Sustainable synthesis of shea butter-derived bio-lubricants: A green alternative to mineral oils

Abstract

As environmental concerns over mineral oil-based lubricants rise, the search for sustainable alternatives intensifies. This study explores producing bio-lubricant from shea butter using double-transesterification with sodium hydroxide and tetraoxosulphate (IV) acid as catalysts. The process achieved a 57.89 % yield at a 4:1 molar ratio of shea methyl ester to trimethylolpropane, with 0.8 % w/w catalyst at 110°C for three hours. Fourier-transform infrared (FTIR) spectroscopy identified key functional groups in the crude oil: O-H (3340 cm⁻¹), C-H (2914–2980 cm⁻¹), CO (1740 cm⁻¹), and C-H terminal alkane bonds (1456 cm⁻¹). In the bio-lubricant, the spectrum showed C-O ester groups (1173–1253 cm⁻¹), CO carbonyl groups (1740 cm⁻¹), C-H stretching (2855–2923 cm⁻¹), and O-H polyol groups (3356 cm⁻¹). These findings demonstrate significant chemical and physicochemical modifications, underscoring the potential of shea butter-based bio-lubricant as a sustainable and green alternative to mineral oils.