Extraction of Pyrrole from Its Mixture with n-Hexadecane Using Protic Ionic Liquids

Area of Science:

• Chemical Engineering
• Separation Science
• Green Chemistry

Background:

• Conventional hydrodenitrogenation for fuel purification is energy-intensive and costly.
• Ionic liquids (ILs) show promise for fuel denitrogenation but can be expensive.
• Protic ionic liquids (PILs) present a viable, cost-effective alternative to ILs.

Purpose of the Study:

• To predict and validate the phase equilibria of three PILs for fuel denitrogenation.
• To evaluate the performance of triethylammonium p-toluenesulfonate (TEA-TSA), triethylammonium salicylate (TEA-SA), and triethylammonium benzoate (TEA-BZ).
• To investigate the interactions governing the extraction of nitrogen compounds.

Main Methods:

• Conductor-like screening model for real solvents (COSMO-RS) for phase equilibria prediction.
• Experimental liquid-liquid extraction at 298 K and 1 atm using pyrrole in n-hexadecane.
• NRTL model for correlating experimental tie lines; analysis of interaction energy (ΔE) and excess enthalpy (H).

Main Results:

• TEA-TSA exhibited superior selectivity and distribution ratio for pyrrole removal compared to TEA-SA and TEA-BZ.
• All tested ternary systems showed positive slopes, indicating a high affinity for nitrogen compounds.
• TEA-TSA demonstrated high interaction energy (ΔE), and all PILs showed negative excess enthalpy (H), confirming strong hydrogen bonding.

Conclusions:

• PILs, particularly TEA-TSA, are effective and selective solvents for fuel denitrogenation.
• The study validates COSMO-RS and NRTL models for predicting PIL performance.
• Strong hydrogen bonding interactions are crucial for efficient nitrogen compound extraction by PILs.