Oxidation of CO by SO2: a theoretical study
George B Bacskay1, John C Mackie
1School of Chemistry, University of Sydney, NSW 2006, Australia.
The Journal of Physical Chemistry. A
|July 13, 2006
Summary
This study investigates the reactions between sulfur dioxide (SO2) and carbon monoxide (CO) using quantum chemical calculations. Including trace impurities like H2O significantly improves modeling of SO2 decomposition in combustion.
Area of Science:
- Chemical Kinetics
- Quantum Chemistry
- Combustion Science
Background:
- The reactions SO2 + CO --> CO2 + SO and SO + CO --> CO2 + S are crucial in combustion processes.
- Accurate kinetic data are essential for modeling these reactions, but experimental determination can be affected by impurities.
- Previous studies using quantum chemistry alone could not fully explain observed SO2 decomposition.
Purpose of the Study:
- To characterize the potential energy surfaces and derive rate coefficients for the SO2 + CO and SO + CO reactions using advanced quantum chemical methods.
- To investigate the influence of trace impurities on the reaction kinetics and modeling of SO2 decomposition.
- To compute heats of formation for key sulfur-containing molecules.
Main Methods:
- Gaussian-3//B3LYP quantum chemical approach to map potential energy surfaces and identify transition states (TS).
- Kinetic analysis to derive rate coefficients for the elementary reactions.
- Incorporation of calculated rate coefficients and trace impurities (H2, CH4, H2O) into a kinetic model.
Main Results:
- Reaction 1 proceeds via cis- and trans-OSOCO transition states on singlet surfaces, involving intersystem crossing.
- Reaction 2 occurs on triplet surfaces via cis- and trans-SOCO transition states.
- The kinetic model, including trace impurities, successfully reproduces experimental SO2 decomposition data from shock tube studies.
Conclusions:
- Quantum chemical calculations provide accurate reaction pathways and rate coefficients for SO2 + CO reactions.
- Trace impurities, particularly H2O, play a critical role in the experimental measurement and kinetic modeling of SO2 decomposition.
- The study successfully reconciles theoretical calculations with experimental observations by accounting for impurity effects.
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