CO₂ in Lyotropic Liquid Crystals: Phase Equilibria Behavior and Rheology

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Carbon capture and storage (CCS) is crucial for mitigating climate change.
• Novel absorbent materials are needed to improve the efficiency and cost-effectiveness of CO₂ capture.
• Liquid crystalline phases offer unique properties for gas absorption.

Purpose of the Study:

• To investigate the CO₂ absorption capacity of a liquid crystalline system composed of Pluronic L92, monoethanolamine (MEA), and water.
• To evaluate the phase transitions and rheological behavior of the system during CO₂ loading.
• To assess the thermal stability of the Pluronic L92 component in the presence of MEA for CCS applications.

Main Methods:

• Vapor-liquid equilibrium (VLE) measurements were conducted to determine CO₂ solubility.
• Small-angle X-ray scattering (SAXS) was used to monitor structural phase transitions.
• Rheological studies were performed to analyze changes in viscosity with CO₂ loading.
• Thermal stability tests were carried out to evaluate MEA degradation.

Main Results:

• The Pluronic L92/MEA/water system achieved a CO₂ loading of 38.6 g CO₂/kg sample at 6 bar CO₂ partial pressure.
• A phase transition from lamellar + hexagonal to hexagonal phase was observed at 25 °C during CO₂ loading.
• Viscosity increased with CO₂ loading until the hexagonal phase transition was complete.
• Pluronic L92 was found to be thermally stable and did not contribute to MEA degradation.

Conclusions:

• The investigated liquid crystalline system demonstrates significant CO₂ absorption potential for carbon capture.
• The observed phase transitions and rheological changes provide insights into the absorption mechanism.
• The thermal stability of Pluronic L92 suggests its suitability as a component in MEA-based CO₂ capture solvents.