In this study, we have synthesized a solid acid catalyst by areca nut husk using low temperature hydrothermal carbonization method. The fabricated catalyst has enhanced sulfonic actives sites (3.12%) and high acid density (1.88 mmol g−1) due to –SO3H, which are used significantly for effective biodiesel synthesis at low temperatures. The chemical composition and morphology of the catalyst is determined by various techniques, such as Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Scanning electron microscope (SEM), Energy disruptive spectroscopy (EDS), Mapping, Thermogravimetric analysis (TGA), CHNS analyzer, Transmission electron microscopy (TEM), particle size analyzer, and X-ray photoelectron spectroscopy (XPS). Acid–base back titration method was used to determine the acid density of the synthesized material. In the presence of the as-fabricated catalyst, the conversion of oleic acid (OA) to methyl oleate reached 96.4% in 60 min under optimized conditions (1:25 Oleic acid: methanol ratio, 80 °C, 60 min, 9 wt% catalyst dosage) and observed low activation energy of 45.377 kJ mol−1. The presence of the porous structure and sulfonic groups of the catalyst contributes to the high activity of the catalyst. The biodiesel synthesis was confirmed by gas-chromatography mass spectrometer (GC–MS) and Nuclear magnetic resonance (NMR). The reusability of the catalyst was examined up to four consecutive cycles, yielding a high 85% transformation of OA to methyl oleate on the fourth catalytic cycle.

Sulfonated polycyclic aromatic carbon (SPAC) catalysts have specific surface characteristics owing to the presence of two types of functional groups: SO3H (sulfonic) and oxygen‐containing functional groups (COOH and OH groups). Oxygen‐containing functional groups provide a synergistic effect to the sulfonic group, resulting in a high total acid density and enhanced catalytic activity of SPAC. Owing to the high acid density, SPAC catalysts are used for various applications such as organic transformations, electrocatalysis and water treatment. The natural abundance of raw materials, easy processing for catalyst fabrication, excellent catalytic performance and high thermal and chemical stability make SPAC cost‐effective and environmentally benign. Biomass‐derived heterogeneous catalysts possess unique surface characteristics, high reusability and low cost owing to their easy accessibility, along with various environmental benefits. This review demonstrates biodiesel production using oleic acid as a feedstock material catalyzed by biomass‐derived SPAC catalysts. Additionally, various parameters such as catalyst synthetic parameters, esterification reaction parameters, the esterification reaction mechanism and catalytic stability, which affect the catalytic performance and esterification efficacy, are discussed. Finally, the future scope for developing novel SPAC catalysts has been demonstrated for young researchers in this field.

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Biodiesel is a less hazardous, environmentally friendly biofuel. Waste biomass derived heterogeneous sulfonated catalysts were a significant focus of the most advanced biodiesel processing techniques for simple and low-cost manufacturing processes.