Diesel soot oxidation over silver-loaded SiO2 catalysts

The catalytic behavior of Ag-loaded fumed SiO2 has been investigated for diesel soot oxidation. The diesel soot generated by burning pure Mexican diesel in laboratory was oxidized under air flow in presence of the catalyst inside a tubular quartz reactor in between 25 and 600 °C. UV–vis optical spectroscopy was utilized to study the electronic state of silver in Ag/SiO2 catalysts. The soot oxidation was seen to be strongly enhanced by the presence of metallic silver on the catalyst surface, probably due to the formation of superoxide ion O2−. During the catalytic process, the Ag2O species on the catalyst acts as a strong oxidizing agent which gets reduced readily by the soot carbon to metallic Ag. The Ag/SiO2 catalysts exhibited strong performance for diesel soot oxidation below 300 °C. Mechanical mixing of extra SiO2 with 3% Ag loaded SiO2 resulted a further increase of soot oxidation rate, probably due to the increased interactions of O2− and soot particles through the highly porous surface of SiO2.

3%Ag/SiO2 catalyst is an effective catalyst for diesel soot oxidation at low temperatures (150–300 °C). This catalyst is highly stable during several consecutive reaction cycles.Figure optionsDownload high-quality image (104 K)Download as PowerPoint slideHighlights
► Ag/SiO2 is highly active and stable during several diesel soot oxidation cycles.
► UV–vis spectroscopy was utilized to study the electronic state of silver in Ag/SiO2.
► The soot oxidation was strongly enhanced by metallic silver on the catalyst surface.
► Mechanical mixing of SiO2 with Ag/SiO2 resulted a further increase of soot oxidation rate.
► Interactions of O2− generated over Ag/SiO2 and soot particles through SiO2.