Interactions of Biodegradable Ionic Liquids with a Model Naphthenic Acid

Area of Science:

• Computational Chemistry
• Materials Science
• Green Chemistry

Background:

• Ionic liquids (ILs) are tunable solvents with potential applications in various industries.
• Biodegradable ILs are being developed to mitigate environmental concerns associated with traditional ILs.
• Functionalization of IL cations can modify their properties and interactions.

Purpose of the Study:

• To investigate the effect of different substitutional groups on the properties of biodegradable ionic liquids.
• To explore the hydrogen bonding interactions within functionalized ionic liquids and with model naphthenic acid.
• To evaluate the potential of these ILs for naphthenic acid extraction.

Main Methods:

• Density functional theory (DFT) calculations were employed to model five biodegradable ionic liquids.
• Analysis of electron density at bond critical points and noncovalent interactions was performed.
• Interaction energies between ILs and a model naphthenic acid were calculated.

Main Results:

• Ionic liquids with -NH2, -COOH, and -COOCH3 groups formed intramolecular hydrogen bonds with the [BF4]- anion.
• The [BMIM][BF4] IL functionalized with -COOH exhibited the strongest intramolecular hydrogen bonds.
• Naphthenic acid extraction primarily occurs via hydrogen bonding, with F-H bonds being most significant.
• ILs containing -COOH and -COOCH3 groups showed enhanced intermolecular hydrogen bonding with naphthenic acid.
• Higher interaction energies were observed between naphthenic acid and ILs with -COOH and -COOCH3 functional groups.

Conclusions:

• The functional groups -COOH and -COOCH3 significantly enhance the hydrogen bonding capabilities of biodegradable ionic liquids.
• These functionalized ILs demonstrate improved performance in naphthenic acid extraction due to stronger interactions.
• The findings suggest potential for developing efficient and environmentally friendly IL-based extraction systems.