Three-way catalysis with supported gold catalysts: Poisoning effects of hydrocarbons
Three-way catalysis with supported gold catalysts: Poisoning effects of hydrocarbons
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DOI：
10.1016/j.apcatb.2018.06.063
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发表时间：
2018-12
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影响因子：
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通讯作者：
V. Ulrich;Christian Froese;B. Moroz;P. Pyrjaev;E. Gerasimov;I. Sinev;B. Cuenya;M. Muhler;V. Bukhtiyarov;W. Grünert
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作者：
V. Ulrich;Christian Froese;B. Moroz;P. Pyrjaev;E. Gerasimov;I. Sinev;B. Cuenya;M. Muhler;V. Bukhtiyarov;W. Grünert
最近在负载型 Au 催化剂上转化三元催化模型原料（CO、NO 丙烯、O2、无水或有水）期间观察到的中毒现象 [V. Ulrich等人，应用催化B 203 (2017) 572]通过反应研究（在模型进料中用丙烷代替丙烯，研究没有和有相关附加组分的CO氧化）、沉积物的程序升温氧化（TG、TPO）、研究自再生现象以及不同条件下CO吸附和CO与丙烯的共吸附的漂移。在其他成分存在的情况下，一氧化碳氧化过程中，观察到两种不同的中毒现象。在丙烷、丙烯和/或 NO 存在的情况下，CO 氧化在低于 370K 的温度下比 Au 在 Al2O3 或 La 稳定的 Al2O3 上受到显着抑制，但在 Au/CeZrOx 上则不然，其中活性在任何地方都相对较低。关于 CO 和丙烯（共）吸附的 DRIFTS 数据表明，这种中毒不仅是共吸附物位点阻塞的结果，而且电子从共吸附物向活性位点的转移（假设位于带有载体的带正电的金簇的周边）可能另外淬灭了反应。在较高温度下，含丙烯混合物中会产生不同的中毒机制。根据 TPO、TG 和 DRIFTS 的研究，我们得出结论，碳质残留物的形成，然而，碳质残留物不会阻挡 CO 吸附位点，而是阻挡金簇周围的支撑表面。虽然这会抑制涉及活性支持氧的 CO 氧化，但相同的氧物质可能会在更高的温度下燃烧沉积物。这导致自我再生现象，具体取决于载体的氧化还原活性、温度和进料中的丙烯含量。在瞬时实验中，观察到丙烯形成焦炭的中间体最有利于还原 NO。然而，在静止条件下，主要通过 CO 实现的 NO 还原仍然不足。
Poisoning phenomena recently observed during the conversion of three-way catalysis model feed (CO, NO propene, O2, without or with water) over supported Au catalysts [V. Ulrich et al., Applied Catalysis B 203 (2017) 572] were investigated by reaction studies (replacing propene by propane in model feed, study of CO oxidation without and with relevant additional components), by temperature-programmed oxidation of deposits (TG, TPO), by studying self-regeneration phenomena and by DRIFTS of CO adsorption and co-adsorption of CO and propene under different conditions. During CO oxidation in the presence of other components, two different poisoning phenomena were observed. In the presence of propane, propene, and/or NO, CO oxidation was significantly inhibited below 370 K over Au on Al2O3or on La-stabilized Al2O3, but not on Au/CeZrOxwhere activity was relatively low anywhere. DRIFTS data on (co-)adsorption of CO and propene suggest that this poisoning is not merely a result of site blocking by the coadsorbate, but that electron transfer from the co-adsorbates towards the active sites, which are assumed to be at the perimeter of positively charged Au clusters with the support, might have additionally quenched the reaction. At higher temperatures, a different poisoning mechanism operates in propene-containing mixtures. From studies by TPO, TG, and DRIFTS, we conclude the formation of carbonaceous residues, which do not block, however, CO adsorption sites but the support surface around Au clusters instead. While this inhibits CO oxidation involving active support oxygen, the same oxygen species might combust the deposits at higher temperatures. This results in self-regeneration phenomena depending on the redox activity of the support, the temperature and the propene content in the feed. In transient experiments, it was observed that NO is most favorably reduced by intermediates of coke formation from propene. Under stationary conditions, however, NO reduction, mostly by CO, remains insufficient.