Enhanced water and sulfur resistance of a palladium/ceria-zirconia catalyst for low-concentration methane combustion through silicate modifying support properties

Ceria-zirconia (CeO₂-ZrO₂) supported palladium (Pd) represents a class of active catalysts for the catalytic combustion of low-concentration methane (CH₄), a potent greenhouse gas. Adjusting the surface properties of the support and thereby modifying the metal-support interaction are expected to enhance the activity of the catalyst and mitigate catalytic deactivation caused by water vapor (H₂O) and sulfur dioxide (SO₂). In this study, we adjust the surface properties of the Ce_0.5Zr_0.5O₂ (CeZr) support by silicate deposition. The silicates enriched on the surface of Ce_0.5Zr_0.5O₂ crystallites reduced the surface Ce³⁺ content, weakened the electron transfer from the support to palladium, thereby enhancing the PdO content and the reducibility of palladium species. The methane turnover frequency (TOF) of the silicate-modified catalyst was 1.3 times that of the Pd/CeZr catalyst at 260 °C under dry conditions. The reduced Ce³⁺ content also decreased the concentration of surface oxygen vacancies and thereby inhibiting the adsorption of H₂O and SO₂ on the catalyst surface. When reaction gases contained 10 vol% H₂O, the TOF value over the silicate-modified catalyst at 340 °C was 2.1 times higher than that over the Pd/CeZr catalyst, and these two catalysts achieved 97.8% and 67.5% methane conversion at 420 °C, respectively. After sulfur poisoning, the silicate-modified catalyst demonstrated 2.5 times higher TOF than the unmodified catalyst at 360 °C, and these two sulfur-poisoned catalysts achieved 60.9% and 30.5% methane conversion at 420 °C, respectively. This study provides valuable insights into developing a high-performance Pd/CeO₂-ZrO₂ catalyst for methane combustion applications.