Specialized nanotubular MnOx-CeO2/TiO2 composite catalysts for simultaneous low-temperature elimination of nitric oxide and ortho-dichlorobenzene

Abstract

Novel TiO₂-supported MnO_x-CeO₂ nanotubular catalysts (denoted as MnCe/Ti-NTs) were engineered for the simultaneous catalytic oxidation of ortho-dichlorobenzene (o-DCBz, CBCO) and selective catalytic reduction of NO with ammonia (NH₃-SCR). The catalyst with optimized Mn/Ti (0.30) and Ce/Ti (0.10) molar ratios exhibits superior catalytic performance for both the CBCO and NH₃-SCR reactions, achieving >90 % conversion efficiencies for both pollutants within the range of 275–360 °C. This outstanding performance originates from the well-balanced surface acidity and redox properties of the Mn_0.30Ce_0.10/Ti-NTs catalyst. Notably, this catalyst exhibits remarkable reaction selectivity and strong resistance to CBCO interference, with NH₃-SCR preferentially proceeding. Moreover, CBCO modulates the redox properties of the catalyst and suppresses the non-selective oxidation of NH₃ above 300 °C, which enhances the high-temperature deNO_x reaction. Although competitive adsorption between NH₃-SCR and CBCO for surface reactive oxygen species raises the T_{90 %} for o-DCBz conversion from 225 °C to 275 °C and slightly reduces the CO₂ selectivity, the H protons generated from NH₃ activation promote the dichlorination of o-DCBz and then remove the Cl atom in the form of HCl. To optimize the simultaneous low-temperature catalytic removal of o-DCBz and NO, further enriching the MnCe/Ti-NTs catalyst with surface reactive oxygen species is crucial. These findings provide both theoretical insights and practical guidance for designing dual-functional catalysts for the simultaneous catalytic removal of chlorinated volatile organic compounds (CVOCs) and NO_x at low temperatures.