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

NO_x 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 NO_x and toluene compared with separate NO_x reduction and toluene oxidation. This indicates that there is a mutual inhibition between NO_x 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/NO_x inhibited toluene oxidation to CO₂ by active oxygen species as the reaction between NH₃/NO_x and active oxygen species would occur more easily.