Vapor phase isomerization process

Claim 1

IN A PROCESS WHEREIN SATURATED, ALIPHATIC HYDROCARBON FEED MATERIAL HAVING AT LEAST FOUR CARBON ATOMS PER MOLECULE IS ISOMERIZED UNDER ISOMERIZATION CONDITIONS, INCLUDING TEMPERTURE WITHIN THE RANGE OF ABOUT 200 TO 400*F. AND RESIDENCE TIME WITHIN THE RANGE OF ABOUT 0.1 TO 3 MINUTES, BY PASSAGE THROUGH A MASS OF PARTICLE FORM CATALYST IN A CONFINED ISOMERIZATION ZONE, SAID CATALYST COMPRISING A METAL HALIDE OF THE FRIEDEL-CRAFTS TYPE ON A POROUS CARRIER AND WHEREIN THE FEED MATERIASL CONTAINS MATERIALS OTHER THAN THE SATURATED HYDROCARBONS TO BE ISOMERIZED, WHICN TEND TO CAUSE RAPID DETERIORATION OF THE ISOMERIZATION OPERATION, AND WHEREIN METAL HALIDE VAPORS ARE INTRODUCED INTO SAID ZONE MIXED WITH A SUITABLE INERT CARRIER GAS AT LEAST INTERMITTENTLY DURING THE ISOMERIZATION ON-STREAM PERIOD AND GASEOUS PRODUCT CONTAINING THE ISOMERIZED HYDROCARBON MATERIAL IS WITHDRAWN FROM SAID ZONE, THE IMPROVEMENT IN COMBINATION THEREWITH WHICH COMPRISES: CONTROLLING THE RATE OF METAL HALIDE VAPOR INTRODUCTION INTO SAID ZONE DURING THE ON-STREAM PERIOD IN EXCESS OF THAT REQUIRED TO SATURATE SAID PARTICLE FORM CARRIER MATERIAL AND SUFFICIENT TO INSURE THE PRESENCE OF METAL HALIDE VAPORS IN THE GASEOUS PRODUCT WITHDRAWN FROM SAID ZONE IN AN AMOUNT AVERAGING AT LEAST 0.005% BY WEIGHT OF THE TOTAL HYDROCARBON MATERIAL INTRODUCED TO SAID ZONE DURING THE ON-STREAM PERIOD, CONTROLLING THE TOTAL PRESSURE IN SAID ISOMERIZATION ZONE WITHIN THE RANGE OF ABOUT 400 TO ABOUT 900 P.S.I.A. AND INTRODUCING FREE HYDROGEN TO SAID ZONE AT A RATE CONTROLLED TO PROVIDE A HYDROGEN PARTIAL PRESSURE WITHIN THE RANGE OF APPROXIMATELY 385 TO ABOUT 800 P.S.I.A. AND A PROPORTION OF HYDROGEN RELATIVE TO TOTAL GASEOUS MATERIAL FLOWING THROUGH THE ISOMERIZATION ZONE, EXCLUSIVE OF ANY METAL HALIDE, WHICH IS SUFFICIENT TO MAINTAIN SAID HYDROCARBON MATERIAL IN THE GASEOUS PHASE, SAID PROPORTION BEING IN ANY CASE GREATER THAN 0.43