Indoor air chemistry and cleaning: Visible light photocatalyst development and characterization and linalool ozone chemistry.

摘要

Cerium and iron based titanium dioxide catalysts are made at varying concentrations and cured at different temperatures to develop a new class of photo catalysts that display catalytic activity for volatile organic compound destruction when irradiated with visible light. These catalysts are characterized using X-ray diffractometry, Raman Spectroscopy, UV Vis Diffuse Reflectance Spectroscopy and BET Surface Area analyses. Although both cerium and iron based titania show destruction of these volatile organics in visible light as compared to pure titania, cerium based titania has better performance than iron based titania. It has been found that cerium doped titania developed in this study performs comparable to the commercially available titania even when irradiated with visible light. Toluene, ethanol and acetaldehyde were the model compounds employed to test the photocatalyst coated on the inner surface of an annular plug flow reactor.;Linalool ozone reactions were conducted in two stainless steel chambers and the gas and particle phase chemistry have been studied. A preliminary analysis of the gas and particle phase products have been performed and a number of intermediates including 2-ethenyl-2-methyl-5-hydroxytetrahydrofuran, 2(3H)-furanone-5-ethenyldihydro-5-methyl-, tetrahydro-1-methyl-5-oxo2-furancarboxylic acid and 2-hydroxy,2-methyl-pentanedioic acid have been identified. The particle size distributions of the aerosol particles produced due to these reactions have been obtained. It is concluded that the concentration of linalool and ozone play a vital role in the formation and growth of particles. Yields of the products in the particle phase have also been obtained to study the partition of organics produced in the gas and particle phase. In addition to these studies, the reactive oxygen species (ROS) produced by these reactions for two different secondary organic aerosol size ranges of 2 --200 nm and greater than 200 nm have been obtained. Results show that although the secondary organic aerosol mass formed for linalool ozone system is low compared to other terpene due to the formation of compounds with low number of carbon atoms, the concentration of ROS produced is high. The study provides an understanding of the relation between ROS concentration to source concentration and particulate size. In addition, the thesis also shows that the concentration of ROS in fine particles that can deposit on respiratory tracks is significantly large and can result in negative health effects.