Rationally engineered ReO -CuSO4/TiO2 catalyst with superior NH3-SCO efficiency and remarkably boosted SO2 tolerance: Synergy of acid sites and surface adsorbed oxygen

Ammonia (NH3) is a critical component causing environmental problems like haze and water pollution. Selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O is a promising method to abate NH3 emission. However, inferior SO2 tolerance is still a tremendous challenge to be conquered for present NH3-SCO catalysts regarding practical applications. Application of materials which was difficult to be sulfated by SO2 should be an effective way to solve this problem. Here, a ReOx-CuSO4/TiO2 catalyst which coupled the advantages of ReOx (Rhenium oxides, supplying highly active adsorbed surface oxygen enhancing NH3-SCO reaction) and CuSO4 (providing Brønsted acid sites inhibiting the formation of N2O) was rationally fabricated. Results indicated that ReOx-CuSO4/TiO2 catalyst exhibited excellent catalytic performance in NH3-SCO with almost 100% of NH3 oxidized at 300 °C (N2 selectivity as high as 96%). Crucially, the composite catalyst exhibited incredible activity and stability under harsh reaction conditions toward SO2 (600 ppm) and H2O (4.0 vol%) owing to the superior inhibition capability for SO2 adsorption. In situ DRIFTS, in situ Raman and in situ XPS demonstrated that the NH3-SCO reaction over ReOx-CuSO4/TiO2 catalyst mainly obeyed a N2H4 reaction mechanism and oxidation–reduction circle between Re7+ and Re6+ played a vital role. Moreover, SO2 would not affect this reaction mechanism on ReOx-CuSO4/TiO2 catalyst. The knowledge and understanding reported could provide critical insights for the design and optimization of efficient materials for industrial NH3 oxidative elimination.