Pt (111)面和Pt14团簇上肉桂醛吸附及选择性加氢机理研究

利用密度泛函理论研究了Pt（111）面及Pt₁₄团簇对肉桂醛（CAL）的吸附作用和不完全加氢的反应机理。分析吸附能结果表明，肉桂醛分子以C=O与C=C键协同吸附在Pt（111）面上的六角密积（Hcp）位最稳定，以C=C键吸附在Pt₁₄团簇上最稳定，且在Pt₁₄团簇上的吸附作用较Pt（111）面更强。由过渡态搜索并计算得到的反应能垒及反应热可知，肉桂醛在Pt（111）面和Pt₁₄团簇上均较容易对C=O键加氢得到肉桂醇（COL）。其中，优先加氢O原子为最佳反应路径，即Pt无论是平板还是团簇对肉桂醛加氢均有较好的选择性。同时发现，肉桂醛分子在Pt（111）面的加氢反应能垒较Pt₁₄团簇上更低，即Pt的催化活性及对肉桂醛加氢产物选择性与其结构密切相关，其中，Pt（111）面对生成肉桂醇更加有利。

Adsorption and selective hydrogenation mechanism of cinnamaldehyde on Pt(111) surface and Pt14 cluster

The adsorption and the mechanism for selective hydrogenation of cinnamaldehyde (CAL) on Pt (111) surface and Pt₁₄ cluster were investigated by using density functional theory (DFT). The results illustrate that the synergistic adsorption of CAL molecule on Pt (111) surface with C=O and C=C bonds is most stable at the Hcp position, whereas most stable adsorption of CAL appears on the Pt₁₄ cluster with C=C bond; the adsorption of CAL on the Pt₁₄ cluster is stronger than that on Pt(111) surface. The reaction barriers for each elementary reaction were determined from the transition state search and the results suggest that CAL was preferentially hydrogenated at C=O on the Pt(111) surface and Pt₁₄ cluster, forming cinnamyl alcohol (COL); the hydrogenation of O atom takes the priority. Both Pt plate and cluster have good selectivity for hydrogenation of CAL to COL. The reaction barrier of CAL hydrogenation on Pt(111) surface is lower than that on Pt₁₄ cluster, indicating that the catalytic activity and selectivity of CAL hydrogenation are closely related to the structure of Pt catalysts; Pt(111) surface is more favorable for catalyzing the hydrogenation of CAL to COL.