Effect of reaction conditions on the direct synthesis of hydrogen peroxide with a AuPd/TiO2 catalyst in a flow reactor

The direct synthesis of hydrogen peroxide (H₂O₂) represents a potential alternative to the currently industrially used anthraquinone process, and Au–Pd catalysts have been identified as effective catalysts. To obtain a direct process, a detailed understanding of the reaction conditions in a continuous flow system is needed. In this study, we use a flow reactor to study reaction conditions independently, including total gas flow rate, catalyst mass, reaction pressure, solvent flow rate, and H₂/O₂ molar ratio. The study was carried out without the addition of any halide or acid additives often used to suppress the sequential hydrogenation and decomposition reactions that allowed the kinetics of these reactions to be studied along with the synthesis reaction. A global kinetic model describing the net and gross synthesis rate is proposed, and on the basis of this model, we propose that the decomposition reaction suppresses the production of H₂O₂ to a greater extent than hydrogenation and that catalyst design studies should aim at blocking or generating catalysts without O–O dissociation sites.