Patent ID: 8058466

Claim:
A process for preparing 3-pentenenitrile by hydrocyanating 1,3-butadiene, which comprises the following process steps: (bâ€²) distillation of 1,3-butadiene comprising water, 1- and 2-butenes and a stabilizer in a distillation apparatus K 4 to obtain a stream 15 as the bottom product, which comprises dried 1,3-butadiene, 1- and 2-butenes and the stabilizer, and a stream 16 as the top product, which comprises an azeotropic 1,3-butadiene/water mixture, condensation of the stream 16 in a condenser W, transfer of the resulting condensate (stream 17 ) into a phase separation apparatus, recycling of the upper liquid phase (stream 18 ) consisting of 1,3-butadiene as reflux to the column K 4 , and discharge of the lower liquid aqueous phase (stream 19 ), (a) reaction of stream 15 in a reactor R 1 with hydrogen cyanide over at least one catalyst (stream 6 d ) to obtain a stream I which comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one catalyst in the form of homogeneously dissolved nickel complexes or nickel(0) complexes and phosphorus ligands, unconverted 1,3-butadiene, and 1- and 2-butenes, with or without residues of unconverted hydrogen cyanide, (b) distillation of stream 1 in a distillation apparatus K 1 to obtain a stream 2 as the top product, which comprises the predominant portion of the 1,3-butadiene from stream 1 , and to obtain a stream 3 as the bottom product, which comprises 3-pentenenitrile, the at least one catalyst, 2-methyl-3-butenenitrile, 1- and 2-butenes and the remaining proportion of the 1,3-butadiene from stream 1 which has not been removed in stream 2 , (c) distillation of stream 3 in a distillation apparatus K 2 to obtain a stream 5 at a side draw of the column, which 3-pentenenitrile and 2-methyl-3-butenertitrile, a stream 6 as the bottom product, which comprises the at least one catalyst, and a stream 4 as the top product, (d) compression of stream 4 in the compressor VI, discharge of a gaseous substream 4 b which comprises 1- and 2-butenes, transfer of the compressed stream 4 a into the condenser W 1 , combined cond. With stream 2 from b) in combined condensation of this stream 2 from b) and transfer of the condensate as stream 9 , partly as reflux to the column K 1 (stream 9 b ), partly as return stream into the reactor R 1 (stream 9 a ), and (e) distillative separation of stream S to obtain 3-pentenenitrile and 2-methyl-3-butenenitrile.