(6az) The Synergistic Effect of Copper and Niobium Species on a Novel Cu/Nb-Ti Mixed Oxide Catalyst for the Selective Catalytic Reduction of NOx with NH3

Wang, X., Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Institute of Industrial Ecology and Environment, College of Chemical and Biological Engineering, Zhejiang University
Li, W., Zhejiang University
Li, S. J., Zhejiang University
Shi, Y., Zhejiang University
Chen, L., Zhejiang University
Research Interests: A series of titanium-niobium oxide as the catalyst support was first synthesized by co-precipitation and then Cu/Nb-Ti ternary oxide catalyst was prepared through wetness impregnation. The optimal proportion was explored.And 0.8%Cu/Ti2NbOx exhibited the best catalytic activity with NOx conversion and N2 selectivity maintaining upon 90% and 97% respectively in the temperature range of 250oC-425oC under a gas hourly space velocity (GHSV) of 177,000h-1. 0.8%Cu/Ti2NbOx showed well activity while traditional commercial VWTi catalyst deactivated after 2%K2O doping. Water vapor or SO2 would not pose any negative effect on the SCR activity while the catalytic performance showed a slightly reversible inhibition with water vapor and SO2 existing in the simulated gas stream simultaneously. Also, 0.8%Cu/Ti2NbOx had an excellent hydrothermal stability after the process of hydrothermal aging with 10%H2O, 5%O2 and N2 as balance for 7h at 800oC.The activity characterization indicated 0.8%Cu/Ti2NbOx was a promising candidate for the NH3-SCR catalyst in the future practical application.

Teaching Interests: An array of analytical techniques (HRTEM, XRD, LRS, XPS, EPR, in-situ DRIFTS etc.) were employed to elucidate the correlations among the “performance – structure – property” and the reaction mechanism over 0.8%Cu/Ti2NbOx catalyst. The introduction of niobium oxide increased the surface area of TiO2 and decreased the crystallite size, promoting the high dispersion of copper species. Meanwhile, the total acidity and the amount of surface active oxygen over the catalyst were increased by the addition of niobium oxide. Copper species mainly existing in the state of isolated Cu2+ and non-isolated Cu+ enhanced the redox capability of the catalyst and the highest ratio of isolated Cu2+/copper species resulted in an excellent catalytic performance of 0.8%Cu/Ti2NbOx. The promotional synergistic effect of copper and niobium in 0.8%Cu/Ti2NbOx catalyst gave rise to a better NH3-SCR performance. Furthermore, the reaction pathway over 0.8%Cu/Ti2NbOx catalyst followed both Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism at 225oC. Both coordinated NH3 and ionic NH4+ were active intermediates and monodentate nitrates, bidentate nitrates and bridging nitrates were involved in the reaction over 0.8%Cu/Ti2NbOx catalyst at the reaction temperature of 225oC.