氧化铝基表层ZrO2的相结构、孔结构及性能研究

近年来，双组份氧化物的性质和作用越来越受到人们的重视，国内外学者对TIOZ／A1203，Ceo。／AI。oa＊，MgO／AI。osRI等作了大量的研究．Zro。既可以做工业催化剂的载体，又可作添加剂或活性组份，它具有酸、碱、氧化和还原四种化学性质，在一氧化碳加氢合成甲醇中更具有重要作用·本文通过改变在7－AI。O3表面上Zro：负载量，研究了Zro。－AI。Oa体系的相结构及孔结构，并以CO氧化为模型反应，结合TPD－MS等实验技术研究并考察了添加Zroz对Alzoa基催化氧化及表面氧性能的影响，探讨Zroz的助催化作用·1实验部分（1）实验样…     

Advances in the Interfacial Assembly of Mesoporous Silica on Magnetite Particles

Interfacing magnetic particles with ordered mesoporous materials is an effective direction for the development of functional porous composite materials with rationally designed core–shell structures. Owing to the combined properties of magnetic nanoparticles and mesoporous silica (high surface area, large pore volume, porosity, and biocompatibility), core–shell magnetic mesoporous silica materials have generated tremendous interest in various disciplines, including chemistry, materials, bioengineering, and biomedicine. Interfacial assembly strategies enable the rational construction of magnetic mesoporous silica materials with well‐defined core–shell structure, morphology, pore parameters, and surface wettability, which can decisively influence their physical and chemical properties and thus improve their application performance. This Minireview summarizes recent progress in the synthesis of core–shell magnetic mesoporous silica and the adjustment of key parameters, including pore size, morphology, and pore orientation.     

Chemistry of alumina, reactions in aqueous solution and its application in water treatment

Due to the presence and significance of alumina in the natural aquatic environment and its increasing application in drinking and wastewater purification, the knowledge of the structure of alumina and its possible interactions with organic and inorganic compounds in water are of great importance. This is of particular importance in both the understanding of natural aquatic environment processes and efficient industrial applications. The chemistry of alumina reactions in water is complex. The adsorption ability of alumina towards organic and inorganic compounds might be influenced by several factors such as: surface characteristics of the adsorbent (surface area, density, pore volume, porosity, pore size distribution, pH(PZC) as well as mechanical strength and purity), pH of the solution, ionic strength, composition of water and the physicochemical properties of adsorbates. The aim of this paper is to give a brief review of the properties of alumina and its reactivity with organic and inorganic compounds present in aqueous solutions. It also summarises the usage of alumina and alumina supported phases in water treatment technology.     

块状石英纤维/Al_2O_3气凝胶复合材料的非超临界干燥法制备及表征

采用溶胶-凝胶法和常压干燥法以N,N′-二甲基甲酰胺(DMF)作为干燥控制化学添加剂制备了低密度石英纤维增强Al2O3气凝胶复合材料.通过氮气吸附-脱附实验比较研究了石英纤维对氧化铝气凝胶孔结构参数的影响;采用X射线衍射技术表征了在升温过程中石英纤维/Al2O3气凝胶复合材料的相结构变化;利用扫描电子显微镜和透射电子显微镜观察了Al2O3气凝胶基体及其石英纤维复合材料的微观形貌;初步探讨了DMF对Al2O3气凝胶形貌和密度的影响.研究结果表明石英纤维/Al2O3气凝胶复合材料成块性好,纤维与气凝胶基体结合紧密,石英纤维提高了Al2O3相转变温度,适量的DMF有利于形成均匀凝胶网络结构,减小干燥收缩压力.     

锆-铝复合氧化物的制备及酸腐蚀对其表面性质的影响

利用溶胶－凝胶技术制备了ZrO2-Al2O3复合氧化物,考察了不同的投料比时复合氧化物的物理化学性质,比较了不同浓度酸腐蚀前后氧化物微球的比表面积、孔径、表面酸碱性及复合氧化物中氧化锆、氧化铝摩尔比等物理化学参数的变化。     

胶溶法制备镧-钡共稳定氧化铝的性能

以硝酸为胶溶剂, 两种拟薄水铝石为前驱体, 用胶溶法制备了镧-钡共稳定的氧化铝. 采用X 射线衍射(XRD)、表面分析仪(BET)、氨气程序升温脱附(NH3-TPD)和NO2程序升温脱附(NO2-TPD)技术对所制备的镧改性和镧钡共改性氧化铝的结构特性和表面性能进行了表征. XRD结果表明, 改性氧化铝在1273 K焙烧后均以γ-Al2O3相存在. 当BaO添加量达到14%(w)时, 有少量BaCO3生成. BET结果表明, 在1273 K下焙烧5 h后, 5%(w)La2O3稳定的氧化铝(Ba-0)和5%La2O3与8%BaO共同稳定的氧化铝(Ba-8)均具有较大的比表面积, 各种氧化铝的吸附等温线表明它们的孔形状均为狭缝型孔和瓶型孔, 孔径分布曲线表明, 仅有样品Ba-8的孔径分布较宽, 孔径为6-10 nm, 其它三种样品的孔径均集中在10 nm; NH3-TPD结果表明, 随着氧化钡添加量的逐渐增多, 氧化铝表面的酸量、酸强度逐步减少. NO2-TPD结果表明, 添加BaO后载体对NO2的吸附量增多, 随着BaO含量的增多, 体相Ba(NO3)2增多. 由于样品Ba-8同时具有很好的织构性质、适中的表面酸量和酸强度分布及NO2吸附脱附能力, 使得以它为载体的催化剂具有最好的催化性能,丙烷的起燃温度和完全转化温度分别为526 K和593 K.     

高比表面积窄孔分布氧化铝的制备研究 Ⅱ.加硅的影响

 采用pH摆动法，以硫酸铝为铝源，以氢氧化钠为碱沉淀剂，考察了添加SiO2对沉淀氧化铝物性的影响．通过孔结构分析、粒度测定和电镜观察等证实，加入少量SiO2可使沉淀粒子分散、变小，颗粒相对均匀，从而提高了氧化铝的比表面积和孔集中的程度．当加入2．5％的SiO时，pH仅摆动2次，即可使氧化铝粉体的孔体积高达1．2ml／g，比表面积达380m2／g．这类氧化铝的孔结构适宜，粒子小，易直接成型为孔径集中和耐压强度好的载体，故用于重油高压加氢脱氮反应具有较好的性能．沉淀时酸侧pH值降低，尽管沉淀氧化铝的孔径向较小的方面集中，但此时沉淀粒子呈紧密堆积，颗粒变大，比表面积下降，氧化铝沉淀粒子的结构发生改变．不同结构的氧化铝表现出不同的催化活性．     

Characterization of covalently bonded and adsorbed polymer coatings on silica, alumina and zirconia by means of physico-chemical and chromatographic methods

Polymer coatings on porous silica, alumina and zirconia were prepared by covalent bonding of a copolymer of styrene and vinylsilane on the oxidic surface with or without subsequent cross-linking of the immobilized polymeric layer. Polybutadiene and polychloromethylstyrene were adsorbed on the surface of porous alumina without covalent bonding and were cross-linked after deposition. Analysis of the pore structure of coated oxides by means of nitrogen adsorption, mercury porosimetry and inverse size-exclusion chromatography revealed different polymer distributions across the modified surface and different changes of the porosity of the initial oxides depending on the method of polymer immobilization. By covalent bonding of the copolymer of styrene and vinylsilane to alumina and zirconia with subsequent cross-linking the modifying polymeric layer, highly hydrolytic stable packings were synthesized and their application in separations with aggressive eluents were demonstrated.     

Gas diffusion and microstructural properties of ordered mesoporous silica fibers

Pore and surface diffusion of carbon dioxide (CO(2)) and ethylene (C(2)H(4)) in the nanopores of ordered mesoporous silica fibers about 200 microm in length was measured by the transient gravimetric method. The experimentally determined pore diffusivity data, coupled with the porosity, pore size, and fiber length, are used to obtain the actual length of the nanopores in silica fibers. These measurements reveal a structure of the ordered nanopores whirling helically around the fiber axis with a spiral diameter of about 15 microm and a pitch value of 1.6 microm. At room temperature the surface diffusion contributes about 10% to the total diffusional flux for these two gases in the nanopores of the ordered mesoporous silica fibers. The surface diffusion coefficients for the ordered mesoporous silica fibers are about 1 order of magnitude larger than the non-ordered mesoporous alumina or silica with similar pore size.     

Effects of surface curvature and surface chemistry on the structure and activity of proteins adsorbed in nanopores

The interactions of proteins with the surface of cylindrical nanopores are systematically investigated to elucidate how surface curvature and surface chemistry affect the conformation and activity of confined proteins in an aqueous, buffered environment. Two globular proteins, lysozyme and myoglobin, with different catalytic functions, were used as model proteins to analyze structural changes in proteins after adsorption on ordered mesoporous silica SBA-15 and propyl-functionalized SBA-15 (C(3)SBA-15) with carefully controlled pore size. Liquid phase ATR-FTIR spectroscopy was used to study the amide I and II bands of the adsorbed proteins. The amide I bands showed that the secondary structures of free and adsorbed protein molecules differ, and that the secondary structure of the adsorbed protein is influenced by the local geometry as well as by the surface chemistry of the nanopores. The conformation of the adsorbed proteins inside the nanopores of SBA-15 and C(3)SBA-15 is strongly correlated with the local geometry and the surface properties of the nanoporous materials, which results in different catalytic activities. Adsorption by electrostatic interaction of proteins in nanopores of an optimal size provides a favorably confining and protecting environment, which may lead to considerably enhanced structural stability and catalytic activity.     

Influence of morphology and composition of fumed oxides on changes in their structural and adsorptive characteristics on hydrothermal treatment in steam phase at different temperatures

A series of fumed oxides such as silica, titania, alumina, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST), initial and hydrothermally treated (HTT) in the steam phase at T(HTT)=150, 250, and 350 degrees C was studied by adsorption, AFM, XRD, FTIR, and theoretical methods. Diminution of the size of primary particles (corresponding to increasing S(BET)) of initial silica and mixed oxides results in enhancement of their structural changes on HTT with elevating T(HTT) and increasing density of packing of primary particles in the secondary structures. Relative changes in the texture of treated fumed silicas are smaller than those of mesoporous silica gels occurring under similar HTT conditions. On HTT, aggregates of primary particles and their agglomerates become denser but their surface layers become looser because of transfer of silica fragments from one particle to another, and the smaller the initial primary particles, the greater the relative diminution of the specific surface area S(BET) for the same type of primary particle packing in aggregates. Relative changes in the pore volume V(p) (or V(BJHd)) on HTT are more complex than that of S(BET), as for many samples the V(p) value increases especially at T(HTT)=150 degrees C. Alumina and titania partially inhibit structural changes on HTT, which decrease in the series silica > SA > AST approximately ST.     

铝膜腔体内高度有序的介孔硅SBA-16的合成

在阳极铝膜腔体内, 以三嵌段聚合物F127为表面活性剂合成出一维纳米介孔二氧化硅材料. 采用压力诱导合成方法能使纳米纤维沿着铝膜腔体有序生长排列, 并且只存在于铝膜的腔体内, 在铝膜表面没有残留. 在纳米纤维的两侧可以清楚地观察到具有六边形结构的孔道, 直径为12 nm. 考察了正硅酸乙酯的水解时间以及化合物的不同配比对材料形貌的影响.     

锆-铝复合氧化物固定相的制备、表征及其色谱性能考察

利用溶胶-凝胶技术制备了无机杂化材料锆铝复合氧化物,对其物理化学性能进行了研究。平均孔径5-8nm,并且孔径分布较窄;表面呈现酸碱两性;氧化铝的掺杂可以提高填料的经表面积。同时以酸性、碱性和中性化合物为溶质,对锆铝填料的正相色谱性能和烷基膦酸改性的锆铝填料的反相色谱性能进行了系统评价,研究结果表明,锆铝填料适合于碱性化合物分离,并且其分离选择性在一定程度上随流动相性质而变;烷基膦酸改性的锆铝填料则呈现出反相色谱特征。     

A Urea Precursor to Synthesize Carbon Nitride with Mesoporosity for Enhanced Activity in the Photocatalytic Removal of Phenol

A urea precursor was used for the first time to prepare mesoporous carbon nitride (MCN) by a thermal polymerization process with silica nanospheres as a hard template. Although the prepared MCN samples have similar structures and optical properties, it was revealed that the specific surface area, pore‐size distribution, and morphology of the MCN samples depend on the initial mass ratio of urea to silica. Compared to the bulk carbon nitride (BCN) that only gave 20 % phenol removal (6 h of irradiation), the activities can be enhanced up to 74 % on MCN samples for photocatalytic removal of phenol under visible‐light irradiation. The highest conversion was obtained on MCN with an initial mass ratio of urea to silica of 5, which has high surface area of 191 m² g^?1 and a nanoporous structure with uniform pore‐size distribution of 7 nm. In addition to the high activity, the MCN sample also showed high photocatalytic stability.     

Preparation and properties of magnetic alumina microspheres with a γ-Fe_2O_3/SiO_2 core and Al_2O_3 shell

Magnetic alumina composite microspheres with γ-Fe 2 O 3 core/Al 2 O 3 shell structure were prepared by the oil column method. A dense silica layer was deposited on the surface of γ-Fe 2 O 3 particles (denoted as γ-Fe 2 O 3 /SiO 2 ) with a desired thickness to protect the iron oxide core against acidic or high temperature conditions. γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 particles with about 85 wt% Al 2 O 3 were obtained and showed to be suitable for practical applications as a magnetic catalyst or catalyst support due to their magnetic properties and pore structure. The products were characterized with scanning electron microscope (SEM) and transmission electron microscope (TEM), nitrogen adsorption-desorption, and vibrating sample magnetometer (VSM). The specific surface area and pore volume of the γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 composite microspheres calcined at 500 ? C were 200 m 2 /g and 0.77 cm 3 /g, respectively.     

Characterization of Silica-Containing Aluminum Hydroxide and Oxide Aerogels

Pure and silica-containing Al hydroxide aerogels were prepared by the supercritical drying method. The samples were later calcined, giving rise to alumina and Si–Al mixed oxides. The materials were characterized from the points of view of their bulk and surface structures. The Si-free material before calcination is well-crystallized boehmite that converts to γ-alumina by calcination. The silica-containing hydroxides are composed of boehmite layers with silicates in the interlayer region. The resulting mixed oxides present silica essentially in the bulk. The surface structure of alumina seems poorly sensitive to silica addition. Surface silanol groups appear only for SiO₂more than 4%. No Brønsted acidity appears. Silica addition allows mixed oxides with higher surface areas to be obtained.     

Tailoring pore properties of MCM-48 silica for selective adsorption of CO2

Four different types of amine-attached MCM-48 silicas were prepared and investigated for CO(2) separation from N(2). Monomeric and polymeric hindered and unhindered amines were attached to the pore surface of the MCM-48 silica and characterized with respect to their CO(2) sorption properties. The pore structures and amino group content in these modified silicas were investigated by XRD, FT-IR, TGA, N(2) adsorption/desorption at 77 K and CHN/Si analysis, which confirmed that in all cases the amino groups were attached to the pore surface of MCM-48 at 1.5-5.2 mmol/g. The N(2) adsorption/desorption analysis showed a considerable decrease of the pore volume and surface area for the MCM-48 silica containing a polymeric amine (e.g., polyethyleneimine). The CO(2) adsorption rates and capacities of the amine-attached MCM-48 samples were studied employing a sorption microbalance. The results obtained indicated that in addition to the concentration of surface-attached amino groups, specific interactions between CO(2) and the surface amino groups, and the resultant pore structure after amine group attachment have a significant impact on CO(2) adsorption properties of these promising adsorbent materials.     

Effect of the Al/Si atomic ratio on surface and structural properties of sol-gel prepared aluminosilicates

A series of aluminosilicates with an Al/Si ratio ranging from 0 to ∞ (0 for pure silica and ∞ for pure alumina) was prepared by sol-gel process and characterized by surface and structure techniques. Aluminum trisecbutoxide and tetramethylorthosilicate were used as precursors for the sol-gel synthesis. The acidic properties of the oxides were studied by determination of the zero point charges, through mass titration method, and, for selected samples, by FT-IR spectroscopy of adsorbed pyridine used as a probe for both Brønsted and Lewis acidity. A dependence of the acidity on the Al/Si atomic ratio was found. According to the X-ray diffraction patterns, all the oxides have an amorphous structure except pure alumina exhibiting a γ-alumina pattern. The surface areas of the mixed oxides increase with increasing amount of alumina and are higher as compared to the individual oxides. The surface elemental distribution and electronic properties were investigated by X-ray photoelectron spectroscopy. According to the results, good agreement between the surface Al/Si atomic ratio and the analytical ratio is obtained.     

介孔氧化铝的制备及其在甲醇脱水制二甲醚反应中的应用

以硝酸铝为铝源,以十六烷基三甲基溴化铵为阳离子模板剂,采用均匀沉淀法成功制得热稳定性较高和高度有序的介孔Al2O3(其比表面积179.8 m2/g,孔径5.4 am,孔体积0.3 cm3/g),并用于甲醇脱水制二甲醚反应中.结果表明,在280℃,液时空速为30 h-1条件下,甲醇转化率为90.2%,二甲醚时空收率最高可...     

Laser desorption/ionization mass spectrometry on porous silica and alumina for peptide mass fingerprinting

We investigated a variant of desorption/ionization on porous silicon (DIOS) mass spectrometry utilizing an aqueous suspension of either porous silica gel or porous alumina (pore size of 60 and 90 A, respectively). Laser desorption/ionization (LDI) from samples directly deposited on a stainless steel surface without any inorganic substrates was also achieved. Synthetic peptides designed to cover large sequence diversity constituted our model compounds. Sample preparation, including material conditioning, peptide solubilization, and deposition protocol onto standard matrix-assisted laser desorption/ionization (MALDI) probe, as well as ionization source tuning were optimized to perform sensitive reproducible LDI analyses. The addition of either a cationizing agent or an alkali metal scavenger to the sample suspension allowed modification of the ionization output. Comparing hydrophilic silica gel to hydrophobic reversed-phase silica gel as well as increasing material pore size provided further insights into desorption/ionization processes. Furthermore, mixtures of peptides were analyzed to probe the spectral suppression phenomenon when no interfering organic matrix was present. The results gathered from synthetic peptide cocktails indicated that LDI mass spectrometry on silica gel or alumina constitutes a promising complementary method to MALDI in proteomics for peptide mass fingerprinting.