Patent ID: 8258336

Claim:
A process for preparing an unsaturated carboxylic ester, comprising reaction of an alkene having 2 to 6 carbon atoms with an alkanecarboxylic acid having 1 to 6 carbon atoms, in the presence of an oxygenous gas and in the presence of a heterogeneous noble metal catalyst, by means of a continuous homogeneous gas phase process in a reactor, wherein the method comprises circulating a cycle gas comprising the alkene and loading the cycle gas with a quantity of said alkanecarboxylic acid in an acid saturator before entry into the reactor, wherein upstream of the acid saturator is connected a presaturator in which the cycle gas is loaded with another quantity of the alkanecarboxylic acid and then is transferred into the acid saturator, wherein predominantly alkanecarboxylic acid which has been recovered from the reaction mixture leaving the reactor is used for presaturation, and wherein the presaturation is regulated such that at least 5% by weight of the alkanecarboxylic acid supplied to the presaturator is not evaporated in the presaturator and issues as a liquid from it.