A Comparative Study on CO₂-Switchable Foams Stabilized by C₂₂- or C₁₈-Tailed Tertiary Amines.

Area of Science:

• Materials Science
• Colloid and Surface Chemistry

Background:

• Bioresource-derived ultra-long chain surfactants show promise for stable CO₂ aqueous foams.
• Limited understanding exists regarding surfactant architecture, environmental factors, and foam properties.

Purpose of the Study:

• To investigate the impact of surfactant tail length on CO₂ foam properties.
• To compare the effects of temperature, pressure, and salinity on foams stabilized by different ultra-long chain surfactants.

Main Methods:

• Fabrication of CO₂ foams using N-erucamidopropyl-N,N-dimethylamine (UC₂₂AMPM) and N-oleicamidopropyl-N,N-dimethylamine (UC₁₈AMPM).
• Evaluation of foamability and stability using a high-temperature, high-pressure visualization foam meter.
• Characterization of continuous phase viscosity and liquid content via rheometry and FoamScan.

Main Results:

• Increased surfactant concentration and pressure enhanced foam properties for both UC₂₂AMPM and UC₁₈AMPM, with a more significant effect for UC₂₂AMPM.
• Increasing salinity and temperature reduced foam stability for both surfactants.
• UC₁₈AMPM foams exhibited greater sensitivity to temperature and salinity, indicating weaker salt and temperature resistance compared to UC₂₂AMPM foams.

Conclusions:

• The longer hydrophobic chain of UC₂₂AMPM contributes to higher viscosity and lower surface tension, enhancing CO₂ foam stability.
• Surfactant architecture, specifically tail length, critically influences CO₂ foam performance under varying environmental conditions.
• UC₂₂AMPM-stabilized CO₂ foams demonstrate superior robustness against temperature and salinity challenges.