20110163002 | PROCESS FOR ENHANCED PROPYLENE YIELD FROM CRACKED HYDROCARBON FEEDSTOCKS AND REDUCED BENZENE IN RESULTING NAPHTHA FRACTIONS - A process in which a catalytic cracking unit is operated to crack a hydrocarbon feedstock in a manner to enhance light olefin yields. The accompanying benzene-containing naphtha product stream is further processed through a benzene selective membrane to provide a low content benzene stream. Refiners frequently operate their cracking units to optimize light olefin yields, e.g. propylene, in response to needs in the petrochemical industry, and it has been discovered that units operated in this manner frequently produce naphtha containing increased amounts of benzene. The method of this invention therefore allows one to operate the unit when it is desired to optimize light olefin yields, yet at the same time produce a naphtha yield having a low benzene content. The invention is particularly useful when the cracking unit utilizes pentasil zeolites at increased concentrations to enhance light olefins yield. | 07-07-2011 |