The optimization of Palladium–Silver/Zirconia alloy catalyst structure for methane combustion

Abstract

Bimetallic alloy catalysts are gaining popularity for methane combustion owing to their high activity and variable structure. Palladium and silver (PdAg) are the most often used alloys due to their simplicity of alloying. The use of suitable support materials is critical for increasing PdAg catalytic performance. In this work, PdAg alloys are supported by monoclinic zirconium dioxide (m-ZrO2) in various phases to fine-tune the active phase structure. Methane temperature-programmed oxidation (methane-TPO) is used to evaluate various designs for oxidizing methane. The catalysts that are concurrently supported with Pd and Ag have a great catalytic activity. The T50 (50 % conversion temperature) of methane in PdAg/Z sample is 120.7 and 35.0 °C lower than PdfAg/Z (Pd supports first) and PdAgf/Z (Ag supports first). Furthermore, when H2-TPR and O2-TPD results are combined, PdAg/Z catalysts have the lowest PdHx decomposition temperature and the highest PdO decomposition temperature (661.8 °C), suggesting that PdAg/Z catalysts may better retain the PdO–Pd active phase structure. Furthermore, XRS analysis reveals that PdAg/Z has the greatest Pd2+/Pd0 ratio (2.69). This indicates that the metal loading sequence employed in catalyst manufacture may affect the catalyst's active phase structure and hence activity.