Effects of Ethanol Purity and Ethanol-to-Oleic Acid Ratio on the Esterification of Oleic Acid Using 13X Zeolite Heterogeneous Catalyst

The effects of ethanol-to-oleic acid molar ratio and ethanol purity on the yield of biodiesel production were investigated for the esterification of oleic acid. The esterification reaction was conducted in a batch system utilizing 13X zeolite as a catalyst. The molar ratio of ethanol to oleic was studied in a range of 1:1 to 12:1, and the ethanol purity ranged from 80 to 100%. The reaction was conducted at 70 ºC up to 120 min with catalyst loads of 5 wt.%. The yield of ethyl oleate increased from 9.56 % at the 1:1 ethanol-to-oleic molar ratio to 11.13% at the 3:1, then decreased as the ethanol-to-oleic molar ratios increased. The reported water yield was 20.56% at 1:1 and higher values of water yield (roughly, 26 to 27 %) were recorded when higher molar ratios of ethanol-to-oleic molar ratios were used. The results showed that the best ethyl oleate yield was 13.90% achieved at a 3:1 ethanol to oleic acid molar ratio and 100% ethanol purity, and the use of excess ethanol encourages a forward reaction. The conversion of oleic acid was enhanced by increasing the ethanol purity and optimizing the molar ratio of ethanol to oleic acid. The maximum oleic acid conversion was 55.60%, attained at 100% ethanol purity and a 3:1 molar ratio of ethanol to oleic acid. In addition, the kinetic model revealed that the values of the reaction rate constant were 0.00270 and 0.00108 L/mol. min at 70 ºC for the forward and backward reactions, respectively. Moreover, the obtained results of the kinetic model were consistent with the experimental results.