Synthesis, Characterization and Foamability Application of a Palm Kernel Oil–derived Surfactant for Enhanced Residual Oil Recovery

The investigation of renewable surfactants for foam-assisted enhanced oil recovery (EOR) provides a basis for evaluating palm kernel oil (PKO) as a chemical feedstock. This study synthesised a PKO-derived sulfonated methyl ester surfactant, characterised its functional groups and assessed its foam generation and persistence under selected experimental conditions. Palm kernel oil was converted to fatty acid methyl esters by base-catalysed transesterification with methanol, followed by sulfonation using chlorosulfonic acid and subsequent neutralisation. The product was examined by Fourier-transform infrared spectroscopy (FTIR). Foam performance was evaluated using a static graduated-column method at 25, 50 and 75 °C, with synthetic brines of varying concentration, SiO₂ and Al₂O₃ nanoparticles at nominal concentrations of 0.1 and 1.0 wt.%, and crude-oil ratios of 90:10 and 50:50. Initial foam height and subsequent height decay were used to assess foam generation and persistence. The FTIR spectrum displayed aliphatic C–H bands at 2922.23 and 2855.14 cm⁻¹, an ester carbonyl band at 1744.39 cm⁻¹ and sulfonate-associated bands at 1170.38 and 1110.75 cm⁻¹, consistent with the intended surfactant structure. Increasing brine concentration and temperature generally reduced foam generation and persistence. A greater crude-oil proportion was associated with additional foam destabilisation. Formulations containing nanoparticles retained measurable foam under several investigated conditions, with differences among nanoparticle types and concentrations. These findings support further investigation of PKO-derived surfactant formulations for foam-assisted EOR, while recognising that bulk-foam measurements do not demonstrate recovery of residual oil in porous media.