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In this work, an in-house computational code capable of simulating highly coupled physicochemical phenomena occurring in ammonia/urea SCR (selective catalytic reduction) was developed. On the basis of this computational code, the kinetic parameters of catalytic reactions were newly calibrated using the experimental results obtained over a commercial ammonia/urea SCR washcoated Fe-ion-exchanged zeolite-based catalyst. Powder-phase NH 3 TPD (temperature-programmed desorption) experiments were performed to calibrate the kinetic parameters of NH 3 adsorption and desorption, and core-out monolith experiments were conducted to estimate the kinetic parameters of various deNO x reactions as well as NH 3 oxidation. The currently established SCR model and kinetic parameters gave a good prediction for both steady-state and transient experimental results for a wide range of operating conditions. The main objectives of this study were to develop numerical tools and their implementation methodologies that can be cost-effectively applied to the design and development of real-world ammonia/urea SCR systems. Details of the procedures and techniques in numerical modeling and kinetic parameter calibration are described step-by-step in this article.

The effects of hydrocarbons (HCs) on a combined selective catalytic reduction (SCR) system by NH3 and mixed HCs for simulated exhaust over five different types of Cu2+-exchanged zeolite catalysts have been systematically examined according to the reaction temperature. CuSSZ-13 with three-dimensional (3D) small pores and CuFER with 2D medium- and small-pore channels showed good resistance to poisoning by heavy HCs such as dodecane (C12H26) and m-xylene (C8H10), while they were not tolerant to poisoning by short-chain HCs such as propylene (C3H6). The deNOx activities of CuZSM-5 and CuBEA containing 3D medium- and large-pore channels, respectively, were significantly decreased by the inclusion of C12H26 in the reaction feed stream. Another large-pore channel-based zeolite catalyst, CuMOR, showed a peculiar behavior of NOx reduction by the combined SCR: complete conversions of NO and NH3 without any side reactions in the medium-temperature region, probably due to small-pore side pockets alongside straight large-pore channels. The NH3/SCR performances of the catalysts tested varied depending on the structural features of the zeolite supports, while there were somewhat common features according to the reaction temperatures. Inhibition of surface NO oxidation by adsorbed HCs was the primary cause of the decrease in NH3/SCR performance at low temperature. In the medium-temperature region, NH3 reacted with HCs to form nitrile compounds through ammoxidation, resulting in a further decrease in deNOx activity due to a shortage of NH3 for NOx reduction. On the other hand, deNOx activity increased at high temperature due to NOx reduction by HCs present in the feed stream.