A novel magnetic bifunctional hydrochar catalyst derived from palm leaf residue for biodiesel production: kinetic and thermodynamic studies

Abstract BACKGROUND Novel magnetic bifunctional hydrochar‐based catalysts were produced from activated hydrochar derived from palm leaf residue (PLRAH) via a wet impregnation technique and used to perform one‐step waste cooking oil (WCO) transesterification to produce biodiesel. The magnetic bifunctional hydrochar‐based catalysts were evaluated for their acid–base properties, crystallinity, functional groups, magnetism, textural properties, thermal stability, chemical composition, and morphology. RESULTS The PLRAH‐Fe 2 O 3 /K 2 O magnetic catalyst performed well in thermal testing, with a large specific surface area of 111.08 m 2 g −1 and its high basicity value of 7.34 mmol g −1 , as well as an acidity value of 12.67 mmol g −1 , significantly contributed to the WCO transesterification. An optimum biodiesel yield of 98.36% was obtained under the following conditions: catalyst loading of 3 wt%, a methanol‐to‐WCO molar ratio of 12:1, and a reaction temperature of 75 °C for a duration of 4 h and biodiesel yields maintained at >80% after five cycles. The produced biodiesel complied with the physicochemical properties stated in ASTM D6751. The kinetic study also revealed that WCO transesterification using the one‐step approach had a pseudo‐first order and activation energy () of 24.27 kJ mol −1 . Furthermore, the thermodynamic variables, including Gibbs free energy (∆ G o ), enthalpy (∆ H o ), and entropy (∆ S o ) of WCO transesterification, were found to be 7.60 kJ mol −1 , 24.27 kJ mol −1 , and −21.78 J mol −1 K, respectively. This suggests that WCO transesterification was an endothermic and non‐spontaneous process. CONCLUSION The synthesized magnetic bifunctional hydrochar‐based catalyst demonstrated outstanding performance for WCO transesterification, highlighting its potential for efficient biodiesel production. © 2024 Society of Chemical Industry (SCI).