利用正十二烷研究催化裂化中的氢转移指数

以正十二烷为模型化合物，以Y型分子筛为催化剂，考察分子筛硅铝比、La含量和P含量对氢转移反应性能的影响，研究催化裂化反应机理及氢转移反应性能。结果表明，分子筛硅铝比的变化引起了分子筛表面酸量、酸密度和酸强度的变化，因而硅铝比的增加会降低分子筛的氢转移能力；随着La含量的增加，分子筛表面的酸量和酸密度也随之增加，有利于氢转移反应的进行；酸量和酸密度也随P含量的变化而变化，弱酸位的增加和强酸位的减少会减弱裂化反应，提高氢转移反应的选择性。质子化裂化机理可以更好地解释烷烃催化裂化反应的引发步骤，将氢转移指数定义为液相产物中烷烃与烯烃的摩尔比，可以很好地表征催化剂的氢转移活性。

STUDY ON HYDROGEN TRANSFER INDEX WITH DODECANE CATALYTIC CRACKING

The catalytic cracking is a chain reaction involving three steps: initiation, propagation and termination. The main reaction mechanisms are the classical cracking mechanism and protolytic cracking mechanism. The latter one can better explain the initiation step in the catalytic cracking of paraffin. The catalytic cracking of dodecane by Y zeolite was used as model reaction to investigate the mechanism of catalytic cracking and hydrogen transfer reaction in this paper. Hydrogen transfer index（HTI，defined as a ratio of the paraffin content over the olefin content in liquid products）is used to investigate the influence of Si/Al ratio, the La content and the P content on the hydrogen transfer performance. The results indicate that HTI is a convenient way to characterize the hydrogen transfer performance of the zeolites in FCC reactions, and the results were also compared with other methods.