Photocatalytic oxidation air cleaner: Identification and quantification of by-products

Ultraviolet photocatalytic oxidation (UV-PCO) has been acclaimed to be a unique technology for decomposition of indoor environment VOCs while minimizing the building energy consumption. This paper addresses application of photocatalytic oxidation for indoor air treatment. Laboratory experiments were conducted in a pilot scale open test rig with an in-duct UV-PCO system. The UV-PCO reactors contain two types of flat commercially available catalyst substrates irradiated by two types of UV-lamps. UV-PCO system was challenged with aromatic: toluene, p-xylene; alcohol: 1-butanol; alkane: n-hexane, octane, and ketone: MEK, acetone. The main objectives of this study were to identify and quantify produced by-products in a large pilot scale reactor in the presence and absence of ozone. Moreover, a detailed investigation was made in order to reveal the effect of type of photocatalyst, UV-lamps as well as initial concentration on the distribution and production of by-products and removal efficiency. It was noticed that there were two common by-products including formaldehyde and acetaldehyde for all challenge compounds; moreover, some other by-products including propionaldehdye and crotonaldehyde were formed. More by-products were formed in the tested aromatic compared to the other compounds. Performance of UV-PCO system and generated by-products of challenge compounds were investigated and compared in the presence of UVC and VUV lamps, and two types of catalysts. Generally higher removal efficiency was achieved in the presence of ozone and VUV lamps compared to the UVC lamps.