Discovering the desulfurization mechanisms of thiophenes catalyzed by CaO (001) different surfaces

Abstract

In this study, the mechanisms of thiophenes decomposition catalyzed by the perfect and defective surfaces of CaO were mainly investigated by density functional theory (DFT) calculations. By XPS analysis, thiophenes of YQ coal significantly decreases after adding CaO, meanwhile CaS obviously appears in XPS spectra, suggesting CaO possesses the strong desulfurization effect on thiophenes. DFT calculation results show that the direct C₂-S bond breakage of TH all difficultly occur on these three CaO surfaces, especially for the Ca_vac surface as of its highest energy barrier. Similar, its C₃-C₄ bond breakage is more difficult to occur on these three surfaces. However, the direct CH₃C₂-S bond breakage of 2-methylthiophene (2-MT) all easily happen on these three CaO surfaces, especially for the O_vac surface as of its lowest energy barrier and negative reaction energy. In addition, the sulfur atom of 2-MT finally combines with the Ca to form CaS on these surfaces, further discovering the reasons about the appearance and increase of CaS in XPS spectra. These DFT calculations can provide some theoretical basis for the catalyzed desulfurization mechanisms of thiophenes.