Theoretical Studies of Unimolecular Decomposition of Thiophene at High Temperatures

Thiophene is an organo-sulfur aromatic molecule present in fossil fuels and alternate fuels such as shale oils and contributes to air pollution via fuel burning. Hence, it is essential to remove thiophene and its derivatives during the refining process. In this regard, experimental and electronic structure theory studies investigating the thermal decomposition of thiophene have been reported in the literature. In the present work, high temperature thermal decomposition of thiophene was investigated using Born-Oppenheimer direct dynamics simulations. The trajectory integrations were performed on-the-fly at the density functional B3LYP/6-31+G* level of electronic structure theory to investigate the atomic level decomposition mechanisms. Simulation results show that C-S cleavage accompanied by an intramolecular proton transfer to C is the dominant initial dissociation step. Acetylene was observed as primary decomposition product and the results are in agreement with previous experimental studies.