Modelling the Kinetics of Steam Distillation of Essential Oils from Lemon Grass (Cymbopogon Spp.)

The kinetics of essential oil recovery from lemon grass was investigated using an experimentally validated first order kinetic model. Essential oil recovery was accomplished in a steam distillation equipment using 100g of plant material in different physical states. The kinetic model developed did not take into consideration the resistance to oil diffusion from the tissues within the plant material to the leaf surface. The integral method of analysis was used to test the fit of the model to the experimental results. The straight lines obtained indicated that the recovery of essential oils from lemon grass followed first order rate kinetics with a mean rate constant, k, of 0.0451. It was observed that oil extraction was not instantaneous as some time was required to wet the plant material to enable the oil diffuse from within the leaves to the surface. Furthermore, loose packing of the plant material within the steam distillation equipment improved oil yield and drying the plant material prior to distillation did not reduce the quantity of oil available for recovery.