To produce biodiesel from oleic acid (OA), the effectiveness
of
sweet lemon (
Citrus limetta
) waste
peels as an acidic catalyst in an esterification process is examined
in the current work. A biowaste-derived sulfonated carbon-based catalyst
is fabricated without high temperatures via a simple one-pot process.
Several techniques are used to investigate the chemical components
and morphology of the catalyst, including Fourier transform infrared
spectroscopy (FTIR), powder X-ray diffraction (XRD), scanning electron
microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission
electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS),
thermogravimetric analysis (TGA), Brunauer–Emmett–Teller
(BET), and N
2
adsorption–desorption. The biodiesel
conversion is observed by gas chromatography–mass spectrometry
(GC–MS), proton nuclear magnetic resonance
1
H NMR,
and carbon nuclear magnetic resonance
13
C NMR. The excellent
biodiesel conversion of 96% was obtained using optimized conditions,
i.e., 1:20 of OA/MeOH, 5 wt % catalyst loading, 70 °C temperature,
and 3 h. The catalyst shows 87% conversion in just 1 h, and the maximum
conversion was found to be ≈96%. This high activity of the
catalyst can be attributed to the presence of sulfonic groups and
its porous nature. The formed catalyst shows excellent catalytic activity
up to three cycles.