Process for recovery of an aliphatic diol oligomerization solvent

In the process for the recovery of an aliphatic diol reaction solvent in the processing scheme wherein ethylene is oligomerized at elevated temperature and pressure by contact with a solution of a nickel complex catalyst in an aliphatic diol solvent to afford a reaction product made up of (a) a liquid solvent phase containing dissolved catalyst, (b) a liquid hydrocarbon phase comprising ethylene oligomers containing dissolved ethylene, catalyst and diol solvent and (c) gaseous ethylene, said reaction product being passed to a series of phase separation zones whereby gaseous ethylene and a substantial portion of the diol reaction solvent containing dissolved catalyst are separated and recycled to the oligomerization reaction zone with a minor portion of the separated catalyst-containing reaction solvent being passed to a fractionation zone for removal of light ends and spent catalyst, prior to its recycle to the oligomerization process;

• the improvement which comprises, contacting the catalyst-containing, diol reaction solvent in the fractionation zone with a minor amount of an alkali metal hydroxide thereby minimizing the formation of oxygenated degradation products from the diol solvent during fractionation.