Synthesis of Waste Cooking Oil Epoxide as a Bio-Lubricant Base Stock: Characterization and Optimization Study

In the present communication waste cooking oil (WCO) epoxide was synthesized by in-situ epoxidation technique using hydrogen peroxide (H₂O₂) as oxygen donor in presence of acidic ion exchange resin (IER) as catalyst. The main objective of this study was to establish an optimum reaction condition for maximum oxirane oxygen content (i.e., OOC) and to study the effects of process variables and their interaction to maximise OOC (response). Response surface methodology (RSM) was employed for statistical analysis and to optimize the reaction variables in the epoxidation of WCO. Central composite rotatable design (CCRD) was adopted to study the effect of time (h), H₂O₂ molar ratio (mol), catalyst loading (wt%) and temperature (°C) on response. The outcomes of RSM analysis indicate that most of the linear, quadratic and cross variables were showing highly significant (P < 0.0001) effect on response. A second-order model satisfactorily fitted the data (R ² = 0.9935). Based on the quadratic analysis optimum condition for this reaction was found to be H₂O₂ 1.68 mol (H₂O₂) to ethylenic unsaturation molar ratio), catalyst loading 16.75 wt%, temperature 54 °C and reaction time 11.45 h, at this condition % OOC was found to be 6.2%. The product was confirmed by ¹H NMR and FTIR spectral analysis. After structural modification physico-chemical properties of epoxidised WCO were found to be improved compared to WCO. This indicates that WCO epoxide could act as a potential alternative for the conventional lubricant base-stock.