A selective synthesis of glycerol carbonate from glycerol and urea over Sn(OH)2: a solid and recyclable in situ generated catalyst

Abstract

In this work, we report a selective and straightforward process to synthesize glycerol carbonate from urea and glycerol using a simple but commercially unavailable catalyst (Sn(OH)₂). This catalyst was generated in situ from the reaction of Sn(II) halides and urea during the glycerol carbonatation process. Effects of main reaction parameters (i.e., temperature, molar ratio of urea to glycerol, catalyst concentration) were investigated. Different tin halides were assessed as catalytic precursors, with SnCl₂ being the most efficient. We found that Sn(OH)₂-catalyzed glycerol carbonation reactions with urea achieved high conversion and selectivity (ca. 87 and 85%, respectively). The samples of Sn(OH)₂ generated in situ or previously synthesized were equally active and selective catalysts toward glycerol carbonate were successfully reutilized without loss activity. This is a very attractive route based on two inexpensive and readily available feedstocks in a chemical cycle that, overall, results in the chemical fixation of carbon dioxide and, concomitantly, adds value to glycerol, a biodiesel byproduct.