Improving the performance of Pd based catalysts for the direct synthesis of hydrogen peroxide via acid incorporation during catalyst synthesis

The direct synthesis of hydrogen peroxide from molecular H2 and O2 offers an attractive alternative to the current means of production of this powerful oxidant, on an industrial scale. Herein we investigate the role of nitric acid addition, during catalyst preparation as a means of improving catalytic performance, under reaction conditions that have previously been found to be optimal for H2O2 production. The addition of dilute nitric acid during catalyst preparation is found to lead to a significant improvement in H2O2 synthesis activity, through the modification of particle size and control of Pd oxidation state

Palladium-tin catalysts for the direct synthesis of H2O2 with high selectivity

Hydrogen peroxide is synthesized industrially without direct contact of hydrogen and oxygen in order to achieve high concentrations. For many applications, only dilute aqueous solutions are needed. Freakley et al. report an improvement in the direct synthesis of hydrogen peroxide over using palladium-tin alloys. This catalyst still achieves selectivities of >95%, like palladium-gold alloys, but is cheaper and can suppress reactions that decompose the product

Direct synthesis of hydrogen peroxide using ruthenium catalysts

The direct synthesis of hydrogen peroxide is investigated using ruthenium containing catalysts. Ruthenium is not soluble in Au but forms alloys with palladium. We have therefore investigated Ru–Au, Ru–Pd as well as trimetallic formulations supported on titania. The addition of ruthenium enhances the direct synthesis activity for all the catalysts studied and the effect is dependent on the amount of ruthenium added. The calcination conditions are shown to affect both activity and reusability

Effect of reaction conditions on the direct synthesis of hydrogen peroxide with a AuPd/TiO2Catalyst 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

The role of the support in achieving high selectivity in the direct formation of hydrogen peroxide

Pd-only, Au-only and bimetallic AuPd catalysts supported on a range of supports (Al(2)O(3), TiO(2), MgO, and C) have been prepared by impregnation and tested for the hydrogenation and decomposition of hydrogen peroxide under conditions similar to those used in direct synthesis of hydrogen peroxide. Hydrogenation and decomposition are the main pathways for loss of selectivity and yield in the direct synthesis reaction, and the support is found to be a crucial parameter with respect to hydrogenation and decomposition activity. We show that by making the right choice of support for both the monometallic and bimetallic Au and Pd catalysts, it is possible to achieve very low hydrogen peroxide hydrogenation and decomposition activity, thus enhancing hydrogen peroxide productivity during synthesis. Carbon is found to be the optimal support for both monometallic Au and Pd catalysts as well as Au -Pd alloys, since carbon-supported catalysts gave the lowest hydrogenation and decomposition activities. Au-only catalysts were generally less active than Pd-only catalysts when utilizing the same support and metal loading. The addition of Au to Pd catalysts supported on TiO(2) and carbon resulted in a decrease in both H(2)O(2) hydrogenation and decomposition while the reverse effect was observed for the Al(2)O(3) and MgO-supported catalysts. These effects are discussed in terms of the basicity of the support, and in particular the isoelectronic point of the support, which is a major factor in controlling the stability of hydrogen peroxide under reaction conditions

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

Effect of Reaction Conditions on the Direct Synthesis of Hydrogen Peroxide with a AuPd/TiO 2

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