Process and plant for the conversion of olefinic C4 cuts to polyisobutene and to propylene

An apparatus for converting an olefinic C4 cut comprising diolefins, 1-butene, isobutene and acetylenic impurities to polyisobutene and to propylene, comprising:

• a) a first selective hydrogenation zone having a catalyst bed for introduction of the C4 cut, for hydrogenating diolefins anid acetylenic impurities and simultaneously isomerizing 1-butene to 2-butenes;
• b) in downstream connection with the first selective hydrogenation zone, a first polymerization and separation zone containing at least one acid catalyst for polymerizing the isobutene in the effluent from the tirst selective hydrogenation zone to polyisobutene and separating the polyisobutene from a residual C4 cut;
• c) in downstream connection with the first polymerization and separation zone, a first metathesis zone conraining at least one catalyst for metathesis of the residual C4 cut from the first polymerization and separation zone with ethylene to produce propylene and for separating a propylene metathesis product from by-products;
• and
• d) a section for treating an olefinic C5 cut to produce at least a portion of the olefinic C4 cut to be converted, said C5 cut containing diolefins, alpha olefins containing 5carbon atoms and acetylenic impurities, the section comprising:
• 1) a second selective hydrogenation zone comprising at least one bed of a catalyst for hydrogenating diolefins and acerylenic impurities and simultaneously isomerizing alpha olefins containing 5 carbon atoms to 2-pentenes and 2-methyl-2-buttene;
• 2) in downstream connection with the second selective hydrogenation zone, a second metathesis zone containing at least one catalyst for metathesis of thre effluent of the second selective hydrogenation zone with ethylene and for separating from the metathesis product propylene, a mixture of 1-butene and isobutene and by-product, and
• 3) a connection for supplying the mixture of 1-butene and isobutene obtained from the second metathesis zone as at least a portion of the olefinic C4 cut in the first selective hydrogenation zone.