GB888952A - Improvements in or relating to the separation of normal olefins from iso-olefins - Google Patents

Abstract

In the vapour phase separation of normal from iso-olefins by adsorption of the former on a molecular sieve, the polymerization activity of the sieve is reduced by contacting with a fluid at elevated temperature. The fluid may be a gas, e.g. natural gas, methane, ethane or nitrogen at 400 DEG -800 DEG F. for 2-8 hours, or a liquid, e.g. liquid isobutylene or a polymer thereof at 200 DEG -500 DEG F. for 0,5-2 hours. In the latter case after the liquid is drained off the sieve is treated with an inert gas at 400 DEG -800 DEG F. Using a 5 sieve, suitable conditions are 60 DEG -130 DEG F. at a rate of 0,5-10 wt./hr./wt. The sieve may be in tablet or pellet form, preferably without a clay binder.ALSO:In the purification of iso-olefins by adsorbing n-olefinic impurities on a molecular sieve, the polymerisation activity of the sieve is first reduced by contact with a fluid at elevated temperature. In one embodiment the sieve is contacted with an inert gas, e.g. natural gas, methane, ethane or nitrogen for 2-8 hours at 400 DEG F.-800 DEG F., the gas being recycled continuously. In another embodiment the sieve is first contacted with isobutylene or a polymer thereof at 200 DEG F.-500 DEG F. for 0.5-2 hours, the bed being flooded with liquid and held at the desired temperature and afterwards treated with an inert gas at 400 DEG F.-800 DEG F. Isobutylene is purified after a sulphuric acid separation process by passing over a treated 5 sieve at 60 DEG F.-130 DEG F. at a rate of 0.5-10 w./hr./w. The sieve may be in tablet or pellet form but preferably a clay binder is not used.