High performance Pd catalysts supported on bimodal mesopore silica for the catalytic oxidation of toluene

Abstract

A series of bimodal mesoporous silica (BMS-x)-supported Pd catalysts were successfully prepared by a facile sol-gel approach, followed by an impregnation method. The synthesized catalysts were characterized by several analytical techniques and the oxidation of toluene was used to evaluate their catalytic performance. Textural analysis showed that all samples had high surface areas (∼1000 m2/g), large pore volumes (∼1.2 cm3/g) and uniform mesopore size (∼2.6 nm). Defining the level of ammonia solution to within a certain range resulted in the catalysts possessing a typical bimodal mesoporous structure with an intraparticle framework mesopore and an interparticle textural mesopore (18–40 nm). Transmission electron microscopy observations and CO chemisorption results revealed that this unique bimodal mesoporous structure helped to decrease the particle size of Pd nanoparticles and could further enhance their dispersion. Activity tests revealed the Pd/BMS-5–Pd/BMS-20 catalysts with a bimodal mesopore structure possessed superior catalytic performance for the oxidation of toluene compared to Pd/BMS-30 with a unimodal mesopore structure. More importantly, compared with the Pd/MCM-41 and Pd/MCM-48 catalysts, Pd/BMS-15 had improved hydrothermal stability and catalytic performance at a high gas hourly space velocity of 70000 h−1. These results indicate the potential application of the catalysts for the elimination of volatile organic compounds.