The Investigation on Gas-phase Photocatalytic Oxidation of MTBE And Its Degradation Pathways

• Main Authors: Rui-ming Lai, 賴瑞明
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/58053793427894788007

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 92 === Gas-phase photocatalytic oxidation of methyl tert-butyl ether (MTBE) was investigated in this study. Series of experiments for MTBE photocatalysis were conducted in a bench-scale annular photocatalytic reactor, in which Degussa P-25 TiO2 was immobilized on glass pellets as photocatalysts and a 15 W near-UV lamp (350 nm) was applied as a light source. Several experimental parameters including MTBE influent concentrations (50~450 ppmv), water vapor content (1500~ 23000 ppmv), oxygen concentrations (1~ 20 %), and reaction temperatures (30 to 120 C) were tested for investigating degradation characteristics of MTBE. Besides, the major reaction products/byproducts under different reaction conditions were particularly interested in this research. The reaction products were qualified and quantified in the investigation. A degradation dynamic kinetic was also proposed to simulate degradation rates of MTBE under various reaction temperatures. The experimental results showed that MTBE reaction rate increased with increasing its influent concentration. Water vapor would compete with MTBE for active sites on TiO2 surfaces and would result in the deterioration in MTBE degradation rates when water vapor concentrations were too high. Typical heterogeneously catalytic reaction patterns were observed for MTBE degradation under different oxygen concentrations. That is, first-order reaction kinetics were detected for MTBE decomposition as oxygen concentration was low, but zero-order reaction kinetics were observed for MTBE decomposition after adsorption saturation of oxygen by TiO2. For the effect of reaction temperature on MTBE degradation, it was observed that the higher temperature, the slower degradation rates were detected especially the temperature above 120 C. A bimolecular Langmuir-Hinshelwood kinetic model was applied to simulate photocatalysis of MTBE and showed well fit the experimental results. Except CO and CO2, both acetone and tert-butyl alcohol (TBA) were two major reaction product/byproduct from photocatalysis of MTBE. It was observed higher formation concentration of TBA but lower formation concentration of acetone when more water vapor was involved in the reaction. Opposite formation pattern was observed for the effect of oxygen content on the formation concentrations of acetone and TBA. More formation of acetone was detected while oxygen concentration was higher, but less formation of TBA for a higher oxygen concentration. For the influence of reaction temperature on the formation of acetone and TBA, acetone formation concentrations were increased but TBA formation concentrations were decreased with increasing reaction temperature. Keywords: MTBE, photocatalysis, Langmuir-Hinshelwood model, temperature effect, reaction pathway