| Summary: | 碩士 === 大同大學 === 化學工程研究所 === 91 === ABSTRACT
In air pollution control, the most advanced flue gas treatment technique is the selective catalytic reduction. This research is to develop the high-performance vanadium-molybdenum oxide catalysts for removing nitrogen-oxides. Concerning the supports, sol-gel method was used to prepare three different kinds of bimetallic oxide supports : Al2O3-TiO2, Al2O3-SiO2 and TiO2-SiO2. Active catalysts of 4 wt% V2O5, 6 wt% MoO3 and 3 wt% NH4Br were impregnated individually on carriers, and then product-catalysts were formed after the 550 ℃ high-temperature-calcination. Among them, NH4Br can increase the applicable temperatures of the catalyst for removing nitrogen-oxides.
The tests of the characteristics of SCR catalysts were carried out by TGA, TPR, XRD, BET and SEM. The SCR reaction was carried out in the fixed-bed reactor. The simulating flue gas which contained NOx flowed through reactor in the presence of O2 and ammonia gas was used as the reducing agent to reduce NOx into N2 for measuring the effects of V2O5, MoO3 and NH4Br in various of catalysts and of different supports on the activates of the catalysts and for finding the best composition of the SCR catalyst of the de-nitrogen oxide reaction.
The experimental result shows that among the bimetallic oxide supports prepared by the sol-gel method, TiO2-SiO2 possesses good crystallinity and porosity. From TPR diagrams, it is known that the reduction temperatures of the active catalysts can be retarded decreased by adding the addition of 3 wt% NH4Br, showing that the chemical broken of V2O5 and MoO3 are not easy to be reduced. Among this series, the conversions of NO are not easy to reach 90% at the reducing temperature of 450 ℃ by using the catalysts with Al2O3-TiO2 and Al2O3-SiO2 as the supports, and the conversions can reach 100% at the reducing temperature above 300 ℃ by using the catalysts with TiO2-SiO2 as the supports; whereas, the conversion can reach 100% at the reducing temperature of 200 ℃ by using the V2O5-MoO3-NH4Br/TiO2-SiO2 catalyst, showing that this is the best composition.
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