(617fq) Regeneration of Fatty Acid-Adsorbed γ-Alumina Using Supercritical Methanol

Vegetable oil is both a major source of nutrition and an important fuel source for production of biodiesel. Triglycerides (TG), diglycerides (DG), monoglycerides (MG), free fatty acids (FFA), and other impurities are components of most vegetable oil. Deacidification, which refers to removal of FFA in vegetable oil, is an important refining process for reducing the high level of FFA that may promote rancidity of oils. Common deacidification method is neutralization with alkali, generally sodium hydroxide solution. However, neutralization via the alkaline method is not suitable for vegetable oils that contain a high concentration of FFA because saponification of vegetable oil due to alkaline treatment results in high loss of oils during the washing step. It is reported that the refining loss reaches three times the FFA content during the deacidification of soybean and cottonseed oil. Adsorption of FFA using activated alumina could be an alternative method of the alkaline neutralization. A chromatographic process using activated alumina at room temperature without physical contact between the oils and alkaline reagent leading to decreased loss of oils has been proposed. However, regeneration of spent activated alumina is energy intensive process because chemisorption of carboxylic acids on alumina can occur via surface esterification with hydrated alumina surfaces. In this study, we introduce a novel method for regeneration of the fatty acid-adsorbed γ-alumina using supercritical methanol. The adsorbed fatty acid converted to fatty acid methyl ester (FAME) through transesterification reaction. This method is based on a difference in the affinity of a fatty acid and the corresponding fatty acid methyl ester (FAME) for γ-alumina. Palmitic acid was selected as a model fatty acid. Batch-type reactors were used to investigate the effect of the operating parameters (temperature, methanol to γ-alumina weight ratio, and reaction time) on supercritical methanol regeneration. Reaction product was analyzed by gas chromatography. Almost all of the adsorbed palmitic acid was desorbed at temperatures above 300 â??, or when the weight ratio of methanol to γ-alumina was higher than 75:1, and/or if the reaction time was longer than fifteen minutes. The crystal structure and BET surface area of γ-alumina was unchanged after supercritical methanol regeneration. The developed technique requires relatively lower operating temperature, is eco-friendly, and generates fuel, although the process is more complex than the thermal regeneration method.