Infrared studies of gas phase and surface processes of the enhancement of catalytic methane decomposition by low temperature plasma

• Published in: Journal of physics. D, Applied physics Applied physics, 2019-03, Vol.52 (22)
• Main Authors: Knoll, A. J., Zhang, S., Lai, M., Luan, P., Oehrlein, G. S.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; atmospheric pressure plasma; Plasma catalysis; plasma surface chemistry
• ISSN: 0022-3727; 1361-6463

Catalyst enhancement by atmospheric pressure plasma is a recently emerging field of research that embodies a complex system of reactive species and how they interact with surfaces. In this work we use an atmospheric pressure plasma jet integrated with a nickel on Al2O3/SiO2 support catalyst material to decompose methane gas by partial oxidation reaction. We use Fourier-transform Infrared spectroscopy (FTIR) analysis of the gas phase post reaction to measure the loss of methane and the production of CO, CO2, and H2O and diffuse reflectance Fourier-transform Infrared spectroscopy (DRIFTs) in situ analysis of the catalyst surface as a function of both catalyst temperature and plasma operating parameters. We find reduction of methane by both plasma alone, catalyst alone, and an increase when both plasma and catalyst were simultaneously used. The production of CO appears to be due primarily to the plasma source as it only appears above 2.5 W plasma dissipated power and decreases as catalyst temperature increases. CO2 production is enhanced by having the catalyst at high temperature and H2O production depends on both plasma power and temperature. Using DRIFTs we find that both heating and plasma treatment remove absorbed water on the surface of the catalyst. Plasma treatment alone however leads to the formation of CO and another IR spectral feature at 1590 cm-1, which may be attributed to carboxylate groups, bonded to the catalyst surface. These species exhibit a regime of plasma treatment where they are formed on the surface and where they are significantly removed from the catalyst surface. We see the formation of a new spectral feature at 995 cm-1 and discuss the behavior and possible origins of this feature. Furthermore, this research highlights the potential for plasma regeneration of catalyst materials as well as showing enhancement of the catalytic behavior under low temperature plasma treatment.