Atmospheric Pressure Continuous Production of Solketal from the Acid-Catalyzed Reaction of Glycerol with Acetone

A continuous-flow process at atmospheric pressure was designed for the conversion of glycerol to solketal, an oxygenated fuel additive, through the acid-catalyzed reaction of glycerol with acetone. Process optimization was performed by checking the influence of different variables on the conversion and selectivity. The variables examined were: residence time (12, 24, 60 and 120 min), catalyst type (Amberlyst-15 and K-10 Montmorillonite), catalyst loading (7, 3, and 1 g), reaction temperature (50, 40 and 30 degrees C), molar ratio of the reactants (1:2, 1:5, 1:10, 1:15 and 1:20) and solvent used to homogenize the system (dimethylsulfoxide or dimethylformamide). The highest conversion (92%) was observed with 7.0 g of Amberlyst-15, reaction temperature of 50 degrees C, molar ratio of glycerol to acetone of 1:20 and dimethylformamide as solvent. In all cases, solketal isomers (five and six-membered ring ketals) were the only product observed. The results of solketal formation of this study, carried out at atmospheric pressure, were similar to other studies with pressures of up to 120 bar. The utilization of higher catalyst loading and molar ratio of reactants compensate the use of atmospheric pressure to achieve high conversion levels and selectivity to the desired product.