Increasing efficiency of hydrocarbon separation with adsorbents

Claim 1

IN A PROCESS FOR SEPARATION OF HYDROCARBONS OF A SELECTED TYPE FROM A MIXTURE THEREOF WITH HYDROCARBONS OF OTHER TYPES WHEREIN SAID MIXTURE IS CONTACTED WITH A BODY OF A ZEOLITIC MOLECULAR SIEVE ADSORBENT OF A SELECTED PORE SIZE AT A SELECTED PERESSURE AND TEMPERATURE, AND AN EFFLUENT STREAM ESSENTIALLY FREE OF SAID SELECTED TYPE HYROCARBONS IS COLLECTED, DURING AN ABSORPTION STEP, AND ABSORBED HYDROCARBONSS ARE SUBSEQUENTLY DESORBED FROM SAID ABSORBENT, IN A DESORPTION STEP, BY RECYCLING A HEATED STREAM OF DESORBATE THROUGH SAID ADSORPTION ZONE, THE IMPROVEMENT WHICH COMPRISES DISCONTINUING THE FEEDING OF SAID MIXTURE OF SAID BODY OF ADSORBENT DURING THE LATTER PORTION OF THE ADSORBTION STEP, AT A TIME PRIOR TO THE NORMAL TIME FOR APPEARANCE IN THE EFFLUENT OF THE TYPE OF HYDROCARBON BEING ADSORBED, THEREAFTER INJECTING INTO SAID BODY OF ADSORBENT DURING THE LATTER PORTION OF SAID ADSORPTION STEP A QUANTITY OF RECYCLED DESORBATE AT ABOUT THE SAME ADSORPTION TEMPERATURE WHILE CONTINUING TO COLLECT AN EFFLUENT STREAM ESSENTIALLY FREE OF SAID SELECTED TYPE HYDROCARBON, AND THEREAFTER DESORBING SAID BODY OF ADSORBENT IN THE MANNER AFORESAID.