Amorphous Vanadium Oxide Supported on Activated Carbon Prepared by Dielectric Barrier Discharge as an Efficient and Stable Catalyst for Hydroxylation of Benzene to Phenol

Effective and selective catalytic oxidation of benzene under moderate conditions remains a significant challenge. The surface properties of amorphous metal oxides differ significantly from those of crystalline oxides due to the presence of numerous unsaturated bonds and defects, resulting in variations in adsorption and catalytic activity. Here, a stable amorphous VO_x/AC-H-DBD catalyst was synthesized using a green method in which the mixture of NH₄VO₃-H₂O₂ composites and activated carbon (AC) was treated by dielectric barrier discharge (DBD) at room temperature and under an O₂ atmosphere. DBD treatment decomposes the NH₄VO₃-H₂O₂ composites and causes partial reduction of V⁵⁺ to V⁴⁺ on the catalyst surface, leading to an increase in catalytic activity. Moreover, many oxygen-containing groups are introduced onto the surface of AC through this process, which enhance the dispersion of vanadium oxides on the support. The pretreatment of H₂O₂ increased the V and O content on the catalyst surface and enhanced the interaction between vanadium oxides and supports, thus improving the catalytic activity. Under the optimized reaction conditions, VO_x/AC-H-DBD showed a good and stable catalytic performance where a benzene conversion of 23.1% and a selective transformation of benzene to phenol of 94.8% was achieved. Our research may provide an environmentally benign method for producing amorphous catalysts with great stability and catalytic performance.