Preparation of supercritical fluid extraction using dry ice and exploration of equation of state to predict the operating conditions

Abstract

Supercritical Fluid Extraction (SFE) is the process of separating a soluble material from an insoluble residue using the supercritical fluid as the extracting solvent. This extraction is the most effective and efficient way to extract valuable constituent in botanicals. Supercritical carbon dioxide is a fluid state of carbon dioxide that is held above its critical temperature (Tc=31.1 °C) and critical pressure (Pc=73.8 bar). It is a natural solvent and has been widely used in practical applications because of its non-toxic, non-flammable, plentiful, inexpensive and tunable of solvent properties by just adjusting temperature and pressure. Due to carbon dioxide’s relatively low critical temperature, it is especially suitable for processing thermo-labile compounds, such as pharmaceutical and nutraceutical compounds. Nevertheless, the cost of SFE equipment is outside the range of most of our finances. A high-pressure intensifier pump is used to achieve the required pressure. In this research, the supercritical CO2 condition was achieved by other alternative using dry ice. It is a solid phase of CO2 when frozen. At standard temperature and pressure (STP), CO2 usually behaves as a gas. If dry ice is put in an enclosed vessel, it will sublimate to become a gas and the pressure will increase depending on the mass of dry ice until the desired pressure (supercritical pressure) is achieved. By supercritical CO2 from dry ice, the equipment of SFE will be simpler and cheaper. It is also suitable for batch operation to get equilibrium data of supercritical fluid extraction. Exploration of Equation of State, such as Ideal Gas, van der Waals, Redlich Kwong, Soave-Redlich Kwong and Peng Robinson, was done to predict the operating condition (supercritical pressure and temperature). In this research, by comparing the calculated and the experimental data, Peng Robinson is considered as the most appropriate Equation of State.