GB767775A - Improved alumina - Google Patents

Abstract

In the example, an aluminium alcoholate was prepared by contacting aluminium metal with a mixture of amyl alcohols and a hydrocarbon of boiling range 240-280 DEG F. in the presence of a HgCl2 catalyst. The mixture was initially heated to 250 DEG F. and subsequently cooled.ALSO:<PICT:0767775/III/1> Alumina which may be used as a catalyst or catalyst support is prepared by hydrolizing an aluminium alcoholate with a solution of water and an alcohol having more than two carbon atoms per molecule there being advantageously an excess of no more than 10 weight per cent of the stoichiometric amount of water for hydrolysis to the monohydrate. Specified alcoholates are those of alcohols having 1-10 or 12, preferably 4-6 carbon atoms per molecule e.g. a mixture of amyl alcohols; specified alcohols in the hydrolysing liquid have 4-6 carbon atoms per molecule. After precipitation the alumina (which may be in the monohydrate (boehmite) form) may be calcined at a temperature below 1400 DEG F., e.g. 900-1400 DEG F. In one embodiment of the invention illustrated by the flowsheet, an amyl alcohol mixture and aluminium are fed into reactor 5, if desired with a hydrocarbon diluent and then passed via storage vessel 11 and after introduction of a peptizing agent such acetic acid into mixing and hydrolysis vessel 15 into which water-saturated (9 wt. per cent water) amyl alcohol is introduced. The hydrolysis zone should be efficiently agitated. (By agitating the aluminium alcoholate in the alcohol containing the water for hydrolysis it is stated that small droplets of the alcoholate may be formed which on hydrolysis give gelled speroids). The mixture is then passed to an efficient agitated soaking drum 23 to complete hydrolysis and to a mixing zone 27 into which excess water is passed, thus creating a second phase, and thence to a settler 33 where the alumina settles into the aqueous phase. A part of the wet alcohol phase is re-cycled to the hydrolysis zone 15 and a part to the reaction zone 5 after removal of water by azeotropic distillation in tower 39. The aqueous phase containing the alumina has alcohol removed therefrom in stripper 47, (the removed alcohol being passed to said distillation tower 39) and the resultant slurry or sol is passed to impregnation zone 53 to which ammonium molybdate or other catalytic agent is added, if desired after the addition of zinc acetate to form a zinc-alumina type of base. The mixture passes to a soaking drum 61 for aging; a portion therefrom may be returned as "seed" to stripper 47. The impregnated mixture is then spray dried in zone 65. In alternative or specific embodiments, (a) an alumina sol may be gelled and dried or calcined before impregnation, (b) molybdic oxide may be dry-mixed with the dried or partly dried alumina and calcined, (c) a heat-decomposable compound of platinum may be applied to the alumina and later converted to platinum, or platinum may be precipitated on the alumina. Specified catalytic materials are: molybdic oxide (5-20, preferably 10 wt. per cent) chromic oxide (10-50 wt. per cent) platinum (0.01-2.0, preferably 0.5 wt. per cent) palladium (0.5-5 wt. per cent) vanadium oxide and nickel oxide. The catalyst may be activated by calcination at 1000-1400 DEG F. In the example an aluminium amylate was prepared from a mixture comprising 75 per cent anhydrous commercial amyl alcohols and 25 per cent hydrocarbon (boiling point range 240-280 DEG F.) and aluminium metal using mercuric chloride as catalyst at 250 DEG F. was hydrolised with isopropyl alcohol containing 9 per cent water at room temperature. Samples of the alumina were (a) treated with additional water (b) heated with additional water on a steam bath for 24 hours (c) dried directly at 160 DEG F. A sample (d) was prepared by hydrolyzing the aluminium alcoholate with water at room temperature. After drying at 260 DEG F. the samples were: (a) and (c) boehmite, (b) boehmite plus bayerite, (d) bayerite. On further heating to 1200 DEG F., each sample formed eta alumina, the surface area and pore volume of which are stated.