HY催化C_4烷基化中异丁烯质子化反应的分子模拟  

Molecular Simulation of Isobutene Protonation in C_4 Alkylation Catalyzed by HY

作　　者：鲁玉莹[1] 李永祥[1] 龙军[1] 任强[1] 付强[1] 周涵[1] 

机构地区：[1]中国石化石油化工科学研究院石油化工催化材料与反应工程国家重点实验室,北京100083

出　　处：《石油学报（石油加工）》2014年第5期765-771,共7页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：中国石油化工股份有限公司项目(112012)基金资助

摘　　要：采用MS QMERA中QM和MM(量子力学和分子力学)相结合的方法,选用84THY分子筛簇模型,研究了HY分子筛催化C4烷基化反应中异丁烯质子化反应过程。结果表明,异丁烯首先吸附在分子筛上形成π-络合物,再通过正碳离子的过渡态生成表面烷氧基团;质子化反应的活化能能垒为98.74kJ/mol,比单纯H+进攻异丁烯的能垒高。过渡态时烷基片段的正电荷数最高(0.675e),且过渡态构象对应于势垒的最高点,极易向反应物或产物转化;同时,过渡态时Al—O1和Al—O2的键长大致相等,而在反应物和生成物时的键长差异较大,表明处于过渡态的正碳离子不稳定。A cluster of 84 THY was chosen to study the protonation of isobutene in C4 alkylation on HY by using the QM/MM method in MS QMERA.The results showed that the transformation of theπ-complex into a covalently bonded surface tert-butyl fragment occurred through a transition state of carbenium ion with an activation energy of 98.74kJ/mol,which was much higher than the activation energy of isobutene addition reaction by proton directly.The transition state of carbenium ion located on the highest position of potential energy with a highest positive charge was not stable and could convert to reactant or product easily.Also,this was assisted by the fact that the bond lengths of Al—O1and Al—O2were almost equal in the transition state,but considerably differed from each other in the initial and final structures.

关 键 词：HY沸石 烷基化 质子化 正碳离子 分子模拟 

分 类 号：TE624.4[石油与天然气工程—油气加工工程]