Esterification of n-butanol with acetic acid in the presence of heteropoly acids with different structures and compositions

Abstract

The esterification reaction of n-butanol with acetic acid ([BuOH] : [HOAc] = 1 : 15 mol/mol; 55°C, 5% H2O) was studied in the presence of tungsten heteropoly acids of the Keggin (H3PW12O40, H4SiW12O40, H5PW11TiO40, H5PW11ZrO40, and H3PW11ThO39) and Dawson structure (α-H6P2W18O62, H6P2W21O71(H2O)3, H6As2W21O69(H2O), and H21B3W39O132). The reaction orders with respect to H6P2W21O71(H2O)3, H3PW12O40, and H6P2W18O69are equal to 0.78, 1.00, and 0.97, respectively. It was found that the reaction rate depends on the acidity, as well as on the structure and composition of heteropoly acids. The H21B3W39O132heteropoly acid is most active, whereas the Keggin-structure heteropoly acids exhibit the lowest activities. Of the Keggin structure heteropoly acids, H5PW11ZrO40exhibits the highest activity because of the presence of a Lewis acid site in its structure.