The Catalytic Incineration of Chlorinated Volatile Organic Compounds Over a γ-Alumina Supported Manganese Oxide Catalyst

• Main Authors: Ting-Ke Tseng, 曾庭科
• Other Authors: Hsin Chu
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/48768114174433393557

博士 === 國立成功大學 === 環境工程學系碩博士班 === 91 === 　　Halogenated VOCs emissions are associated to a wide range of industrial processes, for instance, trichloroethylene (TCE), dichloroethane (DCEA) and Trichloromethane (TCM) are mainly used in metal degreasing processes and known to be hazardous to the environment and public health. The chlorinated VOC decomposition over a Mn2O3/γ-Al2O3 catalyst in a fixed bed reactor was conducted in this study. Preliminarily, three catalysts including Mn2O3/γ-Al2O3, NiO/γ-Al2O3 and Pt/γ-Al2O3 were used to incinerate TCE and the results show that the Mn2O3/γ-Al2O3 catalyst has the best performance. 　　The Mn2O3/γ-Al2O3 powders were prepared by the incipient wetness impregnation method with aqueous solutions of manganese nitrate. The catalysts were characterized by DTA-TGA, XRD, porosity analysis, SEM, EDX, and XPS. The results show that the main distinct weight loss is found at the temperature around 373K and 873K, the MnO is the only observed crystal phase on the fresh catalyst, the SEM image of the MnO impregnated γ-Al2O3 support is much different from the calcined catalyst, and the Mn element quantity on the catalyst surface is higher than that of the impregnated support. 　　The effects of operating parameters, such as inlet temperature, space velocity, Cl-VOCi inlet concentration, and oxygen concentration on the catalytic incineration of Cl-VOCi over the Mn2O3/γ-Al2O3 catalyst were then performed. The results show that conversion of Cl-VOCi increases as inlet temperature and oxygen concentration increase, and decreases with the increases of Cl-VOCi concentration and space velocity. 　　The activity of the catalyst decreases significantly with time while TCE incineration is operated under a low temperature, 365°C. However, the activity of the catalyst does not change much while the operating temperature is as high as 500°C. The catalysts were characterized by the surface and pore size analysis, XRD, XPS, EDS and SEM before and after the tests. The results show that the catalytic crystal is Mn2O3, the catalytic deactivation is not due to carbonaceous material, and the chlorine element is adsorbed on the surface of catalysts. 　　The products and reactants distributions from the oxidation of Cl-VOCi over Mn2O3/γ-Al2O3 were analyzed by GC. The results show that the TCE conversion starts from 5% at 443K, then rises to 100% in the 673~873K ranges, and the CO2 yield also pushes to 99% at the same temperature ranges. HCl and Cl2 are the other main products with little halogenated VOC intermediates. 　　The results of the DCEA destruction show that the DCEA conversion starts from 15% at 450K, then rises to 100% in the 700~800K ranges, and the CO2 yield also pushes to 100% at the same temperature ranges. HCl and Cl2 are the other main products with little halogenated VOC intermediates. 　　The products and reactants distributions from the oxidation of TCM over MnOX/γ-Al2O3 were carried out too. The results show that the TCM conversion starts from 7% at 523K, then rises to 100% in the 700~800K ranges, and the CO2 yield also pushes to 100% at the same temperature ranges. HCl and Cl2 are the other main products. 　　Experimental results indicate that the oxidation kinetic behavior of TCE, TCM and DCEA with the catalyst can be expressed by using the rate expression of the Mars and van Krevelen model and the power-rate law, respectively. The experimental data are also compared with those predicted from the kinetic model by substituting the same condition with experiment state. 　　A study of detailed chemical kinetic mechanism describing the catalytic incineration of TCM is presented. The mechanism involves the participation of 41 species in 87 elementary reactions. This mechanism is subsequently used to calculate the stable species concentration of the reactor exit of the TCM catalytic incineration over the Mn2O3/γ-Al2O3 catalyst. Calculations are performed by using the Chemkin III PLUG code. Result show that the catalyst is the significantly role of the catalytic incineration of TCM over the Mn2O3/γ-Al2O3 catalyst.