Catalystic Combustion Of 1,2-dichloroethane Over CeTiO_x Supported Ceramic Honeycomb Catalysts

Volatile organic compounds (VOCs) are harmful to people and have a significant impact to the air quality; the research on the removal of VOCs has attracted increasing interests during the last decade. Catalytic combustion is one of effective methods for the control of volatile organic compounds. 1,2-dichloroethane (1,2-DCE) is one of typical chlorinated volatile organic compounds. In this thesis, a series of Ti based mixed oxides washcoat on the cordierite monolith were synthesized and tested for catalytic combustion of 1,2-DCE. Several experimental factors,such as coating, catalytic activity and stability and other impacts of the combustion reaction were investigated. The kinetic of the combustion reaction of 1,2-DCE over CeTiO_x supported honeycomb was studied.The cordierite honeycombs directly coated with Ti-based mixed oxides were prepared by sol-gel method. The results indicated that the washcoat showed excellent adhesion to the substrate according to an ultrasonic test, the weight loss was less than 10%. The loading of catalysts showed higher activity in combustion than the catalyst powder, and the adsorption capacity of 1,2-DCE over the coating was 60~80 mg/g.MTiO(xM=Ce;Cu;Mn;Ni;Cr)composite oxide coating was prepared by adding different metal nitrates into Ti sol, and the results showed that CeTiO_x mixed oxides had the highest catalytic activity. With increasing calcination temperature, the particles of active species became larger, which leaded to a decreasing activity of 1,2-DCE combustion. The combustion temperature for the 99% of 1,2-DCE conversion (T99%) over CeTiO_x calcinated at 200℃was 325℃, while the T99% over CeTiO_x calcinated at 600℃was above 400℃. Comparing various ratios of Ce to Ti, 20wt.% CeTiO_x washcoating materials calcinated at 400℃showed the best catalytic activity, the T99% was close to 350℃. CeTiO_x had a high specific surface area which was 175 m2/g and good dispersion on the ceramic honeycomb, so loading porous materials as the second coating and impregnating precious metals could not improve the catalytic activity.The reaction carried out in a fixed-bed reactor and the results showed the effect of internal and external diffusion was successfully eliminated in the reaction system. Oxygen had no significant effects for the catalytic combustion when the concentration of oxygen was more than 5%. The reaction was one order and the index in kinetic model rA=7495×exp(-9041/RT)×CA were calculated and fitted. The data for different reaction temperature and (weight hourly space velocity)WHSV were fitted Arrhenius law and the results verified one order reaction very well.