Process for desorbing solid adsorbents

Claim 1

IN A METHOD OF SEPARATING A LOW-MOLECULAR-WEIGHT NORMAL ALIPHATIC HYDROCARBON FROM A FEED MIXTURE CONTAINING SAME AND OTHER HYDROCARBONS, SELECTED FROM THE GROUP CONSISTING OF BRANCH-CHAIN HYDROCARBONS, CYCLIC HYDROCARBONS, AND MIXTURES THEREOF, IN WHICH SAID FEED MIXTURE IS PASSED THROUGH A ZEOLITIC MOLECULAR SIEVE SELECTIVE FOR NORMAL ALIPHATIC HYDROCARBONS, AT A FIRST TEMPERATURE, WHEREBY SAID NORMAL ALIPHATIC HYDROCARBON IS SELECTIVELY ADSORBED UNTIL SAID SIEVE IS AT SAID FIRST TEMPERATURE AND SATURATED TO EQUILIBRIUM CAPACITY AT SAID FIRST TEMPERATURE, AND DESORBING SAID SIEVE BY SWEEPING SAID SIEVE WITH THE SUPERHEATED VAPORS OF THE SAME HYDROCARBON WHICH IS ADSORBED, AT A SECOND TEMPERATURE HIGHER THAN SAID FIRST TEMPERATURE, WHEREBY THE TEMPERATURE OF SAID SIEVE IS INCREASED TO SAID SECOND TEMPERATURE, UNTIL SAID SIEVE IS SATURATED TO EQUILIBRIUM CAPACITY AT SAID SECOND TEMPERATURE, THE IMPROVEMENT WHICH COMPRISES DESORBING SAID SIEVE IMMEDIATELY AFTER THE PASSAGE OF SAID FEED MIXTURE THERETHROUGH, MIXING THE INITIAL EFFLUENT FROM THE DESORPTION STEP WITH FURTHER FEED MIXTURE UNTIL THE DESORPTION EFFLUENT IS THE HYDROCARBON WHICH IS ADSORBED SUBSTANTIALLY FREE OF OTHER HYDROCARBONS OF SID FEED MIXTURE, RECOVERING FROM THE DESORPTION EFFLUENT THE HYDROCARBON WHICH IS ADSORBED IN AN AMOUNT CORRESPONDING TO THE DIFFERENCE IN EQUILIBRIUM CAPACITIES OF SAID SIEVE AT SAID FIRST AND SECOND TEMPERATURES, DISPLACING INTERSTITIAL HYDROCARBONS FROM THE DESORBED SIEVE BY PASSING TROUGH SAID SIEVE A NON-ADSORBABLE GAS HEATED TO SUBSTANTIALLY SAID SECOND TEMPERATURE, COOLING SAID SIEVE BY PASSING A COOL, NON-ADSORBABLE GAS THROUGH SAID SIEVE, THE SAME GAS BEING UTILIZED FOR DISPLACING INTERSTITIAL HYDROCARBONS AND COOLING SAID SIEVE, AND CONTACTING SAID SIEVE WITH ADDITIONAL QUANTITIES OF SAID FEED MIXTURE.