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Catalytic Oxidation of NO over MnOx–CeO2 and MnOx–TiO2 Catalysts

机译:MnOx–CeO2和MnOx–TiO2催化剂上NO的催化氧化

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摘要

A series of MnOx–CeO2 and MnOx–TiO2 catalysts were prepared by a homogeneous precipitation method and their catalytic activities for the NO oxidation in the absence or presence of SO2 were evaluated. Results show that the optimal molar ratio of Mn/Ce and Mn/Ti are 0.7 and 0.5, respectively. The MnOx–CeO2 catalyst exhibits higher catalytic activity and better resistance to SO2 poisoning than the MnOx–TiO2 catalyst. On the basis of Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and scanning transmission electron microscope with mapping (STEM-mapping) analyses, it is seen that the MnOx–CeO2 catalyst possesses higher BET surface area and better dispersion of MnOx over the catalyst than MnOx–TiO2 catalyst. X-ray photoelectron spectroscopy (XPS) measurements reveal that MnOx–CeO2 catalyst provides the abundance of Mn3+ and more surface adsorbed oxygen, and SO2 might be preferentially adsorbed to the surface of CeO2 to form sulfate species, which provides a protection of MnOx active sites from being poisoned. In contrast, MnOx active sites over the MnOx–TiO2 catalyst are easily and quickly sulfated, leading to rapid deactivation of the catalyst for NO oxidation. Furthermore, temperature programmed desorption with NO and O2 (NO + O2-TPD) and in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS) characterizations results show that the MnOx–CeO2 catalyst displays much stronger ability to adsorb NOx than the MnOx–TiO2 catalyst, especially after SO2 poisoning.
机译:通过均相沉淀法制备了一系列MnOx–CeO2和MnOx–TiO2催化剂,并评估了它们在不存在或存在SO2的情况下对NO氧化的催化活性。结果表明,Mn / Ce和Mn / Ti的最佳摩尔比分别为0.7和0.5。 MnOx–CeO2催化剂比MnOx–TiO2催化剂具有更高的催化活性和更好的抗SO2中毒性。在Brunauer-Emmett-Teller(BET),X射线衍射(XRD)和具有标测的扫描透射电子显微镜(STEM映射)的基础上,可以看出MnOx-CeO2催化剂具有较高的BET表面积和MnOx在催化剂上的分散性优于MnOx-TiO2催化剂。 X射线光电子能谱(XPS)测量表明,MnOx–CeO 2 催化剂可提供大量的Mn 3 + 和更多的表面吸附氧,SO 2 < / sub>可能会优先吸附到CeO 2 的表面形成硫酸盐,从而保护MnO x 活性位点免受中毒。相反,MnO x –TiO 2 催化剂上的MnO x 活性位点容易被快速硫酸化,从而导致催化剂快速失活。不氧化。此外,使用NO和O 2 (NO + O 2 -TPD)进行程序升温脱附以及原位漫反射红外光谱(原位DRIFTS)表征表明, MnO x –CeO 2 催化剂显示的吸附NO x 的能力比MnO x -TiO > 2 催化剂,尤其是在SO 2 中毒之后。

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