HY分子筛催化异丁烷/丁烯烷基化反应中加成反应的模拟研究  

Multi-Scale Computational Study on the Addition Reaction of Butene Alkylation With Isobutane Over HY Zeolite

作　　者：任奎 龙军[1] 任强[1] 李永祥[1] 代振宇 

机构地区：[1]中国石化石油化工科学研究院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）》2018年第1期24-33,共10页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：北京市科技计划项目(Z151100002815026);中国石油化工股份有限公司项目(115114)资助

摘　　要：建立了120T HY分子筛模型,采用量子力学与分子力学(QM/MM)相结合的方法,揭示了叔丁基烷氧基团(TBA)与异丁烯/2-丁烯发生加成反应的细节,并比较了二者的异同。结果表明,叔丁基碳正离子是加成反应的过渡态,且TBA与2-丁烯分子发生加成反应的能垒值是与异丁烯反应的2倍左右。这是由于过渡态的碳正离子与异丁烯之间的电荷转移明显大于与2-丁烯的,二者之间的相互作用力更强,故过渡态能量更低。另外,由于TBA与2-丁烯发生加成反应后中心C原子稳定性降低,故需要首先生成"三角形结构"中间产物,再形成C8碳正离子,最终形成C8烷氧基团完成加成反应。The mechanism of addition reaction between t-butyl alkoxide(TBA)and isobutene/2-butene was calculated using an embedded QM/MM(quantum mechanics/molecular mechanics)method on the 120 T HY zeolite model.It is confirmed that carbonium ion is the transition state of the two reactions,and the reaction barrier of addition reaction between TBA and 2-butene(29.0 kJ/mol)is2 times than that of isobutene(14.9 kJ/mol).It is because the electron transfer from isobutene to t-butyle carbonium is much easier than that from 2-butene.Moreover,with respect to 2-butene,to form C8 carbonium ion,the extra generation of triangle-structured intermediate and its corresponding rotation are needed,but their reaction heat is ultra low,thus the formation of triangle-structured intermediate is hard to occurr.Especially,the central C atom of C8+is in the form of secondary carbonium, which is less stable than t-butyle carbonium,owing to the endothermic pathway.Consequently, TBA preferentially reacts with isobutene,rather than2-butene.

关 键 词：HY分子筛 烷基化 分子模拟 量子力学与分子力学(QM/MM) 加成反应 

分 类 号：TE624.4[石油与天然气工程—油气加工工程]