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

这个小企业创新研究第二阶段项目研究了一系列新的低成本非贵金属催化剂，用于将NH3选择性催化还原（SCO）为N2。尿素选择性催化还原（SCR）技术是目前广泛应用于柴油机车辆的NOx减排技术。使用SCR技术的一个常见问题是氨泄漏。 在NO转化不完全或排气温度升高的情况下，NH3将从排气中释放，导致许多环境问题。这种SCO技术可以在NexTech提出的催化剂上在低温下将有毒的氨转化为氮气和水。所提出的非贵金属催化剂已被证明是高活性的，并且在阶段I中耐受SO2和H2O。在~ 225 ℃时，NH_3转化率达100%，N_2选择性达90%以上。催化剂表现出相当的NH3转化率但更高的N2选择性（即，更少的NO和N2 O形成）。在第二阶段，将进一步改进催化剂配方以提高SCO性能，并将进行长期稳定性测试。在此之后，重点将转移到催化剂放大，整体上的修补基面涂层和评价在真实的柴油机排气条件下，这个项目的更广泛的影响/商业潜力是解决SCR系统中存在的NH3泄漏问题，使其应用于柴油机排气处理。当在SCR工艺中使用化学计量或过量的尿素时，这种SCO技术还可以帮助减少NOx排放量超过90%，为实现积极的NOx减排目标提供了一种极好的方法。与传统的含铂催化剂相比，所提出的非贵金属催化剂的替代物可以大大降低柴油机后处理系统的成本。所产生的信息可以提供新的见解，了解小分子，如NH3，NO，NO2和O2，在氧化物表面上的酸性和氧化还原位点的活化过程，使未来能够开发更好的催化剂，以进一步减排。

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.