Highly dispersed Pd catalysts prepared by a sonochemical method for the direct synthesis of hydrogen peroxide

Abstract Pd catalysts prepared by a sonochemical method that is known to be effective in metal dispersion are applied to direct H 2 O 2 synthesis. To determine the effect of the preparation method on the catalytic performance, Pd catalysts were supported on TiO 2 and SiO 2 by a sonochemical method and general incipient wetness method (IWI), and supports were compared. The sonochemical preparation method achieved the highest Pd dispersion value of 16.6% in the TiO 2 supported catalyst, which is attributed to a synergistic effect between the sonochemical method and TiO 2 support. A near-homogeneous and small size nucleation is often reported in sonochemical methods, and oxygen vacancies in TiO 2 are reported to be strong adsorption sites for Pd nucleation. However, SiO 2 support has not been reported to have obvious oxygen vacancies, and sonochemically prepared Pd/SiO 2 showed the lowest Pd dispersion in addition to a large Pd particle size. In the direct synthesis of H 2 O 2 , a remarkably high H 2 conversion of 22% was achieved in sonochemical Pd/TiO 2 , which led to the highest H 2 O 2 yield of 16% and H 2 O 2 production rate of 729.0 mmol/g Pd h .