1. Decomposition of methanol in a low-pressure DC glow discharge in nitrogen-oxygen mixture Ayako Katsumata 1, Kohki Satoh 1,2 and Hidenori Itoh 1 1 Department of electrical and Electric Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan 2 Center of Environmental Science and Disaster Mitigation for Advanced Research, Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan  Applied voltage ： DC (-295 ～ -323V)  Discharge current ： -2.5mA  The initial total pressure ： 66.7Pa  The initial partial pressure of methanol ： 13.3Pa  The initial gas mixture ratios of nitrogen to oxygen are changed from discharge to discharge as shown in a table. 1.Introduction 2.Experimental apparatus & conditions Background Objective Experimental apparatus  Electrodes Parallel-plate electrodes of 60mm diameter and 20mm separation. The lower electrode is earthed and a negative DC voltage is applied to the upper electrode to generated a glow discharge.  Discharge chamber 155mm inner diameter and 300mm height. Earthed.  Mass spectrometry Gas samples are extracted from the glow discharge through a 0.1mm diameter orifice fitted at the center of the lower electrode, and the mass spectra of the samples are obtained using a Quadrupole mass spectrometer (QMS).  Emission spectroscopy The optical emission of the glow discharge is measured by a Photonic Multi- Channel Analyzer (PMA).  Infrared spectroscopy A gas sample is extracted into a long-path optical cell immediately after the glow discharge is switched off, and an infrared absorption spectrum is obtained using a Fourier Transform Infrared Spectrophotometer (FTIR).  Electrical-energy Input electrical-energy (discharge current × applied voltage) to the glow discharge is measured every second. Conditions gas mixture ratios (N 2 ： O 2 ) Partial gas pressure [Pa] total pressure [Pa] methanolnitrogenoxygen 100:0 13.3 53.40 66.7 95: 550.72.7 90:1048.15.3 85:1545.48.0 80:2042.710.7 75:2540.113.3 3.Results & discussion Partial pressure variation of CH 3 OH, H 2, CO, CO 2, HCN, CH 4 and C 2 H 2 & ion current variation of H 2 O The yield and selectivity of CO X (CO or CO 2 ) [2] as a function of O 2 concentration CH 3 OH No significant difference is shown in the variations of methanol for the difference oxygen concentrations. Methanol decomposition is independent of oxygen additive. Principle products The variations of the gaseous products are considerably influenced by the oxygen concentration of the background gas.  H 2 The partial pressure of H 2 decreases when the oxygen concentration increases.  CO CO concentration peaks when the oxygen concentration is near 10 and 15%.  CO 2 The partial pressure of CO 2 increases when the oxygen concentration increases.  H 2 O The QMS ion-current of H 2 O increases when the oxygen concentration increases. Minor products HCN, CH 4 and C 2 H 2 are also detected as minor products. HCN, CH 4 and C 2 H 2 are found to be intermediate products, which are decomposed in a glow discharge. 4.Conclusions HCN CH 4 C2H2C2H2  The yield of CO X  The selectivity of CO X Where  H 2, CO, CO 2, HCN, CH 4, C 2 H 2 and H 2 O are gaseous products in a low-pressure DC glow discharge in nitrogen-oxygen-methanol mixture.  H 2, CO, CO 2 and H 2 O are principle products and HCN, CH 4 and C 2 H 2 are minor products.  Methanol is chiefly inverted to CO and CO 2 via intermediate products at low oxygen concentration (5%) and directly to CO and CO 2 at relatively high oxygen concentration (20%).  The Y CO peaks at the oxygen concentration of 15%, but the Y CO 2 increases monotonously and tends to saturate at that of approximately 20%.  The S CO decreases linearly and the S CO 2 increases linearly when the oxygen concentration increases.  Methanol is one of the most commonly used volatile organic compounds (VOCs) for adhesive, paint, degreasing, etc.  Due to the low toxicity of methanol, only the concentration has been controlled; however, the quantity also has been limited under the new regulation [1].  Gas-cleanup using discharge plasmas has recently attracted attentions because chemically active species and UV radiation, which can initiate or assist the decomposition of the hazardous gases like VOCs, are generated in the discharge plasmas.  To investigate gaseous products in a low-pressure DC glow discharge in nitrogen-oxygen- methanol mixture, and examined the influence of oxygen additive on the decomposition characteristics of methanol, to develop the plasma cleaning of exhaust gases containing methanol. [1] Government Amends Laws, Latest Amendment by Law, No. 56 of 2004 (Ministry of the Environment) Mass balance for C atoms CH 3 OH C 2 H 2 HCN CH 4 CO CO 2 Low O 2 Concentration High O 2 Concentration N 2 :O 2 =100:0 N 2 :O 2 =95:5N 2 :O 2 =80:20  The number of C atoms (in Pa) Concentration of methanol The number of C atoms in a methanol molecule(1) In methanol = × In a gaseous product = Concentration of a gaseous × The number of C atoms in a gaseous product(1 & 2)  Oxygen concentration At low oxygen concentration (N 2 : O 2 = 95 : 5), there is a tendency that methanol is chiefly inverted to CO and CO 2 via intermediate products. At high oxygen concentration (N 2 : O 2 = 80 : 20), methanol is directly inverted to CO and CO 2. CO and CO 2 increase with the oxygen concentration.  Namely, decomposition process can be shown as follows, [CO]:The partial pressure of CO [CO 2 ]:The partial pressure of CO 2 [CH 3 OH]:The partial pressure of methanol [CH 3 OH] 0 :The initial partial pressure of methanol We investigated gaseous products in a low-pressure DC glow discharge in nitrogen-oxygen-methanol mixture, and examined the influence of oxygen additive on the decomposition characteristics of methanol. The Y CO peaks at the oxygen concentration of 15%. The Y CO 2 increases monotonously and tends to saturate at the oxygen concentration of approximately 20%. Further, the S CO decreases linearly and the S CO 2 increases linearly when the oxygen concentration increases. [2] Hyun-Ha Kim, et al., Appl. Catal. B: Environ. 56 (2005) 213-220.  It is straightforward to examine the decomposition process of methanol in an atmospheric pressure discharge.  However, we selected the low-pressure DC glow discharge in order to clarify the products from methanol in detail because the low-pressure glow discharge is stable and the diagnostics of the discharge can be done easily, compared with that of the atmospheric-pressure discharge.