SO2-promoted reduction of NO with NH3 over vanadium molecularly anchored on the surface of carbon nanotubes

Being a major poison, SO2 is often avoided for selective catalytic reduction (SCR) of NO with ammonia at low temperatures. In the present work, we report a V2O5/CNT catalyst with high NO catalytic activities tolerant to SO2, moreover, whose SCR activity is promoted by the SO2 at proper low temperatures. When the reacting temperature is higher than 200 °C, SO2 improves the SCR activity, while it is lower than 200 °C, SO2 deactivates the V2O5/CNT catalysts. It seems that the reacting temperature behaves like a switch, capable of turning on and off the poisoning reactions. Furthermore, the promoting effect of SO2 exhibits a magnified tendency with decreasing V2O5 loadings. TEM and EDS results indicate that the vanadium oxides should molecularly anchor on the surface of CNTs. X-ray photoelectron spectroscopy, ammonia temperature-programmed desorption, temperature-programmed decomposition and temperature-programmed surface reaction results show that the promoting effect of SO2 on SCR activity originates from the formation of sulfate species on the catalyst surface. Based on these findings, a promoting process is also proposed. More importantly, the V2O5/CNTs catalysts show a great stability under the SO2-containing conditions after being operated for 100 h.