TITANIUM(IV) OXIDE PHOTOCATALYST OF ULTRA-HIGH ACTIVITY FOR SELECTIVEN-CYCLIZATION OF AN AMINO-ACID IN AQUEOUS SUSPENSIONS

Titanium(IV) oxide (TiO2) powder was prepared by the high-temperature hydrolysis of titanium(IV) tetrabutoxide in toluene as anatase crystal lites of average diameter approximate to 15 nm. They were platinized b y impregnation from aqueous chloroplatinic acid solution followed by h ydrogen reduction. The catalyst was suspended in an aqueous L-lysine ( Lys) solution and photoirradiated under argon at ambient temperature t o obtain L-pipecolinic acid (PCA). Among several platinized commercial TiO2 powders, the present TiO2 showed the highest photocatalytic acti vity for both Lys consumption and PCA production. This result is attri buted to both the higher activity owing to the larger surface area wit h lesser defects and the higher dispersion of platinum deposits acting as an efficient reduction site for a Schiff base intermediate into PC A.