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1.
Catalytic oxidation of diesel soot particulate on Ce(x)Zr(1-x)O(2) catalysts was investigated. Results indicated that Ce/Zr ratios had a significant influence on the catalytic activities. Compared with the ignition temperature (T(i)) of uncatalyzed soot combustion, T(i) of Ce(0.5)Zr(0.5)O(2) with the best catalytic behavior decreased by 80 degrees C. The reactant gas compositions (O(2), H(2)O and NO) affected the catalytic activities too. O(2)-TPD, TG-DTA and XPS characterization results showed that Ce(x)Zr(1-x)O(2) released lattice oxygen continuously to promote the soot combustion even no gas oxygen occurred in the reaction atmosphere. The mechanisms of spill-over and reduction/oxidation functioned synergistically for soot catalytic combustion.  相似文献   

2.
A series of CeO(2)-ZrO(2) mixed oxides were prepared using coprecipitation method and characterized by BET, oxygen storage capacity (OSC), X-ray diffraction (XRD) and H(2)-temperature-programmed reduction (H(2)-TPR). The catalytic activities toward toluene combustion were investigated in a micro-reactor. The results demonstrate that the catalytic activity of Pt/gamma-Al(2)O(3)/Ce(0.50)Zr(0.50)O(2) monolithic catalyst can be greatly improved by doping metal into Ce(0.50)Zr(0.50)O(2). When doping Y and Mn into Ce(0.50)Zr(0.50)O(2) simultaneously, the catalyst Pt/gamma-Al(2)O(3)/Ce(0.40)Zr(0.40)Y(0.10)Mn(0.10)O(X) shows the highest activity. The T(10) (the temperature of 10% toluene conversion) and the complete conversion temperature (the temperature of 90% toluene conversion) of toluene are 443 and 489K, respectively. Gas hourly space velocity (GHSV) results show that the prepared catalyst can be applied in a wide range of GHSV (from 12,000 to 20,000h(-1)). The catalyst prepared shows great potential for practical application.  相似文献   

3.
The paper demonstrates that the photocatalytic activity of TiO2 towards the decomposition of gaseous benzene in a batch reactor can be greatly improved by loading TiO2 on the surface of CeO(2)-ZrO(2). The research investigates the effects of three metals doping into Ce(0.5)Zr(0.5)O(2) on photocatalytic activity of TiO2/Ce(0.45)Zr(0.45)M(0.1)O(X) (M=Y, La, Mn). The prepared photocatalysts were characterized by BET, XRD, UV-vis diffuse reflectance and XPS analyses. BET surface area of TiO2/Ce(0.45)Zr(0.45)M(0.1)O(X) (M=Y, La, Mn) is smaller than that of Ce(0.5)Zr(0.5)O(2). XRD results reveal that the deposited titania is highly dispersed as in the CeO(2)-ZrO(2) matrix, doping M in the CeO(2)-ZrO(2) lattice causes the changing of lattice space and the diffraction peaks shift to higher 2theta position. Among these four catalysts, the band gap value of TiO(2)/Ce(0.45)Zr(0.45)La(0.1)O(X) is the lowest. The binding energy value of Ti 2p(3/2) of four catalysts transfers to a lower value. The order of photocatalytic activity is TiO2/Ce(0.45)Zr(0.45)La(0.1)O(X)>TiO2/Ce(0.45)Zr(0.45)Y(0.1)O(X)>TiO2/Ce(0.45)Zr(0.45)Mn(0.1)O(X)>TiO2/Ce(0.5)Zr(0.5)O(2)>TiO2. The proposed mechanism is of electron transfer and the stronger absorption in the region 210-400 nm.  相似文献   

4.
铈锆氧化物固溶体的制备、表征及三效催化性能   总被引:7,自引:0,他引:7  
采用共沉淀技术制备了Ce0.6Zr0.4O2固溶体,并对其进行了XRD、Raman光谱和SEM表征.将其用于单钯三效催化剂的制备,考察了Ce06Zr0.4O2对三效催化剂性能的影响.结果表明:Ce0.6Zr0.4O2具有和CeO2相似的立方结构,并具有较高的热稳定性;与含CeO2的三效催化剂相比,含Ce06Zr0.4O2的三效催化剂经高温老化后,仍具有较高的HC、CO、NO转化率和较低的起燃温度.  相似文献   

5.
In this paper, the effects of Zr, Sc and Ce additions on the as-cast microstructure and mechanical properties of Mg-3Sn-1Mn (wt.%) magnesium alloy were preliminarily investigated and compared. The results indicate that adding 0.36 wt.% Sc and 0.87 wt.% Ce to the Mg-3Sn-1Mn alloy, respectively leads to the formation of the extra phases of Mg-Sn-Sc and Mg12Ce while adding 0.43 wt.% Zr does not cause the formation of any new phases. At the same time, adding 0.43 wt.% Zr or 0.87 wt.% Ce can refine the grains while adding 0.36 wt.% Sc coarsens the grains. Among the Zr- and Ce-containing alloys, the grains of the latter are relatively finer than those of the former. In addition, adding 0.43 wt.% Zr, 0.36 wt.% Sc and 0.87 wt.% Ce to the Mg-3Sn-1Mn alloy can improve the tensile and/or creep properties of the alloy. However, the addition of 0.43 wt.% Zr is not beneficial to the creep properties. Among the Zr-, Sc- and Ce-containing alloys, the alloy with the addition of 0.87 wt.% Ce exhibits the optimal tensile and creep properties.  相似文献   

6.
Ce(0.67)Zr(0.33)O(2) doped with iron oxide was prepared and the corresponding Pd-only three-way catalysts were examined and characterized. Pd/CZFe(1%) catalyst exhibits the best catalytic performance for CO, HC, NO and NO(2) elimination and the widest operation window. The doping of iron oxide with 1% loading suggests the formation of more homogeneous Ce-Zr-Fe-O ternary solid solution, which seems to facilitate the reduction of Ce(4+)→Ce(3+) or the formation of oxygen vacancy and to promote the interaction between Ce-Zr and Fe. Moreover, the Ce redox behaviour for surface reduction suggests depending not only on the formation of homogeneous Ce-Zr-Fe-O but also on the surface property of the sample. The increase in the concentration of oxygen vacancies under all atmospheres for CZFe(1%) sample also results in the enhancement of oxygen storage complete capacity.  相似文献   

7.
A series of Mn(x)-CeLa mixed oxide catalysts with different compositions prepared by sol-gel method were tested for the catalytic combustion of chlorobenzene (CB), as a model of chlorinated aromatics. Mn(x)-CeLa catalysts with the ratios of Mn/(Mn + Ce + La) in the range from 0.69 to 0.8 were found to possess high catalytic activity in the catalytic combustion of CB. The stability and deactivation of Mn(x)-CeLa catalysts were studied by other assistant experiments. Mn(x)-CeLa catalysts can deactivate below 330 °C, due to the strong adsorption of Cl species produced during the decomposition of CB. Nevertheless, the increase in oxygen concentration can enhance the resistance to Cl poisoning through the reaction of surface oxygen species with residual chlorine. At 350 °C, high activity, good selectivity and desired stability were observed over Mn(x)-CeLa catalysts.  相似文献   

8.
氨选择性催化还原(NH3-SCR)技术需要进一步研发在相对较低温度(<300℃)下具有良好催化活性、高稳定性及环境友好的脱硝催化材料。本工作采用草酸共沉淀法制备Mn-Fe-O催化材料,并对其进行不同含量CeO2修饰,用于低温NH3-SCR脱硝催化反应。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附-脱附、X射线光电子能谱(XPS)、程序升温还原或脱附(H2-TPR、NH3-TPD)等手段对催化剂进行了表征。催化结果表明,在相同反应条件下适量CeO2修饰后的Mn-Fe-O样品比纯Mn-Fe-O表现出更优异的NH3-SCR脱硝催化性能,在80℃时NO转化率在95%以上,且具有较高的N2选择性。CeO2修饰提高了Mn-Fe-O氧化物表面的Fe^3+、Mn^3+和Mn4+含量及表面酸性位点数量,从而有助于NH3的吸附及催化反应的进行,并且Fe^2+/Fe^3+、Mn^2+/Mn^3+/Mn^4+以及Ce^3+/Ce^4+电子对之间的相互氧化还原反应提高了催化剂的氧化还原能力及稳定性。  相似文献   

9.
胡玉才 《功能材料》2005,36(9):1464-1466,1471
以硝酸铈和硝酸锆为原料用溶剂热的方法在甲酸中120℃加热24h制得了纳米Ce0.8Zr0.2O2固溶体材料,利用X射线衍射(XRD)、Raman光谱、扫描电镜(SEM)和投射电镜(TEM)对其进行了表征。在乙酸和正丁醇制备乙酸丁酯的反应中考察了其催化活性。XRD和Raman光谱显示出所制备的样品形成了具有氧化铈立方结构的均一固溶体。TEM结果表明所合成的Ce0.8Zr0.2O2的粒径〈100nm。在酯化反应中,Ce0.8Zr0.2O2固溶体具有较高的催化活性,且容易和反应液分离。反复实用10次后,其催化活性基本上保持不变。  相似文献   

10.
Liu L  Liang H  Yang H  Wei J  Yang Y 《Nanotechnology》2011,22(1):015603
Uniform Mn(2)O(3) octahedral nanoparticles were synthesized by a mediated N, N-dimethylformamide (DMF) solvothermal route. On the basis of a time-dependent experiment, we propose that the Mn(2)O(3) octahedra were formed through oriented aggregation of primary nanocrystals. Meanwhile, poly(vinyl-pyrrolidone) (PVP) was applied as a surfactant to facilitate the oriented aggregation of small Mn(2)O(3) nanoparticles into octahedral crystallites. By tuning the amount of Mn(NO(3))(2), particles with average sizes 1 μm to 300 nm, with a narrow size distribution, could be fabricated. The catalytic test results show that the as-obtained Mn(2)O(3) octahedra exhibited desirable CO catalytic oxidation properties and the surface texture and particle size significantly affected the catalytic activity. By contrast, the larger Mn(2)O(3) octahedral nanoparticles prepared at a lower concentration of Mn(NO(3))(2) exhibited relatively high activities.  相似文献   

11.
Ce(0.8)Sm(0.2)O(2-delta) and Ce(1-x)Gd(x)O(2-delta) (0.1 < or = x < or = 0.3) nano-sized powders were successfully synthesized by the solution combustion synthesis process. The calcined nanopowders showed a ceria-based single phase with a cubic fluorite structure. In this study, we discussed the structural and electrical characteristics of the sintered Ce(0.8)Sm(0.2)O(2-delta) and Ce(1-x)Gd(x)O(2-delta). We obtained high-quality Ce(0.8)Sm(0.2)O(2-delta) and Ce(1-x)Gd(x)O(2-delta) ceramics with a high density, ultra-fine grain size, and high electrical conductivity even at low sintering temperature using the nanosized powders. The electrical conductivities at 800 degrees C for the Ce(0.8)Sm(0.2)O(2-delta) sintered at 1400 degrees C and the Ce(0.8)Gd(0.2)O(2-delta) sintered at 1350 degrees C were 0.110 and 0.104 Scm(-1), respectively.  相似文献   

12.
采用共沉淀法制备了低铈型Ce-Zr-Sn复合氧化物纳米储氧材料,采用X射线衍射、储氧量、比表面积等研究手段对其进行了分析和表征,结果表明,低铈型Ce(0.35)Zr(0.55-x)SnxLa(0.1)O(1.95)(x=0-0.12)复合氧化物纳米储氧材料具有高的比表面积和储氧量,且物相单一,只含有稳定的立方结构的固溶体晶相。少量Sn的掺入有利于低铈型铈锆固溶体储氧材料热稳定性能和低温储氧性能的提高。当Sn含量(摩尔分数)为0.06时,样品的低温储氧量和比表面积最高,抗老化性能最佳,经1000℃高温老化5h后,储氧量和比表面积仍可达298.1μmo1/g和48.95m~2/g。  相似文献   

13.
Transition metal oxide compounds with perovskite‐type structure (AMX3‐δ) show besides attractive physical properties, such as high temperature superconduction or thermoelectricity, often excellent catalytic properties for various redox reactions. The catalytic reactivity is strongly dependent on composition, structure and of course the specific surface area of the compounds. Fine‐tuning of the properties can therefore be achieved by suitable cation‐ and anion‐ substitutions and by adjusting the morphology of the compounds. For systematic studies on the relationship between composition, structure and properties in these systems fine particles as well as thin films of identical compositions e.g. La1‐xCaxMO3‐δ (x = 0, 0.3, 0.4 , 0.5) (M = Fe, Co, Ni, Mn, Ti) are produced with diverse “chimie douce” methods. The samples are characterised concerning their chemical and physical properties. Carbon nanotube composite materials have been produced by catalytic decomposition of gaseous carbon compounds on nanometer‐size transition metal clusters on top of perovskite‐type metal oxides and tested for a possible application as oxygen electrodes in air based batteries.  相似文献   

14.
A series of Ca(4)Y(6)(SiO(4))(6)O (CYS): Ce(3+)/Mn(2+)/Tb(3+) oxyapatite phosphors were prepared via high-temperature solid-state reaction. Under UV excitation, there exist dual energy transfers (ET), i.e., Ce(3+)→Mn(2+) and Ce(3+)→Tb(3+) in the CYS: Ce(3+), Mn(2+), Tb(3+) system and their emitting colors can be adjusted from blue to orange-red via ET of Ce(3+)→Mn(2+) and from blue to green via ET of Ce(3+)→Tb(3+), respectively. Moreover, a wide-range-tunable white light emission with high quantum yields (13%-30%) were obtained by precisely controlling the contents of Ce(3+), Mn(2+) and Tb(3+) ions. On the other hand, the CL properties of CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have been investigated in detail. The studied results indicate that the as-prepared CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have good CL intensity and CIE color coordinate stability with a color-tunable emission crossing the whole white light region under low-voltage electron beam excitation. In general, the white light with varied hues has been obtained in Ce(3+), Mn(2+), and Tb(3+)-triactivated CYS phosphors by utilizing the principle of energy transfer and properly designed activator contents under UV (284, 358 nm) and low-voltage (1-5 kV) electron beam excitation, which make them as a potential single-composition trichromatic white-emitting phosphor.  相似文献   

15.
A series of CuO/Ce(1-x)Ti(x)O(2) catalysts used for low-temperature CO oxidation were prepared by impregnation with the support derived from surfactant-assisted co-precipitation. The techniques of N(2) adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by H(2) (H(2)-TPR) were employed for catalyst characterization. It is found that the support CeO(2) prepared by the surfactant-assisted method possesses much larger specific surface area than the one obtained from conventional precipitation. Doping Ti in the support with Ti/Ce atomic ratio of 1:9 or 3:7 can further increase the surface area of CeO(2) and decrease its crystallite size. As a result, the active Cu species possess higher dispersion on the support Ce(1-x)Ti(x)O(2) than on pure CeO(2). The strong interaction between the dispersed Cu species and the support Ce(1-x)Ti(x)O(2) makes the catalysts possess much higher oxidation activity and thermal stability. However, when the ratio of Ti/Ce reaches 5:5, opposite effect is found, due to the highest surface concentration of Ti and the lack of surface highly dispersed copper species.  相似文献   

16.
以Ce(NO3)3.6H2O和ZrOCl2.8H2O为原料,以尿素为沉淀剂,利用微波均相法制备Ce0.75Zr0.25O2粉体,采用热分析仪、X射线衍射仪、扫描电子显微镜表征制备的粉体,对制备的粉体压制成型并烧结,用扫描电子显微镜观察烧结体的微观结构。结果表明,合成Ce0.75Zr0.25O2前驱体时加入2倍于Ce3+物质的量的H2O2可以减小固溶体颗粒粒度,降低固溶温度30℃;所制备的固溶体粉体具有良好的烧结性,在1 550℃得到烧结体的相对密度达99.57%。  相似文献   

17.
Nanoplates of Mn3O4 were prepared by redox reactions of Mn(CH3COO)2 x 4H2O taking place in short chain n-alkylamine aqueous solutions such as n-butylamine, n-propylamine and n-hexylamine at room temperature. Phase purity was confirmed by powder X-ray diffraction. The high resolution transmission electron microscopy revealed the rectangle shape of Mn3O4 nanoplates with the average edge length of 22 nm and width of 19 nm. The prepared Mn3O4 nanoplates exhibited a coercive field of 5034 Oe at 10 K. The possible formation mechanism was also discussed.  相似文献   

18.
以Al2O3-TiO2-SiO2(ATS)为载体、Ti0.8Zr0.2Ce0.2O2.4(TZC)为催化活性组分, 采用挤出成型法制备系列整体式TZC/ATS及W掺入催化剂样品。研究了W掺入对催化剂TZC/ATS 的氨气选择性催化还原(NH3-SCR)脱除NO活性及抗K2O、CaO等毒性的影响, 比较了Ti0.8Zr0.2Ce0.2W0.08O2.64/ATS(TZCW0.4/ATS)催化剂与V2O5(WO3)/TiO2催化剂的抗K2O、CaO等中毒性能, 并采用N2-BET、XRD、SEM和NH3-TPD等技术手段分别表征了催化剂的比表面积、固相结构、微观形貌及表面酸性。结果表明, 当活性组分中Ti/Zr/Ce/W元素摩尔比为4:1:1:0.4时, TZCW0.4/ATS催化剂NH3-SCR脱除NO的效率最高、稳定性最好。W掺入显著增强了催化剂的抗K2O及CaO毒性能力, 且TZCW0.4/ATS催化剂抗K2O及CaO的中毒能力明显强于V2O5(WO3)/TiO2催化剂。分析表明, W掺入提高了TZCW0.4/ATS催化剂的比表面积, 增加了催化剂的表面酸量, 从而优化了催化剂的脱硝性能。  相似文献   

19.
郑建东  任晓光 《材料导报》2011,25(8):77-80,84
采用反相微乳液-共沉淀法制备了一系列以La、Sr作为镜面阳离子、锰离子作为活性组分的六铝酸盐催化剂La1-xSrxMnAl11O19-δ(x=0.2、0.4、0.5、0.6、0.8)。利用X射线衍射、比表面积分析等分析方法及甲烷燃烧对催化剂的结构和性质进行了考察,主要考察了不同含量的La和Sr离子的掺杂量对催化剂结构及对甲烷催化燃烧活性的影响。结果表明,La和Sr同时作为镜面阳离子,不但可以形成完整的六铝酸盐,而且所制备的催化剂具有较高的催化活性。不同含量的La和Sr离子掺杂对于催化剂的特性有较大影响。当x=0.5时,所制备的催化剂La0.5-Sr0.5MnAl11O19-δ具有较高的催化活性,起燃温度T10%=502℃,至683℃甲烷完全转化。催化剂在低转化率下的宏观动力学实验结果表明,甲烷催化燃烧在La1-xSrxMnAl11O19-δ催化剂上为一级动力学反应,反应速率受催化剂固有性质控制。  相似文献   

20.
The layered LiNi1/3CO1/3Mn1/3-xMg(x)O2 (x = 0, 0.01, 0.03, 0.05) cathode materials were prepared by solid state reaction, then copper oxide was coated on the product. The structures, morphologies and electrochemical properties of the LiNi1/3Co1/3Mn1/3-xMg(x)O2 and CuO-coated LiNi1/3Co1/3Mn1/3-xMg(x)O2 were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electrochemical tests. The results showed that the electrochemistry properties and cycle performance of magnesium doped LiNi1/3Co1/3Mn1/3O2 and CuO-coated LiNi1/3Co1/3Mn1/3-xMg(x)O2 materials were improved. The optimal doping content of Mg was x = 0.03 in the LiNi1/3Co1/3Mn1/3-xMg(x)O2 samples to achieve high discharge capacity and good cyclic stability, and the first discharge special capacity was 158.5 mAh/g at 0.2 C in the voltage of 2.5-4.3 V, then CuO-coated LiNi1/3Co1/3Mn1/3-0.03Mg0.03O2 was investigated. The electrode reaction reversibility and electronic conductivity were enhanced through Mg-doped and CuO-coated.  相似文献   

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