Collection of scientific works Nanosystems, nanomaterials, nanotechnologies
Year 2025 Volume 23, Issue 4
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H. V. TETERIATNYKOV, A. Ya. KARVATSKYI, and O. I. IVANENKO

National Technical University of Ukraine 'Igor Sikorsky Kyiv Polytechnic Institute', 37, Beresteiskyi Ave., UA-03056 Kyiv, Ukraine

Molecular Dynamics Modelling of the Distribution of Gaseous Products of High-Density Polyethylene Pyrolysis Using the ReaxFF Force Field

983–997 (2025)

PACS numbers: 02.70.Ns, 07.05.Tp, 31.15.-p, 34.20.Gj, 36.20.-r, 82.30.Lp, 82.35.Np

Received 4 April, 2025; in revised form, 3 May, 2025

The object of the study is the pyrolysis process of high-density polyethylene (HDPE). The aim of the work is to study the qualitative and quantitative distributions of valuable and harmful gaseous products of HDPE pyrolysis and to determine rational temperature regimes for conducting the process with the maximum yield of valuable products and minimizing the harmful impact on the environment. The research is based on the methods of molecular dynamics (MD) modelling within the nanosize-computing cell using the reaction force field ReaxFF and specialized software products, namely, Materials Studio and LAMMPS. The research methodology includes: creating an atomistic model of a polymer chain using Materials Studio with the addition of oxygen molecules, carrying out its geometric optimization and energy minimization with equilibration in a canonical isothermal-isobaric ensemble (NVT) at a temperature of 300 K with a time integration step of 1 fs over 5 ns; simulation of the pyrolysis process using LAMMPS at temperatures of 600°C, 800°C, 1000°C, 1400°C, 1800°C, 2000°C. According to the results of MD simulation of pyrolysis, graphs of the yield of the number of molecules of the main gaseous products are constructed depending on time, namely, O2, H2, CO, C2H2, C2H4, C2H6, CH2O, CH4, CO2. As shown, when oxygen concentration approaches the minimum, changes in the concentrations of the intermediate and final gaseous products become more significant. Among the main gaseous products of pyrolysis, the following components have the highest yield (≥10 molecules): hydrogen (H2), methane (CH4), ethylene (C2H4), acetylene (C2H2), and carbon monoxide (CO). The temperature regime of HDPE pyrolysis is optimized based on the criterion of maximum yield of the main gaseous products, the results of which determine that, at a temperature of 1000°C, a sufficiently intensive release of H2, CH4, C2H4 and CO occurs, and a further increase in a temperature to 1400°C, 1800°C and 2000°C leads to both an increase in the yield of H2 and a decrease in the release of CO and some other hydrocarbons (e.g., CH4). Therefore, a temperature of 1000°C is taken as optimal. The results obtained will contribute to a deeper understanding of the processes of pyrolysis decomposition of HDPE at nanolevel and the development of effective methods for the utilization of polymer waste.

KEY WORDS: pyrolysis, high-density polyethylene, molecular dynamics, force field ReaxFF, simulation, gaseous reaction products

DOI: https://doi.org/10.15407/nnn.23.04.0983

Citation:
H. V. Teteriatnykov, A. Ya. Karvatskyi, and O. I. Ivanenko, Molecular Dynamics Modelling of the Distribution of Gaseous Products of High-Density Polyethylene Pyrolysis Using the ReaxFF Force Field, Nanosistemi, Nanomateriali, Nanotehnologii, 23, No. 4: 983–997 (2025); https://doi.org/10.15407/nnn.23.04.0983
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