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

HE Xing-chu; CHEN De-zhen

doi:10.1016/S1872-5813(21)60161-5

Volume 50 Issue 3

Mar. 2022

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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

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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

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

doi: 10.1016/S1872-5813(21)60161-5

HE Xing-chu,
CHEN De-zhen^,

Thermal & Environmental Engineering Institute, Shanghai Engineering Research Center of Multi-source Solid Wastes Co-processing and Energy Utilization, Tongji University, Shanghai 200092, China

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)

Received Date: 2021-07-20
Rev Recd Date: 2021-08-31

Available Online: 2021-09-18

Publish Date: 2022-03-28

Abstract

Abstract

The early stage co-pyrolysis of typical plastic waste including polyethylene (PE), polypropylene (PP) and polystyrene (PS) were investigated by using the reactive force field molecular dynamics (ReaxFF MD) simulation with an automatic reaction mechanism analysis software (AutoRMA); the kinetic model, product yields and reaction process of co-pyrolysis were analyzed at atomic level. The results show that the kinetic parameters of PE/PP/PS co-pyrolysis can be obtained through the weighted sum of the parameters for the fracture of C–C and C–H bonds; the estimated activation energy is very close to the experimental one with a small error of ±3.86%, indicating that the fracture of C–C and C–H bonds can accurately characterize the co-pyrolysis process. For the co-pyrolysis of PE-PP mixture, an increase of PP content can improve the yields of oil and combustible gas, whereas for the co-pyrolysis of PP-PS mixture, the increase of PS content can improve the yields of tar and oil. In contrast, for the co-pyrolysis of PE-PP-PS mixture, a higher temperature is beneficial for the conversion of heavy oil into light oil; the light oil content increases from 44.77% at 2400 K to 56.18% at 3000 K. In addition, as a higher temperature can promote the further cracking of light hydrocarbons into gas products of smaller molecules, the yields of H₂ and CH₄ increase significantly with the increase of pyrolysis temperature, whereas the yields of C₂H₄ and C₃H₆ increase first and then decrease with the temperature. In comparison with the separated pyrolysis, the co-pyrolysis commences later, but displays shorter time to reach the first equilibrium state and generates products with smaller molecules. For the separate pyrolysis of PE and PP, their monomers emerge first, hereafter the alkanes and small molecule gases are produced; for the co-pyrolysis process, in contrast, the alkanes and small molecule gases are generated prior to the monomers. Moreover, PS tends to provide ·H radicals in the co-pyrolysis process, which can combine with the free radicals generated from PE and PP pyrolysis, forming small molecule alkanes and H₂.
- co-pyrolysis,
- plastic waste,
- reactive force field molecular dynamics (ReaxFF MD),
- kinetics,
- polyethylene (PE), polypropylene (PP), polystyrene (PS)

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References(28)

References

[1]	WILLIAMS P T, WILLIAMS E A. Interaction of plastics in mixed-plastics pyrolysis[J]. Energy Fuels,1999,13(1):188−196. doi: 10.1021/ef980163x
[2]	赵娟. 废塑料回收利用的研究进展[J]. 现代塑料加工应用,2020,32(4):60−63. ZHAO Juan. Research progress on plastic easte recycling[J]. Mod Plast Process Appl,2020,32(4):60−63.
[3]	张振华, 汪华林, 陈于勤, 胥培军. 聚乙烯类废弃塑料延迟焦化方法制取燃料油的研究[J]. 燃料化学学报,2008,36(2):223−226. doi: 10.3969/j.issn.0253-2409.2008.02.019 ZHANG Zhen-hua, WANG Hua-lin, CHEN Yu-qin, XU Pei-jun. Preparation of fuel oil from waste polyethylene by delayed coking[J]. J Fuel Chem Technol,2008,36(2):223−226. doi: 10.3969/j.issn.0253-2409.2008.02.019
[4]	KAMINSKY W, PREDEL M, SADIKI A. Feedstock recycling of polymers by pyrolysis in a fluidised bed[J]. Polym Degrad Stab,2004,85(3):1045−1050. doi: 10.1016/j.polymdegradstab.2003.05.002
[5]	DAS P, TIWARI P. The effect of slow pyrolysis on the conversion of packaging waste plastics (PE and PP) into fuel[J]. Waste Manage,2018,79:615−624. doi: 10.1016/j.wasman.2018.08.021
[6]	DONAJ P J, KAMINSKY W, BUZETO F, YANG W. Pyrolysis of polyolefins for increasing the yield of monomers’ recovery[J]. Waste Manage,2012,32(5):840−846. doi: 10.1016/j.wasman.2011.10.009
[7]	HONUS S, KUMAGAI S, FEDORKO G, MOLNÁR V, YOSHIOKA T. Pyrolysis gases produced from individual and mixed PE, PP, PS, PVC, and PET—Part I: Production and physical properties[J]. Fuel,2018,221:346−360. doi: 10.1016/j.fuel.2018.02.074
[8]	ONWUDILI J A, INSURA N, WILLIAMS P T. Composition of products from the pyrolysis of polyethylene and polystyrene in a closed batch reactor: Effects of temperature and residence time[J]. J Anal Appl Pyrolysis,2009,86(2):293−303. doi: 10.1016/j.jaap.2009.07.008
[9]	PREDEL M, KAMINSKY W. Pyrolysis of mixed polyolefins in a fluidised-bed reactor and on a pyro-GC/MS to yield aliphatic waxes[J]. Polym Degrad Stab,2000,70(3):373−385. doi: 10.1016/S0141-3910(00)00131-2
[10]	JIN Z C, YIN L J, CHEN D Z, JIA Y J, YUAN J, HU Y Y. Co-pyrolysis characteristics of typical components of waste plastics in a falling film pyrolysis reactor[J]. Chin J Chem Eng,2018,26(10):2176−2184. doi: 10.1016/j.cjche.2018.07.005
[11]	VAN DUIN A C T, DASGUPTA S, LORANT F, GODDARD W A. ReaxFF: A reactive force field for hydrocarbons[J]. J Phys Chem A,2001,105(41):9396−9409. doi: 10.1021/jp004368u
[12]	LIU X L, LI X X, LIU J, WANG Z, KONG B, GONG X M, YANG X Z, LIN W G, GUO L. Study of high density polyethylene (HDPE) pyrolysis with reactive molecular dynamics[J]. Polym Degrad Stab,2014,104:62−70. doi: 10.1016/j.polymdegradstab.2014.03.022
[13]	KNYAZEV V D. Effects of chain length on the rates of C−C bond dissociation in linear alkanes and polyethylene[J]. J Phys Chem A,2007,111(19):3875−3883. doi: 10.1021/jp066419e
[14]	贺兴处, 陈德珍, 梅振飞, 阿迪力·巴吐尔, 安青. CaO催化PE热解及H₂O对催化过程影响的ReaxFF MD研究与机理分析[J]. 化工学报,2021,:1−15. doi: 10.11949/0438-1157.20201566 HE Xing-chu, CHEN De-zhen, MEI Zhen-fei, ADILI Batuer, AN Qing. ReaxFF MD study on the pyrolysis of PE catalyzed by Cao and the effect of H₂O on the catalytic process and mechanism analysis[J]. J Chem Ind Eng,2021,1−15. doi: 10.11949/0438-1157.20201566
[15]	同济大学. 全自动 ReaxFF 反应机理分析软件[简称: AutoRMA] V1.0: 2021SR0108488[P]. 2021-01-20 Tongji university. Automatic ReaxFF reaction mechanism analyzer [abbreviation: AutoRMA] V1.0: 2021SR0108488[P]. 2021-01-20.
[16]	Sandia National Laboratories. LAMMPS[EB/OL]. http://lammps.sandia.gov.
[17]	ZHANG J L, GU J T, HAN Y, LI W, GAN Z X, GU J J. Supercritical water oxidation vs supercritical water gasification: Which process is better for explosive wastewater treatment?[J]. Ind Eng Chem Res,2015,54(4):1251−1260. doi: 10.1021/ie5043903
[18]	PITMAN M C, VAN DUIN A C T. Dynamics of confined reactive water in smectite clay-zeolite composites[J]. J Am Chem Soc,2012,134(6):3042−3053. doi: 10.1021/ja208894m
[19]	PONOMAREV I, VAN DUIN A C T, KROLL P. Reactive force field for simulations of the pyrolysis of polysiloxanes into silicon oxycarbide ceramics[J]. J Phys Chem C,2019,123(27):16804−16812. doi: 10.1021/acs.jpcc.9b03810
[20]	PAAJANEN A, VAARI J. High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study[J]. Cellul,2017,24(7):2713−2725. doi: 10.1007/s10570-017-1325-7
[21]	BHOI S, BANERJEE T, MOHANTY K. Molecular dynamic simulation of spontaneous combustion and pyrolysis of brown coal using ReaxFF[J]. Fuel,2014,136:326−333. doi: 10.1016/j.fuel.2014.07.058
[22]	张秀霞, 吕晓雪, 肖美华, 林日亿, 周志军. 典型烟煤热解机理的反应动力学模拟[J]. 燃料化学学报,2020,48(9):1035−1046. doi: 10.3969/j.issn.0253-2409.2020.09.002 ZHANG Xiu-xia, LU Xiao-xue, XIAO Mei-hua, LIN Ri-yi, ZHOU-Zhi-jun. Molecular re action dynamics simulation of pyrolysis mechanism of typical bituminous coal via ReaxFF[J]. J Fuel Chem Technol,2020,48(9):1035−1046. doi: 10.3969/j.issn.0253-2409.2020.09.002
[23]	ZHONG Q F, MAO Q Y, XIAO J, VAN DUIN A C T, MATHEWS J P. ReaxFF simulations of petroleum coke sulfur removal mechanisms during pyrolysis and combustion[J]. Combust Flame,2018,198:146−157. doi: 10.1016/j.combustflame.2018.09.005
[24]	ZHANG Z J, GUO L, ZHANG H Y, ZHAN J H. Comparing product distribution and desulfurization during direct pyrolysis and hydropyrolysis of Longkou oil shale kerogen using reactive MD simulations[J]. Int J Hydrogen Energy,2019,44(47):25335−25346. doi: 10.1016/j.ijhydene.2019.08.036
[25]	CHEN C, ZHAO L L, WU X, LIN S C. Theoretical understanding of coal char oxidation and gasification using reactive molecular dynamics simulation[J]. Fuel,2020,260:116300. doi: 10.1016/j.fuel.2019.116300
[26]	CHENOWETH K, CHEUNG S, VAN DUIN A C T, GODDARD III W A, KOBER E M. Simulations on the thermal decomposition of a poly(dimethylsiloxane) polymer using the ReaxFF reactive force field[J]. J Am Chem Soc,2005,127:7192−7202. doi: 10.1021/ja050980t
[27]	BATUER A, CHEN D Z, HE X C, HUANG Z. Simulation methods of cotton pyrolysis based on ReaxFF and the influence of volatile removal ratio on volatile evolution and char formation[J]. Chem Eng J,2021,405:126633. doi: 10.1016/j.cej.2020.126633
[28]	LI D, LEI S J, WANG P, ZHONG L, MA W C, CHEN G Y. Study on the pyrolysis behaviors of mixed waste plastics[J]. Renewable Energy,2021,173:662−674. doi: 10.1016/j.renene.2021.04.035