Patent ID: 6362386
Filing Date: 2002-03-26
Classification: C07C,Y02P

Abstract:
A process for isolating isobutene from a C4-hydrocarbon mixture consisting essentially of 1-butene, cis 2-butene, trans 2-butene, n-butane and isobutene bya) combining said C4-hydrocarbon mixture with a primary C3- or C4-alkanol, b) reacting the isobutene in said C4-hydrocarbon mixture with said primary C3- or C4-alkanol in the presence of a heterogeneous catalyst to give the corresponding tertiary ether of isobutene, c) separating the resultant reaction mixture into the relatively low-boiling, unetherified C4-hydrocarbons and the relatively higher-boiling tertiary ether of isobutene with the aid of a distillation column, where the C4-hydrocarbons are taken off at the top, and the tertiary ether of isobutene obtained at the bottom is transferred into a reactor, d) cleaving this ether into isobutene and the corresponding primary C3- or C4-alkanol, e) distilling this mixture from d) in a further distillation column, and taking off the isobutene as the top product, which comprises carrying out step a) in a zone containing reactive internals and containing the catalyst for carrying out step b) arranged in such a way that said zone is integrated into a distillation column, that a reactive distillation takes place in said zone, and that said C3- or C4-alkanol is fed separately to the distillation column above said zone and said C4-hydrocarbon mixture is fed separately to the distillation column below said zone so that there is countercurrent flow of said alkanol and said hydrocarbon mixture.