ABSTRACT
In the economy of a modern refinery, fluid catalytic cracking unit (FCCU) plays a significant role, as it adds value to the refinery products. In this unit more attention is usually given to the behavior of gasoline formation, but it is also important to study the manner of the middle distillates (kerosene and diesel) formation during the cracking process. In the present study, catalytic cracking of heavy gas oil on FCC type catalysts (zeolite Y, blend of zeolite Y (75%) and ZSM-5 zeolite (25%) and commercial zeolite Y)was carried out in a bench scale mini-fluidized bed reactor. The activities of the two prepared catalysts from kaolin were compared with commercial zeolite Y used by Kaduna Refinery and Petrochemical Company (KRPC).The feed in this study was heavy gas oil (also obtained from KRPC); the cracking process was carried out at reaction temperature of 500-590?C and reaction time of 30-180 seconds. The yields of kerosene and diesel fractions were observed to decrease with time at 500?C and 530?C but increased with time at 560?C and 590?C for all the catalysts. In terms of catalytic activity amongst the three catalysts, analysis of the products shows that the zeolite blend (i.e. zeolite Y/ZSM-5) was most active with superior product selectivity for the lighter fractions. With the zeolite blend, the yields of kerosene and diesel were found to be lowest at 17.63% and 15.56% respectively. This indicated the effect of ZSM-5 in converting the heavier fractions in the middle distillate range to lighter fractions. Synthesized zeolite Y had 19.8% and 21.27% yield of kerosene and diesel fractions respectively while the commercial zeolite Y gave 32.29% and 19.04% yields of kerosene and diesel fractions respectively.