| abstract |
Butane-1,4-diol is produced by vapour phase hydrogenolysis of an alkyl ester of a C4 dicarboxylic acid, e.g. diethyl maleate, over a reduced Cu-Cr or Cu-Zn mixed oxide catalyst. Two adiabatic hydrogenolysis zones are used. The mixture exiting the first of these zones is cooled (by, for example, 5oC) and the resulting cooled mixture is fed to the second zone in which it reequilibriates at a lower temperature to increase the butane-1,4-diol yield at the expense of gamma-butyrolactone. Typical reaction conditions include use of temperatures of 150oC to 200oC, pressures of 25 to 70 bar, and a H2:ester molar ratio of 100:1 to 800:1. When using a maleate ester it is often advantageous to hydrogenate this to the corresponding succinate ester in an upstream hydrogenation zone prior to entry to the first hydrogenolysis zone. |