Catechol and hydroquinone are important industrial raw materials. The methods by which phenol hydroxylates to dihydroxybenzene (catechol and hydroquinone) by one step are high in utilization of reactant atoms, energy-saving and efficient, which are in line with the concept of sustainable development. Using H₂O₂ as oxidant in the oxidation process of phenol to dihydroxybenzene has become a hot spot in the field of catalytic synthesis because it is simple, environmentally-friendly and it can be done under mild reaction conditions. The catalyst plays a decisive role in this reaction system, and the phenol conversion and yield of the product greatly depend on the catalytic activity of catalyst. In this paper, the recent progresses in the catalysts which are used for the hydroxylation of phenol to dihydroxybenzene are reviewed. According to the reaction system, the catalysts are divided into the catalysts used in thermal-driven reaction systems and in photocatalytic reaction systems. The catalytic performances of the catalysts are mainly evaluated by the conversion of phenol, the selectivity of dihydroxybenzene and stability. The research of metal-containing catalysts in heterogeneous reaction systems using H₂O₂ as oxidant is mainly introduced. Finally, the development trends of application of catalysts in the reaction system of one-step hydroxylation of phenol with H₂O₂ are prospected.
Contents
1 Introduction
2 Catalysts used in thermal-driven reaction systems
2.1 Fe-containing catalysts
2.2 Cu-containing catalysts
2.3 Mixed metal oxide catalysts
2.4 Other metal-containing catalysts
2.5 TS-1 molecular sieve catalysts
2.6 Polyoxometalate compounds
3 Catalysts used in photocatalytic reaction systems
4 Conclusion