Direct flow synthesis of H2O2 catalysed by palladium supported on sulfonated polystyrene resins

Hydrogen peroxide (H2O2) has a wide application range in industry. It is a strong oxidant used e.g. for bleaching, water treatment, semiconductor wafer cleaning and propylene oxide synthesis. It is produced on large scale by the anthraquinone process to yield highly concentrated (50–70 wt%) product in a routine fashion. Nevertheless, this process is very energy consuming, generates a lot of waste and requires transport of hazardous quantities of H2O2. Therefore, direct H2O2 synthesis (starting from gaseous H2 and O2) has recently emerged as a viable alternative.1 Flow chemistry using microreactor technology has made its entry into this field, offering opportunities for safer and efficient process operation.2
Metal catalysts supported on strongly acidic macroreticular polystyrene resins have also been successfully applied for this transformation.3 In this work, we describe a transfer of this type of catalysis into flow technology. The preparation and characterization of a number of catalysts are described, followed by a presentation of their catalytic performances in the direct H2O2 synthesis. We have been able to obtain more than 2 wt% of H2O2 with selectivities exceeding 30-40% in the best cases. These results are superior to most current literature results regarding direct H2O2 synthesis in flow.