Sulfur resistance mechanism of PdSx catalysts in catalytic oxidation of toluene

• Published in: Catalysis science & technology Vol. 14; no. 13; pp. 3739 - 3747
• Main Authors: Liu, Huadong, Bian, Jiawei, Sun, Zhaofei, Ling, Hao, Ju, Feng
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.07.2024
• Subjects: Catalysts; Catalytic oxidation; Flue gas; Oxidation resistance; Reaction mechanisms; Refineries; Sulfidation; Sulfur; Sulfur dioxide; Toluene; VOCs; Volatile organic compounds; Zeolites
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d4cy00349g

Toluene is a main component of volatile organic compounds (VOCs) in the refinery flue gas, and catalytic oxidation stands out as an efficient and energy-saving method for eliminating toluene. Nevertheless, the presence of SO2 within VOCs can result in the irreversible deactivation of the catalyst. The enhancement of the catalyst's sulfur resistance is imperative. Here, we prepared PdSx/Hβ-zeolite catalysts with exceptional sulfur resistance by using the gas-phase sulfidation method. The PdSx/Hβ-zeolite exhibits remarkable activity under the experimental conditions of 1000 ppm toluene and 21% O2, with a sustained conversion rate of toluene exceeding 76% even after the introduction of SO2. Based on the characterization of catalysts and resistance experiments, the reaction mechanism and sulfur resistance mechanism were studied. Pd0 serves as the active catalytic center, and the catalytic oxidation mechanism follows the Mars–van Krevelen (MVK) mechanism. The high sulfur resistance of the PdSx/Hβ-zeolite catalyst is attributed to the PdSx species, which is considered as the sulfur resistance center. The presence of PdSx facilitates SO2 desorption, thereby improving the catalyst's sulfur resistance. This work will provide new insights into enhancing precious metal catalysts' resistance to sulfur.