KATALYTISCHES VERFAHREN

1446856 Support for I.C. engine exhaust gas catalyst coated products IMPERIAL CHEMICAL INDUSTRIES Ltd 6 Aug 1973 [18 Aug 1972 4 Oct 1972 20 Nov 1972 5 April 1973] 38622/72 45696/72 53493/72 and 16288/73 Headings B1E and B2E [Also in Division Cl] A support for an I.C. engine exhaust gas purification catalyst comprises a primary catalyst, support carrying on its surface a refractory unglazed secondary catalyst support comprising a mixture and/or compound of alumina and silica, at least 70% of which is in chemical combination with a basic oxide that is one or more of the oxides of calcium, strontium and barium, otherwise than as a hydraulic cement. The secondary support may contain the alkaline earth metal oxide in an amount to form a stoichiometric compound, e.g. melilite or gehlenite. The support may be formed by (i) applying a suspension of preformed secondary support to the primary support surface; (ii) applying a solution or suspension of secondary support precursors to the primary support surface and then heat treating to effect reaction and form the secondary support in situ; or (iii) selecting a primary support comprising one or more of the oxides to be combined in the secondary support, applying the other oxides or their precursors thereto and effecting reaction to form the secondary support at the surface of the primary support. The primary support may be alumina, silica, titania, magnesia, hafnia, thoria, chromia, aluminosilicates such as cordierite or zircon-mullite, alphaalumina bonded with bentonite, calcined kaolin/cement mixtures, petalite, silicon nitride or oxynitride or glass. It may be in the form of granules, fibres, multi-tubular matrices or coatings on metallic substrates such as vessel walls or meshes. The secondary support may further comprise zirconia or rare earth oxides. The support may have a catalyst applied thereto for I.C. engine exhaust gas treatment and may form part of a catalyst composition comprising 0.001-5% wt of a platinum group metal or 2-50% wt of metallic nickel and/or cobalt (calculated as monoxide) or their oxides, optionally further containing 2-10% wt copper (calculated as CuO and based on Ni/Co monoxide) or oxides of manganese or chromium or a platinum group metal. The exhaust gas treatment may be effected in two stages-reductive followed by oxidative and a preoxidation catalyst may be arranged upstream of the reductive zone. The formation of an uncalcined catalyst may be completed in situ by initially adjusting