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1.
The effect of MoO3 addition to alumina supported vanadia catalysts on the catalytic activity for the selective catlaytic reduction of NO is investigated. Upon the addition of MoO3, catalytic activity is enhanced and the particle size of V2O5 which is shown by the results of XRD and Raman spectroscopy is decreased. The MoO3-V2O5/Al2O3 catalyst also exhibits more resistance to SO2 deactivation than V2O5/Al2O3 does.  相似文献   

2.
Water-soluble conducting poly(2-(3thienyloxy)ethanesulfonic acid) (PTOESA)/V2O5 nanocomposite, (PTOESA)xV2O5, was prepared by simply mixing PTOESA with V2O5 wet gel at room temperature. XRD data showed that the interlayer spacings of (PTOESA)xV2O5 films are 14.0±1.5 Å and increased as the polymer content increased. These values are consistent with the insertion of polythiophene chains into the V2O5 layer gallery. The formation of alternative layers of PTOESA and V2O5 was further supported by depth profile SIMS analyses. Cyclic voltammograms of (PTOESA)xV2O5 film showed two pairs of redox peaks with colors varying from orange, yellowish green, green, to purple blue, depending on the stoichiometry of the nanocomposites. Moreover, a synergetic effect was observed on the electrochromic properties of these nanocomposites. It was found that the optical contrast (ΔOD) of the composites is better than those of PTOESA and V2O5 at the film thickness from 150 to 500 nm. The oxidation optical response time of (PTOESA)xV2O5 is independent of the stoichiometry and falls in between those of PTOESA and V2O5. At higher polymer content (x>0.5), the reduction optical response time of (PTOESA)xV2O5 is smaller than those of PTOESA and V2O5. Variable temperature conductivity data showed that the conductivity of (PTOESA)xV2O5 films increased as temperature increased, characteristic of thermal activated behavior, which was dominated by the interparticle contact resistance. The room-temperature conductivity of water-soluble (PTOESA)xV2O5 films was in between those of PTOESA and V2O5 xerogel and higher conductivity was found in the composite with lower polymer content. The anomalous conductivity of (PTOESA)xV2O5 with high PTOESA content may be due to the reason that the higher the polymer content, the bigger the grain size of (PTOESA)xV2O5 film as revealed with scanning electron microscopy and AFM micrographs.  相似文献   

3.
5-Acylethynylpyrrole-2-carbaldehydes have been synthesized from the protected pyrrole-2-carbaldehydes by their transition-metal-free topochemical mechanoactivated ethynylation with acylbromoacetylenes in a solid Al2O3 medium (room temperature, 6 h, 41–54% yields).  相似文献   

4.
V2O5-TiO2复合半导体光催化材料结构及光响应性能研究   总被引:9,自引:0,他引:9  
采用溶胶凝胶法制备了V2O5-TiO2复合半导体材料,通过Raman、XRD及UV-Vis DRS等实验方法研究了V2O5与TiO2复合对材料表面组成、晶体结构以及光响应性能的影响。结果表明:钒加入后优先与TiO2作用形成较为稳定的金红石型TiVO4晶相,其中V4+是促进TiO2发生相变的关键;随着钒加入量的增加,V2O5由表面高分散状态逐渐聚集形成晶相,并释放部分Ti4+使之形成锐钛矿型TiO2晶相,使得体相中金红石型TiO2的含量有所下降;复合后形成的TiVO4晶相显著提高了材料对可见光的吸收率,并使其吸光域红移至460 nm左右。  相似文献   

5.
运用自动电位滴定技术分别研究了在纳米α-Fe2O3,γ-Al2O3单一体系及其混合体系中矿物表面的酸碱性质。依据表面配位理论恒电容模式,计算了相应的表面酸碱配位常数。实验和计算结果表明,按照等表面积原则混合α-Fe2O3、γ-Al2O3纳米粒子得到混合体系,其表面化学反应并非是单一体系的简单叠加,而是存在着不同矿物表面间复杂的交互作用。其表面酸碱性质和吸附重金属离子的行为可以用单表面模型拟合,混合体系表面反应平衡模式和相应的酸碱反应平衡常数分别为:≡XOH+H+≡XOH2+lgK1=4.04≡XOH≡XO-+H+lgK2=-9.20根据重金属离子Cu2+、Pb2+、Zn2+在α-Fe2O3/γ-Al2O3混合体系表面的吸附行为,计算得出Cu2+、Pb2+、Zn2+在混合体系固体表面的配位反应平衡常数如下:≡XOH+M2+≡XOM++H+lgK=-2.50、-2.25、-3.75(M=Cu、Pb、Zn)  相似文献   

6.
Mesoporous vanadium oxide (V2O5) thin films were deposited electrochemically onto indium tin oxide-coated glass substrates from an aqueous solution of vanadyl sulfate using CTAB (hexadecyltrimethylammonium bromide) as a templating agent. For comparison, a control sample was electrodeposited without CTAB templating. Transmission electron microscopy and small angle X-ray diffraction indicated the presence of mesoporosity with a well-ordered lamellar phase in the electrodeposited films. The crystallinity of the V2O5 thin films was confirmed by X-ray diffraction. Cyclicvoltammetry and chronoamperometry were used to measure electrochemical properties of synthesized films. The mesoporous films prepared with CTAB templating had a much higher capacity and lithium-ion diffusion rate than the non-porous electrode prepared without CTAB templating.  相似文献   

7.
以聚乙烯吡咯烷酮(PVP)和偏钒酸铵(NH4VO3)为原料,利用静电纺丝技术结合溶胶过程制备PVP/NH4VO3纤维,对纤维缓慢控温处理制备V2O5微纳米棒。采用热重-差热分析(TG-DTA)、X射线衍射光谱(XRD)、傅立叶红外光谱(FT-IR)、场发射扫描电子显微镜(FE-SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis)技术手段对V2O5微纳米棒的结构和表面形态进行表征。以亚甲基蓝(MB)的光降解为模型反应,研究V2O5微纳米棒的光催化性能。结果表明:热处理温度对催化剂表面形态和晶相的生长有明显影响,550℃煅烧的V2O5微纳米棒在可见光区对MB的光降解效率最高,并分析和探讨了可能的光催化机理。  相似文献   

8.
Summary. The textural characteristics, including surface area, mean pore diameters, and total pore volume of Cr2O3–CuO/Al2O3 solid catalysts were determined from the low temperature adsorption of N2 at 77 K. The structural properties were investigated using XRD. The surface acidity of calcined samples was determined using two comparable methods, including the non-aqueous titration of acidic groups with n-butylamine and dehydration/dehydrogenation activity of cyclohexanol. XRD patterns assigned a crystalline CuO and γ-Al2O3 for 723 K calcinations products of lower Cr2O3 content. The gradual increase of calcinations temperature promoted the crystallinity of Cr2O3 and resulted in solid–solid interaction of CuO and Cr2O3 forming CuCr2O4. The textural parameters varied with both calcinations temperature and catalyst composition. The surface acid density (DAS) increased with the increase of chromia content up to 0.132 mole% Cr2O3, while the rise of calcinations temperature led to a decrease of surface acidity. The dehydration/dehydrogenation of cyclohexanol as well as n-butylamine titration succeeded in characterizing of surface acidity. Present address: Chemistry Department, College of Science, King Faisal University, Al-Hofuf 31982, Saudi Arabia  相似文献   

9.
采用静电纺丝技术制备了添加0~20wt%Al2O3的Ni0.5Zn0.5Fe2O4纳米纤维。通过XRD、FESEM、TEM和VSM对样品的物相结构、形貌和磁性能进行了表征。结果表明,所合成的复合纳米纤维的直径都分布在40~150 nm之间,添加到纤维中的Al2O3主要以非晶态形式分布于铁氧体晶粒边界;随着Al2O3添加量的增加,可观察到γ-Fe2O3相逐渐析出,Ni-Zn铁氧体的晶格常数单调减小,说明有一些Al2O3进入到尖晶石晶格中取代了B位的Fe3+离子,Ni-Zn铁氧体的平均晶粒尺寸先增大后减小,在Al2O3添加量为8wt%时达到最大值39.2 nm;比饱和磁化强度和矫顽力随Al2O3添加量的增加呈现出相同的变化规律,先减小后增大,当Al2O3添加量超过5wt%时又开始变小。  相似文献   

10.
Zn/V2O5水相二次电池的交流阻抗研究   总被引:1,自引:1,他引:0  
The dependence of charge transfer resistances of electrodes in the aqueous Zn/V 2O 5 secondary battery on the Zn 2+ amount intercalated was studied by means of AC impedance experiments. The results showed that the electrode reaction on cathode was controlled by the diffusion of Zn 2+ at the beginning of the discharge process. With the increase of Zn 2+ amount intercalated into the cathode, the reaction became a kinetic controlled process, i.e.a process controlled by intercalation of Zn 2+ in V 2O 5.  相似文献   

11.
以自制不对称双子季铵盐表面活性剂为模板, 在水热合成体系中控制合成系列硅铝比纳米薄层ZSM-5分子筛.采用X射线衍射(XRD)、N2吸附-脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)和27Al魔角旋转核磁共振(27Al MAS-NMR)对合成的样品进行了表征. 详细研究了晶化温度、晶化时间、结构导向剂(SDA)用量、碱度等对合成的影响和纳米薄层ZSM-5分子筛的形成过程. 结果表明: 分子筛硅铝比越高, 结构导向剂用量越大, 所需的晶化时间越短; 晶化温度越高, 晶化时间越短; 且不同硅铝比纳米薄层ZSM-5分子筛的形貌规整度、比表面积和介孔/微孔孔容比例随着硅铝比而变化.  相似文献   

12.
Mn/Fe mixed oxide solids doped with Al2O3 (0.32-1.27 wt.%) were prepared by impregnation of manganese nitrate with finely powdered ferric oxide, then treated with different amounts of aluminum nitrate. The obtained samples were calcined in air at 700-1000 °C for 6 h. The specific surface area (SBET) and the catalytic activity of pure and doped precalcined at 700-1000 °C have been measured by using N2 adsorption isotherms and CO oxidation by O2. The structure and the phase changes were characterized by DTA and XRD techniques. The obtained results revealed that Mn2O3 interacted readily with Fe2O3 to produce well-crystallized manganese ferrite (MnFe2O4) at temperatures of 800 °C and above. The degree of propagation of this reaction increased by Al2O3-doping and also by increasing the heating temperature. The treatment with 1.27 wt.% Al2O3 followed by heating at 1000 °C resulted in complete conversion of Mn/Fe oxides into the corresponding ferrite phase. The catalytic activity and SBET of pure and doped solids were found to decrease, by increasing both the calcination temperature and the amount of Al2O3 added, due to the enhanced formation of MnFe2O4 phase which is less reactive than the free oxides (Mn2O3 and Fe2O3). The activation energy of formation (ΔE) of MnFe2O4 was determined for pure and doped solids. The promotion effect of aluminum in formation of MnFe2O4 was attributed to an effective increase in the mobility of reacting cations.  相似文献   

13.
An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P2O5/Al2O3 and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields.  相似文献   

14.
以Al_2O_3为载体,Fe、Mn为活性组分,采用浸渍法制备了Mn-Fe/Al_2O_3催化剂,研究了Mn-Fe/Al_2O_3催化剂的低温脱硝性能.实验结果表明,Fe负载量为7%时,7Fe/Al_2O_3催化剂显示出较佳的低温脱硝性能;添加Mn能明显改变7Fe/Al_2O_3催化剂低温脱硝性能,其中当Mn/Fe质量比为11∶7时,11Mn7Fe/Al_2O_3催化剂获得最佳低温脱硝效率.对催化剂的表征结果表明,比表面积和孔径的大小不是决定催化剂性能高低的主要因素;Mn O2和Fe2O3在x Mn7Fe/Al_2O_3催化剂中具有较强的相互作用,影响活性组分微观晶体结构,改善活性组分分散程度,从而提高了催化剂的低温脱硝性能;Fe的添加使催化剂表面酸性位点数目增加,从而提高7Fe/Al_2O_3催化剂的低温脱硝效率.添加Mn不仅增多了11Mn7Fe/Al_2O_3催化剂表面酸性位点数目增加,而且使催化剂表面出现新的中强性酸位点,使其低温脱硝效率进一步提高;经过详细分析,结果表明表面吸附氧Oβ、Mn4+和Fe3+的含量较高是11Mn7Fe/Al_2O_3催化剂脱硝活性较高的主要原因.  相似文献   

15.
    
The rheological responses of aqueous alumina suspensions, stabilized with an organic polyvalent salt dispersant called “Aluminon,” and including a poly(vinyl) alcohol (PVA) binder, are described in this study. It is observed that the addition of PVA, without any dispersant does not significantly influence the rheology. However, in the presence of the dispersant the rheology is affected significantly. At a given concentration of the dispersant, the viscosity, the storage and loss modulii all increase with the PVA concentration. Also, for a given concentration of the PVA, the viscosity, the storage and loss modulii values increases as the concentration of the dispersant is increased. At relatively low PVA concentrations, an excess concentration of the dispersant, causes flocculation of the particles in the suspension by a reduction of the electrostatic (double layer) effect. On the contrary, at higher concentrations of the PVA the flocculation of the suspension occurs via a depletion mechanism.  相似文献   

16.
Treatment of N-aryl-N-methoxyamides with AlCl3 in EtSH (or Me2S) generates the corresponding N-aryl-N-hydroxyamides in high yields.  相似文献   

17.
水合氧化铝的热处理及纳米氧化铝的颗粒特性   总被引:2,自引:0,他引:2  
利用IR、XRD、TG-DTA和TEM等测试技术研究了醇铝的水解产物——水合氧化铝的特性及水合氧化铝的热处理过程,探讨了热处理工艺对纳米氧化铝颗粒特性的影响规律。结果表明,醇铝的水解产物水合氧化铝为富含吸附水和结构水的非晶态一水铝石,300 ℃煅烧后出现部分非晶态γ-Al2O3;煅烧温度、保温时间和冷却方式均能影响纳米氧化铝粒子的晶型、大小和形貌,其中煅烧温度影响最大,冷却方式影响次之,保温时间影响最弱;在750 ℃ / 3 h、800 ℃ / 4 h、900 ℃ / 4 h、950 ℃ / 4 h和1 000 ℃ / 4 h随炉冷却工艺条件下,分别得到粒径为3~5 nm、3~5 nm、5~10 nm、10~15 nm和50~100 nm的纤维状或球状、α相或γ相的纳米氧化铝粒子。  相似文献   

18.
本文采用共沉淀法合成了Ti∶Al2O3纳米粉体。利用热重/差热(TG/DTA)/X射线衍射(XRD)/红外光谱(FTIR)/扫描电镜(SEM)以及能谱(EDS)等分析方法对合成的Ti∶Al2O3纳米粉体进行了表征。结果分析表明:前驱体在1200℃下,保温1 h可以得到纯的α-Al2O3晶相;粉体的粒径均匀、分散性好,平均粒径在25~50 nm之间。  相似文献   

19.
The results obtained showed that the addition of small amounts of LiNO3 to the reacting mixed solids, consisting of equimolar proportion of Fe2O3 and basic MgCO3 much enhanced the thermal decomposition of magnesium carbonate. The addition of 12 mol% LiNO3 (6 mol% Li2O) decreased the decomposition temperature of MgCO3 from 525.5 to362°C. MgO underwent solid–solid interaction with Fe2O3 at temperatures starting from800°C yielding MgFe2O4. The amount of ferrite produced increased by increasing the precalcination temperature of the mixed solids. However, the completion of this reaction required prolonged heating at elevated temperature above 1100°C. Doping with Li2O much enhanced the solid–solid interaction between the mixed oxides leading to the formation of MgFe2O4 phase at temperatures starting from 700°C. The addition of 6 mol% Li2O to the mixed solids followed by precalcination at 1050°C for 4 h resulted in complete conversion of the reacting oxides into magnesium ferrite. The heat treatment of pure and doped solids at 900–1050°C effected the disappearance of most of IR transmission bands of the free oxides with subsequent appearance of new bands characteristic for MgFe2O4 structure. The promotion effect of Li2O towards the ferrite formation was attributed to an effective increase in the mobility of the various reacting cations. The activation energy of formation (ΔE) of magnesium ferrite was determined for pure and variously doped solids and the values obtained were 203, 126, 95 and 61 kJ mol−1 for pure mixed solids and those treated with 1.5, 3.0 and 6.0 mol% Li2O, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

20.
Novel alkylimidazolium-intercalated V2O5 compounds were synthesized by a redox reaction between iodide ion and V2O5. The X-ray photoelectron spectroscopy and the diffuse reflectance UV-vis spectrometry experiments reveal that the vanadium in the intercalated V2O5 products was partially reduced by an iodide ion and the resultant iodine can be removed in the final products. The transmission electron microscope observation and X-ray diffraction analysis testify that the prepared alkylimidazolium/V2O5 intercalation compounds have typical lamellar structure with different d100 interlayer spacing values and the special straw-like nanofiber morphology with the length of 0.5-10 μm. Systematic investigation indicates that new intercalation compounds possess the extraordinary adsorption performance for methylene blue in an aqueous solution.  相似文献   

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