Solvent-free synthesis of glycerol carbonate and glycidol from 3-chloro-1,2-propanediol and potassium (hydrogen) carbonate

BACKGROUND: An indirect solvent-free synthetic approach for obtaining glycerol carbonate and glycidol from glycerol and CO₂ through their more reactive and easily synthesizable derivatives 3-chloro-1,2-propanediol (HAL) and potassium (hydrogen) carbonate has been studied. RESULTS: The reaction is fast with source of carbonation and temperature having a strong influence on the results. A yield of 80% glycerol carbonate together with a simultaneous substantial production of glycidol (0.56 mol mol^-1 glycerol carbonate) are obtained using K₂CO₃ as the carbonation source at 80 °C, a reaction time of 30 min and a 3:1 HAL/K₂CO₃ molar ratio. A lower yield of glycerol carbonate (60%) is obtained from KHCO₃ after 50 min with the other experimental conditions remaining unchanged. In this case, glycidol formation is zero or insignificant. Glycerol is also obtained in high yields, although in much lower amounts from KHCO₃ (~0.59 mol mol^-1 glycerol carbonate independent of operating conditions) than from K₂CO₃ (0.84-1.1 mol mol^-1 glycerol carbonate, depending on experimental conditions). CONCLUSIONS: The proposed synthetic strategy overcomes the currently difficult direct reaction between glycerol and CO₂, leading to the simultaneous synthesis of two valuable chemicals: glycerol carbonate and glycidol. However, glycerol is also obtained in substantial amounts thus decreasing the overall yield of the process. Thus, methods for preventing its formation must be developed for industrial feasibility.