1. Identifying Regimes During Plasma Catalytic Ammonia Synthesis.
- Author
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Gershman, Sophia, Fetsch, Henry, Gorky, Fnu, and Carreon, Maria L.
- Subjects
NITROGEN plasmas ,MESOPOROUS materials ,PLASMA density ,EMISSION spectroscopy ,METAL catalysts ,ELECTRON density ,AMMONIA ,MESOPOROUS silica - Abstract
Herein, we demonstrate that the performance of mesoporous silica SBA-15 and SBA-15-Ag during plasma ammonia synthesis depends on the plasma conditions. At high power, the mesoporous silica SBA-15 without Ag produces the largest amount of ammonia, but the addition of Ag provides a minor benefit at lower powers. Plasma conditions were analyzed through optical emission spectroscopy using N
2 , N2 + , and NH molecular bands and Hα line. Stark broadening of Hα line was used to find electron density, and N2 molecular bands were used to assess N2 vibrational excitation, important for plasma nitrogen decomposition. At similar input conditions, reactors with SBA-15 have higher electron density and higher N2 vibrational temperature. Consistent with higher electron density, SBA-15 reactors have stronger N2 + emission intensity relative to the neutral N2 . The addition of Ag results in higher N2 rotational temperature, possibly due to localized heating. From the materials point of view, SBA-15 is a more robust catalyst with good surface area retention after plasma exposure due to the lack of local heating generated when a metal is in the structure. We identify two possible regimes during ammonia synthesis, a metal and a surface-plasma driven. At lower plasma densities, the addition of metal is beneficial, while at higher power and plasma density, the best performance is achieved without the aid of a metal catalyst. Mesoporous materials for Plasma Catalytic Ammonia Synthesis, at certain plasma conditions lead to different regimes, a plasma/surface and a metal dominated regimes of ammonia production. [ABSTRACT FROM AUTHOR]- Published
- 2022
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