Thermal Stability and Acidic Strength of Preyssler‐Type Phosphotungstic Acid, H14[P5W30O110Na] and It's Catalytic Activity for Hydrolysis of Alkyl Acetates

Abstract

AbstractFull structural analysis of Preyssler‐type phosphotungstic acid, H14[P5W30O110Na], using 183W NMR, 31P NMR, and IR spectroscopy, as well as complete elemental analysis revealed that H14[P5W30O110Na]·44H2O was obtained in pure form. H14[P5W30O110Na] started to decompose by heating at 373 K and was less stable than Keggin‐type phosphotungstic acid, H3PW12O40·6H2O, which was stable even after heating at 673 K. Acidic strength measurements using trimethyl phosphine oxide (Me3P=O) as a probe molecule indicated that the acidic strength of H14[P5W30O110Na] was greater than that of H3PW12O40 on the basis of the amount of acid in an aqueous solution. H14[P5W30O110Na] was less active than H3PW12O40 for hydrolysis of alkyl acetates on the basis of acid amount. However, H14[P5W30O110Na] was more active than H3PW12O40 for hydrolysis of alkyl acetates with small alkyl groups on the basis of catalyst weight because acid amount per weight of H14[P5W30O110Na] was about two times higher than that of H3PW12O40.