The influencing mechanism of NH3 and NOx addition on the catalytic oxidation of toluene over Mn2Cu1Al1Ox catalyst

As important precursors of PM2.5 and ozone, the simultaneous removal of VOCs and NOx by catalytic oxidation and NH3-SCR has attracted more and more attention. Exploring the effect of NH3-SCR on toluene oxidation is important for guiding the design of dual-function catalysts, but lacks unified understanding currently. In this work, the role of Mn3-yCuyAl1Ox mixed oxides from layered double hydroxide (LDH) precursors in the simultaneous removal of toluene and NOx was reported. The obtained Mn2Cu1Al1Ox can achieve a close to 80% toluene conversion and a 62% NOx conversion at 250 °C. The catalyst has more Lewis acid sites and oxygen vacancies, and the synergistic effect between Cu and Mn promotes electron transfer, which leads to a certain ability to simultaneously removal toluene and NOx. But compared to toluene oxidation without NH3 and NOx, the inhibitory effect of NH3-SCR reactants was found over Mn2Cu1Al1Ox. The inactive nitrate formed by NOx oxidation below 200 °C was deposited on the catalyst surface. The results also presented that there was obvious competitive adsorption between toluene and NH3; and by-products such as acetonitrile were easily formed by NH3 and toluene oxidation intermediates to deposit on the catalyst surface, which affect the deep oxidation of toluene and reduces the CO2 yield.