Al2O3-based passive NOx adsorbers for low temperature applications
Al2O3-based passive NOx adsorbers for low temperature applications
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DOI：
10.1016/j.apcatb.2015.01.025
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发表时间：
2015-07-01
影响因子：
22.1
通讯作者：
Crocker, Mark
中科院分区：
文献类型：
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作者：
Ji, Yaying;Bai, Shuli;Crocker, Mark
通过微反应器和原位DRIFTS实验，研究了Pt/Al2O3和Pt/La-Al2O3在80-160℃温度范围内对NOx的存储，以确定它们作为被动NOx吸附剂的适用性。在Al2O3中加入1 wt%的La，产生了新的NOx存储位点，提高了NOx存储效率。然而，根据TPD测量，Pt/La-Al2O3在250℃以下的NOx脱附效率略低于Pt/Al2O3。在重复的NOx吸附-解吸循环中，由于无法在250℃下再生与La相关的强NOx储存位点，在5个循环后，几乎没有观察到添加La的好处。DRIFTS测量表明，在NOx- tpd过程中，亚硝酸盐和弱结合硝酸盐最初从Pt/Al2O3和Pt/La-Al2O3表面去除。高温（bb0 ~ 250℃）下的NOx脱附主要与硝酸盐分解有关。对Pt/Al2O3的DRIFTS测量表明，当氧化Pt存在时，NOx主要存储在Al2O3表面，尽管当还原性再处理应用于还原Pt位点时，NOx存储在还原Pt位点上变得显著，并且总NOx存储效率得到提高。然而，与裸Al2O3相比，Pt存在时，250℃以下的NOx脱附效率显著下降，H-2预还原后的脱附效率更低。总体而言，未经预还原的Pt-Al在250℃以下显示出最高的NOx解吸量(C)。
NOx storage on Pt/Al2O3 and Pt/La-Al2O3 in the temperature range 80-160 degrees C was investigated by means of microreactor and in situ DRIFTS experiments, to ascertain their suitability for passive NOx adsorber applications. Addition of 1 wt% La to Al2O3 resulted in the creation of new NOx storage sites and improved NOx storage efficiency. However, according to TPD measurements, Pt/La-Al2O3 exhibited slightly lower NOx desorption efficiency below 250 degrees C than Pt/Al2O3. During repeated NOx adsorption-desorption cycles, almost no benefit of La addition was observed after five cycles, due to the inability to regenerate the strong NOx storage sites associated with the La at 250 degrees C. DRIFTS measurements indicated that during NOx-TPD, nitrites and weakly bound nitrate species were initially temoved from the surface of Pt/Al2O3 and Pt/La-Al2O3. NOx desorption at higher temperatures (>250 degrees C) was mainly associated with nitrate decomposition. DRIFTS measurements on Pt/Al2O3 revealed that NOx was mainly stored on the Al2O3 surface when oxidized Pt was present, although when a reductive re-treatment was applied NOx storage on reduced Pt sites became significant and total NOx storage efficiency was improved. However, compared to bare Al2O3, NOx desorption efficiency below 250 degrees C significantly dropped when Pt was present, and was even lower after pre-reduction in H-2. Overall, the Pt-Al without pre-reduction showed the highest amount of NOx desorption below 250 degrees C. (C) 2015 Elsevier B.V. All rights reserved.