Preyssler's anion, with formula [NaP5W30O110]14-, catalyzes the oxidation of aromatic aldehydes to related carboxylic acids by hydrogen peroxide as oxidizing agent, under microwave irradiation, or at 70 ºC. Both homogeneous and heterogeneous Preyssler's catalysts (as H14[NaP5W30O110 ]) were used and had their activity compared with those of some Keggin structures. Our data indicate that Sodium30-tungsto pentaphosphate, the so-called Preyssler's anion, with high hydrolytic (pH=0-12) and thermal stability is the best catalyst with high yield and good selectivity. Under microwave irradiation, this polyanion supported on SiO2 was found to be an excellent catalyst for aldehydes with low loss factor in 1-2 min (the loss factor is a measure of the ability of the material to dissipate energy). The effects of various parameters, including catalyst type, nature of the substituent in the aldehyde and temperature, on the yield of the carboxylic acids were studied.
Preyssler's anion; catalyst; heteropolyacid; oxidation; benzaldehyde; benzoic acid
