KEGGIN HETEROPOLY ACIDS AS AN EFFICIENT CATALYSTS FOR PHOTOCATALYTIC OXIDATION OF AROMATIC ALDEHYDES

Photocatalytic oxidation of aromatic aldehydes to related carboxylic acids was investigated in the presence of some Keggin heteroploy acids as phosphomolybdic acid H3PMo12O40 (PMo), silicotungestic acid H4SiW12O40 (SiW) and phosphotungstic acid H3PW12O40 (PW). Keggin acids can catalyze the oxidation of 4-carboxybenzaldehyde (4-CBA) and p-tolualdehyde (p-Tol) under homogeneous reaction. Also, for additional studies, we reconnoitered the application of Keggin catalyst in the presence of persulfate (PS) as oxidizing agent. ­­­­­­­­­Our results showed that in the presence of PS and (6 watt)UV light, the most active catalyst among the used Keggin acids is the phosphomolybdic acid (80.9% yield) due to the high oxidative ability of molybdenum . The effects of catalyst concentration, time and oxidant load have been studied. The mechanistic aspects of the reaction also have been discussed.