Preparation of Al2O3–ZrO2 mixed supports; their characteristics and hydrothermal stability

Al₂O₃–ZrO₂ mixed supports have been synthesised using a colloidal solution of ZrO(OH)₂ or a Zr(IV) propoxide solution in organic medium. Zirconia content in these samples was about 10% (36% of the theoretic monolayer). The hydrothermal stability (alumina→boehmite transformation at 230 °C, about 10 bar pressure, in the presence of water vapour) of these supports was then investigated by XRD. The presence of the zirconia over the alumina decrease the quantity of boehmite formed after the hydrothermal treatment. The dispersion of zirconia and the stability in hydrothermal conditions of the final support are function of the preparation method.     

Mesoporous carbon/zirconia composites: a potential route to chemically functionalized electrically-conductive mesoporous materials

Mesoporous nanocomposite materials in which nanoscale zirconia (ZrO(2)) particles are embedded in the carbon skeleton of a templated mesoporous carbon matrix were prepared, and the embedded zirconia sites were used to accomplish chemical functionalization of the interior surfaces of mesopores. These nanocomposite materials offer a unique combination of high porosity (e.g., ～84% void space), electrical conductivity, and surface tailorability. The ZrO(2)/carbon nanocomposites were characterized by thermogravimetric analysis, nitrogen-adsorption porosimetry, helium pychnometry, powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Comparison was made with templated mesoporous carbon samples prepared without addition of ZrO(2). Treatment of the nanocomposites with phenylphosphonic acid was undertaken and shown to result in robust binding of the phosphonic acid to the surface of ZrO(2) particles. Incorporation of nanoscale ZrO(2) surfaces in the mesoporous composite skeleton offers unique promise as a means for anchoring organophosphonates inside of pores through formation of robust covalent Zr-O-P bonds.     

助剂对低温水煤气变换反应Au/αFe2O3催化剂性能的影响

采用共沉淀法制备了系列Au/αFe2O3 MOxM=Zr、Al、Mg、Ca、Ba)催化剂，通过N2物理吸附、XRD、H2-TPR和CO2-TPD-MS等手段对催化剂的物化性质进行表征，考察了富氢下低温水煤气变换（WGS）反应中助剂对Au/αFe2O3催化剂性能的影响。结果表明，助剂ZrO2能有效提高Au/α Fe2O3催化剂在富氢气氛下低温WGS反应活性和稳定性，反应温度150℃时CO转化率可达88.45%，且催化剂具有较高的稳定性。研究发现，添加ZrO2助剂能抑制载体晶粒的生长，降低载体晶粒度，提高催化剂的比表面积，改善催化剂的还原性能和表面酸碱度，从而提高催化剂的催化活性和稳定性。     

Surfactants for CNTs dispersion in zirconia-based ceramic matrix by sol–gel method

Zirconium oxide is a ceramic material widely studied due to its mechanical and electrical properties that can be improved with the use of carbon nanotubes (CNTs) as reinforcement. The synthesis of CNT/zirconia composites by sol–gel method is still very scarce, due to the hydrophobic nature of the CNTs, being their dispersion in aqueous medium an intrinsic difficulty to the synthesis. In this work, we present a sol–gel synthesis for MWCNTs/zirconia composites, where two kinds of surfactants, sodium and ammonium stearates dissolved in water (1 g/100 mL), were used as dispersant agents for multiwall carbon nanotubes (MWCNTs). They are cheap and easy to prepare, and were very effective in dispersing the MWCNTs. Different quantities of MWCNTs (up to 5 wt%) were added in the solution of stearate/water and this solution with the highly dispersed MWCNTs was added to the zirconia sol–gel, producing composites of MWCNTs/zirconia with different concentrations of MWCNTs. All the powders were heat treated at 300 and 500 °C and the powder characterization was performed by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR). The composite MWCNTs/zirconia remained amorphous at 300 °C and presented a tetragonal phase at 500 °C with an average grain size of about 20 ± 3 nm, determined by the Scherrer equation from the XRD patterns. For these crystalline samples, TEM images suggest a more effective interaction between MWCNTs with ZrO₂ matrix, where it can be observed that the carbon nanotubes are fully coated by the matrix.     

费-托合成Co/ZrO2-Al2O3催化剂反应性能的研究

以ZrOCl2·6H2O和AlCl3为原料,采用共沉淀方法制得一系列不同ZrO2质量分数的ZrO2-Al2O3混合氧化物载体;并以该混合氧化物为载体,采用初湿浸渍法制得钴质量分数为12％的Co/ZrO2-Al2O3催化剂。XRD、NH3-TPD、TPR和原位IR等表征结果表明,随着混合载体中ZrO2质量分数的增加,载体比表面积先增加后减少,混合载体的平均孔径则小于单一氧化物ZrO2和Al2O3的平均孔径。ZrO2和Al2O3载体混合后会导致氧化物的比表面积和酸性增大并且有新的物相生成。当混合氧化物用作载体时,能够抑制载体表面金属钴的分散,改变催化剂的还原行为,降低催化剂对CO物种的吸附能力。CO加氢反应表明,与单一金属氧化物相比,钴负载ZrO2-Al2O3混合氧化物催化剂的加氢活性和重质烃选择性有所降低。     

Surface characterization of WO(3)/ZrO(2) catalysts

A series of WO(3)/ZrO(2) catalysts with tungsten (W) loadings ranging from 0.5 to 11.4 wt% was prepared by incipient wetness impregnation on a preformed ZrO(2) support. The oxidic catalysts were characterized using XRD, Raman spectroscopy, XPS, ISS, and IR spectroscopy. XRD and Raman results showed that the ZrO(2) support was predominantly present in the monoclinic form. XPS and Raman measurements indicated the formation of increasing amounts of W interaction species for catalysts with W loadings up to 8.8 wt% WO(3). In addition to the W interaction species, bulk WO(3) was also observed for catalysts with W loadings > or = 3.0 wt% WO(3). Comparison of the XPS results with coverage measurements by ISS and CO adsorption suggests that the W surface phase is in the form of two-dimensional polymeric patches for catalysts with W loadings 3.0 < or = wt% WO(3) < or = 4.5. For catalysts with W loadings >4.5 wt% WO(3), the results indicated an additional build-up of a bilayer (or multilayer) polymeric W species. Analysis of the hydroxyl region of ZrO(2) by IR spectroscopy showed that initial additions of W occur on the high frequency hydroxyl group. A schematic for the structure of the catalysts has been proposed based on the above observations.     

碱土金属对ZrO2-Al2O3及其负载Pd-Rh密偶催化剂的影响

采用胶溶法制备了一系列碱土金属改性的ZrO₂-Al₂O₃, 并以其为载体采用等体积浸渍法制备了Pd-Rh密偶催化剂. 采用低温N₂吸附-脱附、X射线衍射(XRD)、氨气程序升温脱附(NH3-TPD)对载体样品进行了表征. 结果表明, 碱土金属的添加增大了ZrO₂-Al₂O₃的比表面积, Sr-Zr-Al样品经1000 °C焙烧5 h后具有最大的比表面积, 为164 m²·g^-1. 对催化剂进行了H₂程序升温还原(H₂-TPR)、X射线光电子能谱(XPS)和活性表征, 考察了催化剂对C₃H₈的转化活性. 测试结果表明, 添加碱土金属能有效提高催化剂上丙烷的转化活性.     

纳米 ZrO2 作分散剂的 Ru-Zn 催化剂上苯选择加氢制环己烯

 采用水热法合成了比表面积分别为 34 和 87 m2/g 的 ZrO2 样品 (分别记为 ZrO2-34 和 ZrO2-87), 并考察了它们作分散剂时 Ru-Zn 催化剂上苯选择加氢制环己烯反应的性能. 结果表明, 两个 ZrO2 样品具有相近的纯度和物相, 晶粒粒径分别为 21.6 和 11.4 nm. 其中 ZrO2-34 具有较小的比表面积、较大的孔径、较小的粒径、集中的粒度分布和较大的堆密度, 因而更适合用作苯选择加氢制环己烯 Ru-Zn 催化剂的分散剂, 且循环使用多次催化剂仍表现出较高的选择性和稳定性.     

Synthesis of nano-sized MgO particle and thin film from diethanolamine-stabilized magnesium-methoxide

The effects of diethanolamine (DEA) addition on the crystallization behavior of magnesium methoxide and the stabilization behavior of the Mg-alkoxide were investigated using differential scanning calorimetry, thermogravimetry, X-ray powder diffraction, transmission electron microscopy, and X-ray photoemission spectroscopy. 20 mol% DEA additions to magnesium methoxide showed enhanced stability such that a time-dependent change in the sol was not observed in air. Moreover, the DEA addition enhanced the crystallization process. Crystalline MgO in the 20 mol% of DEA-added magnesium methoxide powder was observed at 300°C for samples processed in O₂ and a high degree of crystallinity was observed at 400°C when processed in O₂. The enhanced crystallization of Mg-methoxide with added DEA in O₂ is discussed in terms of structural relaxation and heat generation during the ignition of an organic species of DEA. Using a DEA added sol, a MgO thin film with a high degree of crystallinity was prepared at 400°C in O₂.     

Self-assembled colloidal crystals from ZrO2 nanoparticles

Ordered three-dimensional (3-D) assemblies of nanocrystalline zirconia were synthesized from aqueous suspensions of ZrO(2) nanoparticles without the need for hydrocarbon surfactants or solvents to control colloidal crystal growth. Nanoparticles were suspended in mild acid and subsequently titrated from low to neutral pH. The solubility was reduced as the surfaces were neutralized, promoting assembly of the nanoparticles into ordered monoliths. TEM measurements indicated the formation of three-dimensional, hexagonal faceted, micrometer-sized colloidal crystals composed of 4 nm diameter ZrO(2) nanoparticles. Lacking organic surfactants, the colloidal crystals were exceptionally robust and were sintered at high temperatures (300-500 degrees C) for further stability. Small-angle X-ray scattering (SAXS) measurements demonstrate that the samples become progressively more amorphous above 350 degrees C, although some ordered domains of nanoparticles persist. Additionally, the heat treatment dramatically increases the surface area of the colloidal crystals as water and residual organics are desorbed, revealing highly controlled interstitial spaces and pores.     

Effect of surface treatment with potassium permanganate on ultra-high molecular weight polyethylene fiber reinforced natural rubber composites

The effects of surface treatment using potassium permanganate on ultra-high molecular weight polyethylene (UHMWPE) fibers reinforced natural rubber (NR) composites were investigated. The results showed the surface roughness and the oxygen-containing groups on the surface of the modified fibers were effectively increased. The NR matrix composites were prepared with as-received and modified UHMWPE fibers added 0–6 wt%. The treated fibers increased the modulus and tensile stress at a given elongation. The tear strength increased with increasing fiber mass fraction, attained maximum values at 4 wt%. The hardness of composites exhibited continuous increase with increasing the fiber content. The dynamic mechanical tests showed that the storage modulus and the tangent of the loss angle were decreased in the modified UHMWPE fibers/NR composites. Several micro-fibrillations between the treated fiber and NR matrix were observed, which meant the interfacial adhesion strength was improved.     

Methanation of carbon dioxide on Ni/ZrO2-Al2O3 catalysts:Effects of ZrO2 promoter and preparation method of novel ZrO2-Al2O3 carrier

The novel nickel-based catalysts with a nickel content of 12 wt% were prepared with the zirconia-alumina composite as the supports. The new carriers, ZrO2 improved alumina, were synthesized by three methods, i.e., impregnation-precipitation, co-precipitation, and impregnation method. The catalytic properties of these catalysts were investigated in the methanation of carbon dioxide, and the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. The new catalysts showed higher catalytic activity and better stability than Ni/γ-Al2O3. Furthermore, as a support for new nickel catalyst, the ZrO2-Al2O3 composite prepared by the impregnation-precipitation method was more efficient than the other supports in the methanation of carbon dioxide. The highly dispersed zirconium oxide on the surface of γ-Al2O3 inhibited the formation of nickel aluminate-like phase, which was responsible for the better dispersion of Ni species and easier reduction of NiO species, leading to the enhanced catalytic performance of corresponding catalyst.     

Electrosteric Stabilization of Al(2)O(3), ZrO(2), and 3Y-ZrO(2) Suspensions: Effect of Dissociation and Type of Polyelectrolyte

The mechanisms of eight anionic polyelectrolytes stabilizing colloidal sized alpha-Al(2)O(3), pure ZrO(2), and Y(2)O(3)-doped ZrO(2) particles in aqueous solution are discussed. The polyelectrolytes studied were the Na(+) and NH(4)(+) salts of polyacrylic acid and polymethacrylic acid having different molecular weights. The particle-dispersant interactions were studied by measuring adsorption isotherms, particle size, thickness of adsorbed layer, and zeta potentials by elektrokinetic sonic analysis at different powder volume fractions (straight phi=0.01-0.3), pH, and electrolyte (KCl) content. The dissociation of the polyelectrolytes was studied by potentiometric titrations. The dissociation constant of the polymethacrylates was found to be 0.6 pH unit higher than that for the polyacrylates. High-affinity adsorption isotherms were observed over the pH range when the polyelectrolytes were fully ionized. The results show good correlation between adsorption isotherms and zeta potential data in systems of dispersed, dilute alumina particles. When particles and polymers were of equal charge (the same sign of charge) the polymer shell was thicker. At higher volume fractions (straight phi=0.3), and when alumina particles/added ammonium polyelectrolyte were of equal charge, a maximum in the absolute value of zeta potential resulted. Due to adsorption all the anionic polyelectrolytes studied provided electrosteric stabilization of the alpha-Al(2)O(3), and Y(2)O(3)-doped ZrO(2) suspensions by enhancing the zeta potential to 40 mV or over and by shifting the isoelectric point to lower pH, the low-molecular-weight polyelectrolytes decreasing the isoelectric point more than the polyelectrolytes having higher molecular weight. The polyelectrolytes studied failed to stabilize pure monoclinic ZrO(2) particles. Due to the shortness of the chain of polyelectrolytes studied, no bridging was observed between oppositely charged polyelectrolyte/alumina particles. Copyright 2000 Academic Press.     

A colloid "digesting" route to novel, thermally stable high surface area ZrO2 and Pd/ZrO2 catalytic materials

Zirconia having high thermal stability and high surface area (up to 160 m(2)/g at 700 degrees C) has been prepared by a colloidal "digesting" process. This material having demonstrated high surface areas at elevated temperatures was then applied as a catalyst support. A Pd colloid with diameter of approximately 12 nm has been successfully deposited on the high surface area zirconia material. All systems have been well characterized by TEM, X-ray diffraction, N2 adsorption isotherms, FTIR, elemental analysis and dynamic light scattering techniques. The colloidal Pd particles have been found homogeneously well dispersed in the hydrous zirconia matrix without aggregation. The Pd/ZrO2 catalysts have been screened for cyclohexene and 1-hexene hydrogenation activity and it was found that the catalyst is extremely active.     

Influence of processing technique on morphology and mechanical properties of PVC nanocomposites

This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were prepared on a two-roll mill or in a microcompounder, both were either processed once or via a masterbatch containing 20 phr MMT. The MMT was treated with non-ionic surfactants and analysed by thermo gravimetric analysis and X-ray diffraction prior to being added. The final composites were analysed and tested using X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), tensile test, and Charpy impact test. The dispersion was found to be best in the roll milled samples prepared via the masterbatch and the elongation at break and impact strength was also better for the roll milled samples. E-modulus and tensile strength, on the other hand, were significantly better for the microcompounded samples despite the larger particle size. This can be explained by a higher degree of orientation in these samples. Finally, it must be stated that the change in properties are not satisfactory. Although we see an increase in E-modulus, the decreased impact properties are not acceptable. The main reason for this is the lack of compatibility between the clay particles as observed by high resolution SEM.     

Transient DSC,a Novel and Rapid Method for Assessing Pharmaceutical Powder Compacts

The previously described method involving the use of transient DSC was applied to pharmaceutical powder compacts and to ceramic powder compacts. The samples were prepared by compressing powders of pentaerythritol tetraacetate and two kinds of alumina powder (differing in particle size distribution) up to a pressure of 20 MPa by using a jig. For pentaerythritol tetraacetate, a linear relationship was obtained between the parameter obtained by DSC and the compaction pressure. This revised version was published online in August 2006 with corrections to the Cover Date.     

锆改性钴基费-托合成催化剂催化性能的研究

 考察了助剂锆和金属钴负载量对锆改性Co／Al2O3催化剂催化性能的影响．结果表明，锆助剂能够高度分散在氧化铝载体上，而活性组分钴以一定尺寸存在；锆的添加能够明显地提高Co／Al2O3催化剂的催化活性和C5＋烃选择性，但助剂锆含量对催化剂催化性能的影响不大；在锆存在下，催化剂的催化活性随金属钴含量先升高后降低．进一步的研究表明，催化剂上烃形成速率的提高可能是由于锆助剂能够增加催化剂的活性位数目，增强桥式CO吸附的强度，在Co－ZrO2间形成界面．     

Au/ZrO2催化剂中ZrO2的尺寸效应:1,3-丁二烯加氢反应

在不同温度(673～1073K)下,于流动N2气中焙烧ZrO(OH)2醇(乙醇)凝胶,制备了不同尺寸的ZrO2-AN纳米晶(6～30nm).采用沉积-沉淀方法制备了相应的质量分数为0.7%的Au/ZrO2-AN催化剂.用XRD,XRF,TEM/HRTEM,EDS,N2吸附和1,3-丁二烯加氢反应对ZrO2-AN和Au/ZrO2-AN催化剂进行了表征.结果表明,在所有的Au/ZrO2-AN样品中,Au粒子的平均尺寸为4～5nm,ZrO2-AN的颗粒大小没有因为负载Au粒子而发生改变.1,3-丁二烯在Au/ZrO2-AN催化剂催化下能以100%的选择性进行加氢反应生成单烯烃.随着Au/ZrO2-AN催化剂中ZrO2-AN纳米晶尺寸的增加或“载体”焙烧温度的升高,1,3-丁二烯的转化率明显降低;1-丁烯的选择性先增加后减小,2-丁烯中反/顺异构体的摩尔比在0.5～1.0的范围内逐渐增大,TEM/HRTEM表征结果清楚地表明,Au/ZrO2-AN催化剂中Au粒子与ZrO2-AN颗粒接触界面/周边随ZrO2-AN颗粒尺寸的减小而明显增加,这很可能是含有更小尺寸ZrO2-AN纳米粒子的Au/ZrO2-AN催化剂具有更高的催化活性的重要原因.     

Effects of processing parameters on the mechanical properties of polypropylene random copolymer

The mechanical properties of polypropylene random copolymer (PP-R) with different processing parameters were studied. Special attention is devoted to the investigation of the influence of masterbatch addition on the variation in the mechanical properties of injection moulded PP-R. Tensile, instrumented Charpy impact, Shore D hardness, differential scanning calorimeter (DSC) and Vicat softening temperature (VST) tests were conducted on the test samples containing different colour masterbatches varying from 0.5 to 10 wt%. The observed changes in the mechanical behaviour are explained by the type and level of masterbatch content. The natural UV weathering performance of the PP-R material was studied from the masterbatch type point of view. The effect of processing parameters on material performance was studied on samples which were directly obtained from extruded pipes and on injection moulded samples.

Finally, the effects of storage time on the polymer properties were investigated.