Process for the co-production of aliphatic diols and cyclic ethers

Abstract

A process for the co-production of a diol product (e.g. butane-1,4-diol) and a cyclic ether (e.g. tetrahydrofuran) by hydrogenation of an aliphatic diester or lactone feedstock (e.g. dimethyl or diethyl maleate), which contains a minor amount of acidic material, such as the corresponding monoester. The process utilizes a plurality of hydrogenation zones connected in series, each containing a charge of a granular ester hydrogenation catalyst. The catalyst in the first hydrogenation zone is tolerant of a minor amount of acidic material, while the catalyst in the second hydrogenation zone provides enhanced yields of cyclic ethers compared to the catalyst of the first hydrogenation zone. The catalyst in a third hydrogenation zone exhibits low selectivity towards conversion of the diester to at least one by product (e.g. 2-4'-hydroxybutoxy-tetrahydrofuran). The feedstock is supplied to the first hydrogenation zone as a vaporous stream comprising hydrogen and there is recovered a final product stream from the third hydrogenation zone which is substantially free of the hydrogenatable material and contains the diol, cyclic ether and other by products, the selectivity to the cyclic ether being greater in the final product stream than in the first intermediate product stream.