This work extends our previous investigation of nitrogen-methane atmospheric glow discharge for the simulation of chemical processes in prebiotic atmospheres. Also reactions on surfaces of solid state bodies can be important. So in presented experiments the electrodes with different shapes and different surface areas were used. Exhaust products of discharge in this gas mixture were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS) and Gas Chromatography - Flame Ionization Detector (GC-FID). The major products identified in chromatograms were hydrogen cyanide and acetylene

Krcma, F.

Manduchová, I.

Mazankova, V.

Prokes, L.

Trunec, D.

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

doi:10.14311/ppt.2018.3.103Plasma Physics and Technology 5(3):103–106, 2018 © Department of Physics, FEE CTU in Prague, 2018GC-MS AND GC-FID ANALYSIS OF PRODUCTS FROM GLOWDISCHARGE IN N2 + CH4 MIXTUREV. Mazánkováa,∗, I. Manduchováb, F. Krčmab, L. Prokešc, D. Trunecca Faculty of Military Technology, University of Defense, Kounicova 65, 662 10 Brno, Czech Republicb Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 612 00 Brno, Czech Republicc Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic∗ vera.mazankova@unob.czAbstract. This work extends our previous investigation of nitrogen-methane atmospheric glowdischarge for the simulation of chemical processes in prebiotic atmospheres. Beside the volume chemicalreactions also heterogeneous chemical reactions on surfaces of solid state bodies can be important. Soin presented experiments the electrodes with different shapes and different surface areas were used.Exhaust products of discharge in this gas mixture were analyzed by Gas Chromatography - MassSpectrometry (GC-MS) and Gas Chromatography - Flame Ionization Detector (GC-FID). The majorproducts identified in chromatograms were hydrogen cyanide and acetylene.Keywords: prebiotic atmosphere, GC-MS, GC-FID, glow discharge.1. IntroductionThe effect of an electric discharge on gas mixtures ofmethane (CH4) and nitrogen (N2) has been shown toresult in the synthesis of many different biologicallyimportant organic compounds including ammonia. Ithas been also shown that ammonia can be producedin discharges at atmospheric pressure [1] and it isassumed that ammonia can be created by reactionson surfaces [2]. The electrical discharges are believedto imitate the effect of thunderstorm lightning onchemical processes in prebiotic atmospheres. Indeedthe Miller-Urey spark discharge experiments in theearly 1950s [3, 4] were the first experimental studiesdescribing results in reducing atmospheres and ledto the start of laboratory studies of the origins ofprebiotic material on the Earth. The atmosphericpressure glow discharges are of significant interest fora wide range of applications such as pollution control,material processing or surface treatment. The glidingarc configuration has been shown to be a good mimicof processes in the prebiotic atmospheres being usedto replicate physical and chemical processes e.g. onmoon Titan. Titan is the largest moon in Saturn’s lu-nar system and the only one with a dense atmosphere,with atmospheric surface pressure of approximately1.5 × 105 Pa [5]. It is the only lunar body with asignificant quantities of CH4 and N2 in its atmosphere[6, 7]. The chemical composition of the Titan’s atmo-sphere is favorable for formation of complex moleculescontaining C, N and H. The solar ultraviolet radia-tion and electrons from Saturn’s magnetosphere areresponsible for the generation of primary radicals andother neutral species, which initiate chains of chem-ical reactions that finally result in the formation ofvarious organic molecules in the Titan atmosphere.This makes Titan as planetary-scale laboratory forthe synthesis of complex organic molecules [8]. Thepresent work is focused on the experimental study ofgaseous products produced in the atmospheric pres-sure glow discharge fed by N2+CH4 gas mixtures withCH4 concentrations in the range from 1% to 5%. Alsothe influence of surface processes was studied, namelytwo types of electrodes were used. The first oneswere electrodes in standard gliding-arc configurationwith large surface area. The second ones were theelectrodes made of wires.2. Experimental setupThe experimental setup schematic drawing is shownin Figure 1. The special high vacuum stainless steel re-actor was constructed for our experiments to preventany oxygen contamination during the experiments.Nitrogen and methane flows were automatically con-trolled by Bronkhorst controllers. The measurementswere carried out at total gas flows 100 sccm at at-mospheric pressure and laboratory temperature. Thedischarge electrode system had two configurations: i)configuration of the gliding arc discharge (see Figure1), ii) two wires with diameter of 2 mm. Both types ofelectrodes were made of copper. The wire electrodeswere fixed in one line and the distance of their tipswas 2 mm. The discharge was formed in the stableabnormal glow regime, and plasma occurred betweenthe electrodes at their shortest distance of 2 mm inthe form of a plasma channel of 1 mm in its diameter.The reactor chamber volume was 0.5 l. The dischargewas supplied by a DC stabilized HV source. Dischargebreakdown voltage was 1500 V, a stable plasma chan-nel was operating at 400 V at current in range 15 mAto 40 mA during all presented experiments. The mea-surements were performed for different N2:CH4 ratiosin the range from 1 % to 5 % of methane in nitrogen103V. Mazanková, I. Manduchová, F. Krčma et al. Plasma Physics and TechnologyFigure 1. Experimental setup. 1- storage bottle of nitrogen, 2- storage bottle of methane, 3- storage bottle of oxygen,4- Bronkhorst controllers, 5- reactor body, 6- electrode system, 7- oscilloscope, 8- GC-MS, GC-FID, 9- exhaust.(both gases having quoted purities of 99.995 %). Theexhaust gas was analyzed by GC-MS and GC-FIDmethods.Before starting the experiments, the discharge cham-ber was pumped down by oil rotary vacuum pumpto 1 Pa for 1 h and then was filled with the inves-tigated gas mixture up to the pressure of 101 kPa.Atmospheric pressure during the experiments wasmaintained by a slight pumping through the needlevalve.GC-MS analysis was carried out using an FisionsInstruments 8060 gas chromatograph. Separation wasperformed on a Polar plot Q-HT + 2PT column (25 mlength, 0.32 mm internal diameter) using helium flowof 2 sccm as the carrier gas. The GC oven temperaturewas held for 3.3 min at 50◦C and then increased withthe step of 15◦C min−1 to 250◦C, whereas the finaltemperature was held for 3 min.3. ResultsA typical GC-MS chromatogram showing the prod-ucts formed in the nitrogen discharge fed by 5% ofCH4 is shown in Figure 2. Similar spectra were alsoobserved for other N2:CH4 ratios. Hydrogen cyanide(HCN) was found to be the most abundant product atthe retention time 9 min. The second major productwas acetylene (C2H2). Other detected compounds aresigned in spectrum. These products were recognizedin all investigated gas mixtures, they were also de-tected in previous experiments [9]. The intensitiesshown in the following graphs were calculated as thearea bellow corresponding peaks. These intensitiesare proportional to the product concentrations. Thedependence of C2H2 concentration on CH4 addition isshown in Figure 3. The C2H2 concentration increaseswith increasing methane concentration as was alreadyobserved in previous experiments [9]. The MS andFID detection methods provide the same results. Alsothere is no significant difference of acetylene concentra-tion between both types of electrodes. So the surfacereactions are not important for acetylene creation.The same features were observed for HCN, see Figure4. The decrease of HCN concentration at 4% of CH4 isprobably caused by carbon (graphite) deposit on thetip of the wire electrodes. This deposit was observedduring the experiments and it could changed the dis-charge properties. The dependencies of C2H2 andHCN concentrations on discharge current are shownin Figures 5 and 6. There is no clear increasingdependence of products concentrations on dischargecurrent as in previous study [1]. This is probablycaused again by thick graphite deposit which was cre-ated on electrode surfaces. Such thick deposit wasobserved when copper electrodes were used, substan-tially thinner graphite deposit was observed when thestainless steel electrodes were used [10].Finally, the influence of oxygen addition to N2+CH4mixture was studied. The oxygen content was changedfrom 1% to 3%. The water molecules were observed inGC-MS chromatograms in this case, no other oxygencontaining molecules were observed. The concentra-tions of hydrocarbons and nitriles decrease with in-creasing oxygen content. So the oxygen has oppositeinfluence then carbon dioxide, the addition of car-bon dioxide leads to concentration increase of majorproducts [1].4. ConclusionsThe concentrations of major products (acetylene andhydrogen cyanide) from DC glow discharge in nitrogenmethane mixture were measured by GC-MS and GC-FID methods. It was found using electrodes with104vol. 5 no. 3/2018 Analysis of products from discharge in N2 + CH4 mixtureFigure 2. GC-MS spectrum of the gas-phase products from the discharge of 5% of CH4 in N2 for discharge current30 mA.Figure 3. The dependence of C2H2 concentration onCH4 addition. FID 1 and MS 1 are the results fromexperiments with gliding-arc electrodes configuration,FID 2 and MS 2 are the results from experiments withwire electrodes.different surface area that the surface reactions arenot important for productions of these two products.The use of copper as a electrode material leads to largeamount of carbon deposited on electrode surfaces.AcknowledgementsThe research was performed within the collaboration ofthe COST Actions CM 1401 and TD 1308. The researchwas supported by Czech Ministry of Education, Youth andSports, projects No. LO1411 (NPU I).Figure 4. The dependence of HCN concentration onCH4 addition. FID 1 and MS 1 are the results fromexperiments with gliding-arc electrodes configuration,FID 2 and MS 2 are the results from experiments withwire electrodes.References[1] V. Mazankova, L. Torokova, F. Krcma, N. J. Mason,and S. Matejcik. The influence of CO2 admixtures onthe product composition in a nitrogen-methaneatmospheric glow discharge used as a prebioticatmosphere mimic. Origins Life Evol B, 46(4):499–506,2016. doi:10.1007/s11084-016-9504-3.[2] G. Horvath, N. J. Mason, L. Polachova, M. Zahoran,L. Moravsky, and S. Matejcik. Packed bed DBDdischarge experiments in admixtures of N2 and CH4.Plasma Chem Plasma P, 30(5):565–577, 2010.doi:10.1007/s11090-010-9241-8.105V. Mazanková, I. Manduchová, F. Krčma et al. Plasma Physics and TechnologyFigure 5. The dependence of C2H2 concentration ondischarge current. The results are from experimentswith gliding-arc electrodes configuration.Figure 6. The dependence of HCN concentration ondischarge current. The results are from experimentswith gliding-arc electrodes configuration.[3] S. L. Miler. A production of amino acids under possibleprimitive Earth conditions. Science, 117(3046):528–529,1953. doi:10.1126/science.117.3046.528.[4] S. L. Miler and C. H. Urey. Organic compoundsynthesis on the primitive Earth. Science, 130(3370):245–251, 1959. doi:10.1126/science.130.3370.245.[5] M. Fulchignoni and et al. In situ measurements of thephysical characteristics of Titan’s environment. Nature,438(7069):785–791, 2005. doi:10.1038/nature04314.[6] A. Coustenis, D. Jennings, C. Nixon, R. Achterberg,P. Lavvas, S. Vinatier, N. Teanby, G. Bjoraker,R. Carlson, L. Piani, G. Bampasidis, F. Flasar, andP. Romani. Titan trace gaseous composition from CIRSat the end of the Cassini-Huygens prime mission.Icarus, 207:461–476, 2010.doi:10.1016/j.icarus.2009.11.027.[7] S. Horst and M. Tolbert. The effect of carbonmonoxide on planetary haze formation. Astrophys J,781(53), 2014. doi:10.1088/0004-637X/781/1/53.[8] F. Raulin, C. Brasse, O. Poch, and P. Coll.Prebiotic-like chemistry on Titan. Chem Soc Rev,41:5380–5393, 2012. doi:10.1039/C2CS35014A.[9] L. Torokova, J. Watson, F. Krcma, V. Mazankova,N. Mason, G. Horvath, and S. Matejcik. Gaschromatography analysis of discharge products inN2-CH4 gas mixture at atmospheric pressure: study ofmimic Titan’s atmosphere. Contrib Plasma Phys,55:470–480, 2015. doi:10.1002/ctpp.201400052.[10] V. Mazankova, L. Torokova, D. Trunec, F. Krcma,S. Matejcik, and N. J. Mason. Diagnostic ofnitrogen-methane atmospheric glow discharge used for amimic of prebiotic atmosphere. Plasma Phys Technol,4(1):83–86, 2017. doi:10.14311/ppt.2017.1.83.106

GC-MS and GC-FID Analysis of Products from Glow Discharge in N2 + CH4 Mixture

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GC-MS and GC-FID Analysis of Products from Glow Discharge in N2 + CH4 Mixture

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