Browsing by Author "Hadia, Abubaker"
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thesis.listelement.badge THEORETICAL INVESTIGATION OF CARBONYL SULFIDE CAPTURE BY AQUEOUS DIETHANOLAMINE SOLUTION(2017-05-02) Hadia, Abubaker; Kayı, HakanCarbonyl sulfide (COS), an unwanted impurity, released with a variety of processing gases. Capturing of COS can be achieved with liquid absorbents. Two different mechanisms are proposed in the literature for COS and diethanolamine (DEA) reaction, and both drive to a formation of thiocarbamate. The first mechanism is zwitterion intermediate mechanism, which takes two reaction steps. The first step is the forming of the zwitterion, and the second one is the deprotonation of the formed zwitterion. The second mechanism is termolecular mechanism in which a complex forms as intermediate in a single step reaction. Four different termolecular reactions among COS, DEA and water were investigated through the quantum chemical calculations, and structural, energetic and thermochemical properties were revealed. Theoretical standard free energy of activation (∆ ‡G ° ) and reaction (∆G°rxn), equilibrium constant (Keq) and reaction rate constant (k) values for these four termolecular reactions were calculated. Density Functional Theory (DFT) was applied during the theoretical investigations of this study utilizing the B3LYP hybrid functional, and 6-311G(d) basis set. In conclusion, calculated activation energy and reaction rate constant values obtained in this study were compared with the experimental data available in the literature, and under the guidance of these findings, the most probable termolecular reaction mechanism for the COS capture by aqueous DEA solution was revealed.