Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects
Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects
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DOI：
10.1016/j.cattod.2014.10.027
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发表时间：
2015-05
期刊：
影响因子：
5.3
通讯作者：
K. Ralphs;Sarayute Chansai;C. Hardacre;R. Burch;S. Taylor;S. James
中科院分区：
文献类型：
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作者：
K. Ralphs;Sarayute Chansai;C. Hardacre;R. Burch;S. Taylor;S. James
机械化学法制备的Ag/Al_2O_3催化剂用于烃类选择性催化还原NO_x的反应中，与湿法浸渍法制备的Ag/Al_2O_3催化剂相比，其活性显著提高。考察了不同球磨实验参数对材料结构和催化剂活性的影响，确定了最佳球磨条件。在高速球磨条件下，发现γ-氧化铝相转变为α-氧化铝相，导致催化剂活性降低。在较低的研磨速度下，取决于研磨时间，可以观察到氧化铝载体的破裂和附聚。然而，由于球磨，与常规制备的催化剂相比，观察到所有催化剂的NOx还原活性的普遍增强，与所使用的还原剂无关。通过瞬态DRIFTS-MS实验研究了H2在无水和有水条件下对球磨法和湿浸渍法制备的催化剂上SCR反应的影响，原位DRIFTS-MS分析表明气相和表面物种均存在显著差异.最值得注意的是，在机械化学制备的催化剂的情况下，异氰酸酯物质形成得明显更快并且表面浓度更高。
Mechanochemical preparation of Ag/Al2O3catalysts used for the selective catalytic reduction of NOxusing hydrocarbons has been shown to substantially increase the activity of the catalyst in comparison with Ag/Al2O3prepared by wet impregnation. The effect of using different ball-milling experimental parameters on both the structure of the material as well as the catalyst activity has been investigated and the optimum conditions established. A phase transition from γ- to α-alumina was observed milling at high speeds which was found to result in lower catalyst activities. At lower milling speeds both fracturing and agglomeration of the alumina support can be observed depending on the grinding time. However, due to ball-milling, a general enhancement in the NOxreduction activity was observed for all catalysts compared with the conventionally prepared catalysts irrespective of the reductant used. Transient DRIFTS-MS experiments were performed to investigate the effect of H2in the absence and presence of water on the SCR reaction over catalysts prepared by both ball milling and wet impregnation.In-situDRIFTS-MS analysis revealed significant differences in both gas phase and surface species. Most notably, isocyanate species were formed significantly more quickly and at higher surface concentration in the case of the mechanochemically prepared catalyst.