Selective catalytic oxidation of ammonia over MnO x –TiO 2 mixed oxides

• Published in: RSC advances 2016, Vol.6 (91), p.88117-88125
• Main Authors: Song, Dongdong, Shao, Xunzhe, Yuan, Menglong, Wang, Li, Zhan, Wangcheng, Guo, YangLong, Guo, Yun, Lu, Guanzhong
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C6RA20999H

The selective catalytic oxidation of ammonia to nitrogen (NH 3 –SCO) was investigated over MnO x –TiO 2 . The physicochemical properties of MnO x –TiO 2 were characterized by XRD, O 2 -TPD, NH 3 -TPD, H 2 -TPR and XPS, and the reaction mechanism was studied by in situ DRIFTS. The addition of Mn into TiO 2 accelerated the support phase transformation and the formation of Mn–O–Ti bonds. MnO x (0.25)–TiO 2 showed the best performance in NH 3 –SCO, for which complete conversion of NH 3 was obtained at 200 °C with the temperature window (180–300 °C) for N 2 yield > 80%. The formation of Mn–O–Ti provided abundant oxygen vacancies which promoted the adsorption and dissociation of molecular oxygen to form active oxygen species. The finely dispersed MnO x species on the support favored NH 3 adsorption. N 2 O was produced over the whole temperature range while NO x was produced only at high temperatures (>250 °C). N 2 O was formed from the combination of two HNO species at low temperatures, whereas it was formed from NH 3 and nitrate/nitrite species reaction at high temperatures.