A Sustainable Preparation of Glycerol Carbonate from Glycerol and Urea Catalyzed by Hydrotalcite-Like Solid Catalysts

The selective synthesis of glycerol carbonate from glycerol and urea catalyzed by hydrotalcite-like compounds has been performed under solvent-free conditions. Different hydrotalcite-like compounds have been prepared and characterized by X-ray diffraction (XRD) and infrared spectroscopic techniques (FTIR), which confirm the well-defined structure of these materials. The investigations of the reaction of glycerol and urea showed that hydrotalcite-like compounds including Mg, Zn, and Al elements have very high catalytic activity. As a result, 89.8% conversion and 93.2% selectivity for glycerol carbonate were obtained under suitable conditions. Comp ared to the addition of Zn, the addition of Ga and Ni is disadvantageous to the catalytic activity of Mg-Al hydrotalcite. These phenomena are consistent with the activity of the halides of these metals. The difference between the XRD and FTIR results of fresh and used catalysts showed the existence of dissolved metal, which was related to the catalytic activity in the reaction. The kinetic study with hydrotalcite catalysts was also performed. The relationship between the amounts of active species in liquid phase and the yield of product and recycling tests indicated that homogeneous catalysis was dominant during the entire reaction.