GB720031A - Method of preparing silico-alumina catalysts - Google Patents

Abstract

A silica-alumina catalyst is prepared by mixing an aumina hydrosol of pH 3.5-6.5 with a slica ing an alkali metal silicate to a pH of 3.5-6.5) hydrosol of pH 3.5-6.5 (prepared e.g. by acidifyallowing the mixture to set to a transparent, vibrant "ultragel," washing with or without previous drying, drying and calcining said ultragel. Catalysts in the form of spherical beads may be prepared by gelling droplets of the mixed sols in suspensions in, e.g., an oil bath, by spray drying, &c. A pH range of 4-5.2, better 4.6 is preferred for the silica hydrosol, and the catalyst may contain 30-75 per cent or even more of alumina. Acidification may be by means of sulphuric, hydrochloric, formic or other acids. The alumina hydrosol may contain in solution an organic acid such as acetic, having a dissociation constant of less than 1 x 10-3, and may be prepared by the known action of water containing a peptizing agent such as 1-2 per cent acetic, or formic acid, upon aluminium amalgam. The activity of the catalysts may be increased by immersing the dried gel in various solutions, ammonia, magnesium carbonate, calcium bicarbonate, acetic acid, ammonium chloride, and Lake Michigan water being specified. The use of a catalyst containing 32 per cent. alumina to crack a gas oil having a sulphur content of 1.38 per cent by weight, at 922 DEG F, is mentioned, in the process all unconverted heavy distillates boiling above the gasoline end point being recycled.