Ketonic decarboxylation and esterification of propionic acid over beta zeolites

The present work reports the nanocrystalline Beta zeolites synthesis from the high concentration hydrogels and their behavior in the propionic acid esterification with cyclohexanol and in the ketonic decarboxylation of propionic acid. The solids were characterized by X-ray diffraction, N₂-adsorption, transmission and scanning electron microscopy, diffuse reflectance infrared spectroscopy. Three types of acid sites has been evidenced in Beta zeolites: external silanol groups (Si–OH) (with weakly acidity), Si–OH–Al groups (with strong Brønsted acidity) and silanol nests associated with the defect sites (with Lewis acidity). In the propionic acid esterification with cyclohexanol, the highest cyclohexyl propionate yield was obtained over the sample with the highest specific surface area, the highest mesopore volume and the highest Brønsted acidity. In the propionic acid ketonic decarboxylation, the catalyst with the lowest ratio Brønsted acid sites/Lewis acid sites showed the highest activity and selectivity towards 3-pentanone compared to the other two which are more selective towards propanol.