尖晶石纳米催化剂应用于烯丙醇多相氧化制烯丙醛或烯丙酮

Nanoparticle Spinel Catalysts for Heterogeneous Oxidation from Allylic Alcohols to Corresponding Aldehydes and Ketones

使用共沉淀法通过Ru对MnFe2O4的同晶取代制备了纳米级MnFe1.95Ru0.05O4催化剂。在通过过渡金属进一步改性该催化剂的过程中,发现MnFe1.8Cu0.15Ru0.05O4的催化剂性能优异于文献报道的其他多相醇氧化催化剂, XRD测试表明该催化剂仍保持尖晶石结构。该纳米催化剂能有效地将不同烯丙醇类氧化成烯丙醛类或烯丙酮类, 与文献报道的其他多相醇氧化催化体系相比,该催化剂具有更高的活性转换数。借助于EXAFS等表征结果和1-辛醇与4-辛醇的竞争反应,判断出单核的Ru为反应的活性中心,EXAFS的表征同时表明由于Cu的添加而产生的Ru=O能加快反应速度。作者在此基础上提出反应机理,认为Ru在反应过程中形成醇化物,再经过b 消除反应生成相应的醛或酮。

Nanoparticle MnFe1.95Ru0.05O4 catalyst was prepared by isomorphous replacement of Fe in MnFe2O4 with Ru using coprecipitation method. With further modifying the catalyst with transition metals, we found that MnFe1.8Cu0.15Ru0.05O4 showed the best catalytic properties among all reported heterogeneous catalysts for alcohols oxidation, and the results of XRD showed that the catalyst remained the spinel structure unchanged. Nanoparticle MnFe1.8Cu0.15Ru0.05O4 catalyst can effectively oxidize allylic alcohols to allylic aldehydes and allylic ketones. Compared with other heterogeneous catalytic systems of alcohols oxidation, this catalyst can gain higher turnover number (TON). With the aid of Extend X-ray Adsorption Fine Structure (EXAFS) characterization and competitive reaction between 1-octanol and 4-octanol, monomeric ruthenium species were found to be the active sites. Based on the above research, reaction mechanism was proposed that Ru-alcoholate species were formed in reaction, which underwent the b elimination to produce the corresponding aldehydes and ketones.