Extraction solvent control for reducing stable emulsions

A process for recovering diphosphonite-containing compounds from a feed mixture comprising diphosphonite-containing compounds, organic mononitriles, organic dinitriles and a Lewis acid in a multistage countercurrent liquid-liquid extractor with extraction solvent comprising aliphatic hydrocarbon, cycloaliphatic hydrocarbon or a mixture of aliphatic and cycloaliphatic hydrocarbon, said process comprising:

• a) flowing the feed mixture to the first stage of the multistage countercurrent liquid-liquid extractor;
• and
• b) contacting the feed mixture with extraction solvent in the multistage countercurrent liquid-liquid extractor,
• wherein the first stage of the multistage countercurrent liquid-liquid extractor comprises a mixing section and a settling section, wherein the mixing section provides a mixed phase comprising a light phase and a heavy phase, wherein a light phase separates from a heavy phase in the settling section, wherein a mixed phase comprising a heavy phase, light phase is present in the settling section between the light phase and the heavy phase, wherein the light phase comprises extraction solvent and extracted diphosphonite-containing compounds, wherein the heavy phase comprises organic mononitriles and organic dinitriles, wherein at least a portion of the light phase is withdrawn from the settling section and treated to recover diphosphonite-containing compounds extracted into the light phase, wherein at least a portion of the heavy phase is passed to the second stage of the multistage countercurrent liquid-liquid extractor, and wherein the process further comprises at least one of the following additional steps:
• (i) withdrawing a portion of the heavy phase from the settling section of the first stage of the multistage countercurrent liquid-liquid extractor and recycling the withdrawn heavy phase to the settling section of the first stage of the multistage countercurrent liquid-liquid extractor;
• (ii) withdrawing a portion of the light phase from the settling section of the first stage of the multistage countercurrent liquid-liquid extractor and recycling the withdrawn light phase to the mixing section of the first stage of the multistage countercurrent liquid-liquid extractor;
• (iii) introducing a Lewis base into the settling section of the first stage, wherein the first stage of the multistage countercurrent liquid-liquid extractor comprises a mixer-settler, and wherein a complex of Lewis acid and Lewis base is formed in the settling section in the mixer-settler of the first stage;
• and
• (iv) adding a polyamine to the mixing section of the first stage.