Process for the manufacture of tetramethylethylene

Claim 1

A PROCESS FOR THE MANUFACTURE OF TETRAMETHYLETHYLENE COMPRISING CONTINUOUSLY PASSING A PROPYLENE-CONTAINING STREAM HAVING SUBSTANTIALLY NO OTHER OLEFIN PRESENT IN LIQUID PHASE AND UNDER TEMPERATURE CONDITIONS BETWEEN 25* C. AND 94* C. OVER A SUBSTANTIALLY WATER-FREE CATALYST BED COMPRISING A SOLID BF3-ADSORBING CATALYST CARRIER WHICH IS ITSELF RELATIVELY INACTIVE TOWARD OLEFIN POLYMERIZATION AND WHICH CONTAINS BETWEEN 0.5% AND 12% BY WEIGHT OF SAID CATALYST BED OF ADSROBED BORON TRIFLUORIDE AT A SPACE VELOCITY SUFFICIENTLY HIGH TO RESTRICT THE AMOUNT OF POLYMERS FORMED PER PASS TO LESS THAN 20% BY WEIGHT OF THE TOTAL FLOW, AND THEREAFTER INTRODUCING THE POLYMER-CONTAINING STREAM THUS PRODUCED INTO AN INTERMEDIATE SECTION OF A FRACTIONATING COLUMN, IN WHICH THE HEAD TEMPERATURE IS MAINTAINED WITHIN 20* C. OF THE CRITICAL TEMPERATURE OF THE DISTILLATE, AND THEREIN SEPARATING THE FEED INTO AN OVERHEAD FRACTION COMPRISING POLYMER-FREE PROPYLENE AND A BOTTOMS FRACTION COMPRISING PROPYLENE-FREE POLYMER, COMBINING SAID HEADS FRACTION WITH SAID PROPYLENE-CONTAINING STREAM FOR RECYCLING, AND SIMULTANEOUSLY PASSING SAID BOTTOMS STREAM INTO A SECOND FRACTIONATING SYSTEM WHEEREIN TETRAMETHYLETHYLENE IS SEPARATED FROM OTHER CONSTITUENTS OF SAID STREAM BY FRACTIONAL DISTILLATION.