TY - JOUR
T1 - Combustion chemistry of COS and occurrence of intersystem crossing
AU - Zeng, Zhe
AU - Dlugogorski, Bogdan Z.
AU - Oluwoye, Ibukun
AU - Altarawneh, Mohammednoor
N1 - Funding Information:
This study has been supported by funds from the Australian Research Council (ARC), and grants of computing time from the National Computational Infrastructure (NCI), Canberra, Australia and the Pawsey Supercomputing Centre in Perth. M. Altarawneh acknowledges a start-up grant from College of Engineering at The United Arab Emirates University, UAEU (grant number: 31N421 ).
Publisher Copyright:
© 2020 The Authors
PY - 2021/1/1
Y1 - 2021/1/1
N2 - This contribution combines results of experiments with kinetic modelling to probe the unusual behaviour of carbonyl sulfide (COS), a sulfur species that frequently arises in fuel systems. The experiments identified CO and SO2 as the primary oxidation products, with no formation of CO2. The low ignition temperature (<600 K) of COS observed in prior experiments conflicts with the high activation barrier for the reaction COS + O2 → CO2 + SO of 211.3 kJ mol−1 on the traditional triplet reaction surface. We proposed that, this kinetic barrier prompts the reaction to transfer onto the singlet surface through intersystem crossing that allows the process to surmount lower-energy hurdles. By considering the oxidation of COS as a single step reaction, we fitted the Arrhenius parameter for the reaction COS + O2 → CO + SO2 directly from our experimental measurements. The fitted activation energy of 70.1 kJ∙mol−1 agrees with that of 85.4 ± 20.0 kJ∙mol−1 as calculated in literature at the Hartree-Fock level of theory, indicating the appearance of the intersystem crossing process in the oxidation of COS. The reaction mechanism based on this comportment leads to excellent agreement between the kinetic model and the experimentally measured quantities, such as the onset temperature and the conversion profiles of detected species. The proposed kinetic model for the oxidation of COS provides a tool to design both the SOx mitigation processes and industrial systems for safe handling of sulfur impurities in fossil fuels.
AB - This contribution combines results of experiments with kinetic modelling to probe the unusual behaviour of carbonyl sulfide (COS), a sulfur species that frequently arises in fuel systems. The experiments identified CO and SO2 as the primary oxidation products, with no formation of CO2. The low ignition temperature (<600 K) of COS observed in prior experiments conflicts with the high activation barrier for the reaction COS + O2 → CO2 + SO of 211.3 kJ mol−1 on the traditional triplet reaction surface. We proposed that, this kinetic barrier prompts the reaction to transfer onto the singlet surface through intersystem crossing that allows the process to surmount lower-energy hurdles. By considering the oxidation of COS as a single step reaction, we fitted the Arrhenius parameter for the reaction COS + O2 → CO + SO2 directly from our experimental measurements. The fitted activation energy of 70.1 kJ∙mol−1 agrees with that of 85.4 ± 20.0 kJ∙mol−1 as calculated in literature at the Hartree-Fock level of theory, indicating the appearance of the intersystem crossing process in the oxidation of COS. The reaction mechanism based on this comportment leads to excellent agreement between the kinetic model and the experimentally measured quantities, such as the onset temperature and the conversion profiles of detected species. The proposed kinetic model for the oxidation of COS provides a tool to design both the SOx mitigation processes and industrial systems for safe handling of sulfur impurities in fossil fuels.
KW - Carbonyl sulfide
KW - Combustion of reduced sulfur species
KW - Inter-system crossing (ISC)
KW - Jet-stirred reactor (JSR)
KW - Kinetic modelling
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U2 - 10.1016/j.fuel.2020.119257
DO - 10.1016/j.fuel.2020.119257
M3 - Article
AN - SCOPUS:85091998138
SN - 0016-2361
VL - 283
JO - Fuel
JF - Fuel
M1 - 119257
ER -