DFT study on the oxidation of sulfur-containing coke

Coal remains an important component of China’s energy mix, and the goals of carbon peaking and carbon neutrality have increased the need for research on clean coal combustion. Based on density functional theory, we use a sulfur-containing armchair-edge model of coal char to investigate the adsorption, migration, and rearrangement of atomic and molecular oxygen, followed by SO2 formation and release. Following the chemisorption of two oxygen atoms, SO2 formation and release proceed through three transition states with barriers of 378.12, 149.84, and 367.65 kJ/mol, respectively. For molecular oxygen, physisorption is followed by chemisorption and two subsequent transition states associated with SO2 formation and release, with barriers of 238.32 and 345.59 kJ/mol, respectively. Bond order analysis and transition state theory are used to examine the proposed pathways. Rate constants are also calculated at different temperatures. The reported kinetic trends suggest that atomic oxygen increases the rate constant of the rate-limiting step and thereby facilitates SO2 release from the sulfur-containing coal char model.