Effect of various iron impregnating agents on the characteristics and reduction activity of carbon supported catalysts

Autor: Chih-Liang Hung, 黃志良
Rok vydání: 2010
Druh dokumentu: 學位論文 ; thesis
Popis: 98
The purpose of this study is to prepare carbon supported catalyst via impregnating iron sulfate (ACS), iron chloride (ACC), and iron nitrate (ACN) and to apply for catalytic reduction of nitrogen oxide. The pore characteristics, morphology, and crystal form of iron oxides were analyzed by the BET, SEM/EDS, and XRD, respectively. The sorption/desorption properties were carried out by using the temperature programming desorption (TPD) measurement with ammonia, NO, and CH4. The reduction activity of catalyst in the selective catalytic reduction (SCR) and non selective catalytic reduction (NSCR) were also investigated. Base on the pore analysis, the iron chloride impregnated catalysts showed the superior surface area (over 900 m2/g) than the others. On the other hand, the iron nitrate and iron sulfate impregnated catalysts owned a higher iron content than the ACC with over 60% iron content in the catalyst. It was found that the reduction activity of catalysts strongly depended on the iron content, iron distribution, BET, and the crystal form of iron oxides. Based on the results of SCR, it was found that the ACN15 and ACS20 owned over 95% conversion with 1000ppm ammonia and NO in feed at 550℃. The conclusion was that the activity of reduction strongly depended on the iron content, crystal form of iron oxide (γ- Fe2O3), and BET of the catalysts. It was also indicated that the higher BET, iron content, and the right crystal form of iron oxides dominated the reduction activity of carbon catalyst. The experiment indicated that the increasing in impregnating concentration significantly decreased the BET in the case of ACN and ACS catalysts. Therefore, the optimum dosage of impregnating iron in the preparation is necessary to obtain the highly active catalysts. On the other hand, it was also found that the ACC did not show the similar activity as ACS and ACN. The low activity was due to the low γ- Fe2O3 content in the ACC catalyst. It was also indicated that the iron oxide (γ- Fe2O3) play an important role in the SCR to converse the NO to nitrogen. In the case of NSCR, it was found that the ACN and ACS catalysts owned an about 60% NO conversion rate with 1000ppm CH4 and NO in feed at 600℃. Base on the XRD analysis, it was indicated that γ- Fe2O3 did not show the superior activity. Though the iron content and BET were high in this case but the low conversions were also found with higher iron content and BET. It was indicated the activity of reduction in the case of NSCR was low than the SCR with the ACN and ACS. It is interesting to note that that ACC showed the less activity of reduction than the others. It was concluded that the high activity of ACS and ACN catalysts due to higher BET and γ- Fe2O3 content than the ACC catalysts. It was concluded that the reduction activity of carbon catalyst can be improved by increasing the BET and γ- Fe2O3 content in the matrix. Keywords: iron sulfate (ACS), iron chloride (ACC), and iron nitrate (ACN), γ- Fe2O3, selective catalytic reduction (SCR), non selective catalytic reduction (NSCR)
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