Process for the preparation of olefins

摘要

Olefins, especially propenes from steam cracking or 4C refinery streams, are produced in a coupled metathesis process. Olefins, especially propenes from steam cracking or 4C refinery streams, are produced by: (A) optionally extractively distilling butadiene from the 4C stream with a butadiene-selective solvent to obtain a butadiene-rich 4C stream; (B) selectively hydrogenating butadiene and acetylenic impurities in the steam cracker or 4C stream refinery stream or the stream from step (A) with simultaneous or subsequent partial isomerization of 1-butene to 2-butene to obtain a 4C stream containing n-butene and i-butene and being essentially free from impurities; (C) removing I-butene from the 4C stream in step (B) by reacting with an alcohol to form an ether, which is removed and split to recover the pure isobutene, to obtain a 4C stream containing n-butene and optionally oxygenate impurities; (D) removing the oxygenate impurities from the 4C stream in (C) using an adsorbent; and (E) carrying out a two-step metathesis of butene in the 4C stream in step (D).