CHEMICAL ENGINEERING TRANSACTIONS VOL. 32, 2013 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Chief Editors: Sauro Pierucci, Jiří J. Klemeš Copyright © 2013, AIDIC Servizi S.r.l., I SBN 978-88-95608-23-5; I SSN 1974-9791 Biodiesel Production from Supercritical Ethanolysis of Soybean Oil Fábio P. Nascimento a , Alcides R. G. Oliveira b , Márcio L. L. Paredes a , André L. H. Costa a , Fernando L. P. Pessoa* b a Instituto de Química, Universidade do Estado do Rio de Janeiro, Campus Maracanã, P H L C, S. 310, Rua São Francisco Xavier, 524, Maracanã, Rio de Janeiro, RJ, Brazil, Cep 20550-900 b Escola de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, C T, Bloco E, S. 209, Av. Athos da Silveira Ramos, 149, Ilha do Fundão, Rio de Janeiro, RJ, Brazil, Cep 21941-909 pessoa@eq.ufrj.br The study of biodiesel production in supercritical media is of interest because compared with conventional technologies it does not need catalysts and, therefore, no negative effects are noticed due to the presence of water. In this context, the present work studied the conversion of soybean oil into biodiesel through a transesterification reaction without catalyst with supercritical ethanol in a batch reactor. The reaction time was 15 minutes, and the initial alcohol:oil molar ratio was 39:1. The reactions were carried out in the temperature range of 260 to 300 °C and pressure over 100 bar. The conversion was determined with three different analyses: refractive index, density and dynamic viscosity. All three equipments used to analyze the conversion were calibrated with a soybean biodiesel with purity of 98 %. The results show significant conversion of oil into biodiesel in the temperature of 300 °C. The production of biodiesel decreases as the temperature drops and for the temperature of 260 °C the conversion is negligible. As an attempt to improve the conversion at 260 °C CO2 was added as a co-solvent to the system in a mass ratio of 0.05:1, 0.1:1 and 0.22:1 (CO 2 :alcohol). The results show that the presence of CO 2 did not improved conversion at temperature of 260 °C. 1. Introduction Biodiesel is a renewable fuel produced from biological oils and fats, which has many characteristics of a promising alternative energy resource. It has properties similar to ordinary diesel fuel made from crude oil and can be used in conventional diesel engines (Baroutian et al., 2008). Nowadays, the most common process for biodiesel production is the transesterification, in which fatty acid ethyl esters (FAEE) are obtained by reacting triglycerides with ethanol, in the presence of a strong base used as a catalyst. The reaction yields glycerol as a by-product. The triglycerides come from a variety of oils, including soybean, sunflower, corn and other oils (Santos et al., 2010). These processes are time consuming and the separation of the product and the catalyst is complicated, resulting in high production costs and energy consumption (Han et al., 2005). Enzymes (free or immobilized) can be used as an alternative catalyst, but the main drawbacks of this technology are the high cost of enzymes and their inhibition due to the presence of the alcohol (Magalhães et al., 2010). Saka and Kusdiana (2001) proposed the non-catalytic transesterification of vegetable oils using supercritical alcohols as an alternative for biodiesel production. The experimental results shown that the process is not sensitive to free fatty acids and water contents. The authors observed high reaction rates at conditions close to the critical properties of the alcohol. However, the reaction requires elevated temperature and pressure, which are not viable in industry. To reduce the expected high operating cost, supercritical CO2 can be added as a co-solvent to increase the mutual solubility of ethanol and vegetable oil at low reaction temperatures (Han et al., 2005). The co-solvent can also decrease the critical point of ethanol allowing the supercritical reaction to be carried out under lower temperatures (Pak and Kay, 1972). 829