CA1319360C - Oxidation of carbon monoxide and catalyst therefor - Google Patents
Oxidation of carbon monoxide and catalyst thereforInfo
- Publication number
- CA1319360C CA1319360C CA000576788A CA576788A CA1319360C CA 1319360 C CA1319360 C CA 1319360C CA 000576788 A CA000576788 A CA 000576788A CA 576788 A CA576788 A CA 576788A CA 1319360 C CA1319360 C CA 1319360C
- Authority
- CA
- Canada
- Prior art keywords
- composition
- matter
- accordance
- temperature
- material obtained
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Catalysts (AREA)
Abstract
Abstract A composition of matter, which is active as a CO oxidation catalyst at about 10°-50°C, consists essentially of TiO2 or a TiO2-coated ceramic material, platinum metal, and iron oxide. Another composition of matter, which is active as a CO oxidation catalyst at about 10°-50°C, consists essentially of TiO2 or a TiO2-coated porous ceramic material, platinum metal, iron oxide, and palladium metal or silver metal.
Description
13~936~
OXIDATION OF CARBON MONOXIDE AND CATALYST ~HERE~OR
Background of the Invention This invention relates to the oxidation of carbon monoxide to carbon dioxide. In another aspect, this invention relates to the catalytic ogidation of carbon monoxide, in particular under conditions suitable for laser applications. In a further aspect, this invention relates to effective CO oxidation catalyst compositions. In still another aspect, this invention relates to a process for preparing CO
oxidation catalyst compositions.
The use of catalysts for the o~idation of carbon monoxide to carbon dioxide by reaction with oxygen, in particular at low temperature, is of much interest, e.g., in breathing masks designed to remove CO from inhaled air, and in CO2 lasers for combining CO and 2 formed by dissociation of CO2 during discharge. In the latter application, the presence of 2 is most undesirable because it can cause a breakdown of the electrical field in the laser cavity. Several patents, such as U.S.
Patents 4,490,4~2 and 4,~39,432, discIose compositions useful as CO
oxidation catalysts in CO2 laser applications. However, there is an ever present need to develop new, effective CO oxidation catalyst compositions andlor improved processes for preparing effective CO oxidation catalyst compositions.
Summary of the Invention It is an object of this invention to provide a composition of matter which is effective as a catalyst for the oxidation of carbon monoxide with free oxygen. It is another object to provide a process ior ~3~g~ 323l4rhc preparing a co~position of matter which is effective as a catal~Jst for the oxidation of carbon monoxide. It is a further object of this invention to provide an effective process for catalytically oxidizing carbon monoxide. Other objects and advantages will ~e apyarent from the de-tailed description and the claims.
In accordance with this invention, a process for preparing a composition of matter comprising Pt and/or Pd and TiO2 ~suitable and efective as a catalyst composition for the oxidation of carbon monoxide by reaction with free o~ygen) comprises the steps of:
(a) contacting (preferably impregnating) a support material (~rom which silica is substantially absent) comprising (preferably consisting essentially of) titanium dioxide (titania) with a solution comprising at least one dissolved compound of at least one noble metal selected from the group consisting of platinum and palladium (preferably Pt);
~ b) heating the material obtained in step (a~ under such condltions as to substantially dry said material obtained in step ~a) and to a-t least partially (preferably substantially) convert said at least one compound of Pt and/or Pd to at least one of oxides of Pt, oxides of Pd, Pt metal and Pd metal; and (c) heating the material obtained in step (b) in a reducing gas atmosphere, preferably a free hydrogen containing gas, more preferably a stream of H2, at a temperature in the range of from about 300 to about 800C, under such conditions as to activate said material obtained in step (b), i.e, to make the material obtained in step (b) more active as a catalyst for CO oxidation by reaction with 2-In a preferred embodiment, heating step (b) is carried out in two sub-steps:
~bl) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids [i.e., the solvent of the soll-tion used in step (a)] from said material obtained in step (a), and (b~) heating ~calcining) the substantially dried material obtained in step (bl) at a second temperature, which is higher than said 13 ~ 32314CA~
first temperature, so as to at leas-t partially (preferably substantially~
convert said at least one compound o~ Pt and/or Pd to at least one ~f oxides of Pt, oxides of Pd, metallic Pt and metallic Pd (i.e., Pt oxide and/or Pd oxide and/or Pt metal and/or Pd metal).
In another preferred embodiment, the solution used in step (a) additionally comprises at least one dissolved compound of at least one metal selected from the group consisting of rhenium, iron, ruthenium, copper and silver, which are at least partially (preferably substantially) converted to metal oxides in step (b) or, alternatively, step (b2). In another preferred embodiment, compounds of chromium, manganese and zinc are substantially absent (besides silica) from the material obtained in step (c). In a further pre~erred em~odiment, the titania support ma~erial, before its being used in step (a) has been extracted with an aqueous acidic solution (so as to remove undesirable impurities thereform), treated with an alkaline solution, washed (e.g., with water), dried, and then calcined (e.g., at about 200-800C, preferably for about 0.5-10 hours).
In a particular 2referred embodiment, a process ior preparing a composi-tion of matter comprising Pt and/or Pd and TiO2 (effective as a CO
oxidation catalyst composition) comprises the step of:
(A) impregnating a mono]ith material, (i.e., a porous ceramic honeycomb material) with a colloidal dispersion (also referred to as a colloidal solution) of titania in a suitable liquid dispersion medium (preferably water), wherein dispersed silica is substantially absent in said colloidal dispersion;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated monolith material;
(C) contacting (preferably i~pregnating3 the titania-coated monolith material obtained in step (B) ~ith a solution (preferably aqueous), comprising at least one dissolved compound of at least one noble metal selected from the group consisting o~ platinum and palladium (preferably Pt);
(~) heating the material obtained in step (C~ under such conditions as to substantially dry the material obtained in step (C) and to at least partially (preferably substantially) convert said at least ~ 3 ~ 9 ~ 314~h5 one compound of Pd and/or Pt to at least one of oxides bf Pt, oxide~ of Pd, Pt metal and Pd metal; and (E) heating the material obtained in step (D) in a reducin~ gas atmosphere, preferably a free hydrogen containing gas, mo-~e preferably a stream of H2, at a -temperature in the range of from about 0C to about 300~, under such conditions as to activate said material obtained in step (D), i.e., to make it more active as a C0 oxidation catalyst.
The impregnation step (A) can be carried out once or twice or more than twice in sequence, so as to ensure adequate coating of the monolith with TiO2. Step (D) can be carried out as a sequence of sub-steps: drying sub-step (D1) and calcining sub-step (~2~. The conditions of drying steps (B) and (~1) are substantially the same as those of drying sub-step (bl), described above. The conditions of calcining sub-step tD2~ is substantially the same as those of calcining sub-step ~b2), described above.
Al~o in accordance with this invention, there is provided a composition of matter (useul and effective as a catalyst composition for the oxidation of C0 with 2), from which silica is substantially absent, comprising (i) a support material comprising (preferably consisting essentially of) titania and (ii) at least one noble metal selected from the group consisting of Pt and Pd; said composition of matter having been prepared by the process, described above, comprising steps (a), (b) and (c); or, alternatively, steps (a), (bl), (b2) and (c); or, preferably, steps (~), (B), (C), (D~ and (E), as definea above. Preferably said composition of matter further comprises (iii) at least one substance selected from the group consisting of rhenium oxide, iron oxide, ruthenium metal, ruthenium oxide, copper metal, copper oxide, silver metal and silver oxide, preferably iron oxide. In a more preferred embodiment, the composition of matter o~ this invention consists essentialIy of components (i), (ii) and (iii).
~ urther in accordance with this invention, a process for oxidizing carbon monoxide comprises contacting a gas comprising C0 and 2 with a catalyst composition (from which silica is substantially absent~
comprising titania and at least one of Pt and Pd; said catalyst composition having been prepared by a process comprising steps (a), (b) 13193~0 323l4chc and ~c); or, alternatively, (a), (bl), (b2) and (c); or, preferably, (A), (B), (C), (D) and (E), as defined above, under such conditions as to at least partially (preferably substantially) convert CO and 2 to CO~.
Preferably, in the CO oxidation in process of this invention the catalyst composition of this inven~ion (described above) additionall~
comprises component (iii), as defined above, preferably iron oxide (e g., FeO and/or Fe203 andtor Fe304). Also preferably, compounds of Cr, Mn and ~n are substantially absent from the catalyst composition (be~ides SiO2).
In a preferred embodiment, the CO oxidation process of this invention i5 carried out at a temperature of below lOO~C (more preferably from about 0C to about 90C). In another preferred embodiment, the CO oxidation process is carried out in a CO2 laser so as to recombine CO and 2, which have been formed by decomposition of COz.
Brief Description of the Drawings FIGUæE 1 shows the dependence of CO conversion during low temperature oxidation of CO upon the temperature during the reducing pretreatment of a Pt/TiO2 catalyst with H2.
FIGURE 2 illustrates the effect of copromoters on the catalytic activity of a PtfTiO2 catalyst when used for low temperature oxidation of CO.
FIGURE 3 illustrates the effect of copromoters on the catalytic activity of a Pt/Fe/TiO2 catalyst when used for low temperature oxidation of CO.
Deta-led Description of the Invention Any titania-containing support material can be used as the support material (i). Titania, as the preferred support material, is commercially available. The method of preparation of titania is not considered critical. Titania can be prepared by flame hydrolysis of volatile titania compounds; or by precipitation from an aqueous solution of titanium compounds with an alkaline reagent, followed by washing, drying and calcining; and the like. If mixtures of titania with alumina and/or magnesia are used, any suitable weight ratio can be used ~such as from 1-99 weight-% TiO2 and from 99-1 weight-h Al203 and/~r MgO).
&enerally the surface area ~determined by the BET/~2 method;
ASTM D3037) of titania is in the range of from about 10 to about 300 ~93~ 32314C~C
m2/g. Titania can have spherical, trilobal, quadrilobal or irregular shapes. When titania spheres are used, their diameter generally is in the range of from about 0.5 to about 5 mm. Silica should be substantially absent from the support material (i e., ~ilica should not be present at a level higher than about a.5, preferably about 0.2, weight-% each).
It is within the scope of this invention to prepare suitable support materials by coating a honeycomb ce. ami-~ material, such as a monolith (commercially available from Corning Glass Works, Corning, NY), described in U.S. Patents 4,388,277 and 4,524,051, with titania. The monolith can be impregnated with organic compounds o' Ti (such as a titanium tetraalkoxide), hydrolyzed, dried and calcined. Or the monolith can be impregnated with a dispersion of titania particles, followed by drying and calcining.
In the presently more preferred embodiment of this invention, a mon~lith is impregnated with a colloidal dispersion (colloidal solution) of titania in step (A). Preferably, colloidal particles of titania having an aYerage particle diameter of about 1 to about 100 nanometers, more preferably about 5 to about 20 nanometers, are dispersed in any suitable liquid dispersion medium, such as water, alcohols, ketones and the like, preferably water. Generally, the concentration of TiO2 in the colloidal dispersion is in the range of from about 0.1 to about 50, preferably from about 5 to about 25, weight percent TiO2. The weight ratio of colloidal dispersion of TiO2 to monolith material in step (A) is chosen so as to provide a TiO2 content of the material obtained in step (B) in the range of from about 1 to about 4Q weight-% TiO2, preferably about 5 to about 30 weight-l~ TiO2.
The impregnation of the titania-containing support ma-terial with Pt and/or Pd (preferably Pt) in steps (a) and ~c), respectively, can be carried out in any suitable manner. ~irst, compounds of Pt and/or Pd are dissolved in a suitable solvent (preferably water) so as to prepare solutions of suitable concentration, generally containing from about 0.005 to about 0.20, preferably about 0.01 to about 0.1, g Pt and/or Pd per cc of solution. Non-limiting examples of suitable compounds of Pt and Pd are: PtCl2, PtCl4, H2PtCl6, PtBr4, Pt(NH3)4cl2~ PtlNH3)~(~03)2 ~ ~193~ 323l4rA~
and the like; PdC12, PdCl4, H2PdCl6, Pd(NH3)4(NO3)2 and the like;
preferably (at present) Pt(NH3)4(NO3)2 and Pd(NH3)4(N03)2. The TiO2-containing support material is then impregnated by soaking it in the solution of Pt and/or Pd compounds; or (less preferably) the Pt and/or Pd containing solution is sprayed onto the support material. The ratio of Pt and/or Pd containing solution to support material generally is such that the final catalyst obtained in step (c) or, alternatively, the coating of the material obtained in (~), i.e., the material obtained in step (E) excludi~g the monolith, contains about 0.5 to about 5, preferably about 1 to about 3, weight-~ Pt or Pd. When a solution containing both Pt and Pd compounds, the level of Pt and Pd generally is about 0.5 to about 5, preferably about 1 to about 3, weight percent (Pt+Pd).
In a preferred embodiment, at least one compound of a metal selected from the group of Re, Fe, Ru, Cu and Ag, more preferably Fe, is also present as a copromoter in the impregnating solution (besides Pt and/or Pd). Non-limiting examples of suitable Fe compounds that can be used as solutes are FeCl2, FeCl3, Fe2(S04)3, Fe(N03)2, Fe(N03)3 and the like, preferably compounds of Fe in the valence state ~3, more preferably Fe(~03)3. Non-limiting examples of Nn compounds are MnCl2, MnS04, MntNO3)2, KMnO4, and the like. Non-limiting examples of Ru compounds are RuCl3, RuE4, Ru~NH3)6Cl3, KRu04, and the like. Non-limiting examples of Cu compounds are CuC12, Cu~NO3)2, GuS04, Cu(II) acetate, ammine complexes of the above Cu salts, and the like. Non-limiting examples of Ag compounds are AgF, AgN03, Ag2S04, Ag acetate, ammine complexes of the above Ag salts, and the like.
Cenerally, the concentration of the copromoter compound (expressed as metal) is in the ran8e of from about 0.01 to about 0.4, preferably about 0.02 to about 0.2, g metal (i.e., Mn or Fe or Ru or Cu or Ag or mixtures thereof) pex cc solution. When a mixture of copromoter compounds is used, e.g., a mixture of compounds of Fe and Ru, Fe and Ag, Ru and Cu, Fe/Ru/Ag, and the like, the total concentration of copromoter metals is about 0.02-0.8 g/cc. The impregnation of the support material with Pt and/or Pd and the copromoter method can be carried out either by sequential impregnation (first Pt and/or Pd, then copromoter) or by 13 ~ 9 3 ~ ~ 32314CAC
simultaneous impregnation in step (a) or, alternatively, step (C~ (using a solution containing Pt and/or Pd compounds and at least one copromoter compound).
When sequential impregnation is employed, the impregnation with a solution of at least one copromoter compound is carriPd out after heating step (b) and before step (c); or, if applicable, after heating step (D) and before step (E). Thus, an impregnating step (a*) with at least one dissolved copromoter compound and heating step (b*) [carried out in substantially the same manner as step (b)] are performed after step (b) and before step (c). Similarly, an impregnation atep (~') ~ith at least one dissolved copromoter compound and heating step (D*) [carried out in substantially the same manner as step (D)] are performed after step (D) and before step (E). The ratio of copromoter containing solution to support material is such as to provide a level of about 0.2 to about 4, preferably about 0.5-2, weight percent copromoter metal ~i.e., Re or Fe or Ru or Cu or Ag, or mixtures of two or more metals, (e.g., Fe/Ag, and the like) on the material obtained in step (c) or, alternatively, on the material obtained in step (~) excluding the monolith.
Preferably compounds of Cr, Mn and Zn should be substantially absent from the impregnating solutions used in impregnation steps (a), (a~), (C) and (C~) since these compounds have a detrimental effect on the activity for C0 oxidation of the finished catalyst.
Heating step (b) is generally carried out in an inert or oxidizing atmosphere, preferably a free oxygen containing gas atmosphere (such as air), generally at a temperature ranging from about 30 to about 700C. Preferably, heating step tb) is carried out in tWQ sequential sub-steps: sub-step (bl), at about 3a to about 200C (preferably at 30-130C~, generally for about 0.5 to about 10 hours, so as to substantially dry the impregnated material obtained in step (a) (preferably under such conditions as to reduce the level of adhered and accluded water to less than about 20 weight-~O)j and sub-step (b2), at about 300 to about 700C (preferably about 400 to about 600C), generally for about 1 to about 20 hours, under such conditions as to substantially calcine the impregnated support material so as to obtain oxides of Pt 131936~ 32314CAC
and/or Pd, on titania. When compounds of Re, Fe, Ru, Cu or Ag or mixtures thereof have been present in the Pt and/or Pd-containing impregnating solution, gene-rally oxides of Re, Fe, Ru, Cu and/or Ag are formed in step (b2).
Drying sub-steps (b~l), (Dl~ and (D*l), described above, are carried out at conditions which are essentially the same a~ ths~e described for sub-step (bl). And calcining sub-steps (b*Z) 7 (D2) and (D-~2), described above, are carried out at conditions which are essentially the same as those described for sub-step (b2) Reducing step (c) can be carried out in any suitable manner at a temperature in the range of from about 300 to about 800C, preferably rom about 350 to about 500~C. Reducing step (~) can be carried out in any suitable manner at a temperature in the range of from about 0 to about 300C, preferably about 20 to about 200C. Any reducing gas can be employed in reducing steps (C) and (E~, such as a gas comprising H2, C0, gaseous hydrocarbons such as methane, mixtures of the above, and the like. Preferably, a free hydro~en containing gas, more preferably sub~tantially pure H2, is employed. Reducing steps (c) and (E) can be carried out for any suitable period of ~ime suitable to activate the calcined material obtained in the previous step, preferably from about 0.5 to about 20 hours.
The process for oxidizing a carbon monoxide containing feed gas can be carried at any suitable temperature and pressure conditions, for any suitable length of time, at any suitable gas hourly space velocity, and any suitable volume ratio of C0 and 2 The reaction temperature generally is in the rang eof from about 0 to about 400C, preferably about 0 to about 100C, more preferably from about 10 to about 50C, most preferably about 20-4aoc. The pressure during the oxidation process generally is in the range of from about 1 to about 2,000 psia, more preferably from about 5 to about 20 psia. The volume ratio of C0 to 2 in the feed gas can range from about 1:100 to about 100:1, and preferably is in the range of about 1:10 to about 10:1. The volume percentage of C0 and the volume percentage of f 2 in the feed gas can each be in the range of from about 0.05 to about 50, preferably from about 0.5 to about 3. The gas hourly space velocity (cc feed gas per cc catalyst per hour) 13~936~ 32314ChC
can be in the range of from about 0.5 to about 10,000, preferably from about 1 to about 1,000. It is understood that the calculation of the ~a~
hourly space velocity is based on the volume of the active catalyst i.e , the titania-supported Pt and/or Pd catalyst toptionally also contaiuing copromoter), excluding the volume occupied by any additional ~upport material, such as a monolith material.
The feed gas can be formed in any suitable manner, e g., by mixing C0, 2 and optionally other gases such as CO2, N2~ He and the like, such as in a carbon dioxide laser cavity. Or the feed gas can be an exhaust gas from a combustion engine, or it can be air that is to be inhaled by humans and contains undesirable levels of toxic carbon monoxide, and the like. The feed gas can be contacted in any suitable vessel or apparatus, such as in a laser cavity or in an exhaust pipe of a combustion engine, or in a gas mask used by humans, wherein the feed gas passes over the catalyst composition of this invention at the conditions described above. The CO oxidation process of this invention can be carried out in any suitable setting and for any purpose, e.g., for recombining C0 and 2 in CO2 lasers, to oxidize CO contained in exhaust gases or air, to make isotopically labeled CO2 from CO and the 1~o isotope, and the like.
The following examples are presented in further illustration of the invention and are not to be construed as unduly limiting the scope of the invention.
Example I
This example illustrates the experimental setup for testing the activity of noble metal catalysts for catalyzing the oxidation of carbon monoxide (so as to simulate catalytic recombination of C0 and 2 in CO2 lasers). A gaseous feed blend comprising C0, 2, ~le and ~2 was passed through a needle valve and a glass reactor in an upflow direction. The glass reactor tube had an inner diameter of about 6 mm and generally contained about 1.0 gram catalyst in a bed of about 2.5 cm height. The temperature in the catalyst bed was measured by means of a thermocouple inserted into the top layer of the catalyst bed. The CO content in the reactor effluent was determined by means of a Beckman Model 864 IR
analyzer.
131936~ 32314CAC
All tests were carried out at ambient conditions. Generally the temperature in the catalyst bed rose to about 30C because of the generation of hPat during the 50 oxidation tests. The feed rate of the gaseous feed stream generally was in the range of about 4-300 cc/minute.
Example II
This example illustrates the preparation of titania-supported catalyst compositions and their performance in CO oxidation testg.
Catalyst A1 con-tained 1 weight-% Pt on TiO2 ~t was prepared by mixing, a~ room temperature, 30 g of flame-hydrolyzed titania (provided by Degussa Corporation, Teterboro, NJ; having a B~T/N2 surface area of about 50 m2/g) with 31 cc of aqueous chloroplatinic acid solution, which contained 0 0096 g Pt/cc solution, and enough distilled water to form a thick paste After impregnation, Catalys~ Al was dried at about 125C for several hours and calcined in air at about 350C for about 6 hours Catalyst Al was then pretreated with hydrogen gas for about 4 hours at various temperatures (range: 200-725C) Samples of catalyst A1 (1% Pt/TiO2) that had been pretreated with H2 at different temperatures was tested at room temperature (about 27GC) in the C0 oxidation unit described in E~ample I. The gaseous feed blend contained 1.2 volume-~/O C0, 0.6 volu~e-/O 2~ 40.7 volume-% N2 and 57.5 volume-% He. The feed rate was 10 cc/minute. The ~orrelation between C0 conversion and the temperature of the hydrogen pretreatment temperature of Catalyst Al is shown in Figure 1. Figure 1 shows that H2 pretreatment of the Pt/TiO2 catalyst at temperatures in the range of 400 to 725C resulted in a considerably more active C0 oxidation catalyst than H2 pretre~tment at 200C.
Catalyst A2 contained 1 weight-l~ Pt and 0 3 weight-b Pd on TiO2, and was prepared by mixing 30 g Catalyst Al with 100 cc of an aqueous solution containing 0.25 g tetramminepalladinum(II) nitrate, drying and calcining the obtained paste as described for Catalyst Al.
The calcined Catalyst A~ material was then activated by heating with H2 at 725C for 16 hours C0 conversion tmeasured as described for the tests employing Catalyst A1) was 100% for about 126 hours. Thus, Pd enhanced the C0 o~idation activity of the Pt/TiO2 catalyst.
3 1 9 ~ 6 ~ 32314CAC
~xample III
This example illustrates the effects of various other copromoters on the C0 oxidation activity of a Pt/TiO2 catalyst which contain~d 2 weight-% Pt (labeled Catalyst Bl) and was prepared substantially in accordance with the procedure for Catalyst Al, e-~cept that the Pt concentration in the impregnating solution was thrice as high, and the TiO2 support material was provided by Calsicat (division of Mallinckrodt, Inc., St. Louis, MO) and had a BET surface area sf about 40-170 m2/g.
Catalyst Bl was then mixed with aqueous solutions containing different metal compounds so as to provide a copromoter level of 0.8 weight-% of the metal. A solution of tetramminepalladinum(II) nitrate was used to make Catalyst B2 (0.8% Pd/2% Pt/TiO2~. A solution of Ru~13 3H20 was used to make Catalyst B3 (0.8% Ru/2% Pt/Ti2) A
solution of ReCl3 was used to make Catalyst B4 (0.8% Re/2% Pt/TiO2). A
sGlution of hexamminechloroiridium(II) dichloride was used to make Catalyst B5 (0.8% Ir/2% Et/TiO2~. A solu~ion of Cu(N03)2 2.5H20 was used to make Catalyst B6 (0.8b Cu/2% Pt/TiQ2). A solution of Fe(N03) 9H20 was used to make Catalyst B7 (0.8% Fe/2/O Pt/TiO2).
C0 conversions attained at room temperature (about 27C) in the test unit of Example I employing a gas ieed containing 1.2 volume-% CO, 0.6 volume-/O 2, 48 volume-/O N2 and He as the balance (flow rate of feed:
10 cc/minute), are shown for Catalysts B1, B2, B3, B4, B5, B6 and B7 in Figure 2. All catalysts had been pretreated with hydrogen gas for 3 hours at 600C.
The graphs in Figure 2 indicate that Fe, Pd, Re, Ru and Cu consistently enhanced the C0 oxidation activity of the Pt/TiO2 base catalyst, whereas Ir enhanced the C0 oxidation ac-tivity of the base catalyst only up to 60 hours on stream. Additional test data (not shown in Figure 2~ indicated that Rh did not affec~ the catalytic activity of the PtlTiO2 base catalyst. Fe, Pd and Re were the most effective copromoters for the Pt/TiO2-containing C0 oxidation catalyst.
In another test series, a TiO2-supported catalyst containing 0.4 weight-h Fe and 2.0 weight-b Pt, labeled Catalys-t B8, was prepared substantially in accordance with the procedure for Catalyst B7 t except ~ 3 ~ 32~14CAC
for a lower Fe level. Catalyst B8 was then impregnated tlith an aqueo~s solution containing a compound of a third promoter metal, so as to obtain Catalysts _ , Bl0, Bll and B12, respectively, containing 0.1 weight % o~
the following third promoter elements: Mn, Cr, Ag and Zn. Carbon 5 monoxide conversions, attained by Catalysts B8, B9, B10 and Bll at room temperature (about 27C) in the test unit of Example I employing the gas feed described in Example II are shown in Figure ~. The gas feed rate was 60 cc/minute (in lieu of 10 cc/minute). All catalysts had been pretreated in hydrogen gas for 3 hours at about 500C. The TiO2 support had been heated in H2 for about 48 hours at 500C before impregnation with the promoters (Fe, Pt ~ third promoter) for removal of traces of sulfur in TiO2.
The graphs in Figure 3 indicate that Ag enhanced the activity of the Fe~Pt/TiO2 C0 oxidation catalyst, whereas the presence of Mn, Cr and Mn was detrimental. Based on these test results, it is concluded that Ag i5 also an effective promoter for a Pt/TiO2-containing catalyst (with or without Fe).
Example IV
This example illustrates a preferred feature of the preparation of TiO2-supported Pt catalysts useful for C0 oxidation at low temperature. Two catalysts containing 0.5 weight-% Fe, and 2.0 weight-%
Pt on Calsicat TiO2 support were tested. Catalyst Cl was prepared substantially in accordance with the preparation of Catalysts B7 and B8, using an aqueous solu-tion of chloroplatinic acid. Catalyst C2 was prepared as described above except that the dissolved Pt compound was te~rammineplatinum(II) nitrate. The two catalysts were dried, calcined and pretreated with hydrogen gas at 500C for about 3 hours, as has been described in ~xamples II and III.
The two catalysts were tested at room temperature (about 26C) in the C0 oxidation test unit described in E~ample I, employing the gas feed described in Example III. The gas ~eed rate was 120 cc/minute.
Test results are summarized in Table I.
13~936B 3Z~14CAC
Table I
Hours on % C0 cclMinute Catalyst Stream Converted C0 Con~erted Cl 2 60 ~.84 6 56 0 7~
1~ 56 0.78 1~ 55 0.77 ~0 55 0.77 301 50 0.70 ~0 401 44 0.62 C2 2 63 0,89 6 70 0.98 78 1.09 89 1.25 94 1.3Z
92 1.30 92 1.3 1.2 91 1.27 ~0 lTemperature had dropped to 23C.
Test results in Table I clearly show that the Fe/Pt/TiO2 catalyst prepared using a chloride-free Pt compound for impregnation (Catalyst C2) was consistently more active for C0 oxidation than Catalyst Cl, which had been prepared using a chloride-containing Pt compound for impregnation.
Example V
This example illustrates how the C0 oxidation activity of a TiO2-supported catalyst can be enhanced by pretreatment of the TiO2 support.
25 grams of flame-hydrolyzed titania (provided by Degussa Corporation; see Example II) was stirred overnight in a mixture of ~00 cc concentrated H2SO~ and 300 cc deionized water. The aqueous slurry of titania was then neutralized wi~h a concentrated ammonia solution. The -dispersed titania was allowed to settle, and the supernatant solution was decanted. The thus treated titania was washed four times with deioni~ed water and dried in a circulating air oven (80-90C; 5 hours3.
S grams of the acid-treated TiO2 was impregnated with 3 cc of an aqueous solution of Pt(NH3)4(NO~)2 (containing 0.033 g Pt per cc) and 13193~ 32314CAC
then with 2.5 cc of an aqueous solution of Fe(~03)3 ~containing ~ 01 g ~e per cc~. The thus impregnated material was dried, calci~ed and pretreated with hydrogen gas for 3 hours at 500C. This catalyst, labeled Catalyst D, contained 2 weight-~ Pt and 0.5 weight-% Fe Catalyst D was compared to Catalyst C2 (see ~xa~ple IY; also containing 2 weight-% ~e on TiO2) which had been prepared without acid treatment of titania (provided by Degussa Corporation). The two catalysts were tested at room temperature (27-29gC) in the C0 o~idation test unit described in Example I, employing the gas feed described in ~xample III. Test results are summarized in Table II.
Table II
Gas Feed Hours on % C0 cc/Minute CatalystRate (cc/min.) Stream ConvertedC0 Converted -D 160 2 58 1.09 15 (TiO2 Support " 4 65 1.22 Acid-Treated) " 6 68 1.28 " 10 68 1.28 " 14 68 1.28 " 18 67.5 1.26 " 22 67.5 1.26 C2 120 2 56 ~.79 (TiO2 Support " 4 48 0.67 Not Acid-Treated) " 6 43 0.60 " 10 41 0.58 25" 14 41 0.58 " 18 ~2 0.59 Data in Table II clearly indicate that the C0 conversion was greater for Catalyst D as compared to Catalyst C2 in spite of the higher gas feed rate of the run with Cataly~t D. The conversion of C0, expressed in cc C0 converted per minute, attained by Catalyst D was about twice that attained by Catalyst C2.
Thus, in the presently preferred catalyst preparation method of this invention, the TiO2 support material is treated with an aqueous acid solution, followed by neutralization and washing, before the TiO2 support material is impregnated with promoters, dried, calcined and heated in H~
gas.
16 1~93~
~xample VI
This example illustrates the use of honeycomb ceramic catalyst supports, called monoliths, for preparing Pt/TiO2-containing catalysts employed in the oxidation of carbon monoxide. The two best modes of preparation of these honeycomb catalysts are described in this example.
Mode A: A round piece of Celcor~ Cordierite #9475 monolith ceramic material 2MgO 2Al203 5SiO2; provided by Corning Glass Works, Corning, NYi diameter: 1 inch; height 1 inch; having 100 cells per square inch) was dried for 2 hours at 185C, and was then dipped about 7 times into a stirred suspension of 30 grams flame-hydrolyzed TiO2 (Degussa Corporation) in 250 cc distilled water. The material was dried a$ter each dipping. This TiO2-coated monolith material was calcined in air for 4 hours at 500C. The calcined TiO2-coated monolith material was then dipped into an aqueous solution of chloroplatinic acid (containing 0.022 g Pt/cc), dried for 1 hour at 300C, dipped into an a~ueous solution of Fe~N03)3 (containing O.Ol g Fe/cc) and dried again for 1 hour at 300C. The Fe/Pt/TiO2/monolith catalyst, labeled Catalyst El, was pretreated in hydrogen gas for 3 hours at 500~C and then heated in helium gas at that temperature for 30 minutes. The impregnation with Pt and Ee, drying and pretreating with H2 was repeated.
Catalyst El was tested in a C0 oxidation apparatus at room temperature (about 26C) in an apparatus similar to the one described in Example I, except that a glass reactor tube of l inch inner diameter was used. The $eed gas employed was essentially the same as the one described in Example III. Test results are summarized in Table III.
1 ~19~ 323~4CA~
Table III
Hours on Gas Feed % C0 cc/Minute Stream Rate (cc/min.)ConversionC0 Converted 4 10 99 O.lZ
99 0.12 96 0.34 24 30 96 ~.34 g1 0.64 0.56 72 0.50 66 0.46 5~ 0.41 0.42 58 0.41 100 60 56 0.40 ~10 60 55 0.38 Mode B: The presently best mode for preparing honeycomb-type Pt/TiO2-containing catalysts is as follows. A piece of Cordierite 9475 monolith material (diameter: 1 inch; height: 1 inch) was dipped into a colloided solution of TiO2 in water (provided by Nalco; containing about 6 weight-~ TiO2 having an average particle diameter of ~ microns). The monolith piece was dipped 9 times into the colIoidal TiO2 solution. The thus impregnated piece was dried at 150C after each dipping. The TiO2-coated monolith was then dipped into an aqueous Pt(~H3)~(N~3)2 solution (containing 0.33 g/cc Pt), dried, calcined in air for 2 hours at 300C, and pretreated in H2 gas after 1 hour at room temperature (25C).
The coating of the thus-prepared catalyst, labeled Catalyst E2, contained about 3 weight-% Pt and about 97 weight-% TiO2.
~ y~ was prepared by dipping E2 into an aqueous solution of Fe(N03)3 (containing 0.01 g Fe per cc), drying, calcining in air for 2 hours at 300C, and pretreating in H2 for 1 hour at room temperatnre.
The coating of Catalyst E2 contained about 3 weight-~ Pt, about 1 weight-% Fe and 96 weight-% TiO2.
Catlayst E4 was prepared by dipping E3 into an aqueous solution of Pd~NH3)4(N03~2 (containing 0.04 g Pd per cc), calcining in air for 2 hours at 300C, and pretreating with H2 for 1 hour at room temperature.
Catalysts E2, E3 and E4 were tested in the experimental setup described for the C0 oxidation run employing Catalyst E1. The gas feed ~3~93~ 32314CAC
rate for all runs was 300 cc/minute. Test results are summarized in Table IV.
Table IV
Hours on /~ C0 cc/Minute Catalyst S~ream Conversion C0 Converted E2 1 9.4 0 33 2 8.5 0.30 4 4.3 0 15 2 6g 2 43 6 69 2.43 1.92 14 47 1.65 33 1.17 Test results in Table IV indicate that high C0 conversions (cc C0/minute) were attained at high gas feed rates (300 cc/minute; higher than in any previous run). Thus the monolith-supported catalysts E2-E4, prepared by impregnation with colloidal TiO2, are considered the presently best TiO2-supported C0 oxidation catalysts.
A run not listed in Table IV employing a catalyst similar to Catalyst E3, except that 0.6 weight-% Mn was prepared in the coating in lieu of 1 weight-% Fe, gave C0 conversions of only about 33% and about 1.2 cc CO/minute during the first 5 hours. Thus, Mn/Pt/TiO2 catalysts are not considered more preferred catalysts of this invention.
A particular advantage of the monolith-supported Pt/TiO2-containing catalysts E2-E4 is that they could be activated by pretreatment in H2 at a low temperature (about 25C), whereas the catalysts used in previous examples required pretreatment in H2 at an elevated temperature (e.g., 400-500C). In fact, reheating Catalyst E4 ~3193~ 32314CAC
for 3 hours in air at 500C and then for 1 hour in hydrogen at 400C ~ade this catalyst substantially inactive for C0 oxidation.
Example VII
A test employing a catalyst, which contained 1 wei~ht-% Pt on SiO2 and had been pretreated in H2 at 660C for about 1 hour, showed no activity for catalyzing the oxidation of C0 at room temperature. Thus, SiO2 should be substantially absent from the ca-talyst of this invention.
Reasonable variations t modifications and adaptations for various usages and conditions can be made within the scope of the disclosure and the appended claims, without departing from the scope of this invention.
OXIDATION OF CARBON MONOXIDE AND CATALYST ~HERE~OR
Background of the Invention This invention relates to the oxidation of carbon monoxide to carbon dioxide. In another aspect, this invention relates to the catalytic ogidation of carbon monoxide, in particular under conditions suitable for laser applications. In a further aspect, this invention relates to effective CO oxidation catalyst compositions. In still another aspect, this invention relates to a process for preparing CO
oxidation catalyst compositions.
The use of catalysts for the o~idation of carbon monoxide to carbon dioxide by reaction with oxygen, in particular at low temperature, is of much interest, e.g., in breathing masks designed to remove CO from inhaled air, and in CO2 lasers for combining CO and 2 formed by dissociation of CO2 during discharge. In the latter application, the presence of 2 is most undesirable because it can cause a breakdown of the electrical field in the laser cavity. Several patents, such as U.S.
Patents 4,490,4~2 and 4,~39,432, discIose compositions useful as CO
oxidation catalysts in CO2 laser applications. However, there is an ever present need to develop new, effective CO oxidation catalyst compositions andlor improved processes for preparing effective CO oxidation catalyst compositions.
Summary of the Invention It is an object of this invention to provide a composition of matter which is effective as a catalyst for the oxidation of carbon monoxide with free oxygen. It is another object to provide a process ior ~3~g~ 323l4rhc preparing a co~position of matter which is effective as a catal~Jst for the oxidation of carbon monoxide. It is a further object of this invention to provide an effective process for catalytically oxidizing carbon monoxide. Other objects and advantages will ~e apyarent from the de-tailed description and the claims.
In accordance with this invention, a process for preparing a composition of matter comprising Pt and/or Pd and TiO2 ~suitable and efective as a catalyst composition for the oxidation of carbon monoxide by reaction with free o~ygen) comprises the steps of:
(a) contacting (preferably impregnating) a support material (~rom which silica is substantially absent) comprising (preferably consisting essentially of) titanium dioxide (titania) with a solution comprising at least one dissolved compound of at least one noble metal selected from the group consisting of platinum and palladium (preferably Pt);
~ b) heating the material obtained in step (a~ under such condltions as to substantially dry said material obtained in step ~a) and to a-t least partially (preferably substantially) convert said at least one compound of Pt and/or Pd to at least one of oxides of Pt, oxides of Pd, Pt metal and Pd metal; and (c) heating the material obtained in step (b) in a reducing gas atmosphere, preferably a free hydrogen containing gas, more preferably a stream of H2, at a temperature in the range of from about 300 to about 800C, under such conditions as to activate said material obtained in step (b), i.e, to make the material obtained in step (b) more active as a catalyst for CO oxidation by reaction with 2-In a preferred embodiment, heating step (b) is carried out in two sub-steps:
~bl) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids [i.e., the solvent of the soll-tion used in step (a)] from said material obtained in step (a), and (b~) heating ~calcining) the substantially dried material obtained in step (bl) at a second temperature, which is higher than said 13 ~ 32314CA~
first temperature, so as to at leas-t partially (preferably substantially~
convert said at least one compound o~ Pt and/or Pd to at least one ~f oxides of Pt, oxides of Pd, metallic Pt and metallic Pd (i.e., Pt oxide and/or Pd oxide and/or Pt metal and/or Pd metal).
In another preferred embodiment, the solution used in step (a) additionally comprises at least one dissolved compound of at least one metal selected from the group consisting of rhenium, iron, ruthenium, copper and silver, which are at least partially (preferably substantially) converted to metal oxides in step (b) or, alternatively, step (b2). In another preferred embodiment, compounds of chromium, manganese and zinc are substantially absent (besides silica) from the material obtained in step (c). In a further pre~erred em~odiment, the titania support ma~erial, before its being used in step (a) has been extracted with an aqueous acidic solution (so as to remove undesirable impurities thereform), treated with an alkaline solution, washed (e.g., with water), dried, and then calcined (e.g., at about 200-800C, preferably for about 0.5-10 hours).
In a particular 2referred embodiment, a process ior preparing a composi-tion of matter comprising Pt and/or Pd and TiO2 (effective as a CO
oxidation catalyst composition) comprises the step of:
(A) impregnating a mono]ith material, (i.e., a porous ceramic honeycomb material) with a colloidal dispersion (also referred to as a colloidal solution) of titania in a suitable liquid dispersion medium (preferably water), wherein dispersed silica is substantially absent in said colloidal dispersion;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated monolith material;
(C) contacting (preferably i~pregnating3 the titania-coated monolith material obtained in step (B) ~ith a solution (preferably aqueous), comprising at least one dissolved compound of at least one noble metal selected from the group consisting o~ platinum and palladium (preferably Pt);
(~) heating the material obtained in step (C~ under such conditions as to substantially dry the material obtained in step (C) and to at least partially (preferably substantially) convert said at least ~ 3 ~ 9 ~ 314~h5 one compound of Pd and/or Pt to at least one of oxides bf Pt, oxide~ of Pd, Pt metal and Pd metal; and (E) heating the material obtained in step (D) in a reducin~ gas atmosphere, preferably a free hydrogen containing gas, mo-~e preferably a stream of H2, at a -temperature in the range of from about 0C to about 300~, under such conditions as to activate said material obtained in step (D), i.e., to make it more active as a C0 oxidation catalyst.
The impregnation step (A) can be carried out once or twice or more than twice in sequence, so as to ensure adequate coating of the monolith with TiO2. Step (D) can be carried out as a sequence of sub-steps: drying sub-step (D1) and calcining sub-step (~2~. The conditions of drying steps (B) and (~1) are substantially the same as those of drying sub-step (bl), described above. The conditions of calcining sub-step tD2~ is substantially the same as those of calcining sub-step ~b2), described above.
Al~o in accordance with this invention, there is provided a composition of matter (useul and effective as a catalyst composition for the oxidation of C0 with 2), from which silica is substantially absent, comprising (i) a support material comprising (preferably consisting essentially of) titania and (ii) at least one noble metal selected from the group consisting of Pt and Pd; said composition of matter having been prepared by the process, described above, comprising steps (a), (b) and (c); or, alternatively, steps (a), (bl), (b2) and (c); or, preferably, steps (~), (B), (C), (D~ and (E), as definea above. Preferably said composition of matter further comprises (iii) at least one substance selected from the group consisting of rhenium oxide, iron oxide, ruthenium metal, ruthenium oxide, copper metal, copper oxide, silver metal and silver oxide, preferably iron oxide. In a more preferred embodiment, the composition of matter o~ this invention consists essentialIy of components (i), (ii) and (iii).
~ urther in accordance with this invention, a process for oxidizing carbon monoxide comprises contacting a gas comprising C0 and 2 with a catalyst composition (from which silica is substantially absent~
comprising titania and at least one of Pt and Pd; said catalyst composition having been prepared by a process comprising steps (a), (b) 13193~0 323l4chc and ~c); or, alternatively, (a), (bl), (b2) and (c); or, preferably, (A), (B), (C), (D) and (E), as defined above, under such conditions as to at least partially (preferably substantially) convert CO and 2 to CO~.
Preferably, in the CO oxidation in process of this invention the catalyst composition of this inven~ion (described above) additionall~
comprises component (iii), as defined above, preferably iron oxide (e g., FeO and/or Fe203 andtor Fe304). Also preferably, compounds of Cr, Mn and ~n are substantially absent from the catalyst composition (be~ides SiO2).
In a preferred embodiment, the CO oxidation process of this invention i5 carried out at a temperature of below lOO~C (more preferably from about 0C to about 90C). In another preferred embodiment, the CO oxidation process is carried out in a CO2 laser so as to recombine CO and 2, which have been formed by decomposition of COz.
Brief Description of the Drawings FIGUæE 1 shows the dependence of CO conversion during low temperature oxidation of CO upon the temperature during the reducing pretreatment of a Pt/TiO2 catalyst with H2.
FIGURE 2 illustrates the effect of copromoters on the catalytic activity of a PtfTiO2 catalyst when used for low temperature oxidation of CO.
FIGURE 3 illustrates the effect of copromoters on the catalytic activity of a Pt/Fe/TiO2 catalyst when used for low temperature oxidation of CO.
Deta-led Description of the Invention Any titania-containing support material can be used as the support material (i). Titania, as the preferred support material, is commercially available. The method of preparation of titania is not considered critical. Titania can be prepared by flame hydrolysis of volatile titania compounds; or by precipitation from an aqueous solution of titanium compounds with an alkaline reagent, followed by washing, drying and calcining; and the like. If mixtures of titania with alumina and/or magnesia are used, any suitable weight ratio can be used ~such as from 1-99 weight-% TiO2 and from 99-1 weight-h Al203 and/~r MgO).
&enerally the surface area ~determined by the BET/~2 method;
ASTM D3037) of titania is in the range of from about 10 to about 300 ~93~ 32314C~C
m2/g. Titania can have spherical, trilobal, quadrilobal or irregular shapes. When titania spheres are used, their diameter generally is in the range of from about 0.5 to about 5 mm. Silica should be substantially absent from the support material (i e., ~ilica should not be present at a level higher than about a.5, preferably about 0.2, weight-% each).
It is within the scope of this invention to prepare suitable support materials by coating a honeycomb ce. ami-~ material, such as a monolith (commercially available from Corning Glass Works, Corning, NY), described in U.S. Patents 4,388,277 and 4,524,051, with titania. The monolith can be impregnated with organic compounds o' Ti (such as a titanium tetraalkoxide), hydrolyzed, dried and calcined. Or the monolith can be impregnated with a dispersion of titania particles, followed by drying and calcining.
In the presently more preferred embodiment of this invention, a mon~lith is impregnated with a colloidal dispersion (colloidal solution) of titania in step (A). Preferably, colloidal particles of titania having an aYerage particle diameter of about 1 to about 100 nanometers, more preferably about 5 to about 20 nanometers, are dispersed in any suitable liquid dispersion medium, such as water, alcohols, ketones and the like, preferably water. Generally, the concentration of TiO2 in the colloidal dispersion is in the range of from about 0.1 to about 50, preferably from about 5 to about 25, weight percent TiO2. The weight ratio of colloidal dispersion of TiO2 to monolith material in step (A) is chosen so as to provide a TiO2 content of the material obtained in step (B) in the range of from about 1 to about 4Q weight-% TiO2, preferably about 5 to about 30 weight-l~ TiO2.
The impregnation of the titania-containing support ma-terial with Pt and/or Pd (preferably Pt) in steps (a) and ~c), respectively, can be carried out in any suitable manner. ~irst, compounds of Pt and/or Pd are dissolved in a suitable solvent (preferably water) so as to prepare solutions of suitable concentration, generally containing from about 0.005 to about 0.20, preferably about 0.01 to about 0.1, g Pt and/or Pd per cc of solution. Non-limiting examples of suitable compounds of Pt and Pd are: PtCl2, PtCl4, H2PtCl6, PtBr4, Pt(NH3)4cl2~ PtlNH3)~(~03)2 ~ ~193~ 323l4rA~
and the like; PdC12, PdCl4, H2PdCl6, Pd(NH3)4(NO3)2 and the like;
preferably (at present) Pt(NH3)4(NO3)2 and Pd(NH3)4(N03)2. The TiO2-containing support material is then impregnated by soaking it in the solution of Pt and/or Pd compounds; or (less preferably) the Pt and/or Pd containing solution is sprayed onto the support material. The ratio of Pt and/or Pd containing solution to support material generally is such that the final catalyst obtained in step (c) or, alternatively, the coating of the material obtained in (~), i.e., the material obtained in step (E) excludi~g the monolith, contains about 0.5 to about 5, preferably about 1 to about 3, weight-~ Pt or Pd. When a solution containing both Pt and Pd compounds, the level of Pt and Pd generally is about 0.5 to about 5, preferably about 1 to about 3, weight percent (Pt+Pd).
In a preferred embodiment, at least one compound of a metal selected from the group of Re, Fe, Ru, Cu and Ag, more preferably Fe, is also present as a copromoter in the impregnating solution (besides Pt and/or Pd). Non-limiting examples of suitable Fe compounds that can be used as solutes are FeCl2, FeCl3, Fe2(S04)3, Fe(N03)2, Fe(N03)3 and the like, preferably compounds of Fe in the valence state ~3, more preferably Fe(~03)3. Non-limiting examples of Nn compounds are MnCl2, MnS04, MntNO3)2, KMnO4, and the like. Non-limiting examples of Ru compounds are RuCl3, RuE4, Ru~NH3)6Cl3, KRu04, and the like. Non-limiting examples of Cu compounds are CuC12, Cu~NO3)2, GuS04, Cu(II) acetate, ammine complexes of the above Cu salts, and the like. Non-limiting examples of Ag compounds are AgF, AgN03, Ag2S04, Ag acetate, ammine complexes of the above Ag salts, and the like.
Cenerally, the concentration of the copromoter compound (expressed as metal) is in the ran8e of from about 0.01 to about 0.4, preferably about 0.02 to about 0.2, g metal (i.e., Mn or Fe or Ru or Cu or Ag or mixtures thereof) pex cc solution. When a mixture of copromoter compounds is used, e.g., a mixture of compounds of Fe and Ru, Fe and Ag, Ru and Cu, Fe/Ru/Ag, and the like, the total concentration of copromoter metals is about 0.02-0.8 g/cc. The impregnation of the support material with Pt and/or Pd and the copromoter method can be carried out either by sequential impregnation (first Pt and/or Pd, then copromoter) or by 13 ~ 9 3 ~ ~ 32314CAC
simultaneous impregnation in step (a) or, alternatively, step (C~ (using a solution containing Pt and/or Pd compounds and at least one copromoter compound).
When sequential impregnation is employed, the impregnation with a solution of at least one copromoter compound is carriPd out after heating step (b) and before step (c); or, if applicable, after heating step (D) and before step (E). Thus, an impregnating step (a*) with at least one dissolved copromoter compound and heating step (b*) [carried out in substantially the same manner as step (b)] are performed after step (b) and before step (c). Similarly, an impregnation atep (~') ~ith at least one dissolved copromoter compound and heating step (D*) [carried out in substantially the same manner as step (D)] are performed after step (D) and before step (E). The ratio of copromoter containing solution to support material is such as to provide a level of about 0.2 to about 4, preferably about 0.5-2, weight percent copromoter metal ~i.e., Re or Fe or Ru or Cu or Ag, or mixtures of two or more metals, (e.g., Fe/Ag, and the like) on the material obtained in step (c) or, alternatively, on the material obtained in step (~) excluding the monolith.
Preferably compounds of Cr, Mn and Zn should be substantially absent from the impregnating solutions used in impregnation steps (a), (a~), (C) and (C~) since these compounds have a detrimental effect on the activity for C0 oxidation of the finished catalyst.
Heating step (b) is generally carried out in an inert or oxidizing atmosphere, preferably a free oxygen containing gas atmosphere (such as air), generally at a temperature ranging from about 30 to about 700C. Preferably, heating step tb) is carried out in tWQ sequential sub-steps: sub-step (bl), at about 3a to about 200C (preferably at 30-130C~, generally for about 0.5 to about 10 hours, so as to substantially dry the impregnated material obtained in step (a) (preferably under such conditions as to reduce the level of adhered and accluded water to less than about 20 weight-~O)j and sub-step (b2), at about 300 to about 700C (preferably about 400 to about 600C), generally for about 1 to about 20 hours, under such conditions as to substantially calcine the impregnated support material so as to obtain oxides of Pt 131936~ 32314CAC
and/or Pd, on titania. When compounds of Re, Fe, Ru, Cu or Ag or mixtures thereof have been present in the Pt and/or Pd-containing impregnating solution, gene-rally oxides of Re, Fe, Ru, Cu and/or Ag are formed in step (b2).
Drying sub-steps (b~l), (Dl~ and (D*l), described above, are carried out at conditions which are essentially the same a~ ths~e described for sub-step (bl). And calcining sub-steps (b*Z) 7 (D2) and (D-~2), described above, are carried out at conditions which are essentially the same as those described for sub-step (b2) Reducing step (c) can be carried out in any suitable manner at a temperature in the range of from about 300 to about 800C, preferably rom about 350 to about 500~C. Reducing step (~) can be carried out in any suitable manner at a temperature in the range of from about 0 to about 300C, preferably about 20 to about 200C. Any reducing gas can be employed in reducing steps (C) and (E~, such as a gas comprising H2, C0, gaseous hydrocarbons such as methane, mixtures of the above, and the like. Preferably, a free hydro~en containing gas, more preferably sub~tantially pure H2, is employed. Reducing steps (c) and (E) can be carried out for any suitable period of ~ime suitable to activate the calcined material obtained in the previous step, preferably from about 0.5 to about 20 hours.
The process for oxidizing a carbon monoxide containing feed gas can be carried at any suitable temperature and pressure conditions, for any suitable length of time, at any suitable gas hourly space velocity, and any suitable volume ratio of C0 and 2 The reaction temperature generally is in the rang eof from about 0 to about 400C, preferably about 0 to about 100C, more preferably from about 10 to about 50C, most preferably about 20-4aoc. The pressure during the oxidation process generally is in the range of from about 1 to about 2,000 psia, more preferably from about 5 to about 20 psia. The volume ratio of C0 to 2 in the feed gas can range from about 1:100 to about 100:1, and preferably is in the range of about 1:10 to about 10:1. The volume percentage of C0 and the volume percentage of f 2 in the feed gas can each be in the range of from about 0.05 to about 50, preferably from about 0.5 to about 3. The gas hourly space velocity (cc feed gas per cc catalyst per hour) 13~936~ 32314ChC
can be in the range of from about 0.5 to about 10,000, preferably from about 1 to about 1,000. It is understood that the calculation of the ~a~
hourly space velocity is based on the volume of the active catalyst i.e , the titania-supported Pt and/or Pd catalyst toptionally also contaiuing copromoter), excluding the volume occupied by any additional ~upport material, such as a monolith material.
The feed gas can be formed in any suitable manner, e g., by mixing C0, 2 and optionally other gases such as CO2, N2~ He and the like, such as in a carbon dioxide laser cavity. Or the feed gas can be an exhaust gas from a combustion engine, or it can be air that is to be inhaled by humans and contains undesirable levels of toxic carbon monoxide, and the like. The feed gas can be contacted in any suitable vessel or apparatus, such as in a laser cavity or in an exhaust pipe of a combustion engine, or in a gas mask used by humans, wherein the feed gas passes over the catalyst composition of this invention at the conditions described above. The CO oxidation process of this invention can be carried out in any suitable setting and for any purpose, e.g., for recombining C0 and 2 in CO2 lasers, to oxidize CO contained in exhaust gases or air, to make isotopically labeled CO2 from CO and the 1~o isotope, and the like.
The following examples are presented in further illustration of the invention and are not to be construed as unduly limiting the scope of the invention.
Example I
This example illustrates the experimental setup for testing the activity of noble metal catalysts for catalyzing the oxidation of carbon monoxide (so as to simulate catalytic recombination of C0 and 2 in CO2 lasers). A gaseous feed blend comprising C0, 2, ~le and ~2 was passed through a needle valve and a glass reactor in an upflow direction. The glass reactor tube had an inner diameter of about 6 mm and generally contained about 1.0 gram catalyst in a bed of about 2.5 cm height. The temperature in the catalyst bed was measured by means of a thermocouple inserted into the top layer of the catalyst bed. The CO content in the reactor effluent was determined by means of a Beckman Model 864 IR
analyzer.
131936~ 32314CAC
All tests were carried out at ambient conditions. Generally the temperature in the catalyst bed rose to about 30C because of the generation of hPat during the 50 oxidation tests. The feed rate of the gaseous feed stream generally was in the range of about 4-300 cc/minute.
Example II
This example illustrates the preparation of titania-supported catalyst compositions and their performance in CO oxidation testg.
Catalyst A1 con-tained 1 weight-% Pt on TiO2 ~t was prepared by mixing, a~ room temperature, 30 g of flame-hydrolyzed titania (provided by Degussa Corporation, Teterboro, NJ; having a B~T/N2 surface area of about 50 m2/g) with 31 cc of aqueous chloroplatinic acid solution, which contained 0 0096 g Pt/cc solution, and enough distilled water to form a thick paste After impregnation, Catalys~ Al was dried at about 125C for several hours and calcined in air at about 350C for about 6 hours Catalyst Al was then pretreated with hydrogen gas for about 4 hours at various temperatures (range: 200-725C) Samples of catalyst A1 (1% Pt/TiO2) that had been pretreated with H2 at different temperatures was tested at room temperature (about 27GC) in the C0 oxidation unit described in E~ample I. The gaseous feed blend contained 1.2 volume-~/O C0, 0.6 volu~e-/O 2~ 40.7 volume-% N2 and 57.5 volume-% He. The feed rate was 10 cc/minute. The ~orrelation between C0 conversion and the temperature of the hydrogen pretreatment temperature of Catalyst Al is shown in Figure 1. Figure 1 shows that H2 pretreatment of the Pt/TiO2 catalyst at temperatures in the range of 400 to 725C resulted in a considerably more active C0 oxidation catalyst than H2 pretre~tment at 200C.
Catalyst A2 contained 1 weight-l~ Pt and 0 3 weight-b Pd on TiO2, and was prepared by mixing 30 g Catalyst Al with 100 cc of an aqueous solution containing 0.25 g tetramminepalladinum(II) nitrate, drying and calcining the obtained paste as described for Catalyst Al.
The calcined Catalyst A~ material was then activated by heating with H2 at 725C for 16 hours C0 conversion tmeasured as described for the tests employing Catalyst A1) was 100% for about 126 hours. Thus, Pd enhanced the C0 o~idation activity of the Pt/TiO2 catalyst.
3 1 9 ~ 6 ~ 32314CAC
~xample III
This example illustrates the effects of various other copromoters on the C0 oxidation activity of a Pt/TiO2 catalyst which contain~d 2 weight-% Pt (labeled Catalyst Bl) and was prepared substantially in accordance with the procedure for Catalyst Al, e-~cept that the Pt concentration in the impregnating solution was thrice as high, and the TiO2 support material was provided by Calsicat (division of Mallinckrodt, Inc., St. Louis, MO) and had a BET surface area sf about 40-170 m2/g.
Catalyst Bl was then mixed with aqueous solutions containing different metal compounds so as to provide a copromoter level of 0.8 weight-% of the metal. A solution of tetramminepalladinum(II) nitrate was used to make Catalyst B2 (0.8% Pd/2% Pt/TiO2~. A solution of Ru~13 3H20 was used to make Catalyst B3 (0.8% Ru/2% Pt/Ti2) A
solution of ReCl3 was used to make Catalyst B4 (0.8% Re/2% Pt/TiO2). A
sGlution of hexamminechloroiridium(II) dichloride was used to make Catalyst B5 (0.8% Ir/2% Et/TiO2~. A solu~ion of Cu(N03)2 2.5H20 was used to make Catalyst B6 (0.8b Cu/2% Pt/TiQ2). A solution of Fe(N03) 9H20 was used to make Catalyst B7 (0.8% Fe/2/O Pt/TiO2).
C0 conversions attained at room temperature (about 27C) in the test unit of Example I employing a gas ieed containing 1.2 volume-% CO, 0.6 volume-/O 2, 48 volume-/O N2 and He as the balance (flow rate of feed:
10 cc/minute), are shown for Catalysts B1, B2, B3, B4, B5, B6 and B7 in Figure 2. All catalysts had been pretreated with hydrogen gas for 3 hours at 600C.
The graphs in Figure 2 indicate that Fe, Pd, Re, Ru and Cu consistently enhanced the C0 oxidation activity of the Pt/TiO2 base catalyst, whereas Ir enhanced the C0 oxidation ac-tivity of the base catalyst only up to 60 hours on stream. Additional test data (not shown in Figure 2~ indicated that Rh did not affec~ the catalytic activity of the PtlTiO2 base catalyst. Fe, Pd and Re were the most effective copromoters for the Pt/TiO2-containing C0 oxidation catalyst.
In another test series, a TiO2-supported catalyst containing 0.4 weight-h Fe and 2.0 weight-b Pt, labeled Catalys-t B8, was prepared substantially in accordance with the procedure for Catalyst B7 t except ~ 3 ~ 32~14CAC
for a lower Fe level. Catalyst B8 was then impregnated tlith an aqueo~s solution containing a compound of a third promoter metal, so as to obtain Catalysts _ , Bl0, Bll and B12, respectively, containing 0.1 weight % o~
the following third promoter elements: Mn, Cr, Ag and Zn. Carbon 5 monoxide conversions, attained by Catalysts B8, B9, B10 and Bll at room temperature (about 27C) in the test unit of Example I employing the gas feed described in Example II are shown in Figure ~. The gas feed rate was 60 cc/minute (in lieu of 10 cc/minute). All catalysts had been pretreated in hydrogen gas for 3 hours at about 500C. The TiO2 support had been heated in H2 for about 48 hours at 500C before impregnation with the promoters (Fe, Pt ~ third promoter) for removal of traces of sulfur in TiO2.
The graphs in Figure 3 indicate that Ag enhanced the activity of the Fe~Pt/TiO2 C0 oxidation catalyst, whereas the presence of Mn, Cr and Mn was detrimental. Based on these test results, it is concluded that Ag i5 also an effective promoter for a Pt/TiO2-containing catalyst (with or without Fe).
Example IV
This example illustrates a preferred feature of the preparation of TiO2-supported Pt catalysts useful for C0 oxidation at low temperature. Two catalysts containing 0.5 weight-% Fe, and 2.0 weight-%
Pt on Calsicat TiO2 support were tested. Catalyst Cl was prepared substantially in accordance with the preparation of Catalysts B7 and B8, using an aqueous solu-tion of chloroplatinic acid. Catalyst C2 was prepared as described above except that the dissolved Pt compound was te~rammineplatinum(II) nitrate. The two catalysts were dried, calcined and pretreated with hydrogen gas at 500C for about 3 hours, as has been described in ~xamples II and III.
The two catalysts were tested at room temperature (about 26C) in the C0 oxidation test unit described in E~ample I, employing the gas feed described in Example III. The gas ~eed rate was 120 cc/minute.
Test results are summarized in Table I.
13~936B 3Z~14CAC
Table I
Hours on % C0 cclMinute Catalyst Stream Converted C0 Con~erted Cl 2 60 ~.84 6 56 0 7~
1~ 56 0.78 1~ 55 0.77 ~0 55 0.77 301 50 0.70 ~0 401 44 0.62 C2 2 63 0,89 6 70 0.98 78 1.09 89 1.25 94 1.3Z
92 1.30 92 1.3 1.2 91 1.27 ~0 lTemperature had dropped to 23C.
Test results in Table I clearly show that the Fe/Pt/TiO2 catalyst prepared using a chloride-free Pt compound for impregnation (Catalyst C2) was consistently more active for C0 oxidation than Catalyst Cl, which had been prepared using a chloride-containing Pt compound for impregnation.
Example V
This example illustrates how the C0 oxidation activity of a TiO2-supported catalyst can be enhanced by pretreatment of the TiO2 support.
25 grams of flame-hydrolyzed titania (provided by Degussa Corporation; see Example II) was stirred overnight in a mixture of ~00 cc concentrated H2SO~ and 300 cc deionized water. The aqueous slurry of titania was then neutralized wi~h a concentrated ammonia solution. The -dispersed titania was allowed to settle, and the supernatant solution was decanted. The thus treated titania was washed four times with deioni~ed water and dried in a circulating air oven (80-90C; 5 hours3.
S grams of the acid-treated TiO2 was impregnated with 3 cc of an aqueous solution of Pt(NH3)4(NO~)2 (containing 0.033 g Pt per cc) and 13193~ 32314CAC
then with 2.5 cc of an aqueous solution of Fe(~03)3 ~containing ~ 01 g ~e per cc~. The thus impregnated material was dried, calci~ed and pretreated with hydrogen gas for 3 hours at 500C. This catalyst, labeled Catalyst D, contained 2 weight-~ Pt and 0.5 weight-% Fe Catalyst D was compared to Catalyst C2 (see ~xa~ple IY; also containing 2 weight-% ~e on TiO2) which had been prepared without acid treatment of titania (provided by Degussa Corporation). The two catalysts were tested at room temperature (27-29gC) in the C0 o~idation test unit described in Example I, employing the gas feed described in ~xample III. Test results are summarized in Table II.
Table II
Gas Feed Hours on % C0 cc/Minute CatalystRate (cc/min.) Stream ConvertedC0 Converted -D 160 2 58 1.09 15 (TiO2 Support " 4 65 1.22 Acid-Treated) " 6 68 1.28 " 10 68 1.28 " 14 68 1.28 " 18 67.5 1.26 " 22 67.5 1.26 C2 120 2 56 ~.79 (TiO2 Support " 4 48 0.67 Not Acid-Treated) " 6 43 0.60 " 10 41 0.58 25" 14 41 0.58 " 18 ~2 0.59 Data in Table II clearly indicate that the C0 conversion was greater for Catalyst D as compared to Catalyst C2 in spite of the higher gas feed rate of the run with Cataly~t D. The conversion of C0, expressed in cc C0 converted per minute, attained by Catalyst D was about twice that attained by Catalyst C2.
Thus, in the presently preferred catalyst preparation method of this invention, the TiO2 support material is treated with an aqueous acid solution, followed by neutralization and washing, before the TiO2 support material is impregnated with promoters, dried, calcined and heated in H~
gas.
16 1~93~
~xample VI
This example illustrates the use of honeycomb ceramic catalyst supports, called monoliths, for preparing Pt/TiO2-containing catalysts employed in the oxidation of carbon monoxide. The two best modes of preparation of these honeycomb catalysts are described in this example.
Mode A: A round piece of Celcor~ Cordierite #9475 monolith ceramic material 2MgO 2Al203 5SiO2; provided by Corning Glass Works, Corning, NYi diameter: 1 inch; height 1 inch; having 100 cells per square inch) was dried for 2 hours at 185C, and was then dipped about 7 times into a stirred suspension of 30 grams flame-hydrolyzed TiO2 (Degussa Corporation) in 250 cc distilled water. The material was dried a$ter each dipping. This TiO2-coated monolith material was calcined in air for 4 hours at 500C. The calcined TiO2-coated monolith material was then dipped into an aqueous solution of chloroplatinic acid (containing 0.022 g Pt/cc), dried for 1 hour at 300C, dipped into an a~ueous solution of Fe~N03)3 (containing O.Ol g Fe/cc) and dried again for 1 hour at 300C. The Fe/Pt/TiO2/monolith catalyst, labeled Catalyst El, was pretreated in hydrogen gas for 3 hours at 500~C and then heated in helium gas at that temperature for 30 minutes. The impregnation with Pt and Ee, drying and pretreating with H2 was repeated.
Catalyst El was tested in a C0 oxidation apparatus at room temperature (about 26C) in an apparatus similar to the one described in Example I, except that a glass reactor tube of l inch inner diameter was used. The $eed gas employed was essentially the same as the one described in Example III. Test results are summarized in Table III.
1 ~19~ 323~4CA~
Table III
Hours on Gas Feed % C0 cc/Minute Stream Rate (cc/min.)ConversionC0 Converted 4 10 99 O.lZ
99 0.12 96 0.34 24 30 96 ~.34 g1 0.64 0.56 72 0.50 66 0.46 5~ 0.41 0.42 58 0.41 100 60 56 0.40 ~10 60 55 0.38 Mode B: The presently best mode for preparing honeycomb-type Pt/TiO2-containing catalysts is as follows. A piece of Cordierite 9475 monolith material (diameter: 1 inch; height: 1 inch) was dipped into a colloided solution of TiO2 in water (provided by Nalco; containing about 6 weight-~ TiO2 having an average particle diameter of ~ microns). The monolith piece was dipped 9 times into the colIoidal TiO2 solution. The thus impregnated piece was dried at 150C after each dipping. The TiO2-coated monolith was then dipped into an aqueous Pt(~H3)~(N~3)2 solution (containing 0.33 g/cc Pt), dried, calcined in air for 2 hours at 300C, and pretreated in H2 gas after 1 hour at room temperature (25C).
The coating of the thus-prepared catalyst, labeled Catalyst E2, contained about 3 weight-% Pt and about 97 weight-% TiO2.
~ y~ was prepared by dipping E2 into an aqueous solution of Fe(N03)3 (containing 0.01 g Fe per cc), drying, calcining in air for 2 hours at 300C, and pretreating in H2 for 1 hour at room temperatnre.
The coating of Catalyst E2 contained about 3 weight-~ Pt, about 1 weight-% Fe and 96 weight-% TiO2.
Catlayst E4 was prepared by dipping E3 into an aqueous solution of Pd~NH3)4(N03~2 (containing 0.04 g Pd per cc), calcining in air for 2 hours at 300C, and pretreating with H2 for 1 hour at room temperature.
Catalysts E2, E3 and E4 were tested in the experimental setup described for the C0 oxidation run employing Catalyst E1. The gas feed ~3~93~ 32314CAC
rate for all runs was 300 cc/minute. Test results are summarized in Table IV.
Table IV
Hours on /~ C0 cc/Minute Catalyst S~ream Conversion C0 Converted E2 1 9.4 0 33 2 8.5 0.30 4 4.3 0 15 2 6g 2 43 6 69 2.43 1.92 14 47 1.65 33 1.17 Test results in Table IV indicate that high C0 conversions (cc C0/minute) were attained at high gas feed rates (300 cc/minute; higher than in any previous run). Thus the monolith-supported catalysts E2-E4, prepared by impregnation with colloidal TiO2, are considered the presently best TiO2-supported C0 oxidation catalysts.
A run not listed in Table IV employing a catalyst similar to Catalyst E3, except that 0.6 weight-% Mn was prepared in the coating in lieu of 1 weight-% Fe, gave C0 conversions of only about 33% and about 1.2 cc CO/minute during the first 5 hours. Thus, Mn/Pt/TiO2 catalysts are not considered more preferred catalysts of this invention.
A particular advantage of the monolith-supported Pt/TiO2-containing catalysts E2-E4 is that they could be activated by pretreatment in H2 at a low temperature (about 25C), whereas the catalysts used in previous examples required pretreatment in H2 at an elevated temperature (e.g., 400-500C). In fact, reheating Catalyst E4 ~3193~ 32314CAC
for 3 hours in air at 500C and then for 1 hour in hydrogen at 400C ~ade this catalyst substantially inactive for C0 oxidation.
Example VII
A test employing a catalyst, which contained 1 wei~ht-% Pt on SiO2 and had been pretreated in H2 at 660C for about 1 hour, showed no activity for catalyzing the oxidation of C0 at room temperature. Thus, SiO2 should be substantially absent from the ca-talyst of this invention.
Reasonable variations t modifications and adaptations for various usages and conditions can be made within the scope of the disclosure and the appended claims, without departing from the scope of this invention.
Claims (87)
1. A composition of matter consisting essentially of (i) a support material consisting essentially of titania, (ii) platinum metal and (iii) iron oxide, wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C, and said composition of matter contains components (ii) and (iii) in amounts such that said iron oxide is effective as copromoter for said platinum metal on said support material in said oxidation at about 10°-50°C.
2. A composition of matter in accordance with claim 1 comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe.
3. A composition of matter in accordance with claim 2 comprising about 1-3 weight-% Pt.
4. A composition of matter in accordance with claim 1 having been prepared by a process comprising the steps of:
(a) contacting titania with a solution comprising at least one dissolved compound of platinum and at least one dissolved compound of iron;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron at least one oxide of iron; and (c) heating the material obtained in step (b) in a reducing gas atmosphere at a temperature in the range of from about 300° to about 800°C, under such conditions as to form said composition of matter.
(a) contacting titania with a solution comprising at least one dissolved compound of platinum and at least one dissolved compound of iron;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron at least one oxide of iron; and (c) heating the material obtained in step (b) in a reducing gas atmosphere at a temperature in the range of from about 300° to about 800°C, under such conditions as to form said composition of matter.
5. A composition of matter in accordance with claim 4, wherein said reducing gas atmosphere is a free hydrogen containing gas.
6. A composition of matter in accordance with claim 4, wherein step (c) is carried out in a stream of H2 at a temperature in the range of from about 350° to about 500°C, for a period of time in the range of from about 0.5 to about 20 hours.
7. A composition of matter in accordance with claim 4, wherein step (b) is carried out in two sub-steps:
(b1) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein step (c) is carried out with the material obtained in step (b2).
(b1) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein step (c) is carried out with the material obtained in step (b2).
8. A composition of matter in accordance with claim 7, wherein said first temperature is in the range of from about 30° to about 200°C, and said second temperature is in the range of from about 300° to about 700°C.
9. A composition of matter in accordance with claim 4, wherein said titania has been treated with an acid solution prior to step (a).
10. A composition of matter in accordance with claim 1, having been prepared by a process comprising the steps of:
(a) contacting titania with a solution comprising at least one compound of platinum;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a) and to at least partially convert said at least one dissolved compound of platinum to at least one oxide of platinum;
(a*) impregnating the material obtained in step (b) with a solution comprising at least one dissolved compound of iron;
(b*) heating the material obtained in step (a*) under such conditions as to substantially dry said material obtained in step (a*), and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (c) heating the material obtained in step (b*) in a reducing gas atmosphere at a temperature in the range of from about 300° to about 800°C, under such conditins as to form said composition of matter.
(a) contacting titania with a solution comprising at least one compound of platinum;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a) and to at least partially convert said at least one dissolved compound of platinum to at least one oxide of platinum;
(a*) impregnating the material obtained in step (b) with a solution comprising at least one dissolved compound of iron;
(b*) heating the material obtained in step (a*) under such conditions as to substantially dry said material obtained in step (a*), and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (c) heating the material obtained in step (b*) in a reducing gas atmosphere at a temperature in the range of from about 300° to about 800°C, under such conditins as to form said composition of matter.
11. A composition of matter in accordance with claim 10, wherein said reducing gas atmosphere is a free hydrogen containing gas.
12. A composition of matter in accordance with claim 10, wherein step (c) is carried out in a stream of H2 at a temperature in the range of from about 350° to about 500°C, for a period of time in the range of from about 0.5 to about 20 hours.
13. A composition of matter in accordance with claim 10, wherein step (b) is carried out in two sub-steps:
(b1) heating the material in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
wherein step (b*) is carried out in two sub-steps:
(b*1) heating the material obtained in step (a*) at a first temperature so as to remove substantially all liquids from said material obtained in step (a*), and (b*2) heating the material obtained in step (b*1) at a second temperature, which is higher than said temperature, so as to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein said step (c) is carried out with a material obtained in step (b*2).
(b1) heating the material in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
wherein step (b*) is carried out in two sub-steps:
(b*1) heating the material obtained in step (a*) at a first temperature so as to remove substantially all liquids from said material obtained in step (a*), and (b*2) heating the material obtained in step (b*1) at a second temperature, which is higher than said temperature, so as to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein said step (c) is carried out with a material obtained in step (b*2).
14. A composition of matter in accordance with claim 13, wherein said first temperature is in the range of from about 30°C to about 200°C, and said second temperature is in the range of from about 300° to about 700°C.
15. A composition of matter in accordance with claim 10, wherein said titania has been treated with an acid solution prior to step (a).
16. A composition of matter consisting essentially of (i) a support material consisting essentially of titania-coated porous ceramic material, (ii) platinum metal, and (iii) iron oxide, wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C, and said composition of matter contains components (ii) and (iii) in amounts such that said iron oxide is effective as copromoter for said platinum metal on said support material in said oxidation at about 10°-50°C.
17. A composition of matter in accordance with claim 16 wherein said titania-coated porous ceramic material is a titania-coated monolith material.
18. A composition of matter in accordance with claim 17, comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe, based on the weight of said composition of matter excluding said monolith.
19. A composition of matter in accordance with claim 16, comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe, based on the weight of said composition of matter excluding said ceramic material.
20. A composition of matter in accordance with claim 16, wherein said titania-coated porous ceramic material contains about 1 to about 40 weight-% TiO2.
21. A composition of matter in accordance with claim 16, wherein said titania-coated porous ceramic material is a titania-coated monolith material and comprises about 1 to about 40 weight-% TiO2.
22. A composition of matter in accordance with claim 16, having been prepared by a process comprising the steps of:
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum and at least one dissolved compound of iron;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C), to at least partially convert said at least one compound platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (E) heating the material obtained in step (D) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C, under such conditions as to form said composition of matter.
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum and at least one dissolved compound of iron;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C), to at least partially convert said at least one compound platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (E) heating the material obtained in step (D) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C, under such conditions as to form said composition of matter.
23. A composition of matter in accordance with claim 22, wherein said porous ceramic material is a monolith material.
24. A composition of matter in accordance with claim 22, wherein said reducing gas atmosphere is a free hydrogen containing gas.
25. A composition of matter in accordance with claim 22, wherein step (E) is carried out in a stream of H2 at a temperature in the range of from about 20° to about 200°C, for a period of time in the range of from about 0.5 to about 20 hours.
26. A composition of matter in accordance with claim 22, wherein said colloidal dispersion used in step (A) contains titania particles having an average particle diameter in the range of from about 1 to about 100 nanometers, and said liquid dispersion medium is water.
27. A composition of matter in accordance with claim 22, wherein said colloidal dispersion used in step (A) comprises about 0.1-50 weight-% TiO2.
28. A composition of matter in accordance with claim 22, wherein step (D) is carried out in two sub-steps:
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein said step (E) is carried out with the material obtained in step (D2).
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, and to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein said step (E) is carried out with the material obtained in step (D2).
29. A composition of matter in accordance with claim 28, wherein said first temperature is in the range of from about 30° to about 200°C, and said second temperature is in the range of from about 300° to about 700°C.
30. A composition of matter in accordance with claim 16, having been prepared by a process comprising the steps of:
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C) and to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
(C*) impregnating the material obtained in step (D) with a solution comprising at least one compound of iron;
(D*) heating the material obtained in step (C*) under such conditions as to substantially dry said material obtained in step (C*), and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (E) heating the material obtained in step (D*) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C, under such conditions as to form said composition of matter.
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C) and to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
(C*) impregnating the material obtained in step (D) with a solution comprising at least one compound of iron;
(D*) heating the material obtained in step (C*) under such conditions as to substantially dry said material obtained in step (C*), and to at least partially convert said at least one compound of iron to at least one oxide of iron; and (E) heating the material obtained in step (D*) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C, under such conditions as to form said composition of matter.
31. A composition of matter in accordance with claim 30, wherein said porous ceramic material is a monolith material.
32. A composition of matter in accordance with claim 30, wherein said reducing gas atmosphere is a free hydrogen containing gas.
33. A composition of matter in accordance with claim 30, wherein step (E) is carried out in a stream of H2 at a temperature in the range of from about 20° to about 200°C, for a period of time in the range of from about 0.5 to about 20 hours.
34. A composition of matter in accordance with claim 30, wherein said colloidal dispersion used in step (A) contains titania particles having an average particle diameter in the range of from about 1 to about 100 nanometers, and said liquid dispersion medium is water.
35. A composition of matter in accordance with claim 30, wherein said colloidal dispersion used in step (A) comprises about 0.1-50 weight-% TiO2.
36. A composition of matter in accordance with claim 30, wherein step (D) is carried out in two sub-steps:
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
wherein step (D*) is carried out in two sub-steps:
(D*1) heating the material obtained in step (C*) at a first temperature so as to remove substantially all liquids from said material obtained in step (C*), and (D*2) heating the substantially dried material obtained in step (D*1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein step (E) is carried out with the material obtained in step (D*2).
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum;
wherein step (D*) is carried out in two sub-steps:
(D*1) heating the material obtained in step (C*) at a first temperature so as to remove substantially all liquids from said material obtained in step (C*), and (D*2) heating the substantially dried material obtained in step (D*1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of iron to at least one oxide of iron;
and wherein step (E) is carried out with the material obtained in step (D*2).
37. A composition of matter in accordance with claim 36, wherein said first temperature is in the range of from about 30° to about 200°C, and said second temperature is in the range of from about 00° to about 700°C.
38. A composition of matter in accordance with claim 18, comprising about 1-3 weight-% Pt.
39. A composition of matter in accordance with claim 19, comprising about 1-3 weight-% Pt.
40. A composition of matter in accordance with claim 4, wherein said compound of platinum is Pt(NH3)4(N03)2.
41. A composition of matter in accordance with claim 10, wherein said compound of platinum is Pt(NH3)4(N03)2.
42. A composition of matter in accordance with claim 22, wherein said compound of platinum is Pt(NH3)4(N03)2.
43. A composition of matter in accordance with claim 30, wherein said compound of platinum is Pt(NH3)4(N03)2.
44. A composition of matter consisting essentially of (i) a support material consisting essentially of titania, (ii) platinum metal, and (iii) iron oxide;
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C, and said composition of matter contains components (ii) and (iii) in amounts such that said iron oxide is effective as copromoter for said platinum metal on said support material in said oxidation at about 10°-50°C;
wherein said support material (a) has been prepared by a process comprising the steps of extracting said titania with an aqueous acidic solution, treating the thus extracted titania with an alkaline solution, washing the thus alkaline-treated titania with water, drying the thus washed titania, and calcining the thus dried titania at a temperature of about 200°-800°C.
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C, and said composition of matter contains components (ii) and (iii) in amounts such that said iron oxide is effective as copromoter for said platinum metal on said support material in said oxidation at about 10°-50°C;
wherein said support material (a) has been prepared by a process comprising the steps of extracting said titania with an aqueous acidic solution, treating the thus extracted titania with an alkaline solution, washing the thus alkaline-treated titania with water, drying the thus washed titania, and calcining the thus dried titania at a temperature of about 200°-800°C.
45. A composition in accordance with claim 44, wherein said aqueous acidic solution is a sulfuric acid solution.
46. A composition of matter in accordance with claim 44, wherein said alkaline solution is an aqueous ammonia solution.
47. A composition of matter in accordance with claim 44, wherein said calcining is carried out for about 0.5-10 hours.
48. A composition of matter in accordance with claim 44, comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe.
49. A composition of matter in accordance with claim 48, comprising about 1-3 weight-% Pt.
50. A composition of matter consisting essentially of (i) a support material consisting essentially of titania, (ii) platinum metal, (iii) iron oxide, and (iv) a material selected from the group consisting of palladium metal and silver metal;
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C;
and said composition contains components (ii), (iii) and (iv) in amounts such that the component (iii) is a copromoter for component (ii) on said support material in said oxidation at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C.
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C;
and said composition contains components (ii), (iii) and (iv) in amounts such that the component (iii) is a copromoter for component (ii) on said support material in said oxidation at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C.
51. A composition of matter in accordance with claim 50 comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe.
52. A composition of matter in accordance with claim 51 comprising about 1-3 weight-% Pt.
53. A composition of matter in accordance with claim 50, wherein component (iv) is palladium metal.
54. A composition of matter in accordance with claim 50, wherein component (iv) is silver metal.
55. A composition of matter in accordance with claim 50 having been prepared by a process comprising the steps of:
(a) Contacting titania with a solution comprising at least one dissolved compound of platinum, at least one dissolved compound of iron, and at least one compound of additional element selected from the group consisting of palladium and silver;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound of iron to at least one oxide of iron, and to at least partialy convert said at least one compound of said additional element to at least one oxide of said additional element; and (c) heating the material obtained in step (b) in a reducing gas atmosphere at a temperature in the range of from about 300°C to about 800°C, under such conditions as to form said composition of matter.
(a) Contacting titania with a solution comprising at least one dissolved compound of platinum, at least one dissolved compound of iron, and at least one compound of additional element selected from the group consisting of palladium and silver;
(b) heating the material obtained in step (a) under such conditions as to substantially dry said material obtained in step (a), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound of iron to at least one oxide of iron, and to at least partialy convert said at least one compound of said additional element to at least one oxide of said additional element; and (c) heating the material obtained in step (b) in a reducing gas atmosphere at a temperature in the range of from about 300°C to about 800°C, under such conditions as to form said composition of matter.
56. A composition of matter in accordance with claim 55, wherein said reducing gas atmosphere is a free hydrogen containing gas.
57. A composition of matter in accordance with claim 55, wherein step (c) is carried out in a stream of H2 at a temperature in the range of from about 350° to about 500°C, for a period of time in the range of from about 0.5 to about 20 hours.
58. A composition of matter in accordance with claim 55, wherein step (b) is carried out in two sub-steps:
(b1) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound or iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element.
(b1) heating the material obtained in step (a) at a first temperature so as to remove substantially all liquids from said material obtained in step (a), and (b2) heating the substantially dried material obtained in step (b1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound or iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element.
59. A composition of matter in accordance with claim 58, wherein said first temperature is in the range of from about 30° to about 200°C, and said second temperature is in the range of from about 300° to about 700°C.
60. A composition of matter in accordance with claim 55, wherein said compound of platinum is Pt(NH3)4(NO3)2.
61. A composition of matter consisting of essentially of (i) a support material consisting essentially of titania, (ii) platinum metal, (iii) iron oxide, and (iv) a material selected from the group consisting of palladium metal and silver metal;
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to the carbon dioxide at about 10°-50°C; and said composition contains components (ii), (iii) and (iv) in amounts such that component (iii) is a copromoter for component (ii) on said support material at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C;
wherein said support material (i) has been prepared by a process comprising the steps of extracting said titania with an aqueous acidic solution, treating the thus extracted titania with an alkaline solution, washing the thus alkaline-treated titania with water, drying the thus-washed titania, and calcining the thus-dried titania at a temperature of about 200°-800°C.
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to the carbon dioxide at about 10°-50°C; and said composition contains components (ii), (iii) and (iv) in amounts such that component (iii) is a copromoter for component (ii) on said support material at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C;
wherein said support material (i) has been prepared by a process comprising the steps of extracting said titania with an aqueous acidic solution, treating the thus extracted titania with an alkaline solution, washing the thus alkaline-treated titania with water, drying the thus-washed titania, and calcining the thus-dried titania at a temperature of about 200°-800°C.
62. A composition of matter in accordance with claim 61, wherein said aqueous acidic solution is a sulfuric acid solution.
63. A composition of matter in accordance with claim 61, wherein said alkaline solution is an aqueous ammonia solution.
64. A composition of matter in accordance with claim 61, wherein said calcining is carried out for about 0.5-10 hours.
65. A composition of matter in accordance with claim 61 comprising 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe.
66. A composition of matter in accordance with claim 65 comprising 1-3 weight-% Pt.
67. A composition of matter in accordance with claim 61, wherein component (iv) is palladium metal.
68. A composition of matter in accordance with claim 61, wherein component (iv) is silver metal.
69. A composition of matter consisting essentially of (i) a support material consisting essentially of titania-coated ceramic material, (ii) platinum metal, (iii) iron oxide, and (iv) a material selected from the group consisting of palladium metal and silver metal;
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C; and said composition contains components (ii), (iii) and (iv) in amounts such that component (iii) is a copromoter for component (ii) on said support material in said oxidation at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C.
wherein said composition of matter is active as a catalyst for the oxidation of carbon monoxide with free oxygen to carbon dioxide at about 10°-50°C; and said composition contains components (ii), (iii) and (iv) in amounts such that component (iii) is a copromoter for component (ii) on said support material in said oxidation at about 10°-50°C, and component (iv) is a copromoter for the combination of components (ii) and (iii) on said support material in said oxidation at about 10°-50°C.
70. A composition of matter in accordance with claim 69, wherein said titania-coated porous ceramic material is a titania-coated monolith material.
71. A composition of matter in accordance with claim 70, comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe, based on the weight of said composition of matter excluding said monolith.
72. A composition of matter in accordance with claim 71, comprising about 1-3 weight-% Pt.
73. A composition of matter in accordance with claim 69 comprising about 0.5-5 weight-% Pt and about 0.2-4 weight-% Fe, based on the weight of said composition of matter excluding said ceramic material.
74. A composition of matter in accordance with claim 73 comprising about 1-3 weight-% Fe.
75. A composition of matter in accordance with claim 69, wherein said titania-coated porous ceramic material contains about 1 to about 40 weight-% TiO2.
76. A composition of matter in accordance with claim 69, wherein said titania-coated porous ceramic material is a titania-coated monolith material and comprises about 1 to about 40 weight-% TiO2.
77. A composition of matter in accordance with claim 69 having been prepared by a process comprising the steps of:
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum, at least one dissolved compound of iron, and at least one dissolved compound of an additional element selected from the group consisting of palladium and silver;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound of iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element; and (E) heating the material obtained in step (D) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C under such conditions as to form said composition of matter.
(A) impregnating a porous ceramic material with a colloidal dispersion of titania in a suitable liquid dispersion medium;
(B) heating the titania-coated material obtained in step (A) so as to obtain a substantially dried titania-coated porous ceramic material;
(C) contacting the material obtained in step (B) with a solution comprising at least one dissolved compound of platinum, at least one dissolved compound of iron, and at least one dissolved compound of an additional element selected from the group consisting of palladium and silver;
(D) heating the material obtained in step (C) under such conditions as to substantially dry the material obtained in step (C), to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said at least one compound of iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element; and (E) heating the material obtained in step (D) in a reducing gas atmosphere at a temperature in the range of from about 0° to about 300°C under such conditions as to form said composition of matter.
78. A composition of matter in accordance with claim 77, wherein said porous ceramic material is a monolith material.
79. A composition of matter in accordance with claim 77, wherein said reducing gas atmosphere is a free hydrogen containing gas.
80. A composition of matter in accordance with claim 77, wherein step (E) is carried out in a stream of H2 at a temperature in the range of from about 20° to about 200°C, for a period of time in the range of from about 0.5 to about 20 hours.
81. A composition of matter in accordance with claim 77, wherein said colloidal dispersion used in step (A) contains titania particles having an average particle diameter in the range of from about 1 to about 100 nanometers, and said liquid dispersion medium is water.
82. A composition of matter in accordance with claim 77, wherein said colloidal dispersion used in step (A) comprises about 0.1-50 weight-% TiO2.
83, A composition of matter in accordance with claim 77, wherein step (D) is carried out in two sub-steps:
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said compound of iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element.
(D1) heating the material obtained in step (C) at a first temperature so as to remove substantially all liquids from said material obtained in step (C), and (D2) heating the substantially dried material obtained in step (D1) at a second temperature, which is higher than said first temperature, so as to at least partially convert said at least one compound of platinum to at least one oxide of platinum, to at least partially convert said compound of iron to at least one oxide of iron, and to at least partially convert said at least one compound of said additional element to at least one oxide of said additional element.
84. A composition of matter in accordance with claim 83, wherein said first temperature is in the range of from about 30° to about200°C, and said second temperature is in the range of from about 300° to about 700°C.
85. A composition of matter in accordance with claim 77, wherein said compound of platinum is Pt(NH3)4(NO3)2.
86. A composition of matter in accordance with claim 69, wherein component (iv) is palladium metal.
87. A composition of matter in accordance with claim 69, wherein component (iv) is silver metal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9446787A | 1987-09-08 | 1987-09-08 | |
| US94,467 | 1987-09-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1319360C true CA1319360C (en) | 1993-06-22 |
Family
ID=22245364
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000576788A Expired - Fee Related CA1319360C (en) | 1987-09-08 | 1988-09-08 | Oxidation of carbon monoxide and catalyst therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1319360C (en) |
-
1988
- 1988-09-08 CA CA000576788A patent/CA1319360C/en not_active Expired - Fee Related
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4920088A (en) | Catalyst for the oxidation of carbon monoxide | |
| US4956330A (en) | Catalyst composition for the oxidation of carbon monoxide | |
| US4808394A (en) | Catalytic oxidation of carbon monoxide | |
| JP2911466B2 (en) | Exhaust gas purification catalyst for internal combustion engine, method for producing the same, and exhaust gas purification method | |
| US4818745A (en) | Catalyst for oxidation of carbon monoxide and process for preparing the catalyst | |
| CA1095012A (en) | Catalyst manufacture | |
| CA1252607A (en) | Method of simultaneous oxidation of carbon monoxide and unburned fuel in methanol vehicle exhaust | |
| CA1319671C (en) | Oxidation of carbon monoxide and catalyst composition therefor | |
| US4753915A (en) | Process for making a carrier-supported catalyst | |
| US4171289A (en) | Selective automotive exhaust catalysts and a process for their preparation | |
| US4921830A (en) | Catalyst for the oxidation of carbon monoxide | |
| CA2014559C (en) | Catalysts for oxidation of carbon monoxide | |
| US5759949A (en) | Supported cold-complex oxidation catalyst | |
| Papadakis et al. | Development of high performance, Pd-based, three way catalysts | |
| JPH06504940A (en) | Base metal oxide assisted rhodium-containing catalyst composition | |
| WO1997045192A1 (en) | Oxidation catalyst | |
| JPS594175B2 (en) | Nitrogen oxide removal using coated catalysts | |
| GB2234450A (en) | Low temperature oxidation catalysts | |
| US4940686A (en) | Catalyst for oxidation of carbon monoxide | |
| US6093670A (en) | Carbon monoxide oxidation catalyst and process therefor | |
| US4994247A (en) | Preparation of catalyst for oxidation of carbon monoxide | |
| USRE34655E (en) | Vehicle exhaust gas systems | |
| US20040048740A1 (en) | Tin oxide three-way catalysts stable at high temperatures | |
| CA1319360C (en) | Oxidation of carbon monoxide and catalyst therefor | |
| JP3251009B2 (en) | Exhaust gas purification catalyst |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20040622 |