基于量子化学的玉米秸秆热解机理的模拟计算
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摘要
建立了玉米秸秆的分子模型,并以此为研究对象,采用密度泛函理论B3LYP方法,在6～31g基组水平上,对其进行了热解反应机理研究。设计了玉米秸秆热解过程的4条初反应路径,并在分析初反应结果的基础上设计了14条次反应路径,对每条反应路径的反应物,过渡态,中间体以及产物均进行了结构优化和频率计算。计算结果表明:玉米秸秆热解初期半纤维素开始热解,木质素侧链轻微热解;初反应R1,R4反应焓变较小,分别为395. 77 kJ/mol和104. 70 k J/mol,认为玉米秸秆热解主反应路径以TS2及TS8次反应路径为主,其热解产物包括呋喃类,吡喃类,烷烯烃和芳香族化合物。
The molecular model of corn stalk was established and chosen as a research object in this paper.The corn stalk molecular model were theoretically calculated by using density functional theory methods B3 LYP at 6 ～ 31 g level. Four initial reaction were designed,and then fourteen secondary reaction were designed according to the analysis of the initial reaction results. The reactants,transition states,intermediates and products in every reaction path were optimized and their frequency were calculated. The calculation results show that hemicellulose is pyrolysed earliest in the initial stage of corn stalk pyrolysis,the side chains of lignin also begin to pyrolyze slightly at the same time; the enthalpy changes of R1 and R4 in the initial reaction are395. 77 kJ/mol and 104. 70 kJ/mol respectively,which proves that the mainly pyrolysis reaction paths for corn stalk are the secondary reaction of TS2 and TS8. The pyrolysis products of corn stalk include furan,pyran,alkanes and aromatic compounds.
The molecular model of corn stalk was established and chosen as a research object in this paper.The corn stalk molecular model were theoretically calculated by using density functional theory methods B3 LYP at 6 ～ 31 g level. Four initial reaction were designed,and then fourteen secondary reaction were designed according to the analysis of the initial reaction results. The reactants,transition states,intermediates and products in every reaction path were optimized and their frequency were calculated. The calculation results show that hemicellulose is pyrolysed earliest in the initial stage of corn stalk pyrolysis,the side chains of lignin also begin to pyrolyze slightly at the same time; the enthalpy changes of R1 and R4 in the initial reaction are395. 77 kJ/mol and 104. 70 kJ/mol respectively,which proves that the mainly pyrolysis reaction paths for corn stalk are the secondary reaction of TS2 and TS8. The pyrolysis products of corn stalk include furan,pyran,alkanes and aromatic compounds.
引文
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[33]MAYER I.Charge,bond order and valence in the ABinitio SCF theory[J].Chemical Physics Letters,1983,97(3):270-274.
[34]黄金保,刘朝,魏顺安,等.纤维素热解形成左旋葡聚糖机理的理论研究[J].燃料化学学报,2011,39(8):590-594.
[35]MULLIKEN R S.Electronic population analysis on LCAO-MO Molecular Wave Functions[J].Journal of Chemical Physics,2004,23(10):1841-1846.
[36]王华静,赵岩,王晨,等.木质素二聚体模型物裂解历程的理论研究[J].化学学报,2009,67(9):893-900.
[37]LIU C,ZHANG Y,HUANG X.Study of guaiacol pyrolysis mechanism based on density function theory[J].Fuel Processing Technology,2014,123(7):159-165.
[2]黄金保,武书彬,程皓,等.木质素模化物键离解能的理论研究[J].燃料化学学报,2015,43(4):429-436.
[3]ZHANG Y,LIU C,XIE H.Mechanism studies onβ-D-glucopyranose pyrolysis by density functional theory methods[J].Jounal of Analytical&Applied Pyrolysis,2014,105:23-34.
[4]LUO Z,WANG S,LIAO Y F,et al.Resrarch on biomass fast pyrolysis for liquid fuel[J].Biomass Bioenergy,2004,26(5):455-462.
[5]赵晓倩,孙军,邹玲,等.玉米秸秆热解特性及其动力学研究[J].应用能源技术,2012(9):41-44.
[6]王明峰,蒋恩臣,周岭.玉米秸秆热解动力学分析[J].农业工程学报,2009,25(2):204-207.
[7]刘荣厚,袁海荣,徐璐.玉米秸秆热解反应动力学的研究[J].太阳能学报,2007,28(5):527-531.
[8]惠世恩,梁凌,范庆伟,等.玉米秸秆热解特性的实验研究及动力学分析[J].热力发电,2014(43)4:69-75.
[9]王树荣,谭洪,骆仲泱,等.木聚糖快速热解试验研究[J].浙江大学学报(工学版),2006,40(3):419-423.
[10]黄金保,刘朝,曾桂生,等.左旋葡聚糖热解机理的密度泛函理论研究[J].燃料化学学报,2012,40(7):807-815.
[11]HUANG J B,LIU C,TONG H,et al.Theoretical studies on pyrolysis mechanism of xylopyranose[J].Computation Theorrtical Chemistry,2012,1001(3):44-50.
[12]张智,刘朝,李豪杰,等.木聚糖单体热解机理的理论研究[J].化学学报,2011,69(18):2099-2107.
[13]张阳,陆强,廖航涛,等.葡萄糖热解生成5-羟甲基糠醛机理[J].燃烧科学与技术,2015(1):89-95.
[14]WANG S R,LUO Z Y.Pyrolysis of biomass components[M].Beijing:Science Press,2013.
[15]FARAVELLI T,FRASSOLDATI A,MIGLIAVACCAG,et al.Detailed kinetic modeling of the thermal degradation of lignins[J].Biomass&Bioenergy,2010,34(3):290-301.
[16]吕高金.玉米秸秆及其主要组分的热解规律与生物油特征组分的定量分析[D].广州:华南理工大学,2012.
[17]王少光,武书彬,郭秀强,等.玉米秸秆木素的化学结构及热解特性[J].华南理工大学学报(自然科学版),2006,34(3):39-42.
[18]黄金保,吴隆琴,童红,等.半纤维素模型化合物热解机理的理论研究[J].燃料化学学报,2016,44(8):911-920.
[19]边静.农林生物质半纤维素分离及降解制备低聚木糖研究[D].北京:北京林业大学,2013.
[20]EBRINGEROVAA,HEINZE T.Xylan and xylan derivatives-Biopolymers with valuable properties,1.Naturally occurring xylans structures,isolation procedures and properties[J].Macromolecular Rapid Communications,2015,21(9):542-556.
[21]ALEN R,KUOPPALA E,OESCH P.Formation of the main degradation compound groups from wood and its components during pyrolysis[J].Journal of Analytical&Applied Pyrolysis,1996,36(96):137-148.
[22]SVENSON J,PETTERSSON J B C,DAVIDSSON KO.Fast Pyrolysis of the main components of birch wood[J].Combustion Science&Technology,2004,176(5-6):977-990.
[23]YANG H,YAN R,CHEN H,et al.In-depth investigation of biomass pyrolysis based on three major components:hemicellulose,cellulose and lignin[J].Energy&Fuels,2011,20(1):388-393.
[24]NIKSA S.Predicting the rapid devolatilization of diverse forms of biomass with bio-flashchain[J].Proceedings of the Combustion Institute,2000,28(2):2727-2733.
[25]秦育红.生物质气化过程中焦油形成的热化学模型[D].山西:太原理工大学,2009.
[26]GIRIO F M,FONSECA C,CARVALHEIRO F,et al.Hemicellulose for fuel ethanol:A review[J].Bioresource Technology,2010,101(13):4775-4800.
[27]HEREDIA A,JIMENEZ A,GUILLEN R.Composition of plant cell walls[J].Zeitschriftfür Lebensmittel-Untersuchung und Forschung,1995,200(1):24-31.
[28]ZHANG M,GENG Z,YU Y.Density functional theory(DFT)study on the dehydration of cellulose[J].Energy&Fuels,2011,25(6):2664-2670.
[29]刘倩.基于组分的生物质热裂解机理研究[D].杭州:浙江大学,2009.
[30]RAVEENDRAN K,GANESH A,KHILAR K C.Pyrolysis characteristics of biomass and biomass components[J].Fuel,1996,75(8):987-998.
[31]PISKORZ J,RADLEIN D,SCOTT D S.On the mechanism of the rapid pyrolysis of cellulose[J].Journal of Analytical&Applied Pyrolysis,1986,9(2):121-137.
[32]刘朝,李豪杰,黄金保.木聚糖热解过程的分子动力学模拟[J].功能高分子学报,2010,23(3):291-296.
[33]MAYER I.Charge,bond order and valence in the ABinitio SCF theory[J].Chemical Physics Letters,1983,97(3):270-274.
[34]黄金保,刘朝,魏顺安,等.纤维素热解形成左旋葡聚糖机理的理论研究[J].燃料化学学报,2011,39(8):590-594.
[35]MULLIKEN R S.Electronic population analysis on LCAO-MO Molecular Wave Functions[J].Journal of Chemical Physics,2004,23(10):1841-1846.
[36]王华静,赵岩,王晨,等.木质素二聚体模型物裂解历程的理论研究[J].化学学报,2009,67(9):893-900.
[37]LIU C,ZHANG Y,HUANG X.Study of guaiacol pyrolysis mechanism based on density function theory[J].Fuel Processing Technology,2014,123(7):159-165.