Enhancing of low-temperature OHC-SCR activity of Ag/TiO2 with addition of MnO2 nanoparticles, and performance evaluation using diesel engine exhaust gases

Abstract

The purpose of this study is to investigate the NO x removal activity of Ag/TiO 2 catalyst with addition of MnO 2 to improve the low temperature activity in the SCR system. The catalysts were prepared using washcoating method and were characterized with SEM, BET, XRD and FT-IR analyzes. According to results of SEM analysis, the catalysts exhibited a regular structure and fine particles dispersed over the surface and pores. BET analysis showed that the surface area and pore volume of catalysts decreased significantly with increasing of Mn amount. A strong interaction between catalytic materials and TiO 2 was determined by XRD analysis. FT-IR results indicated the presence of loading catalytic species on the catalyst surface. The effects of MnO 2 amount, reaction temperature, space velocity and engine load on catalytic performance were investigated by using ethanol as the reductant. The results indicated that Ag–Mn (3%)/TiO 2 catalyst was very effective in the temperature range of 170–290 °C. NO x conversion on the Ag–Mn (3%)/TiO 2 catalyst reached 92.9% at 290 °C and 30000 h −1 space velocity. The NO x removal performance of Ag/TiO 2 catalyst with high amount of MnO 2 decreased at low temperatures. In general, NO x conversion ratios of the catalysts reduced at 50000 h − 1 . • NO x removal performance of Ag based catalysts are insufficient at low temperatures. • Ag–Mn (3%)/TiO 2 catalyst shows highest NO x conversion ratios at low temperatures. • High MnO 2 loading reduces catalytic activity at low temperatures. • Increasing of GHSV decreases activity of catalysts.