ReaxFF molecular dynamics studies on the impact of reaction conditions in polystyrene conversion through hydrothermal gasification

Microplastics, particularly polystyrene (PS), are significant environmental pollutants due to their persistence and harmful effects on ecosystems and health. To address this issue, we explored hydrothermal gasification (HTG) as a novel approach for PS degradation using molecular dynamics simulations with ReaxFF. Our research reveals that HTG effectively converts PS into renewable syngas through complex reaction pathways influenced by temperature and water content. Temperature is critical in determining the dominant reaction mechanisms and syngas yield, while water plays a dual role of enhancing hydrogen production but also increasing activation energy for PS decomposition. The calculated activation energies vary significantly (198–289 kJ/mol), suggesting that optimizing reaction conditions is essential to maximize efficiency and hydrogen content in the produced syngas. This study provides insights into designing effective strategies for managing PS microplastic waste via hydrothermal gasification, aiming at a more sustainable future by converting plastics into valuable resources. • Detailed mechanism of the hydrothermal gasification of polystyrene microplastics. • In agreement with experimental data on hydrogen and syngas product, • Comprehensive understanding the crucial role of temperature in HTG reactions. • Dual role of water content on the HTG process. • Activation energy within the range of 198–289 kJ/mol.