Catalytic oxidation of styrene and its reaction mechanism consideration over bimetal modified phosphotungstates

Cobalt and nickel modified phospotungstates (CoNiPW) were fabricated via the reaction of H3PW12O40•6•5H2O (PW) with Co(NO3)2•6H2O and NiCl•6H2O, followed by calcination; and then characterized by various physicochemical techniques, such as XRD, FT-IR, UV–vis, SEM, TEM and XPS to determine the surface morphology, structure and composition. The as-prepared CoNiPW was used as a catalyst for solvent-free oxidation of styrene with molecular oxygen oxidant. It exhibited efficient in achieving higher conversion of styrene and high selectivity to benzaldehyde. A detail study on influence of key reaction parameters, as well as catalytic role of various constituents in CoNiPW on the reactivity and selectivity was conducted to identify active sites. The reaction mechanism via benzyl alcohol intermediate was proposed by in situ adsorption of styrene on the catalyst surface and the product intermediate produced in the oxidation reaction. The recovery and reusability of the catalyst was also evaluated.