A Green Process for Selective Hydrolysis of Cinnamaldehyde in Water to Natural Benzaldehyde by Using Ti and Zn Modified Hydrotalcites as Catalysts

Abstract

Hydrolysis of Cinnamaldehyde (CNM) is one of the important processes for the production of industrially essential natural benzaldehyde. Benzaldehyde is a vital precursor in the production of perfumes, cosmetics, food, beverages, and pharmaceutical intermediates. As homogeneous base catalysts are polluting and difficult to separate, heterogeneous catalysts should be used. Hydrolysis of cinnamaldehyde to benzaldehyde was studied over modified hydrotalcite (HT) base catalysts wherein HT was activated with either zinc or titanium, by combustion synthesis using glycine or glycerol as fuel. Both the catalyst composition and combustion fuel affect the activity of modified HT catalysts. SEM, EDXS, BET surface area and porosimetry were used to characterize all catalysts. Zinc modified hydrotalcite using glycine as fuel (Zn-HT-Glycine) was the most active, selective, and reusable catalyst under mild reaction conditions, and it was used to study the influence of different process parameters on the reaction rate, conversion and selectivity. Reaction mechanism and kinetics were established. The reaction follows pseudo-first-order kinetics. At 1:92 mole ratio of cinnamaldehyde to water and 0.005 g/cm3 catalyst loading, the reaction gives 75.8 % conversion of cinnamaldehyde and 100 % selectivity to benzaldehyde at 130oC in 4 h. The apparent activation energy was 19.15 kcal/mol. The overall process is green and the catalyst reusable.