烯烃与环烷烃在催化裂化中反应的异同点

Similarities and differences between the catalytic cracking reactions of olefins and cycloalkanes

烯烃和环烷烃是催化裂化原料中常见的两种分子类型,对这两类分子反应特点和反应规律的研究对于深入认识催化裂化反应具有重要意义。采用计算化学工具,详细研究烯烃和环烷烃裂化过程中的热力学和动力学。结果表明,在B酸中心作用下,烯烃主要发生裂化反应;在L酸中心作用下,烯烃容易发生环化反应生成环烷基正碳离子,并进一步发生反应生成环烷烃和环烯烃;环烷烃的裂化反应受到热力学限制,反应发生较为困难;烯烃环化反应和环烷烃裂化反应互为逆反应,在催化裂化过程中烯烃环化反应占据优势。

Olefins and cycloalkanes are two important molecular types in FCC feedstocks, and the study of the reaction characteristics and reaction laws of these two types of molecules have great significance in the further understanding of the FCC reactions. In this paper, the thermodynamics and kinetics of olefins and cycloalkanes cracking were studied by means of computational chemistry. The results showed that olefins were mainly cracked under the action of B acid center ;under the action of L acid center,the olefins were prone to cyclization to form naphthenic carbon ions, and further reacted to form cycloalkanes and cyclic olefins;the cracking reaction of cycloalkane was difficult because it was limited by the thermodynamics; the cyclization reaction of olefins and the cracking reaction of cycloalkanes were reverse reaction each other;in the process of catalytic cracking, the cyclization of olefins was dominant.