THEORETICAL INVESTIGATION INTO THE CAPTURE MECHANISM OF CARBONYL SULFIDE BY ORGANIC SOLVENTS AN AB INITIO QUANTUM CHEMICAL APPROACH

Abstract

The efficient removal of carbonyl sulfide (COS) from industrial gas streams is critical for environmental protection and catalyst preservation. In this work, an ab initio quantum chemical approach was employed to investigate the capture mechanisms and kinetics of twenty-four organic solvent mixtures composed of guanidine bases (BTMG, TBD) or amidine bases (DBU, DBN) paired with linear alcohols (C1–C6). Computational modeling performed at the ωB97X-D3/6-311++G(d,p) level, incorporating the polarizable continuum model (PCM), successfully validated the thermodynamic and kinetic feasibility of a proposed single-step termolecular reaction mechanism. The results demonstrate excellent alignment with established benchmarks for CO₂ capture in similar systems. Among all screened formulations, the BTMG/methanol system exhibited the lowest activation energy barrier and the highest reaction rate constant, rendering it the most effective candidate for COS sequestration, followed by TBD/1-propanol. For the amidine systems, DBU performed optimally with methanol and ethanol, while DBN showed the best compatibility with 1-propanol. These first-principles insights provide a robust theoretical foundation for the rational design of highly efficient, non-aqueous solvent mixtures for acid gas separation.