In Situ Fourier Transform Infrared (FTIR) Study of Nonthermal-Plasma-Assisted Methane Oxidative Conversion

• Published in: Industrial & engineering chemistry research Vol. 46; no. 11; pp. 3486 - 3496
• Main Authors: Nair, S. A, Nozaki, Tomohiro, Okazaki, Ken
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 23-05-2007
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; Reactors; Methane; Oxidation; Non thermal plasma; In situ
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie0606688

Nonthermal plasma-assisted methane conversion has been widely investigated as a potential low-temperature process. The desired end objective is synthesis gas production, one-step production of liquid oxygenates, or coupling products. Either oxygen or steam or both is used as a second reactant or reactants, to provide additional O atoms and initiate plasma-assisted radical processing. The present paper intends to investigate the various possible products/reactive species that are formed during plasma processing. In situ Fourier transform infrared (FTIR) absorption spectrometry is used to monitor the products/reactive groups. Experiments are performed at room temperature and at low energy inputs (50 kJ/(mol CH4)) in a gas mixture of CH4/O2/N2/H2O (atmospheric humidity). In the absence of oxygen, alkane, alkene, and alkyne groups are formed as the products, which indicates termination reactions. With increasing oxygen concentration (11, 15, and 33%) a gradual shift from alkane to a −CHO group is observed. In addition, alcohol group formation is detected with oxygen input, which indicates coupling between the CH4 dissociation products and the O radicals as a primary step. The effect of higher energy input and the presence of catalytic surfaces such as platinum also are investigated.