Deterpenation of citrus essential oil with 1-ethyl-3-methylimidazolium acetate: A comparison of unit operations

摘要

Deterpenation of an essential oil improves its stability and quality, thus increasing its market value. In this work, different unit operations to carry out the deterpenation of citrus essential oil were evaluated by simulation. The selected processes were: liquid-liquid extraction using the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) as solvent, vacuum distillation, and extractive distillation using [C(2)mim][OAc] as entrainer. A pressure of 5 kPa was selected for distillation processes in order to maintain the organoleptic properties of the essential oil. To that aim, isobaric vapor-liquid equilibria were determined at that pressure for limonene + linalool and linalool + [C-2 mim][OAc] binary, and limonene + linalool + [C(2)mim] [OAc] ternary, systems. NRTL adequately correlated experimental data and the obtained parameters were used for simulations. Liquid-liquid extraction was shown to be unsuccessful in providing a significant deterpenation. Distillation allowed the recovery of all the fed linalool (100 kg/h) almost pure, but very demanding conditions were required: a reflux ratio and number of plates of 3 and 45, respectively. The use of [C(2)mim][OAc] as entrainer increases the relative volatility of limonene and linalool, and greatly facilitates their separation by reducing the reflux ratio and number of plates required to 1 and 20 respectively, and also diminishes the energy requirements. The vacuum level of the flash unit used to recover the entrainer drastically affects the essential oil production rate.