Patent GB-735257-A (GB)
Title: Improvements in or relating to stabilized metal catalysts for naphtha reforming
Inventor: KEARBY KENNETH KARL
IPC: B01J27/13
Filed: 1953-05-18
Abstract: Catalysts containing platinum or palladium are prepared by contacting, in the presence of a precipitating agent, a homogeneous dispersion of a platinum- or palladium-containing material and a compound capable of yielding a hydrous oxide, so as to precipitate simultaneously, on to a preformed carrier, a colloidal dispersion of platinum or palladium in a hydrous oxide. Suitable carriers are alumina (which may contain silica and titania), silica, silica-alumina, or activated carbon.  The hydrous oxide may be alumina or silica, or hydrated oxides of chromium, zirconium, thorium, titanium, or iron.  Methods of catalyst preparation specified are (a) precipitation by ethylene oxide of a solution containing chlorides of aluminium, zirconium, or chromium and of platinum on to a carrier; alternatively ethylene oxide may be added to aluminium, zirconium or chromium chloride solution and platinic chloride solution added subsequently; (b) hydrolysis of an alcoholate of silicon or aluminium or of a silicate or alkyl silicate, with precipitation of platinum from the same solution on to a carrier; e.g. a mixture of ethyl orthosilicate and isopropyl alcohol is added to hydrochloric acid, a solution of platinic chloride is stirred in, ethylene oxide added, and the solution used to impregnate alumina or silica gel; (c) addition of ammonia to a solution of an aluminium salt (e.g. chloride) and chloroplatinic acid; the ammonia may contain ammonium sulphide and the precipitation is preferably effected at a pH greater than 8.5; alternatively solutions of aluminium chloride and chloroplatinic acid are added, either separately or together, to a vigorously agitated solution of ammonia, ammonium sulphide, or ammonium carbonate; (d) addition of a weak base to a peptized sol of the hydrous oxide containing platinic chloride; (e) reduction of a solution of chromic acid and platinic chloride with alcohol or sugar; (f) impregnation of active alumina with a solution containing chromic nitrate and platinic chloride, followed by treatment with ammonium acetate solution; (g) addition of aniline to a methanol solution of aluminium nitrate, addition of magnesia to an aluminium salt solution, or addition of sodium silicate to dilute acid, in each case with simultaneous precipitation of platinum on to the carrier. Non-ionic or ionic wetting or dispersing agents may be present during the precipitation.  After precipitation on to the carrier, the catalyst is dried and may be calcined and reduced by treatment with hydrogen.  The preferred platinum or palladium content of the final catalyst is 0.05-2 per cent by weight and the dry hydrous oxide content 0.5-20 per cent.  When chlorides or oxychlorides are used in the preparation, a small amount of residual chlorine may remain in the catalyst as a promoter. Fluoride may be introduced before or after the precipitation step. The catalysts are suitable for the hydroforming of naphthas, especially at pressures of 100-300 lb. per square inch, and are stable to regeneration by air or oxygen-containing gases.