Synthesis of glycerol carbonate from 3-chloro-1,2-propanediol and carbon dioxide using triethylamine as both solvent and CO2 fixation–activation agent

The synthesis of glycerol carbonate from 3-chloro-1,2-propanediol, a glycerol derivative easily obtained by reacting glycerol with HCl, and carbon dioxide using triethylamine as both solvent and CO2 fixation and activation agent is reported. The influence on conversions and yields of triethylamine/3-chloro-1,2-propanediol molar ratio, temperature, CO2 pressure and reaction time has been studied. A 3-chloro-1,2-propanediol conversion of 100% and a glycerol carbonate yield of 90% are obtained at 100 °C, using a triethylamine/3-chloro-1,2-propanediol molar ratio of 1.5, a carbon dioxide pressure of 25 bar and 60 min. Glycerol was the only byproduct detected in 4–6% yields independently of experimental conditions. Above 100 °C, glycerol carbonate yield decreases dramatically due to glycerol carbonate polymerization resulting in a polyglycerol mixture. The yield of glycerol carbonate is strongly and negatively influenced by the presence of water. A reaction mechanism is proposed in which the first step is the formation of a zwitterionic adduct between triethylamine and CO2 which reacts with 3-chloro-1,2-propanediol leading to an intermediate which evolves towards glycerol carbonate either directly or through the glycidol intermediate.

Figure optionsDownload as PowerPoint slideHighlights
► Glycerol carbonate is obtained from 3-chloro-1,2-propanediol and CO2 in 90% yield.
► Reaction is carried out in subcritical conditions.
► CO2 fixation–activation is simultaneously achieved with triethylamine as solvent.
► A zwitterionic adduct between CO2 and triethylamine leads to CO2 activation.