Process for rejecting heavy hydrocarbons from light hydrocarbons gases

A cyclic process for rejecting heavy hydrocarbons from a natural gas stream including methane, ethane, propane and butane, heavy hydrocarbons including C.sub.10+ hydrocarbons, carbon dioxide, and water, prior to introducing said natural gas stream to a membrane unit for the separation of carbon dioxide from the natural gas stream, said process comprising:

• a) contacting the natural gas stream comprising from about 500 ppm to about 1 wt-% heavy hydrocarbons with a regenerable adsorbent comprising a high silica zeolite molecular sieve having a silica to alumina ratio greater than 20 and a pore opening greater than about 4.5 Angstroms, said regenerable adsorbent being selected from at least one of the group consisting of silicalite, zeolite Beta, boggsite, chabasite, faujasite, EMC-2, zeolite L, mordenite, offretite, ferrierite, ZSM-5, ZSM-11, ZSM-18, ZSM-57, EU-1, zeolite A, ZK-5, zeolite Rho, and mixtures thereof to provide a purified gas stream essentially free of said heavy hydrocarbons;
• b) terminating the contacting of the natural gas stream with the regenerable adsorbent and contacting said regenerable adsorbent with at least a portion of a non-permeate stream from the membrane zone to regenerate said adsorbent and recovering a spent regeneration gas stream;
• c) cooling said regeneration gas stream to provide a cooled spent regeneration gas stream;
• and,
• d) combining said cooled spent regeneration gas stream with said non-permeate stream.