Published: July 12, 2010 r2010 American Chemical Society 2544 dx.doi.org/10.1021/ie1005806 | Ind. Eng. Chem. Res. 2011, 50, 2544–2547 ARTICLE pubs.acs.org/IECR Reaction Kinetic Study of Biodiesel Production from Fatty Acids Esterification with Ethanol L. D. T. C ^ amara* ,† and D. A. G. Aranda ‡ † Departamento de Engenharia Mec ^ anica e Energia (DEMEC), Instituto Polit  ecnico da Universidade do Estado do Rio de Janeiro (IPRJ- UERJ), Nova Friburgo-RJ, Brazil ‡ Departamento de Engenharia Química, Laborat orio de Tecnologias Verdes (GreenTec), Escola de Química da Universidade Federal do Rio de Janeiro (EQ-UFRJ), Rio de Janeiro-RJ, Brazil ABSTRACT: The kinetic of fatty acids esterification with ethanol utilizing niobium oxide catalyst (79.8% of N b O 5 and 19.6% of water) for the production of biodiesel was analyzed through a reversible kinetic modeling for the determination of the kinetic and thermodynamic data of the reactions. The reactions were carried out with three kinds of fatty acids (stearic, palmitic, and lauric) with anhydrous and hydrated ethanol. From the kinetic study it was possible to calculate the theoretical equilibrium data which were compared to experimental data of each reaction. From the comparison between the experimental and calculated conversions it was possible to analyze the accuracy of the estimations, providing a good way to apply statistical treatments in the improvement of the kinetic and thermodynamic properties calculated. 1. INTRODUCTION The production of biodiesel from raw materials that can be used for food is not the best way to generate and develop renewable energy. 1 Therefore, the alternative sources, such as the fatty acids (byproduct), are a good option as these materials lead to low cost biodiesel production without interfering in food production. 2 In the literature there are many works related to research and development of technologies for the conversion of fatty acids into biodiesel. 3-20 There are researches where the main objective is the conversion of pure fatty acids, 3-11 and others in which the fatty acids are part of the oil phase medium. 12-20 In the latter case sometimes it is necessary to convert the fatty acids to reduce the problems of saponification which reduce the yield of the reaction of transesterification by alkali. In the reactions of esterification for the production of biodiesel a great variety of catalyst are found, such as sulfuric acid, 4,5,12,13 acid resins, 3,7,9-11 acid polymers 17,18 and others (tungstophos- phoric acid, 14,16 tungstosilicic acid, 16 niobium oxide (Nb 2 O 5 ), 19 zinc hydroxide nitrate (Zn 5 (OH) 8 (NO 3 ) 2 3 2H 2 O) 8 and Fe 2 - (SO4) 3 /C). 6 The most common is sulfuric acid and acid resins used in the catalysis of such reactions. The use of niobium oxide is a promising possibility observed in a previous work. 19 In the work of Aranda et al. 19 different catalysts were tested and com- pared in the esterification of a mixture of fatty acids residue. They observed a better performance of the polynaphthalene sulfonic acid and the niobium oxide (Nb 2 O 5 ) if compared to that of a zeolite catalyst. The authors also observed higher conversion when utilizing the methanol if compared to using the ethanol. From the literature can be seen works related to the kinetic modeling studies of the esterification reactions of fatty acids for the production of biodiesel. 4,6,10,11,19,20 In the work of Berrios et al. 4 the authors applied a reversible reaction kinetic model that is first order in the forward direction and second order in the reverse direction. They studied the esterification of free fatty acids in sunflower oil with methanol and sulfuric acid. They determined the activation energies by the Arrhenius equation, observing a decrease in the activation energy with an increase in the catalyst concentration. Tesser et al. 10 applied a detailed kinet- ic/equilibrium model that takes into account different aspects of the esterification of oleic acid with soybean oil with methanol and acid exchange resins. The developed kinetic model was able to correctly represent the experimental data both as a function of temperature and of catalyst concentration. In the work of Aranda et al. 19 the authors applied two different kinetic models to study the esterification of fatty acids with polynaphthalene sulfonic acid, niobium oxide, and zeolite catalyst utilizing ethanol and methanol. They studied an empiric heterogeneous model and a homogeneous model. The parameters for both models were obtained utilizing the Statistical software and applying nonlinear regression. The authors observed that the homogeneous model is more adequate to represent the esterification with methanol, whereas the heterogeneous model better represents the ester- ification with ethanol. This work presents the study of the kinetics of fatty acid esterification with ethanol and niobium oxide catalyst (N b O 5 ) for the production of biodiesel. A reversible kinetic model was assumed in the determination of the kinetic parameters of three different kinds of pure fatty acids (stearic, palmitic, and lauric) with anhydrous and hydrated ethanol. From the experimental equilibrium data, it was possible to analyze the accuracy of the Special Issue: IMCCRE 2010 Received: March 10, 2010 Accepted: June 24, 2010 Revised: June 23, 2010