Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Mixture is exhaust from internal-combustion engine
Patent
1988-03-10
1990-03-13
Russel, Jeffrey E.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Mixture is exhaust from internal-combustion engine
502310, B01D 5336
Patent
active
049081926
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to catalyst compositions primarily for use in the treatment of vehicle exhaust gas emissions to reduce the content of carbon monoxide and unburnt hydrocarbons, and thus to reduce pollution problems associated with vehicle exhausts.
However, whilst the invention will be particularly described hereinafter with reference to vehicle exhaust gas emissions, it is to be understood that the catalyst compositions described herein may well find other applications in the treatment of waste or other gases containing carbon monoxide, hydrocarbons and nitrogen oxides, alone or in combination, thereby to remove any or all of such components prior to disposal e.g. venting of the waste or other gas to the atmosphere.
BACKGROUND
Increasingly severe environmental regulations governing the emission of noxious gases into the atmosphere, and in particular, vehicle exhaust emissions, have stimulated a demand for catalysts active in the removal of such noxious components from the gases prior to disposal or venting to the atmosphere. In particular demand are 2- way and 3-way catalysts effective in removing carbon monoxide, unburnt hydrocarbons and/or nitrogen oxides from vehicle exhaust emissions, and this has led to the development of catalytic converters for attachment to vehicle exhaust gas emission systems to control the emission of carbon monoxide, unburnt hydrocarbons and/or nitrogen oxides to the atmosphere. Preferably such catalysts are active in the removal of all three, i.e. the so-called 3-way catalysts, but 2-way catalysts, or even 1-way catalysts do have some utility, not necessarily in the field of exhaust gas emissions, but in others.
PRIOR ART
Current commercial catalytic converters generally comprise one or more platinum group metals e.g. platinum, palladium, rhodium and rhenium, alone or in combination. Such converters tend therefore to be expensive. Attempts have been made either to reduce or eliminate altogether the dependence on platinum group metals in such systems. For example, in GB-A-2,070,958 an exhaust gas catalyst is disclosed comprising the combination of a platinum group metal and a base metal oxide selected from SnO.sub.2, TiO.sub.2 and NiMoO.sub.4 deposited on a monolithic ceramic support coated with a refractory metal oxide, e.g. alumina.
Numerous other patent applications and scientific papers have been published on the subject, with activity largely being centered on tin(IV) oxide, i.e. SnO.sub.2, as an essential catalyst component, alone or in combination either with platinum group metals, as already mentioned, or other base metal oxides, but the fact remains that the present commercially available or acceptable converters all employ a platinum group metal as a principal component. A non-exhaustive list of other relevant art relating to the use of tin(IV) oxide in the purification of exhaust or other waste gases is as follows:
Journal of Catalysis, 39 (1975), 412-418, Catalytic reduction of nitrous oxide by carbon monoxide over tin(IV) oxide;
Nature, 269 (1977), 585-586, Water-promoted oxidation of carbon monoxide over tin(IV) oxide-supported palladium;
Chemistry and Industry, (1976), 787-788, Catalysis of the NO--CO reaction: a further example of synergism in the Pd--SnO.sub.2 system;
Journal of Catalysis, 42 (1976), 418-424, Catalytic reduction of nitric oxide by carbon monoxide over SnO.sub.2 --CuO gels; see also J.C.S. Chem. Comm. (1973) 210 and J.C.S. Chem. Comm. (1974) 56-57;
Japanese published patent application 75-108169, Catalytic treatment of waste gases, including vehicle exhaust emissions, with ammonia in the presence of an SnO.sub.2 /Cr.sub.2 O.sub.3 catalyst to reduce nitrogen oxides;
USSR Patent No. 736,997, Carbon monoxide oxidation catalyst comprising SnO.sub.2 and Cr.sub.2 O.sub.3 ;
USSR Patent No. 691,185, Sulphur dioxide removal catalyst comprising SnO.sub.2 and Cr.sub.2 O.sub.3 ;
Prep. Catal. Proc. Int. Symp. 1975 (Published 1976) 197-206, Preparation and activation of tin(IV) oxide-chromium(III) oxide catalysts for nitric oxide
REFERENCES:
patent: 3951867 (1976-04-01), Howell
patent: 4003978 (1977-01-01), Shiraishi et al.
patent: 4208537 (1980-06-01), Kawamata et al.
patent: 4524051 (1985-06-01), Wright et al.
Bozso, F., Solymosi, F., "Oxidation of Ethylene, Ethylene Oxide and Propylene on SnO.sub.2 O--Cr.sub.2 O.sub.3 ", Symposium on the Mechanisms of Hydrocarbon Reactions 5-7, Jun., 1973, Siofoa, Hungary pp. 311-320.
Adsorption and Reduction of NO on Tin (IV) Oxide Doped with Chromium (III) Oxide, F. Solymosi et al, 11/11/77-pp. 42-51.
Chemical Abstracts, vol. 91, 1979, Abstract No. 97262b, "The Preparation and Activation of Tin (IV) Oxide-Chromium (III), Oxide Catalysts".
Chemical Abstracts, vol. 81, 1974, Abstract No. 175627j, "Removing Nitrogen Oxides from Waste or Exhaust Gases by Contacting with Ammonia in the Presence of Tin Oxide or Cerium Oxide".
"The Catalytic Reduction of Nitrous Oxide b y Carbon Monoxide OVer Tin (IV) Oxide"; M. J. Fuller and M. E. Warwick, Nov. 11, 1975, vol. 39, pp. 412-418.
"Water-Promoted Oxidation of Carbon Monoxide Over Tin (IV) Oxide-Supported Palladium"; E. P. Hincks et al, Oct. 13, 1977, vol. 269, pp. 585-586.
"Catalysis of the NO--CO Reaction: A further Example of Synergism in the PD-SNO System"; Martin J. Fuller et al; 1976, pp. 787-788.
"The Catalytic Reduction of Nitric Oxide by Carbon Monoxide SnO.sub.2 --CuO Gels"; J. J. Fuller et al; 8/4/75; vol. 42, pp. 418-424.
Harris Peter J. F.
Harrison Philip G.
Russel Jeffrey E.
TI Corporate Services Limited
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