Photocatalytic oxidation of gas phase butyraldehyde

This work is composed of three parts: Part I. UV light irradiance and radiant flux measurements, Part II. Photo-reactor with distributed light sources, and Part III. By-product identification and reaction mechanisms.;At the same power supply, a photo-reactor with a uniformly distributed light source has high conversions, high carbon dioxide yields, and low by-product concentrations.;The kinetics can be fitted into the Lainguir-Hinshelwood model. Concentrations of propinonaldehyde and 1-propanol during the photocatalytic oxidation (PCO) of butyraldehyde are lower under UV light illumination than under black light illumination. At low input concentrations, the controlling step is the adsorption of butyraldehyde. At high input concentrations, intermediate concentrations increase and hinder the PCO. The rate-limiting step gradually changes to oxidation of 1-propanol. An activated carbon column and a glass bead column were used for by-product identification. The major by-products caused by C-C bond cleavage were propinonaldehyde, 1-propanol, ethanol, and acetaldehyde, whereas propyl formate and di-n-propyl ether were secondary by-products. The reductive coupling of propinonaldehyde and butyraldehyde may result in the formation of 3-heptene and some other related C7 olefins. Aldol condensation of the vapor phase aldehydes on TiO2 surfaces may be partially responsible for the formation of some minor by-products.;Part I describes a method for measuring UV light irradiances and their distributions on the inner surfaces of annular reactors and how operating conditions (power supply, reactor diameter, UVC or UVA lamps) influence the observed irradiances. The irradiances measured can be used to calculate radiant flux, heat loss, and efficiency of UVC and UVA lamps. UV absorption of TiO 2 catalyst can also be calculated from the measured irradiances. The relationship between UV light irradiance and lamp power supply can be described with a logarithmic function. The main energy loss is the adsorption of UV light by the lamp glass. A UVC lamp has its maximum efficiency (=23%) whereas the maximum light efficiency of UVA lamp is 7%, all at about one third of the full power supply. The aging of a UV light causes a 20% radiant flux loss. The molar absorptivities of Ti02 are 64.44 cm2/g for UVC lamp and 30.45 cm2/g for black lamp, respectively.