Density functional theory study on the pyrolysis mechanism of thiophene in coal

The pyrolysis mechanism of thiophene in coal has been investigated with a density functional theory method. Three intramolecular hydrogen migration reaction paths leading to the formation of H2S were designed. It can be concluded that the favorable energy path by the kinetic analysis is that the α-H migrates to S firstly; then the β-H migrates to the α-C followed by a concerted C-S bond cleavage resulting in the cyclic structure of thiophene turning into a chain structure; finally H2S and butadiyne are formed via H migrating twice. In the favorable energy path, the rate determining step is the α-H migration to S, and the activation energy is about 351.63 kJ mol−1 at 298.15 K.