Mutual inhibition mechanism of simultaneous catalytic removal of NOx and toluene on Mn-based catalysts.

Abstract NOx and toluene have been identified as the dominant air pollutants in solid wasted combustion, and it is of great importance to remove these two pollutants simultaneously. Here, we found that Mn/CeO2 and Mn/TiO2 exhibited a bifunctional property in both NO reduction and toluene oxidation, and both of which could achieve 80% of conversion rate in NO reduction and toluene oxidation processes. However, the activity of both Mn/CeO2 and Mn/TiO2 decreased in simultaneous removal of NOx and toluene compared with separate NOx reduction and toluene oxidation. This indicates that there is a mutual inhibition between NOx reduction and toluene oxidation in simultaneous removal process over Mn-based catalysts, attributing to the competitive adsorption and utilization of active oxygen. In detail, the adsorption of toluene occupied the Lewis acid sites and restrained the NH3 adsorption. Meanwhile, the competitive utilization of active oxygen by NH3/NOx inhibited toluene oxidation to CO2 by active oxygen species as the reaction between NH3/NOx and active oxygen species would occur more easily.