Diesel engines produce high thermal efficiency and low CO2 but release more particulate matters (PM) and NOx which are harmful to atmosphere as well as human beings. In India, these emissions are controlled by after exhaust gas treatment and are regulated by Bharat Stage Emission Standards. The effective technology for NOx reduction is Selective Catalytic Reduction (SCR). In this study selective catalysis is carried out over Mn/Ce/Al2O3 catalysts which were prepared by sol-gel and combustion synthesis methods. These catalysts were coated on honeycomb ceramic samples and characterized by SEM. The coated samples were tested in Single cylinder Diesel Engine. The results showed nearly 60%NO conversion. © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved.