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 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 catalyst flows through the first, second and third reaction zones along with reactants and products,
• wherein any Lewis acid promoter introduced into a reaction zone flows through the reaction zone along with reactants, products and catalysts,
• wherein first catalyst flowing through the first reaction zone is recycled into the first reaction zone, and wherein catalyst flowing through the third reaction zone is recycled into the third reaction zone,
• wherein the first reaction zone is substantially free of the Lewis acid promoter, which flows through the third reaction zone (Z3),
• wherein the flow of recycled catalyst is controlled to avoid the introduction of the Lewis acid promoter, which flows through the third reaction zone (Z3), into the first reaction zone (Z1),
• wherein first catalyst flowing from the first reaction zone is concentrated in one or more distillation steps and recycled in at least one catalyst recycle stream to the first reaction zone,
• wherein a portion of the catalyst recycle stream to the first reaction zone is contacted with a first extraction solvent in a first liquid/liquid extraction step to produce a solvent phase and a raffinate phase,
• wherein the solvent phase from the first liquid/liquid extraction step comprises said first catalyst and wherein the raffinate phase from the first liquid/liquid extraction step comprises catalyst degradation products and reaction byproducts,
• wherein said third catalyst is not contacted with said first extraction solvent in said first liquid/liquid extraction step,
• wherein said third catalyst flowing from the third reaction zone is contacted with an extraction solvent in a separate liquid/liquid extraction step, which is different from said first liquid/liquid extraction step, and
• wherein said third catalyst is recovered from the separate liquid/liquid extraction step and recycled to the third reaction zone, but not to the first reaction zone.