Optimum Biodiesel Production from Shea Nut Oil by Heterogeneous Catalyst Transesterification

Abstract

A renewable alternative to petroleum fuels is essential due to declining oil supplies. Bio-based diesel production from fruit peels and vegetable oil waste may reduce reliance on petroleum. Various materials, including oyster shells, rocky clay, and plantain peels, were identified as potential resources, used for developed bifunctional catalysts, utilized in heterogeneous catalyst transesterification. The catalyst's stability and characteristics were evaluated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). High surface area analysis through Brunauer-Emmett-Teller (BET) and various adsorption isotherms indicated its effectiveness. The catalyst primarily consisted of calcite, along with minerals like muscovite, orthoclase, and quartz, as confirmed by X-ray diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) revealed metal-oxide bonding, C=C stretching, and hydroxyl groups. Energy dispersive X-ray spectroscopy demonstrated that CaO constituted 66.194%, with K₂O and Al₂O₃ also present. Scanning electron microscopy (SEM) highlighted the catalyst's shape and porosity, confirming its potential for serial reuse. The optimized heterogeneous catalyst transesterification of shea nut oil resulted in ideal conditions: 5 wt% catalyst loading, 65°C reaction temperature, 8:1 methanol-to-oil molar ratio, 70-minute reaction time, and a biodiesel yield of 92.68%. Characterization showed that the produced biodiesel met key diesel fuel properties and conformed to ASTM D-675 standards. Gas chromatography/mass spectroscopy (GC/MS) analysis indicated that the biodiesel contained predominantly methyl esters, achieving 99.57% with minimal impurities, making heterogeneous catalyst transesterification a cost-effective and scalable method for biodiesel production.