Experimental Determination of Triethylene Glycol (TEG) and Methanol Loss in Compressed CO2

Abstract The presence of polar organic impurities in dense-phase CO2 streams is a critical issue for carbon capture, utilization, and storage (CCUS) and enhanced oil recovery (EOR) operations. Among these impurities, triethylene glycol (TEG) and methanol are particularly important, owing to their widespread use in gas dehydration and hydrate inhibition. Their persistence in CO2 can alter compression behavior, promote corrosion through water film formation, and contaminate storage reservoirs. This study investigates the phase behavior of TEG and methanol in compressed CO2 under pipeline-relevant conditions using a high-pressure gas–liquid saturation unit combined with nuclear magnetic resonance (NMR) spectroscopy. The methodology enables reproducible equilibration and precise detection of trace polar organics in the vapor phase. The observed solubility trends are interpreted in terms of operational risks, including condensation, foaming, and corrosion initiation. The work does not disclose numerical data but provides a technical framework for understanding how methanol and TEG behave in dense-phase CO2 systems, linking laboratory observations to practical challenges in transport and storage. The findings are directly relevant for defining impurity specifications, improving EoS parameterization, and informing risk-based design and monitoring strategies in CCUS projects.