The sulfur fixation mechanisms of COS and SO2 on perfect and defect surfaces of CaO (001) investigated by DFT combined with XPS

Abstract

In this study, Erdos (ED) coal with high inorganic sulfur content was selected to investigate the sulfur fixation mechanisms of COS and SO₂ on CaO (001) perfect and defective surfaces by Density functional theory (DFT) combined with X-ray photoelectron spectroscopy (XPS). Pyrolysis and gas chromatography (Py-GC) was used to analyze the release behaviors of COS and SO₂ during coal pyrolysis. XPS proves that CaS and CaSO₄ peaks significantly increase after the co-pyrolysis of ED coal and CaO. The electronic structure analysis reveals that the O vacancy belongs to a strong electron-donator, indicating O vacancy would facilitate the stable adsorption of COS and SO₂ on this surface. The most possible sulfur fixation Path of COS would occur on the O vacancy surface accompanied by the formation of CaS and CO. However, SO₂ would be more inclined to be fixed in the form of sulfates similar to calcium sulfate on perfect and defective surfaces. These DFT calculation results are consistent with the experimental results. Thus, this study could provide theoretical support for the sulfur fixation mechanisms on the different surfaces of CaO (001) and for the improvement of the CaO sulfur-fixing agents.