# US 4,397,770 A · Method of preparing a catalyst > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,397,770 A - Document ID: US4397770A - Status: Granted - Kind: A - Application number: 05/733,152 - Filed: 1976-10-18 - Granted: 1983-08-09 - Earliest claimed: 1975-10-22 - Assignees: United Kingdom Atomic Energy Authority - Inventors: James A. Cairns; James L. Woodhead; John D. F. Ramsay - Web page: https://patentgrep.com/patent/US4397770A ## CPC - C04B 35/111: Fine ceramics - B01D 53/86: Catalytic processes - B01J 13/0047: {containing a metal oxide} - B01J 23/10: of rare earths - B01J 23/63: with rare earths or actinides - B01J 37/0215: {Coating} - B01J 37/0236: {Drying, e.g. preparing a suspension, adding a soluble salt and drying} - C04B 38/0045: {by a process involving the formation of a sol or a gel, e.g. sol-gel or precipitation processes} - B01J 35/23: in a colloidal state - B01J 35/45: Nanoparticles - F02B 1/04: with fuel-air mixture admission into cylinder - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) ## Abstract A catalyst suitable for use in the treatment of motor vehicle exhaust emissions is made by contacting a substrate, preferably of an aluminium bearing ferritic alloy, with a first sol of refractory material followed by drying and firing, and preferably then contacting with a second sol of refractory material, which additionally contains a salt convertible to catalytic material, followed by drying and firing. The sols are obtained from refractory material, e.g., alumina, made by a vapor phase condensation method. ## Claims ### Claim 1 A method of preparing a catalyst comprising a substrate carrying refractory material which method comprises the steps of (i) contacting a substrate with a dispersion comprising colloidal particles of refractory material in a liquid medium, which refractory material has been prepared by a vapour phase condensation method, and (ii) drying and firing to produce a coating of the refractory material on the substrate. ### Claim 2 (depends on 1) A method according to claim 1 wherein catalytically active material is also applied to the substrate. ### Claim 3 (depends on 2) A method according to claim 2 wherein the catalytically active material is applied by contacting the product of step (ii) with a second dispersion in a liquid medium comprising colloidal particles of a refractory material, which has been prepared by a vapour phase condensation method, and comprising material which is catalytically active or is convertible to catalytically active material, and by converting the convertible material, if present, to catalytically active material. ### Claim 4 (depends on 3) A method according to claim 3 wherein convertible material is used and comprises a water-soluble salt of a platinum group metal in solution in water as the liquid medium. ### Claim 5 (depends on 4) A method according to claim 4 wherein the second dispersion additionally contains, dissolved therein, a water-soluble carbonisable polymer and wherein the conversion of the salt to catalytic material is effected by firing whereby the polymer is carbonised and the salt reduced to catalytic material. ### Claim 6 (depends on 5) A method according to claim 5 wherein the refractory material is alumina. ### Claim 7 (depends on 6) A method according to claim 6 wherein each of the first and second dispersions contains a grain growth inhibitor for the alumina. ### Claim 8 (depends on 7) A method according to claim 7 wherein the grain growth inhibitor is yttria. ### Claim 9 (depends on 3) A method according to claim 3 wherein the substrate comprises an aluminium-bearing ferritic alloy. ### Claim 10 (depends on 9) A method according to claim 9 wherein the alloy is an alloy of iron, aluminium, chromium and yttrium. ### Claim 11 (depends on 10) A method according to claim 10 wherein the alloy contains up to 20% chromium, 0.5 to 12% aluminium, 0.1 to 3% yttrium, and the balance iron, wherein the percentages are by weight. ### Claim 12 (depends on 11) A method according to claim 11 wherein the alloy used carries an essentially alumina surface layer, formed by oxidation of the alloy. ### Claim 13 A method of preparing a catalyst comprising the steps of (i) dispersing alumina in the form of substantially spherical primary-particles, prepared by a vapour phase condensation method, in water to give a sol; (ii) contacting said sol with an aluminium-bearing ferritic alloy which carries an essentially alumina surface layer, formed by oxidation of the alloy, (iii) drying and firing, (iv) dispersing alumina in the form of substantially spherical primary-particles prepared by a vapour phase condensation method in water to give a sol and providing in solution in the water a water-soluble salt of a platinum group metal and a water-soluble carbonisable polymer, (v) contacting the product of step (iii) with the sol of step (iv), (vi) drying and firing to reduce the salt to a platinum group metal and thereby produce the final catalyst. ### Claim 14 (depends on 13) A method according to claim 13 wherein there is provided, dissolved in the water in each of steps (i) and (iv), a water-soluble ytrrium salt which is convertible to yttria on firing. ### Claim 15 (depends on 14) A method according to claim 14 wherein the aluminium-bearing ferritic alloy is an alloy of iron, aluminium, chromium, and yttrium. ### Claim 16 (depends on 15) A method according to claim 15, wherein the alloy contains up to 20% chromium, 0.5 to 12% aluminium, 0.1 to 3% yttrium, and the balance iron, wherein the percentages are by weight. ### Claim 17 (depends on 1) A method according to claim 1 wherein said dispersion includes material which is catalytically active or is convertible to catalytically active material by step (ii).