The deposition of VWOx on the CuCeOy microflower for the selective catalytic reduction of NOx with NH3 at low temperatures

Abstract NOx emissions are a major environmental problem, and the selective catalytic reduction (SCR) is the most effective method to convert NOx in flue gas into harmless N2 and H2O. In this work, a new carrier, CuCeOy microflower assembled from a large number of copper-cerium mixed oxide nanosheets, is firstly developed to load vanadium-tungsten mixed oxides (VWOx) for the SCR of NOx with NH3. The resultant optimal VWOx/CuCeOy catalyst exhibits significantly enhanced low-temperature de-NOx performance with the NOx conversion of 60% at 180 °C, over 90% from 240 °C to 390 °C under the gas hourly space velocity (GHSV) of 36,000 h−1. The reason can be mainly attributed the fact that the transfer of electrons among Ce, Cu and V ions is very easy to occur via the following equations Ce3++Cu2+ ↔ Ce4++Cu+, V5+ + Cu+ ↔ V4+ + Cu2+, V4+ + Ce4+ ↔ V5+ + Ce3+, which effectively decreases the apparent activation energy (Ea = 16.59 kJ/mol) of NH3-SCR de-NOx reaction. In addition, the enhanced reducibility and a large number of Bronsted acid sites also contribute the low-temperature de-NOx performance. Both Eley-Rideal and Langmuir-Hinshelwood mechanisms are included in the NH3-SCR de-NOx reaction over the VWOx/CuCeOy catalyst.