GB675527A - A process for the catalytic reduction of sugars - Google Patents

Abstract

Sugar alcohols are obtained by reacting an aqueous solution of an optically active monosaccharide with hydrogen at substantially normal atmospheric pressure in the presence of a hydrogenation catalyst containing metallic nickel. The reduction may be effected at room temperature and in neutral, acid, or alkaline solution. The reaction is accelerated by increasing the temperature or the amount of catalyst and by adding methyl or ethyl alcohol. In examples: (1) Raney nickel is added to an aqueous solution of glucose and the air driven out by passing hydrogen through the reaction vessel. When the escaping hydrogen is pure the discharge cock is closed and the vessel agitated, the hydrogen being absorbed to form sorbitol; (2) as in (1) except that 25 per cent ammonia is added to the reaction mixture, a mixture of mannitol and sorbitol being obtained. The Specification as open to inspection under Sect. 91 includes two additional examples in which (1) an aqueous solution of commercial glucose containing Raney nickel as catalyst and to which a small amount of a base, e.g. calcium hydroxide is added at intervals to maintain a pH of 9 to 9.5, is treated with hydrogen to yield sorbitol; (2) mannitol is obtained by treating an aqueous solution of fructose with hydrogen in the presence of Raney nickel, pulverized magnesium being added to the mixture to neutralize the organic acids produced in the reaction; (3) wood sugar wort evaporated to about 25 per cent and purified is brought to a pH value of 9.5 with soda lye and then filtered. An alcoholic suspension of nickel-kieselguhr catalyst is then added and the mixture treated with hydrogen to yield a syrup. This subject-matter does not appear in the Specification as accepted.