Pressure cycle for molecular sieve separation of normal paraffins from hydrocarbon mixtures

Claim 1

IN A CYCLIC PROCESS FOR SEPARATING A HYDROCARBON FEED VAPOR MIXTURE OF NORMAL PARAFFINS AND NON-STRAIGHT CHAIN HYDROCARBONS BY CONTACT WITH A BED OF ZEOLITIC MOLECULAR SIEVE HAVING PORE SIZE OF ABOUT 5 ANGSTROMS AT TEMPERATURE BELOW 900*F. AND A FIRST HIGHER PRESSURE FOR ADSORPTION OF A KEY NORMAL PARAFFIN, AND THEREAFTER DESORPTION OF SAID KEY NORMAL PARAFFIN AT SUBSTANTIALLY THE ADSORPTION TEMPERATURE AND LOWER SECOND PRESSURE, THE IMPROVEMENT COMPRISING THE STEPS OF: PROVIDING A VAPOR MIXTURE OF SAID HYDROCARBON FEED AND A NORMAL PARAFFIN PURGE COMPONENT FOR CONTACT WITH THE MOLECULAR SIEVE BED DURING THE ADSORPTION STEP, SAID PURGE COMPONENT BEING LESS STRONGLY ADSORBABLE THAN THE KEY NORMAL PARAFFIN BY THE MOLECULAR SIEVE BUT HAVING AT LEAST FOUR CARBON ATOMS PER MOLECULE, AND IN QUANITY SUFFICIENT TO PROVIDE A MOLAR RATIO OF BETWEEN 10:1 AD 1:4 RELATIVE TO THE QUANTITY OF NORMAL PAFAFFIN IN THE HYDROCARBON FEED; INTRODUCING SAID VAPOR MIXTURE INTO A FIRST END OF SAID MOLECULAR SIEVE