Esterification of propanoic acid with 1,2-propanediol: catalysis by cesium exchanged heteropoly acid on K-10 clay and kinetic modelling

Abstract

Aromatic as well as aliphatic esters are important classes of chemicals having a variety of applications. Valuable chemicals can be produced from 1,2-propanediol (1,2-PDO) by etherification, esterification and cyclization through acetalization. In the current study, esterification of propanoic acid was carried out with 1,2-propanediol using a clay supported heteropolyacid Cs_2.5H_0.5PW₁₂O₄₀/K-10 as solid acid catalyst in a batch reactor. The diester of 1,2-PDO was found to be formed at 180 °C. The product of this reaction, the diester of propanoic acid with propylene glycol, is approved as a safe chemical and also as a food flavoring agent in non-alcoholic beverages, chewing gums and frozen dairy products. The Cs_2.5H_0.5PW₁₂O₄₀/K-10 catalyst was prepared by the incipient wetness method, and characterization techniques such as X-ray diffraction, surface area measurement by N₂ adsorption–desorption, FTIR, and SEM were employed to study its physicochemical properties. The product was confirmed and characterised by a mass spectroscopic method. The effect of various reaction parameters such as speed of agitation, catalyst loading, mole ratio, and temperature was studied. Parameter optimization was carried out and a kinetic model developed. The apparent activation energy was found to be 13.8 kcal mol⁻¹. FT-IR and surface area analysis established that the catalyst was stable and reusable.