 9 in each bed.
  • the test gas composition was the same except that the space velocity was increased for technical reasons.
  • the first catalyst bed was run at 130 °C and the second bed was run at 120 °C.
  • the CO concentration detected in the outlet gas stream from the first bed was 9200 ppm, while the CO concentration detected for the second bed was 1850 ppm.
  • the detected CO concentrations corresponds to a 54% conversion in the first bed and a 91% conversion after two beds. This is a significantly better conversion than achieved using the 0.5 wt.% platinum, 0.03 wt.% iron on alumina catalyst.
  • Catalyst Al was shown to have a tolerant operating window.
  • the first bed was operated at 160 °C to yield an outlet CO concentration from the first bed of 1% CO.
  • This CO conversion of 50% is still better than that achieved by the iron promoted, platinum on alumina catalyst.
  • the result also illustrates the small change in CO selectivity for Catalyst Al as a function of temperature.
  • Catalyst Al was further tested at 120 °C, and the outlet CO concentration decreased to 8900 ppm, or a CO conversion of 55%.
  • the preferential oxidation Catalyst Al containing 0.125 wt.% Pt, shows superior CO conversions, with lower material costs than the 0.5 wt.% platinum, 0.03 wt.% iron on alumina tablets.
  • the temperature window for stable operation of the catalyst of the invention is large.

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Abstract

L'invention concerne des catalyseurs d'oxydation préférés à base de cuivre contenant de faibles concentrations de métaux du groupe platine et procédés faisant intervenir des catalyseurs afin d'oxyder sélectivement le monoxyde de carbone provenant d'un flux gazeux d'entrée qui contient du monoxyde de carbone, de l'oxygène et de l'hydrogène. Les procédés appliqués à l'aide desdits catalyseurs d'oxydation préférés permettent une oxydation sélective du monoxyde de carbone avec une consommation minimale d'hydrogène sur de larges plages de température. Dans certains modes de réalisation, les catalyseurs selon l'invention comportent un support d'oxyde sur lequel est dispersé du cuivre ou un oxyde de cuivre, un métal du groupe platine et un oxyde métallique réductible. Dans d'autres modes de réalisation, les catalyseurs selon l'invention comportent un support d'oxyde de cérium sur lequel est dispersé du cuivre ou un oxyde de cuivre et un métal du groupe platine. L'invention concerne également un appareil, tel qu'un dispositif de transformation du combustible, qui fournit de l'hydrogène à une pile à combustible et qui comprend les catalyseurs d'oxydation selon l'invention.
PCT/US2002/035545 2001-11-09 2002-11-06 Catalyseur d'oxydation a base de cuivre dope par un metal du groupe platine et procedes de biorestauration du monoxyde de carbone Ceased WO2003051493A2 (fr)

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US10/035,525 US6913739B2 (en) 2000-09-25 2001-11-09 Platinum group metal promoted copper oxidation catalysts and methods for carbon monoxide remediation
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WO2006052866A1 (fr) * 2004-11-05 2006-05-18 Tufts University Traitement de catalyseurs a base d'oxyde de cerium avec de l'oxygene afin d'en ameliorer la stabilite dans la conversion catalytique et reactions selectives de co-oxydation
WO2006130574A1 (fr) * 2005-06-01 2006-12-07 Engelhard Corporation Catalyseur d'oxydation preferentielle ameliore contenant du platine, du cuivre et du fer pour eliminer le monoxyde de carbone d'un gaz riche en hydrogene
EP2143488A1 (fr) * 2008-07-09 2010-01-13 W.C. Heraeus GmbH Catalyseur d'oxydation
US7781368B2 (en) 2006-02-14 2010-08-24 Basf Se Adsorption composition and method of removing CO from streams
EP1787720A4 (fr) * 2004-07-15 2011-08-31 Nikki Universal Co Ltd Catalyseur utilise pour purifier un gaz d'echappement contenant un compose azote organique et procede d'epuration d'un tel gaz d'echappement
US8022264B2 (en) 2006-06-21 2011-09-20 Basf Se Adsorption composition and method of removing CO from streams
US8236264B2 (en) 2006-12-01 2012-08-07 Basf Se Adsorption composition and process for removing CO from material streams
WO2013163536A1 (fr) * 2012-04-26 2013-10-31 Basf Corporation Composition de catalyseur à métal de base et procédés de traitement des gaz d'échappement d'une motocyclette
CN108940296A (zh) * 2018-08-02 2018-12-07 沈炳龙 Co-Mo-Ni/TiO2-Al2O3催化剂在脱除CO中的应用
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GB2256375B (en) * 1991-05-31 1995-06-07 Riken Kk Exhaust gas cleaner and method of cleaning exhaust gas
JP3796744B2 (ja) * 1997-10-16 2006-07-12 日産自動車株式会社 水素ガス中のｃｏ選択酸化触媒およびその製造方法ならびに水素ガス中のｃｏ除去方法
DE10013894A1 (de) * 2000-03-21 2001-10-04 Dmc2 Degussa Metals Catalysts Verfahren zur katalytischen Umsetzung von Kohlenmonoxid in einem Wasserstoff enthaltenden Gasgemisch mit verbessertem Kaltstartverhalten und Katalysator hierfür

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EP1787720A4 (fr) * 2004-07-15 2011-08-31 Nikki Universal Co Ltd Catalyseur utilise pour purifier un gaz d'echappement contenant un compose azote organique et procede d'epuration d'un tel gaz d'echappement
US8575054B2 (en) 2004-07-15 2013-11-05 Nikki-Universal Co., Ltd. Catalyst for purifying organic nitrogen compound-containing exhaust gas and method for purifying the exhaust gas
WO2006052866A1 (fr) * 2004-11-05 2006-05-18 Tufts University Traitement de catalyseurs a base d'oxyde de cerium avec de l'oxygene afin d'en ameliorer la stabilite dans la conversion catalytique et reactions selectives de co-oxydation
WO2006130574A1 (fr) * 2005-06-01 2006-12-07 Engelhard Corporation Catalyseur d'oxydation preferentielle ameliore contenant du platine, du cuivre et du fer pour eliminer le monoxyde de carbone d'un gaz riche en hydrogene
US8445402B2 (en) 2005-06-01 2013-05-21 Basf Corporation Preferential oxidation catalyst containing platinum, copper and iron
US7884048B2 (en) 2006-02-14 2011-02-08 Basf Se Adsorption composition and process for removal of CO from material streams
US7781368B2 (en) 2006-02-14 2010-08-24 Basf Se Adsorption composition and method of removing CO from streams
US8022264B2 (en) 2006-06-21 2011-09-20 Basf Se Adsorption composition and method of removing CO from streams
US8236264B2 (en) 2006-12-01 2012-08-07 Basf Se Adsorption composition and process for removing CO from material streams
EP2143488A1 (fr) * 2008-07-09 2010-01-13 W.C. Heraeus GmbH Catalyseur d'oxydation
US8753999B2 (en) 2008-07-09 2014-06-17 Heraeus Precious Metals Gmbh & Co. Kg Oxidation catalyst
WO2013163536A1 (fr) * 2012-04-26 2013-10-31 Basf Corporation Composition de catalyseur à métal de base et procédés de traitement des gaz d'échappement d'une motocyclette
US8668890B2 (en) 2012-04-26 2014-03-11 Basf Corporation Base metal catalyst composition and methods of treating exhaust from a motorcycle
KR20150008887A (ko) * 2012-04-26 2015-01-23 바스프 코포레이션 비금속 촉매 조성물 및 모터사이클로부터의 배기물의 처리 방법
KR102222867B1 (ko) * 2012-04-26 2021-03-04 바스프 코포레이션 비금속 촉매 조성물 및 모터사이클로부터의 배기물의 처리 방법
CN108940296A (zh) * 2018-08-02 2018-12-07 沈炳龙 Co-Mo-Ni/TiO2-Al2O3催化剂在脱除CO中的应用
CN108940296B (zh) * 2018-08-02 2021-04-30 沈炳龙 Co-Mo-Ni/TiO2-Al2O3催化剂在脱除CO中的应用
US11358128B2 (en) 2019-12-30 2022-06-14 Saudi Arabian Oil Company High activity reforming catalyst formulation and process for low temperature steam reforming of hydrocarbons to produce hydrogen

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