GB799459A - Improvements in or relating to manufacture of platinum-containing catalysts - Google Patents

Abstract

Platinum-containing catalysts are prepared by impregnating a carrier comprising alumina with a solution of a platinum compound and then calcining, without addition of halogen to the composite, at a temperature in the range 250-595 DEG C. in the presence of a free oxygencontaining gas to which water has been added in an amount to give the gas a water content of at least 15.78 grams per kilogram of dry gas. The association between the platinum and the alumina is improved so that less platinum is washed off when the catalyst is treated with hot ammonium nitrate solution. The alumina support may also contain silica, titania or boron oxide. A halogen, especially fluorine, may be present in the catalyst in an amount of 0.1-8 per cent by weight of dry alumina; the halogen may be added as a solution of hydrogen fluoride or hydrogen chloride or as an ammonium salt of these acids. The platinum content of the catalyst is preferably 0.01-1 per cent by weight and may be introduced by mixing aqueous solutions of chloroplatinic acid and ammonium hydroxide and adding to the alumina. The alumina may be formed by precipitation from a solution of an aluminium salt, especially the chloride, with ammonium hydroxide or carbonate; the precipitate is calcined at 535-760 DEG C., washed, and formed into pills with the aid of a lubricant. The halogen and the platinum are added either before or after forming the pills. Alternatively the alumina is produced in spherical form by passing droplets of alumina sol into an oil bath. The addition of water to the oxygen-containing gas used in calcination may be effected by spraying in water or by adding steam to the gas or to the calcination zone. The catalysts are particularly useful for the reforming of gasoline hydrocarbons in the presence of hydrogen, and may also be used in other reactions including the dehydrogenation of naphthenes to aromatics, paraffins to olefins, or mono-olefins to di-olefins, dehydrocyclization, isomerization of paraffins and alkyl cyclic compounds, destructive and non-destructive hydrogenation of hydrocarbons, oxidation of hydrocarbons to oxides and alcohols, and desulphurization of hydrocarbon mixtures. Specification 657,565 is referred to.