Kinetics Of Supercritical Extraction Research Articles

Effect of process parameters on the extraction kinetics of Leptocarpha rivularis DC. in a packed bed extractor using supercritical carbon dioxide

The kinetics of supercritical extraction from L. rivularis stalks using CO2 were studied in terms of temperature (40−60ºC), pressure (18–30 MPa), specific CO2 consumption (30−50 kg/kg d.s.), and particle diameter (0.5−1.1 mm). The extraction yield was found to range from 17.30 to 27.23 g/kg d.s. The highest extraction yield was obtained at 40°C, 30 MPa, 30 kg CO2/kg d.s., and mean particle size of 0.5 mm. The yield increased with pressure and decreased with temperature and particle size (p≤0.05). The diffusion model based on Fick's 2nd law adequately described the cumulative extraction curves, using the effective diffusion coefficient (De) as the adjusted parameter, which ranged between 3.50 and 19.26×10−12 m2/s. The Biot number was estimated, indicating a prevalence of internal control to mass transfer resistance. Additionally, the “apparent solubility” was obtained from the initial slope of the cumulative extraction curves. The extraction yield correlated positively with apparent solubility (p≤0.05) and De coefficient (p≤0.05).

Supercritical CO2 extraction of neutral lipids from dry and wet Chlorella vulgaris NIES 227 microalgae for biodiesel production

This study investigates supercritical CO2 extraction of neutral lipids from Chlorella vulgaris NIES 227 microalgae, for biodiesel applications. While microalgae feedstocks are typically desiccated before extraction, drying is energy intensive and supercritical extraction from wet microalgae would be beneficial in reducing overall energy costs. The effects on the supercritical extraction kinetics, yields and extract composition of the water content of the initial biomass (either 0 or 27 wt%), and of the operating pressure (200 and 250 bar) and temperature (40 and 60 °C) were investigated. The highest total extraction yield (16.16 wt% extract/dry biomass) was obtained with freeze-dried microalgae at 40 °C and 200 bar. However, the extracts obtained at 40 °C and 250 bar were the richest in fatty acids (0.96 g FA/extract), and the extracts obtained at 60 °C and 250 bar had the highest cetane number (69) and oxidative stability (18 h). Water in the initial biomass had a negative impact on total extraction yields (3.89 wt% extract/dry biomass at 200 bar and 40 °C) and led to increased pigment extraction, but results suggest the presence of water may promote the extraction of fatty acids, in particular monounsaturated ones, highly desirable for biodiesel. In comparison, Soxhlet extraction with hexane was found to have higher lipid yields (31.20 wt% extract/dry biomass) than any of the tested supercritical conditions, but more pigments were also extracted alongside, having a negative impact on oxidative stability. All the extracts obtained with supercritical CO2 and Soxhlet hexane met biofuel European standards for density, cetane numbers and iodine values.

Grape by-products: extraction of polyphenolic compounds using supercritical CO2 and liquid organic solvent – a preliminary investigationSubproductos de la uva: extracción de compuestos polifenólicos usando CO2 supercrítico y disolventes orgánicos líquidos – una investigación preliminar

This research focussed on the exploitation of grape by-products as a source of polyphenolic compounds, which are of interest to the food, pharmaceutical and cosmetic industries. In particular, two substrates were tested: Pinot Noir grape skins and grape seeds. Pinot Noir grape skins were extracted by supercritical CO2 added with ethanol as modifier at constant temperature (45 °C) and at variable pressure (200, 300, 400 or 500 bar). The supercritical extraction kinetics of polyphenolic compounds was obtained. Grape seeds were extracted by combining supercritical (at 40 °C and 500 bar and using CO2 or CO2 added with ethanol as modifier) with liquid ethanol extraction. The supercritical technique seemed not to be really effective in extracting polyphenolic compounds; it can be anyway utilized to selectively extract grape seed oil by avoiding any solvent contamination of the matrix which can be further extracted for the recovery of polyphenolic compounds by means of liquid organic solvent.