Micro-Sized TiO2 for Toluene Photodegradation in Gas Phase: catalyst preparation and role of doped metal to increase the photo-activity

Micro-Sized TiO2 for Toluene Photodegradation in Gas Phase: catalyst preparation and role of doped metal to increase the photo-activity. Indoor air pollution is a problem not to be underestimated because of two reasons: firstly, because the majority of the population spends about 80-90% of the time in these places and secondly, because the risk is affects almost the entire population. Pollutants are classified in three big categories: chemical, physical and biological; VOC's, formaldehyde, toluene, benzene, carbon monoxide, carbon dioxide and nitrogen dioxide fall in the category of chemical agents. Industrial age caused an increase of indoor pollution and chemical substances like formaldehyde, xylene or toluene could making the air inside homes to 20 times more polluted than outdoor air. In fact, toluene and xylene are in many household and educational products, well as they are emitted from the exhaust gases of cars; in particular, they are widespread because they are ubiquitous. Titanium dioxide is a semiconductor material that has good catalytic properties and is able to degrade numerous organic compounds by oxidation; its molecules exposed to light catalyse the oxidation of organic residues in water and carbon dioxide. In this work, catalysts based on titanium dioxide were tested and improved in particular on the degradation of toluene. P25 was the sample reference for nanometric powders, and its activity was compared with Kronos 1077, which consists of micrometric particles. Kinetics are carried out in a glass Pyrex reactor with a 200 mm diameter and a 5,5 L volume. Located 50 cm above the reactor there is an UV lamp; its power is 500 W and the wavelengths of the emissions are between 100 and 400 nm. The power calculated on the catalyst surface is 30 W\m2. A gas chromatograph tracked the toluene and carbon dioxide concentrations inside the reactor. Although micrometric sample showed a lower activity than P25, it is possible to modify it, in particular with metals, and improve its final performance. Finally, the toluene kinetic reaction pathway was studied as well, and the main by-products were analyzed and classified.