Synthesis of Ln-doped MCM-41 mesoporous materials and their catalytic performance in oxidation of styrene

Using cetyl-trimethyl-ammonium bromide （CTMAB） as the template agent and tetraethylorthosilicate （TEOS） as the silica source, the MCM-41 mesoporous materials were synthesized with La or Ce incorporated in the framework under hydrothermal conditions. The structure and the state of La or Ce were investigated through the analyses of XRD, nitrogen adsorption-desorption, FT-IR, and UV-Vis. XRD and N2 adsorption-desorption results showed that Ln-MCM-41 exhibited the loss of the lattice ordering of the MCM-41 construct, and larger unit cell parameter and pore diameter than pure silica MCM-41. The FT-IR and UV-Vis results indicated the presence of isolated tetra-coordinated La or Ce ions in the framework and other Ln species dispersed highly on the Ln-MCM-41 surface simultaneously. Furthermore, their catalytic behaviors in the oxidation of styrene were studied using H2O2 as the oxidant. The La-MCM-41 catalysts exhibited high reactivity and the reactivity increased with the increase of the La content in the La-MCM-41 samples. On the contrary, Ce-MCM-41 catalysts showed low reactivity in the oxidation of styrene and the conversion of styrene decreased with the increase of the Ce content in the Ce-MCM-41 samples.     

铁尾矿为原料微波法制备介孔分子筛

以鞍山铁尾矿为硅源,CTAB为模板剂,采用微波辐照法合成出全硅介孔分子筛MCM-41。用N2低温吸附、FT-IR、XRD和TEM等表征手段考察了其比表面积、孔径分布、晶体形貌等特性。结果表明:微波辐射法合成的MCM-41分子筛诱导期极短,晶化速度很快,具有典型的按六方对称性排列的孔道结构,FT-IR证明了分子筛具有硅氧四面体骨架。     

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.     

Synthesis and Characterization of Mesoporous Titanium Dioxide Spheres

Mesoporous titanium dioxide spheres were synthesized by a convenient solvothermal method at room temperature with tetraethyl titanate as a procursor. Investigation by means of X-ray diffraction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), and N<,2> adsorption-desorption isotherms confirms that the sample has a mesostructure with a higher specific surface area and shows that the mesoporous TiO<,2> spheres have a diameter of 2 μm, the average pore size is about 5.9 nm, and the BET surface area and specific pore volume are about 236 m<'2>/g and 2.116 cm<'3>/g, respectively. The anatase and rutile mesoporous TiO<,2> spheres calcined at 700 ℃ show much better photocatalytic activity than the samples calcined at other temperatures and is comparable to an uncaicined sample in the photodegradation of Methyl Blue(MB) under the UV irradiation.     

Synthesis and characterization of branched yttrium hydroxide fluoride microcrystals with hierarchical tubular structure

Hexagonal yttrium hydroxide fluoride microcrystals were prepared by a two-step hydrothermal route using yttrium nitrate, sodium hydroxide and sodium fluoride as raw materials to react in propanetriol solvent. The samples were characterized by powder X-ray diffraction (XRD), energy dispersive spectrum (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier trans-form infrared spectroscopy (FT-IR), thermogravimetre and differential-thermogravimetric analysis (TG-DTA), which revealed that Y(OH)2.14F0.86 microcrystals were multi-branched and that the branches of Y(OH)2.14F0.86 microcrystals were composed of hierarchical tubes. This novel multi-branched and intriguing hierarchical tubular structure of yttrium hydroxide fluoride maybe has a potential application in photoelectric crystals. The formation of branched Y(OH)2.14F0.86 microcrystals with hierarchical tubular structure were due to the substitution reaction and Oswald ripening.     

Preparation and characterization of visible-light-driven europium doped mesoporous titania photocatalyst

Pure and different content europium(Eu) doped mesoporous titania were prepared by template method using Eu(NO3)3.6H2O andTi(OC4H9)4 as precursors and Pluronic P123 as template and characterized with X-ray diffraction(XRD),N2 adsorption-desorption measurements,and ultraviolet-visible diffuse absorption spectra.Their photocatalytic activities were studied by photodegradation phenol in water under visible light irradiation.The results showed that Eu doping restrained the growth of grain size and extended the p...     

Preparation of Neodymium-Doped Yttrium Aluminum Garnet Transparent Ceramics by Homogeneous Precipitation Method

Neodymium-doped yttriumaluminumgarnet(Nd∶YAG)transparent polycrystalline ceramics,laser ce-ramic matrix materials,are gradually becomingsubsti-tutes for single crystals because they are provided withpredominantly chemical stability,highly doped ionconcentration,excellent optical performance and hightemperature stability[1,2].Presently,the conventionallyused methods to produce Nd∶YAG powders are solid-state processes[3],chemical precipitation methods[4,5]andlowtemperature combustiontechniqu…     

Prominent catalytic activity of mesoporous molecular sieves in the vapor phase dehydration of cyclohexanol to cyclohexene

Cerium incorporated KIT-6 mesoporous materials were synthesized through direct hydrothermal method and characterized by using X-ray diffraction (XRD), nitrogen sorption isotherm (BET), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma -atomic emission spectroscopy (ICP-AES), diffuse reflectance ultraviolet visible spectroscopy (DRS-UV-Vis), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. It appeared that stable cerium ions were inserted into the silica framework of KIT-6, thus generating acid properties in their host materials. The catalytic activity of Ce-KIT-6 materials was evaluated in the vapor phase dehydration of cyclohexanol to cyclohexene and dicyclohexyl ether at different temperatures with various Si/Ce molar ratios. Ce-KIT-6 (25) showed higher activity with 54% cyclohexanol conversion and 64% selectivity to cyclohexene. The catalytic results indicated that Ce-KIT-6 mesoporous materials could be used as versatile and stable acid catalysts.     

金属氧化物改性丝光沸石柱状晶的制备及性能研究

以六亚甲基亚胺为模板剂,采用动态水热合成法制备了柱状晶紧密堆砌形貌的丝光沸石。采用等体积浸渍法制备了Cr_2O_3、MgO以及ZnO改性丝光沸石,并对其催化1-甲萘与均三甲苯的异构化-烷基转移耦合反应性能进行对比研究。采用XRD、N_2吸附-脱附、SEM和NH_3-TPD等手段对样品的结构和酸性质进行表征。结果表明,与颗粒形丝光沸石相比,丝光沸石柱状晶具有更大的比表面积、孔容和介孔孔容,酸强度相近而酸密度下降。在1-甲萘与均三甲苯的异构化-烷基转移耦合反应中,明显提高了1-甲萘及均三甲苯的转化率和产物中二甲基萘的收率。负载金属氧化物后,丝光沸石的比表面积和中强酸酸量下降,产物中2-MN选择性提高,而三甲基萘等大分子副产物选择性降低。可通过金属氧化物改性调变异构化-烷基转移耦合反应中产物的选择性。     

新型功能介孔材料的合成及其对铅离子吸附性能研究

2O3-3 %CaF2-KCl体系的初晶温度,并对测定数据进行回归分析,得到初晶温度的回归方程。研究结果表明,在铝电解质中添加氯化钾能够降低电解质的初晶温度。本文旨在获得铝电解质初晶温     

Synthesis and Spectral Properties of Nd3+:Gd3Ga5O12 Nanopowder for Transparent Laser Ceramics

Nd3 :Gd3Ga5O12 (Nd:GGG) nanopowder for transparent laser ceramics was synthesized using sol-gel method. XRD, SEM, and fluorescence spectrum were used to study the properties of Nd3 :Gd3Ga5O12 nanopowder. XRD patterns of samples show that it has a cubic structure. Meanwhile, pure Nd:GGG crystals were obtained at 1000 ℃ for 12 h. SEM photographs show that dispersed, uniform, ball-like Nd:GGG nanopowder is obtained. Both XRD and SEM results show that the crystallization degree and the grain size increase with the increase in calcining temperature. Analysis of fluorescence spectrum shows that fluorescence emission occurs at 1062.7 nm, which is the result of Nd3 (4F3/2→4I11/2) transition. Homogenous Nd:GGG nanopowder with a small grain size synthesized using the sol-gel method is favorable for sintering the transparent ceramic, which proves that the nanopowder obtained is suitable as a precursor for preparing GGG transparent ceramics.     

铁尾矿两步法制备多级孔ZSM-5分子筛

以铁尾矿为原料替代纯化学试剂,采用两步法制备含有介孔–微孔复合孔的多级孔ZSM-5分子筛。首先在介孔模板剂（CTAB）作用下合成介孔分子筛（MCM-41）,然后通过固相转换法将MCM-41晶化转变为多级孔ZSM-5分子筛。采用X射线衍射(XRD)、扫描电镜（SEM）、透射电镜（TEM）和氮气吸附脱附测试（BET）等技术对样品进行表征。实验结果表明,由于体系中没有液态水相参与,成功避免了CTAB与微孔结构导向剂（TPABr）在水溶液中相互竞争,从而得到高结晶度的多级孔ZSM-5分子筛。因此,本文为铁尾矿制备多级孔ZSM-5提供了一种全新方法。      

Preparation and Ionic Conductivity of Ultrafine Li2+xRExSi1-xO3 by Sol-Gel Method

Ｒｅｃｅｎｔｌｙ ,ｓｔｕｄｉｅｓｏｎｌｉｔｈｉｕｍｉｏｎｃｏｎｄｕｃｔ ｉｎｇｓｏｌｉｄｅｌｅｃｔｒｏｌｙｔｅｓｈａｖｅｂｅｅｎｏｆｍｕｃｈｉｎｔｅｒ ｅｓｔｂｅｃａｕｓｅｏｆｉｔｓｌｉｇｈｔｗｅｉｇｈｔａｎｄｌｏｗｅｌｅｃｔｒｏｄｅｐｏｔｅｎｔｉａｌ.Ｌｉ2 ＳｉＯ3ｃａｎｂｅｕｓｅｄａｓａｎｉｄｅａｌｂａ ｓｉｃｍａｔｅｒｉａｌｏｆｆａｓｔｉｏｎｃｏｎｄｕｃｔｏｒｏｗｉｎｇｔｏｉｔｓｓｔｒｕｃｔｕｒｅｃｈａｒａｃｔｅｒ[1 ] .Ｓｉｎｃｅ 1 970ｓ,ｓｏｌ ｇｅｌｍｅｔｈｏｄｈａｓｂｅｃｏｍｅａｐｒｅｐａ…     

Synthesis and Properties of Heteropoly Tungstovanadogermanic Complexes with Rare Earths

Ｈｅｔｅｒｏｐｏｌｙｃｏｍｐｏｕｎｄｉｓａｎｅｗｃａｔａｌｙｓｔｗｉｔｈｍａｎｙｆｕｎｃｔｉｏｎｓｉｎｃｈｅｍｉｓｔｒｙｉｎｄｕｓｔｒｙ .Ｉｔｓｅｘｃｅｌｌｅｎｔｃａｔａｌｙｔｉｃｐｅｒｆｏｒｍａｎｃｅｉｓｄｅｔｅｒｍｉｎｅｄｂｙｉｔｓｃｏｍｐｏｓｉｔｉｏｎａｎｄｓｔｒｕｃｔｕｒｅ .Ｉｔｈａｓｓｉｍｐｌｅｃｏｍｐｏｓｉｔｉｏｎａｎｄｆｉｘｅｄｓｔｒｕｃｔｕｒｅ ,ａｌｔｈｏｕｇｈｉｔｍａｙｃｏｎｓｉｓｔｏｆｍａｎｙｅｌｅｍｅｎｔｓ .Ｉｔｓｓｔｒｕｃｔｕｒｅａｎｄｐｒｏｐｅｒｔｙｃａｎｂｅｃｈａｎｇ…     

MCM-41 supported nano-sized CuO-CeO_2 for catalytic combustion of chlorobenzene

In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO_2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N_2 adsorption,HRTEM-EDS,H_2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB) were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO_2 particles is about 3-5 nm and adding CeO_2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO_2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO_2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce~(4+)and Ce~(3+),and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.     

微波外场对液相合成砂状氧化钇前驱体形貌的影响

在微波外场作用下,以YCl3溶液为原料、草酸为沉淀剂直接液相合成了大颗粒砂状Y2O3前驱体,采用SEM、XRD和TG-DTA对前驱体及热分解产物进行表征,考察了H2C2O4与YCl3的摩尔比、YCl3起始浓度、反应时间和反应温度等对前驱体形貌的影响.结果表明,在微波外场作用及H2C2O4与YCl3的摩尔比为2∶1、YCl3的起始浓度为0.5 mol/L、反应时间3 h和反应温度40℃液相合成条件下,可得到D50约为40μm的附聚形大颗粒砂状前驱体.     

Preparation of Y-H3PW12O40/TiO2 and La-H3PW12O40/TiO2 by hydrothermal method and its photocatalytic activity for dinitrotoluene decomposition

A series of mesoporous materials （H3PW12O40/TiO2, Y-H3PW12O40/TiO2 and La-H3PW12O40/TiO2） were prepared by a modified sol-gel-hydrothermal route, which realized the load and modification of H3PW12O40 at the same time. The prepared samples were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, nitrogen adsorption-desorption analysis, ultraviolet-visible absorption spectrum （UV-Vis） and scanning electron microscopy （SEM）. The XRD and FT-IR results displayed that the catalysts had uniform anatase phase and the primary Keggin structure of H3PW12O40 remain intact. Nitrogen ad-sorption-desorption analysis suggested that suitable doping of rare earth elements could increase the specific surface area from 177.9 m2/g （H3PW12O40/TiO2） to 229.5 （1 wt.%Y-H3PW12O40/TiO2） or 236.1 m2/g （1 wt.%La-H3PW12O40/TiO2）. Results of UV-Vis spectra showed that the band of the 1 wt.%Y-H3PW12O40/TiO2 and 1 wt.%La-H3PW12O40/TiO2 have an obvious redshift compared with the H3PW12O40/TiO2. Additionally, the composites were used as heterogeneous photocatalysts to the degradation of dinitrotoluene （DNT）. It is the first time that polyoxometalate （POM） is applied in the degradation of explosive wastewater.     

Lanthanum incorporated in MCM-41 and its application as a support for a stable Ni-based methanation catalyst

Herein, lanthanum was incorporated via hydrothermal synthesis into a MCM-41 framework structure with La/Si molar ratios from 0.01 to 0.1. Samples of NiO supported on LaMCM-41 were prepared using the impregnation method. The catalyst performance was evaluated using a fixed bed CO methanation reactor. A Ni/LaMCM-41 catalyst with La/Si = 0.1 shows the best catalytic performance with a CO conversion of almost 100% and a CH4 selectivity of 89.5% at 250 ℃ under a pressure of 1.5 MPa and at an airspeed of 36,000 mL/(g·h). Compared with Ni-La/MCM-41(La/Si = 0.1) and Ni/MCM-41 prepared via the impregnation method, Ni/LaMCM-41(La/Si = 0.1) shows a higher CO conversion and CH4 selectivity.In a 100 h stability test, the Ni/LaMCM-41(La/Si = 0.1) catalyst shows excellent stability; furthermore, the CO conversion is always greater than 98.0%, which is significantly better than the results for Ni/MCM-41.We experimentally demonstrate that elemental La enters the framework of MCM-41. The Ni/LaMCM-41 catalyst performs well because the La reduces the average particle size of the NiO particles and enhances the interaction between NiO and MCM-41; moreover, the introduction of La significantly inhibits the sintering of the catalyst and the formation of carbon deposits.     

Thermal conductivity of （Sm1-xLax）2Zr2O7 （x=0, 0.25, 0.5, 0.75 and 1） oxides for advanced thermal barrier coatings

Pyrochlore oxides of general compositions, A2Zr2O7, where A is a 3+ cation (La to Lu), are promising candidate materials for ap-plications as high temperature thermal barrier coatings because of their high melting points, high thermal expansion coefficients, and low thermal conductivities. In this study, oxides of Sm2Zr2O7, (Sm0.75La0.25)2Zr2O7, (Sm0.5 La0.5)2Zr2O7, (Sm0.25La0.75)2Zr2O7 and La2Zr2O7 were prepared by solid reactions at 1600 ℃ for 10 h using Sm2O3, La2O3 and ZrO2 as the reactants. The phase compositions of these ceramic ma-terials were analyzed by X-ray diffractometer (XRD) and fourier transform infrared spectroscopy (FT-IR) methods, respectively. The micro-structure was observed by scanning electronl microscope (SEM). The thermal conductivities of these ceramic materials were measured using laser-flash method. XRD and FT-IR results showed that pure ceramic materials with pyrochlore structure were prepared successfully. SEM results indicated that microstructures of these ceramic materials were dense and grain boundaries were very clean. The La2O3 doped Sm2Zr2O7 pyrochlores (Sm0.75 La0.25)2Zr2O7 and (Sm0.5 La0.5)2Zr2O7 had lower thermal conductivity than the undoped Sm2Zr2O7. The thermal conductivity of (Sm0.25La0.75)2Zr2O7 was found to be lower than that of La2Zr2O7. The results showed that these ceramic materials had the poten-tial to be used as candidate materials for TBCs.     

Preparing Process of Cerium Acetate and Rare Earth Acetate

Preparing process was presented and the influences of concentration of acetic acid, reaction temperature, the ratio of cerium carbonate and acetic acid, heat preservation time to the yield of cerium acetate were discussed.The crystalline cerium acetate and rare earth acetate such as ( La, Ce, Pr, Nd) (Ac) 3, ( Ce, Pr, Nd) (Ac) 3, ( Pr, Nd, Er,Y) (Ac) 3 and yttrium acetate were prepared under this condition.The shape, structure and composition of the crystals were determined by the methods of SEM, TG-DTA, X-ray diffraction and chemical analysis.The optimum prepared conditions of cerium acetate were described.This prepared process has characteristics such as simple process route, low cost, high yield, good quality, no pollution to environment, etc.