Separation of α-Terpineol and Limonene from an Orange Essential Oil Mixture Using Supercritical CO ₂ Pressure Reduction

Brazil is the world's largest orange producer, generating significant amounts of byproducts that are used to produce limonene-rich orange essential oil. In this sense, one possible alternative for its valorization is the biotransformation of limonene into α-terpineol, which has emerged as a promising valorization route, but the efficient separation of these compounds remains challenging due to their similar chemical nature. This work aimed to evaluate the solubility and fractionation behavior of α-terpineol and limonene in supercritical CO₂ (SC-CO₂) using a model mixture (orange essential oil + α-terpineol, 60:40 wt %), which simulated a biotransformation product. The best solubilization was found at 10 MPa and 40 °C. Supercritical fluid fractionation (SFF) was performed at different separator pressures (6-8 MPa) and temperatures (40-60 °C), to find optimal conditions for the selective recovery of α-terpineol. The SFF performed at 8 MPa and 40 °C achieved the precipitation of most α-terpineol. However, coprecipitation of limonene indicated limited selectivity under the tested conditions, likely due to molecular interactions in the complex multicomponent matrix. Calculated losses through the SFF at this same condition indicated a substantial limonene loss of nearly 50%, highlighting the challenges in designing an efficient system for terpene separation.