Pd/silicalite-1: An highly active catalyst for the oxidative removal of toluene

Catalytic combustion is thought as an efficient and economic pathway to remove volatile organic compounds, and its critical issue is the development of high-performance catalytic materials. In this work, we used the in situ synthesis method to prepare the silicalite-1 (S-1)-supported Pd nanoparticles (NPs). It is found that the as-prepared catalysts displayed a hexagonal prism morphology and a surface area of 390-440 m(2) /g. The sample (0.28Pd/S-1-H) derived after reduction at 500 degrees C in 10 vol% H-2 showed the best catalytic activity for toluene combustion (T-50% = 180 degrees C and T-90% = 189 degrees C at a space velocity of 40,000 mL/(g(.)hr), turnover frequency (TOFPd) at 160 degrees C = 3.46 x 10(-3) sec(-1), and specific reaction rate at 160 degrees C = 63.8 mu mol/(g(Pd.sec))), with the apparent activation energy (41 kJ/mol) obtained over the best performing 0.28Pd/S-1-H sample being much lower than those (51 -70 kJ/mol) obtained over the other samples (0.28Pd/S-1-A derived from calcination at 500 degrees C in air, 0.26Pd/S-1-im derived from the impregnation route, and 0.27Pd/ZSM-5-H prepared after reduction at 500 degrees C in 10 vol% H-2 ). Furthermore, the 0.28Pd/S-1-H sample possessed good thermal stability and its partial deactivation due to CO2 or H2O introduction was reversible, but SO2 addition resulted in an irreversible deactivation. The possible pathways of toluene oxidation over 0.28Pd/S1-H was toluene -> p-methylbenzoquinone -> maleic anhydride, benzoic acid, benzaldehyde -> carbon dioxide and water. We conclude that the good dispersion of Pd NPs, high adsorption oxygen species concentration, large toluene adsorption capacity, strong acidity, and more Pd0 species were responsible for the good catalytic performance of 0.28Pd/S-1-H. (C) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

In this study, Pd nanoparticles supported on silicalite-1 were prepared using the in situ synthesis method. The resulting catalyst exhibited excellent catalytic activity and thermal stability for the combustion of toluene. The study provides insights into the factors contributing to the catalytic performance of Pd/S-1 catalysts.