Pd/α-Al_2O_3催化乙炔选择性加氢微观反应动力学

采用乙炔顺序加氢的反应机理,利用已报道的密度泛函理论(DFT)计算结果进行了乙炔加氢反应的微观反应动力学模拟,所得的乙炔加氢反应动力学具有共同的特征。利用实验获得的Pd/α-Al_2O_3催化乙炔加氢反应动力学数据,对上述DFT数据进行校验,发现经过不超过0.1eV的调整,微观反应动力学模拟结果与实验结果符合很好,说明DFT数据是良好的微观反应动力学参数来源。利用优化后的动力学参数模拟了工业生产范围内的动力学,获得了速率控制步骤和表面物种等信息,可为双曲动力学模型的建立提供参考。

Influence of surface strain on activity and selectivity of Pd-based catalysts for the hydrogenation of acetylene: A DFT study

The effects of surface strain and subsurface promoters, which are both important factors in heterogeneous catalysis, on catalytic selectivity and activity of Pd are examined in this study by considering the selective hydrogenation of acetylene as an example. Combined density functional theory calculations and microkinetic modeling reveal that the selectivity and activity of the Pd catalyst for acetylene hydrogenation can both be substantially influenced by the effects of Pd lattice strain variation and subsurface carbon species formation on the adsorption properties of the reactants and products. It is found that the adsorption energies of the reactants and products are, in general, linearly scaled with the lattice strain for both pristine and subsurface carbon atom-modified Pd（111） surfaces, except for the adsorption of C_2H_2 over Pd（111）-C. The activity for ethylene formation typically corresponds to the region of strong reactants adsorption in the volcano curve; such an effect of lattice strain and the presence of subsurface promoters can improve the activity of the catalyst through the weakening of the adsorption of reactants. The activity and selectivity for Pd（111）-C are always higher than those for the pristine Pd（111） surfaces with respect to ethylene formation. Based on the results obtained, Pd-based catalysts with shrinking lattice constants are suggested as good candidates for the selective hydrogenation of acetylene. A similar approach can be used to facilitate the future design of novel heterogeneous catalysts.

The Co-seismic Response of Underground Fluid in Yunnan to the Nepal MS8.1 Earthquake

In this paper,statistics are taken on the co-seismic response of underground fluid in Yunnan to the Nepal M_S8. 1 earthquake,and the co-seismic response characteristics of the water level and water temperature are analyzed and summarized with the digital data. The results show that the Nepal M_S8. 1 earthquake had greater impact on the Yunnan region,and the macro and micro dynamics of fluids showed significant co-seismic response. The earthquake recording capacity of water level and temperature measurement is significantly higher than that of water radon and water quality to this large earthquake; the maximum amplitude and duration of co-seismic response of water level and water temperature vary greatly in different wells. The changing forms are dominated by fluctuation and step rise in water level,and a rising or falling restoration in water temperature. From the records of the main shock and the maximum strong aftershock,we can see that the greater magnitude of earthquake,the higher ratio of the occurrence of co-seismic response,and in the same well,the larger the response amplitude,as well as the longer the duration. The amplitude and duration of co-seismic response recorded by different instruments in a same well are different. Water temperature co-seismic response almost occurred in wells with water level response,indicating that the well water level and water temperature are closely related in co-seismic response,and the well water temperature seismic response was caused mainly by well water level seismic response.