Cu-fe Base Load Catalyst Hydrogen Peroxide Oxidation Of Benzyl Alcohol To Benzaldehyde Study

Benzaldehyde is an important fine chemical, which is widely used for drugs, perfumery, foodstuff, dyestuff, etc. Toluene chlorination is mainly used for industrial production of benzaldehyde. However, this method has some disadvantages such as low benzaldehyde yield, low quality level, enviromental pollution, etc.In recent years, the market demand of the high quality benzaldehyde increases greatly. Therefore, it is highly desirable to develop an efficient green route for the production of benzyaldehyde. Liquid-phase oxidation of benzyl alcohol by hydrogen peroxide is considered one of the friendly environment routes to get high yield of benzaldehyde. The use of an efficient green catalyst is key factor in this reaction. In addition, it is still challenge to simultaneously achieve high conversion of benzyl alcohol and high selectivity of benzaldehyde. Therefore, research on liquid-phase oxidation of benzyl alcohol by hydrogen peroxide has significant importance in academic exploration and industrial application.In this thesis, the catalytic reactivity, kinetic reaction behavior and properties of supported Cu-based catalysts in liquid-phase oxidation of benzyl alcohol by hydrogen peroxide were investigated, and the function-properties relation of these catalysts was discussed. Effects of supports, Cu-loading and the reaction conditions on the reactivity of the supported Cu-based catalysts were studied in the reaction. Under the condition of 80℃,4 h, 20 mL benzyl alcohol, hydrogen peroxide/benzyl alcohol (H2O2/BzOH) solution=1.5,0.02 g catalyst,6-CuOx/4A (6 wt.%Cu-loading) catalyst has the highest reactivity among these investigated.45.3% conversion of benzyl alcohol and 84.7% selectivity of benzaldhyde were obtained on the 6-CuOx/4A catalyst. On the base of above results, effect of promoters on the reactivity of the catalyst was investigated. Under the condition of 80℃,3 h,20 mL benzyl alcohol, hydrogen peroxide/benzyl alcohol (H2O2/BzOH) solution=2,0.1 g catalyst,58.9% conversion of benzyl alcohol and 90.4% selectivity of benzaldhyde was observed on the 6-CuOx-6-FeOx/4A catalyst.6-CuOx-6-FeOx/4A (6 wt.%Cu-loading and 6 wt.%Fe-loading) catalyst has the higher reactivity than any other catalysts.Furthermore, a comparative kinetics study about liquid-phase oxidation of benzyl alcohol on the 6-CuOx/HZSM-5,6-CuOx/4A and 6-CuOx-6-FeOx/4A catalyst was carried out. The first order and second order rate constant of 6-CuOx/4A catalyst are higher than those of 6-CuOx/HZSM-5, and the activation energy of 6-CuOx/4A (13 KJ/mol) is less than 6-CuOx/HZSM-5 (23.6 KJ/mol). These results indicate that 6-CuOx/4A catalyst has much strong reactivity comparing with 6-CuOx/HZSM-5. The support plays great influences on the reactivity of supported Cu catalysts. On the other hand, the first order and second order rate constant of 6-CuOx-6-FeOx/4A catalyst are greater than 6-CuOx/4A; in addition, the activation energy of 6-CuOx-6-FeOx/4A (9 KJ/mol) is less than 6-CuOx/4A (13 KJ/mol). Hence, 6-CuOx-6-FeOx/4A catalyst has much strong reactivity comparing with 6-CuOx/4A. Promoter Fe modifies the properties of active sites on the catalyst, which in turn affects the reactivity of the catalyst. Liquid-phase oxidation of benzyl alcohol on benzyl alcohol concentration and catalyst dosage was first-order.In addition, the structure and properties of Cu-based catalysts was characterized by N2-isothermy adsorption desorption, powder X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR) technology. The results show that Cu loading not only affects the specific surface area and volume of the catalysts but also the dispersion and structure of Cu oxide species on the catalysts. As Cu-loading increasing, the specific surface area and volume of catalysts decreased; in addition, the dispersion of copper oxide gradually reduced and phase CuO appeared. The reducibility of supported Cu catalyst varied as the Cu-loading. The reducibility of 6-CuOx/4A catalyst was much strong comparing with other supported Cu catalysts. The reducibility of supported Cu catalyst can be improved significantly by added Fe into the catalyst, which was mainly attributed to the interaction between copper oxygen species and iron oxygen species on the catalyst.6-CuOx-6-FeOx/4A catalyst had highest reactivity among the investigated catalysts, due to one of possible reasons that it had highest reducibility.