Fecha de publicación: 09/05/1956 Fuente: WIPO "olive table" A process for producing a silica-alumina hydrocarbon cracking catalyst comprising the steps of forming a silica hydrogel in aqueous slurry, mixing therewith aluminium sulphate solution, adding ammonia to precipitate alumina, spray-drying the slurry to form microspheroidal particles, washing the particles to remove soluble salts, and redrying, is characterized by treating the spray-dried particles, before washing, in an aqueous medium at a pH between 4.5 and 5.5. The particles from the spray-drying step may be collected in an aqueous slurry, the pH of which is adjusted by the addition of aqueous ammonia or an aqueous solution of an amine, e.g. methyl-, dimethyl-, or trimethylamine, ethyl- or diethylamine, isopropyl- or diisopropylamine, n-butylamine, n-hexylamine, ethylene diamine, morpholine, pyridine, monoethanolamine, diethylbenzylamine, or phenylethanolamine. The adjustment of pH enables sulphate to be washed out more easily and reduces the loss of alumina during washing. In examples, sodium silicate solution and dilute sulphuric acid are mixed and after gelation the product is aged at pH 10 and pH 6.9. Aluminium sulphate solution is added, followed by ammonia, and spray-dried particles are collected in a slurry the pH of which is raised from 4 to 4.9 by adding ammonia. The product is washed with ammonium sulphate solution and water. Figures are given which show that the temperature of spray-drying and the particle size affect the amount of ammonia or amine required for pH adjustment.