Glycerolysis of Soybean Oil with Crude Glycerol Containing Residual Alkaline Catalysts from Biodiesel Production

Abstract

The glycerolysis reaction of soybean oil was evaluated using crude glycerol obtained from the transesterification of soybean oil with methanol, catalyzed by sodium methoxide and sodium hydroxide, without any purification step other than the methanol removal. Crude glycerol with the lower content of remaining inorganic catalyst produced the highest concentration of monoglycerides (about 42%). The effect of the addition of water on the glycerolysis reaction was analyzed, evidencing a low formation rate of products in the first stages of the reaction due to the transformation of the inorganic catalyst to soaps, which are weaker bases. The sample of crude glycerol that led to the best results was evaluated at several temperatures. It was observed that the reaction with crude glycerol exhibits a lower formation rate of monoglycerides at low temperatures (160 and 180°C) compared with the reaction with pure glycerol and catalyzed with NaOH. This behavior was explained by the lower activity of the soaps present in the crude glycerol respect to the inorganic base. Above 200°C the reaction is very fast and the monoglycerides formed are consumed to produce diglycerides.

Diglyceride-rich oils from glycerolysis of edible vegetable oils

“…Glycerolysis of TG toward DG has been shown to be promoted by enzymes [13,14,11], ionic liquids [15], alkali metal hydroxides, alkoxides and hydrides [16][17][18]. Enzymatic glycerolysis entails problems derived from the high cost of the enzymes and from the low reaction temperature that might not produce the 1,3-DG isomer in high yields.…”

Síntesis y Caracterización de Catalizadores tipo Hidrotalcita Dopados con Fe³+ para la Producción de Monoglicéridos y Diglicéridos de Aceite de Soya

“…Actualmente la reacción de glicerólisis para la formación de glicéridos es llevada a cabo usando catalizadores homogéneos (Yesinowski et al, 1988;Echeverri et al, 2011). El uso de catalizadores heterogéneos es de importancia en la búsqueda de mejores selectividades y facilidades a la hora se separar o aislar los productos.…”

“…Comercialmente los métodos para la obtención de monoglicéridos y diglicéridos parten de la reacción de glicerólisis entre un aceite vegetal o metil éster con glicerina, utilizando temperaturas entre los 220-260°C, conjuntamente con altas velocidades de agitación y la adición de catalizadores como el NaOH, KaOH, o el Ca(OH)2 (Echeverri et al, 2013), sin que se logre una selectividad significativa hacia alguno de los productos finales. Se conocen entre 15-20 catalizadores (Sonntag 1982;Echeverri et al, 2011) en la producción glicéridos. Dentro de estos las enzimas han demostrado ser catalizadores muy efectivos y selectivos hacia monoglicéridos, pero su uso a nivel industrial requiere solventes costosos y sistemas de reacción que no favorecen una aplicación práctica de esta tecnología (Noureddini et al, 2004).…”

Spectroscopic Studies of the Quality of Fatty Acid Methyl Esters Derived from Waste Cooking Oil

“…Currently, edible vegetable oils [7], e.g., rapeseed, sunflower [8], soybean [9], and palm oils, are most commonly used for biodiesel production. However, the use of these first-generation raw materials does not solve the major problems associated with reduction of CO 2 emissions, but considerably exacerbates food market problems [10][11][12].…”