SBIR Phase II: Selective Catalytic Oxidation of Ammonia to Nitrogen for Hot Exhaust Treatment

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This Small Business Innovation Research Phase II project investigates a new series of low-cost non- precious metal catalysts for selective catalytic reduction (SCO) of NH3 to N2. Selective catalytic reduction (SCR) of NO with urea is widely applied for abating NOx emissions in diesel engine vehicles. A common problem of using the SCR technology is ammonia slip. Under conditions of incomplete NO conversion or exhaust temperature upswings, NH3 will be released from the exhaust, resulting in a number of environmental problems. This SCO technology can convert the toxic ammonia to nitrogen and water on NexTech¡¯s proposed catalysts at low temperatures. The proposed non-precious metal catalysts have proven to be highly active and tolerant to SO2 and H2O in Phase I. 100% NH3 conversion and above 90% N2 selectivity were achieved at ¡Ý 225 ¡ãC. The catalysts exhibited comparable NH3 conversion but higher N2 selectivity (i.e., less NO and N2O formation) as compared to a conventional Pt-based catalyst. In Phase II, catalyst formulation will further be refined to improve SCO performance, and long term stability testing will be conducted. After that, the focus will be shifted to catalyst scale-up, washcoating on monoliths and evaluation under real diesel engine exhaust conditions.The broader impact/commercial potential of this project is to solve the NH3 slip problem existing in the SCR system, allowing its application in the diesel engine exhaust treatment. This SCO technology can also help reduce NOX emissions by greater than 90% when stoichiometric or excess amount of urea is used in the SCR process, providing an excellent approach for reaching aggressive NOX abatement goals. As compared to conventional Platinum containing catalysts, the substitution of the proposed non-precious metal catalysts could drastically reduce the cost of diesel engine after-treatment system. The generated information can provide new insights in understanding activation process of small molecules, such as NH3, NO, NO2 and O2, on the oxide surface with acid and redox sites, enabling development of better catalysts for further emission reduction in the future.