Selective Catalytic Oxidation Of Cyclohexanol And Benzyl Alcohol By Tungsten Trioxide

Cyclohexanone and benzaldehyde are important organic industrial raw materials. Cyclohexanone is the chemical intermediates for producing caprolactam and nylon-66; benzaldehyde is one of the most simple and most useful aromatic aldehydes. Benzaldehyde was widely used in the chemical industry, medicine, perfumes, pesticides, dyes and other industries. But the synthetic methods reported in literatures had many shortcomings, such as complex operation, high costs; many toxic and hazardous substances used in the production process, toxic substances-chlorine existed in benzaldehyde products, so these methods are inconsistent with green chemistry development requirements. Therefore, it is still one significative and chanllenging difficulties to explore effective and green synthetic methods of cyclohexanone and benzaldehyde. In this paper, synthetic methods of cyclohexanone and benzaldehyde were studied; meanwhile, the high-efficiency and green synthesis path was discussed.In this paper, the reactions of selective catalytic oxidation of cyclohexanol and benzyl alcohol to cyclohexanone and benzaldehyde were studied, H₂O₂ (mass fraction 30%) as oxidant, WO₃ and WO₃/TiO₂ as catalysts. The influencing factors in the reactions were investigated; the feasible synthesis conditions were obtained. The results under the feasible conditions of the experiments were as follows:(1) With WO₃ as catalyst and H₂O₂ (mass fraction 30%) as oxidant, the reaction of selective catalytic oxidation of cyclohexanol to cyclohexanone was studied. When the amount of WO₃ 1mmol, the amount of methanol 12.4mmol (5mL), the molar ration of WO₃ and cyclohexanol and H₂O₂ 1:100:147, refluxing temperature 80oC and reaction time 2.5h, the yield of cyclohexanone was up to 88.6%. By filtrating and separating, WO₃ catalyst could be reused for six times and catalytic effect changed little. Under the feasible conditions, the small scale tests and repeated testing were investigated, and the yield of cyclohexanone changed little.(2) In the experiments of catalytic oxidation of cyclohexanol to cyclohexanone, with WO₃/TiO₂ as catalyst. When the amount of WO₃/TiO₂ catalyst 0.9276g (equal to 0.8mmol WO₃), the amount of methanol 12.4mmol (5mL), the molar ration of WO₃ and cyclohexanol and H₂O₂ 2:250:375, refluxing temperature 80oC and reaction time 2h, the yield of cyclohexanone was up to 94.5%. WO₃/TiO₂ catalyst was better than WO₃ catalyst, and improved the yield of cyclohexanone and shortened the reaction time. By filtrating and separating, WO₃/TiO₂ catalyst could be reused for six times and catalytic effect changed little. Under the feasible conditions, the small scale tests and repeated testing were investigated, and the yield of cyclohexanone changed little.(3) With WO₃ as catalyst, H₂O₂ (mass fraction 30%) as oxidant, the reaction of selective catalytic oxidation of benzyl alcohol to benzaldehyde was also studied. When the amount of WO₃ 1mmol, the amount of methanol 24.8mmol (10mL), the molar ration of WO₃ and benzyl alcohol and H₂O₂ 1:100:147, refluxing temperature 60oC and reaction time 2h, the yield of benzaldehyde was up to 95.8%. By filtrating and separating, WO₃ catalyst could be reused for six times and catalytic effect changed little. Under the feasible conditions, the small scale tests and repeated testing were investigated, and the yield of benzaldehyde changed little.Compared with existed methods, the experimental methods were simple; reaction conditions were mild, clean, economical, and consistent with the requirements of green chemistry. A new approach for the clean synthesis of cyclohexanone and chlorine-free benzaldehyde were provided.