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Diesel engines are becoming popular because of more fuel efficient and durability. While the CO and HC impurities are significantly lower than in gasoline engines, the design strategies for reduction of Particulate Matter and Nitrogen Oxides remain a major challenge for environment. The work mainly focused on reduction of NOx from diesel engines using SCR technology under Indian driving conditions and furl availability. With BS III/IV fuel available in the country, the catalyst system of choices the Vanadia Tungsten Titania (VWT) system because of its proven resistance to Sulfur poisoning. However, under urban driving conditions on Indian roads, the major obstacle is the low engine out temperatures which are below the normal operating temperature window (200 to 450 °C) of VWT - SCR.

Diesel exhaust is typically at lower temperature compared to gasoline exhaust and would need a catalyst that has activity in low temperature range to be effective. Hence considerable research has been directed to improve low temperature activity of catalysts used in diesel application. One of the aspects that has been widely reported in literature is that small Pt clusters have a positive effect on reducing the CO light off temperature (LOT). To examine this phenomenon closely, the present work was taken up to correlate Pt cluster size with performance. Catalysts were prepared on various supports - Alumina, Siliceous clay, ceria-zirconia, etc with different metal loadings and the calcinations conditions were varied both in time and temperature as well as calcinations atmosphere. The cluster sizes were ascertained using Phillips Tecnai 20 Transmission Electron Microscope.