Effects of precursor moisture and inert N_2 atmosphere calcinations on structure and properties of alumina modified CeZrLaNd mixed oxides

CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of cerium zirconium mixed oxides are the key properties for the automotive catalysts so as to meet the strict emission regulations. In this work, alumina modified CeZrLaNd mixed oxides were prepared by a co-precipitation method. The effects of moisture in precursor and inert N2 atmosphere during calcinations on the structure and properties were investigated by Brunauer-Emmett-Teller(BET) surface area measurements, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), hydrogen temperature-programmed reduction(H_2-TPR), oxygen storage capacity(OSC), Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). The results show that the moisture in precursor during calcinations increases the crystal grain size of the cerium zirconium mixed oxides, improving the thermal stability. And the aged surface area of sample after being calcined at1000 ℃ for 4 h reaches 68.8 m~2/g(5.7% increase compared with the common sample). The inert N2 atmosphere endows a great pore-enlarging effect, which leads to high fresh surface area of 148.9 m2/g(13.5% increase compared with the common sample) and big pore volume of 0.5705 mL/g. The redox and oxygen storage capacity are also improved by inert N2 atmosphere with high OSC value of 241.06μmolO_2/g(41.3% increase compared with the common calcination), due to the abundant formation of the crystal defects and oxygen vacancies.     

球形氧化镍粉末对乙醇的电催化性能的研究

通过水热-热分解法制备球形介孔氧化镍粉末,并采用X射线衍射、扫描电镜、透射电镜和比表面积仪对氧化镍粉末的形貌和结构进行表征;通过循环伏安法、计时电流法和电化学阻抗谱的测试,系统研究该种粉末在碱性介质中对乙醇的电催化氧化活性.结果表明:所得到的氧化镍粉末为球形,比表面积为35 m2·g-1,平均孔径为15.88 nm;该粉末对乙醇具有良好的催化活性,氧化电流随乙醇浓度和扫描速率的增大而增大,在0.60 V电位下保持1000 s,球形多孔氧化镍对乙醇氧化催化的电流衰减率为0.075%,稳定性比较好.循环伏安法、计时电流法和电化学阻抗谱测试表明,球形介孔NiO/玻碳电极(NiO/GCE)对乙醇的催化氧化反应机理为扩散控制.      

Preparation and performance of CeO_2 hollow spheres and nanoparticles

CeO_2 hollow spheres were synthesized by polystryrene sphere(PS) templates and CeO_2 nanoparticles were prepared by a facile method. The as-obtained products were characterized by scanning electron microscopy(SEM), N_2 adsorption-desorption, X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR) and UV-vis diffuse reflectance spectra. The results showed that the structure of the obtained CeO_2 hollow spheres was hollow microsphere with a diameter of 380 nm and the average particle size of CeO_2 nanoparticles was about 1700 nm. The two samples' Brunauer-Emmett-Teller(BET) surface area was 67.1 and 37.2 m~2/g. The CeO_2 hollow spheres had a better performance than nanoparticles at UV-shielding because of higher surface area and the structure of hollow sphere.     

Effect of cerium oxide prepared under different hydrothermal time on electrocatalytic performance of Pt-based anode catalysts

In this paper,CeO_2 with a pore size of 2-4 nm was synthesized by hydrothermal method.The CeO_2 modified graphene-supported Pt catalyst was prepared by the microwave-assisted ethylene glycol reduction chloroplatinic acid method,and the effect of the addition of CeO_2 prepared by different hydrothermal reaction time on the catalytic performance of Pt-based catalysts was investigated.The microstructures of CeO_2 and catalysts were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),specific surface area and pore size analyzer(BET),scanning electron microscopy(SEM) and electron spectroscopy(EDAX),transmission electron microscopy(TEM),and the catalysts electrochemical performance was tested by electrochemical workstation.The results show that the catalytic performance of the four catalysts with CeO_2 is better than that of the catalyst without CeO_2.Adding CeO_2 with a specific surface area of 120.15 m~2/g prepared by hydrothermal reaction time of 39 h to Pt/C synthesis catalyst,its electrocatalytic performance,stability and resistance to poisoning are the best.The electrochemical active surface area is 102.83 m~2/g,the peak current density of ethanol oxidation is 757.17 A/g and steady-state current density of 1100 s is 108.17 A/g which shows the lowest activation energy for ethanol oxidation reaction.When the cyclic voltammogram is scanned for 500 cycles,the oxidation peak current density retention rate is 87.74%.     

Methanol Oxidation over TiO2-modified Multi-walled Carbon Nanotubes Supported Pt-Mo Electrocatalyst

In order to develop a novel and high-performance catalytic material for direct methanol fuel celIs(DMFC), molybdenum oxide as a co-catalyst with Pt on multi-walled carbon nanotubes which were modified by titanium dio- xide(denoted as CNTs@TiO<,2>) was investigated. The physicochemical characterizations of the catalysts were carried out via X-ray diffraction(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). Cyclic voltammetry(CV) showed that the CO-tolerance performance increased in the sequence of Pt/CNTs< Pt/CNTs@TiO<,2>. The improved CO-tolerance performance of the Pt-Mo/CNTs@TiO<,2> catalyst can be attributed to the combined beneficial effects of highly dispersed Pt nanoparticles on the CNTs, the existence of oxygen holes in the MoO<,3> layer structure and the oxidation capability of TiO<,2>.     

镍掺杂介孔二氧化锰的制备及放电性能

为了提高二氧化锰在碱性锌锰电池中的放电性能,利用二氧化硅模板通过水热法合成了具有高表面积的介孔二氧化锰,并通过镍离子的掺杂进一步改进其性能。采用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射仪（xRD）和全自动氮吸附比表面仪对样品进行了检测,电化学结果表明：镍掺杂5％的样品放电性能最佳,其比表面积高达115．45m^2／g,平均孔径为14．26nm。在250mA／g电流密度下恒电流放电容量为359．5mAh／g,与电解二氧化锰（EMD）相比,放电性能提高244．3％。     

Mechanism of CeO_2 synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion

In this paper,the formation mechanism of mesoporous CeO_2 synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion,as well as the structure-activity relationship between them were studied in depth.The self-assembly process and physicochemical properties of CeO_2 were characterized by thermogravimetry analysis,powder X-ray diffraction,N_2 adsorption/desorption,high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy techniques.Characterization results show that Ce-MOF is completely decomposed into pure mesoporous CeO_2 when the decomposition temperature is higher than 400℃.At this threshold temperature,CeO_2(400) has the largest specific surface area and pore volume of 114 m~2/g and 0.152 cm3/g,respectively.CeO_2(400) exhibits very high catalytic activity for benzene combustion,which can completely catalyze the degradation of benzene at 260℃.Meanwhile,the mesoporous CeO_2(400) supported Pt nanocrystalline catalysts were prepared by high temperature solution-phase reduction method.Pt/CeO_2(400)can completely degrade benzene at about 200℃ and represents high durability and good waterresistance for benzene combustion during 100 h of continuous reaction.     

Influence of [La(EDTA)]~- on pore structure of activated alumina carrier at high-temperature

The activated alumina as a catalyst carrier were widely used in automotive exhaust catalysts under high temperature,such as,petroleum refining catalysts,hydrogenation and hydrodesulfurization catalyst carrier in China and abroad.γ-Al2O3 was the catalyst carrier that was the most widely used and the best carrier of improved specific surface area .However,the activation of the coating consisted of γ-Al2O3 were usually transformed into α-Al2O3 at 800 oC,causing increased density,reduced specific surface area,and the collapse result of pore structure.While the temperature reached 1200 oC,activation of coating detached from the carrier,the resistance of flowing gas increased,catalytic activity decreased.Addition of La2O3 stabilized the γ-Al2O3 crystal structure,which would keep the activation stability of coating at a high temperature and inhibit activity loss.The activated alumina carrier treated with the solid-pore-expanding agent containing [La(EDTA)]-that synthesized using solid and solid-hybrid approach with the thermal stabilizer lanthana and EDTA at the high-temperature had a 10-30 μm large pore porous network-like structure,after alumina was calcined at 1200 oC for 1 h.The specific surface area of four specimen were beyond 120 m2/g,while the sample specific surface area of x([La(EDTA )]-)=1% was up to 150.36 m2/g.     

TiO2-SiO2复合气凝胶的常压干燥制备及光催化降解含油污水活性

以钛酸四丁酯和正硅酸乙酯为原料,利用溶胶凝胶工艺制备出不同硅含量的TiO₂-SiO₂复合醇凝胶.结合老化液浸泡和小孔干燥工艺,在常压下干燥得到完整的TiO₂-SiO₂复合气凝胶块体.采用扫描电子显微镜、BET比表面积测试、X射线粉末衍射等测试手段对复合气凝胶的微观结构和物化性能进行了测试和表征.测试结果表明,复合气凝胶具有良好的性能,Ti和Si元素在气凝胶中分布均匀.随着SiO₂含量的增加,复合气凝胶的密度逐渐变小,比表面积增大,孔隙率增加,转变为锐钛矿相的相变温度升高.经高温煅烧晶化处理,复合气凝胶转变为锐钛矿相结构.以乳化后的渤海原油水溶液作为含油污水模拟溶液,测试了复合气凝胶对含油污水的催化降解性能.污水降解结果显示复合气凝胶对渤海原油污水具有较好的催化降解活性.在SiO₂摩尔分数低于30%时,随着硅含量的增加,复合气凝胶的光催化降解率升高;但当SiO₂摩尔分数高于30%后,继续增加SiO₂掺入量,反而造成复合气凝胶催化能力下降.对于SiO₂摩尔分数为30%的复合气凝胶,获得了最佳的催化降解效果,90 min催化降解率达95%.      

Synthesis and Characterization of Y-Doped Mesoporous CeO2 Using A Chemical Precipitation Method

Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.     

石灰微观结构对铁水预处理脱硫的影响

采用比表面积1.891~2.664 m²/g和平均孔径575.5~814.9 nm四种不同结构的活性石灰在高真空电弧熔炼旋淬一体机中进行铁水预处理脱硫实验。用扫描电子显微镜分析不同石灰样品表面形貌,并用全自动压汞仪测量石灰的比表面积和平均孔径。实验结果表明铁水脱硫率随着石灰平均孔径的增大而减小,随着比表面积增大而提高;最佳脱硫剂配比为1:50。可将铁水中硫含量从0.014%脱至0.001%。     

Effects of precipitate aging time on the cerium-zirconium composite oxides

Cerium-zirconium composite oxides with high performance were synthesized by a co-precipitation method, using zirconium oxychloride and rare earth chloride as raw materials. The effects of precipitate aging time on the properties of cerium-zirconium composite oxides were investigated. The prepared cerium-zirconium composite oxides were characterized by X-ray diffraction（XRD）, BET specific surface area, pulsed oxygen chemical adsorption, H2 temperature-programmed-reduction（H2-TPR）, scanning electron microscopy（SEM）, etc. The results showed that the precipitate aging time caused great effects on the properties of cerium zirconium composite oxides. With the increase of aging time, the cerium zirconium composite oxides showed enhanced specific surface area, good thermal stability, and high oxygen storage capacity（OSC）. The best performance sample was obtained while the precipitate aging time up to 48 h, with the specific surface area of 140.7 m2/g, and OSC of 657.24 μmolO2/g for the fresh sample. Even after thermal aged under 1000 oC for 4 h, the aged specific surface area was 41.6 m2/g, moreover with a good OSC of 569.9 μmolO2/g.     

无机盐模板剂法合成介孔CeO_2

以自制碳酸镁为模板,通过高速搅拌,加入硝酸铈溶液,以及以氨水为沉淀剂,获得介孔CeO_2前驱体,再通过低温焙烧后用弱酸去除模板剂碳酸镁,即得到介孔CeO_2.并采用XRD,BET,HRTEM,FT-IR等手段对其进行了表征.结果表明,利用无机盐碳酸镁为模板剂合成的介孔CeO_2,比表面为129m~2/g,平均孔径为5nm.     

Effect of Preparation Method on Surface Area and Crystalline Form of CeO2-ZrO2 Solid Solution

TheCeO2 ZrO2 solidsolutionisacrucialcompo nentinthethree waycatalysts(TWCs)usedtocatalyzethesimultaneouspurificationofCO ,HCandNOxfromanautomobileexhaust [1～ 3] .Besidesafeasiblecatalyticactivity ,itshouldhavehighthermalstabilityandoxygenstoragecapacity(OSC) .InordertogainhighperformanceCeO2 ZrO2 solidsolution ,varioustechniqueshavebeendeveloped .ItwasshownthataneffectofpreparationmethodonthesurfaceareaandcrystallineformofCeO2 ZrO2 isveryobvious .Intheearliestwork ,theCeO2 ZrO…     

Synthesis of Dy2O3 nanoparticles via hydroxide precipitation： effect of calcination temperature

This work described the preparation of dysprosium oxide, Dy2O3, nanoparticles using the homogeneous precipitation method. Dy3+ ions were precipitated using NaOH solution. The obtained product was filtered, dried, and then calcined for 1 h at the temperature range of 300–700 °C in static air. The calcination temperature of the Dy-precursor was chosen based on its decomposition as indicated by the TGA analysis. The crystalline structure and surface morphology of the calcined solids were studied by X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). The obtained results revealed that Dy2O3 with crystallites size of 11–21 nm was formed at 500 °C. Such value increased to 25–37 nm for the sample calcined at 700 °C.     

Influence of [La(EDTA)]− on pore structure of activated alumina carrier at high-temperature

The activated alumina as a catalyst carrier were widely used in automotive exhaust catalysts under high temperature, such as, petroleum refining catalysts, hydrogenation and hydrodesulfurization catalyst carrier in China and abroad. γ-Al₂O₃ was the catalyst carrier that was the most widely used and the best carrier of improved specific surface area . However, the activation of the coating consisted of γ-Al₂O₃ were usually transformed into α-Al₂O₃ at 800 °C, causing increased density, reduced specific surface area, and the collapse result of pore structure. While the temperature reached 1200 °C, activation of coating detached from the carrier, the resistance of flowing gas increased, catalytic activity decreased. Addition of La₂O₃ stabilized the γ-Al₂O₃ crystal structure, which would keep the activation stability of coating at a high temperature and inhibit activity loss. The activated alumina carrier treated with the solid-pore-expanding agent containing [La(EDTA)]^? that synthesized using solid and solid-hybrid approach with the thermal stabilizer lanthana and EDTA at the high-temperature had a 10-30 μm large pore porous network-like structure, after alumina was calcined at 1200 °C for 1 h. The specific surface area of four specimen were beyond 120 m²/g, while the sample specific surface area of x([La(EDTA)]^?)=1% was up to 150.36 m²/g.     

原状和重塑离子型稀土矿体的孔径分布特征

为获得离子型稀土矿原状矿体和重塑矿体的孔径分布特性,利用张力计对赣南典型的离子型 稀土矿体进行现场和室内的土-水特征曲线测试试验,依据拟合得到的土-水特征曲线计算原状矿体 和重塑矿体的孔径分布.研究发现院原状矿体的比表面积为1.313 m2/g,累积孔隙总体积0.224 4 m3/g, 重塑矿体的比表面积为4.205 m2/g,累积孔隙总体积0.236 5 m3/g.重塑过程改变原矿的孔径分布,使 矿体的比表面积增加3.2 倍,但有效孔隙总体积变化不明显,使得重塑矿体浸润效果更好,而渗透性 有所降低.      

Synthesis of ordered mesoporous γ-Al2O3：Eu^3＋ with high luminous performance and thermal stability

An efficient and convenient one-step process was developed for synthesizing new effective red luminous materials through ordered mesoporous γ-alumina assembling with Eu³⁺. Employing P123 as a structure-directing agent and hydrochloric acid, citric acid as pH adjustor, ordered mesoporous γ-alumina was fabricated by simple sol-gel method. The pore structure was characterized by X-ray diffraction (XRD), N₂ adsorption-desorption isotherms and transmission electron microscopy (TEM). The as-synthesized γ-aluminas had narrow pore-size distribution (5–7 nm), large surface area (246 m²/g) and high thermal stability (750–1000 °C). The luminous property of materials was characterized by Photoluminescence (PL) spectra. The γ-Al₂O₃:Eu³⁺ materials had efficient luminescence, and the emission strength was related to the content of Eu³⁺.     

孔结构对热电池用氧化镁吸附性能的影响

采用沉淀法制备用于热电池电解质流动抑制剂的氧化镁粉末, 通过调节氨水与镁盐的比例得到不同孔结构的粉末,采用XRD、SEM、TEM、FT-IR和N₂吸附-脱附等方法分析粉末的形貌和孔结构,研究孔结构对电解质漏液率和热电池性能的影响.结果表明:沉淀剂比例能显著改变孔结构,当n(NH₃·H₂O):n(Mg2+)=1.5: 1时,形成大量的介孔,比孔容提高到0.179 cm3/g,比表面积达到30.91 m2/g,氧化镁含量（质量分数）为35 %的电解质粘合板中漏液率仅为6 mg/cm2.适合吸附LiCl-KCl共晶盐的氧化镁孔径应在2~200 nm之间.电解质漏液率高导致热电池平均工作时间变短,氧化镁孔径过小会增加热电池平均激活时间.      

石灰活性和微观结构对铁水脱磷的影响

通过管式电阻炉,用工业铁块、磷铁和硫化亚铁配制0.40%P试验用铁水,造渣剂石灰:萤石=9:1,造渣剂与铁水的比例为1:50,熔融温度1600℃。采用场发射扫描电镜和全自动压汞仪研究了石灰的微观结构-比表面积（1.05~4.75 m²/g）、平均孔径（605~1404 nm）、孔容积（0.23~0.78 mL/g）、体积密度（0.80~3.10 g/cm³）和活性度（298~350 mL）对铁水脱磷的影响。结果表明,随着石灰活性度的增加,铁水脱磷率逐渐增加;随着比表面积、平均孔径、孔容积和体积密度的增加铁水的脱磷率均先增加后降低,当石灰比表面积2.5 m²/g,平均孔径750~850 nm,孔容积0.45~0.55 mL/g,体积密度2.0 g/cm³时铁水的脱磷率达到最好,其铁水脱磷率达到63.0%。