Peels of banana, plantain and banana-plantain as heterogeneous catalysts in papaya seed oil methyl ester production

Purpose Heterogeneous catalysts derived from peels of banana, plantain and banana-plantain were utilized to catalyze the transesterification of papaya seed oil (PSO) in papaya seed oil methyl ester (PSOME) production. Design/methodology/approach Each of the fruit peels was subjected to a calcination temperature of 700°C:4 h to produce calcined banana peel ash (CBPA), calcined plantain peel ash (CPPA), in addition to calcined banana-plantain peel ash (CBPPA) while transforming potassium species in the peels into active K2O catalysts. The catalyst constituents were ascertained using scanning electron microscopy-energy dispersive X-ray, X-ray diffraction and Brunauer–Emmett–Teller analysis. Temperature, catalyst dosage, methanol/oil molar ratio and time effects on PSOME yield while utilizing the various bio-derived catalysts were investigated. Findings The CBPA, CPPA and CBPPA catalysts were found to have large surface areas and pore diameters of 870.8 m2/g: 2.123 nm, 547.372 m2/g: 2.133 nm and 697.422 m2/g: 2.131 nm, respectively. Each of the catalysts exhibited high catalytic ability in PSO methanolysis resulting in over 97% PSOME conversion at the optimal settings of 60°C, 2.5 wt. % catalyst dosage and 9:1 molar ratio at a reduced reaction time of 1 h and mixing rate of 600 rpm. The CBPA-catalyzed PSO transesterification depicted the highest catalytic capability with a fatty-acid-methyl-ester (FAME) yield of 100%. The catalysts' efficacy in the PSO transesterification is a function of the potassium content and the surface area. The PSOME physicochemical properties were within the specified biodiesel standard. Originality/value Thus a route for an ecologically and economically sustainable fuel could be established with bio-derived catalysts.