Biopolyol synthesis via ring-opening of epoxidized soybean oil with glycerol utilizing a novel sulfonic-functionalized ionic liquid as the catalyst at low temperature

Herein, a novel synthetic strategy for the preparation of soybean oil-based biopolyol has been established using ionic liquids (ILs) as the green and efficient catalysts via the ring-opening reaction of epoxidized soybean oil (ESO) with glycerol as the nucleophile. Among them, the sulfonic-functionalized IL 1-butylsulfonic-3-methylimidazolium trifluoromethanesulfonate ([BSO 3 HMIM]OTF) exhibited superior catalytic performance in the ring-opening reaction under mild reaction conditions, demonstrating excellent catalytic efficiency and a high hydroxyl number of the synthesized biopolyol products. The impacts of various reaction variables on the ring-opening reaction were systematically investigated employing one variable at a time (OVAT) and response surface methodology (RSM). Under the optimized reaction parameters, including a catalyst loading of 1.2 wt%, a reaction duration of 4 h, a molar ratio of glycerol to epoxy groups of 3:1, and a tert -butanol to substrate of 1:1 (w/w) at 45 °C, the highest epoxy group conversion rate and the hydroxyl number were found to be 98.0 ± 0.6 % and 285.0 ± 1.4 mg KOH/g, respectively. Characterization by NMR and FT-IR confirmed the successful synthesis of biopolyols, while thermal stability and rheological studies further highlighted their suitability for diverse industrial applications as valuable chemical intermediates. These findings underscore the potential of sulfonic-functionalized [BSO 3 HMIM]OTF IL as efficient and eco-friendly catalyst in sustainable biopolyol production.