Valorization of bio-glycerol: New catalytic materials for the synthesis of glycerol carbonate via glycerolysis of urea

The glycerolysis of urea plays an important role in the conversion of glycerol into glycerol carbonate because it is a phosgene-free process that uses easily available and low-cost raw materials that have a low toxicity. γ-Zirconium phosphate shows a good activity as catalyst as it affords 80% of conversion of glycerol under mild reaction conditions. The catalyst is easily recoverable and reusable in subsequent cycles of reaction. The kinetics of the reaction has been studied considering the full parameter space. The best temperature is 418 K, with 3 h of reaction using an equimolar amount of the two reagents (glycerol and urea) with a catalyst load of 0.6–1.5% w/w with respect to glycerol. The behaviour of the catalyst has been investigated by using the TPD technique. Multinuclear 1H and 13C NMR and FTIR have been used for the characterization of intermediates and by-product. The reaction mechanism is fully elucidated.