Process for the preparation of C5-/C6-olefins

摘要

The production of 5C/6C olefins from a 4C olefin-containing product stream involves disproportionation of 1-, 2- and iso-butene on a Group VIb, VIIb or Sub-Group VIII metal-based catalyst followed by distillation to give a 4-6C fraction which is then distilled to give hexene and methylpentene as a high-boiling fraction. A process (A) for the production of 5C/6C olefins from 4C olefins involves: (a) disproportionation of 1-butene, 2-butene and isobutene in a 4C olefin product stream in presence of a disproportionation catalyst containing Group VIb, VIIb or Sub-Group VIII metal compound(s), to give a mixture of 2-6C olefins and butanes; (b) distillation to give a low-boiling fraction (A) comprising 2-3C olefins or 2-4C olefins and butanes, which is removed, and a high-boiling fraction consisting of 4-6C olefins and butanes; (c) distillation of the high-boiling fraction to give a low-boiling fraction (B; butenes and butanes), a middle fraction (C; pentene and methylbutene) and a high-boiling fraction (D; hexene and methylpentene), and (d) separation of (D) as product, with complete or partial return of fractions (B) and/or (C) to stage (a). An Independent claim is also included for a process (B) for the production of 5C/6C olefins and propene from steam cracker streams or refinery 4C streams, involving: (1) removal of butadiene and acetylenes by optional extraction with a butadiene-selective solvent and subsequent or alternative selective hydrogenation of butadienes and acetylenic impurities in the crude 4C fraction, to give a product containing n-butene and iso-butene; (2) removal of isobutene by reaction of the above product with an alcohol in presence of acid catalyst to give an ether, with separation of the ether and alcohol to give a product containing n-butene and possibly oxygenated impurities, and removal of the ether or re-cleavage for the production of pure isobutene by subsequent distillation with optional separation of entrained 3C, iso-4C and 5C hydrocarbons; (3) removal of oxygenated impurities on suitable adsorbers; and (4) disproportionation of the refined product (II) stream as in stages (a)-(d) above.