Abstract
Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification with ethanol (also called ethanolysis) in order to substitute fossil fuels. In this work, we were interested in the transesterification reaction of sunflower oil with ethanol, which leads to ethyl esters, used to date for applications principally in food and cosmetic industry. To open the application field to biofuels (to substitute current fuels resulting from fossil resources), the process efficiency has to be developed to be economically profitable. The batch reaction of vegetable oil ethanolysis was transposed to a micro-scaled continuous device (PFA tube of 508 μm internal diameter), inducing better heat and mass transfer. Study of the influence of the operational conditions (reactants flow, initial ethanol to oil molar ratio, temperature. . .) revealed the favourable reaction parameters necessary to reach high conversions and yields. In these conditions, it is possible to acquire kinetics data at the first seconds of the reaction, which was not feasible in a conventional batch process. These data were used to model occurring phenomena and to determine kinetic constants and transfer coefficients. The model was subsequently used to simulate reactions with other operational conditions. To acquire these data in microreactors, an on-line analysis method by Near InfraRed (NIR) spectroscopy was developed by using gas chromatography as a reference method. PLS models were then set up to quantify on-line the major compounds contents during the reaction.
Highlights
Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification (Demirbas, Karslioglu, 2007; Encinar et al, 2007) with an alcohol in order to substitute fossil fuels
Different analytical procedures (gas chromatography (Mittelbach, 1993; Knothe, 2001), high performance liquid chromatography (Holcapek et al, 1999), Fourier transform infrared spectroscopy (Zagonel et al, 2004; Mahamuni, Adewuyi, 2009) have been developed to off-line monitor the composition of reaction mixtures obtained during or after transesterification of vegetable oils with ethanol containing free fatty acid (FFA), ethyl esters, monoglycerides, diglycerides, triglycerides and glycerol
Only a few techniques such as ultrasonicationassisted spray ionization mass spectroscopy (Chen et al, 2010) or mid-infrared spectroscopy (Trevisan et al, 2008) can on-line monitor organic reactions. Faced to this lack of analysis techniques, we developed an innovative method using Near Infrared (NIR) spectroscopy to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol in microreactors
Summary
Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification (Demirbas, Karslioglu, 2007; Encinar et al, 2007) with an alcohol in order to substitute fossil fuels. Different analytical procedures (gas chromatography (Mittelbach, 1993; Knothe, 2001), high performance liquid chromatography (Holcapek et al, 1999), Fourier transform infrared spectroscopy (Zagonel et al, 2004; Mahamuni, Adewuyi, 2009) have been developed to off-line monitor the composition of reaction mixtures obtained during or after transesterification of vegetable oils with ethanol containing FFA, ethyl esters, monoglycerides, diglycerides, triglycerides and glycerol. These techniques are long to handle, unreliable and expensive methods. The developed models were validated by comparison with the GC data
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