GB844637A - Preparation of eta alumina - Google Patents

Abstract

A mixture of alcohols, normally having from 2-20 carbon atoms, is produced inter alia in the hydrolysis of aluminium alcoholates to precipitate alumina (see Group III). The alcoholates are obtained by reacting a C2-C4 olefin with a compound of formula: <FORM:0844637/IV(b)/1> where R1 is a C2-C8 alkyl group and R2 and R3 are C1-C8 alkyl groups or hydrogen, to form a mixture of aliminium trialkyls of higher molecular weight, e.g. in which the alkyl groups contain 2-20 carbon atoms, and oxidising said trialkyls to a mixture of the corresponding alcoholates. The preferred olefin is ethylene and initial aluminium alkyl compounds specified are aluminium triethyl, tripropyl, tributyl and triisobutyl, aluminium diethyl hydride and aluminium ethyl dihydride. The first reaction may take place at 85-120 DEG C. and 200-5000 p.s.i.g. in a reactor having several sections packed with Raschig rings over a period of 1-30 hrs. to give products having three similar alkyl groups with 4, 6, 8, 10, 12 or 14 carbon atoms or three different groups e.g. <FORM:0844637/IV(b)/2> a diluent such as a C6-C8 paraffin, benzene, toluene or xylene may be employed. The aluminium trialkyl is then oxidixed, preferably with air at 0-90 DEG C. and 0-500 p.s.i.g.; a diluent such as hexane, heptane, octane, benzene, toluene, or a solvent naphtha having a boiling range of 200-400 DEG F. may be used. Specifications 760,081 and 827,392 are referred to. Reference has been directed by the Comptroller to Specification 667,145.ALSO:In the production of c -alumina by hydrolysing aluminium alcoholates, ageing to form b -alumina trihydrate and calcining at 260-800 DEG C., the alcoholates are prepared by reacting an olefin with a compound of formula: <FORM:0844637/III/1> where R1 is a C2-C8 alkyl group and R2 and R3 are C1-C8 alkyl groups or hydrogen, to produce a mixture of aluminium trialkyls of higher molecular weight, e.g. in which the alkyl groups have 2-20 carbon atoms, and oxidising said trialkyls to a mixture of the corresponding aluminium alcoholates (see Group IV(b)). The hydrolysis of the alcoholates (which may be a solid or liquid and may be hydrolysed in solution in e.g. n-heptane) may be performed by spraying into water (as in Specification 760,081) or an aqueous solution of an organic or volatile inorganic acid (as in Specification 827,392) or an aqueous solution of ammonia. The mixture is preferably stirred during hydrolysis. The alumina is then aged, preferably without agitation, at temperatures depending on the hydrolysis, and if desired in the presence of b -trihydrate seeds. Reference has been directed by the Comptroller to Specification 667,145.