Pd催化氧化乙二醛制取乙醛酸的理论研究

乙醛酸由于其独特的结构,在生产和生活中都有广泛的用途。本文应用密度泛函理论对CHOCHO与O2在Pd催化剂存在条件下的各个反应通道进行了势能面扫描研究。在M06/6-31G(d,p)水平上优化了各反应通道上各驻点物(反应物、中间体、过渡态、产物)的几何构型,并计算了它们的振动频率和零点能,通过零点能校正计算了各反应通道的活化能。计算结果表明,乙二醛在Pd催化剂存在下与氧气反应存在着生成乙醛酸和甲酸两条反应通道。两条反应通道速控步骤的活化能分别为215.3 kJ/mol和296.1 kJ/mol,生成乙醛酸的反应为主反应通道。与无催化剂相比,生成乙醛酸反应通道的能垒降低了80.1 kJ/mol;而生成甲酸和CO2的反应通道的能垒反而升高了21.9 kJ/mol。这说明Pd催化剂的加入可以有效的抑制甲酸和CO2的生成,提高乙醛酸的选择性。

Theoretical Study on Reaction Path for Preparation of Glyoxylic Acid from Glyoxal by Pd Catalyse-oxidizing Action

Glyoxylic acid with its unique molecular structure,has a lot of use during the productions and the life.Using the density functional theory （DFT）,the reaction mechanism of CHOCHO and Oz to produce CHOCOOH has been studied. At M06/6--31G（d,p）level, the geometries of all species（reactants,intermediates,transition states and products）of reaction paths were optimized and the vibration frequencies as well as zero point vibration energies（ZPVE）were also calculated.The activation energies of the reactions were calculated with the results of ZPVE.The calculation results suggest that CHOCHO with 02 has been investigated with catalysts or not,which is found that there are two reaction paths which bring glyoxylic acid and methanoic acid.It is found that the rate--determining step activation energy of the two paths is at 215.3kJ/mol and 296,1 kJ/mol,respectlvely,and the path to glyoxylic acid reaction is the main channel.