Browse Publications Technical Papers 2019-01-0735
2019-04-02

Low-Temperature NH 3 Storage, Isothermal Desorption, Reactive Consumption, and Thermal Release from Cu-SSZ-13 and V 2 O 5 -WO 3 /TiO 2 Selective Catalytic Reduction Catalysts 2019-01-0735

Worldwide, regulations continue to drive reductions in brake-specific emissions of nitric oxide (NO) and nitrogen dioxide (NO2) from on-highway and nonroad diesel engines. NOx, formed as a byproduct of the combustion of fossil fuels (e.g., natural gas, gasoline, diesel, etc.), can be converted to dinitrogen (N2) through ammonia (NH3) selective catalytic reduction (SCR). In this study, we closely examine the low-temperature storage, isothermal desorption, reactive consumption, and thermal release of NH3 on commercial Cu-SSZ-13 and V2O5-WO3/TiO2 SCR catalysts. Catalyst core-reactor, N2 adsorption (BET) surface area, and in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) experiments are utilized to investigate the fundamental chemical processes relevant to low-temperature (T < 250°C) NH3 SCR. Results show that NH3 stored at low-temperature continuously, yet slowly releases from the SCR catalysts, and that nearly all of the weakly bound NH3 stored on Cu2+ sites of the Cu-SSZ-13 catalyst will isothermally desorb from the catalyst in the absence of NOx. However, in the presence of NOx, a large fraction of this weakly bound NH3 will react with NOx, contributing to the total NOx conversion of the catalyst. The authors anticipate that the results presented herein can benefit the research communities’ efforts to reduce NOx emissions in comparison to today’s regulated limits by improving the understanding of critical low temperature chemical processes.

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