Natural Oil Polyol from High-Oleic Palm Oil─Reaction Kinetics and Monitoring Using Near-Infrared Spectroscopy

Natural oil polyols are widely used biobased monomers for the manufacture of polymers and resins. They are mainly produced via hydroxylation of epoxidized vegetable oils. This work studied the kinetics of hydroxylation of epoxidized high-oleic palm oil via oxirane ring cleavage with ethylene glycol (EG). Experiments were performed at different temperatures (65–95 °C), hydroxyl-to-oxirane mol ratios (1.75–14), and catalyst loadings (H2SO4, 0.5–4% wt). The reaction was monitored by measuring the hydroxyl value and oxirane oxygen content in samples using near-infrared absorbance. Different power-law kinetic expressions were evaluated, and the lower average error (3.25%) resulted in first order with respect to epoxide, second order with respect to EG, and considering oligomers formation. The corresponding frequency factor and energy of activation for hydroxylation were 3.58 × 104 and 51.9 kJ/mol, and those for oligomerization were 3.32 × 105 and 67.2 kJ/mol, respectively. The obtained model is suitable for further process design and scale up.