Kinetics of acetalization of perfumery aldehydes with alkanols over solid acid catalysts

Abstract

This paper highlights the importance of heterogeneous catalysis in the manufacture of fragrance and flavor chemicals, with theoretical and experimental analysis of acetalization reaction. The acetals of n-octanal with methanol and ethanol were prepared by using solid acids, such as Filtrol-24, Amberlyst-15, dodecatungstophosphoric acid (DTPA) supported on ZSM-5, as well as on K-10 clay. The efficacy of these catalysts per unit weight basis was in the following order: Filtrol-24> Amberlyst-15> 10% DTPA/K-10 > 10% DTPA/ZSM-5 A kinetic model has been developed to observe that Eley-Rideal type of mechanism prevails with chemisorption of the aldehyde on the active sites. The reaction is intrinscially kinetically controlled. The overall rate of reaction is controlled by the formation of the acetal from the hemi-acetal on the surface of the catalyst, which is formed in the first step from the aldehdye and alcohol.