NiTi^(+)催化甲基环己烷脱氢的密度泛函理论研究

Density functional theory study on NiTi^(+)catalytic dehydrogenation of methylcyclohexane

有机液体储氢是极具潜力的氢气存储方式,在原子水平上研究储-释氢催化机理,是寻找高效低廉催化剂的重要途径.采用密度泛函理论(DFT)方法研究了甲基环己烷(MCH)在过渡金属二聚体离子NiTi^(+)催化下逐步脱氢制甲苯的反应机理,考察了反应物、中间体和生成物的能量变化.采用波函数分析方法,观察反应过程中原子电荷变化,并分析了初始化合物的态密度(DOS)等性质.结果表明:NiTi^(+)与甲基环己烷的反应是在混合势能面上进行的放热反应,三个脱氢分子机理相似,反应整体放热为-12.19 kcal·mol^(-1),反应过程出现了中间体甲基环己烯和甲基环己二烯,与实验结果一致.整个反应的速率决定步骤为第三个脱氢反应过程中的IM10→TS10.

Organic liquid hydrogen storage is a promising hydrogen storage method.Studying the catalytic mechanism of hydrogen storage-release at the atomic level is an important way to find efficient and low-cost catalysts.The reaction mechanism of stepwise dehydrogenation of methylcyclohexane(MCH)to toluene under the catalysis of transition metal dimer ion NiTi^(+)was studied by density functional theory(DFT)method,and the energy changes of reactants,intermediates and products were investigated.The wave function analysis method was used to observe the change of atomic charge during the reaction,and the properties such as the density of states(DOS)of the initial compound were analyzed.The results show that the reaction between NiTi^(+)and methylcyclohexane is an exothermic reaction on the mixed potential energy surface.The three dehydrogenation molecular mechanisms are similar.The overall exothermic heat of the reaction is-12.19 kcal·mol^(-1).The intermediates methylcyclohexene and methylcyclohexadiene were obtained,which were consistent with the experimental results.The rate-determining step of the whole reaction is IM10→TS10 during the third dehydrogenation reaction.