Oxidation of hydroquinones to benzoquinones with hydrogen peroxide using catalytic amount of silver oxide under batch and continuous-flow conditions

Silver oxide (Ag2O) can be utilized as heterogeneous catalyst in the oxidation of hydroquinones to the corresponding benzoquinones with 30% aq. H2O2. The catalytic properties of Ag2O have been explored in the model reaction of methylhydroquinone with H2O2 performed under batch conditions. Results show that the reaction can be carried out in high yield and selectivity at room temperature under environmentally friendly conditions. The truly heterogeneous catalyst can be recovered by filtration and reused for at least five times, giving the same excellent results (similar to 95% yield, similar to 98% selectivity). The catalyst can be packed in a tubular reactor and utilized under continuous-flow conditions giving similar good results. (C) 2010 Elsevier Inc. All rights reserved.