Cu(111)面上糠醇加氢生成2-甲基呋喃的反应机理

采用广义梯度近似的密度泛函理论并结合平板模型的方法,详细研究了糠醇在Cu(111)面上反应生成2-甲基呋喃的反应历程,优化了糠醇在Cu(111)面的吸附模型,并采用完全线性同步和二次同步变换的方法,对三种可能的反应机理中的各反应步骤进行了过渡态搜索.结果表明,糠醇主要通过支链上OH与Cu(111)面相互作用,易形成ψCH2和ψCH2O中间体(ψ代表呋喃环).糠醇进一步加氢机理很可能为:引入的氢物种明显降低了糠醇分解形成的中间体ψCH2的活化能,并促进了它的形成;中间体ψCH2更易从糠醇中获得H而生成2-甲基呋喃.该过程的控速步骤为ψCH2O*→ψCHO*+H*,活化能为199.0kJ/mol,总反应是2ψCH2OH=ψCH3+ψCHO+H2O.

Reaction Mechanism for 2-Methylfuran Formation during Hydrogenation of Furfuryl Alcohol Catalyzed by Cu(111) Plane

The reaction mechanism for 2-methylfuran formation during hydrogenation of furfuryl alcohol on Cu(111) plane was investigated by the density functional theory generalized gradient approximation calculations with the slab model.The adsorption energy of furfuryl alcohol was calculated to obtain preferred adsorption sites on Cu(111) plane.Three possible reaction mechanisms were characterized and the reaction potential energy surfaces were computed.The transition states(TSs) were searched with the linear and quadratic synchronous transit(LST/QST) complete search.The results show that the furfuryl alcohol molecule adsorbed on the Cu(111) plane via-OH,and the intermediate ψCH2 and ψCH2O can be obtained by the furfuryl alcohol decomposition.The mechanism for 2-methylfuran formation according to the mechanism C is more probable.The energy barrier of furfuryl alcohol decomposition to form ψCH2 can be significantly reduced by the participation of hydrogen radical.The intermediate of ψCH2 is much easier to obtain the H atom from the furfuryl alcohol,that is the formation routine of the product 2-methylfuran.In the mechanism C,the calculated barrier for the rate-determining step ψCH2O* → ψCHO* + H* is 199.0 kJ/mol.The general reaction is 2ψCH2OH = ψCH3 + ψCHO + H2O.