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Increasing the production volume of organic synthesis products demands improvements to the technology of the pyrolysis process to reduce costs and increase the yield of desired products, particu-larly ethylene, which is the dominant raw material in the petrochemical industry.
The aim of the present work is the substantiation of the methods that increase the pyrolysis selectivity for ethylene by influencing the stages of the radical chain process.
Based on the study of the relative reactivity of the various C–H bonds in their interaction with the methyl radicals and with hydrogen atoms, which are the basic particles that determine the chain propagation in the pyrolysis, the possibility of increasing the process selectivity for ethylene was established, while simulta-neously reducing the yield of the condensation products and suppressing the formation of pyrolytic carbon by replacing the methyl radical with hydrogen atoms, which was made possible by adding hydrogen to the feedstock in the amount of approximately 2% by weight.
It was found that allene lowers the activation energy of the thermal decomposition of hydrocarbons, thus increasing the depth of the reaction. Accelerating the rate of initiation of the radical chain process was observed at the temperatures below 1,000 K. This opens up the possibility of increasing the effi-ciency of the pyrolysis process by recycling the propane fraction containing allene into the pyrolysis feedstock. This speeds up the process at low temperatures and suppresses the yield of the condensa-tion products. Experimental data demonstrating the results of application of the proposed method are presented.
allene, chain propagation stage, hydrogen, initiating stage, process selectivity, pyrolysis, yield of ethylene.
[1] Lewandowski, W.M., Radziemska, E., Ryms, M. & Ostrowski, P., Modern methods of thermochemical biomass conversion into gas, liquid and solid fuels. Ecological Chem-istry and Engineering, 18(1), pp. 39–47, 2011.
[2] Grigiante, M., Ischia, M., Baratieri, M., Maschio, R.D. & Ragazzi, M., Pyrolysis analy-sis and solid residue stabilization of polymers, waste tyres, spruce sawdust and sewage sludge. Waste and Biomass Valorization, 1(4), pp. 381–393, 2010. http://dx.doi.org/10.1007/s12649-010-9038-2
[3] Wang, X.Q., Xie, C.G., Li, Z.T. & Zhu, G.Q. Catalytic processes for light olefin produc-tion (Chapter 5). Practical Advances in Petroleum Processing, eds. C.S. Hsu & P.R. Rob-inson, Springer Science – Business Media, Inc.: New York, Vol. 1, pp. 149–168, 2006.
[4] Global Ethylene Market Outlook: Low Cost Feedstocks Fuel The Next Wave Of Invest-ments In North America and China. Inaugural Ethylene Forum Online www.media. corporate-ir.net/media_files/IROL/11/110877/05_Global_Ethylene_Market_Outlook_ Eramo.pdf
[5] Korzun, N.V. & Magaril, R.Z., Thermal Processes of Refining, [in Russian], KDU: Moscow, pp. 10–20, 2008.
[6] Kondratiev, V.N., Rate Constants of Gas Phase Reactions, National Bureau of Stan-dards: Washington, 1972.
[7] Emanuel, N.M. & Knorre, D.G., Chemical Kinetics; Homogeneous Reactions, Wiley: New York, 1973.
[8] Vedeneyev, V.I., Gurvich, L.V., Kondratyev, V.N., Medvedev, V.A. & Frankevich Ye. L., Bond Energies, Ionization Potentials, and Electron Affinities, St. Martin’s Press, Inc.: New York, 1966.
[9] Magaril, E. & Magaril R, Increasing the selectivity of the hydrocarbon feedstock pyrolysis. WIT Transactions on Ecology and the Environment, 186, pp. 529–534, 2014. http://dx.doi.org/10.2495/ESUS140461
[10] Magaril, R.Z., Theoretical foundation of the chemical processes of oil refining, [in Russian], KDU: Moscow, p. 69, 2010.
[11] Klementyev, A., Magaril, R., Korzun, N. & Magaril, E., Efficiency improvement of py-rolysis. WIT Transactions on Ecology and the Environment, 190(2), pp. 861–865, 2014. http://dx.doi.org/10.2495/EQ140802