烃分子结构对其催化裂解反应性能的影响

采用脉冲微型反应器和小型固定流化床催化裂解装置，研究了直馏石脑油中不同结构烃分子的裂解反应性能，考察了链烷烃与环烷烃的相互作用，以及催化材料对烃分子裂解性能的影响。结果表明：随着烷烃分子支链度的增加，C8烷烃的反应性能降低，丙烯选择性提高；链烷烃和具有烷基侧链的环烷烃是丙烯的主要来源，双环环烷烃对丙烯也有部分贡献，而芳香烃不易生成低碳烯烃；环烷烃的竞争吸附抑制了链烷烃的转化，而链烷烃在催化裂解过程中生成的碳正离子或烯烃提高了环烷烃的反应性能；与Beta分子筛相比，ZRP分子筛具有较狭窄孔道和较多的Brønsted酸中心，有利于正辛烷的质子化裂解，裂解产物中乙烯和丙烯产率高。

Effect of Molecular Structure onHydrocarbon Catalytic Cracking Performance

With using a pulse micro-reactor and a fixed fluidized bed reactor, catalytic cracking reactions of different hydrocarbons from naphtha were investigated. Interaction between alkanes with cycloalkanes, as well as effects of zeolites on the reactivities of different hydrocarbons were studied. Experimental results showed that, with the increase of methyl substituents, the reactivity of octane isomers decreases due to shape-selective catalysis, but propylene selectivity improves. Linear alkanes and cycloalkanes with paraffinic side chain are ideal feedstocks, which can produce more propylene than that of cycloalkanes with double rings and aromatics. Competitive adsorption of cycloalkanes depresses the reactivity of linear alkanes. However, the intermediates, such as carbocation or olefins formed by cracking of alkane, can improve the conversion of cycloalkanes. It was also found that ZRP zeolite can promote protolitic cracking of n-octane due to its narrow pore size and more Brønsted acid sites, and thus can obtain higher ethylene and propylene yield and selectivity than macroporous zeolites.