Three-Dimensionally ordered macro-mesoporous ZrTiO4 supported polyoxometalate-ionic liquid hybrid for efficient biodiesel production from low-quality oils

In this study, a heterogeneous polyoxometalate-ionic liquid hybrid catalyst was successfully constructed on a hierarchical porous ZrTiO 4 support for one-pot biodiesel production from acidic oils. The three-dimensional ordered macro-mesoporous structure of the catalyst significantly facilitated reactant diffusion and increased the accessibility of active sites, leading to superior catalytic activity compared to non-hierarchical analogues. The immobilized polyoxometalate-ionic liquid composite functioned as integrated Brønsted-Lewis acid sites, substantially boosting the overall acidity. This catalyst demonstrated high efficiency in simultaneously converting triglycerides and free fatty acids into biodiesel. Under optimized reaction conditions, including a methanol-to-oil molar ratio of 35:1, a temperature of 130 °C, a catalyst loading of 8 wt%, and a reaction time of 6 h, it achieved 92.7% oil conversion alongside complete conversion of free fatty acids. Kinetic analysis revealed an ultralow activation energy of 35.2 kJ·mol −1 , which is significantly lower than values reported in the literature. In addition, the catalyst demonstrated robust tolerance to both water and free fatty acids in the feedstocks and retained significant activity after five reuses, showing great potential for sustainable biodiesel production from low-cost feedstocks.