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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.

Small Commercial Vehicle (SCV) is an emerging Commercial Vehicle (CV) segment both in India and throughout the world. Vehicles in this segment have diesel engine of capacity less than 1 l and GVW of less than 3.5 t. Normally for the CV, engines are tested on engine dynamometer for emission test, but SCV are tested on chassis dynamometer as they are classified as N1.1 class vehicles. Hence SCV have to follow same emission regulations as diesel passenger cars. The main challenge is to meet BS-IV NOx and PM emission target together with high torque optimization along with required durability targets. This paper addresses this challenge and reports the work carried out on an Indian SCV with 0.7 l naturally aspirated indirect injection diesel engine.

Technologies for exhaust aftertreatment of diesel engines are driven by emission standards and Selective Catalytic Reduction (SCR) will play a key role in complying with the requirements, particularly for the heavy duty vehicles. Amongst the variety of catalysts for the SCR reaction, the Vanadium-Tungsten-Titanium-Based (VWT) system is preferred over the base metal doped zeolite because of the established advantages of wide temperature window, robust and durable performance and resistance to sulfur exposure. While the basic chemical reactions involved in ammonia-SCR are well known, the challenge lies in identifying the right combination of substrate and wash coat formulation to meet with customer specific requirements. An insight into the relevant materials properties of the substrates as well as the bulk surface properties of the wash coat such as its ammonia storage capacity, V2O5 dispersion and stability are important.