Kinetics of Glycerol Dehydration with WO3/TiO2 in Supercritical Water

Dehydration of glycerol on TiO2 and WO3/TiO2 in supercritical water at 400 degrees C and 33 MPa was examined using a fixed bed flow reactor. The structure of TiO2 was changed from anatase type to rutile type in supercritical water, and addition of WO3 to TiO2 suppressed the change of structure. Main products were acrolein and acetaldehyde. In the reaction on TiO2, a large amount of propionic acid was also produced. The reaction route was proposed on the basis of the products distribution from glycerol and intermediate products. From kinetic analysis, the reaction route could explain the experimental data well. Because of high water density, degradation of acrolein to acetaldehyde is favorable in supercritical water. Reaction rate for dehydration of glycerol to acrolein considerably increased with an increase in WO3 content of the catalyst, and this dependence is attributed to higher surface area and stronger acidity of WO3/TiO2 catalysts.