1. IN A POLYMERIZATION PROCESS WHEREIN PROPYLENE MONOMER IN THE PRESENCE OF HYDROGEN AND A CATALYST CONSISTING OF DIETHYLALUMINUM CHLORIDE AND THE MATERIAL PRODUCED BY CONTACTING TITANIUM TETRACHLORIDE WITH ALUMINUM IS REACTED TO PRODUCE SOLID POLYPROPYLENE, THE REACTION EFFLUENT IS CONTACTED WITH ACETYLACETONE AND PROPYLENE OXIDE AND WASHED WITH LIQUID PROPYLENE, SOLID POLYPROPYLENE IS REMOVED AND THE REMAINING RESIDUE STREAM CONTAINING PROPYLENE, A COMPLEX OF SAID CATALYST AND ACETYL ACETONE AND SOLUBLE POLYMER IS SUBJECTED TO FRACTIONAL DISTILLATION FOR REMOVAL OF PROPYLENE; THE IMPROVEMENT IN THE TREATING OF THE RESIDUE STREAM FROM SAID FRACTIONAL DISTILLATION ZONE WHICH COMPRISES SEPARATING SAID STREAM INTO TWO PHASES, A FIRST PHASE CONTAINING SOLUBLE POLYMER AND PROPYLENE AND A SECOND PHASE CONTAINING SAID COMPLEX AND PROPYLENE; CONTACTING SAID FIRST PHASE WITH PROPYLENE AND SUBJECTING THE RESULTING MIXTURE TO A STRIPPING OPERATION WHEREIN SOLUBLE POLYMER IS RECOVERED AS A BOTTOMS PRODUCT; CONTACTING SAID SECOND PHASE WITH WATER AT INCREASED TEMPERATURES TO REGENERATE SAID ACETYLACETONE AND SUBJECTING THE RESULTING MIXTURE TO INCREASED TEMPERATURES TO RECOVER SAID ACETYLACETONE.