Various volatile organic compounds (VOCs) have been emitted from numerous industries process, many of which in common use are toxic and some are considered to be carcinogenic or mutagenic. Recently, a variety of photocatalytic processes have been studied for treating gaseous streams containing VOCs. However, recombination between electron/hole pairs resulted in low quantum yields for most photocatalytic reactions. Various methods were developed to modify the structural and morphological properties of TiO2 catalyst by doping several metals, such as Pt, Ag, and Au to enhance the photocatalytic activity of TiO2 due to the increase of electron transfer rate to the oxidant and enable visible light absorption by providing defect states in the band gap.
The gaseous 2-propanol (isopropanol, IPA) which was decomposed by UV/TiO2 process in an annular photoreactor was influenced by UV light intensity, initial gaseous concentration, relative humidity and so on. In the gaseous photoreduction, the experimental parameters were focused on relative humidity, differential initial concentration, retention time and light intensity, etc. Experimental results obtained in this study demonstrated that UV/TiO2¬ photocatalytic process is capable of carrying the reduction of carbon dioxide in gaseous steams. The primary reduction products from the reduction of carbon dioxide were determined to be methane and methanol.
The objective of this research was to investigate the reaction behavior of both the photooxidation of gas-phase volatile organic compounds and the reduction of carbon dioxide in the presence of titanium dioxide, and to develop a photoreactor. A new-type optical fiber photoreactor was investigated for treatment of gaseous acetone, formaldehyde and IPA. After changing the initial concentration of acetone, methylethylketone (MEK), formaldehyde and IPA, from 30 ppmv to 180 ppmv, the degradation rate of these pollutants were from 61 % to 31 %, 52 % to 25 %, 82 % to 46 % and 67 % to 42 %, respectively.
In this study, experimental results indicate that the deposition of 0.04 wt% Pt on TiO2 film exhibited the highest photocatalytic activity among all the composition investigated.The new photoreactor was introduced as a superior photoreactor to decompose VOCs. Experimental results showed higher apparent quantum yields were obtained compared with the annular reactor.
In order to simulate the actual discharge of factory, the array-photocatalytic reactor was developed and the initial concentration of IPA was increased to 550 ppmv. However, the photodegradation of IPA remained at 67 % in an array-photocatalytic reactor. The results indicated that new photoreactor seems to be more energy-efficient than the annular reactor, which suggested an appropriately designed reactor could be a potential alternative in photocatalytic gas-phase organic compounds treatment.
