Positive Effect of Antagonistic Additives on the Homogeneous Catalytic Etherification Reaction of Glycerol

Abstract

Various compounds prepared using glycerol, diglycerol (DG), and triglycerol (TG) have been gaining increasing attention due to their wide range of applications. To increase the yield and selectivity of DG and TG syntheses, previous studies investigated a variety of catalysts with different basicity and variable reaction temperatures. In this study, we introduced additives that act as inhibitors to increase the selectivity of the etherification reaction for DG and TG production and depress the formation of higher oligomers by moderating the activity of the catalyst. By adding weakly acidic alkali metal-based inorganic salts (NaHSO4 and KHSO4), the selectivity of DG and TG formation could be enhanced, although the conversion of glycerol decreased due to the reduced activity of catalyst. We found that the decrease in the activity of the catalyst caused by the additives could be recovered and that side reactions were reduced if the reaction was carried out at an increased temperature of 280 °C and if the reaction time was shortened to 2 h to suppress the formation of oligomers. The dependence of the reaction on the amount of the additive, the reaction time, and the reaction temperature was investigated to elucidate the role of the additive.

Keywords

• glycerol
• diglycerol
• triglycerol
• proton donor
• additive
• homogeneous catalysis