Method of separating gas mixtures by adsorption

Claim 1

A PROCESS FOR PURIFYING AN ETHYLENE GAS STREAM WHICH COMPRISES PROVIDING A FIXED BED OF CRYSTALLINE ZEOLITIC MOLECULAR SIEVE MATERIAL HAVING PORE SIZES OF AT LEAST 4 ANGSTROM UNITS; PROVIDING AN ETHYLENE FED GAS STREAM CONTAINING AN ADMIXTURE OF CARBON DIOXIDE IMPURITY IN ETHYLENE GAS PRODUCT; CONTACTING SUCH STREAM WITH SAID BED AS AN ADSORPTION STEP BY INTRODUCING SAID FEED GAS STREAM AT THE INLET END THEREOF TO ADSORB AT LEAST PART OF SAID CARBON DIOXIDE IMPURITIES AND PART OF SAID ETHYLENE PRODUCT GAS IN SAID BED OF CRYSTALLINE ZEOLITE MOLECULAR SIEVE MATERIAL, DISCHARGING A CARBON DIOXIDE IMPURITY DEPLETED ETHYLENE PRODUCT GAS STREAM FROM THE OPPOSITE END OF SAID BED; ESTABLISHING A CARBON DIOXIDE IMPURITY ABSORPTION FRONT AT SAID INLET END; PROGRESSIVELY MOVING SUCH FRONT LONGITUDINALLY THROUGH SAID FIXED BED TOWARD THE OPPOSITE END THEREOF THEREBY DISPLACING SAID ETHYLENE PRODUCT GAS WITH CARBON DIOXIDE IMPURITY IN SAID CRYSTALLINE ZEOLITE MOLECULAR SIEVE MATERIAL AS THE RESULT OF THE MOVEMENT OF SAID CARBON DIOXIDE IMPURITY ADSORPTION FRONT; TERMINATING THE INTRODUCTION OF SAID FEED GAS STREAM TO SAID BED TO COMPLETE THE ADSORPTION STEP; AS A REGENERATED STEP INTRODUCING A HOT PURGE GAS HAVING A TEMPERATURE SUBSTANTIALLY HIGHER THAN THE TEMPERATURE AT WHICH THE ABSORPTION STEP TAKES PLACE TO THE INLET END OF SAID BED AND FLOWING SAID PURGE GAS IN THE SAME DIRECTION AS SAID