Bjerregaard Joachim D, Han Joonsoo, Creaser Derek, Olsson Louise, Grönbeck Henrik
Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
Chemical Engineering and Competence Centre for Catalysis, Chalmers University of Technology, SE 412 96 Göteborg, Sweden.
J Phys Chem C Nanomater Interfaces. 2024 Mar 8;128(11):4525-4534. doi: 10.1021/acs.jpcc.3c07998. eCollection 2024 Mar 21.
Temperature-programmed reduction and oxidation are used to obtain information on the presence and abundance of different species in complex catalytic materials. The interpretation of the temperature-programmed reaction profiles is, however, often challenging. One example is H temperature-programmed reduction (H-TPR) of Cu-chabazite (Cu-CHA), which is a material used for ammonia assisted selective catalytic reduction of NO (NH-SCR). The TPR profiles of Cu-CHA consist generally of three main peaks. A peak at 220 °C is commonly assigned to ZCuOH, whereas peaks at 360 and 500 °C generally are assigned to ZCu, where Z represents an Al site. Here, we analyze H-TPR over Cu-CHA by density functional theory calculations, microkinetic modeling, and TPR measurements of samples pretreated to have a dominant Cu species. We find that H can react with Cu ions in oxidation state +2, whereas adsorption on Cu ions in +1 is endothermic. Kinetic modeling of the TPR profiles suggests that the 220 °C peak can be assigned to ZCuOCu and ZCuOH, whereas the peaks at higher temperatures can be assigned to paired ZCu and ZCuHOOHCu species (360 °C) or paired ZCu and ZCuOOCu (500 °C). The results are in good agreement with the experiments and facilitate the interpretation of future TPR experiments.
程序升温还原和氧化用于获取有关复杂催化材料中不同物种的存在和丰度的信息。然而，对程序升温反应曲线的解释通常具有挑战性。一个例子是铜菱沸石（Cu-CHA）的氢程序升温还原（H-TPR），Cu-CHA是一种用于氨辅助选择性催化还原NO（NH-SCR）的材料。Cu-CHA的TPR曲线通常由三个主要峰组成。220°C处的峰通常归属于ZCuOH，而360°C和500°C处的峰通常归属于ZCu，其中Z代表铝位点。在此，我们通过密度泛函理论计算、微观动力学建模以及对预处理以具有主要铜物种的样品进行TPR测量，来分析Cu-CHA上的H-TPR。我们发现H可以与氧化态为+2的铜离子反应，而在+1价铜离子上的吸附是吸热的。TPR曲线的动力学建模表明，220°C处的峰可归属于ZCuOCu和ZCuOH，而较高温度处的峰可归属于成对的ZCu和ZCuHOOHCu物种（360°C）或成对的ZCu和ZCuOOCu（500°C）。结果与实验结果吻合良好，有助于对未来TPR实验的解释。
