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A series of catalysts of manganese oxide, manganese–cerium and iron–manganese oxide supported on USY (ultra-stable Y zeolite) were studied for the low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. It was found that MnOx/USY have high activity and high selectivity to N2 in the temperature range 80-180 °C. The addition of iron and cerium oxide increased NO conversion significantly although the single-component Fe/USY and Ce/USY catalysts had low activities. Among the catalysts studied in this work, the 14% Ce-6% Mn/USY showed the highest activity. The results showed that this catalyst yielded nearly 100% NO conversion at 180 °C at a space velocity of 30 000 cm3 g-1 h-1. The only product is N2 (with no N2O) below 150 °C. The effects of the concentration of oxygen, NO and NH3 were studied and the steady-state kinetics were also investigated. The reaction order is 1 with respect to NO and zero with respect to NH3 on the 14% Ce-6% Mn/USY catalyst at 150 °C. 相似文献
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K. Krishna G.B.F. Seijger C.M. van den Bleek M. Makkee Guido Mul H.P.A. Calis 《Catalysis Letters》2003,86(1-3):121-132
Fe-ZSM-5 catalysts were prepared by subliming FeCl3 into H-ZSM-5. The method used allowed Fe-ZSM-5 catalyst preparation by FeCl3 exchange at a desired sublimation temperature and was found to be more precise. The sublimation of FeCl3 into H-ZSM-5 was carried out at 320 and 700 °C. Fe-ZSM-5 prepared by sublimation of FeCl3 at 320 °C followed by rapid heating to 700 °C and the catalyst prepared by subliming FeCl3 at 700 °C were found to be more active for NO reduction with NH3 in the presence of simulated exhaust gases containing water vapor than catalysts prepared by subliming FeCl3 at 320 °C. To determine the active sites, the catalysts were characterized by H2-TPR, in situ DRIFTS of NO adsorption, NH3-TPD, XRD and chemical analysis methods. The observed NO conversion differences in selective catalytic reduction using NH3 could be correlated to the iron cation species present at different locations determined from diffuse reflectance infrared spectroscopy. Enhanced NO reduction activity was obtained when positions in Fe-ZSM-5, corresponding to Fe2+(NO) band at 1877 cm-1 in DRIFTS, were preferentially occupied. 相似文献
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Joo-Hyoung Park Jong-Hyun Choung In-Sik Nam Sung-Won Ham 《Applied catalysis. B, Environmental》2008,78(3-4):342-354
The N2O decomposition activity of Fe-ZSM-5 strongly depends on the iron content and the preparation methods, including wet (WIE) and solid state ion exchanges (SSIE). The state of Fe species formed on the surface of a series of Fe-ZSM-5 catalysts containing a variety of Fe contents with respect to the preparation method and their role for N2O decomposition activity have been systematically examined. The general trend for the decomposition activity of Fe-ZSM-5-SSIE is higher than that of Fe-ZSM-5-WIE, indicating the formation of a distinctive local structure of Fe on the catalyst surface during the course of the ion-exchange procedure. Based upon the Fourier transformed Fe K-edge EXAFS spectra for the series of Fe-ZSM-5-SSIE and -WIE catalysts, most of the Fe species on the surface of Fe-ZSM-5-SSIE with high Fe loading are well dispersed in the form of oxygen-bridged binuclear Fe species. The turnover frequency (TOF) for N2O decomposition under dry and wet conditions has been confirmed assuming that Fe-ZSM-5-SSIE samples with Fe/Al = 0.20 and Fe/Al = 0.65 only contain mononuclear and binuclear Fe species, respectively, as active reaction species on their surface. The high performance of Fe-ZSM-5-SSIE may be mainly due to the formation of the binuclear Fe species onto its surface during the preparation of the catalyst. 相似文献
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Low-temperature SCR of NO with NH3 over AC/C supported manganese-based monolithic catalysts 总被引:4,自引:0,他引:4
Metal oxide/active carbon/ceramic (MOx/AC/C) monolithic catalysts were prepared by impregnation method for selective catalytic reduction (SCR) of NOx with NH3 at low-temperature, and they also had been characterized by elemental analysis, N2-BET, XRD, SEM and NO-TPD. The adsorption capability of the monolithic catalyst was greatly enhanced due to the attached active carbon. An ultrasonic treatment was used to improve the impregnation process, and which can increase their catalytic activities. More than 90% NOx conversion could be achieved over the Mn-based monolithic catalysts at low-temperature, and which could be improved further by doping Ce, from 30% to 78% at 100 °C. Mn–Fe–Ce and Mn–V–Ce monolithic catalysts had better tolerance to SO2 than Mn or Mn–Ce monolithic catalysts. 相似文献
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Fe-ZSM-5 for Selective Catalytic Reduction of NO with NH3: A Comparative Study of Different Preparation Techniques 总被引:3,自引:0,他引:3
Fe-ZSM-5 are prepared by using four different techniques: conventional aqueous ion-exchange (CA), improved aqueous ion-exchange (IA), solid-state ion-exchange (SS) and chemical vapor ion-exchange (CV). All of the catalysts show very high activities for selective catalytic reduction (SCR) of NO with ammonia. However, the activities are different and follow the sequence of Fe-ZSM-5 (IA) > Fe-ZSM-5 (CA), Fe-ZSM-5 (SS) > Fe-ZSM-5 (CV). ESR results indicate that Fe3+ ions with tetrahedral coordination are the active sites for the SCR reaction. 相似文献
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受“水俣公约”和环境保护政策约束,研究和开发新型无汞催化剂是保障我国乙炔法制备聚氯乙烯未来发展的核心环节。无汞催化剂包括贵金属催化剂、非贵金属催化剂和非金属催化剂,其中贵金属催化剂被认为是最具有工业化应用前景的催化剂。本文概述了近年来国内外乙炔氢氯化贵金属Au、Ru、Pd和Pt催化剂的研究进展,重点综述了不同催化剂的活性组分、催化机理及催化剂的改性方法等方面的研究,分析了不同改性方法的作用机制及不同催化剂改性的研究方向。研究表明,添加助剂或多金属复配、配体和离子液体的使用及载体改性均使贵金属催化剂的催化活性和稳定性得到一定程度提高,从而进一步增加了贵金属催化剂工业化应用的可能性。 相似文献
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Characterization and activity of Fe-ZSM-5 catalysts for the total oxidation of phenol in aqueous solutions 总被引:2,自引:0,他引:2
Nguyen Huu Phu Tran Thi Kim Hoa Nguyen Van Tan Hoang Vinh Thang Pham Le Ha 《Applied catalysis. B, Environmental》2001,34(4):267-275
Fe-ZSM-5 zeolites with of Si/Fe ratios varying from 40 to 200 were synthesized and characterized by IR, XRD, SEM, ESR and ion-exchange techniques. From the obtained results, it is possible to conclude that, these zeolites have a good crystallinity and that the incorporation of Fe3+ ions into the MFI-structure depends on the Si/Fe ratios in the gel: the higher the Si/Fe ratio, the more the percentage of Fe3+ions is incorporated into the MFI lattice.
Catalytic properties of Fe-ZSM-5 were studied in the oxidation of phenol. The reaction was performed in a static system, at the atmospheric pressure, 343 K, and with H2O2 concentration, which exceeds stoichiometric concentration for complete oxidation of phenol to carbon dioxide and water. From the catalytic results, it can be concluded that framework Fe can catalyze more completely phenol oxidation than the extra-framework Fe does. 相似文献
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We have reported previously the excellent performance of Fe-exchanged ZSM-5 for selective catalytic oxidation (SCO) of ammonia to nitrogen at high temperatures (e.g., 400-500 °C). The present work indicates that the reaction temperature can be decreased to 250-350 °C when a small amount of noble metal (Pt, Rh or Pd) is added (by both doping and ion exchange) to the Fe-ZSM-5. The SCO activity follows the order: Pt/Fe-ZSM-5 > Rh/Fe-ZSM-5 > Pd/Fe-ZSM-5. The noble metal promoted Fe-ZSM-5 catalysts also show higher activity for NH3 oxidation than Ce-exchanged Fe-ZSM-5 at low temperatures. On the Pt promoted Fe-ZSM-5, near 100% of NH3 conversion is obtained at 250 °C at a high space velocity (GHSV = 2.3 × 105 h-1) and nitrogen is the main product. The presence of H2O and SO2 decreases the SCO performance only slightly. This catalyst is a good candidate for solving the ammonia slip problem that plagues the selective catalytic reduction (SCR) of NO with ammonia in power plants. 相似文献
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The electrochemical reduction of NO in alkaline solutions was investigated at gas diffusion electrodes with various metal (Ru, Rh, lr, Pd and Pt) catalysts at various NO flow rates. Reduction currents are observed at potentials more negative than 0.95 V, which increase with the decrease in potential and also with increasing gas flow rate. The faradaic efficiencies of N2O formation decrease with decreasing NO flow rate and with decrease in potential. The faradaic efficiencies of N2 formation increase with decreasing flow rate and with decrease in potential. The reduction of NO to N2 at a flow rate of 5mlmin–1 occurs selectively at potentials more negative than 0.1V; the faradaic efficiency of N2 formation is approximately 95 at Pd catalysts.Electricity production and NO decomposition can be carried out simultaneously using an H2NO fuel cell reactor. The faradaic efficiency of N2 formation at a flow rate of 5mlmin–1 is approximately 80 at a cell voltage of 0.25 V. 相似文献
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一氧化碳(CO)广泛存在于烧结/球团/焦化烟气或汽车尾气中,应用CO-选择性催化还原(SCR)技术同时脱除烟气中CO和NO是烟气治理的理想方案之一。目前,在NO-CO反应研究中较多的是贵金属催化剂,但由于其价格昂贵、高温失活、易中毒等问题难以在工业中实现应用。本文将近几年来金属氧化物催化CO还原NO的研究成果进行了系统的梳理与总结,重点介绍Fe基、Ce基、Co基、Cu基这4种金属氧化物催化剂的研究进展,分析催化剂的制备方法、掺杂助剂种类和比例、NO-CO反应条件等因素与催化活性之间的关系,总结催化剂抗水抗硫性能及可能的CO-SCR反应机理,并探讨O2存在的条件下对催化剂活性的影响,为提高金属氧化物催化剂抗氧性研究提供理论参考。 相似文献
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研究了碱金属化合物(K2SO4)对活性炭(AC)担载五氧化二钒(V2O5)组成的V2O5/AC催化剂的低温脱硝活性的影响。发现在V2O5/AC催化剂表面负载碱金属化合物(K2SO4)后其脱硝活性大大降低。用等体积浸渍法制备了V2O5/AC催化剂和Kx-V2/AC(x=0.5,1,2)催化剂。采用5种模型对动力学实验数据进行关联。结果显示,无论V2O5/AC催化剂是否负载K2SO4,Eley-Rideal模型均比其他模型可更好地描述SCR脱硝反应,碱金属化合物(K2SO4)的存在提高了反应活化能,但并不改变反应机理。 相似文献
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为实现N_2O一步氧化苯制备苯酚的工业化生产,基于自制的Fe-ZSM-5分子筛(粒度?1.5 mm×1 mm),在等温固定床积分反应器中,以单因素实验和正交实验[L_9(3~4)]相结合的方式,系统考察了温度(375~475℃)、空速(2 500~10 500 h~(-1))和苯与N_2O的物质的量比(6:1~14:1)等操作条件对N_2O一步氧化苯制苯酚反应过程规律及产物分布的影响。结果表明,实验所用Fe-ZSM-5分子筛对N_2O一步氧化苯制苯酚具有良好的催化活性和选择性;该反应过程存在催化剂起始活性高但失活速率快的特点,适宜操作条件域的选取对催化剂性能的发挥至关重要;基于正交实验分析最终确定的相对适宜工艺条件操作域为:温度425~450℃、空速4 500~5 500 h~(-1)和苯与N_2O的物质的量比8:1~10:1,在此条件下苯酚收率可达60%以上。 相似文献