Free radical models of small molecular alkane pyrolysis

doi:10.11949/j.issn.0438-1157.20161578

Abstract

Abstract:

Besides short reaction time, large variety and low concentrations of free radicals in alkane pyrolysis, interactions between different free radicals, which were produced by various raw materials, and between main streams and free radicals, which were produced near high temperature wall zone and stagnant residence time under high reaction depth, can spontaneously alter reaction paths and affect product distribution. Therefore, it is very difficult to study pyrolysis mechanism of hydrocarbons by experimental methods. Through integration of Materials Studio and Aspen Plus software, free radical mechanism of single hydrocarbon pyrolysis by molecular simulation techniques was studied. Research methodologies from initial free-radical mechanism of ethane pyrolysis, interaction mechanism of ethane and propane mixture pyrolysis, data accuracy of reaction kinetics, and steric hindrance in n-hexane pyrolysis were also evaluated. The results show that numerical simulation method can get a better understanding of some mechanistic details than experimental method and the combination of experimental and simulation methods can eliminate various hypotheses in current kinetic models and improve model accuracy, which will provide a high-precision mechanism model for industrial production forecast.

Key words: ethylene, pyrolysis, free radical, reaction mechanism, simulation

摘要：

由于热裂解存在反应时间短、自由基数量多、浓度小，且不同原料产生的不同自由基之间、反应深度较大时管壁处于高温和停留时间所生成的不同自由基与主流体间的相互作用会随时改变反应路径，并影响到产物分布，因此造成了用实验方法研究单体烃热裂解反应机理的困难。将Materials Studio软件与Aspen Plus软件相结合来研究单体烃热裂解的自由基反应机理，并通过对乙烷热裂解一次反应机理、乙烷和丙烷混合热裂解相互作用机理、动力学数据准确性对比及正已烷空间位阻的影响，对研究方法进行了论述。结果表明，数值模拟的理论方法与实验方法相比，可以深入了解实验研究不可能达到的一些机理细节问题，如果将实验研究和模拟研究相结合，可避免目前动力学模型研究中的各种假设，提高机理模型研究的准确性，为工业生产预测提供高精度的机理模型。

关键词: 乙烯, 热裂解, 自由基, 反应机理, 模拟

CLC Number:

TQ21.211

ZHANG Hongmei, LIN Feng, REN Mingqi, LI Jinlian, HAO Yulan, WU Hongjun, ZHAO Jingying, ZHAO Liang, HE Yongdian. Free radical models of small molecular alkane pyrolysis[J]. CIESC Journal, 2017, 68(4): 1423-1433.

张红梅, 林枫, 任铭琪, 李金莲, 郝玉兰, 吴红军, 赵晶莹, 赵亮, 贺永殿. 小分子烃类蒸汽热裂解自由基机理模型研究方法的探讨[J]. 化工学报, 2017, 68(4): 1423-1433.

References 59

[1]	RICE F O. The thermal decomposition of organic compounds from the standpoint of free radicals(Ⅳ):The dehydrogenation of paraffin hydrocarbons and the strength of the C-C bond[J]. American Chemical Society, 1933, 55(10):4245-4247.
[2]	RICE F O. The thermal decomposition of organic compounds from the standpoint of free radicals (Ⅲ):The calculation of the products formed from paraffin hydrocarbons[J]. American Chemical Society, 1933, 55(1):3035-3040.
[3]	FREDDY E I, ROGER M M. The mechanism and rate parameters for the pyrolysis of n-hexane in the range 723-823 K[J]. International Journal of Chemical Kinetics, 1987, 19(2):81-103.
[4]	BILLAUD F, ELYAHYAOUI K, BARONNET F. Mechanistic modeling of the pyrolysis of n-hexane[J]. Journal of Analytical & Applied Pyrolysis, 1991, 19:29-40.
[5]	EBERT K H, EDERER H J, ISBARN G. The thermal decomposition of n-hexane[J]. International Journal of Chemical Kinetics, 1983, 15(5):475-502.
[6]	SABBE M K, GEEM K M V, REYNIERS M F, et al. First principle-based simulation of ethane steam cracking[J]. AIChE Journal, 2011, 57(2):482-496.
[7]	WANG K, SALDANA M H, VILLANO S M, et al. Improved kinetic model for ethane pyrolysis at high conversions[C]//ACS National Meeting. Boston, 2015.
[8]	WANG K, VILLANO S M, DEAN A M. Fundamentally-based kinetic model for propene pyrolysis[J]. Combustion & Flame, 2015, 162(12):4456-4470.
[9]	张兆斌, 李华, 张永刚, 等. 丁烷热裂解自由基反应模型的建立和验证[J]. 石油化工, 2007, 36(1):44-48.ZHANG Z B, LI H, ZHANG Y G, et al. Establishment and verification of free radical model for butane steam cracking[J]. Petrochemical Technology, 2007, 36(1):44-48.
[10]	WANG K, VILLANO S M, DEAN A M. Experimental and kinetic modeling study of butene isomer pyrolysis(Ⅰ):1-and 2-butene[J]. Combustion & Flame, 2016, 173:347-369.
[11]	WANG K, VILLANO S M, DEAN A M. Experimental and kinetic modeling study of butene isomer pyrolysis(Ⅱ):Isobutene[J]. Combustion & Flame, 2017, 176:23-37.
[12]	杜鸟锋, 甯红波, 李泽荣, 等. 1, 3-丁二烯热裂解的动力学计算与模型研究[J]. 物理化学学报, 2016, 32(2):453-464.DU N F, NING H B, LI Z R, et al. Kinetic calculation and modeling study of 1, 3-butadiene pyrolysis[J]. Acta Phys. -Chim. Sin., 2016, 32(2):453-464.
[13]	姬伟毅. 正戊烷热裂解自由基反应模型的研究[J]. 石油化工, 2012, 41(6):633-636.JI W Y. Radical reaction model for n-pentane pyrolysis[J]. Petrochemical Technology, 2012, 41(6):633-636.
[14]	张红梅, 姜维, 李金莲, 等. 乙烷热裂解自由基反应机理的综合数值模拟[J]. 化工科技, 2014, 22(2):20-23.ZHANG H M, JIANG W, LI J L, et al. Numerical simulation research on free radical reaction mechanism of ethane pyrolysis[J]. Science & Technology in Chemical Industry, 2012, 41(6):633-636.
[15]	张红梅, 顾萍萍, 张晗伟, 等. 丙烷热裂解反应机理的分子模拟[J]. 石油学报(石油加工), 2012, 28(6):986-990.ZHANG H M, GU P P, ZHAO H W, et al. Molecular simulation of propane pyrolysis reaction[J]. Acta Petrolei Sinica(Petroleum Processing Section), 2012, 28(6):986-990.
[16]	张红梅, 李青月, 李金莲, 等. 乙烷丙烷单独及混合裂解相互作用机理的模拟研究[J]. 化工科技, 2015, 23(1):9-13.ZHANG H M, LI Q Y, LI J L, et al. Numerical simulation on cracking mechanism of interaction of ethane, propane and their mixtures[J]. Science & Technology in Chemical Industry, 2015, 23(1):9-13.
[17]	李金莲, 张红梅, 李春秀, 等. 丙烷-正丁烷混合热裂解反应机理及相互作用机理的数值模拟[J]. 计算机与应用化学, 2016, 33(2):213-217.LI J L, ZHANG H M, LI C X, et al. Numerical simulation on reaction mechanism of pyrolysis of propane, n-butane and their mixture[J]. Computers and Applied Chemistry, 2016, 33(2):213-217.
[18]	郝玉兰, 张红梅, 张晗伟, 等. 丁烷热裂解反应机理的分子模拟[J]. 石油学报(石油加工), 2013, 29(5):824-829.HAO Y L, ZHANG H M, ZHANG H W, et al. Molecular simulation on pyrolysis mechanism of butane[J]. Acta Petrolei Sinica(Petroleum Processing Section), 2013, 29(5):824-829.
[19]	张红梅, 张晗伟, 顾萍萍, 等. 异丁烷热裂解反应机理的分子模拟[J]. 化工学报, 2012, 63(10):3138-3142.ZHANG H M, ZHANG H W, GU P P, et al. Molecular simulation research on pyrolysis mechanism of isobutane[J]. CIESC Journal, 2012, 63(10):3138-3142.
[20]	张红梅, 李春秀, 郝玉兰, 等. C4烷烃混合热裂解反应机理的数值模拟[J]. 化学工程, 2015, 43(5):73-78.ZHANG H M, LI C X, HAO Y L, et al. Numerical simulation on reaction mechanism of mixed pyrolysis of C4 alkanes[J]. Chemical Engineering(China), 2015, 43(5):73-78.
[21]	张红梅, 孙维, 李金莲, 等. 正戊烷热裂解一次反应机理的数值模拟[J]. 石油学报(石油加工), 2016, 32(2):394-400.ZHANG H M, SUN W, LI J L, et al. Molecular simulation on pyrolysis mechanism of n-pentane[J]. Acta Petrolei Sinica(Petroleum Processing Section), 2016, 32(2):394-400.
[22]	李青月. 正己烷热裂解一次自由基反应分子模拟及反应机理研究[D]. 大庆:东北石油大学, 2015.LI Q Y. Molecular simulation and reaction mechanism of free radical reactions mechanism of n-hexane thermal cracking[D]. Daqing:Northeast Petroleum University, 2015.
[23]	李金莲, 张红梅, 李春秀, 等. 1-丁烯热裂解反应机理的数值模拟[J]. 石油学报(石油加工), 2016, 32(5):1055-1061. LI J L, ZHANG H M, LI C X, et al. Numerical simulation on reaction mechanism of 1-butene pyrolysis[J]. Acta Petrolei Sinica(Petroleum Processing Section), 2016, 32(5):1055-1061.
[24]	HIRATO M, YOSHIOKA S. Pyrolysis of naphtha, kerosene, and gas oil by tubular reactor and its simulation model[J]. Sekiyu Gakkaishi, 1972, 15(10):818-824.
[25]	QUANN R J, JAFFE S B. Building useful models of complex reaction systems in petroleum refining[J]. Chemical Engineering Science, 1996, 51(10):1615-1631.
[26]	GUILLAUME D, VAKERY E, VERSTRAETE J J, et al. Single event kinetic modelling without explicit generation of large networks:application to hydrocracking of long paraffins[J]. Oil & Gas Science & Technology, 2011, 66(3):399-422.
[27]	BECKER P J, CELSE B, GUILLAUME D, et al. A continuous lumping model for hydrocracking on a zeolite catalysts:model development and parameter identification[J]. Fuel, 2016, 164:73-82.
[28]	BLANDING F H. Reaction rates in catalytic cracking of petroleum[J]. Industrial & Engineering Chemistry, 1953, 45(6):1186-1197.
[29]	WEI J, PRATER C D. The structure and analysis of complex reaction systems[J]. Advances in Catalysis, 1962, 13:203-392.
[30]	WEEKMAN V W. Optimum operation-regeneration cycles for fixed-bed catalytic cracking[J]. Industrial & Engineering Chemistry Process Design & Development, 1968, 7(2):252-256.
[31]	张红梅, 尹云华, 徐春明, 等. 大庆重石脑油蒸汽热裂解集总动力学模型[J]. 化工学报, 2009, 60(11):2743-2748.ZHANG H M, YIN Y H, XU C M, et al. Lumping kinetic model of Daqing naphtha pyrolysis[J]. CIESC Journal, 2009, 60(11):2743-2748.
[32]	PASHIKANTI K, LIU Y A. Predictive modeling of large-scale integrated refinery reaction and fractionation systems from plant data(Ⅱ):Fluid catalytic cracking (FCC) process[J]. Energy & Fuels, 2011, 25(11):5320-5344.
[33]	GAO H, WANG G, LI R, et al. Study on the catalytic cracking of heavy oil by proper cut for higher conversion and desirable products[J]. Energy & Fuels, 2012, 26(3):23275-84.
[34]	BECKER P J, CELSE B, GUILLAUME D, et al. Hydrotreatment modeling for a variety of VGO feedstocks:a continuous lumping approach[J]. Fuel, 2015, 139(139):133-143.
[35]	关国民, 王宗祥. 大庆石脑油裂解炉计算机控制模型[J]. 石油化工, 1990, (8):523-530.GUAN G M, WANG Z X. A computer-controlled model for Daqing naphtha cracking furnace[J]. Petrochemical Technology, 1990, (8):523-530.
[36]	CAMP C E V, DAMME P S V, WILLEMS P A, et al. Severity in the pyrolysis of petroleum fractions. Fundamentals and industrial application[J]. Ind. Eng. Chem. Process Des. Dev., 1985, 24(3):561-570.
[37]	熊国华, 郝红, 王烨, 等. 烃类热裂解的乙烯产率计算[J]. 化学反应工程与工艺, 1996, (2):161-165.XIONG G H, HAO H, WANG Y, et al. The calculation of ethylene yield by the thermal cracking of hydrocarbon[J]. Chemical Reaction Engineering & Technology, 1996, (2):161-165.
[38]	FRANK D J, SACKETT W M. Kinetic isotope effects in the thermal cracking of neopentane[J]. Geochimica et Cosmochimica Acta, 1969, 33(7):811-820.
[39]	WANG F, REN J, LI Y. Theoretical study on free radical model for n-hexane pyrolysis[J]. Computers & Applied Chemistry, 2009, 26(10):1243-1248.
[40]	KEYVANLOO K, SEDIGHI M, TOWFIGHI J. Genetic algorithm model development for prediction of main products in thermal cracking of naphtha:comparison with kinetic modeling[J]. Chemical Engineering Journal, 2012, 209(20):255-262.
[41]	ABBAS, DREA, NADIA, et al. Mechanism and kinetic of free radical reactions for propane using theoretical calculations[J]. J. Chem. Chem. Eng., 2012, 6(6):563-573.
[42]	CABALLERO D Y, BIEGLER L T, GUIRARDELLO R. Simulation and optimization of the ethane cracking process to produce ethylene[J]. Computer Aided Chemical Engineering, 2015, 37:917-922.
[43]	LI D, ZHAO Y. Understanding the chain mechanism of radical reactions in n-hexane pyrolysis[J]. Research on Chemical Intermediates, 2015, 41(6):3507-3529.
[44]	ZHAO Y, ZHANG S, LI D. Understanding the mechanism of radical reactions in 1-hexene pyrolysis[J]. Chemical Engineering Research & Design, 2014, 92(3):453-460.
[45]	吴指南. 基本有机化工工艺学(修订版)[M]. 北京:化学工业出版社, 1990:28-29.WU Z N. Basic Organic Chemical Technology(Revised Edition)[M]. Beijing:Chemical Industry Press, 1990:28-29.
[46]	DOMANCICH A O, PEREZ V, HOCH P M, et al. Systematic generation of a CAPE-OPEN compliant simulation module from GAMS and FORTRAN models[J]. Chemical Engineering Research & Design, 2010, 88(4):421-429.
[47]	ZAMOSTNY P, KARABA A, OLAHOVA N, et al. Generalized model of n-heptane pyrolysis and steam cracking kinetics based on automated reaction network generation[J]. Journal of Analytical & Applied Pyrolysis, 2014, 109:159-167.
[48]	王国清, 杜志国, 张利军, 等. 应用BP神经网络预测石脑油热裂解产物收率[J]. 石油化工, 2007, 36(7):699-704.WANG G Q, DU Z G, ZHANG L J, et al. Applying BP neural networks to predict product-yields of naphtha steam cracking[J]. Petrochemical Technology, 2007, 36(7):699-704.
[49]	MAIO F P D, LIGNOLA P G. KING, a kinetic network generator[J]. Chemical Engineering Science, 1992, 47(9/10/11):2713-2718.
[50]	KARABA A, ZAMOSTNY P, LEDERER J, et al. Generalized model of hydrocarbons pyrolysis using automated reactions network generation[J]. Industrial & Engineering Chemistry Research, 2013, 52(52):15407-15416.
[51]	ZAMOSTNY P, KARABA A, OLAHOVA N, et al. Generalized model of n-heptane pyrolysis and steam cracking kinetics based on automated reaction network generation[J]. Journal of Analytical & Applied Pyrolysis, 2014, 109:159-167.
[52]	VAN GEEM K. Single Event Microkinetic Model for Steam Cracking of Hydrocarbons[M]. MARIN G. Ghent:Ghent University, 2006:47-55.
[53]	VAN G K M, MARIE-FRANCOISE R, MARIN G B, et al. Automatic reaction network generation using RMG for steam cracking of n-hexane[J]. AIChE Journal, 2006, 52(2):718-730.
[54]	周丛, 李蔚, 张兆斌, 等. 正戊烷热裂解自由基反应网络自生成模型的研究[J]. 石油化工, 2015, 44(6):669-673.ZHOU C, LI W, ZHANG Z B, et al. Self-generated model for reaction network of pyrolysis of n-pentane[J]. Petrochemical Technology, 2015, 44(6):669-673.
[55]	张红梅, 罗殿英, 赵雨波, 等. 典型烃类分子裂解产物分布数值模拟[J]. 化学反应工程与工艺, 2011, 27(6):551-555.ZHANG H M, LUO D Y, ZHAO Y B, et al. Numerical simulation on distribution of products of typical hydrocarbon molecules pyrolysis[J]. Chemical Reaction Engineering & Technology, 2011, 27(6):551-555.
[56]	傅献彩, 沈文霞, 姚天扬. 物理化学[M]. 北京:高等教育出版社, 1990:798-812.FU X C, SHEN W X, YAO T Y. Physical Chemistry[M]. Beijing:Higher Education Press, 1990:798-812.
[57]	EYRING H. The activated complex and the absolute rate of chemical reactions[J]. Chemical Review, 1935, (1):65-77.
[58]	ARIBIKE D S, SUSU A A. Mechanistic modeling of the pyrolysis of n-heptane[J]. Thermochimica Acta, 1988, 127(1):259-273.
[59]	胡益锋. 石脑油裂解炉建模技术研究[D]. 北京:清华大学, 2005.HU Y F. Study on modeling of naphtha pyrolysis furnace[D]. Beijing:Tsinghua University, 2005.