Patent ID: 8410299

Claim:
A process for preparing 3-pentenenitrile, comprising the following process steps: (a) isomerizing a reactant stream which comprises 2-methyl-3-butenenitrile over at least one dissolved or dispersed isomerization catalyst to give a stream 1 which comprises the at least one isomerization catalyst, 2-methyl-3-butenenitrile, 3-pentenenitrile and (Z)-2-methyl-2-butenenitrile, (b) distilling stream 1 at a pressure of 0.1 mbar to 100 bar to obtain a stream 2 as the top product which comprises 2-methyl-3-butenenitrile, 3-pentenenitrile and (Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product which comprises the at least one isomerization catalyst, (c) distilling stream 2 at a bottom temperature of 40 to 180° C. and a pressure of 10 mbar to 500 mbar to obtain a stream 4 as the top product which, compared to stream 2, is enriched in (Z)-2-methyl-2-butenenitrile, based on the sum of all pentenenitriles in stream 2, and a stream 5 as the bottom product which, compared to stream 2, is enriched in 3-pentenenitrile and 2-methyl-3-butenenitrile, based on the sum of all pentenenitriles in stream 2, (d) distilling stream 5 at a pressure of 0.001 bar to 100 bar to obtain a stream 6 as the bottom product which comprises 3-pentenenitrile and a stream 7 as the top product which comprises 2-methyl-3-butenenitrile, the (Z)-2-methyl-2-butenenitrile-depleted 2-methyl-3-butenenitrile being recycled to step (a); and wherein the distilling in each of steps (b), (c) and (d) is carried out without the addition of an aqueous solution.