Biodiesel production catalyzed by NaOH/Magnetized ZIF-8: Yield improvement using methanolysis and catalyst reusability enhancement

The current study investigates the methanolysis reaction to increase biodiesel yield using the recently developed NaOH/magnetized ZIF-8 catalyst. The effects of methanol to oil ratio and catalyst dose on oil conversion with their interaction were studied by employing full factorial design and response surface methodology. Two-factor interaction model was selected as the best model to fit the experimental data with a determination coefficient (R²) of 0.97 where all the model's parameters were significant. The two factors were found positively influencing the reaction conversion. The maximum observed conversion reached almost 100% at 21:1 M methanol to oil ratio and 3 wt% catalyst/oil ratio. Additionally, the kinetic study revealed that pseudo-second order kinetic model fits the experimental data well. In addition, the Arrhenius equation analysis showed lower activation energy and higher pre-exponential factor for methanolysis in comparison with ethanolysis indicating the faster kinetics. Besides, ASTM standard testing techniques confirmed that the produced esters at optimum conditions can be used as biodiesel sustainable fuel. Finally, several modifications in the catalyst preparation conditions or procedure showed their ability to increase catalyst stability and reusability characteristics.