Silicotungstic acid modified Ce‐Fe‐O x catalyst for selective catalytic reduction of NO x with NH 3 : Effect of the amount of HSiW

Ce(SO4)2/α-Fe2O3 selective catalytic reduction of NOx with NH3: preparation, characterization, and performance

To achieve a low-cost, high-activity denitrification catalyst with excellent water and sulfur resistance, goethite and Ce(SO₄)₂·4H₂O were used to prepare Ce(SO₄)₂/α-Fe₂O₃ composite catalyst by the impregnation way and investigated the effect of Ce(SO₄)₂ on the properties of goethite. Ce(SO₄)₂/α-Fe₂O₃ with various preparation conditions for denitration was systematically discussed, and its structure and properties were characterized by XRD, BET, TEM, XPS, H₂-TPR, and NH₃-TPD methods. The results showed that Ce(SO₄)₂/α-Fe₂O₃ over the Ce/Fe molar ratio of 0.02 and calcination temperature of 350 ℃ had excellent catalytic activity, resistance to sulfur, and water properties and stability. When NO_x initial concentration was 500 ppm, gas hourly space velocity was 36,000 h^-1 and its reaction temperature was 300 ℃; the NO_x conversion efficiency was maintained at over 95% along with 300 ppm SO₂ and nearly 100% couple with 10% H₂O. Its superior performance was mainly attributed to the enhancement of the surface adsorbed oxygen and acidity of α-Fe₂O₃ by cerium sulfate. The multiple advantages of Ce_0.02/α-Fe₂O₃(350) made it feasible for practical engineering application.

Silicotungstic acid modified CeO2 catalyst with high stability for the catalytic combustion of chlorobenzene

The catalysts' redox capacity and surface acidity was important during the catalytic combustion of chlorobenzene (CB). CeO₂ showed great attractiveness due to its high oxygen storage capacity. Furthermore, the increase of acidity on the catalyst surface could improve the resistance to the chlorine poisoning. In this work, the silicotungstic (HSiW) modified CeO₂ catalysts prepared by four cerium salts and exhibited the different morphologies and catalytic activity. The HSiW modified CeO₂ catalyst prepared by Ce(CH₃COO)₃ (Cat-A) exhibited the best catalytic activity due to its abundant surface weak acid sites, more Ce³⁺ species and surface adsorption oxygen. The HSiW mainly located on the CeO₂ (111) planes of the Cat-A, which was conducive to redox property of CeO₂, thus promoting the deep oxidation of CB. Meanwhile the redox ability together with the weak acidity influenced the catalytic efficiency at low temperature. And the redox ability played a major role at high temperature. In addition, the Cat-A still possessed high stability and water resistance and maintained high activity after continuous catalytic oxidation of CB at 235 and 295 °C for 100h, exhibiting the possibility of industrial application.