Synergetic Effects of Plasma, Temperature and Diluant on Nonoxidative Conversion of Methane to C2+ Hydrocarbons in a Dielectric Barrier Discharge Reactor

Document Type: Research Article

Authors

1 Catalysis and Reaction Engineering Laboratory, Department of Chemical Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, I.R. IRAN

2 Catalysis and Reaction Engineering Laboratory, Department of Chemical Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, I.R. IRAN

3 Department of Electrical & Computer Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, I.R. IRAN

Abstract

Noncatalytic and nonoxidative conversion of methane in a dielectric barrier discharge (DBD) reactor is examined at different temperatures, gas residence times and input powers. In addition, the ratio of methane to helium as a diluant, is changed in the range of 0.6 to 1.8. Results show significant synergetic effects of plasma, temperature and helium on the methane conversion and C2+ selectivities. C2 hydrocarbons are the main products (more than 70%) of the process, however, minor amounts of heavier hydrocarbons up to C8 are formed. At an input power of 230W and gas residence time of 6 sec, when the temperature increases from 100 to 200oC, the methane conversion enhances by 33%. In the temperature of 100-350oC, the methane conversion passes through a maximum at CH4 /He ratio of 1.0, at which the highest effect of the temperature is observed. In addition, at 350oC, when the input power increases from 140 to 230W, the CH4 conversion enhances from 20.3 to 27.0%. As the temperature increases from 100 to 350oC, the selectivity of ethane decreases from 81.5 to 73.0%, while the selectivities of ethylene and acetylene enhances by about 40% and 270%, respectively. The frequency of effective collisions among the reactants, excited helium (He*), and free electrons (e-) seems to increase with temperature, that in turn leads to higher methane conversions and changes in products selectivities.

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Main Subjects


[1] Lunsford, J.H., Catalytic conversion of methane to more useful chemicals and fuels: a challenge for the 21st century, Catal. Today, 63, 165 (2000).

[2] Fox, J.M., Catal. Rev. Sci. Eng., 35, 169, (1993).

[3] Parkyns, N.D., Warburton, C.I. and Wilson, J.D., Natural gas conversion to liquid fuels and chemicals: Where does it stand?, Catal. Today, 18, 385 (1993).

[4] Liu, C.J., Eliasson, B., Xue, B., Li, Y. and Wang, Y., React. Kinet. Catal. Lett., 74, 71 (2001).

[5] Mallinson, R. G., Sliepcevich, C. M., and Rusek, S., ‘‘Methane Partial Oxidation in Alternating Electric Fields,’’ Division of Fuel Chemsitry,Proc. Amer. Chem. Soc. Meeting, Vol. 32, No. 3, American. Chemical Society, San Francisco (1987).

[6] Bhatnager, R., and Mallinson, R. G., ‘‘The Partial Oxidation of Methane Under the Influence of an AC Electric Discharge,’’ Methane and Alkane Con-version Chemistry, Bhasin, M. M. and Slocum, D. N., eds., Plenum, New York, 249 (1995).

[7] Larkin, D. W., Caldwell, T. A., Lobban, L. L. and Mallinson, R. G., Oxygen Pathways and Carbon Dioxide Utilization in Methane Partial Oxidation in Ambient Temperature Electric Discharges, Energy & Fuels, 124, 740 (1998).

[8] Rosacha, L. A., Anderson, G. K., Bechtold, L. A., Coogan, J. J., Heck, H. G., Kang, M., McCulla, W.H., Tennant, R.A. and Watnuck, P.J., “Treatment of Hazardous Wastes Using Silent Discharge Plasmas”, Non-Thermal Plasma Technique for Pollution Control, Penetrante, B.M. and Schultheis, S.E., eds., NATO ASI Ser., Vol. G  34, Part B, Springer-Verlag, Berlin, Heidelberg (1993).

[9] Eliasson, B., Liu, C.J. and Kogelschatz, U., Direct Conversion of Methane and Carbon Dioxide to Higher Hydrocarbons Using Catalytic Dielectric-Barrier Discharges with Zeolites, Ind. Eng. Chem. Res., 39, 1221 (2000).

[10] Yao, S.L., Nakayama, A. and Suzuki, E., Methane conversion using a high-frequency pulsed plasma: Discharge features, AIChE J., 47, 419 (2001).

[11] Suib, S.L. and Zerger, R.P., A Direct, Continuous, Low-Power Catalytic Conversion of Methane to Higher Hydrocarbons via Microwave Plasmas, J. Catal., 139, 383 (1993).

[12] Liu C.J., Mallinson R., Lobban L., Comparative investigations on plasma catalytic methane conversion to higher hydrocarbons over zeolites, Appl. Catal. A, 178, 17 (1999).

[13] Yao, S.L., Ouyang, F., Nakayama, A., Suzuki, E., Okumoto, M. and Mizuno, A., Oxidative Coupling and Reforming of Methane with Carbon Dioxide Using a High-Frequency Pulsed Plasma, Energy & Fuels, 14, 910 (2000).

[14] Jeong,  H.K., Kim, S.C., Han, C., Lee, H., Song, H.K. and Na, B.K., Conversion of Methane to Higher Hydrocarbons in Pulsed DC Barrier Discharge at Atmospheric Pressure, Korean J. Chem. Eng., 18, 196 (2001).

[15] Kado, S., Sekine,  Y. and  Fujimoto,  K., Direct synthesis of acetylene from methane by direct current pulse discharge, Chem. Commun., 2485 (1999).

[16] Liu, C.J., Xue, B., Eliasson, B., He, F., Li, Y. and Xu, G.H., Methane Conversion to Higher Hydro-carbons in the Presence of Carbon Dioxide Using Dielectric-Barrier Discharge Plasmas, Plasma Chem. Plasma Processing, 21, 301 (2001).

[17] Tao Jiang , Yang Li , Chang-jun Liu , Gen-hui Xu, Baldur Eliasson , Bingzhang Xue, Plasma methane conversion using dielectric-barrier discharges with zeolite A, Catalysis Today, 72, 229 (2002).

[18] Thanyachotpaiboon,  K.,  Chavadej, S., Caldwell, T. A., Lobban, L.L. and Mallinson, R.G., Con-version of Methane to Higher Hydrocarbons in AC Nonequilibrium Plasmas, AIChE Journal, 44 (10), 2252, October (1998).

[19] Shuiliang, Y., Nakayama, A. and Suzuki, E., Methane conversion using  a high-frequency pulsed plasma: Important factors, AIChE Journal, 47 (2), 413 (2001).

[20] Shuiliang, Y., Nakayama, A. and Suzuki, E., Methane conversion using a high-frequency pulsed plasma: Discharge factors, AIChE Journal, 47 (2), 419 (2001).

[21] Yang, Y., Direct Non-oxidative methane conversion by non-thermal plasma: Experimental study, Plasma Chemistry and Plasma Processing, 23 (2), 283 (2003).

[22] Huang, J. and Suib, S.L., Dimerization of methane through microwave plasma, J. Phys. Chem., 97, 9403 (1993).

[23] Oumghar, A., Lerand, J.C., Diamy, A.M., Turillon, N. and Ben-Aim., A Kinetic of Methane Conversion By A Dinitrogen Microwave Plasma, Plasma Chemistry and Plasma Processing, 14 (3), p. 229 (1994).

[24]  Hsieh,  L. T., Lee, W. j., Chen, C.Y., Chang, M.B. and Chang, H.C., Converting Methane  By Using An RF Plasma Reactor, Plasma Chemistry and Plasma processing, 18 (2), p. 215 (1998).

[25] Yao, S., Nakayama, A. and Suzuki, E., Acetylene and hydrogen from pulsed plasma conversion of methane, Catalysis Today, 71, 219 (2001).

[26] Stephanie L. Brock, Manuel Marquez, z Steven L. Suib, y,1 Yuji Hayashi, and Hiroshige Matsumoto, Plasma Decomposition of CO2 in the Presence of Metal Catalysts, Journal of Catalysis, 180, 225 (1998).

[27] Bagheri-Tar, F., Khodadadi, A.A., Malekzadeh A. and Mohajerzadeh, S.S., Oxidative Coupling of Methane in a Negative DC Corona Reactor at Low Temperature, Can. J. Chem. Eng., 81 (1), 37 (2003).