Hydrolysis, esterification and glycerolysis of lipids in supercritical carbon dioxide media.

摘要

Hydrolysis, esterification and glycerolysis reactions were conducted in supercritical carbon dioxide (SC-CO2) media with the overall objective of enhancing fundamental knowledge about enzymatic and non-enzymatic lipid reactions conducted in SC-CO2 media while providing key processing parameters and kinetic models for process design.;Reactions were conducted in a stirred batch reactor (for glycerolysis, esterification and hydrolysis) and in a continuous packed-bed enzymatic reactor (for hydrolysis). Samples were collected as a function of time and the concentrations of monoacylglycerol (MAG), diacylglycerol (DAG), free fatty acids (FFA) and triacylglycerol were determined using thin layer chromatography - flame ionization detector or supercritical fluid chromatography system. Tested processing parameters for batch reactions were: pressure (10-30 MPa), temperature (170-250°C), supercritical media (CO2 or N2) and initial reactant concentrations (glycerol/oil/water, glycerol/oleic acid, oil/water). For enzymatic reactions, SCCO2 flow rate, enzyme load and temperature were the investigated parameters.;Pressure had no impact on the maximum rate of MAG formation (MAG max) obtained during esterification but decreased MAGmax during glycerolysis and delayed FFA production during non-enzymatic hydrolysis. High temperatures increased MAGmax during esterification while supercritical media did not have any effect on MAGmax during glycerolysis and esterification or on the maximum rate of FFA formation (FFAmax) during hydrolysis. An increase in initial water concentration increased MAG max during glycerolysis and FFAmax during hydrolysis while an increase in initial glycerol content increased MAGmax during esterification.;For enzymatic hydrolysis, conversion rate was improved with enzyme load and SC-CO2 flow rate but unaffected by temperature. More studies are therefore required to determine the true optimum for enzyme load and flow rate.;Extensive kinetic modeling taking into account all possible reaction steps for the batch reactions was performed and rate constants were established. Research findings lead to a better understanding of the complex mechanism involved in each reaction while providing the necessary data for optimal process design targeting the production of MAG, DAG or FFA. This research contributes to the development of novel environmentally friendly approaches to value-added processing of oilseeds such as canola, an important local agricultural commodity.