Molecular sieve adsorption process utilizing a two-stage desorption technique

Claim 1

THE PROCESS WHICH COMPRISES CHARGING TO A BED OF MOLECULAR SIEVES OF 5 ANGSTROM UNITS CHANNEL DIAMETER AT A PRESSURE OF AT LEAST ONE ATMOSPHERE AND AT A TEMPERATURE LESS THAN 100*F. A REFORMATE CONTAINING AROMATICS AND STRAIGHT CHAIN PARAFFING, RECOVERING FROM THE SIEVES AN UNADSORBED FIRST PRODUCT PERCOLATE FRACTION RICHER IN AROMATICS THAN SAID REFORMATE, DISCONTINUING THE CHARGING OF SAID REFORMATE TO SAID BED OF MOLECULAR SIEVES BEFORE THE COMPOSITION OF SAID PERCOLATE INDICATES A SUBSTANTIAL DECREASE IN THE DEGREE OF SEPARATION OF SAID REFORMATE, DRAINING FROM SAID BED OF MOLECULAR SIEVES LIQUID HELD UP THEREIN BUT CORRESPONDING SUBSTANTIALLY IN COMPOSITION TO SAID REFORMATE, THEREAFTER IN A LOW TEMPERATURE PURGING STAGE FLOWING A PURGING GAS THROUGH SAID BED AT A TEMPERATURE BELOW 100*F. AT A SPACE VELOCITY OF AT LEAST 20 VOLUMES (STP) OF GAS PER VOLUME OF MOLECULAR SIEVES PER HOUR, FOR A GAS THROUGHPUT FROM 100 TO 1,000 VOLUMES (STP) OF GAS PER VOLUME OF MOLECULAR SIEVES, RECOVERING FROM SAID PURGING GAS A SECOND PRODUCT HYDROCARBON FRACTION RICHER IN STRAIGHT CHAIN PARAFFINS THAN SAID REFORMATE, THEREAFTER IN A HIGH TEMPERATURE PURGING STAGE FLOWING A PURGING GAS THROUGH SAID BED AT A TEMPERATURE FROM 500 TO 650*F., A SPACE VELOCITY OF AT LEAST 20 VOLUMES (STP) OF GAS PER VOLUME OF MOLECULAR SIEVES PER HOUR, FOR A GAS THROUGHPUT FROM 100 TO 1,000 VOLUMES (STP) OF GAS PER VOLUME OF MOLECULAR SIEVES, RECOVERING FROM SAID PURGING GAS A THIRD FRACTION OF SAID REFORMATE, RICHER IN AROMATICS THAN SAID REFORMATE, COMBINING SAID FIRST AND THIRD PRODUCTS TO FORM A HIGH OCTANE GASOLINE PRODUCT AND RECYCLING SAID SECOND FRACTION RICHER IN STRAIGHT CHAIN PARAFFINS THAN SAID REFORMATE TO CATALYTIC REFORMING.