Apparatus for the double bond hydroisomerization of butenes
An apparatus is described for the preferential conversion to 2-butene of a stream containing C4 compounds including 1-butene and 2-butene involving mixing the C4 stream with a first hydrogen stream to form a feed stream, hydroisomerizing the feed stream in the presence of a first hydroisomerization catalyst in order to convert at least a portion of the 1-butene to 2-butene, thereby producing a hydroisomerization effluent, passing the 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 above the feed point at which the weight ratio of 1-butene to 2-butene is high, and combining the recycle stream with at least one of the C4 stream and the feed stream upstream from the hydroisomerization catalyst.
1. 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, the hydroisomerization reactor having a feed stream inlet and a reactor outlet,
a first fractionation column configured to separate said hydroisomerized feed stream into a top stream comprising isobutane and isobutylene and a bottoms stream comprising 2-butene, the first fractionation column having a feed inlet, a top outlet and a bottoms outlet,
a side draw near the top of said fractionation column above the feed inlet for removing a recycle stream, and
a recycle inlet for combining said recycle stream with said feed stream upstream from said feed stream inlet.
2. The apparatus of claim 1 , wherein the side draw is positioned at an elevation in said column at which the 1-butane concentration would be at a maximum if no side draw were withdrawn.
3. The apparatus of claim 1 , further comprising a metathesis reactor positioned downstream from the bottoms outlet of the fractionation column.
4. The apparatus of claim 1 , further including a second fractionation column positioned downstream from the hydroisomerization reactor and upstream from the first fractionation column to remove C5 and/or heavier components.
5. The apparatus of claim 1 , wherein the hydroisomerization reactor further includes a hydrogen inlet downstream from the feed stream inlet.
6. The apparatus of claim 5 , wherein the hydroisomerization reactor further includes a supplemental hydrogen inlet downstream from the hydrogen inlet.
7. The apparatus of claim 1 , wherein the side draw is positioned at the elevation in said fractionation column at which the driving force for the hydroisomerization of 1-butene to 2-butene would be at least 85% of the maximum driving force within said column if no recycle stream were withdrawn.
8. 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, the hydroisomerization reactor having a feed stream inlet and a reactor outlet,
a first fractionation column configured to separate said hydroisomerized feed stream into a top stream comprising isobutane and isobutylene and a bottoms stream comprising 2-butene, the first fractionation column having a feed inlet, a top outlet and a bottoms outlet,
a side draw near the top of said fractionation column above the feed inlet for removing a recycle stream, the side draw being positioned at an elevation in said column at which the 1-butane concentration would be at a maximum if no side draw were withdrawn,
a second fractionation column positioned downstream from the hydroisomerization reactor and upstream from the first fractionation column to remove C5 and/or heavier components, and
a recycle inlet for combining said recycle stream with said feed stream upstream from said feed stream inlet.