Preparation Of H-ZSM-5Supported Iron-based Catalysts And Their Application In Phenol Hydroxylation

Dihydroxybenzene is important organic chemical intermediate. Catechol is mainlyused for pesticides, perfume and pharmaceutical industry. In addition, it can be usedas specialty chemicals like plating bath additives and antioxidants. It is also one of theraw material for the synthesis of phenolic resin. Hydroquinone is widely used for thephotosensitive material, rubber and dye industry. Besides, it also can be used aspolymerization inhibitor during the storage of some resin or rubber monomer, guminhibitor of engine fuel, oil anticoagulant and catalytic desulfurization agent in theNitrogen Fertilizer Industry.The hydroxylation of phenol by hydrogen peroxide is a kind of "green technology"and the most promising process for the manufacture of dihydroxybenzene. In thisarticle, H-ZSM-5supported iron oxide catalyst was prepared by precipitation andhomogeneous precipitation with sodium hydroxide and urea as precipitating agentrespectively. The catalytic properties were tested by the reaction of phenolhydroxylation. The result shows that the catalyst prepared with sodium hydroxide asprecipitating agent has better catalytic properties.In order to improve the conversion of phenol and the selectivity todihydroxybenzene, H-ZSM-5supported binary transition metal oxide catalysts wereprepared with sodium hydroxide as precipitating agent, among which the iron-cobaltbinary oxide catalyst showed the best activity and selectivity. H-ZSM-5supportedcatalysts showed better activity and selectivity than transition metal oxide. UsingH-ZSM-5supported iron-cobalt binary oxide as catalyst, under the conditions thatm(catalyst)/m(phenol)=0.05with water as solvent, reaction temperature60oC，n(Phenol)/n(H2O2)=1.25and reaction time1h, the conversion of phenol was51.82%，the total selectivity of dihydroxbyenzene was92.47%and the effectiveutilization of hydrogen peroxide reached59.90%.The effect of catechol, hydroquinone and acid in the initial reaction system,reaction temperature, molar ratio of phenol to hydrogen peroxide, mass ratio ofcatalyst to phenol and reaction time to the hydroxylation of phenol was investigated.