The nature of silica-to-alumina ratio effect on lean methane oxidation over Pd/Beta zeolite catalysts

The silica-to-alumina ratio (SAR) effect on lean methane oxidation over Pd/Beta catalysts was investigated. Light-off test, steady-state performance and kinetic analysis demonstrate the activity of Pd/Beta catalysts shows a volcano-shaped dependence on SAR. Pd/Beta402 presents the highest activity among all samples, regardless of the presence of water. By the employment of H2-TPR, CO-chemisorption, STEM-EDS, TGA and NH3-TPD, it is found that the activity of Pd/Beta catalysts is essentially influenced by their acidity, which is the nature of the SAR effect on methane oxidation. Increasing SAR leads to lower acidity, resulting in less formation of inactive Pd2+ and higher hydrophobicity which benefit methane oxidation. However, the larger PdO particles are formed at the same time, leading to a decrease in the amount of exposed PdO which is detrimental to methane oxidation. This work can guide the design of state-of-the-art zeolite-supported Pd-based methane oxidation catalysts.

Automated summary

This study investigates the silica-to-alumina ratio (SAR) effect on lean methane oxidation over Pd/Beta catalysts. The results show that Pd/Beta402 exhibits the highest activity among all samples. Through various experiments and analyses, it is found that the acidity of Pd/Beta catalysts is the major factor influencing their activity, with increasing SAR leading to lower acidity. This results in less formation of inactive Pd2+ and higher hydrophobicity, which benefits methane oxidation. However, increasing SAR also leads to larger PdO particles and a decrease in the amount of exposed PdO, which is detrimental to methane oxidation.