Crude butan-1,4-di:ol purification to minimise impurities causing discoloration or poor reactivity

摘要

The purification of crude butan-1,4-diol (I), obtained by hydrolysis of diacetoxybutane (II), comprises (1) hydrogenating crude (I) in the presence of a hydrogenation catalyst (III); (2) removing a fine (III) powder from the hydrogenation mixture; and (3) distilling the remaining mixture to give highly pure (I) from a side stream of the distillation column. PREFERRED COMPOSITION - The crude (I) is contaminated by BGTF and the purified (I) by <= 0.1 wt.% BGTF. PREFERRED CATALYST - (III) consists of a palladium (Pd) catalyst and a ruthenium (Ru) catalyst. PREFERRED CONDITIONS - (III) is removed by filtration, especially through a filter with a pore size <= 10 mu m. In distillation, water and acetic acid from the hydrolysis product are separated with a distillation column for low boiling products and crude (I) is discharged at vapour from the lower side stream of a column for high boiling products. The oxygen pressure at the top of the column in stage (3) is <= 10 mmHg.