Patent ID: 6271430
Filing Date: 2001-08-07
Classification: B01D,C07C,Y02P

Abstract:
A process for preparing propene bya) passing a raffinate II stream comprising a mixture of 1-butene and 2-butene obtained from a refinery process over absorber materials to purify the raffinate II stream by removing water, oxygen, sulfur, nitrogen, phosphorus or halogens, passing the purified raffinate II stream into a first reactor (R1),b) reacting the 1-butene and 2-butene in raffinate II in the presence of a metathesis catalyst comprising at least one compound of a metal of transition group VIb, VIIb or VIII of the Periodic Table of elements to give propene and 2-pentene,c) subsequently passing the effluent from reactor R1 to a distillation column (D1) wherein the effluent is separated into low boiling C.sub.2-3 hydrocarbons, intermediate boiling C.sub.4 hydrocarbons and high boiling C.sub.5+ hydrocarbons,d) passing at least a portion of the high boiling C.sub.5+ hydrocarbons together with added ethene to reactor R2 for reaction in the presence of a metathesis catalyst comprising at least one compound of a metal of transition group VIb, VIIb or VIII of the Periodic Table of elements to give a mixture containing 1-butene and propene,e) subsequently passing the effluent from reactor R2 to distillation column (D1),f) subsequently passing the stream of low boiling C.sub.2-3 hydrocarbons from distillation column (D1) to a distillation column (D3) for separation into ethene and propene and passing the ethene to metathesis reactor R2,g) passing at least a portion of the intermediate boiling C.sub.4 hydrocarbons to reactor R1 and optionally removing any remaining intermediate boiling C.sub.4 hydrocarbons from the system,h) continuously passing the effluents from Reactors R1 and R2 to distillation column D1 subsequently returning the 1-butene formed in d) to step a) and, recovering the propene.