Stability and performance of silica gel-supported triphenylpyrylium cation as heterogeneous photocatalyst

Pyrylium salts are known to be good photocatalysts in aqueous solutions, able to achieve the photodegradation of several phenolic pollutants. Nevertheless, they exhibit a limited stability in these media. The rate of the hydrolytic reaction depends on the pH of the solution, the intensity of irradiation and the pyrylium concentration. Silica gel plates have been employed as inorganic support of the pyrylium cation in order to improve its stability and performance as a heterogeneous catalyst. The resulting material has been tested using ferulic acid as a model compound. Important degradation yields have been achieved (up to 80% after 6 It of solar irradiation). The catalyst is stable under these conditions and can be easily recovered for further use. (C) 2002 Elsevier Science B.V. All rights reserved.