UNVEILING THE EFFICIENCY OF CARBONYL SULFIDE CAPTURE BY ORGANIC SOLVENTS: AN ELECTRON CORRELATION STUDY

Abstract

Natural gas plays a pivotal role in the global transition toward cleaner energy alternatives; however, the sustainable utilization of unconventional and contaminated reserves remains restricted by the presence of hazardous sulfur species. While conventional gas sweetening processes effectively reduce hydrogen sulfide (H2S) levels, meeting stringent modern environmental regulations requires the comprehensive elimination of trace, less-reactive organosulfur contaminants, particularly carbonyl sulfide (COS). (COS) poses severe threats due to its high toxicity, pipeline corrosion potential, and tendency to poison industrial catalysts. To address the limitations of traditional alkanolamine absorption, Carbonyl Sulfide-Binding Organic Liquids (COS-BOLs) comprised of sterically hindered organic bases and linear alcohol co-solvents have emerged as highly tunable, efficient alternatives. Nevertheless, the precise molecular-level mechanisms and termolecular reaction kinetics governing these systems remain poorly understood. In this study, rigorous quantum mechanical calculations and electron correlation methods, including Density Functional Theory (DFT), were deployed to systematically investigate the efficiency of (COS) immobilization by organic solvent mixtures. Specifically, the termolecular, single-step reaction pathways between (COS) and key amidine or guanidine organic bases including 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclonon-5-ene (DBN), 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG), and 1,5,7-triazabicyclodec-5-ene (TBD) were mapped in the presence of various linear alcohols. By elucidating the dominant base effects and synergistic alcohol co-solvent behaviors through high-level electronic structure configurations, this work delivers crucial molecular insights necessary for the rational design and optimization of high-performance organic solvents for effective (COS) mitigation.