Method for purifying isobutene from a C4 stream and process system therefor

A process for the purification of isobutene from a C4 stream comprising at least 1-butene, 2-butene, isobutane and isobutene, the process comprising the following steps:

• supplying the C4 stream to a first rectification column which is associated with a first catalyst comprising at least one metal active in hydrogenation on a first support,
• wherein the C4 stream is subjected to distillation in the first rectification column,
• wherein an intermediate stream containing 1-butene is obtained from the first rectification column, the intermediate stream and a first stream of hydrogen are brought into contact with the first catalyst to isomerize 1-butene present in the intermediate stream to 2-butene, and
• wherein a reaction product stream separated from the first catalyst is supplied to the first rectification column and subjected to the distillation therein;
• separating a stream of material concentrated in isobutane and isobutene as an overhead product and a stream of material concentrated in 2-butene as a bottom product from the first rectification column, wherein the stream of material concentrated in isobutane and iso butene contains less 1-butene and 2-butene compared with the C4 stream:
• supplying the stream of material concentrated in isobutane and isobutene and a second stream of hydrogen to an isomerization reactor comprising a second catalyst, wherein the second catalyst comprises at least one metal active in hydrogenation on a second support;
• bringing the stream of material concentrated in isobutane and isobutene and the second stream of hydrogen into contact with the second catalyst in the isomerization reactor thereby isomerizing 1-butene present in the stream of material concentrated in isobutane and isobutene to 2-butene;
• supplying a product stream from the isomerization reactor to a second rectification column, wherein the product stream comprises less 1-butene compared with the stream of material concentrated in isobutane and isobutene;
• and
• providing a stream of material concentrated in isobutene:
• by separating the stream of material concentrated in isobutene:
• via a side stream from the second rectification column,
• via a side stream and a bottom product from the second rectification column, or
• as a bottom product from the second rectification column,
• wherein a stream of material concentrated in isobutane is separated from the rectification column as an overhead product, or
• by separating a stream comprising isobutane and isobutene via an overhead product from the second rectification column and then supplying the stream comprising isobutane and isobutene separated from the second rectification column to a third rectification column to separate isobutane from isobutene and to obtain the stream of material concentrated in isobutene as a bottom product from the third rectification column.