Synthesis of glycerol carbonate from urea and glycerol using polymer-supported metal containing ionic liquid catalysts

• The polystyrene-supported metal containing ionic liquid catalysts was successfully synthesized.
• PS-(Im)2ZnI2 with well-balanced acid–base properties exhibited high catalytic activity.
• The reaction pathway was studied via FT-IR and 13C NMR.
• PS-(Im)2ZnI2 was easily recovered and reused.

Polystyrene-supported, metal containing imidazolium salt [PS-(Im)2MX2] catalysts were prepared and characterized by various analytical methods, and their role in the synthesis of glycerol carbonate from glycerol and urea was investigated under mild conditions. Among different metal containing PS-(Im)2MBr2 catalysts, the yield of GC increased Cu < Mg < Zn, which is the order of acid–base balance of the catalysts. PS-(Im)2ZnI2 catalyst, which showed a good balance of the acid–base properties, was the most active and selective catalyst; it was readily recoverable and reusable in the subsequent reaction cycles. Furthermore, the reaction pathway for the glycerolysis of urea was studied with the time-on-line analysis of the products via a combination of FT-IR spectroscopy and 13C NMR analysis. The effects of reaction parameters such as temperature, degree of vacuum, catalyst loading, and the ratio of reactants on the reactivity were also investigated to elucidate the reaction mechanism.

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