Boosting Methane Combustion over Pd/Y2O3-ZrO2 Catalyst by Inert Silicate Patches Tuning Both Palladium Chemistry and Support Hydrophobicity

Supported palladium (Pd) catalysts are widely utilized to reduce the emission of exhaust CH(4 )from lean-burn engines by catalytic combustion. A large amount of water vapor in the exhaust makes hydroxyls accumulate on the catalyst surface at temperatures below 450 degrees C, leading to severe catalyst deactivation. Tuning palladium chemistry and inhibiting water adsorption are critical to developing active catalysts. Modifying the support surface with inert silicates would both change the palladium-support interaction and decrease water adsorption sites. This study reports an improved Pd/Y2O3-ZrO2 catalyst by constructing silicate patches on yttria-stabilized zirconia (Y2O3-ZrO2) support. The silicates hindered electron transfer from Y2O3-ZrO2 oxygen vacancies to palladium, which optimized palladium chemistry, especially the reducibility of active PdO species, and thereby boosted CH4 conversion under dry conditions. The temperature of 90% methane conversion (T90) over the catalyst decreased from 386 to 309 degrees C. Moreover, the inert silicates decreased surface oxygen vacancies of Y2O3-ZrO2 to improve support hydrophobicity, thereby inhibiting hydroxyl accumulation. The poisoning effect of water on the active sites located on the palladium-silicate interface was alleviated. When reaction gases contained 10 vol % water, the silicate-modified catalyst still showed higher activity with T-90 of 404 degrees C, which is lower than T-90 of 452 degrees C for unmodified catalyst. This work represents a step forward in preparing high-performance palladium catalysts for low-temperature wet methane combustion.

Automated summary

This study improves the performance of Pd/Y2O3-ZrO2 catalyst by constructing silicate patches on the support surface. This modification optimizes palladium chemistry, enhances CH4 conversion, reduces surface oxygen vacancies, and inhibits hydroxyl accumulation.