Infrared studies of gas phase and surface processes of the enhancement of catalytic methane decomposition by low temperature plasma
Infrared studies of gas phase and surface processes of the enhancement of catalytic methane decomposition by low temperature plasma
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DOI：
10.1088/1361-6463/ab0c66
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发表时间：
2019-05-29
影响因子：
3.4
通讯作者：
Oehrlein, G. S.
中科院分区：
文献类型：
--
作者：
Knoll, A. J.;Zhang, S.;Oehrlein, G. S.
常压等离子体增强催化剂是一个新出现的研究领域，它体现了一个复杂的活性物种系统及其与表面的相互作用。在这项工作中，我们使用常压等离子体射流结合镍的Al_2O_3/SiO_2载体催化剂材料，分解甲烷气体的部分氧化反应。我们使用傅里叶变换红外光谱分析反应后的气相，测量甲烷的损失和CO、CO2和H2O的生成，并用漫反射傅立叶变换红外光谱(DRIFTS)原位分析催化剂表面随催化剂温度和等离子体操作参数的变化。我们发现，单独使用等离子体，单独使用催化剂，甲烷的还原作用都会增加，同时使用等离子体和催化剂时，甲烷的还原作用会增加。CO的产生似乎主要是由于等离子体源，因为它只出现在2.5W的等离子体耗散功率以上，并且随着催化剂温度的升高而减少。在高温下使用催化剂可以提高CO2的产量，而H2O的产量取决于等离子体功率和温度。利用漂移法，我们发现加热和等离子体处理都去除了催化剂表面的吸附水分。然而，单独的等离子体处理会导致CO的形成和1590 cm(-1)处的另一个红外光谱特征，这可能归因于连接到催化剂表面的羧酸基。这些物种表现出一种等离子体处理制度，其中它们在表面形成，并从催化剂表面显着去除。我们看到在995厘米(-1)处形成了一个新的光谱特征，并讨论了这个特征的行为和可能的起源。这项研究突出了催化剂材料的等离子体再生潜力，以及在低温等离子体处理下催化性能的增强。
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 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. 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.