Nanometric palladium confined in mesoporous silica as efficient catalysts for toluene oxidation at low temperature

Short column SBA-15 supported Pd mesoporous catalysts with controllable acidity and expanded microporosity were firstly prepared through a simple “two-solvents” approach. The catalytic performances of the synthesized catalysts were evaluated for toluene oxidation. The characterization results reveal that Al atoms prefer to be tetrahedrally coordinated in the framework of the synthesized materials, and the acid sites can significantly promote Pd particle dispersion and metallic Pd oxidation due to their electrophilic characters. The Pd-confined catalysts possess high toluene turnover frequencies and toluene can be totally converted to CO2 and H2O below 210 °C. The oxidation reaction can be suppressed by water vapor due to the formation of inactive Pd-hydroxides, and the synthesized catalyst has a good hydrothermal stability and high tolerance to moisture. Both the specific surface area and the toluene adsorption/desorption property are not the main factors determining the catalytic activity. Overall, the toluene oxidation performance is closely related to the support microporosity and acidity, the Pd dispersion and the CO2 desorption capability.

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► Short column mesoporous silica with controllable acidity, expanded microporosity and 3-D micro/mesoporous composite structure.
► Both catalysts combined promoted accessibility and enhanced acid strength.
► Highly dispersed Pd-confined catalysts with improved hydrothermal stability.
► Catalyst with high turnover frequency and superior low temperature efficiency.