Granular-carbon supported nano noble-metal (Au, Pd, Au-Pd): new dual-functional adsorbent/catalysts for effective removal of toluene at low-temperature and humid condition

Treatment of the volatile organic compounds (VOCs) especially aromatic compounds such as toluene at low temperature and in the highly humid condition is currently a great challenge. New dual functional adsorbent/catalysts have been developed in this study to minimize the mass-transfer limitation at low temperature. The ready-to-practically-use materials, which consisted nano-sized noble metal (Au, Pd, Au-Pd) supported on granular carbon (GC) have been prepared using a metal-sol method. The surface morphology, and structure of these granular materials were characterized to confirm the presence of nano-sized noble metal on the GC as well as the properties of the dual functional adsorbent/catalyst. The results of catalytic performance revealed that the presence of Pd played an important role in the formation of nano Au particles, which were the catalytic active-site for toluene oxidation. At 60% relative humidity and 150°C the dual functional adsorbent/catalyst, Au-Pd/GC, exhibited 97.2% toluene removal. Importantly, the kinetic analysis for the catalytic oxidation of nano-sized 0.5%Au-0.27%Pd/GC catalyst showed that the Langmuir-Hinshelwood mechanism provided a good fit towards the experimental data and allowed to determine the kinetic parameters of the reaction-rate law $\left(-r_A=\frac{k\cdot K_A\cdot C_A}{1+K_A\cdot C_A}\cdot \frac{K_{O_2}\cdot C_{O_2}}{1+K_{O_2}.C_{O_2}}\right)$. The activation energy, adsorption enthalpy of toluene, and oxygen on the catalyst were reported.