Transesterification of Vegetable Oils with Ethanol and Characterization of the Key Fuel Properties of Ethyl Esters

George Anastopoulos, Ypatia Zannikou, Stamoulis Stournas and Stamatis Kalligeros
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George Anastopoulos: National Technical University of Athens, School of Chemical Engineering, Laboratory of Fuels Technology and Lubricants, Iroon Polytechniou 9, Athens 15780, Greece
Ypatia Zannikou: National Technical University of Athens, School of Chemical Engineering, Laboratory of Fuels Technology and Lubricants, Iroon Polytechniou 9, Athens 15780, Greece
Stamoulis Stournas: National Technical University of Athens, School of Chemical Engineering, Laboratory of Fuels Technology and Lubricants, Iroon Polytechniou 9, Athens 15780, Greece
Stamatis Kalligeros: Hellenic Organization for Standardization, Technical Committee 66, 67 Prevezis Street, Athens 10444, Greece

Energies, 2009, vol. 2, issue 2, 1-15

Abstract: The transesterification reactions of four different vegetable oils (sunflower, rapeseed, olive oil and used frying oil) with ethanol, using sodium hydroxide as catalyst, were studied. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil (0.25 – 1.5%), the molar ratio of ethanol to oil (6:1 – 12:1), and the reaction temperature (35 – 90 °C) were studied for the conversion of sunflower oil to optimize the reaction conditions in both stages. The rest of the vegetable oils were converted to ethyl esters under optimum reaction parameters. The optimal conditions for first stage transesterification were an ethanol/oil molar ratio of 12:1, NaOH amount (1% wt/wt), and 80 °C temperature, whereas the maximum yield of ethyl esters reached 81.4% wt/wt. In the second stage, the yield of ethyl esters was improved by 16% in relation with the one-stage transesterification, which was obtained under the following optimal conditions: catalyst concentration 0.75% and ethanol/oil molar ratio 6:1. The fuel properties of the esters were measured according to EN test methods. Based on the experimental results one can see that the ethyl esters do not differ significantly from methyl esters. Moreover, the results showed that the values of density, viscosity, and higher heating value of ethyl esters were similar to those of automotive and heavy duty engine diesel fuel. However, the CFPP values were higher, which may contribute to potential difficulties in cold starts. On the other hand, the flash points, which were higher than those of diesel fuel constituted a safety guarantee from the point of view of handling and storage.

Keywords: transesterification; biodiesel; ethanol; sodium hydroxide (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2009
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (24)

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