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本文研究了2-丙醇和1,1,1-三氟-2-丙醇在Ni(100)表面解离的可能微观反应机理,使用完全线性同步和二次同步变换(complete LST/QST)方法确定解离反应的过渡态.采用基于第一性原理的密度泛函理论与周期平板模型相结合的方法,优化了2-丙醇和1,1,1-三氟-2-丙醇裂解反应过程各物种在Ni(100)表面的top,hollow和bridge位的吸附模型,计算了能量,并对布局电荷进行了分析,得到了各物种的有利吸附位.结果表明:2-丙醇和1,1,1-三氟-2-丙醇在Ni(100)表面都存在β-H和γ-H两个平行竞争的解离过程,其中2-丙醇在Ni(100)表面β-H解离的速控步骤活化能为64.7 k J·mol-1猯,而γ-H解离速控步骤活化能为233.1 k J·mol-1猯,故β-H解离过程占优势,主要产物是CH3COCH3;相反,1,1,1-三氟-2-丙醇在Ni(100)表面β-H解离的速控步骤活化能为257.1 k J·mol-1猯,而γ-H解离速控步骤活化能为148.1 k J·mol-1猯,故γ-H解离过程占优势,主要产物是CF3CH=CH2.由此说明,电负性更大的氟原子取代2-丙醇中的氢原子之后,2-丙醇在Ni表面的解离机理发生了改变.理论预测结果与实验结论一致.
In this paper, the possible microscopic reaction mechanism of the dissociation of 2-propanol and 1,1,1-trifluoro-2-propanol on the Ni (100) surface was investigated. The complete LST / QST method The transition state of the dissociation reaction was determined.Using the first-principles-based density functional theory combined with the periodic plate model, the pyrolysis reaction of 2-propanol and 1,1,1-trifluoro-2-propanol was optimized The adsorption energies of each species on the top, hollow and bridge of Ni (100) surface were calculated, and the distribution charge was analyzed, and the favorable adsorption sites of each species were obtained.The results showed that 2-propanol and 1,1 , 1-trifluoro-2-propanol on the surface of Ni (100), there exist two parallel competitive dissociation processes of β-H and γ-H, in which β-H dissociation The activation energy of the fast-controlled step is 64.7 kJ · mol-1 猯, while the activation energy of γ-H dissociation step-controlled step is 233.1 kJ · mol-1 猯, so the β-H dissociation process is dominant. The main products are CH3COCH3. In contrast, the activation energy of 1,1,1-trifluoro-2-propanol in the step-controlled step of dissociation of β-H on Ni (100) surface was 257.1 kJ · mol- The activation energy of the step-controlled step is 148.1 kJ · mol-1 猯, so γ-H dissociation process predominates, the main The product is CF3CH = CH2 .This shows that the more negative electronegative fluorine atoms in 2-propanol hydrogen atoms, 2-propanol dissociation mechanism in the Ni surface has changed.Prediction results and experimental conclusions Consistent.