Cyclopropanation on a highly active heterogeneous catalyst: CuO/TiO2-Al2O3

Some heterogeneous catalysts, cupric oxide supported on different supports, were prepared and employed to catalyze the cyclopropanation of styrene and 2,5-dimethyl-2,4-hexadiene with ethyl diazoacetate (EDA). The catalytic performance for cyclopropanation strongly depends on the nature of the support. A novel catalyst, CUO/TiO2-Al2O3, in which Al2O3 is modified with a monolayer TiO2, is found to be most active and selective for the cyclopropanation reaction. The yields of 93 and 94% cyclopropanes are obtained for styrene and 2,5-dimethyl-2,4-hexadiene at 40 degreesC as the substrates, respectively. The activity and selectivity in cyclopropanes are optimized with a monolayer dispersion of cupric oxide on the corresponding supports. (C) 2002 Elsevier Science B.V. All rights reserved.

Preparation of TiO2, CeO2, and ZrO2 hierarchical structures in "one-pot" reactions

In this paper, a novel template of carbon foam is used in building hierarchical structures of TiO2, CeO2, and ZrO2. They had multiscale morphologies, from nanowalls, nanoparticles to layer nanostructures. Oil a hundred-micron scale, the product was a sponge-like material constructed by nanowalls. On a hundred-nanometer scale, the electron microscope images showed that the nanowalls were porous and assembled by polycrystalline nanoparticles. Meanwhile, on one nanometer scale, many nanoparticles exhibited layer nanostructures with about 1.1 run of thickness and spacing. In mechanism section, the process analysis and characterizations suggested that the hierarchical structures were the combined result of two templates in a "one-pot" reaction. The mesoporous nanowalls were derived from carbon foams, while the layer nanostructures were the replicas of graphite sheets. The method has potential utilizations in preparation of various adsorbent and catalyst.

CO_2在TiO_2-CuO修饰Cu电极上的光电化学还原

制备了TiO2-CuO修饰Cu电极,并对CO2在该复合光电电极上的还原行为进行了研究。光电化学测试表明,TiO2有助于电极的光电转换,能注入更多的电子促进CO2还原。TiO2-CuO/Cu复合电极在光照条件下对CO2具有很好的光电催化还原活性,使还原电位正移约100 mV,同时有效地抑制了水的光电分解。Mott-Schottky曲线测定表明,TiO2-CuO/Cu复合电极具有n型半导体性质,其平带电位随光照时间的增加而负移。光谱及色质谱测试证明,CO2在TiO2-CuO/Cu复合电极上的光电化学还原产物为甲酸和甲醛,还有少量乙烯和甲烷。在-1.2 V条件下光照3 h,CO2的转化率可达32%。基于实验结果对CO2光电还原机理进行了推断。

Remarkable changes in the optical properties of CeO2 nanocrystals induced by lanthanide ions doping

Highly uniform and well-dispersed CeO2 and CeO2:Eu3+ (Sm3+, Tb3+) nanocrystals were prepared by a nonhydrolytic solution route and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), UV/vis absorption, and photoluminescence (PL) spectra, respectively. The result of XRD indicates that the CeO2 nanocrystals are well crystallized with a cubic structure. The TEM images illustrate that the average size of CeO2 nanocrystals is about 3.5 nm in diameter. The absorption spectrum of CeO2:Eu3+ nanocrystals exhibits red-shifting with respect to that of the undoped CeO2 nanocrystals. Under the excitation of 440 nm (or 426 nm) light, the colloidal solution of the undoped CeO2 nanocrystals shows a very weak emission band with a maximum at 501 nm, which is remarkably enhanced by doping additional lanthanide ions (Eu3+, Tb3+, Sm3+) in the CeO2 nanocrystals. The emission band is not due to the characteristic emission of the lanthanide ions but might arise from the oxygen vacancy which is introduced in the fluorite lattice of the CeO2 nanocrystals to compensate the effective negative charge associated with the trivalent ions.

Study on the lifetime of M-intermediate of bacteriorhodopsin film chemically modified with CeO2 nanoparticles

The characteristics of intermediates of bacteriorhodopsin (bR) can be verified by chemical modification of its surroundings. CeO2 nanoparticles, which were obtained using water-in-oil (W/O) microemulsion and calcined at various temperatures, were used as chemical additive for the modification of bR. X-ray diffraction (XRD) shows that the mean particle sizes for the samples calcined at 500 and 800 degrees C are approximately 10 and 30 nm, respectively. We prepared CeO2 nanoparticle modified poly(vinyl alcohol) (bR-PVA) films with an optical density of about 1.5 at the ground state. It is observed that the lifetime of the Wintermediate for the modified films is prolonged compared with that of the unmodified ones, and the lifetime increases with decreasing particle size. A probable mechanism, which is likely to involve effective molecular interactions between the CeO2 nanoparticles and the bR molecules, is discussed. The hydroxyl groups, which might arise from the interaction between the nanoparticles and the surrounding water molecules, help to lower the ability of the Schiff base of uptaking protons in the Wintermediate. The results indicate that controlling the interactions between biomolecules and various nanomaterials would enlarge the functionality and the range of the application of nanoparticles.

Preparation of CeO2-ZrO2 ceramic fibers by electrospinning

Electrospinning was employed to fabricate polymer-ceramic composite fibers from solutions containing poly(vinyl pyrrolidone) (PVP), Ce(NO3)(3)(.)6H(2)O and ZrOCl2-8H(2)O. Upon firing the composite fibers at 1000 degrees C, Ce(0.67)Zr(0.33)O(2)fibers with diameters ranging from 0.4 to 2 mu m were synthesized. These fibers exhibit strong resistance to sintering. They still have specific surface area around 11.8 m(2)/g after being heated at 1000 degrees C for 6 h.

Structure and electrical properties of Pr ans Sm doped CeO2 and Ce2MoO15 based solid electrolytes

Sin and Pr doped CeO2 and Ce6MoO15 based materials were synthesized by sol-gel method. The structure of the powders were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy(FE-SEM) and the electrical conductivity of the samples was investigated by AC impedance spectroscopy. By comparing the structure and electrical properties of different systems, it could be concluded that the electrical property of Ce6MoO15 based system is better than that of CeO2 system. The added Mo element resulted in the increase of gain size and improved the grain boundary conductivity notably below 600 degrees C, while the Pr dopant induced the smaller grain size and improved the grain boundary conductivity of the materials.

Studies on syntheses and properties of novel CeO2/Polyimide nanocomposite films from Ce(Phen)(3) complex

A series of cerium dioxide (CeO2,)/polyimide (PI) nanocomposites were successfully prepared from Ce(Phen)(3) and polyamic acid (PAA) via the solution direct-dispersing method, followed by a step thermal imidization process. TGA and XPS studies showed that the cerium complex decomposed to form CeO2, during the thermal imidization process at 300 degrees C. SEM observation showed that the formed CeO2, as nalloparticles was well dispersed in polyimide matrix with a size of about 50-100 nm for samples with different contents of CeO2. Thermal analysis indicated that the introduction of CeO2, decreased the thermal stability of nanocomposite films due to the decomposition of Ce(Phen)(3) in the imidization process, while the glass transition temperature (T-g) increased obviously. especially nanocomposite films with high loading of CeO2 exhibited a trend of disappearance off, DMTA and static tensile measurements showed that the storage modulus of nanocomposite films increased, while the elongation at break decreased with increasing CeO2 content.

用于烟气脱硝的堇青石基CuO/γ-Al2O3催化剂及制法和应用

一种用于烟气脱硝的堇青石基ＣｕＯ／γ－Ａｌ↓［２］Ｏ↓［３］催化剂重量百分比组成为：堇青石载体为７８．７－９３．８％，Ａｌ↓［２］Ｏ↓［３］为５－１６％，ＣｕＯ为１．２－５．３％。采用以高强度堇青石蜂窝陶瓷为基体，在其上涂敷载体γ－Ａｌ↓［２］Ｏ↓［３］后在浸渍一定浓度的ＣｕＯ。本发明具有采用简易高效的涂层方法，减少了γ－Ａｌ↓［２］Ｏ↓［３］膜的涂层裂痕，增加了γ－Ａｌ↓［２］Ｏ↓［３］涂层的牢固度。增加了γ－Ａｌ↓［２］Ｏ↓［３］的上载量；提高了催化剂的脱硝活性，寿命和稳定性的优点。

一种CeO2-CoOx复合氧化物载体及其制备方法

一种ＣｅＯ↓［２］－ＣｏＯ↓［ｘ］复合氧化物载体是Ｃｅ与Ｃｏ的摩尔比为Ｃｅ∶Ｃｏ＝０．１－０．６∶１，晶粒大小：１－５０ｎｍ，比表面积：５０－１８０ｍ↑［２］ｇ↑［－１］。采用利用溶胶凝胶法以钴和铈的无机盐溶液为前驱物，制备了ＣｅＯ↓［２］含量在低范围内的钴基复合氧化物。本发明具有制备的ＣｅＯ↓［２］－ＣｏＯ↓［ｘ］复合氧化物载体颗粒和组分分布均匀的优点。

一种CuO/Al2O3脱硫剂的再生方法

一种ＣｕＯ／Ａｌ＃－［２］Ｏ＃－［３］脱硫剂的再生方法是将吸硫的ＣｕＯ／γ－Ａｌ＃－［２］Ｏ＃－［３］脱硫剂在含氨气气氛中还原再生，再生温度为３５０－５００℃，空速为５００－３０００ｈ＃＋［－１］，再生时间为３０－９０分钟。本发明的再生过程简单，易操作，二次脱硫活性稳定，可实现脱硫温度下的有效还原再生；再生过程中生成的ＳＯ＃－［２］在低温条件下可与未反应的ＮＨ＃－［３］结合生成固体硫酸铵盐，不仅简化了再生后续处理工序，而且可增强本再生方法的经济效益，降低了脱硫综合成本。

一种CeO2-TiO2复合氧化物载体及其制备方法

一种ＣｅＯ↓［２］－ＴｉＯ↓［２］复合氧化物载体，其特征在于Ｃｅ∶Ｔｉ（摩尔比）为０．０５－０．４∶１，粒径为１－１００ｎｍ，比表面积为５０－２５０ｍ↑［２］·ｇ↑［－１］，孔体积为０．３－１．２ｃｍ↑［３］·ｇ↑［－１］，采用一般的混合沉淀、抽滤、洗涤、干燥、焙烧可制成不同比例的水凝胶、醇凝胶、气凝胶ＣｅＯ↓［２］－ＴｉＯ↓［２］复合氧化物载体，其特征在于采用钛的无机物为原料，所以大大降低了成本。

Preparation and characterization of nanocrystalline CeO2 by precipitation method

CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group O-H(5)-F-M3M, when calcination temperature is in the range of 250 similar to 800 degreesC. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.