Bifunctional acid-activated montmorillonite catalyzed biodiesel production from non-food oil: Characterization, optimization, kinetic and thermodynamic studies

Utilizing robust heterogeneous catalysts to efficiently produce biodiesel from low-cost non-food oil is very important for replacing fossil energy to meet globally increasing energy demands and accelerate realization of carbon neutrality. In this study, a novel Lewis (L)-Brønsted (B) bifunctional catalytic material 30%Sn-MMT-SO3H was conveniently fabricated by ion-exchange and sulfonation using widely-sourced and biocompatible montmorillonite (MMT) as a matrix, which was successfully applied in direct conversion of Jatropha curcas oil (JCO) into biodiesel. Systematical characterization techniques showed that 30%Sn-MMT-SO3H presented a layered nanostructure along with a high specific surface area (145.32 m2/g), rich mesopores (5.8 nm), strong acidic intensity (1.801 mmol g−1), abundant accessible active sites, and outstanding chemical and thermal stability. Additionally, the single-factor method and response surface methodology (RSM) were employed to investigate optimal reaction conditions. Accordingly, the maximum biodiesel yield (93.1%) was achieved under conditions of 7 wt% catalyst dosage, 20.2 methanol/oil molar ratio at 150 °C for 7.5 h, and no significant decrease was observed after five cycles. Importantly, kinetic and thermodynamic behaviors together with possible reaction mechanisms were also determined. Compared with other reported catalysts, 30%Sn-MMT-SO3H exhibited satisfactory activity and reusability, showing promising prospects in industrialization of biodiesel mediated by heterogeneous acid catalysts.