An environmentally friendly biodiesel Production: Computational and experimental investigations of ZnO-based catalysts for enhanced olive oil conversion

The main aim of the present study was to develop recoverable and reusable monometallic ZnO/rGO and bimetallic Cu-ZnO/rGO compounds as acidic catalysts via an efficient synthesis method to optimize the conversion of olive oil into biodiesel. The chemical and structural properties of the catalysts were assessed utilizing XRD, TPD, BET-BJH, XPS, EDS, Raman, and TEM analyses. The final product of transesterification process was also evaluated by ¹H NMR and FTIR analyses. The objective is to attain high conversion rates while maintaining catalyst stability and reusability over multiple cycles. RSM and its BBD subset were used to estimate optimal conditions and simultaneously evaluate influential parameters. Under optimum conditions (i.e.; methanol/oil molar ratio of 15.5, a reactor catalyst loading of 10 wt %, and a specific temperature of 70 °C), a conversion rate of 94 % was achieved with the Cu-ZnO (13)/rGO catalyst. This level remained relatively constant over eight catalytic cycles, illustrating the robustness of the prepared catalyst. These experimental findings aligned closely with the DFT (density functional theory) calculations. They displayed that, the Cu-ZnO catalyst, with a Cu/Zn ratio of 0.3 exhibited the Maximum triglyceride adsorption energy of −4.97 eV, resulting in a high conversion also revealed experimentally.