Revealing the catalytic gasification mechanisms of toluene and naphthalene in supercritical water using ReaxFF-MD and DFT methods

Abstract

Supercritical water gasification (SCWG) is a promising method for treating hazardous oily sludge waste from petroleum industry. However, achieving complete gasification under mild conditions remains challenging, particularly for persistent intermediates such as toluene and naphthalene. Herein, molecular dynamics simulations are used to explore the impact of Na₂CO₃ on target product yields from toluene and naphthalene in SCWG. The findings reveal that Na₂CO₃ considerably enhances radical yields within the reaction system, especially OH radicals, leading to increased gas production (H₂, CO, and CO₂). Molecular dynamics and density functional theory calculations reveal that Na₂CO₃ accelerates the ring-opening process and reduces the energy barrier of toluene and naphthalene to 7.4379 ± 0.0001 kcal/mol and 53.5887 ± 0.0011 kcal/mol, respectively. This study highlights OH radicals as an effective active substance in SCWG aromatic conversion. Further catalyst optimization and system design are essential for a highly efficient and clean oily sludge treatment.