Method of preventing sulfur dioxide deterioration of platinum-group metal reforming catalyst

Claim 1

IN THE REFORMING OF A NAPHTHA FRACTION IN THE PRESENCE OF PARTICLE-FORM SOLID PLATINUM-GROUP METAL REFORMING CATAALYST WHEREIN THE AFORESAID PLATINUM-GROUP METAL REFORMING CATALYST IS DISTRIBUTED IN A PLURALITY OF REACTION ZONES COMPRISING AT LEAST A HEAD REACTION ZONE AND A TAIL REACTION ZONE, WHEREIN A HEAD REACTANT HEATER HAVING REACTANT TUBES THEREIN IS UP-STREAM OD SAID HEAD REACTOR, WHEREIN A TAIL REACTANT HEATER HAVING REACTANT TUBES THEREIN IS UP-STREAM OF SAID TAIL REACTOR, WHEREIN THE NAPTHA FRACTION TO BE REFORMED IS HEATED TO AT LEAST 800* F. IN SAID HEAD HEATER AND THE HEATED NAPTHA PASSED VIA A TRANSFER LINE TO SAID REACTOR HEAD REACTOR TRHOUGH A BED OF SAID PLATINUM-GROUP METAL CATALYST IN SAID HEAD REACTOR WHEREIN THE EFFLUENT OF SAID HEAD REACTOR FOLWS THROUGH THE REACTANT HEATER TUBES IN SAID TAIL-HEATER TO SAID TAIL REACTOR AND THROUGH A BED OF SAID PLATINUM-GROUP METAL CATALYST IN SAID TAIL REACTOR, WHEREIN THE EFFLUENT OF SAID TAIL REACTOR FLOWS TO A LIQUID-GAS SEPARATOR IN WHICH HYDROGEN AND LIGHT HYDROCARBONS ARE SEPARATED FROM C4 AND HEAVIER HYDROCARBONS, WHEREIN CARBONACEOUS MATERIAL IS DEPOSITED ON SAID CATALYST DEACTIVATING SAID CATALYST WHEREIN SAID CATALYST IS REACTIVATED BY COMBUSTION IN A FLOWING STREAM OF INERT GAS CONTAINING FREE OXYGEN HEATED IN SAID HEAD AND TAIL HEATERS, WHEREIN IRON SULFIDE IS DEPOSITED ON THE INNER PERIPHERY OF THE REACTANT HEATER TUBES AT LEASST SAID HEAD HEATER AND WHEREIN SAID HEATERS REACTORS, AND INTERVENING PIPING ARE PURGED OF HYDROGEN AND HYDROCARBONS BEFORE REACTIVTING SAID CATALYST, THE IMPROVEMENT WHICH COMPRISES SUBJECTING THE REACTANT HEATER TUBES OF AT LEAST SAID HEAD HEATER TO A SULFUR PURGE COMPRISING PASSING A SULFUR PURGE MIXTURE, COMPRISING INERT GAS CONTAINING FREE OXYGEN THROUGH SAID REACTANT HEATER TUBES TO PRODUCE GAS CONTAINING SULFUR DIOXIDE FROM SAID IRON SULFIDE WHILE REGULATING THE OXYGEN CONCENTRATION OF SAID SULFUR PURGE MIXTURE TO MAINTAIN A TEMPERATURE NOT EXCEEDING ABOUT 1000* F. SAID REACTANT HEATER TUBES, VENTING SAID INERT GAS WITHOUT CONTACTING THE AFORESAID PLATINUM CATALYST, CONTINUING TO PASS SAID SULFUR PURGE MIXTURE THROUGH SAID REACTANT HEATER TUBES AND TO BENT GAS CONTAINING SULFUR DIOXIDE UNTIL SULFUR DIOXIDE IS NOT DETECTED IN SAID VENTED GAS, AND THEN BURNING SAID CARBONACEOUS MATERIAL DEPOSITED ON SAID CATALYST.