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1.
CeO2-ZrO2-MnOx mixed oxide series were prepared by sol-gel method. CO pulse and CO-O2 cycle measurements were carried out to examine the oxygen storage complete capacity (OSCC) and dynamic oxygen storage capacity (OSC) of the samples. The doping method brought about strong interactions between manganese oxide and ceria, both in the bulk and on the surface. Only a small part of Mn cations are incorporated into the ceria lattice to form solid solutions and the remaining are left on the surface as finely dispersed Mn3O4. The OSC behaviors of the materials are influenced by the doping amount of Mn and the solubility of Mn in the CeO2 lattice. The OSC is more easily affected by available contents of oxygen storage components when the measurement frequency is low. Comparatively, the concentration of lattice defects, which affects the mobility of bulk oxygen, is the determining factor under high frequency. 相似文献
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Diesel oxide catalysts and soot combustion catalysts were reported in this paper.The former was manufactured in mass last year, and enhanced performance is under development now.The later is screened out and further research is under way.The best soot combustion catalyst could ignite soot combustion even at 350 ℃, which is within the range of temperatures reached in diesel exhaust, and shows the catalytic combustion velocity nearly one time faster compared with non-catalytic combustion of soot, which is of benefit to rapid regeneration of diesel particulate filter, thus it might be an excellent practicable catalyst. 相似文献
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The catalysts of CeO2 and the mixture of CeO2 and CuO were prepared, and the activities of these catalysts for completely oxidizing benzene were studied.The results show that the optimal proportion of CeO2/CuO is 6: 4.The highest temperature at which benzene was completely oxidized on these catalysts at different airspeed was measured.Compared these catalysts with the noble metal used, our catalysts had superiority in the resources and the industrial cost besides good activities. 相似文献
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Ceriumoxideisusedwidelyinthree waycatalystduetoitsoxygenstoragecapabilitywhichenablesthecatalysttooperatemoreefficientlybymakingitlesssensitivetothevariationofoxygenconcentrationinex haustgasstream[1~ 3] .TheoxygenstoragecapabilityofceriastemsfromthevalencechangebetweenCe3+andCe4 +[1,2 ] .Thereareafewotherelementswithvariableoxidationstatewithinthewholeseriesofrareearth .Praseodymiumisoneoftheelementswhichcanformaspectrumofoxygen deficientornonstoi chiometricPrOx.Ontheotherhand ,theproperti… 相似文献
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Structure and Catalytic Behavior of CuO-ZrO-CeO2 Mixed Oxides 总被引:1,自引:0,他引:1
The effect of doping CuO on the structure and properties of zirconia-ceria mixed oxide was studied. The results show that addition of CuO decreases the reduction temperature of ceria, and stabilizes the cubic structure of mixed oxides, and enhances catalytic activity of CuO-ZrO-CeO2 mixed oxides for CO oxidation. Increasing ceria content in the mixed oxides can enhance the catalytic activity, but some impurities such as sulfate make catalytic activity falling. There is little effect of calcination temperature on catalytic activities, implying that these catalysts are effective with good thermal stability. 相似文献
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氯化铵法氯化混合氧化稀土及其动力学的研究 总被引:3,自引:0,他引:3
研究了氯化铵氯化混合氧化稀土的适宜条件及氯化反应动力学。结果表明 :氯化铵氯化混合氧化稀土的适宜条件为氯化剂用量为物质的量比n氯化铵∶n氧化稀土 =1 2∶1 ,氯化焙烧温度 380~ 42 0℃ ,氯化时间 30min ,稀土的氯化率在 99%以上 ;混合氧化稀土氯化反应的表观活化能Ea 为 75 .82kJ·mol- 1 ,过程限制环节是界面化学反应控制。CeO2 与NH4 Cl的反应和反应程度分别是混合氧化稀土氯化的控速步骤和决定混合氧化稀土氯化率的关键。混合氧化稀土的组成和配分是影响氯化铵氯化氧化稀土氯化率和氯化反应速率的重要因素。 相似文献
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Temperature programmed reduction (TPR) study was carried out for CeO2/A12O3 and CeO2/ZrO2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO2/ZrO2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO2/Al2O3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO3. Consequently, the oxygen storage on the CeO2/ZrO2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures. 相似文献
9.
Wang Jianli Cao Hongyan Zhong Junbo Gong Maochu Yan Shenghui Liu Zhimin Shen Mei Chen Yaoqiang 《中国稀土学报(英文版)》2007,25(1)
This article showed that the catalytic activity of MnOx/γ-Al2O3/Ce0.5Zr0.5O2 monolithic catalyst toward the catalytic combustion of ethanol in a fixed bed reactor could be greatly improved by doping three metal oxides into Ce0.5Zr0.5O2. The catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45M0.1Ox (M=Y, La, Mn) is better than that of MnOx/γ-Al2O3/Ce0.5Zr0.5O2. The order of activity of the catalysts is as follows: MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1Ox>MnOx/γ-Al2O3/Ce0.45Zr0.45La0.1Ox>MnOx/γ-Al2O3/Ce0.45Zr0.45Mn0.1Ox>MnOx/γ-Al2O3/Ce0.5Zr0.5O2. The influence of the loading amount of manganese oxide in enhancing the catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1Ox was investigated. The results showed that when MnO2 loading amount was 10%(mass fraction), the MnOx/Al2O3/Ce0.45Zr0.45Y0.1Ox catalyst recorded the highest activity. 相似文献
10.
Inthelastdecadethethree waycatalystshave beenremarkablyimproved.Oxygenstoragecapacity(OSC)ofthecatalystwasdeterminedbyTPR.The measuredvalueisactuallyapartoftheoxygentransfer capacity(OTC)offluorite typeoxidescontainingCe,and orPr,and orTb[1,2].Theseoxides,Ce1-x-y PrxTbyO2-δ(0≤x≤1,0≤y≤1,0≤δ≤0.5)can releasetheirlatticeoxygenwhenthetemperatureisin creasedunderdifferentoxygenpartialpressureinclud inghydrogenflow,buttheywillabsorboxygenfromits vicinityenvironmentwhenthetemperatureisde… 相似文献
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The metallic substrate-catalysts with different subsistence states of CeO2-ZrO2 mixed oxides were prepared and the catalytic properties were investigated. The studies on CeO2-ZrO2-V2O5-CuO mixed oxides which were prepared by coprecipitation, show that the doping of V5 and Cu2 in CeO2-ZrO2 mixed oxides can enhance the catalytic activity and thermal stability of coating materials. Moreover, different additives were doped in slurries of γ-Al2O3 to investigate the influence of additives on oxidation activity of catalysts. The mixture of ceria-zirconia, alkali metals and other rare earths acting as additives exhibits promotion effect on oxidation activity by optimizing the distribution of oxygen on the surface and in the bulk of ceria species. This mentioned mixture was mixed with γ-Al2O3 and a newly proposed active component to prepare a new catalyst. Afterward, the influence of thermal treatment on the new catalyst were investigated by calcinations at 500, 650, 750, 800, 850 and 900 ℃ for 2 h. The light-off curves of CO and HC show that after being treated at 650~750 ℃, catalysts present the best activity. XRD patterns show that ceria and zirconia species in the newly proposed active component form a phase of extra CeO2-ZrO2 mixed oxides on the surface of catalysts after the thermal treatment at 750 ℃, which has practical value for improving the preparation process and promoting the catalytic properties. Moreover, XPS results imply the existence of Ce1-xPdxO2-σ and Ce1-xPtxO2-σ on the surface of these treated samples, which may show influence on the catalytic activities. 相似文献
13.
ThereisprofuseresourceofrareearthelementinChina,soitisveryimportanttostudytheapplicationoftherareearthcompounds[1].Theperovs... 相似文献
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A new catalyst system was used in the synthesis of polyethylene terephthalate(PET) and its copolymers, which involved a Ln3 containing compound. The catalytic effects were studied, and it was found that the direct esterification reaction of terephthalate acid(TPA) with ethylene glycol (EG) can be accelerated by the addition of Ln3 ~ containing compound, which acts as a promoter of the catalyst Sb203 in polycondensation of bis hydroxyethyl terephthalate(BHET). 相似文献
15.
Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines
A series of low noble-metal coment monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 (where OSM was oxygen storage material) catalyst with Ce0.5Zr0.5-MnOx(3%MnOx) OSM held low light-off temperature for CO, HC, and NO; quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently comrol exhaust emission of small gasoline engines. 相似文献
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Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity. 相似文献
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The oxygen adsorption/desorption properties of double perovskite structure oxides PrBaCo2O5+δ, GdBaCo2O5+δ, and YBaCo2O5+δ were investigated by the thermogravimetry (TG) method in the temperature range of 400~900 ℃. The calculated oxygen adsorption/desorption surface reaction rate constants ka and kd of these double perovskite structure oxides were larger than the commonly used cubic perovskite oxides, such as Ba0.95Ca0.05Co0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ, whereas, the oxygen permeation flux was comparable to that of the latter, which was attributed to the smaller difference of oxygen vacancy in oxygen and nitrogen atmosphere (Δδ/Vmol) in these double perovskite structure oxides. The large oxygen adsorption/desorption rate constants of GdBaCo2O5+δ and PrBaCo2O5+δ made them nice catalyst coating materials, on other membrane surfaces, to improve the oxygen permeability. 相似文献
19.
RE-doped Ni-based catalysts were prepared by sol-gel method.These catalysts were applied to the reaction of CO2 reforming CH4 to syngas.The studies reveal that RE-doped ( RE = La, Ce, Sm, Yb) Ni-based catalysts show higher catalytic activity than undoped Ni-based catalyst, and with the increasing of RE-doped quantity, the catalytic activity of catalysts exhibits regular changes.When RE-doped quantity is 0.2% ( molar ratio), the catalysts show the best catalytic activity. 相似文献
20.
Four kinds of CeO2-ZrO2 mixed oxides, i.e., a physical mixture of ceria and zirconia (CZP), zirconia-coated ceria (ZCC), ceria-coated zirconia (CCZ) and a chemical mixture of celia and zirconia (CZC), were prepared. The oxygen storage capacity (OSC) measurements at 500℃ were performed under transient and stationary reaction conditions. All the curves of CO2 evolution during CO-O2 cycles presented a bimodal shape. The fast peak was primarily the result of the reaction of CO with the oxygen from the oxides, which was mainly determined by the nature of the material The sec- ond peak was mostly related to the CO2 adsorption behavior and was highly influenced by the surface area and the number of surface active sites. As a result, OSC activity of the samples followed in the order of CZC 〉 CCZ 〉 ZCC=CZP. 相似文献