Advancing biodiesel production from Pyrus glabra seed oil: Kinetic study and RSM optimization via microwave-assisted transesterification with biocompatible hydroxyapatite catalyst

 In this study, a biocompatible hydroxyapatite (HAp) catalyst was synthesized using the chemical precipitation method to create biodiesel (FAME). The HAp was characterized for its structure (FT-IR and XRD), particle size, morphology (SEM and TEM), and surface area (BET). The obtained results indicated that HAp had a spherical shape ranging in size from 28.36 to 51.40 nm, a specific surface area of 21.90 m2/g, and a pore diameter of 15.36 nm. The aforementioned catalyst was employed in the transesterification of Pyrus glabra seed oil, with the assistance of microwaves, and the optimization of the biodiesel production process was achieved using RSM-CCD. The impact of the reaction parameters, including catalyst weight (0.5–1.5 wt%), temperature (60–80 °C), and time (10–30 min), was analyzed. The highest biodiesel yield of 89.21% was achieved in 30 min using a 0.5 wt% catalyst at 80 °C. Microwave-produced FAME was evaluated with FT-IR and GC-MS analysis. GC-MS results revealed 78.02% unsaturated and 13.16% saturated FAME content. The FTIR spectrum validated the presence of methyl and ester groups in the produced biodiesel. Both the FTIR and GC-MS results illustrated that the produced biodiesel had good quality. Transesterification of Pyrus glabra seed Oil followed first-order kinetics with an activation energy of 23.20 kJ/mol and an Arrhenius constant of 2.43 × 104 min−1. The catalyst remained active over six recycling cycles without notable decline. The optimal properties of Pyrus glabra biodiesel, meeting ASTM standards, highlight its potential as a catalyst for large-scale production, aligning with the Sustainable Development Goals (SDGs).