Synthesis of <i>Murraya koenigii</i> ‐Derived Heterogeneous Catalyst for Sustainable Biodiesel Production from <i>Cassia Fistula</i> Oil

ABSTRACT The present investigation aims to utilize Murraya koenigii extract for the synthesis of a CaO catalyst to produce biodiesel from crude oil obtained from Cassia fistula . Initially, the Murraya koenigii extract was prepared by boiling its ground leaves for 30 min. Then, a heterogeneous catalyst (CaO) was prepared by sol‐gel synthesis. The precursor obtained was annealed at 500°C, 700°C and 900°C. X‐ray diffraction (XRD) analysis of the synthesized material revealed that the CaO phase retained its structure at 700°C and 900°C. Similarly, Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of CaCO 3 at lower temperatures, while CaO was formed at higher temperatures. Gas Chromatography–Mass Spectrometry (GC‐MS) analysis of the Murraya koenigii extract confirmed the presence of dominant acidic compounds (1‐butanol and n ‐hexadecanoic acid), which act as acid catalysts during the formation of CaO. Biodiesel (75% yield) from Cassia fistula oil was synthesized by heating the crude oil and CaO with methanol at 60°C for 2 h under reflux conditions. FTIR analysis of the crude oil and synthesized biodiesel showed a characteristic peak for C═O stretching of the ester group (1746 cm −1 ) and the presence of an ester linkage, indicated by a peak at 1157 cm −1 . GC‐MS analysis of the crude oil confirmed the presence of key fatty acids such as oleic acid, palmitic acid and linoleic acid which were suitable for biodiesel production.