Improving the NH3 oxidation and removing NOx during ammonia-rich fuel catalytic combustion using the Ag/CuOx@SiO2 catalyst with high-temperature catalytic activity

Abstract

Listen

Translate article

Ammonia, as a carbon-free, hydrogen-rich and renewable fuel, is of great significance for building the zero-carbon emission energy supply system in the word. However, the drawbacks of high ignition energy and high NOx emissions limit its widespread application. Catalytic combustion provides a reliable option for NH3 combustion. In the study, the catalyst of Ag/CuOx@SiO2 catalyst with high-temperature catalytic activity was prepared, and the catalytic flow reactor was employed to evaluate the ability of the catalyst in enhancing NH3 oxidation and removal NOx during NH3-rich combustion with high temperature region (900 K∼1400 K) and wide equivalence ratio range (0.4 ∼ 1.2). The high-temperature catalytic activity of the catalyst was proved by XPS spectrogram that the valence states of Ag and CuOx species in the catalyst have not been changed after the catalytic combustion. The results of catalytic combustion indicated that the catalyst enhanced the NH3 oxidation significantly. Compared to NH3 combustion, the temperature of 100 %NH3 conversion (T100) was decreased by over 500 K during NH3 catalytic combustion. Moreover, catalytic combustion performed higher efficiency on enhancing NH3 oxidation than the approach of co-firing NH3 with higher reactive gas fuels. The T100 of NH3 catalytic combustion was lower by 200 K∼220 K than that of NH3/H2 and NH3/CH4 combustion. Furthermore, the catalyst reduced the NOx effectively during NH3/H2 and NH3/CH4 combustion. At 1400 K, NO selectivity during NH3/H2 and NH3/CH4 catalytic combustion reduced by 86.80 %∼90.42 % and 43.61 %∼61.42 % compared to the combustion, respectively. Additionally, the peak of N2O selectivity moved to lower temperature range during catalytic combustion. Especially in stoichiometric and fuel rich conditions, the peak temperature reduced by 100 K∼200 K. The study provided references for the development of catalysts in ammonia-rich fuel catalytic combustion.