Supercritical fluid extraction and pretreatment processes for natural products using carbon dioxide

This dissertation presents the measurement of equilibrium solubility of spearmint oil components in supercritical CO{dollar}sb2{dollar} (SC-CO{dollar}sb2{dollar}) and supercritical CO{dollar}sb2{dollar} extraction of these oil components from spearmint leaves. The pretreatment using SC-CO{dollar}sb2{dollar} and water for the enhanced enzymatic hydrolysis of lignocellulosic materials and the crystallization of benzoic acid in a supercritical fluid crystallizer with a membrane were attempted in this dissertation.; By comparing reported solubility data, it was found that significant disagreements exist in the published equilibrium solubilities of various lipid substances in supercritical CO{dollar}sb2{dollar}. To overcome this problem, a new solubility measurement technique combining the static and dynamic methods was developed.; The solubility of l-limonene was higher than that of l-carvone. The solubility was found to be strongly dependent on the density of CO{dollar}sb2{dollar}. In the ternary system containing a mixture of l-carvone and l-limonene (4:1 by the weight) in CO{dollar}sb2{dollar}, the solubility of l-limonene was lower than that in the binary system where l-limonene was present as a pure solute in CO{dollar}sb2{dollar}. The solubility of l-carvone was at a similar value as that in the binary system.; The extraction of carvone and limonene from spearmint leaves using SC-CO{dollar}sb2{dollar} was performed. The dynamic extraction behavior was presented by showing the concentration history of oil components in the bulk CO{dollar}sb2{dollar} with time extraction.; The extraction behavior of essential oil components from spearmint leaves was predicted using mathematical models. When using a mass transfer model, the optimized intraparticle effective diffusivity as a model parameter was much smaller than the effective diffusivity calculated by an empirical diffusivity estimation method and general diffusivity values in supercritical CO{dollar}sb2{dollar} in the literature. The desorption kinetic model in which the releasing rate of solute from the leaf particle matrix is defined by a desorption rate constant gave a fair prediction.; The pretreatment of lignocellulose using SC-CO{dollar}sb2{dollar} alone was not effective for the enzymatic hydrolysis. It was effective only when lignocellulose was soaked with water prior to the SC-CO{dollar}sb2{dollar} pretreatment. The presence of water at a high temperature had major effects on the pretreatment effectiveness. However, SC-CO{dollar}sb2{dollar} contributed to increasing 10% of the total reducing sugar yield.