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

摘要

BACKGROUND: An indirect solvent-free synthetic approach for obtaining glycerol carbonate and glycidol from glycerol and CO_2 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 K_2CO_3 as the carbonation source at 80 °C, a reaction time of 30 min and a 3:1 HAL/K_2CO_3 molar ratio. A lower yield of glycerol carbonate (60%) is obtained from KHCO_3 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 KHCO_3 (~0.59 mol mol~(-1) glycerol carbonate independent of operating conditions) than from K_2CO_3 (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 CO_2, 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.