Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-V-10composition (methyl esters, mono-, di and triglycerides content) was determined by GCanalysisusing tricaprin as internal standard.Results and discussionIn the performed reaction conditions (140°C, 24 hours, 15% wt of catalyst respect to oil,oil:methanol molar ratio equal to 1:10) the potassium silicate shows the highest oleic acidconversion value (93%), followed by the sodium silicate with a conversion value of 88%.Among the zeolites, the K-Silicalite-1 allows to reach the 50% of conversion, with respect the20% of the Fau-X. To achieve a conversion value comparable with the basic catalyst, the acidzeolites require the increasing of the temperature and methanol amount. These results suggestthat the faster reaction rate achieved using silicates could be due to the presence of base siteson amorphous surface of these catalysts. At the same time, the weak acid sites also present onsilicates surface allow to achieve an acid esterification of the free fatty acid, avoiding the soapformation.In the transesterfication of an olive oil with the following fatty acid composition: 74% ofoleic acid, 12,3% of palmitic acid, 3,5% of stearic acid and 7,7% of linoleic acid and 2,5% ofmyrisitc acid, the selectivity of the silicates catalyst has been compared with that of theconventional alkaline homogeneous catalyst KOH. The sodium silicate catalyst shows ahigher selective towards the long chain fatty acids (Figure 1). The maximum content ofmethyl palmitate, methyl oleate and methyl linoletae (C18) increases and no myristic acidconversion occurs at the end of the reaction catalyzed by the sodium silicate.80Finally, some of the most important70Sodium SilicateKOHparameters of biodiesel quality60(monoglyceride, diglyceride and50403020triglyceride content, total glycerol leveland acid value) for reactions using eachcatalyst have been evaluated. For example,100the acid value of the biodiesel produced byFigure 1. Methyl esters content obtained bytransesterification reaction catalyzed by KOH andsodium silicate.Methyl Methyl Methyl Methyl MethylMiristate Palmitate Sterate Oleate Linoleatepotassium silicate is equal to 0.23 mgKOH/g (0.5 mg KOH/g is the maximumvalue defined by the European UnionDraft Standard prEN 14214).Methyl Esters C ontent [% wt]References1. F. Ma, M.A. Hanna, Bioresour. Technol., 70 (1999) 1-15.2. B. Freedman, E.H. Pryde, T.L. Mounts, J. Am. Oil Chem. Soc., 61 (1984) 1638-1643.476