GB1457239A - Process for the preparation of butanediols - Google Patents

Abstract

1457239 Butanediols BAYER AG 22 May 1975 [22 June 1974 19 July 1974] 22264/75 Heading C2C In a process for the simultaneous preparation of butane-1, 4-diol, butane-1,2-diol and 2- methylpropane-1,3-diol in a first stage propylene, oxygen and acetic acid are reacted in the presence of a catalyst containing palladium to give allyl acetate and water, in a second stage the allyl acetate is catalytically converted with carbon monoxide and hydrogen into a mixture of 4 - acetoxybutan - 1 - ol, 2 - acetoxybutan - 1 - ol and 3 - acetoxy - 2 - methylpropan-1-ol, in a third stage this mixture is catalytically reacted with methanol to give butane - 1,4 - diol, butane - 1,2 - diol and 2- methylpropane - 1,3 - diol and methyl acetate, in a fourth stage the methyl acetate is reacted with water from the first stage in the presence of an acid cation exchanger to give methanol and acetic acid, and the methanol is returned to the third stage and the acetic acid to the first stage. Transition metal compounds are suitable catalysts for the second stage, and alkaline catalysts are suitable for the third stage. Fig. 1 is a flow sheet of an embodiment of the process. Propylene, oxygen and recycled acetic acid/water are fed via lines 5, 6 and 15 respectively to Stage 1; allyl acetate obtained is passed via 7 to Stage 2, and a stream essentially of water is passed via 16 to Stage 4. Allyl acetate is reacted in Stage 2 with hydrogen and carbon monoxide (via 8 and 9) to give acetoxybutanols which are fed, together with catalyst via 10, to Stage 3. Butanediols are removed from 3 by line 12, and methyl acetate passed via 13 to Stage 4, where it is hydrolysed with water introduced by 16; distillation gives a top product, methyl acetate and methanol, which is recycled to 3, and a bottom product, acetic acid and water, which is recycled to 1. An alternative more elaborate flow sheet for Stages 3 and 4 is given, in which also the diols obtained are separated from each other by distillation. The catalyst for Stage 2 may be prepared by reacting a cobalt compound with carbon monoxide and hydrogen in a solvent; acetoxybutyraldehydes are obtained as intermediates in Stage 2, and this stage may be carried out in two steps, the aldehydes being formed in the first step, and hydrogenated to acetoxybutanols, possibly with a different catalyst, in a second step. Further alkali may be added to the crude butanediols from Stage 3 after separation from methyl acetate, to carry the reaction to completion.