Rationally engineered ReOx-CuSO4/TiO2 catalyst with superior NH3-SCO efficiency and remarkably boosted SO2 tolerance: Synergy of acid sites and surface adsorbed oxygen
Ammonia (NH 3 ) is a critical component causing environmental problems like haze and water pollution. Selective catalytic oxidation of ammonia (NH 3 -SCO) to N 2 and H 2 O is a promising method to abate NH 3 emission. However, inferior SO 2 tolerance is still a tremendous challenge to be conquered for present NH 3 -SCO catalysts regarding practical applications. Application of materials which was difficult to be sulfated by SO 2 should be an effective way to solve this problem. Here, a ReO x -CuSO 4 /TiO 2 catalyst which coupled the advantages of ReO x (Rhenium oxides, supplying highly active adsorbed surface oxygen enhancing NH 3 -SCO reaction) and CuSO 4 (providing Brønsted acid sites inhibiting the formation of N 2 O) was rationally fabricated. Results indicated that ReO x -CuSO 4 /TiO 2 catalyst exhibited excellent catalytic performance in NH 3 -SCO with almost 100% of NH 3 oxidized at 300 °C (N 2 selectivity as high as 96%). Crucially, the composite catalyst exhibited incredible activity and stability under harsh reaction conditions toward SO 2 (600 ppm) and H 2 O (4.0 vol%) owing to the superior inhibition capability for SO 2 adsorption. In situ DRIFTS, in situ Raman and in situ XPS demonstrated that the NH 3 -SCO reaction over ReO x -CuSO 4 /TiO 2 catalyst mainly obeyed a N 2 H 4 reaction mechanism and oxidation–reduction circle between Re 7+ and Re 6+ played a vital role. Moreover, SO 2 would not affect this reaction mechanism on ReO x -CuSO 4 /TiO 2 catalyst. The knowledge and understanding reported could provide critical insights for the design and optimization of efficient materials for industrial NH 3 oxidative elimination.
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