Effects of fluorinated hydrocarbon addition on H2O2 direct synthesis from H2 and air over an Au–Pd bimetallic catalyst supported on rutile-TiO2

Abstract

Synthesis of H₂O₂ by oxidation of H₂ with air on Au–Pd/TiO₂ was studied and it was found that H₂ conversion and H₂O₂ selectivity were strongly affected by the crystal phase of the TiO₂ support for Au–Pd. At 0.1 MPa, brookite type TiO₂ was active for H₂O₂ synthesis because of high H₂ conversion (40%) and selectivity (67%). In contrast, rutile type TiO₂ showed high H₂ conversion but low selectivity. With increasing H₂ pressure, H₂O₂ selectivity increased on Au–Pd/rutile TiO₂ and the H₂O₂ yield became much higher on the catalyst supported on rutile TiO₂ than those on brookite or anatase at 1.0 MPa. The effects of fluorinated hydrocarbon addition to reaction media were also studied, and it was found that the addition of a small amount of fluorinated hydrocarbon was effective for increasing H₂O₂ productivity. The optimized fluorinated hydrocarbon was CF₃(CF₂)₅CF₃, and the amount was 1/10 (7.5 ml) of the reaction media (75 ml). The H₂O₂ formation rate of 3.78 mmol h⁻¹ was achieved under the optimized conditions, and the concentration of 1.8 wt% H₂O₂ was achieved after 20 h.