Comparative catalytic activity of supported ZnBr2-containing ionic liquid catalysts for preparation of glycerol carbonate by glycerolysis of urea

Abstract

The synthesis of glycerol carbonate by glycerolysis of urea was investigated under mild conditions, using immobilized metal-containing ionic liquid catalysts. Three different catalysts were prepared, with the following supports: (1) polystyrene (PS), (2) commercial silica (CS), and (3) chitosan (CH). The glycerolysis of urea was considered to include two main reactions: carbamoylation of glycerol and carbonylation of glycerol carbamate. The approximate rate constant for PS-(Im)2ZnBr2 was higher than those of CH-(Im)2ZnBr2 and CS-(Im)2ZnBr2 probably due to its wellbalanced acid-base properties. The activation energies for PS-, CH-, and CS-(Im)2ZnBr2 were 142.9, 163.0, and 166.7 kJ mol−1, respectively. PS-(Im)2ZnBr2 exhibited better reuse properties than CH-(Im)2ZnBr2 and CS-(Im)2ZnBr2 catalysts.