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Fuel 89 (2010) 650–658

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Fuel
journal homepage: www.elsevier.com/locate/fuel

Optimization of the reaction parameters for fast pseudo single-phase transesterification of sunflower oil
Abraham Casas, Carmen Maria Fernández, Maria Jesús Ramos *, Ángel Pérez, Juan Francisco Rodríguez
Department of Chemical Engineering, Institute for Chemical andEnvironmental Technology (ITQUIMA), University of Castilla-La Mancha, Avd. Camilo José Cela s/n 13071, Ciudad Real, Spain

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Transesterification of sunflower oil with methanol was carried out using potassium hydroxide and methoxide as catalysts and MTBE as cosolvent. The aim of this work was to study and optimize the reaction parameters. Chosen parameters werereaction time, catalyst amount and methanol amount (expressed as catalyst-to-oil and methanol-to-oil molar ratios, respectively). The response variables were methyl ester content (ME) and acid value (AV) due to their relationship with the completion and yield reaction, respectively. A factorial plus composite design was developed to carry out the optimization. From this design, several quadraticmodels have been used to fit the experimental data. All the factors studied had a positive influence on methyl ester content and acid value, except the methanol amount on acid value. For methoxide catalyst, optimum values were 0.235 catalyst to oil molar ratio, 12 methanol to oil molar ratio and 5 min reaching 99 wt.% ME and 0.20 mg KOH/g of AV. Ó 2009 Elsevier Ltd. All rights reserved.

Articlehistory: Received 23 February 2009 Received in revised form 25 June 2009 Accepted 5 August 2009 Available online 22 August 2009 Keywords: Biodiesel Pseudo single-phase Cosolvent Response surface Factorial design

1. Introduction As supply of fossil fuels is limited while energy demand continues to rise, research is increasingly directed towards alternative renewable fuels of limitless durationand smaller environmental impact than the traditional ones. Biodiesel, an alternative diesel fuel, is made from renewable biological sources such as vegetable oils and animal fats. It is biodegradable and non-toxic, has low emission profiles and so is environmentally beneficial [1]. Recently, the demand of biodiesel has increased due to high petroleum price and the development of government measureslike EU Directive 2003/30/EC on the promotion of the use of biofuels or other renewable fuels for transport. In a transesterification or methanolysis reaction, one mole of triglyceride reacts with three moles of methanol to form one mole of glycerol and three moles of the respective fatty acid methyl ester. The process is a sequence of three reversible reactions, in which the triglyceride moleculeis converted step by step into diglyceride, monoglyceride and glycerol. In order to shift the equilibrium to the right, methanol is added in an excess over the stoichiometric amount in most commercial biodiesel production plants [2]. After the reaction, the glycerol is separated by settling or centrifugal sedimentation and is purified to be used in its traditional applications (for instancepharmaceutical and cosmetics

* Corresponding author. Tel.: +34 926 295 300; fax: +34 926 295 242. E-mail address: MariaJesus.Ramos@uclm.es (M.J. Ramos). 0016-2361/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2009.08.004

industries) or in its recently developed applications (polymers, lubricants, etc.) [3]. Generally, the transesterification reaction is catalysedby a basic or an acid catalyst. Basic catalysis is by far the most commonly used reaction type for biodiesel production because high conversion under mild conditions is reached in comparatively short reaction times [2,4,5]. However, basic catalysis produces soaps by neutralizing the free fatty acids in the oils or triglycerides and methyl esters saponification. Heterogeneous catalysts avoid this...