Two-stage propylene polymerization process

Claim 1

A PROCESS FOR THE POLYMERIZATION OF PROPYLENE WHICH COMPRISES CONTACTING A PROPYLENE-CONTAINING FEED STREAM, CONTAINING ABOVE ABOUT 20% PROPYLENE AND SUBSTANTIALLY FREE FROM HYDROCARBONS HEAVIER THAN PROPANE, WITH A LIQUID PHOSPHORIC ACID CATALYST OF A CONCENTRATION IN THE RANGE OF FROM ABOUT 50 TO 90 PERCENT H3PO4 IN A PRIMARY POLYMERIZATION ZONE AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 350*F. TO 500*F., A PRESSURE IN THE RANGE OF FROM ABOUT 300 TO 2000 P.S.I.G., AND A SPACE VELOCITY ABOVE 0.15 L. H. S. V. TO CONVERT FROM 30 TO 60 PERCENT OF THE PROPYLENE CONTAINED IN SAID FEED STREAM PREDOMINANTLY TO HYDROCARBONS BOILING IN THE RANGE OF FROM ABOUT 100*F. TO 200*F.; RECOVERING THE HYDROCARBON EFFLUENT FROM SAID PRIMARY POLYMERIZATION ZONE AND PASSING SAID EFFLUENT INTO A PRIMARY SEPARATION ZONE TO SEPARATE AN OVERHEAD FRACTION BOILING BELOW ABOUT 100*F. AND A BOTTOMS FRACTION BOILING ABOVE SAID TEMPERATURE; CONTACTING SAID OVERHEAD FRACTION WITH A LIQUID PHOSPHORIC ACID CATALYST OF A CONCENTRATION IN THE RANGE OF FROM ABOUT 100 TO 110 PERCENT H3PO4 IN A SECONDARY POLYMERIZATION ZONE AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 300*F. TO 400*F., A PRESSURE IN THE RANGE OF FROM ABOUT 250 TO 1500 P.S.I.G. AND A SPACE VELOCITY ABOVE 0.15 L. H. S. V.; RECOVERING THE HYDROCARBON EFFLUENT FROM SAID SECONDARY POLYMERIZATION ZONE AND PASSING SAID EFFLUENT INTO A SECONDARY SEPARATION ZONE TO SEPARATE AN OVERHEAD FRACTION BOILING BELOW ABOUT 100*F AND A BOTTOMS FRACTION BOILING ABOVE SAID TEMPERATURE, AND MIXING SAID BOTTOMS FRACTIONS FROM SAID PRIMARY AND SECONDARY SEPARATION ZONES TO FORM THE DESIRED POLYMER PRODUCT.