Patent ID: 6743958
Filing Date: 2004-06-01
Classification: C07C

Abstract:
A process for converting an olefinic C4 fraction into propylene, said olefinic fraction comprising butadiene-1,3, butene-1, butene-2, isobutene, and acetylenic impurities, said process comprising the following successive stages:1) selective hydrogenation of diolefins and acetylenic impurities with isomerization of butene-1 into butenes-2, carried out in a reactor, in the presence of a catalyst, in order to obtain an effluent that contains for the most part butenes-2 and isobutene, and that contains essentially no diolefins or acetylenic compounds; 2) separation of said effluent from stage (1) by distillation to produce a top fraction that contains for the most part isobutene and unconverted butene-1 from the first stage, and a bottom fraction that contains essentially butene-2 and butane; and 4) metathesis of the butenes-2 that is obtained from stage 2 with the ethylene so as to obtain an effluent that contains propylene, followed by a separation of the propylene; said process also comprising a stage (3) of skeletal isomerization of the isobutene in the top fraction into n-butenes, with recycling of at least a portion of the resultant n-butene into stage 1.