Toluene Unexpectedly Promotes Low-Temperature NOx Reduction by Inducing Peroxide Oxygen on Ce-Ti Catalysts.

Abstract

Volatile organic compounds (VOCs) are widely considered to inhibit NH3-SCR by competing with NH3 for surface sites and blocking redox centers, yet industrial flue gases frequently contain both VOCs and NOx. Here we show that toluene unexpectedly promotes low-temperature DeNOx over Ce-Ti catalysts, with the hollow nanotube-structured CeTiNTs exhibiting outstanding performance, achieving >90% conversion of both NOx and toluene at 200 °C with high CO2 selectivity and near-unity N2 selectivity. Mechanistically, toluene acts as an electron donor to surface Ce sites, increasing the Ce3+ fraction and oxygen-vacancy-associated adsorbed oxygen. In situ near-ambient-pressure XPS and Raman spectroscopy reveal the toluene-triggered formation of surface peroxide (O22-), which accelerates NO oxidation to NO2 and thus initiates the fast-SCR pathway, while simultaneously enabling deep oxidation of toluene. Density functional theory corroborates preferential adsorption of toluene on Ce sites and reduced oxygen-vacancy formation energies at specific lattice positions. These results establish a reaction-coupling route in which toluene exhibits dual effects, involving competitive adsorption that partially inhibits certain NH3-SCR steps, while predominantly promoting low-temperature fast-SCR via peroxide-enabled NO oxidation through enhanced oxygen activation, offering a mechanistic basis for rational catalyst design for multipollutant abatement.

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