| abstract |
Butane-1,4-diol is produced by vapor phase hydrogenolysis of an alkyl ester of a C 4 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, 5° C.) and the resulting cooled mixture is fed to the second zone in which is 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 150° C. to 200° C., pressures of 25 to 70 bar, and a H 2 :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 hyrogenolysis zone. |