GB691574A - Improved process for preparing microspheres of silica-alumina gel catalyst - Google Patents

Abstract

Silica-alumina microspheres are prepared by spray-drying to a moisture content below 8 per cent and preferably from 3 to 4 per cent, a slurry of unwashed silica-alumina gel still containing soluble salts produced in its formation. The product may be washed to remove soluble salts and calicined to a final moisture content of 2 per cent. The slurry is prefarably prepared by mixing a solution of sodium silicate and sulphuric acid to form a slightly alkaline reaction product, e.g. pH 9.3, adding sulphuric acid to reduce the pH to 2.5 to 6 thereby completing the precipitation and gelation of the silica, adding aluminium sulphate to impregnate the gel particles and adding aqueous ammonia to precipitate alumina in the gel and form a slurry having a pH of 6.0 to 7.5. The slurry is dewatered by filtration, thereby removing half of the soluble salts present, reslurried and spray dried in hot gases at 212 to 1500 DEG F to a water content of 8 per cent or less. The resulting microsphenes are then worked to remove completely soluble salts, a dilute solution of ammonium sulphate being employed if desired, dewatered and calcined. A typical catalyst contains 13 per cent alumina and a fixed water content of 12 per cent. Specifications 586,945 and 30187/49 (as open to inspection), are referred to.