Process for making nitriles

A process for making adiponitrile, said process comprising the steps of:

• (a) reacting in a first reaction zone a mixture comprising 1,3-butadiene (BD) and hydrogen cyanide (HCN) in the presence of a first catalyst comprising zero-valent Ni and a first phosphorus-containing ligand to produce a reaction product comprising 3-pentenenitrile (3PN) and 2-methyl-3-butenenitrile (2M3BN);
• (b) isomerizing at least a portion of the 2M3BN of step (a) in a second reaction zone in the presence of a second catalyst comprising zero-valent Ni and a second phosphorus-containing ligand to produce a reaction product comprising 3PN;
• and
• (c) reacting in a third reaction zone a mixture comprising 3PN from step (b) and hydrogen cyanide (HCN) in the presence of a third catalyst comprising zero-valent Ni and a third phosphorus-containing ligand and in the presence of Lewis acid promoter to produce a reaction product comprising adiponitrile,
• wherein the first catalyst flows through the first reaction zone along with reactants and products,
• wherein the second catalyst flows through the second reaction zone along with reactants and products,
• wherein the third catalyst flows through the third reaction zone along with reactants and products,
• wherein the reaction product of step (a) further comprises dinitriles comprising adiponitrile (ADN) and methylgiutaronitrile (MGN),
• wherein at least a portion of first catalyst flowing from the first reaction zone is concentrated in one or more distillation steps and recycled in at least one first catalyst recycle stream to the first reaction zone,
• wherein a portion of the first catalyst recycle stream is contacted with a first extraction solvent in a first liquid/liquid extraction step to produce a solvent phase and a raffinate phase,
• wherein a separate liquid/liquid extraction step is used to treat the product from the third reaction zone such that said third catalyst is not contacted with said extraction solvent in said first liquid/liquid extraction step,
• wherein the first liquid/liquid extraction step comprises introducing a portion of the first catalyst recycle stream, a first extraction solvent stream and a dinitrile recycle stream comprising adiponitrile (ADN) into a first liquid/liquid extraction zone,
• wherein the first liquid/liquid extraction step further comprises separating liquids in the first liquid/liquid extraction zone into a first solvent phase comprising first extraction solvent and first catalyst and a first raffinate phase comprising adiponitrile (ADN), methylglutaronitrile (MGN), compounds with a higher boiling point than adiponitrile (ADN) and compounds with a lower boiling point than methylglutaronitrile (MGN);
• wherein first catalyst from said solvent phase obtained in said liquid/liquid extraction step is recycled to the first reaction zone or the second reaction zone or both the first and second reaction zone,
• wherein said first raffinate phase is distilled in one or more distillation steps to separate adiponitrile (ADN) and methylglutaronitrile (MGN) from compounds with a higher boiling point than adiponitrile (ADN) and compounds with a lower boiling point than methylglutaronitrile (MGN) to obtain a first refined dinitrile stream,
• wherein said first refined dinitrile stream is further distilled to remove methylglutaronitrile (MGN) from the first refined dinitrile stream to obtain a second refined dinitrile stream enriched in adiponitrile, and
• wherein at least a portion of said second refined dinitrile stream is recycled to the liquid/liquid extraction step.