Ethane as an alternative solvent for supercritical extraction of orange peel oils

Abstract

The objective of this study was to investigate the superiority of ethane in comparison to CO2 as a supercritical extraction solvent for deterpenating citrus oils. A rigorous computer code was developed that optimized extraction column operating conditions to minimize solvent recirculation. The SRK equation of state was used as the thermodynamic model after globally optimizing its adjustable binary interaction parameters to a combination of different literature data sets consisting of binary isothermal P–x, y, ternary constant composition P–T, and ternary isothermal isobaric x–y data. An investigation of the effects of different process variables on the degree of extraction revealed complicated and interconnected relations among the variables and extraction efficiencies. However, since the process of deterpenation, in particular, benefits from higher solubility more than from higher selectivity, increases in temperature, pressure, solvent-to-feed ratio, and reflux rate all seem to favor the separation. To compare the performance of ethane and carbon dioxide for orange oil deterpenation, selectivities of separation between the terpene and aroma fractions were calculated and compared for the two solvents. Compared to CO2, ethane is the better solvent for citrus constituents. This results in decreased solvent/feed mass ratio for ethane when the processes are compared at the same reduced pressure. However, these are not the only benefits of ethane over CO2. As the critical pressure of ethane is lower, the absolute operating pressures of ethane columns can be lower.