Separation of N2O and CO2 using room-temperature ionic liquid [bmim][BF4]

Area of Science:

• Chemical Engineering
• Thermodynamics
• Separation Science

Background:

• Separating nitrous oxide (N2O) and carbon dioxide (CO2) is crucial for various industrial processes.
• Room-temperature ionic liquids (RTILs) show promise for gas separation applications.
• Accurate thermodynamic models are needed to predict and optimize RTIL-based separations.

Purpose of the Study:

• To develop and validate a ternary equation of state (EOS) model for the N2O/CO2/[bmim][BF4] system.
• To understand and predict the separation of N2O and CO2 using the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]).
• To evaluate the gas selectivity of N2O/CO2 mixtures in the presence of the RTIL.

Main Methods:

• Development of a ternary Redlich-Kwong (RK) EOS model with empirical interaction parameters.
• Determination of binary interaction parameters using measured vapor-liquid equilibrium (VLE) data for N2O/[bmim][BF4] and CO2/[bmim][BF4], and literature data for N2O/CO2.
• Validation of the ternary EOS model through VLE experiments for the N2O/CO2/[bmim][BF4] system at temperatures from 296 to 315 K.

Main Results:

• The binary EOS models accurately predicted liquid-liquid phase separation observed in VLLE experiments.
• The ternary EOS model successfully predicted VLE behavior for the N2O/CO2/[bmim][BF4] system.
• Gas selectivity for N2O/CO2 (α(N2O/CO2)) was enhanced to 1.4-1.5 with the ionic liquid, compared to 0.96-0.98 without it.
• Ionic liquid concentration did not significantly impact selectivity, but its presence was essential for separation.

Conclusions:

• The developed ternary EOS model provides a reliable tool for predicting N2O/CO2 solubility and separation behavior in [bmim][BF4].
• The addition of [bmim][BF4] significantly improves the selectivity for N2O/CO2 separation.
• This study demonstrates the practical utility of RTILs and EOS modeling for efficient gas separation processes.