GB701349A - Improvements in or relating to the manufacture of alumina sols and catalysts therefrom - Google Patents

Abstract

Solutions of aluminium alcoholates, hydrolysable in the presence of a peptizing agent to form alumina hydrosols (see Group III), are prepared by dissolving aluminium in an aliphatic alcohol containing from 2-10 carbon atoms in the presence of a catalyst. Amyl, tertiary butyl, isopropyl, and ethyl alcohols are referred to. Suitable catalysts are mercuric chloride, iodine, and aluminium halide. A hydrocarbon, e.g. heptane, octane, toluene, benzene, xylene, or a petroleum fraction boiling from 180-500 DEG F., may be added to the alcohol to control the temperature of the reaction and to serve as a solvent for the alcoholate. Reaction may be carried out under atmospheric or super-atmospheric pressure at a temperature of 200 DEG -300 DEG F. Heat is supplied initially and then the heat of reaction removed by cooling.ALSO:Alumina hydrosol is prepared by hydrolysis of an anhydrous solution of an aluminium alcoholate in the presence of a peptizing agent which is added to the alcoholate solution before the addition of water. Specified peptizing agents are acetic acid, aluminium chloride, aluminium bromide, hydrogen chloride, hydrogen bromide, formic acid, lactic acid, glycollic acid. Preferred amounts of peptizing agent are 1/10 -2 parts by weight per part of alumina. To form the alcoholate, aluminium may be dissolved under pressure at about 200 DEG -300 DEG F. in an aliphatic alcohol of 2-10 carbon atoms, preferably water-insoluble, in the presence of a catalyst, e.g. mercuric chloride, iodine, or aluminium halide; in examples isopropyl alcohol and amyl alcohol are used to dissolve the aluminium. From 0-90 per cent. of a hydrocarbon, e.g. heptane, octane, toluene, benzene, xylene, or a petroleum fraction boiling from 180 DEG -500 DEG F. may be mixed with the alcohol in order to facilitate subsequent separation. Hydrolysis is effected by mixing with water at 65 DEG -220 DEG F., and the product may be aged for at least 15 minutes at 70 DEG -210 DEG F. and separated into two layers; the upper layer of regenerated alcohol and hydrocarbon is heated to remove water, and then used again in the process; the lower alumina sol is heated to remove alcohol and hydrocarbon, and aged for 1-20 hours at a pH of 3-7. To prepare silica-alumina catalysts the alumina sol, which may contain 1-8 per cent. alumina, is mixed with a silica sol containing 3-15 per cent. silica. The silica sol is obtained by contacting sodium silicate solution with an acid-regenerated cation exchange material by a four-stage process involving washing and regeneration of the ion exchange material; preferably a bed of weak acid-type resin is superimposed on a bed of strong acid-type resin; the silica sol may be aged for 1-20 hours at 80 DEG -180 DEG F., and preferably has a pH of 2-7. The mixed sols may be dried and ground, or they may be sprayed into hot gas to obtain microspherical gel particles; alternatively they may be sprayed above or into a body of heated organic liquid which may contain an emulsifying agent. The gel particles may be further dried and activated at 800-1400 DEG F.