Sustainable biodiesel production from waste cooking oil using highly effective CaO/hectorite catalyst: Process optimization, kinetic and thermodynamic studies.

Biodiesel production through trans-esterification reaction requires design of efficient solid catalyst for sustainable use. This study reports a newly prepared CaO/hectorite catalyst for trans-esterification reaction of waste cooking oil (WCO). The catalyst material was prepared by wet impregnation method. Material characterization was done using various advanced instrumentation techniques such as FTIR, ¹H/¹³C NMR, XRD NMR, BET, TGA and FE-SEM. The result of FE-SEM characterization shows the surface heterogeneity in catalytic material. Further, an enhanced BET surface area (142.3 m² g⁻¹) of CaO/hectorite indicated suitability of material for catalytic applications. Kissinger-Akahira-Sonuse (KAS) computational model was used to evaluate thermodynamic parameters. Response surface methodology (RSM) – Box Behnken model/ANOVA was used to draw the 3D-surface plots and 2D-contour plots for estimation of maximum biodiesel yield. The catalytic trans-esterification shows high biodiesel production (95 %) in an optimized reaction condition (10.5:1 methanol:oil molar ratio, 3.5 % catalyst loading, 57.5 °C reaction temperature and 105 min). It was found that the biodiesel produced from WCO has fuel characteristics complied with that of B100. The catalyst could be reused up to seven consecutive cycles operation resulting biodiesel production (>80 % yield) thus indicating future commercial applications in a sustainable manner.