Boosting sulfur tolerance in Pd/beta zeolite catalyst for toluene oxidation: the role of CeO2

This study examined the impact of CeO2 addition on the sulfur tolerance of Pd/beta zeolite catalyst in toluene catalytic oxidation. By preparing and assessing Ce-modified beta zeolite-supported Pd catalysts, it is found that the toluene complete conversion over Pd/7.5Ce-beta zeolite occurs at 190 °C, with a minimal increase of 20 °C even after sulfur poisoning. It is shown that Ce-doping markedly enhances sulfur tolerance besides catalytic activity. The underlying mechanism involves CeO2 sites capturing sulfur species, thus safeguarding active Pd species from sulfur poisoning. It can be observed that Pd0 active sites, which are crucial in the catalytic high activity, are still present in the most severely poisoned catalyst. Furthermore, Ce-modified catalyst exhibits a more stable pore structure and increased acid strength after sulfur poisoning, all of which are beneficial to improving the sulfur tolerance. Consequently, Pd/Ce-beta zeolite is a promising solution for processing sulfur-containing volatile organic compounds, offering valuable insights for developing effective and sustainable catalysts for environmental remediation.