The application of 2,5-bis(diethylaminoethyl)-hydroquinone in oxidation of benzyl alcohol to benzoic acid with H_2O_2 as an oxidant under organic solvent-free conditions

2,5-Bis(diethylaminoethyl)-hydroquinone was synthesized and used as an co-catalyst during the oxidation of benzyl alcohol to benzoic acid in the presence of 30% aqueous hydrogen peroxide as an oxidant under organic solvent-free and halides-free conditions.The reaction was catalyzed by a coordination compound system including the peroxotungstate formed in situ from sodium tungstate dehydrate and 2,5-bis(diethylaminoethyl)-hydroquinone under organic solvent-free and halide-free conditions.The influence of the reaction conditions including the temperature,reaction time,amounts of catalyst,ligand,sulphuric acid and 30% aqueous hydrogen peroxide was studied.The results showed that when benzyl alcohol dosage was 40.5 mmol,the reaction was conducted at an optimum molar ratio of sodium tungstate dehydrate∶2,5-bis(diethylaminoethyl)-hydroquinone∶benzyl alcohol∶30% H2O2 equating to 0.405∶0.489∶40.5∶273,in the presence of 3 mL of 0.1 mol/L aqueous sulphuric acid at a reaction temperature of 95 ℃ and a reaction time of 8 h,resulting in a primary crystallized benzoic acid yield of 76.9%.The recycling of the catalyst system was studied also.