GAS-PHASE PHOTO-ASSISTED MINERALIZATION OF VOLATILE ORGANIC-COMPOUNDSBY MONOLITHIC TITANIA CATALYSTS

A new monolithic catalyst based on Pt/TiO2 has been developed for the photocatalytic destruction of traces of organic pollutants present in gaseous emissions. The influence of both the raw materials used in the preparation of the support (titanias and magnesium silicates) and the nature of the doping phase (Pt or V2O5) on the properties of the cata lysts have been studied. Finally, a hydroxylated titania gel was selec ted as a catalyst precursor, a mixture of magnesium silicates as inorg anic binders and platinum as the doping phase. The developed monolithi c catalyst can be described as composed of platinum dispersed over the surface of titania-anatase particles, which were intimately mixed wit h the fibrous magnesium silicate. Using the selected catalyst, trichlo roethylene photocatalytic oxidation tests showed complete mineralizati on at operating temperatures between 80 degrees C and 110 degrees C, a nd residence times lower than 0.03 s without any thermocatalytic contr ibution. Although toluene did not reach appreciable photoactivity betw een 130 degrees C and 200 degrees C and a residence time of 0.06 s, th is compound can be completely oxidized between 250 degrees C and 300 d egrees C with the help of infrared radiation without significant produ ction of by-products. Consequently, the operating conditions needed to achieve the complete mineralization of the VOC by photocatalytic oxid ation are strongly dependent on the type of compound to be removed. (C ) 1998 Elsevier Science B.V.