Highly Selective Oxidation of Styrene to Benzoic Acid with H_ 2O_ 2 as an Oxidant

The oxidation of styrene to benzoic acid was described. 30% aqueous hydrogen peroxide(H_ 2O_ 2) was used as an oxidant and the reaction was catalyzed by coordination compound system which including the peroxotungstate formed in situ from sodium tungstate dihydrate and oxalic acid without halides and organic solvent. The influences of the reaction conditions including temperature, time, amounts of catalyst and ligand were studied. The results showed that when styrene was 100.0 mmol, the optimum molar ratio of sodium tungstate dihydrate, oxalic acid, styrene and 30% H_ 2O_ 2 was 2.0 ∶ 3.2 ∶100.0 ∶440.0. The reaction mixture was stirred at 92 ℃ for 24 h, giving benzoic acid in yield of 98.6%. At the same time the products of the oxidation of styrene were characterized by GC-MS(EI, CI source) and GC-IR.According to the analysis of the products, benzoic acid may form via phenol-1,2-ethanediol and α-hydroxyacetophenone intermediate.