Biofuel that Keeps Glycerol as Monoglyceride by 1,3-Selective Ethanolysis with Pig Pancreatic Lipase Covalently Immobilized on AlPO4 Support

Abstract

By using pig pancreatic lipase (EC 3.1.1.3 or PPL) as a biocatalyst, covalently immobilized on amorphous AlPO 4 support, a new second generation biodiesel was obtained in the transesterification reaction of sunflower oil with ethanol. The resulting biofuel is composed of fatty acid ethyl esters and monoglycerides (FAEE/MG) blended in a 2:1 molar ratio. This novel product, which integrates glycerol as monoacylglycerols (MG) into the biofuels composition, has similar physicochemical properties as conventional biodiesel and also avoids the removal step of the by-product by washing of the biodiesel with water. Immobilization of PPL was achieved by covalent attachment of the ε-amino group of the lysine residues of PPL with the aldehyde groups of p-hydroxybenzaldehyde linked on a hybrid organic-inorganic functionalized AlPO 4 surface. With this procedure, the PPL biocatalyst was strongly fixed to the inorganic support surface (94.3%). Nevertheless, the efficiency of the immobilized enzyme was relatively lower compared to that of the free PPL, but it showed a remarkable stability as well as a great capacity of reutilization (25 reuses) without a significant loss of its initial OPEN ACCESSEnergies 2013, 6 3880 catalytic activity. Therefore, this enzymatic method allows the production of a biodiesel which integrates the glycerol, allows a more efficient fabrication method and minimizes the waste production as compared to the conventional alkali-catalyzed process.

Production of a Biofuel that Keeps the Glycerin as Monoglycerides by Using Supported KF as Heterogeneous Catalyst

“…Thus, reactions were carried out with 0.8 g of 10 wt% supported KF on the three inorganic solids, Al 2 O 3 , ZnO and MgO, at 65 ºC reaction temperature with 12 mL of sunflower oil (32 cSt, kinematic viscosity) and 2.43 mL of methanol. According to the results, with all the three KF supported catalysts studied, under the indicated experimental conditions, were obtained similar results as those achieved in the enzymatic processes [19][20][21][22][23][24], where instead of glycerol are obtained the monoacylglycerol that are soluble in the FAME mix. The experimental conditions currently applied were clearly softer than those required for the production of conventional biodiesel with supported KF catalysts [29][30][31][32][33][34][35][36].…”

“…By difference and respect to the internal standard (cetane), the amount of triglycerides (TG) which has not reacted, is calculated. The Conversion includes the total amount of triglyceride transformed (FAME + MG + DG) in the methanolysis process and Selectivity makes reference to the relative amount of FAME + MG obtained, which exhibit retention times (RT < 25) similar to conventional diesel fuel [20,21,27].…”

“…As carrier gas helium is used, with a flow of 1.5 ml/min, it has been applied a heating ramp from 50 °C to 200 °C at a rate of 7 °C/min, followed by another ramp from 200 °C to 360 °C at a rate of 15 ºC/min, maintaining the oven temperature at 360 °C for 10 minutes using as internal standard n-hexadecane (cetane) to quantify the content of methyl esters and glycerides (-mono, di and triglycerides) with the help of some commercial standard fatty acid esters, respectively. This method allows us to obtain a complete analysis of the sample in a single injection and in a time not higher than 65 minutes, which simplifies the process and increases the speed of analysis [19][20][21][22][23][24].…”

“…In this respect it is interesting to point out in this respect that according to recent studies the presence of MG enhances the lubricating properties of the biofuel [25,26]. So far this process is being developed not only with PPL but also with some microbial lipases, both in free and immobilized forms [19][20][21][22][23][24].…”

“…This enzymatic method has shown promising results [19][20][21][22][23][24] in the obtaining of a new biofuel, named Ecodiesel-100, patented by University of Cordoba [22] using pig pancreatic lipase (PPL) to obtain the enantioselective ethanolysis of sunflower oil. This method takes advantage of the 1.3-selective nature of many lipases, which allows stopping the process in the second step of the alcoholysis reaction to obtain a mixture of two moles of FAEE and one MG.…”