GB682260A - Hydrogenation process for the production of alcohols - Google Patents

Abstract

A process for the production of 2 : 2 : 4-trimethyl pentan-1 : 3-diol and isobutanol comprises treating 5 : 5-dimethyl-2 : 4-di-isopropyl-6 - hydroxy - 1 : 3 - dioxan (isobutyraldoxan) in the liquid phase with hydrogen at temperatures in the range 30 DEG to 130 DEG C. and under acidic conditions and in the presence in the reaction mixture of a hydrogenation catalyst. The acidic reaction conditions may be brought about by the addition of one or more weak acids such as acetic, propionic, butyric, isobutyric, succinic, malonic or adipic acids. Strong acids such as phosphoric and trichloracetic acids and formic acid should be preferably avoided as they have a deterious effect on the catalyst. The addition of calcium chloride renders the starting material sufficiently acidic, and crude isobutyraldoxan dried over anhydrous calcium chloride is sufficiently acid to be employed directly. A diluent may be employed if desired and ethanol, isopropanol and isobutanol are suitable. Atmospheric or superatmospheric pressure may be employed. In examples (1) isobutyraldoxan, isopropanol, acetic acid and Raney nickel are heated under hydrogen and the desired product isolated by distillation. On repeating the process in the absence of acetic acid after only a small portion of the hydrogen is absorbed the absorbtion ceases but recommences on the addition of the acid. In example (2) isobutyraldoxan dried under calcium chloride is treated as in example (1), though no acid is added, to give the desired diol and isobutanol. Isobutyraldoxan may be prepared by condensing isobutyraldehyde in the presence of an alkali catalyst.