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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Physisorption and Chemisorption of Hydrocarbons in H-FAU Using QM-Pot(MP2//B3LYP) Calculations
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Physisorption and Chemisorption of Hydrocarbons in H-FAU Using QM-Pot(MP2//B3LYP) Calculations

机译：用QM-Pot（MP2 // B3LYP）计算H-FAU中碳氢化合物的物理吸附和化学吸附

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The DFT parametrized zeolite force field in the QM-Pot program is extended with carbon—carbon, carbon—hydrogen, and alkoxy bond describing parameters. The extended force field has been combined with B3LYP and with MP2 as the high-level quantum mechanical (QM) method to simulate the physisorption and chemisorption of ethene, isobutene, 1-butene, 1-pentene, and 1-octene in H-FAU (Si/Al_F = 95) and for physisorption of 1-pentene, n-pentane, 1-octene, and n-octane in all silica FAU. The new parametrization predicts more stable chemisorption complexes than physisorbed π complexes, but with smaller chemisorption energies which are more reliable as shown by comparison with experimental results and with accurate hybrid MP2:DFT calculations. An embedded cluster size study shows that, due to the importance of the stabilizing van der Waals part in the MM contribution of the cluster, QM-Pot(MP2//B3LYP) calculations yield more reliable physisorption and chemisorption energies of hydrocarbons in zeolites than QM-Pot(B3LYP). The QM-Pot(MP2//B3LYP) results are in good agreement with available experimental data. In H-FAU, the H~+ ··· alkane interaction was found to contribute at most 7 kJ/mol to the total physisorption energy of n-alkanes while the H~+···π interaction contributes 20—25 kJ/mol to the total physisorption energy of alkenes. For n-alkene physisorption in H-FAU, a linear increase of both the physisorption and chemisorption energies of 8.7 kJ/mol per C-atom is found. The protonation energy of n-alkenes in H-FAU was found to be independent of the C-number and amounts to —50 kJ/mol for the formation of secondary alkoxides. The formation of tertiary alkoxides in H-FAU suffers slightly from steric constraints imposed by the zeolite framework.
机译：QM-Pot程序中的DFT参数化沸石力场使用描述参数的碳-碳，碳-氢和烷氧基键扩展。扩展的力场已与B3LYP和MP2结合起来用作高级量子力学（QM）方法，以模拟H-FAU中乙烯，异丁烯，1-丁烯，1-戊烯和1-辛烯的物理吸附和化学吸附（Si / Al_F = 95），并在所有二氧化硅FAU中物理吸附1-戊烯，正戊烷，1-辛烯和正辛烷。新的参数化方法预测的化学吸附复合物比物理吸附的π复合物更稳定，但化学吸附能更小，与实验结果比较并通过精确的MP2：DFT混合计算显示，其更可靠。嵌入式团簇尺寸研究表明，由于稳定​​范德华部分在团簇的MM贡献中的重要性，QM-Pot（MP2 // B3LYP）计算比QM产生更可靠的沸石中碳氢化合物的物理吸附和化学吸附能-锅（B3LYP）。 QM-Pot（MP2 // B3LYP）结果与可用的实验数据非常吻合。在H-FAU中，发现H〜+···烷烃相互作用最多对正构烷烃的总物理吸附能贡献7 kJ / mol，而H〜+···π相互作用则贡献20-25 kJ / mol。烯烃的总物理吸附能。对于H-FAU中正构烯烃的物理吸附，发现每个C原子的8.7 kJ / mol的物理吸附能和化学吸附能均呈线性增加。发现在H-FAU中正构烯烃的质子化能与C数无关，对于仲醇盐的形成，其质子化能为-50 kJ / mol。 H-FAU中叔醇盐的形成受沸石骨架强加的空间约束的影响。

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