Efficient Synthesis of Biobased Glycerol Levulinate Ketal and Its Application for Rigid Polyurethane Foam Production

Glycerol levulinate ketal (GLK) is a novel biobased chemical compound with great potential for industrial applications, especially in the areas of green solvents and polymeric materials. For the first time, this study investigated the synthesis of GLK through acid-catalyzed ketalization at extremely low acid contents between two biobased platform chemicals, methyl levulinate (ML) and glycerol, and fully evaluated the effect of the molar ratio of ML to glycerol, reaction temperature, catalyst amount, vacuum degree, and reaction time on glycerol conversion and GLK yield. Under optimal conditions of a molar ratio of ML to glycerol of 4.4, a reaction temperature of 123 degrees C, a vacuum degree of 90 kPa, a catalyst amount of 0.27 mmol, and a reaction time of 30 min, a high GLK yield of up to 97.2% can be achieved. Further tranesterification between GLK and ethylene glycol allowed us to obtain a new biopolyol with a hydroxyl number of 536 mg of KOH/g, which demonstrated great potential for producing biobased rigid polyurethane (PU) foams; PU foams with 100% GLK-based polyol have a compressive strength of 197 kPa. Its thermal stability and compressive strength can be reinforced with the incorporation of diatomite. This study provided a promising way to synthesize GLK and its derived polyols for PU applications.