光催化甲醇氧化脱氢制甲酸甲酯反应研究

Investigation on Photocatalytic Production of Methyl Formate by Oxidative Dehydrogenation of Methanol

以温和条件下的甲醇制甲酸甲酯为研究对象,探究了甲醇光催化氧化脱氢制甲酸甲酯的技术路线及其反应机理。通过光化学还原的方法制备了不同金属负载的TiO2催化剂,并测试了不同催化剂的光催化活性,其中0.5%Pd/TiO2表现出相对较好的活性。通过X射线衍射(XRD)、拉曼光谱(Raman)、高倍透射电镜(HRTEM)和紫外可见漫反射光谱(UV-Vis DRS)等表征,讨论了Pd在TiO2上的分布和对光催化性能的影响。采用原位漫反射红外光谱(in-situ DRIFTS)分析表征了甲醇在氧气气氛下光催化脱氢制甲酸甲酯过程的中间产物,并探究了其反应机理。结果表明:甲酸甲酯的生成路径有两条,一是中间产物甲醛与吸附的甲醇通过交叉偶联反应生成甲酸甲酯,二是甲醛氧化的中间体甲酸盐进一步与甲醇发生酯化反应生成甲酸甲酯。该工作可为光催化甲醇制甲酸甲酯提供基础数据与理论支持。

To realize the production of methyl formate from methanol self-coupling under mild conditions,photocatalytic oxidative dehydrogenation of methanol to methyl formate was investigated,and the mechanism was discussed.TiO2 catalysts loaded with different metals were prepared by photochemical reduction,and the photocatalytic performance of different catalysts was investigated.0.5%Pd/TiO2 presented the best dehydrogenation activity.The distribution of Pd on the surface of TiO2 particles was characterized by X-ray diffraction(XRD),Raman spectroscopy,high resolution transmission electron microscope(HRTEM)and ultraviolet-visible diffuse-reflectance spectrum(UV-Vis DRS),and the effect of the surface morphology on the photocatalytic properties was investigated.To reveal the photocatalytic dehydrogenation mechanism,in-situ diffuse reflectance infrared spectroscopy(in-situ DRIFTS)analysis was conducted to analyze and characterize the intermediate products of photocatalytic dehydrogenation of methanol to methyl formate in oxygen atmosphere.It was found that methyl formate was derived from two pathways.One was the cross-coupling reaction between the intermediate of formaldehyde and the adsorbed methanol to generate methyl formate,and the other was the further esterification of the intermediate formate derived from the oxidation of HCHO with methanol to produce methyl formate.The present work provides theoretical and data support for the photocatalytic production of methyl formate.