Abstract: To reduce the yield of hydrogen, methane and coke in the secondary reaction of light hydrocarbon in FCC process for more low carbon olefins，the effect of reaction temperature and catalyst bed density on the catalytic cracking of light hydrocarbon and 2-methyl-2-butene on coked regenerated FCC catalyst was investigated in a small fixed-fluidized bed reactor. A series of coked catalysts with different carbon deposition was made by reaction of regenerated catalyst with heavy cycle oil (HCO) or atmospheric residue and used for catalytic cracking of light hydrocarbon test. The experiment results show that the yield of propylene rises with increasing reaction temperature and catalyst bed density, but the yield of hydrogen and methane increases rapidly at high temperature. The increase of catalyst bed density causes rapid growth of coke yield. Compared with the results on the regenerated catalyst, the total yields of hydrogen, methane and coke on the coked catalyst significantly decrease and yield of propylene is almost unchanged. Even if the coked catalyst is recycled many times, the cracking activity for light hydrocarbon still remains stable. The performance of the coked catalyst obtained with HCO is better than the coked catalyst obtained with residue oil.

Key words: catalytic cracking, light hydrocarbon, coke, hydrogen, methane, coked catalyst