硫酸化改性对TiO_(2)负载的铈基脱硝催化剂的活性及抗碱金属性能的影响

Effect of sulfation on the activity and alkali resistance of TiO_(2)-supported cerium-based deNO_(x) catalysts

采用浸渍法对TiO_(2)负载的铈基催化剂进行了硫酸化改性,同时制备了未经硫酸化改性的催化剂与之对比,通过X射线衍射(XRD)、比表面积测试(BET)、氢气程序升温还原(H_(2)-TPR)、X射线光电子能谱(XPS)和吡啶红外光谱(Py-IR)等一系列手段对催化剂进行了表征。结果表明,硫酸化改性不仅能够增加催化剂表面的化学吸附氧的含量,提高催化剂的氧化还原性,而且还能极大地丰富催化剂表面的布朗斯特酸位点和路易斯酸位点,以此来增加催化剂的酸性,使得催化剂的低温活性有所提升并拓宽其温度窗口。此外,硫酸化改性为铈基催化剂表面增加了额外的超强酸位点,使催化剂在受到碱金属的毒害后,仍有大量的酸位能得以保留,能够维持对NH3的吸附,进行催化反应循环,极大地提升催化剂的抗碱金属性能。

TiO_(2)-supported cerium-based catalysts have been modified by sulfation using the impregnation method, and their properties were compared with those of the unmodified catalysts. The catalysts were characterized by means of X-ray diffraction(XRD), specific surface area measurements(BET), hydrogen temperature-programmed reduction(H_(2)-TPR), X-ray photoelectron spectroscopy(XPS) and pyridine infrared spectroscopy(Py-IR). The results showed that sulfation not only increases the content of chemisorbed oxygen on the catalyst surface and improves the redox activity of the catalyst, but also greatly increases the number of Br?nsted acid sites and Lewis acid sites on the catalyst surface. The resulting increase in the acidity of the catalyst improves its low temperature activity and broadens its temperature window. In addition, extra super acid sites were generated on the surface of the cerium-based catalysts after sulfation. A significant proportion of these acid sites were retained after the catalyst was poisoned by alkali metals, allowing the adsorption of NH3 and the catalytic reaction to continue, thus improving the alkali metal resistance of the catalyst.