Bio-Based Copper Oxide Nanocatalyst for Sustainable High-Quality Biofuel Production: RSM-Facilitated Optimization and...

The Michelia champaca plant's leaves and seeds are used in this study as environmentally acceptable resources to produce copper oxide nanoparticles (CuO NPs) and biodiesel, respectively. M. champaca leaf extract is used as a reducing and fuel agent in the solution combustion process to synthesize the CuO NPs. Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Brunauer-Emmett-Teller (BET) methods were used to characterize the CuO NPs and used as an effective catalyst in the manufacture of biodiesel utilizing M. champaca oil (MCO) as the feedstock under various reaction conditions. The results exhibited a monoclinic crystal structure with a spherical shape. The surface area of CuO NPs was found to be 13.27 m²/g, the pore diameter was 23.4 nm and the pore volume was 0.04725 cm³/g. Two-step transesterification, that is, esterification followed by transesterification, is conducted for MCO. To optimize the biodiesel production parameters, response surface methodology (RSM) with the central composite design algorithm is used. The maximum yield of M. champaca methyl ester (MCME), 97.35%, was obtained at 60°C, stirring at 650 rpm, with a reaction period of 64 min, a CuO concentration of 3 wt.% and a methanol-to-oil (M/O) molar ratio of 8.94:1 predicted through RSM. For up to four cycles, the CuO NPs exhibited excellent catalytic stability, with only a little reduction in biodiesel output (86.3%). An activation energy (Ea) of 41.69 kJ/mol and a frequency factor (A) of 1.5 × 10⁵ min^-1 obtained through pseudo-first-order reaction, which is the result of kinetic analysis of MCME synthesis. ¹H NMR and FTIR were used to further evaluate the MCME. It was discovered that MCME's fuel qualities met ASTM requirements. Metrics related to green chemistry are also included. Green chemistry measures, such as environmental factor (E-factor), atom efficiency, atom economy and solvent and catalyst environmental effect parameter, have been investigated.