Promotional Effect of Zirconium Doping on the NH3‐SCR Activity of CeO2 and CeO2‐TA Modified by Thiourea: A Comparative Study

Selective catalytic reduction with ammonia (NH₃-SCR): Thiourea (TA) modification and Zr doping present a synergistic promotional effect on the NH₃-SCR activity of CeO₂ catalyst, and Ce_0.95Zr_0.05O _z -TA exhibits the best catalytic performance among all as-prepared catalysts. The influence of Zr doping on the physical-chemical properties of CeO₂ and CeO₂-TA catalysts are investigated.

Abstract

Zirconium (Zr) was doped to optimize the NH₃-SCR activity of both CeO₂ and thiourea modified CeO₂-TA catalysts for comparison. Different from the promotional influence of thiourea modification on the agglomeration of CeO₂, the transformation from nanoparticles to nanocubes and the formation of highly crystallized CeOSO₄, Zr doping lowers the agglomeration of nanoparticles, loosens the surface morphology of catalyst and promotes the formation of Ce-Zr solid solution. Furthermore, Zr doping exhibits a synergistic promotional effect of thiourea modification on the dispersion of Ce³⁺ and S⁶⁺ species on the surface of CeO₂, and increases the concentrations of the surface total oxygen and chemisorbed oxygen of CeO₂-TA. Interestingly, Zr doping instead decreases the promotional effect of thiourea modification on the high-temperature or medium/low-temperature reducibility of catalyst, but increases both Brønsted and Lewis acid sites of CeO₂-TA by inducing the highly dispersive sulfate species rather than the CeOSO₄ crystal, which might be crucial to the NH₃-SCR activity of Ce-based catalyst.

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