丙酮羰基^(13)C化学位移表征分子筛限域效应的理论计算  

Theoretical Calculation of Relationship Between Zeolite Confinement Effect and Adsorbed 2-^(13)C-acetone^(13)C Chemical Shift

作　　者：熊文朋 褚月英 王强 徐君 邓风 XIONG Wenpeng;CHU Yueying;WANG Qiang;XU Jun;DENG Feng(National Center for Magnetic Resonance in Wuhan,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院精密测量科学与技术创新研究院,波谱与原子分子物理国家重点实验室,武汉磁共振中心,武汉430071 [2]中国科学院大学,北京100049

出　　处：《高等学校化学学报》2023年第8期113-119,共7页Chemical Journal of Chinese Universities

基　　金：国家能源石油炼制技术研发中心(中国石油化工股份有限公司石油化工科学研究院)开放基金课题、国家自然科学基金(批准号:21991092,221611322028,22172177);国家重点研发计划项目(批准号:2022YFB3504001)资助.

摘　　要：2-^(13)C-丙酮是表征分子筛酸性的重要探针分子,其^(13)C化学位移是分子筛孔道限域效应与酸强度(可以用去质子化能来表征)协同作用的结果.为了揭示影响丙酮羰基^(13)C化学位移的主导因素,采用理论计算方法研究了分布在分子筛外表面、孔口、内表面及不同尺寸孔道内的Brønsted酸位对吸附丙酮羰基^(13)C化学位移的影响,发现丙酮在分子筛体系呈现氢键吸附的形式.计算结果表明,吸附丙酮羰基^(13)C化学位移随分子筛固有酸强度的增加而增加,但是不存在定量的线性关系;在限域较强的孔道内^(13)C化学位移变化非常大,分子筛限域效应越强(丙酮吸附能越大)则羰基^(13)C化学位移越大,并且与吸附能呈线性关系,这说明丙酮羰基^(13)C化学位移可以用来定量描述分子筛孔道限域效应的强弱.The relationship between adsorbed 2-^(13)C-acetone^(13)C chemical shift and zeolite confinement effect and acid strength(deprotonation energy,DPE)has been assessed by the quantum chemical calculation with the aim of decoupling the influence of acid site strength and zeolite confinement on the measured^(13)C chemical shift,both of which are key factors in zeolite catalysis.We found the hydrogen-bond complex exist for acetone adsorption independent of the location of the Brønsted acid sites.The calculational results show that although the^(13)C chemical shift of adsorbed acetone increases with the increase of zeolite intrinsic acid strength(DPE decreasing),but a linear correlation is not present between them.For the Brønsted sites located in the zeolites with different pore sizes,the subtle difference in the DPE values would lead to significant differences in the^(13)C chemical shift,which demonstrated the zeolite pore confinement played a pivotal role in the measured^(13)C chemical shift in zeolite catalysis.The acetone adsorption energy increases with the decreasing of the zeolite pore size,which could reflect the strength of the zeolite pore confinement effect.Furthermore,a linear correlation is obtained for the^(13)C chemical shift of adsorbed acetone versus its adsorption energy,which can be used as a scale for quantitatively measuring the zeolite pore confinement effect.

关 键 词：分子筛 理论计算 限域效应 酸强度 化学位移 

分 类 号：O657.61[理学—分析化学]