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

Highlights

• Possible formation pathways of H₂S were revealed in thiophene pyrolysis.

• The influence of hydrogen radicals on thiophene pyrolysis was examined.

• Thiophene decomposition starts with hydrogen transfer between adjacent C atoms.

• The presence of hydrogen radicals significantly promotes the formation of H₂S.

Abstract

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 H₂S 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 H₂S 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 H₂S, 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 H₂S. The current work on H₂S formation from thiophene can provide some theoretical support to explore clean utilization technologies for waste rubber.

Graphical abstract

Keywords

Density functional theory / Waste rubber / Thiophene / H₂S / Pyrolysis

References

[1] Al-Ahmary K M, Soliman S M, Habeeb M M, Al-Obidan A H (2017). Spectral analysis and DFT computations of the hydrogen bonded complex between 2,6-diaminopyridine with 2,6-dichloro-4-nitrophenol in different solvents. Journal of Molecular Structure, 1143(5): 31–41

[2] Bacskay G B, Martoprawiro M, Mackie J C (1999). The thermal decomposition of pyrrole: An ab initio quantum chemical study of the potential energy surface associated with the hydrogen cyanide plus propyne channel. Chemical Physics Letters, 300(3–4): 321–330

[3] Becke A D (1993). Density-functional thermochemistry. III. The role of exact exchange. Journal of Chemical Physics, 98(7): 5648–5652

[4] Buzaré J Y, Silly G, Emery J, Boccaccio G, Rouault E (2001). Aging effects on vulcanized natural rubber studied by high resolution solid state ¹³C-NMR. European Polymer Journal, 37(1): 85–91

[5] Cai J X, Lin R Y, Ma Q, Guo B, Liang J G (2019). Study on the reaction mechanism of thiophene aquathermolysis. Chemical Engineering of Oil and Gas, 48(1): 85–90+95 (in Chinese)

[6] Chu F M, Su M H, Yang G A (2020). Heat and mass transfer characteristics of ammonia regeneration in packed column. Applied Thermal Engineering, 176: 115405

[7] Dennington R, Keith T, Millam J (2016). GaussView, Version6. Semichem Inc. Shawnee Mission, KS

[8] Frisch M, Trucks G, Schlegel H, Scuseria G, Robb M, Cheeseman J, Scalmani G, Barone V, Mennucci B, Petersson G (2009). Gaussian 09. Revision D. 01. Gaussian, Inc., Wallingford CT

[9] Fukui K (1970). Formulation of the reaction coordinate. Journal of Physical Chemistry, 74(23): 4161–4163

[10] Hore N R, Russell D K (2004). The thermal decomposition of 5-membered rings: A laser pyrolysis study. New Journal of Chemistry, 28(5): 606–613

[11] Kong Y Q, Wang W J, Yang L J, Du X Z (2020). Energy efficient strategies for anti-freezing of air-cooled heat exchanger. Applied Energy, 261: 114468

[12] Kumar A, Choudhary V, Khanna R, Cayumil R, Ikram-Ul-Haq M, Sahajwalla V, Angadi S K I, Paruthy G E, Mukherjee P S, Park M (2017). Recycling polymeric waste from electronic and automotive sectors into value added products. Frontiers of Environmental Science & Engineering, 11(5): 53–62

[13] Lanteigne J R, Laviolette J P, Chaouki J (2015). Behavior of sulfur during the pyrolysis of tires. Energy & Fuels, 29(2): 763–774

[14] Li K, Wang Z X, Zhang G, Cui M S, Lu Q, Yang Y P (2020). Selective production of monocyclic aromatic hydrocarbons from ex situ catalytic fast pyrolysis of pine over HZSM-5 catalyst with calcium formate as a hydrogen source. Sustainable Energy & Fuels, 4(2): 538–548

[15] Li T S, Li J, Zhang H L, Sun K N, Xiao J (2019a). DFT research on benzothiophene pyrolysis reaction mechanism. Journal of Physical Chemistry A, 123(4): 796–810

[16] Li T S, Li J, Zhang H L, Sun K N, Xiao J (2019b). DFT study on the dibenzothiophene pyrolysis mechanism in petroleum. Energy & Fuels, 33(9): 8876–8895

[17] Liu J, Zhang X L, Hu B, Lu Q, Hiu D J, Dong C Q, Yang Y P (2020). Formation mechanism of HCN and NH₃ during indole pyrolysis: A theoretical DFT study. Journal of the Energy Institute, 93(2): 649–657

[18] Liu S, Yu J, Bikane K, Chen T, Ma C, Wang B, Sun L S (2018). Rubber pyrolysis: Kinetic modeling and vulcanization effects. Energy, 155(15): 215–225

[19] Lu Q, Tian H Y, Hu B, Jiang X Y, Dong C Q, Yang Y P (2016). Pyrolysis mechanism of holocellulose-based monosaccharides: The formation of hydroxyacetaldehyde. Journal of Analytical and Applied Pyrolysis, 120: 15–26

[20] Ma L Q (2015). Mechanical engineering polymer materials research. Advanced Materials Research, 1079–1080(2159): 33–36

[21] Miranda M, Pinto F, Gulyurtlu I, Cabrita I (2013). Pyrolysis of rubber tyre wastes: A kinetic study. Fuel, 103: 542–552

[22] Montgomery J A Jr, Frisch M J, Ochterski J W, Petersson G A (1999). A complete basis set model chemistry. VI. Use of density functional geometries and frequencies. Journal of Chemical Physics, 110(6): 2822–2827

[23] Nag N K, Sapre A V, Broderick D H, Gates B C (1979). Hydrodesulfurization of polycyclic aromatics catalyzed by sulfided CoO-MoO₃/γ-Al₂O₃: The relative reactivities. Journal of Catalysis, 57(3): 509–512

[24] López G, Olazar M, Aguado R, Bilbao J (2010). Continuous pyrolysis of waste tyres in a conical spouted bed reactor. Fuel, 89(8): 1946–1952

[25] Pakdel H, Pantea D M, Roy C (2001). Production of dl-limonene by vacuum pyrolysis of used tires. Journal of Analytical and Applied Pyrolysis, 57(1): 91–107

[26] Reed A, Weinstock R, Weinhold F (1985). Natural population analysis. Journal of Chemical Physics, 83(2): 735–746

[27] Roy C, Chaala A, Darmstadt H (1999). The vacuum pyrolysis of used tires: End-uses for oil and carbon black products. Journal of Analytical and Applied Pyrolysis, 51(1–2): 201–221

[28] Roy C, Rastegar A, Kaliaguine S, Darmstadt H, Tochev V (1995). Physicochemical properties of carbon blacks from vacuum pyrolysis of used tires. Plastics. Rubber and Composites Processing and Applications, 23(1): 21–30

[29] Schmidt M W, Gordon M S, Dupuis M (1985). The intrinsic reaction coordinate and the rotational barrier in silaethylene. Chemischer Informationsdienst, 16(9): 2585–2589

[30] Vasiliou A G K, Hu H, Cowell T W, Whitman J C, Porterfield J, Parish C A (2017). Modeling oil shale pyrolysis: High-temperature unimolecular decomposition pathways for thiophene. Journal of Physical Chemistry A, 121(40): 7655–7666

[31] Williams P T (2013). Pyrolysis of waste tyres: A review. Waste Management (New York, N.Y.), 33(8): 1714–1728

[32] Winkler J, Karow W, Rademacher P (2002). Gas-phase pyrolysis of heterocyclic compounds, part 1 and 2: flow pyrolysis and annulation reactions of some sulfur heterocycles: thiophene, benzo[b]thiophene, and dibenzothiophene. A product-oriented study. Journal of Analytical and Applied Pyrolysis, 62(1): 123–141

[33] Ye C, Wang Q H, Zheng Y Q, Li G N, Zhang Z G, Luo Z Y (2019). Techno-economic analysis of methanol and electricity poly-generation system based on coal partial gasification. Energy, 185: 624–632

[34] Ye C, Zheng Y Q, Xu Y S, Li G N, Dong C, Tang Y J, Wang Q H (2020). Energy and exergy analysis of poly-generation system of hydrogen and electricity via coal partial gasification. Computers & Chemical Engineering, 141: 106911

[35] Yoshizawa K, Shiota Y, Yamabe T (1999). Intrinsic reaction coordinate analysis of the conversion of methane to methanol by an iron-oxo species: A study of crossing seams of potential energy surfaces. Journal of Chemical Physics, 111(2): 538–545

[36] Yu J X, Xu J Q, Li Z C, He W Z, Huang J W, Xu J S, Li G M (2020). Upgrading pyrolytic carbon-blacks (CBp) from end-of-life tires: Characteristics and modification methodologies. Frontiers of Environmental Science & Engineering, 14(2): 19

[37] Zhang D Q, Tan S K, Gersberg R M (2010). Municipal solid waste management in China: Status, problems and challenges. Journal of Environmental Management, 91(8): 1623–1633

Acknowledgements

The authors thank the National Natural Science Foundation of China (51922040, 51821004), the China Postdoctoral Science Foundation (2019TQ0091), the Grants from Fok Ying Tung Education Foundation (161051), and the Fundamental Research Funds for the Central Universities (2020MS020, 2020DF01, 2018ZD08).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-021-1404-8 and is accessible for authorized users.

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