Process for the double bond hydroisomerization of butenes

A process for the production of propylene from a C4 stream containing butadiene, 1-butene, and 2-butene, comprising:

• mixing said C4 stream with a first hydrogen stream to hydrogenate butadiene and form a feed stream having a butadiene content of no more than about 1 wt %,
• hydroisomerizing said feed stream in the presence of a hydroisomerization catalyst in order to convert at least a portion of said 1-butene to 2-butene, thereby producing a hydroisomerization effluent,
• passing said hydroisomerization effluent through a fractionation column to form a top stream comprising isobutane and isobutylene and a bottoms stream comprising 2-butene,
• withdrawing a recycle stream from said fractionation column at a location in said column at which the weight ratio of 1-butene to 2-butene is at a maximum,
• combining said recycle stream with at least one of said C4 stream and said feed stream upstream from said hydroisomerization catalyst,
• mixing said bottoms stream with ethylene to form a metathesis feed stream, and
• feeding said metathesis feed stream to a metathesis reactor and reacting said 2-butene with said ethylene to form propylene.

An apparatus for the preferential conversion to 2-butene of a feed stream containing hydrogen and C4 compounds including 1-butene and 2-butene, comprising:

• a hydroisomerization reactor configured to contain a hydroisomerization catalyst for converting at least a portion of said 1-butene is said feed stream to 2-butene,
• a fractionation column for separating said hydroisomerized feed stream into a top stream comprising isobutane and isobutylene and a bottoms stream comprising 2-butene,
• a side draw near the top of said fractionation column for removing a recycle stream, and
• a recycle inlet for combining said recycle stream with said feed stream upstream from said hydroisomerization catalyst.