HMFI分子筛酸中心性质解析理论研究  

Theoretical Study on the Property Analysis of Br?nsted Acid Sites Over HMFI Zeolite

作　　者：郑健 秦玉才[2] 宋丽娟[1,2] ZHENG Jian;QIN Yu-cai;SONG Li-juan(College of Chemistry&Chemical Engineering,China University of Petroleum(East China),Qingdao Shandong 266555,China;Liaoning Province Key Laboratory of Petrochemical Catalytic Science and Technology,Liaoning Shihua University,Fushun Liaoning 113001,China)

机构地区：[1]中国石油大学(华东)化学工程学院,山东青岛266555 [2]辽宁省石油化工催化科学与技术重点实验室,辽宁石油化工大学,辽宁抚顺113001

出　　处：《当代化工》2022年第3期529-533,共5页Contemporary Chemical Industry

基　　金：国家自然科学基金资助项目(项目编号:21902068,U20A20120,U1908203)。

摘　　要：分子筛B酸中心酸性质是影响其性能的关键因素。选取有代表性硅铝比(Si/Al=13,即SiO_(2)/Al_(2)O_(3)=26)的HMFI周期性模型为研究对象,采用周期性密度泛函理论的方法考察了HMFI分子筛Brφnsted酸(简称B酸)位的结构特性、电子性质和酸强度。结果表明:HMFI分子筛十元环孔道中的B酸位具有相似的结构性质和电子性质,位于六元环中的B酸位会受到周围骨架O原子的作用,O—H键长增加,H和O原子正负电荷降低。轨道性质分析发现,分子筛中与Al原子相近的骨架O原子最容易贡献电子,B酸位质子H最容易接受电子。去质子化能结果表明,分子筛中的B酸位具有相似的酸强度,证明不同活性位赋予HMFI分子筛普遍存在的各种反应性主要依赖活性位周围的化学环境。本研究从量子化学层面揭示了HMFI分子筛B酸位的本征特性,为深入认识HMFI分子筛中B酸的性质提供理论支持。The properties of Brφnsted acid sites(BAS) in zeolite are the key factors affecting catalytic performance.The HMFI periodic model with representative Si/Al ratio(Si/Al=13, SiO_(2)/Al_(2)O_(3) = 26) was selected as the research object. The structural properties, electronic properties and acid strength of BAS in HMFI zeolite were studied by using a periodic density functional theory(DFT). It was found that the BAS in the ten-membered-ring channel of HMFI model had similar structural and electronic properties. The BAS in the six-membered-ring was affected by the surrounding framework oxygen atom, the O—H bond length increased, and the positive and negative charges of H and O decreased. The analysis of orbital properties showed that the framework oxygen atoms close to Al atom was the most likely to contribute electrons, and the protons of BAS was the most likely to accept electrons. The results of deprotonation energies showed that the BAS in the zeolite had similar acid strength, which proved that the universal reactivity given by various active sites to HMFI zeolite mainly depended on the chemical environment around the BAS. This study reveals the intrinsic characteristics of BAS in HMFI zeolite, which provides theoretical support for further understanding the properties of BAS in HMFI zeolite.

关 键 词：HMFI分子筛 密度泛函理论 结构特性 电子性质 

分 类 号：TQ032[化学工程]