—Biodiesel is a potentially sustainably renewable fuel for diesel engines; transesterification is the most used method to produce it and high quality vegetable oils are the most usual raw material. Non-edible vegetable oils such as castor oil can provide an alternative feedstock. In this work biodiesel was obtained by transesterification of castor oil with subcritical methanol; the reaction was carried out in an hermetic reactor at temperatures higher than methanol boiling point and with a small amount of potassium methoxide as catalyst. The effect of methanol:oil molar ratios were analyzed, observing that high proportion of alcohol is needed to reach high ester content, the best results were reached with 24:1 MeOH:oil molar ratio. Regarding catalyst concentration, 8.7 mM (0.12 wt%) were enough to achieve good results. A temperature of 150 ºC and 1 h of reaction, at 10 bar, were the mildest conditions to reach an ester content higher than 90 wt %. The highest ester content, 94.7 wt %, was achieved at 220 ºC, 36 bar and 4 h of reaction time. Hence good quality biodiesel from castor oil can be produced in subcritical methanol conditions, using a small amount of basic catalyst.
—Biodiesel, methanol, subcritical, transesterification.
N. Sanchez, J. M. Encinar, and G. Martínez are with the Department of Chemical Engineering and Physical Chemistry, University of Extremadura, Avda. Elvas s/n, 06006 Badajoz, Spain (e-mail: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org).
J. F. González is with the Department of Applied Physics, University of Extremadura, Avda. Elvas s/n, 06006 Badajoz, Spain (e-mail: email@example.com).
Cite:Nuria Sánchez, José M. Encinar, Gloria Martínez, and Juan F. González, "Biodiesel Production from Castor Oil under Subcritical Methanol Conditions," International Journal of Environmental Science and Development vol. 6, no. 1, pp. 61-66, 2015.