Process for producing propylene and hexene from C4 olefin streams

A C 3 to C 6 hydrogen cut from a cracking unit is processed for the conversion of olefins to propylene and hexene via autometathesis. The autometathesis (16) of a mixed normal butenes feed (10) in the presence of a metathesis catalyst operates without any ethylene in the feed mix to the metathesis reactor. Some fraction of the 2-butene feed may be isomerized to 1-butene and the 1-butene formed plus the 1-butene in the feed react rapidly with the 2-butene to form propylene and 2-pentene. The feed to the reactor also includes the recycle of the 2-pentene (14) formed in the reactor with unreacted butenes to simultaneously form additional propylene and hexene. Some or all (34) of the 3-hexene (26) formed in the reaction is isomerized to 1-hexene (46). In one embodiment, some portion (72) of the 3-hexene (26) produced in the main metathesis reaction is reacted with ethylene to produce 1-butene (96) without the need for superfractionation.