N₂O Formation Mechanism During NSR Process Using CO As A Reductant

N₂O is a greenhouse gas and has 298 times the Global Warming Potential?GWP? of CO2, and it can also degrade the ozone layer seriously. It is found that large amount of N₂ O forms during NSR process, so investigation of the formation mechanism of N₂ O has guiding significance for the development of high performance NSR catalyst. In this paper, N₂ O formation pathway, effect of H₂ O and cycle frequency on N₂ O formation during NSR process using CO as a reductant were investigated over Pt-BaO/Al₂O₃ catalyst at low to intermediate temperatures.Pt-BaO/Al₂O₃ catalyst was prepared by the incipient wetness impregnation method. BET, XRD and CO-pulse chemisorption were used to studied the characteristics of catalyst. We combined dynamic NSR activity measurements and transient in situ DRIFTS experiments to elucidate N₂ O formation mechanism. Cycling activity measurements were carried out to evaluate N₂ O evolution and DRIFTS experiments were performed to study the changes of surface intermediates in NSR process.N₂O is formed in the lean, rich and delay2 phase. In the lean phase, N₂ O formation is related to the reactions between surface isocyanate and gaseous NO/O2, and NO is more responsible for N₂ O formation than O2. Moreover, N₂ O production decreases with H₂ O due to the hydrolysis of isocyanate species. In the rich phase, the amount of N₂ O formation also decreases in the presence of H₂ O at higher temperature due to the higher reduction ability of H₂ generated from the WGS reaction. During the delay2 phase, N₂ O formation is mainly by reacting of nitrites and Pt0-CO. Furthermore, the presence of H₂ O decreases the stability of nitrites, and thereby results in more N₂ O production at low temperature.The results indicate that N₂ O selectivity decreases with increasing temperature, the presence of H₂ O are beneficial in inhibiting N₂ O generation, and to some extent, N₂ O selectivity can be controlled by tuning the cycle frequency.