FLUID CATALYTIC CRACKING (FCC) PROCESS FOR MANUFACTURING PROPYLENE AND ETHYLENE IN INCREASED YIELD

摘要

A fluid catalytic cracking (FCC) process for manufacturing propylene and ethylene in increased yield. The process comprises cracking an olefinic naphtha stream and main hydrocarbon stock in combination with an olefinic C₄ hydrocarbon stream in different zones of one or more risers of an FCC unit. Each FCC riser comprises an acceleration zone at the lower portion thereof, a lift stream feed nozzle at the bottom of the acceleration zone, a main hydrocarbon stock feed nozzle above the acceleration zone and an olefinic naphtha feed nozzle at a location along the acceleration zone between the lift stream feed nozzle and main hydrocarbon stock feed nozzle. The cracking is carried out on a mixed FCC catalyst comprising at least 2 percent by weight pentasil zeolite and at least 10 percent by weight Y-zeolite. The catalyst is injected at the bottom of each FCC riser, the olefinic naptha is injected through the olefinic feed nozzle, the main hydrocarbon stock is injected through the main hydrocarbon stock feed nozzle and the lift stream is injected through the lift stream feed nozzle at the bottom of the acceleration zone. The lift stream comprises the olefinic C₄ hydrocarbon stream with or without steam and/or a fuel gas. The olefinic C₄ hydrocarbon steam is cracked in the acceleration zone at 600 to 8000° C. and pressure of 0.8 to 5 kg/cm up 2 (gauge) and weight hourly space velocity (WHSV) of 0.2 to 100 hr up 1 and vapour residence time of 0.2 to 5 seconds.