BF.sub.3 recovery process

A process for the oligomerization of an olefin composition and recovery of BF.sub.3, comprising contacting an olefin composition in a reaction zone with BF.sub.3 and in the presence of a BF.sub.3 -promoter complex, under conditions to oligomerize said olefin, forming a crude polyolefin oligomerization reaction product mixture containing dissolved BF.sub.3 and BF.sub.3 -promoter complex;

• recovering crude oligomerization reaction product mixture containing dissolved BF.sub.3 and BF.sub.3 -promoter complex;
• vaporizing BF.sub.3 from said crude oligomerization reaction product mixture in a vaporization zone at a temperature insufficient to decompose BF.sub.3 or BF.sub.3 promoter complex in said mixture;
• contacting BF.sub.3 from said vaporization zone with a liquid olefin composition in an absorption zone under conditions to absorb BF.sub.3 in said liquid olefin composition with minimal oligomerization of the olefin composition in the absorption zone, forming a mixture comprising liquid olefin composition and BF.sub.3.