US 6,777,582 B2 · Process for producing propylene and hexene from C4 olefin streams

Abstract

A C3 to C6 hydrogen cut from a cracking unit is processed for the conversion of olefins to propylene and hexene via autometathesis. The autometathesis of a mixed normal butenes feed 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 formed in the reactor with unreacted butenes to simultaneously form additional propylene and hexene. In one embodiment, some or all of the 3-hexene formed in the reaction is isomerized to 1-hexene. In another embodiment, some portion of the 3-hexene produced in the main metathesis reaction is reacted with ethylene to produce 1-butene without the need for superfractionation. In another embodiment, the 3-hexene product is hydrogenated and recycled back to the cracking heaters.

Claims44

Dependent claims

A process for the conversion of a n-butene feed containing both 1-butene and 2-butene to propylene comprising the steps of:

(a) passing said n-butene feed and a 2-pentene feed into an autometathesis reactor in contact with a methathesis catalyst whereby said 1-butene and 2-butane react to form propylene and 2-pentene and said 2-pentene stream reacts with 1-butene to form additional propylene and 3-hexene;
(b) separating the effluent from said autometathesis reactor into a propylene product stream, an unreacted n-butene stream, a 2-pentene stream and a product 3-hexene stream;
and
(c) recycling at least a portion of said separated 2-pentene stream as said 2-pentene feed to said autometathesis reactor;
wherein said n-butene feed is obtained from a pyrolysis cracking process and wherein only a portion of said separated 2-pentene stream is recycled leaving an unrecycled portion comprising the further steps of hydrogenating said unrecycled portion of said 2-pentene stream and at least a portion of said product 3-hexene stream and then recycling these hydrogenated streams back to the pyrolysis cracking process.

2 more elements

Dependencies are inferred from the claim text.

Process for producing propylene and hexene from C4 olefin streams

Life of this patent

Process for producing propylene and hexene from C4 olefin streams

Life of this patent

Abstract

Claims44