Preferential carbon monoxide oxidation on Ag/Al-SBA-15 catalysts: Effect of the Si/Al ratio

• Al-SBA-15 catalysts were prepared by in situ “pH-adjusting” method.
• Si/Al ratio has an important effect on the structure and catalytic activity.
• A few Al particles are beneficial to the formation of highly dispersed Ag0 particles.
• Ag/Al-SBA-15 (200) catalyst shows highly catalytic activity and selectively.
• Ag/Al-SBA-15 (200) exhibits better activity under the presence of H2O and CO2.

In this work, mesoporous aluminosilicate supports (Al-SBA-15) were prepared using in situ “pH-adjusting” method, and Ag nanoparticles were supported on Al-SBA-15 supports by using the simple impregnation method. The effect of the Si/Al ratios of mesoporous support on the structure of Ag catalysts and the catalytic performance for the preferential oxidation of CO (CO PROX) in H2-rich gases was investigated. The Ag/Al-SBA-15 catalyst with an appropriate Si/Al molar ratio of 200 has been found to show highly catalytic activity, selectivity and stability. A series of supports and corresponding supported Ag catalysts with different Si/Al ratios were characterized by ICP-AES, XRD, N2 adsorption–desorption, 27Al NMR, FT-IR of adsorbed pyridine, TEM, H2-TPR and XPS. The results indicated that the addition of a small amount of Al is beneficial to the formation of small sized highly dispersed metal Ag particles in the channel, consequently improving the catalytic activity. In addition, the Ag/Al-SBA-15 (200) catalyst also exhibited better catalytic activity under the presence of H2O and CO2 in the stream.