Partial oxidation of toluene to benzaldehyde catalyzed by heteropoly compounds immobilized on activated carbon

The commercial production of benzaldehyde through the toluene chlorination and hydrolysis method not only releases chloride-laden effluents into the environment but also excludes its application into the field of food and medicine due to the residual chlorine. To develop a green process that produces chlorine-free product efficiently and cheaply, a keggin-type polyoxometalate designed with Co as a heteroatom, Mo, W and Mn as ligand atoms and La as a counter cation has been loaded on activated carbon to catalyze the production of benzaldehyde from the oxidation of toluene in liquid-phase by oxygen. The optimum catalyst preparation conditions are as follows: polyoxometalate loading 35%(wt), pH 1  = 7.1, pH 2  = 3.8, T 1  = T 2  = 85 °C and activated in N 2 at 220 ℃ for 4 h. Characterization has been done with ICP-OES, FT-IR, XRD and TG. The polyoxometalate synthesized is proved to be Keggin-type structure. The catalyst Na 4.2 LaCoMn 0.3 W 1.5 Mo 10.2 O 40 ·18.53H 2 O@AC manifests the best performance in catalyzing the production of benzaldehyde from the partial oxidation of toluene with a toluene conversion of 18.55%, benzaldehyde selectivity of 33.61% and benzaldehyde yield of 6.23%.