Hydrothermal stability of MO_x-Ce_0.75Zr_0.25O₂ catalysts for NO_x reduction by ammonia

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• 作者：Min WANG ; Zhichun SI ; Lei CHEN ; Xiaodong WU ; Jun YU
• 关键词：Ce0.75Zr0.25O2 ; NH3-SCR ; acidic additives ; hydrothermal stability ; rare earths
• 刊名：Journal of Rare Earths
• 出版年：December, 2013
• 年：2013
• 卷：31
• 期：12
• 页码：1148-1156
• 全文大小：1968 K

文摘

Various acidic components (MO_x: phosphate, sulfate, tungstate and niobate) were loaded on Ce_0.75Zr_0.25O₂ powders by an impregnation method. The as-prepared catalysts were hydrothermally treated at 760 掳C for 48 h in air containing 10 vol.% H₂O to obtain the aged catalysts. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H₂ programmed-reduction, NH₃ adsorption and deNO_x activity measurements. The results showed that, among the catalysts investigated, the phosphated Ce_0.75Zr_0.25O₂ catalyst showed the highest hydrothermal stability. The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH₃-SCR activity of hydrothermally aged catalyst. Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high. The decomposition of sulfates at temperatures higher than 600 掳C restrained the usage of sulfated catalysts in high temperature conditions. The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb₂O₅-Ce_0.75Zr_0.25O₂ catalyst.