| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 102 === Environmental Protection Agency began to implement the Indoor Air Quality Management Act in 2012. Formaldehyde (HCHO) is one of the indoor air pollutants, and standard value of formaldehyde concentration is 0.08ppm in Taiwan. Sources of interior formaldehyde include outdoor source and indoor source. Outdoor source include power plant, incinerator, petroleum refinery, factory waste gas and vehicle exhaust emissions. Indoor source include wooden furniture, consumer products, paint and cooking. Formaldehyde is harmful to human health, such as eyes, nose and mucosal tissues irritation, and IARC (International Agency for Research on Cancer) classified it as carcinogenic to humans.
The P25 TiO2 supported Pt catalysts were using chloroplatinic acid (H2PtCl6) as the Pt precursor compound, and prepared by photo-deposition method in this study. The catalysts would coat on honeycomb monolith which supply more reaction area. Through optical fibers, the UV lamp could irradiate into honeycomb monolith to excite catalysts, and estimate the first stage (unirradiated) and the second stage (irradiated with UV254nm) formaldehyde conversion. Formaldehyde was degraded by photocatalytic reactor, the reactor include Pt/TiO2 supported honeycomb monolith. Pt/TiO2 catalysts were characterized by using XRD, SEM-EDX, BET and ICP-MS. The gas flow rate was controlled at 1.4 LPM with formaldehyde inlet concentration ranged from 0.6ppm to 1.4ppm under RH 30%, 50% and 70%.
The BET surface area of Pt/TiO2 catalysts were increased to 51.2992±0.3640m2/g, and catalysts surface Pt loading were 4018μg/g. The first stage formaldehyde conversion is 51.87%±2.96%, second stage formaldehyde conversion is 94.29%±1.02% and total conversion is 97.27%±0.43%. These results demonstrated that various humidity and inlet concentration were not affect the activity of the catalysts. The oxidation rate constants of formaldehyde with inlet concentration ranged from 0.6ppm to 1.4ppm are increase from 0.46±0.01×10-3μ-mol/m2-s to 1.01±0.02×10-3μ-mol/m2-s at the first stage, and increase from 0.40±0.01×10-3μ-mol/m2-s to 0.99±0.02×10-3μ-mol/m2-s at the second stage. Formaldehyde conversion reaches 97.27%±0.43% when the weight of Pt/TiO2 catalysts coated on honeycomb monolith is 0.45±0.02g. Lin(2013) had used 3.27±0.05g P25 TiO2 to degrade low concentration formaldehyde, and HCHO conversion varied between 90% to 95%. Obviously, the Pt supported P25 TiO2 could reach higher formaldehyde conversion.
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