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Selective catalytic reduction (SCR) technology is being considered as the potential strategy for significant reduction of NOx emissions from diesel engines. Many challenges exist in the development of an On-Road SCR retrofit system in terms of system integration and optimization of control strategy in order to achieve highest NOx reduction given the diversity of duty cycles. The main considered challenges are: - The development of a generic control strategy that would work for a broad range of engines, - Development of a reliable and durable injection system that would be able to withstand the harsh environments on a heavy-duty vehicle, - Packaging of the system to be able to fit on a number of vehicles with different configurations, - Controlling ammonia slip and assurance of reducing agent (Urea) availability and quality. In this study a prototype SCR system was evaluated over engine and chassis dynamometer test cycles.

Non-PGM catalyst containing base metal mixed oxide (BMMO) supported on rare earth mixed oxide (REMO) had been evaluated by various methods for soot-oxidation activity. Thermo-gravimetric/Differential Thermal Analysis (TG/DTA) experiments and synthetic gas bench activity tests showed that the catalyst was able to oxidize soot at temperatures significantly lower than soot combustion temperature leading to a conclusion that soot was oxidized via direct reaction with active species of the catalyst surface. It had been shown that low-temperature soot oxidation occurred with and without NO present in the reaction gas. Evaluation on engine benches of the BMMO catalyst coated on diesel particulate filters (DPF) confirmed low-temperature soot oxidation in exhaust gas with low NO₂ concentration and a possibility of cost-efficient diesel exhaust aftertreatment system without increasing tailpipe NO₂ content.