Patent ID: 7781608
Filing Date: 2010-08-24
Classification: C07C

Abstract:
1. A process for preparing 3-pentenenitrile by hydrocyanating 1,3-butadiene, comprising by the following process steps: (a) reacting 1,3-butadiene which comprises cis-2-butene with hydrogen cyanide over at least one catalyst to obtain a stream 1 which comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one catalyst, 1,3-butadiene and residues of hydrogen cyanide which has yet to be converted, (b) distilling stream 1 in a distillation column K1 to obtain a stream 2 as the top product which comprises the predominant portion of the 1,3-butadiene from stream 1, and a stream 3 as the bottom product which comprises 3-pentenenitrile, the at least one catalyst, 2-methyl-3-butenenitrile and the remaining portion of the 1,3-butadiene from stream 1 which has not been removed in stream 2, (c) distilling stream 3 in a distillation column K2 to obtain a stream 4 as the top product which comprises 1,3-butadiene, a stream 5 which comprises 3-pentenenitrile and 2-methyl-3-butenenitrile at a side draw of the column, and a stream 6 as the bottom product which comprises the at least one catalyst, (d) distilling stream 5 to obtain a stream 7 as the top product which comprises 2-methyl-3-butenenitrile, and a stream 8 as the bottom product which comprises 3-pentenenitrile, the distillation column K1 used in process step (b) comprising at least one distillation column having a stripping section and/or the distillation column K2 used in process step (c) having distillative separation stages between the feed of stream 3 and the draw of stream 5 being disposed lower in the distillation column K2 than the feed of stream 3, and the at least one catalyst being Ni(O) which contains phosphorus ligands and/or free phosphorous ligands having the formula I: or the ligands having the formula II: