Fluid catalytic cracking (FCC) produces not only transportation fuel but also valuable petrochemicals,like propylene.Another valuable stream from the FCC process is the C4 mixture gas.Normally,part of this stream,especially isobutylene,is converted to MTBE and blended with gasoline to boost octane number and the rest of the stream is hydrogenated and sold as fuel.The CA mixture from the FCC plant contains much valuable olefins like butene-1.Cost-effective separation of these olefms will increase the profitability of the FCC unit.