The Structure and Catalytic Properties of Palladium-Silver and Palladium-Gold Alloys

The great differences between the catalytic activities of the Group VIII and the Group IB metals have attracted much attention, especially over the last 25 years, and explanations of these differences have been sought through studying the manner of activity variation in alloys formed between suitable pairs of metals. Selection of suitable alloy systems has presented difficulties. Most work has naturally been done on systems exhibiting a continuous range of solid solution, and hence Pt-Au and Pt-Ag alloys, both of which have miscibility gaps, have not been widely studied. Much work has been done on Ni-Cu alloys, but recent results have demonstrated the presence of phase separation in this system, and this has called into question the interpretation of the earlier work. The Pd-Ag and Pd-Au systems appear to have complete miscibility, and have consequently been much studied: it is to them that this review is directed.     

钙钛矿材料的结构、性能及催化研究进展

概述钙钛矿材料的结构特点及其非计量特性、吸附性能、酸碱性能、热稳定性能、氧化-还原性能等优异特性.基于钙钛矿材料特殊的结构特点和良好的材料性能,介绍了其在光催化、氧化催化、水气变换、高级醇合成及甲醇制备等方面的应用情况.     

Structure and Mechanical Properties of Codeposited Pyrolytic C-SiC Alloys

Alloys of pyrolytic carbon and silicon codeposited in beds of fluidized particles were investigated. X-ray diffraction measurements revealed only two phases, turbostratic C and β-SiC. Since the C crystallites are oriented randomly, the C was macroscopically isotropic, with apparent crystallite sizes in the range found for pure C deposited under similar conditions. Transmission and scanning electron microscopy showed that the SiC was generally distributed as small particles which tended toward larger particles and continuous laminations at high SiC concentrations. The fracture stress and Young's modulus were measured in 3-point bending; they increased continuously with increasing SiC content from values for pure isotropic carbons to values for chemically-vapor-deposited SiC.     

Structure and Catalytic Properties of Iron-Containing Bimetallic Catalysts

The world's largest industrial process, ammonia synthesis, uses promoted iron catalysts. Fifty years ago fused and promoted iron catalysts were first utilized in the Fischer-Tropsch synthesis. The importance of this latter process has increased during the last few years because of the current energy crisis. Iron sulfide catalysts were also used by Varga [1] for the high pressure hydrogenation of coal. This procese, however, has been substituted by other methods.     

离子聚合物/聚氨酯弹性体合金的形态结构与性能

以聚四氢呋喃醚二醇(PTMG)和甲苯二异氰酸酯(TDI)制备预聚体,再用含氢氧化单甲基丙烯酸锌盐(HZMMA)的混合扩链剂扩链制备了不同HZMMA含量的离子聚合物/聚氨酯弹性体(PUE)合金。采用原子力显微镜(AFM)、动态粘弹(DMA)、热重分析(TG)和X射线衍射(XRD)研究了HZMMA含量对离子聚合物/PUE合金的形态结构和性能的影响。结果表明,适量的HZMMA能够形成纳米级的poly-HZMMA粒子,改善了合金中PUE的微相分离程度;poly-HZMMA能够提高材料的储能模量和软段的最大降解温度;HZMMA发生了自聚且硬段相有结晶。     

SBS对PLA/PC合金结构与性能的影响

用苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)对聚乳酸/聚碳酸酯(PLA/PC)合金进行增韧改性,研究了SBS用量对合金力学性能、热性能、微观形貌的影响。结果表明:加入一定量SBS后,PLA/PC(50/50)合金的拉伸强度有所降低,弯曲强度变化不大,而冲击强度明显提高;合金的热变形温度略有下降,两相相容性有所提高。     

Electronic Structure and Catalytic Properties of Transition Metal Nanoparticles: The Effect of Size Reduction

Size reduction of metal particles results in the formation of nanoparticles having short-range order and metastable state. Modeling of the nanoparticles can be obtained by various approaches. The major arrangement is the use of a model support on which metal nanoparticles can be created in a controlled way. Another approach is the use of amorphous alloy as precursor in which the ensemble of active sites (normally small metal nuclei embedded into amorphous matrix) is created. The modeling will be illustrated through the paper using SiO₂/Si(100) on which several transition metals will be deposited by pulsed laser deposition. Ultraviolet photoelectron spectroscopic technique as well as transmission electron microscopic technique will be utilized in characterization of the samples. CO chemisorption and CO oxidation as test reaction will be applied to show the connection between catalytic behavior and electronic properties or morphology of nanoparticles.     

镁合金表面电弧离子镀TiAlN薄膜的结构与性能研究

镁合金抗腐蚀性能差,其腐蚀电位在实用金属中最负.针对这一问题采用表面镀膜的方法,在三组镁合金基体上采用电弧离子镀方法在相同的参数下制备了Al原子掺杂的TiAlN薄膜.通过XRD和SEM研究了不同镁合金基体上薄膜的微观结构;采用电化学极化曲线、Nyquist图和腐蚀形貌分析了不同基体上薄膜的耐蚀性能,采用划痕仪得到了膜基...     

PP釜内合金的合成与性能

采用负载型Ziegler—Natta催化剂合成PP／PB釜内合金,考察了第二段聚合温度和聚合时间对聚丁烯含量的影响。对所得的共聚合金用GPC、IR、DSC、索氏抽提方法进行了分析,研究聚合物组成。并讨论了合金组成对聚合物性能的影响。     

快速凝固Ni-Al基合金的结构特征与十八腈加氢催化性能

利用旋铸法制备了快速凝固 Ni3 1.5Al68.5合金 ,结合常规 Ni- Al合金对其结构特征和十八腈加氢催化性能进行了研究。结果表明 ,快凝 Ni- Al合金中 Ni2 Al3 和Ni Al3 相的含量显著增加 ,α- Al相的含量大幅减小 ;与常规 Raney Ni催化剂相比 ,快凝 Ni- Al合金活化后制得的新型 Raney Ni催化剂中 Ni的晶格常数增大 ,晶粒细化 ,比表面积增加 ,孔径尺寸减小 ,在制备伯胺和仲胺两种选择性反应中均显示出较高的活性和选择性。     

蛋壳型催化剂结构、制备方法及其催化性能影响因素分析

综述了蛋壳型催化剂结构及制备方法,并对蛋壳型催化剂的浸渍制备法和制备过程中的影响因素如溶液浓度、溶剂极性、浸渍时问、溶液pH值和载体等进行了总结和评述.介绍了活性组分呈蛋壳型分布对催化剂性能的影响以及活性组分最优分布状态理论.     

氢化酶的结构、催化机理及其应用

氢化酶既是生物制氢产业的研究热点,又是微生物代谢的关键酶。阐述了氢化酶的分类和特点,主要介绍了[Ni-Fe]和[Fe-Fe]氢化酶的活性中心结构、催化产氢机理以及氢化酶的利用价值。最后对氢化酶的研究进行了展望。     

Synthesis,Crystal Structure,Electrochemical and Catalytic Properties of Hybrid Polyoxomolybdate Clusters-Based Terbium Complex

The inorganic–organic compound based on polyoxomolybdate [Tb(C₂H₆SO)₈][PMo₁₂ O₄₀]·2C₂H₆SO·½H₂O (I) has been isolated and structurally characterized by single-crystal X-ray molecular structure, IR spectra, thermogravimetric analysis and cyclic voltammetry measurements. The catalytic activities of (I) were also tested. The title compound crystallizes in monoclinic crystal system with C2/c space group. In the crystal, the polyoxidometalate anions are arranged in chains parallel to the [010] direction. The complex cations are located between these layers and linked to the neighbouring anions via weak C–H?O hydrogen bonding interactions leading to the formation of three dimensional network structure. Their catalytic activity toward organic dye is quite sizeable since the target removal is about 68% in the presence of the system POM-Tb/H₂O₂ after 120 min.     

Studies on the Structure and Catalytic Properties for Heck Reaction of Troxerutin Supported Palladium Catalyst

Theoretical Foundations of Chemical Engineering - Troxerutin supported palladium (TXT-Pd) catalyst was prepared readily by using one-step synthetic method. As-fabricated TXT-Pd catalyst was...     

Structure and Catalytic Properties of Supported Vanadium Oxides: Support Effects on Oxidative Dehydrogenation Reactions

The effects of support (Al₂O₃, SiO₂, HfO₂, TiO₂, and ZrO₂) on the structure and catalytic behavior of supported vanadia in the oxidative dehydrogenation of propane were examined over a wide range of vanadium surface densities (0.5–15.0 VO_x/nm²). X-ray diffraction and Raman and UV-visible spectra showed that vanadia exists as highly dispersed species at surface densities below 7 VO_x/nm²on Al₂O₃, HfO₂, TiO₂, and ZrO₂, but as large V₂O₅crystallites on SiO₂. Surface structures evolve from isolated monovanadates to polyvanadate domains and V₂O₅crystallites as VO_xsurface density increases. Polyvanadates appear at lower surface densities on ZrO₂and TiO₂than on Al₂O₃and HfO₂. UV-visible edge energies decrease as VO_xdomains grow with increasing VO_xsurface density on all supports. Initial propene selectivities increase with increasing VO_xsurface density, as monovanadate species and exposed support sites, which favor primary combustion pathways, decrease in concentration. Oxidative dehydrogenation rates per V-atom reach a maximum on VO_xdomains of intermediate size, which provide a balance between the activity of surface VO_xspecies and their accessibility to reactants. Interactions with supports determine the type of VO_xstructures present at a given surface density, but turnover rates do not depend on the identity of the support when differences in VO_xstructure are taken into account. Oxidative dehydrogenation turnover rates are similar on polyvanadate species and on surface VO_xsites on bulk V₂O₅. The relative rates of oxidative dehydrogenation to form propene and of secondary propene oxidation to CO_xdo not depend on the identity of the support or on VO_xsurface density or structure. Thus, it appears that these two reactions require similar VO_xsurface sites and that these sites are present at similar surface densities on polyvanadate domains and small V₂O₅clusters.     

抗冲聚丙烯的结构与性能

用FTIR,Cryst-EX对MFR相近的两种市售抗冲聚丙烯结构与性能进行表征,发现乙烯含量更低的进口产品常温和低温抗冲击性能更佳。通过分析认为,乙烯链段在聚丙烯链上分布更加均匀,能生成更多的橡胶相,所以产品抗冲性能更好,综合性能更优。其中,国产料MFR为34.1 g/10 min,乙烯质量分数为11.3%,橡胶相含量为19.7%,橡胶相中乙烯含量为36.9%,常温简支梁冲击强度为11.2 k J/m2,低温简支梁冲击强度为6.5 k/m2。进口料MFR为33.2 g/10 min,乙烯质量分数为9.2%,橡胶相含量为27.7%,橡胶相乙烯含量为26.2%,常温简支梁冲击强度为15.3 k J/m2,低温简支梁冲击强度为7.5 k J/m2。     

聚碳酸酯/无规共聚聚丙烯合金的制备及性能研究

通过熔融共混法制备了聚碳酸脂(PC)/无规共聚聚丙烯(PPR)/POE-g-MAH合金。测试了合金的力学性能和流变性能,观察了合金的拉伸和冲击断面的形貌,并对共混体系的增韧机理进行了探讨。结果表明,利用PPR作为PC的增韧剂以降低PC对缺口的敏感性,改善了成型加工性能,同时确定了各组分的最佳质量比为:100/20/5。PC为连续相,PPR为分散相,POE-g-MAH作为增容剂增强界面间的相容性,有利于合金韧性的提高,两相界面脱粘和空穴化引发的剪切屈服是该共混体系能量耗散的主要形式。     

漆酶的结构与催化反应机理

漆酶是一种广泛分布的多酚氧化酶,主要由单一多肽、铜离子活性中心、糖配基组成。多肽链一般含有18种氨基酸,构成漆酶的结构主体;糖配基因漆酶的来源不同而异,是漆酶多样性的标志之一。漆酶活性中心的铜离子依据光学和磁学特性被分为3种类型:Ⅰ型或蓝型铜,Ⅱ型或通常型铜,Ⅲ型或偶联的双核型铜。漆酶的催化反应机理主要包括酶对底物的电子提取、电子的传递和氧分子对酶的还原三步,是一个通过电子转移发生氧化还原反应的过程。