Highly Selective Catalysts For Phenol Hydroxylation

Phenol is an important raw materials and intermediate compounds, which has an important role in chemical production and life. Dihydroxybenzenes as a phenol derivative, is an important intermediates in chemistry, agricultural chemistry, pharmaceutical and food industries. The path of dihydroxybenzenes preparation achieves large-scale industrial production, what plays an important role in the related development of chemical database and dihydroxybenzenes derivatives. The common methods of preparation are as follows: chlorinated phenols hydrolysis, oxidation of aniline,1,4-Diisopropylbenzene oxidation, phenol and acetone synthesis, Reppe method, benzene and propylene method. The catalysts are acid, base, precious metals and other expensive catalysts.In this study, the method of preparation of bulk copper oxide catalysts included solutions chemical precipitation, sol-gel method and hydrothermal synthesis. By X-ray diffraction (XRD), physical adsorption (BET), scanning electron microscopy (SEM), temperature programmed reduction (H2-TPR), thermo-gravimetric analysis (TGA) and other detection methods to characterize the prepared catalysts. When the catalyst was copper oxide, the phenol hydroxylation reaction of optimal conditions were as follows:the molar ratio of phenol reactant and hydrogen peroxide was 3:1 at 100℃, added the catalyst mass of 10% phenol mass, the reaction time was 5 hours. Under optimal conditions, the selectivity of catechol could reach more than 69%, and the conversion rate of phenol could reach more than 22.9%. Properties of the catalyst for phenol hydroxylation reaction under optimal reaction conditions were discussed.Supported catalysts are obtained by impregnation. By X-ray diffraction (XRD), physical adsorption (BET), scanning electron microscopy (SEM), temperature programmed reduction (H2-TPR), thermo-gravimetric analysis (TGA) and other detection methods to characterize the prepared catalysts, which plays a supporting explanation to catalytic properties. When the catalyst was supported copper oxide, the optimal conditions were as follows:the molar ratio of phenol reactant and hydrogen peroxide was 3:1 at 80℃, added the catalyst mass of 5% phenol mass, the reaction time was 3 hours. Experiments for catalytic activity show that supported catalysts have better catalytic activity than the bulk copper oxide catalyst for phenol hydroxylation reaction. Among different supporters load copper oxide catalysts, the catalytic performance of CuO/Al2O3 and CuO/TiO2 are best. Under optimal conditions, the selectivity of catechol could reach more than 74%, and the conversion rate of phenol could reach more than 25%. Properties of the supported catalysts for phenol hydroxylation reaction under optimal reaction conditions were discussed.