Mechanism insight into the formation of H2S from thiophene pyrolysis: A theoretical study

• Published in: Frontiers of environmental science & engineering Vol. 15; no. 6; p. 120
• Main Authors: Yang, Shiguan, Fan, Xinrui, Liu, Ji, Zhao, Wei, Hu, Bin, Lu, Qiang
• Format: Journal Article
• Language: English
• Published: Beijing Higher Education Press 01.12.2021; Springer Nature B.V
• Subjects: Decomposition; Density functional theory; Earth and Environmental Science; Environment; Hydrogen; Hydrogen sulfide; Industrial applications; Pyrolysis; Radicals; Research Article; Rubber; Sulfur; Sulfur content; Waste utilization; H; Pyrolysis; Density functional theory; Waste rubber; S; Thiophene
• ISSN: 2095-2201; 2095-221X
• DOI: 10.1007/s11783-021-1404-8

Pyrolysis is an efficient and economical method for the utilization of waste rubber, but the high sulfur content limits its industrial application. Currently, the migration and transformation of the element S during pyrolysis of waste rubber is far from well known. In this work, a density functional theory (DFT) method was employed to explore the possible formation pathways of H 2 S and its precursors (radicals HS · and S ·) during the pyrolysis of thiophene, which is an important primary pyrolytic product of rubber. In particular, the influence of reactive hydrogen radicals was carefully investigated in the thiophene pyrolysis process. The calculation results indicate that the decomposition of thiophene tends to be initiated by hydrogen transfer between adjacent carbon atoms, which needs to overcome an energy barrier of 312.4 kJ/mol. The optimal pathway to generate H 2 S in thiophene pyrolysis involves initial H migration and S-C bond cleavage, with an overall energy barrier of 525.8 kJ/mol. In addition, a thiol intermediate that bears unsaturated C-C bonds is essential for thiophene pyrolysis to generate H 2 S, which exists in multiple critical reaction pathways. Moreover, the presence of hydrogen radicals significantly changes the decomposition patterns and reduces the energy barriers for thiophene decomposition, thus promoting the formation of H 2 S. The current work on H 2 S formation from thiophene can provide some theoretical support to explore clean utilization technologies for waste rubber.