Biodiesel production from waste frying oils: Optimization of reaction parameters and determination of fuel properties

Alkali-catalyzed transesterification of waste frying oils (WFO) was carried out in various conditions to investigate the effects of catalyst concentration, reaction time, methanol/oil molar ratio, reaction temperature, catalyst type (hydroxides, methoxides and ethoxides), and purification type (such as washing with hot water, purification with silica gel and dowex) on the biodiesel yields. The optimum conditions were 0.5% wt. of NaOH, 30 min reaction time, 50 degrees C reaction temperature, 7.5 methanol to oil ratio and purification with hot distilled water. 96% biodiesel yield with similar to 97% ester content was obtained within in these conditions, and the activation energy was found to be as 11741 J mol(-1). The determined specifications of obtained biodiesel according to ASTM D 6751 and EN 14214 standards were in accordance with the required limits. As a conclusion, the present study indicates that WFO derived fuel promises being an alternative for petrodiesel, and could be used in engines without a major modification due to its qualifications. (C) 2012 Elsevier Ltd. All rights reserved.