Solubility of Caffeine in Supercritical CO₂: A Molecular Dynamics Simulation Study

Area of Science:

• Chemical Engineering
• Physical Chemistry
• Computational Chemistry

Background:

• Caffeine extraction is vital for decaffeinated products.
• Solvent choice significantly impacts extraction efficiency.
• Supercritical carbon dioxide (scCO2) is a preferred green solvent due to its environmental benefits and recyclability.

Purpose of the Study:

• To investigate caffeine solvation properties in scCO2 using molecular dynamics simulations.
• To understand the interactions between caffeine and scCO2 at different temperatures (318 K and 350 K).

Main Methods:

• Molecular dynamics simulations were employed.
• The study focused on caffeine solvation in supercritical carbon dioxide.
• Simulations were conducted at 318 K and 350 K.

Main Results:

• Caffeine molecules do not aggregate in scCO2, unlike in water, due to strong caffeine-CO2 interactions.
• A distinct scCO2 solvent shell surrounds caffeine molecules, driven by electron-donor-acceptor (EDA) and hydrogen-bonding interactions.
• While minor temperature-dependent shifts in CO2 distribution occur, the overall solvation structure remains stable.
• Higher temperatures weaken hydrogen bonds but strengthen EDA interactions between caffeine and CO2.

Conclusions:

• The interplay of EDA and hydrogen-bonding interactions is crucial for stable solvent structures and caffeine solubility in scCO2.
• scCO2 exhibits favorable solvation properties for caffeine extraction.
• Understanding these molecular interactions can optimize decaffeination processes.