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首页> 外文期刊>RSC Advances >Investigation of the hydrothermal aging of an Mn-based mullite SmMn2O5 catalyst of NO oxidation
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Investigation of the hydrothermal aging of an Mn-based mullite SmMn2O5 catalyst of NO oxidation

机译：锰基莫来石SmMn 2 O 5 NO氧化催化剂的水热老化研究

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Hydrothermal aging tests are important to carry out when evaluating the hydrothermal durability of heterogeneous catalysts in vehicle exhaust emission. Here, we explored the effect of aging on an efficient Mn-based mullite catalyst (SmMn2O5) of NO oxidation. The mullite catalyst was prepared via the hydrothermal method and was subsequently aged in air with a 10% H2O stream at 750 °C for 16 hours. The fresh and aged catalysts were structurally characterized using Powder X-ray diffraction(XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), high resolution-transmission electron microscope (HR-TEM), Brunauer–Emmett–Teller (BET) and temperature programmed desorption (TPD). For the performance evaluations, the samples were placed into a U-shape reactor furnace, and NO and NO2 concentrations were in situ recorded with an NOx analyzer. In contrast to fresh mullite, the aged sample showed a 25 °C higher light-off temperature and 11% conversion loss at its maximum conversion temperature of 300 °C. O2-TPD of the aged sample displayed a large decrease of the desorption area, consistent with an ～3-fold loss of the BET specific surface area. Moreover, HRTEM, XPS and Raman spectroscopy results together indicated that a small portion of the mullite decomposed into perovskite SmMnO3 and Mn2O3, which further reduced the total quantity of Mn active sites. The reduction of the BET surface area and mullite decomposition together caused the decrease of the catalytic performance. We therefore expect maintaining the specific surface area to be important for preventing the loss of catalytic performance during the hydrothermal aging process.
机译：在评估汽车尾气排放中非均相催化剂的水热耐久性时，进行水热老化测试非常重要。在这里，我们探索了老化对高效锰基莫来石催化剂（SmMn 2 O 5 ）的影响。没有氧化。莫来石催化剂通过水热法制备，随后在空气中以10％H 2 O气流在750°C下老化16小时。使用粉末X射线衍射（XRD），拉曼光谱，X射线光电子能谱（XPS），扫描电子显微镜（SEM），高分辨率透射电子显微镜（HR-TEM），Brunauer– Emmett–Teller（BET）和程序升温脱附（TPD）。为了进行性能评估，将样品放入U型反应炉中，并用原位记录 的NO和NO 2 浓度。没有 x 分析器。与新鲜的莫来石相比，老化的样品在最高转换温度为300°C时，起燃温度高25°C，转换损失为11％。老化样品的O 2 -TPD显示解吸面积大大减小，与BET比表面积损失约3倍相一致。此外，HRTEM，XPS和拉曼光谱结果表明，莫来石中的一小部分分解为钙钛矿SmMnO 3 和Mn 2 O 3 ，进一步减少了Mn活性位点的总量。 BET表面积的减少和莫来石的分解一起导致催化性能的降低。因此，我们期望保持比表面积对于防止在水热老化过程中催化性能的损失很重要。

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