Conventional and in situ transesterification of castor seed oil for biodiesel production Gina Hincapié, Fanor Mondragón, Diana López ⇑ Institute of Chemistry, University of Antioquia, A.A. 1226, Medellín, Colombia article info Article history: Received 24 July 2010 Received in revised form 14 January 2011 Accepted 18 January 2011 Available online 2 February 2011 Keywords: Castor oil Transesterification Biodiesel In situ transesterification Nuclear magnetic resonance abstract In the present study, biodiesel production from Ricinus communis L. red and BRS-149 nordestina varieties seed oil is reported. Reactions were made through conventional and in situ processes using ethanol and evaluating the addition of n-hexane as co-solvent. The content of ethyl esters was quantified by 1 H NMR. The highest conversions were obtained from crude oil (conventional reaction) after pre-esterification, using ethanol and a molar ratio of alcohol to oil of 60; furthermore, the addition of n-hexane was not sig- nificant on yield. Under these conditions, best conversion was around 95% for both varieties. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The use of vegetable oils derivatives as alternative fuels has in- creased due to the diminishing oil reserves and the environmental consequences of exhaust gases from petroleum-fueled engines [1]. Biodiesel is an alternative fuel produced by transesterification of oils. This reaction consists of transforming triglycerides into fatty acid alkyl esters in the presence of an alcohol, such as methanol or ethanol, and a catalyst, with glycerol as co-product (Fig. 1) [2,3]. The use of methanol is more common than ethanol because its low cost, but several researches have started to investigate bio- diesel production or optimization using ethanol derived from sug- arcane [4,5]. Some advantages of biodiesel compared with petrodiesel are that it is biodegradable, non-toxic; it is produced from renewable sources and contains insignificant amounts of sul- fur. Nevertheless, cold flow properties, NO x emissions and high costs are features that have to be overcome [6]. Edible oils like soybean, rapeseed, sunflower and palm oil are being used for the production of biodiesel. However, in the last few years, there has been a major concern about the use of these oils for transportation purposes [1]. To overcome this problem, there are several non-edible oil seed species which could be used as a source for biodiesel production, among those, Ricinus commu- nis L. and Jatropha curcas have considerable potential [7–9]. Castor oil, extracted from the seeds of R. communis L. plant (also known as castor bean, castor oil plant, higuerilla, mamona), is a viscous, pale yellow, non-volatile and non-drying oil. Opposed to other vegeta- ble oils it is characterized for its indigestibility, partial solubility in alcohol, high hygroscopicity and high viscosity [10,11]. Like other vegetable oils, castor oil is constituted mainly by tryglice- rides which consist of three fatty acids and one molecule of glyc- erol. The fatty acids of this oil consist of approximately 80–90% of ricinoleic acid (12-hydroxy-cis-octadec-9-enoic acid), 3–6% lino- leic acid, 2–4% oleic acid and 1–5% saturated fatty acids. Due to this particular chemical composition, castor oil is a raw material in great demand by the pharmaceutical and chemical industry [12]. Its use as fuel for internal combustion engines, however, can be- come complicated because of its extremely high viscosity and high water content; biodiesel derived from castor oil exhibit much high- er viscosities than those of more conventional biodiesels, and it can be used in current diesel engines in admixture with fossil diesel or with less viscous biodiesels [13–15]. Nevertheless, the presence of ricinoleic acid, which is a fatty acid that contains both a double bond and a hydroxyl group, can afford an increase in lubricity as compared to normal vegetable oils and becomes a prime candidate as additive for diesel fuel [13,16,17]. Crude castor oil quality deteriorates gradually due to improper handling and storage conditions. An improper handling would cause the water content increase, and exposition to air and light for long time would increase the concentration of free fatty acids (FFA). A high FFA content (>1% w/w) will generate soap formation and the separation of products will be very difficult, and as a result, a low yield will be obtained. The acid-catalyzed esterification of the oil is an alternative, but is much slower than the base-catalyzed transesterification reaction [1,18]. Therefore, an alternative process 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.01.027 ⇑ Corresponding author. Tel.: +57 4 2196613; fax: +57 4 2196565. E-mail address: dplope@gmail.com (D. López). Fuel 90 (2011) 1618–1623 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel