Low temperature CO oxidation over Ag/SBA-15 nanocomposites prepared via in-situ “pH-adjusting” method

The catalytic activity for CO oxidation over Ag/SBA-15 catalysts prepared by in-situ “pH-adjusting” method is studied in this paper. The prepared silver catalyst (7.8 wt%) under pH = 5 condition gives 98% of CO oxidation at 70 °C, as compared to 140 °C with conventional silver catalyst without pH adjusting (6.1 wt%). However, more Ag2O clusters are formed inside the channels with the further pH increasing, resulting in the low catalytic activity for CO oxidation. Therefore the pH value shows significant effect on the silver content and the species state, consequently affecting the catalytic activity of Ag/SBA-15 catalysts for CO oxidation.

The pH value showed significant effect on the silver content and the species state, consequently affecting the catalytic activity of Ag/SBA-15 catalysts for CO oxidation. The pH adjustment of synthesis gel to 5 induced the formation of the Ag species with higher amount inside the channels and the higher activity for low-temperature CO oxidation, giving 100% CO conversion at 70 °C. However, the further increasing of the pH value resulted in more Ag2O clusters formed inside the channels, leading to a decrease of catalytic activity for CO oxidation.Figure optionsDownload as PowerPoint slideHighlights
► The pH adjusting to 5 and 7.5 increased the silver loading inside the SBA-15.
► The silver catalyst prepared under pH = 5 condition gave 100% CO conversion at 70 °C.
► The pH higher than 5 induced the formation of more Ag2O, giving the low activity.