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典型聚乙烯、聚丙烯、聚苯乙烯废塑料共热解初期反应特性的ReaxFF分子模拟研究

贺兴处 陈德珍

贺兴处, 陈德珍. 典型聚乙烯、聚丙烯、聚苯乙烯废塑料共热解初期反应特性的ReaxFF分子模拟研究[J]. 燃料化学学报(中英文), 2022, 50(3): 346-356. doi: 10.1016/S1872-5813(21)60161-5
引用本文: 贺兴处, 陈德珍. 典型聚乙烯、聚丙烯、聚苯乙烯废塑料共热解初期反应特性的ReaxFF分子模拟研究[J]. 燃料化学学报(中英文), 2022, 50(3): 346-356. doi: 10.1016/S1872-5813(21)60161-5
HE Xing-chu, CHEN De-zhen. ReaxFF MD study on the early stage co-pyrolysis of mixed PE/PP/PS plastic waste[J]. Journal of Fuel Chemistry and Technology, 2022, 50(3): 346-356. doi: 10.1016/S1872-5813(21)60161-5
Citation: HE Xing-chu, CHEN De-zhen. ReaxFF MD study on the early stage co-pyrolysis of mixed PE/PP/PS plastic waste[J]. Journal of Fuel Chemistry and Technology, 2022, 50(3): 346-356. doi: 10.1016/S1872-5813(21)60161-5

典型聚乙烯、聚丙烯、聚苯乙烯废塑料共热解初期反应特性的ReaxFF分子模拟研究

doi: 10.1016/S1872-5813(21)60161-5
基金项目: 国家自然科学基金(51776141)和上海市科委国际合作项目(20230712900)资助
详细信息
    作者简介:

    贺兴处(1994—),男,硕士研究生,hexingchu@126.com

    通讯作者:

    E-mail:chendezhen@tongji.edu.cn

  • 中图分类号: O63

ReaxFF MD study on the early stage co-pyrolysis of mixed PE/PP/PS plastic waste

Funds: The project was supported by National Natural Science Foundation of China (51776141) and Shanghai Science and Technology Commission Project for International Cooperation and Exchanges (20230712900)
  • 摘要: 利用反应力场分子模拟(ReaxFF MD)结合反应机理自分析(AutoRMA)工具,从动力学、热解产物及热解反应过程三方面在原子层面上,探究了典型聚乙烯(PE)、聚丙烯(PP)、聚苯乙烯(PS)废塑料共热解的反应机理。结果表明,PE/PP/PS共热解的动力学参数可通过C–C键和C–H键断裂的活化能加权求和(即Char Bonds方法) 获得,其活化能估计值与实验值的误差仅为±3.86%;因此可以由C–C键和C–H键的断裂来表征热解反应进程。对于PP-PE混合塑料热解体系,增加其中PP的含量可以提高油和可燃气的产率,而对于PP-PS体系,增加其中PS的含量可以提高炭和油产率。在PE-PP-PS混合塑料热解体系中,高温有利于重油裂解为轻油,轻油相对含量从2400 K的44.77%升高到3000 K的56.18%;同时,高温也会促使烃类小分子进一步裂解生成更小分子产物,随热解温度升高,H2和CH4的产率明显上升,但C2H4和C3H6的产率先上升后降低。相比单独热解,混合热解体系开始反应时间有所延迟,但达到第一次平衡的总反应时间缩短,并且更倾向于生成较小分子的产物。PE和PP单独热解时,首先生成其单体,继而生成烷烃和小分子气体,但在共热解过程中,首先生成烷烃和小分子气体,而后生成其单体。PS在共热解体系中更倾向于提供·H自由基从而与PE和PP生成的自由基结合,形成小分子烷烃或H2
  • FIG. 1389.  FIG. 1389.

    FIG. 1389.  FIG. 1389.

    图  1  PE-PP-PS体系初始构象

    Figure  1  Initial snapshot of PE-PP-PS model system

    图  2  不同温度下PE-PP-PS体系共热解过程C–C键和C–H键数量变化、固体转换率及动力学计算

    Figure  2  Number change of C–C and C–H bonds in the pyrolysis system at different temperatures as well as the solid conversion rate and related kinetic profiles: (a) C–C bond number change; (b) C–H bond number change; (c) solid conversion rate; (d) C–H bond number in solid products; (e) C–C bond number in solid products; (f) kinetics calculation

    图  3  不同温度下PE/PP/PS单独热解及PE/PP和PP/PS共热解过程C–C键和C–H键数量变化

    Figure  3  Changes in C–C bond and C–H bond number during isothermal pyrolysis of PE/PP/PS and binary mixture of PE/PP and PP/PS at different temperatures

    图  4  3000 K下PE/PP混合热解过程三项产物产率变化

    Figure  4  Changes in the product yields during PE/PP co-pyrolysis at 3000 K

    图  5  3000 K下PE/PP不同比例混合热解80 ps油产品比率

    Figure  5  Heavy oil and light oil ratio from PE/PP co-pyrolysis at 3000 K for 80 ps

    图  6  3000 K下PE/PP不同比例共热解80 ps主要气体组分

    Figure  6  Components of gas products from PE/PP co-pyrolysis after running 80 ps at 3000 K

    图  7  3000 K下PP/PS共热解过程三项产物产率变化

    Figure  7  Changes of product yields during PP/PS co-pyrolysis at 3000 K

    图  8  3000 K下PP/PS不同比例共热解80 ps后油产品比率

    Figure  8  Heavy oil and light oil ratio from the PP/PS co-pyrolysis at 3000 K for 80 ps

    图  9  3000 K下PP/PS在不同比例下共热解80 ps后主要气体组分

    Figure  9  Components of gas products from PP/PS co-pyrolysis at 3000 K for 80 ps

    图  10  2400−3000 K下PE-PP-PS体系热解主要产品产率及转化率

    Figure  10  Conversion rate and oil and gas product yields for the co-pyrolysis of PE-PP-PS at 2400–3000 K

    图  11  不同温度下PE-PP-PS体系热解气主要组分

    Figure  11  Components of gas products from PE-PP-PS co-pyrolysis at different temperatures

    表  1  废塑料典型组分主要来源及其热解产品分布

    Table  1  Main sources of typical plastics and their pyrolysis products at low and high temperatures

    ComponentSourceLow temperature pyrolysis productsHigh temperature pyrolysis products
    PEhousehold, industrial packaging, agricultural filmwax, oil[5, 6]gas, light oil[6, 7]
    PPhousehold, industrial packaging, automotive industrywax, oil[5, 6]gas, light oil[6, 7]
    PShousehold, industrial packaging, construction, WEEEtoluene, styrene and
    its oligomers [8]
    styrene and its oligomers, PAH[8]
    下载: 导出CSV

    表  2  模拟体系分子构成

    Table  2  Molecular composition of simulation system

    System modelPE(C300H602) chain numberPP(C300H602) chain numberPS(C304H306) chain number
    PE9
    PP9
    PS14
    PE-PP-8-383
    PE-PP-1-155
    PE-PP-3-838
    PP-PS-9-866
    PP-PS-3-162
    PP-PS-1-326
    PE-PP-PS622
    下载: 导出CSV

    表  3  PE/PP/PS废塑料单独热解及共热解过程动力学参数

    Table  3  Pyrolysis kinetic parameters of PE, PP, PS and mixtures of PE-PP, PP-PS and PE-PP-PS

    SystemSimulation time
    t/ps
    Activation energy Ea/(kJ·mol−1)Preexponential factor A/s−1Correlation coefficient
    experimentalsimulatedexperimentalsimulatedexperimentalsimulated
    PE 20 362.9 367.89a 4.09 × 1023 1.17 × 1022 0.978 0.973
    PP 7 332.3 332.28b 1.38 × 1022 2.55 × 1022 0.996 0.897
    PS 12 257.4 252.27b 2.61 × 1016 9.87 × 1020 0.997 0.983
    PE-PP-8-3 9 338.4 337.75b 6.71 × 1022 7.37 × 1022 0.979 0.990
    PP-PS-9-8 17 300.4 302.60b 1.65 × 1019 1.44 × 1022 0.999 0.997
    PE-PP-PS 16 314.7 310.85b 9.24 × 1019 2.74 × 1022 0.998 0.995
    a: calculated by bonds method; b: calculated by char bonds method
    下载: 导出CSV

    表  4  3000 K下PE/PP/PS在等温混合热解化学反应进程

    Table  4  Chemical reaction process during isothermal co-pyrolysis of PE/PP/PS at 3000 K

    PlasticSystem modelChemical reaction process
    PEPE
    PE-PP-8-3
    PE-PP-PS
    PPPP
    PPPE-PP-8-3
    PP-PS-9-8
    PE-PP-PS
    PSPS
    PP-PS-9-8
    PE-PP-PS
    下载: 导出CSV
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出版历程
  • 收稿日期:  2021-07-20
  • 修回日期:  2021-08-31
  • 网络出版日期:  2021-09-18
  • 刊出日期:  2022-03-28

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