Hydrolysis of Vegetable Oils in Sub- and Supercritical Water

Abstract

Water, in its subcritical state, can be used as both a solvent and reactant for the hydrolysis of triglycerides. In this study, soybean, linseed, and coconut oils were successfully and reproducibly hydrolyzed to free fatty acids with water at a density of 0.7 g/mL and temperatures of 260−280 °C. Under these conditions the reaction proceeds quickly, with conversion of greater than 97% after 15−20 min. Some geometric isomerization of the linolenic acids was observed at reaction temperatures as low as 250 °C. Reactions carried out at higher temperatures and pressures, up to the critical point of water, produced either/or degradation, pyrolysis, and polymerization, of the oils and resultant fatty acids.

Hydrolysis of corn oil using subcritical water

“…1,5 It was verified that to low temperatures, the speed and the yield of the hydrolysis reaction are both practically null. Figure 1 and Table 1 illustrates a typical profile of triglycerides (TG) obtained of non hydrolyzed corn oil, while Figures 2 to 3 illustrate the variation of the chromatographic profile of a hydrolyzed corn oil as a function of the temperature.…”

“…17, No. 1,2006 (ammonium chlorite, methanol, sulfuric acid) are added and the contents of the capped tube heated in water bath (temperature 90 °C) for 10 min, being after words cooled in ice bath and later added 5 mL of hexane and 10 mL of water. A sample is taken from the clear upper layer (usually 1 μL) for GC analysis of FAMEs.…”

“…[1][2][3][4] Many studies have been done exploring the use of water in conditions sub and supercritical to promote organic synthesis reactions, some of those would be alkyl-aromatics oxidation, oxidation of methane in hydrothermal systems, dehydration of alcohol, and organic transformations catalyzed by metals. 1 Another option is the employment of subcritical water as both solvent and reagent for triglycerides hydrolysis. 5 Some studies utilizing pressures higher than 2 MPa and temperature over 250 °C, demonstrate the viability of its use without the need of using either acidic or alkaline catalysts.…”

An investigation of reaction pathways of hydrothermal liquefaction using Chlorella pyrenoidosa and Spirulina platensis

“…It was reported that the main compositions of the glycerol degradation were methanol, ethanol, acrolein, allyl alcohol, formaldehyde, propionaldehyde, acetaldehyde and gas products. In terms of fatty acids, they have high stability in subcritical water [40][41][42]. The production of fatty acids with higher molecular weight via hydrolysis of lipids may be favored in subcritical water without alkaline conditions.…”

Biocombustíveis a partir de óleos e gorduras: desafios tecnológicos para viabilizá-los

“…A água em estado supercrítico apresentou bons resultados, além de ser considerada uma rota limpa, pois não utiliza solvente nem catalisadores que podem ser nocivos ao meio ambiente. 44,45 Foi ainda reportado o uso de CO 2 supercrítico como solvente, sendo observado que este possui as mesmas vantagens da água supercrítica e ainda facilita o processo de separação dos ácidos graxos dos outros produtos. 46 …”