Optimization of the production parameters of octyl ester biolubricant using Taguchi's design method and physico-chemical characterization of the product

• Synthesis of octyl ester via enzymatic esterification of free fatty acids (FFA) and octanol.
• Optimization of process parameters (temperature, enzyme amount, molar ratio of substrates, reaction time) by Taguchi (L9orthogonal array) robust design matrix.
• Characterization of developed octyl ester via Fourier transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (1H-NMR and 13C-NMR).
• Physico-chemical characterization of the produced octyl ester (following standard methods) revealed its potentiality to be used as biolubricant baseoil.

The enzymatic esterification of free fatty acids (FFA) from waste cooking oil (WCO) and octanol in a solvent free medium has been investigated. A statistical experimental design method (Taguchi L9 orthogonal array) was implemented to optimize the experimental conditions to maximize conversion of FFA to the corresponding octyl esters. The optimum conditions inferred from the Taguchi analyses were: temperature = 60 °C, Novozyme 435 = 5 wt% of FFA, molar ratio of octanol:FFA = 2.5:1 and reaction time = 3 h. The product octyl ester was characterized by Fourier transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (1H-NMR and 13C-NMR). The physico-chemical properties of the waste cooking oil and the product ester (developed from WCO) were determined following standard methods. The results revealed that the developed octyl esters have improved viscosity index, pour point, flash point and oxidation stability when compared to that of the raw material (WCO). Moreover the product is biodegradable (>90% biodegradability). Thus the synthesized octyl esters have shown potential to be used as an environment-friendly biolubricant base-oil.