A thermochemical study on the primary oxidation of sulfur

ABSTRACT

Several chemical reactions related to the oxidation and combustion of sulfur are investigated using a number of computational chemistry methods with the objective of determining appropriate methods for use in developing an elementary reaction mechanism for oxidation of sulfur. Calculations are focused on thermochemical properties and reaction energetics for reactive species and transition state structures for reactions in the oxidation/combustion of sulfur. Reactions involving several intermediates resulting from the reactions of S₂ with oxygen were investigated with the density functional theory B3LYP (with several basis sets) and BB1K/GTLarge. The composite ab-initio methods G2, G3, G3MP2, G3B3, G3MP2B3 and CBS-QB3 were also used. Enthalpies of a series of sulfur compounds and transition state structures are calculated using the ab-initio and DFT calculations. The calculations were combined with isodesmic reaction analysis, whenever possible, in order to cancel error and improve the accuracy of the calculations. Results show that all B3LYP DFT calculations including the 6–311++G(3df,2p) basis set show poor outcome in estimating the enthalpy of reactions involving S₂. The six composite methods have all shown consistency with each other and their calculated reaction energies/bond energies are in good agreement with the available literature. Kinetic parameters for calculation of the kinetic parameters on SO₃ dissociation to SO₂ and O using the canonical transition state theory are reported.

KEYWORDS:

• Sulfur
• Quantum Chemistry
• SO3
• SO2

Acknowledgments

The results presented in this study have been obtained within the framework of the PEGASUS project. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 727540.

Additional information

Funding

This work was supported by the European Union’s Horizon 2020 research and innovation program [727540].