Process for the production of gamma-butyrolactone

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG.
1 of the drawings, maleic anhydride is supplied in line 1 to an esterification plant which is also supplied in line 3 with a mixture of makeup 2 ethanol from line 4 and of recycled ethanol from line 5.
Esterification plant produces a stream of acid free diethyl maleate in line 6, part of which is fed by way of lines 7 and 8 to a vapour phase catalytic hydrogenation plant 9 which is also fed with hydrogen in line 10.
In plant 9 the diethyl maleate is hydrogenated in the presence of excess gaseous hydrogen by passage, in the vapour phase, over a copper chromite catalyst to produce a crude product stream in line 11 that is substantially free from diethyl maleate and contains, as products, a mixture of butane-1,4-diol, gamma-butyrolactone, and tetrahydrofuran, and, as recyclable materials, diethyl succinate, and ethanol, as well as minor amounts of byproducts, including water, n-butanol, and "heavies" such as diethyl ethoxysuccinate.
Esterification plant 2 may include a noncatalytic monoesterification stage, in which maleic anhydride is reacted with excess ethanol to yield monoethyl maleate according to the following equation: ##STR1## and one or more catalytic esterification stages, in which the resulting monoethyl maleate is further reacted with ethanol to yield diethyl maleate, according to the following equation: ##STR2## Although homogeneous liquid phase esterification catalysts, such as sulphuric acid, can be used, it is preferred to use in the catalytic esterification stage or stages a heterogeneous solid catalyst, such as an ion exchange resin containing sulphonic acid groups, for example Amberlyst 16.
(The word "Amberlyst" is a trade mark).
This obviates the need to neutralise the catalyst as is necessary when using a homogeneous catalyst, such as sulphuric acid.
Hence the production of significant quantities of waste liquors and loss of potential product, in the form of monoethyl maleate, therein is avoided by use of a heterogeneous catalyst