Production of ethyl ester biodiesel from a tranesterification reaction of used vegetable oil and ethanol was carried out using a sodium methoxide catalyst. Response surface methodology (RSM) was applied to investigate the effect of experimental factors on the fatty acid ethyl ester (FAEE) conversion. The design of the experiment involved a 5-level-4-factor central composite design and 30 runs were used to achieve the optimum percentage FAEE conversion that was determined by 1H-NMR. The coefficient of determination (R2) for the regression equation was 86.49% and the probability value (p<0.05) demonstrated a very good fit for the regression model. The optimum conditions obtained from RSM were 4% v/v of catalyst, 35.61% v/v of ethanol-to-oil, at 43.70°C reaction temperature, and 75.45 min of reaction time. The produced ethyl ester biodiesel was further purified by wet washing compared with dry washing using ion exchange resin. The result showed that the purified biodiesel by wet washing met the EN standard but the dry washing out put did not but only for the acid value. The blending of 10% v/v of purified biodiesel obtained from dry washing with 90% v/v of petrodiesel could decrease the acid value to meet the EN standard.

Biodiesel is derived from triglycerides by transesterification with methanol or ethanol. In this study, used vegetable oil was transesterified with ethanol using sodium methoxide as catalyst. Parameter affecting the process transesterification were investigated follow this detail. The effects of catalyst to oil volume ratio (3-7:100 %v/v), ethanol to oil volume ratio (20-40:100 %v/v), reaction temperature (55-70 °C) and reaction time (15-90 min.) on the percentage conversion of fatty acid ethyl ester (FAEE) and fatty acid methyl ester (FAME). The FAEE and FAME conversion were detected by 1H-NMR. The result showed that the maximum percentages at 84 % of FAEE and 16 % of FAME were obtained. These conversions were obtained at the catalyst to oil volume ratio of 4:100 %v/v, ethanol to oil volume ratio of 35:100 %v/v, temperature of 65 °C and reaction time of 75 min. The properties of mixed FAEE and FAME biodiesel were within the limits of EN standard. The confirmation result by 1H-NMR and ATR-FTIR also indicated the conversion of used vegetable oil into biodiesel.