Promotional mechanism of WO3 over RuO2-Fe2O3 catalyst for NH3-SCO reaction

• Published in: Applied catalysis. A, General General, 2018-07, Vol.561, p.158-167
• Main Authors: Wang, Huimin, Ning, Ping, Zhang, Qiulin, Liu, Xin, Zhang, Tengxiang, Fan, Jie, Wang, Jing, Long, Kaixian
• Format: Article
• Language: English
• Subjects: Acid sites; N2 selectivity; Promoting effects; Strong interaction
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.05.020

The introduction of WO3 enhanced the capacity of ammonia adsorption of RuO2-Fe2O3 catalyst, as well as increased high-temperature N2 selectivity. The NH3-SCO reaction over RuO2-WO3-Fe2O3 catalyst mainly followed the “internal” selective catalytic reduction (iSCR) mechanism. The key intermediate (-NH2) could rapidly react with the in situ-generated NO ad-species to form N2 and H2O. [Display omitted] •RuO2-WO3-Fe2O3 exhibited excellent NH3-SCO performance at 250–400 °C.•The introduction of WO3 enhanced the surface acidity of the RuO2-Fe2O3 catalyst.•The strong interaction between WO3 and Fe2O3 decreased the reducibility of RuO2-Fe2O3.•The SCO reaction over RuO2-WO3-Fe2O3 followed the “iSCR” mechanism. The promoting effects of WO3 on RuO2-Fe2O3 catalyst were systematically investigated for the selective catalytic oxidation of ammonia to nitrogen. It was found that the introduction of 5 wt.% WO3 led to a dramatic promoting effect on the high-temperature N2 selectivity of RuO2-Fe2O3 catalyst, giving 100% NH3 conversion at 250 °C and 94% N2 selectivity at a high temperature of 400 °C. In depth analysis using XRD, Raman and H2-TPR revealed that the addition of WO3 into the RuO2-Fe2O3 catalyst could strongly inhibit the crystallinity of Fe2O3 and decrease the reducibility of RuO2-Fe2O3 catalyst, which were related to the strong interaction between WO3 and Fe2O3. Moreover, in situ DRIFTS studies illustrated that the ammonia oxidation over 1RuO2-5WO3-Fe2O3 catalyst followed the iSCR mechanism, involving the oxidation of NH3 into NO species and the reaction of -NH2 with in situ-formed NO to form N2. The introduction of WO3 not only promoted the formation of more acid sites on the catalyst surface but also restrained the formation of nitrate species at high temperature, with few NOx formed, which contributed to the high N2 selectivity.