通过等离子体诊断揭示介孔二氧化硅SBA-15上等离子体氨合成过程中出现的不同状态
Unraveling the different regimes arisen during plasma ammonia synthesis on mesoporous silica SBA-15 through plasma diagnostics
摘要：
在这里，我们证明了介孔二氧化硅SBA-15和SBA-15-Ag浸渍等离子体氨合成过程中的性能取决于等离子体条件。在高功率下，不含Ag的介孔二氧化硅SBA-15产生在我们的实验中观察到的最大量的氨，但是添加Ag在较低功率下提供了较小的益处。使用N2、N2+和NH分子带和Hα线的光学发射光谱分析等离子体条件。对SBA-15的光发射谱，特别是Ha线和N2分子谱带数据的分析表明，SBA-15具有更高的电子密度和更高的N2振动温度。相对于中性N2，更强的N2+发射为SBA-15填充床反应器中更高的电子密度提供了额外的证据。Ag的加入导致原子氢的浓度较低。其中Ag充当氢汇，促进与氮的表面反应。光谱中NH的存在可指示SBA-15反应器中较高的H浓度。从材料的角度来看，SBA-15是一种更耐用的催化剂，由于金属在结构中时没有产生局部加热，因此在等离子体暴露后具有值得称赞的表面积保持率。
英文摘要：
Herein we demonstrate that the performance of mesoporous silica SBA-15 and SBA-15-Ag impregnated during plasma ammonia synthesis depend on the plasma conditions. At high power the mesoporous silica SBA-15 without Ag produces the largest amount of ammonia observed in our experiments, but the addition of Ag provides a minor benefit at lower powers. Plasma conditions were analyzed using optical emission spectroscopy using N2, N2+ and NH molecular bands and Hα lines. The analysis of optical emission, specifically Ha lines and N2 molecular bands data shows that SBA-15 has higher electron density, and higher N2 vibrational temperature. Stronger N2+ emission relative to the neutral N2 provides additional evidence for higher electron density in the SBA-15 packed bed reactors. The addition of Ag resulted in a lower concentration of atomic hydrogen. Where Ag acts as a hydrogen sink facilitating surface reactions with nitrogen. The presence NH in the spectrum may indicate a higher concentration of H in the SBA-15 reactor. From the materials point of view SBA-15 is a more robust catalyst with a commendable surface area retention after plasma exposure due to the lack of local heating generated when a metal is in the structure.
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