Acetalization of glycerol and benzaldehyde to synthesize biofuel additives using SO42-/CeO2–ZrO2 catalyst

Abstract

Synthesis of 1,3- dioxane and 1,3-dioxolane, using sulfated CeO2–ZrO2 catalyst for acetalization of glycerol with benzaldehyde, is the focus of present work. SO42-/CeO2–ZrO2 catalyst was synthesized using combustion method. Experiments were carried out to analyze the effect of various solvents (n-hexane, toluene, tert-butyl alcohol, pentanol), molar ratios (1:3, 1:5, 1:7), catalyst loadings (3 wt%, 5 wt%, 9 wt %) and temperatures (80 °C, 90 °C, 100 °C) on glycerol conversion and selectivity of the products. Selectivity of 87.20% dioxolane and 12.80% dioxane was obtained at molar ratio of 1:3, 9 wt% catalyst loading and temperature of 100 °C.Strong NH3 desorption peak from NH3-TPD study indicated the high acidic strength of sulphated catalyst. Strong surface acidity and surface porosity (observed from TEM and SEM analysis) contributed to an enhanced activity of the catalyst for glycerol acetalization reaction. The kinetics of the reaction was studied using an elementary kinetic law. A correlation coefficient of 0.98 from the selected kinetic model proved that the rate of acetalization reaction was dependent on glycerol concentration and acetal formation was instantaneous. The study demonstrated the application of an environmentally benign, inexpensive, thermally stable, active SO42-/CeO2–ZrO2 catalyst for glycerol acetalization reaction to synthesize 1,3-dioxolane as the desired product.