重油催化裂解过程中丙烯和干气的生成历程

采用固定床微反实验装置考察了大庆蜡油不同转化深度下的催化裂解反应的产物分布，探讨了重油催化裂解过程中丙烯和干气的生成历程。结果表明，重油催化裂解过程中，丙烯的生成是原料一次裂解和汽油馏分二次裂解共同作用的结果。当原料转化深度较低时，丙烯已由原料中烷烃的一次裂解反应大量生成；随着原料转化深度的增加，汽油馏分二次裂解生成丙烯的反应所占比重增大。在原料一次裂解为主生成丙烯的反应阶段内，干气主要由烷烃发生单分子裂化反应生成，而在汽油馏分二次裂解为主生成丙烯反应阶段内，芳烃和烯烃缩合生焦反应对干气生成的影响更为显著。

Formation Mechanism of Propylene and Dry Gas During Deep Catalytic Cracking of Heavy Oil

The product distribution of Daqing VGO deep catalytic cracking at various conversion levels was examined in a fixed-bed micro-activity test unit. Based on analyzing the change of product distribution with conversion, the formation mechanisms of propylene and dry gas during deep catalytic cracking of heavy oil were discussed. The results suggested that propylene was formed both by primary cracking reaction of heavy hydrocarbon feedstocks and by secondary cracking reaction of gasoline fractions. A large quantity of propylene was mainly formed by primary cracking reaction of heavy hydrocarbons at lower conversion, after that propylene formed by secondary cracking reaction of gasoline fractions increased with the increase of conversion. Meanwhile, the formation of dry gas was mainly attributed to the occurrence of monomolecular cracking reaction at the reaction stage dominated by primary cracking reaction of heavy hydrocarbon feedstocks, while the formation of dry gas was affected significantly by condensation reaction of aromatics and olefin to coke at the reaction stage dominated by secondary cracking reaction of gasoline fractions.