Recovery of hydrogen from gaseous mixtures and improved hydrogenation process

Claim 1

IN A HYDROGENATION PROCESS WHEREIN AN ALKYL AROMATIC IS HYDROGENATED IN THE PRESENCE OF HYDROGEN IN A REACTION ZONE, AND REACTION EFFLUENT IS SEPARATED INTO A LIQUID HYDROGENATED HYDROCARBON STREAM AND A GASEOUS MIXTURE COMPRISING HYDROGEN, METHANE, AND SOME OF SAID HYDROGENATED PRODUCT, THE IMPROVEMENT COMPRISING PASSING A STREAM OF SAID GASEOUS MIXTURE INTO AN ISOTHERMAL ABSORPTION ZONE OPERATED AT SUPERATMOSPHERIC PRESSURE, PASSING A STREAM OF A LOW MOLECULAR WEIGHT LIQUID PARAFFINIC HYDROCARBON INTO SAID ABSORPTION ZONE TO CONTACT SAID GASEOUS MIXTURE THEREIN, WITHDRAWING FORM SAID ABSORPTION ZONE A LIQUID STREAM OF SAID PARAFFINIC HYDROCARBON ENRICHED WITH SAID HYDROGENATED HYDROCARBON, WITHDRAWING A GASEOUS MIXTURE COMPRISING HYDROGEN, METHANE, AND SOME OF SAID PARAFFINIC HYDROCARBON FROM SAID ABSORPTION ZONE AND COOLING IT TO SUBATMOSPHERIC TEMPERATURES BY INDIRECTLY HEAT-EXCHANGING IT WITH COOLANT IN A COOLING ZONE PASSING THE RESULTING COOLED GAESOUS MIXTURE INTO A FIRST LIQUID-VAPOR SEPARATION ZONE OPERATED AT SUPERATMOSPHERIC PRESSURE, WITHDRAWING A GASEOUS STREAM COMPRISING HYDROGEN FROM SAID SEPARATION ZONE AND RECYCLING IT TO SAID COOLING ZONE FOR USE AS SAID COOLANT, RECYCLING SAID GASEOUS STREAM COMPRISING HYDROGEN FROM SAID COOLING ZONE TO SAID REACTION ZONE, WITHDRAWING A LIQUID STREAM COMPRISING METHANE AND SAID PARAFFINIC HYDROCARBON FROM SAID SEPARTION ZONE AND PASSING IT TO A SECOND LIQUID-VAPOR SEPARATION ZONE OPERATED AT A PRESSURE LOWER THAN THAT OF SAID FIRST LIQUID-VAPOR SEPARATION ZONE, AND WITHDRAWING A GASEOUS STREAM COMPRISING METHANE AND A LIQUID STREAM COMPRISING SAID PARAFFINIC HYDROCARBON FROM SAID SECOND LIQUID-VAPOR SEPARATION ZONE AND RECYCLING THESE WITHDRAWN STREAM TO SAID COOLING ZONE FOR USE AS SAID COOLANT, COMBINING SAID LIQUID HYDROGENATED STREAM WITH SAID STREAM COMPRISING PARAFFINIC HYDROCARBON ENRICHED WITH HYDROGENATED HYDROCARBON, PASSING THE RESULTING COMBINED STREAM TO A STABILIZING ZONE, WITHDRAWING A LIQUID STREAM COMPRISING STABILIZED HYDROGENATED HYDROCARBON FROM SAID STABILIZING ZONE, WITHDRAWING A GASEOUS STREAM COMPRISING METHANE AND SAID PARAFFINIC HYDROCARBON FROM SAID STABILIZING ZONE, COOLING IT, AND PASSING IT TO A LIQUID-VAPOR SEPARATION ZONE, AND WITHDRAWING FROM THE LATTER ZONE A LIQUID STREAM COMPRISING SAID PARAFFINIC HYDROCARBON AND RECYCLING IT TO SAID ABSORPTION ZONE.