Isoamyl acetate production catalyzed by H3PW12O40 on their partially substituted Cs or K salts

The Cs2.9H0.1PW12O40, Cs2.6H0.4PW12O40, K2.9H0.1PW12O40 and K2.5H0.5PW12O40 salts were synthesized and impregnated by means of the incipient wetness method with a H3PW12O40 solution in ethanol-water. The solids were characterized by N-2 adsorption-desorption isotherms, FT-IR, XRD, P-31 MAS-NMR, thermogravimetric and differential thermal analysis, and the acidic behavior was studied by potentiometric titration with n-butylamine and isopropanol dehydration. The proton content evaluated from the thermogravimetric weight loss in the temperature zone ascribed to the deprotonation step showed a good agreement with the values drawn from the synthesis stoichiometry. The physical-chemical characterization led to establish the presence of the Keggin salt structure and well dispersed acid impregnated on the partially substituted salts. The mainly microporous salts as well as the impregnated salts possessed higher acidity than the bulk acid. Their catalytic activity in the esterification of acetic acid and isoamyl alcohol to obtain isoamyl acetate showed a straight correlation with the acidic characteristics of the studied solids. Both the high conversion and selectivity obtained are important results for the use of these type of heteropolycompounds mainly in the flavor and fragrances industries. (C) 2003 Elsevier B.V. All rights reserved.