Supported Nanometric Pd Hierarchical Catalysts for Efficient Toluene Removal: Catalyst Characterization and Activity Elucidation

Micro-/mesoporous composite materials with coke-resistant ZSM-5 and three-dimensional large-pore KIT-6 as their micro- and mesoporous components, respectively, were synthesized using a simple in situ overgrowth approach. The hydrothermal stabilities and acidities of the biporous catalysts were found to be significantly enhanced. All composite materials acted as powerful catalysts for toluene oxidation. Among them, Pd/ZK-6% showed the highest catalytic activity, with 90% toluene decomposition at 203 °C, which is more than 30 °C lower than required for Pd/KIT-6. It can be anticipated that the specific surface area and acidity have a synergistic effect on the Pd dispersion. Overall, the catalytic activities were found to be primarily correlated with the specific surface area, support acidity, Pd dispersion, and toluene adsorption capability.