Interaction Mechanism for Simultaneous Elimination of Nitrogen Oxides and Toluene over the Bifunctional CeO 2 -TiO 2 Mixed Oxide Catalyst.

Simultaneous catalytic elimination of nitrogen oxides (NO x , x = 1 and 2) and volatile organic compounds (VOCs) is of great importance for environmental preservation in China. In this work, the interactions of simultaneous removal of NO x and methylbenzene (PhCH 3 ) were investigated on a CeO 2 -TiO 2 mixed oxide catalyst, which demonstrated excellent bifunctional removal efficiencies for the two pollutants. The results indicated that NO x positively promotes PhCH 3 oxidation, while NH 3 negatively inhibits through competitive adsorption with PhCH 3 . The underlying mechanism is that a pseudo PhCH 3 -SCR reaction happened in this process is parallel to NH 3 -SCR. Combined with in situ diffuse reflectance infrared Fourier transform spectroscopy and quasi in situ X-ray photoelectron spectroscopy, the interaction mechanism between NO x and PhCH 3 is proposed. Specifically, NO x is adsorbed on the catalyst surface to produce nitrate species, which reacts with the carboxylate generated during PhCH 3 oxidation to form organic nitrogen intermediates that create N 2 and CO 2 in the following reactions. In the reaction process, the superoxide (O 2 - ) generated by O 2 activation on the catalyst surface is an important species for the propelling of oxidation reaction. This work could provide guidelines for the design of state-of-the-art catalysts for simultaneous catalytic removal of NO x and VOCs.