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

教授。Gorte和White将研究化学吸附分子与高硅沸石（如ZSM-5）中Bronsted酸位点的相互作用。他们将识别反应中间体，确定1:1化学计量络合物形成的能量学及其远程相互作用，并通过分子动力学建立表面化学模型。他们将研究来自工业上重要的反应分子的吸附中间体，如醇、硫醇、醛、酯、酚和取代芳烃，并将确定适合表征远程相互作用的分子探针。光谱表征将通过TPD， TGA，多相固体核磁共振，NQR和IR来完成。对于核磁共振工作，沸石将以大单晶的形式安装在毛细管随机取向。核磁共振波谱将涉及多相脉冲序列、线窄序列、魔角旋转和同位素取代，并采用诸如REDOR和PISMA等技术。特别重要的是添加甲基的氢核磁共振来研究酸位点的环境。具有各种官能团的弱碱性分子的微热测量信息将与光谱学相关联，目的是使表面反应的能垒合理化。这些结果将与从头算量子化学的结构和能量计算，以及探针分子在沸石簇模型中的化学吸附和反应步骤的从头算量子分子动力学相补充。

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.