Removal Of VOCs Over Monolithic Catalysts By Catalytic Combustion

Air pollution by VOCs has drawn considerable attention in recent years. Among the technologies developed for the treatment of VOCs, the catalytic combustion is considered to be a promising technology. VOCs, especially cooking fume and ethanol, are typical pollutants emitted from industrial sources and difficult to degrade due to their stability. Volatile organic compounds (VOC) removal from air by catalytic combustion techniques has been paid much more attention to in recently. However, none of catalysts can make VOCs combustion completely under low temperature and no by-products. Based on the two kinds of catalysts supports of oxygen storage materials and Al2O3, a kind of low light-up temperature and high selectivity catalysts was prepared. The main contents and results in this thesis can be summarized as follow:1. The influences of Ce/Zr ratio on the oxygen storage capacity (OSC) and textural characteristics of CeO2-ZrO2 oxygen storage materials (OSM) have been investigated. The results show that Ce/Zr ratio has great effect on the OSC and textural characteristics of OSM.2. The influences of Mn doped and preparation method on the oxygen storage capacity (OSC) of CeO2-ZrO2 solid solution have been investigated. The results show that different preparation methods have great effect on the OSC of OSM. The fresh samples prepared by coprecipitation method haven't the highest OSC and specific surface area, but after aged at high temperature, they have the best thermal stability, the highest OSC and specific surface area. Among the CeO2-ZrO2 solid solutions with different Mn addition, the OSM containing 20% Mn exhibits the best thermal stability, the highest OSC after ageing.3. Three monolithic catalysts with low noble metal content were prepared by immergination method (Pt/γ-Al2O3, Pt/La-Al2O3, and Pt/YSZ-Al2O3). Pt/La-Al2O3 catalyst exhibits higher activity than Pt/γ-Al2O3 and Pt/YSZ-Al2O3. Addition of La2O3 into Al2O3 decreases the interaction between Pt and Al2O3 and increases the concentration of Pt species on the surface of Pt/La-Al2O3 catalyst, which results in improvement of catalytic activity of the catalyst.4. Using oxygen storage materials as support improves the catalytic performance of Pt/La-Al2O3 catalyst, in particularly, when m(OSM):m(La-Al2O3) is 1:1, the Pt/Ce0.5Zr0.5O2-La-Al2O3 catalyst possesses the best catalytic capability.5. The effects of Ce/Zr ratio of oxygen storage materials on the property of catalytic activity were studied. When Ce/Zr ratio is 1:1, Pt/Ce0.5Zr0.5O2-La-Al2O3 catalyst possesses the best catalytic capability. In this work, we have investigated the Mn amount in enhancing the catalytic activity of Pt/La-Al2O3/Ce0.5-xZr0.5-xMn2xO2. The catalytic activity of Pt/La-Al2O3/Ce0.4Zr0.4Mn0.2O2 is the best.6. The monolithic catalyst was prepared using modifiedγ-Al2O3 as support, among the four kinds of modifiedγ-Al2O3, Cr- Al2O3 was the best. In this work, the effect of Cr2O3 amount, Pt loading amount and space velocity on catalytic activity was investigated in detail. The results show that the optimal Cr2O3 amount is 3wt%, the optimum Pt loading amount is 0.7g/L and the monolithic catalyst can be used in wide space velocity.7. The catalytic activity of catalyst with the coating amount is 20% by weight of the substrates is better, which ensures the activity of the catalysts and service life time of the catalysts. The activity could be improved by increasing cell density of the substrates.8. CeO2-ZrO2 solid solution was prepared by co-precipitation method and characterized by X-ray diffraction, Raman spectra, BET, oxygen storage capacity and temperature-programmed reduction measurements after calcination at 100℃, 300℃, 600℃and 1000℃.The results show that the precipitation is a crystalline of fluorite structure and in the process of the precipitation the fluorite structure transforms into CeO2-ZrO2 solid solution, the fluorite structure of the precipitation kept unchanged. After 1000℃, there did not appear the other crystalline phase. The samples have excellent oxygen storage capacity, reduction perproty and higher thermal stability.9. The influences of Y and La doped on the oxygen storage capacity (OSC) and textural characteristics of CeO2-ZrO2 solid solution have been investigated. The results show that doping Y and La into CeO2-ZrO2 solid solution can improve OSC, textural characteristics and reduction property of CeO2-ZrO2 solid solution. The OSM containing 10% Y or La exhibits the best thermal stability, the highest OSC after ageing.10. Using oxygen storage materials as support improves the catalytic performance of MnOx/La-Al2O3 catalyst.In particularly, when m (OSM): m (La-Al2O3) is 1:1, the MnOx/Ce0.5Zr0.5O2-La-Al2O3 catalyst possesses the best catalytic capability.11. The effects of Ce/Zr ratio of oxygen storage materials on the catalytic activity were studied. In particularly, when Ce/Zr ratio is 1:1, the Pt/Ce0.5Zr0.5O2-La-Al2O3 catalyst possesses the best catalytic capability. 10%MnOx loading is optimal for the catalytic activity of MnOx/Ce0.5Zr0.5O2- La-Al2O3 catalyst. The catalytic activity of MnOx/La-Al2O3/Ce0.5Zr0.5O2 monolithic catalyst towards the catalytic combustion of ethanol can be greatly improved by doping three metals (M=Y, La, Mn) into Ce0.5Zr0.5O2.Catalytic activity of MnOx/La-Al2O3/Ce0.45Zr0.45M0.1OX (M=Y, La, Mn) is better than that of MnOx/La-Al2O3/Ce0.5Zr0.5O2. The OSM containing 10% Y or La exhibits the best catalytic activity. The OSM containing 20% Mn exhibits the best catalytic activity.