Characterization of Local and Non-local Interactions of Stoichiometric Adsorption Complexes in High-Silica Zeolite

教授Gorte和白色将研究化学吸附分子与高硅沸石（如ZSM-5）中布朗斯台德酸位点的相互作用。 他们将确定反应中间体，确定1：1化学计量复合物形成的能量学及其长程相互作用，并通过分子动力学模拟表面化学。 他们将检查来自工业上重要的反应物分子，如醇，硫醇，醛，酯，酚和取代芳烃的吸附中间体，并将确定适合于表征长程相互作用的分子探针。 将使用TPD、TGA、多相固态NMR、NQR和IR进行光谱表征。对于NMR工作，沸石将以毛细管中随机取向安装的大单晶的形式。核磁共振波谱学将涉及多相脉冲序列、谱线窄化序列、魔角旋转和同位素取代，以及REDOR和PISMA等技术。 特别重要的是添加甲基的H NMR以研究酸位点的环境。 具有各种官能团的弱碱性分子的微量量热法的信息将与光谱学相关，目的是合理化表面反应的能垒。 这些结果将与从头计算量子化学计算的结构和能量，从头计算量子分子动力学的化学吸附和反应步骤的分子筛簇模型中的探针分子。

Profs. Gorte and White will investigate the interaction of chemisorbed molecules with Bronsted acid sites in high-silica zeolites, such as ZSM-5. They will identify the reaction intermediates, determine the energetics of formation of 1:1 stoichiometric complexes and their long-range interactions, and model the surface chemistry by molecular dynamics. They will examine adsorbed intermediates derived from industrially significant reactant molecules, such as alcohols, thiols, aldehydes, esters, phenols and substituted aromatics, and will identify molecular probes suitable for the characterization of long-range interactions. The spectroscopic characterization will be done with TPD, TGA, multi-phase solid-state NMR, NQR, and IR. For the NMR work, the zeolite will be in the form of large single crystals mounted with random orientations in capillary tubes. The NMR spectroscopy will involve multiphase-pulse sequences, line-narrowing sequences, magic-angle spinning and isotopic substitution, with techniques such as REDOR and PISMA. Particularly important is the addition of H NMR of methyl groups to investigate the environment of the acid sites. Information from microcalorimetry of weakly basic molecules having various functional groups will be correlated with the spectroscopy, with the objective of rationalizing the energy barriers for surface reactions. Those results will be complemented with ab initio quantum chemistry calculations of structures and energies, and ab initio quantum molecular dynamics of the chemisorption and reaction steps of probe molecules in cluster models of the zeolites.