负载型金属催化剂表面金属分散度的测定

简要介绍了几种催化剂表面金属分散度的测定方法,包括静态化学吸附法、动态化学吸附法、X射线光电子能谱法(XPS)、X射线衍射宽化法(XRD)和透射电子显微镜法(TEM)。同时,对这几种方法的适用范围、局限性和测定结果的一致性进行了讨论和总结。     

负载型催化剂中金属分散度的测定

介绍了负载型金属催化剂中金属分散度的四种测定技术,即化学吸附法(Chemisorp)、X射线衍射法(XRD)、透射电镜法(TEM)和X光电子能谱法(XPS)。Chemisorp设备简单、应用普遍、局限性小;TEM具有直观粒子形貌、大小及其分布的优点;XRD用于测定金属粉末粒子的大小,是比较成熟的技术;XPS测定金属分散度可定性指示。并通用于各类催化剂。     

负载型催化剂溶液浸渍制备专家系统的初步研究

浸渍过程的分析表明,浸渍制备涉及到大量的经验规律。因此,预测浸渍制备的条件参数是一个比较复杂的不确定性问题,使用专家系统方法有助于此类问题的解决。实现专家系统的关键在于知识的合理表述和系统框架的建造。在文中我们构成了一个浸渍制备的专家系统原型,该系统具备处理数值和非数值信息的功能。此外,讨论了浸渍知识的智能化处理问题。     

负载型金属催化剂制备新技术研究进展

负载型金属催化剂因为其独特的催化性能在众多领域得到广泛应用。传统的催化剂制备方法有浸渍法,沉淀法,离子交换法和熔融法等。文章综述了溶剂化金属原子浸渍法,超临界技术和微波技术在负载型金属催化剂制备中的应用。     

一种提高Mo—Ni／Al2O3催化剂金属分散度的方法研究

提出了一种提高Ｍｏ－Ｎｉ／Ａｌ２Ｏ３催化剂金属分散度的方法，并采用ＸＰＳ及连续流动高压微反等手段进行考查和评价。研究结果表明，向浸渍液中加入适当的有机酸，要明显提高Ｍｏ，Ｎｉ的分散度，进而改善了催化剂的活性及选择性。     

汽油加氢精制MoP催化剂制备的研究

按照Mo∶P摩尔比为1,称取2.729 g磷酸氢二铵((NH4)2HPO4)和3.65 g钼酸铵((NH4)6Mo7O24·4H2O)混合溶于去离子水中,采用氢等离子体还原法(PR)制备免焙烧的MoP催化剂。通过X射线衍射对磷化钼催化剂迚行表征。以二苯幵噻吩(DBT)/十氢萘溶液为加氢脱硫(HDS)反应模型化合物迚行催化反应活性评价。通过实验数据说明,PR法成功制备了体相MoP催化剂,且催化剂的颗粒尺寸较小,具有较高的DBT加氢脱硫反应活性。     

高表面积高分散度铜基催化剂的制备及其性能研究

本文对传统共沉淀法进行改进，成功制备出高表面积（383.87 m2/g）高分散度（42.74%）的新型Cu-O-Al骨架结构催化剂，表征结果表明，改进后的制备方法可以有效增大催化剂比表面积和孔容，并使得催化剂上铜物种的颗粒更小、分散度更高，进而表现出较高的催化活性。同时由于形成了Cu-O-Al骨架结构，可以显著抑制铜物种的移动，进而提高催化剂的稳定性。本文以成本较低的空气作为氧源，在典型催化剂（CuAl3）上反应温度300 ℃、较高液时空速2 h-1下，MOP最佳转化率为85.2%，MOA选择性为55.7%，且稳定运行32 h，而该空速下传统浸渍法制备的催化剂已基本无催化活性。     

等离子体制备负载型金属纳米催化剂的研究进展

等离子体主要是由离子、电子等粒子组成的呈电中性且高度离子化的气体。可在室温条件下,利用等离子体中的高能粒子对化学物质进行还原,避免高温条件下粒子发生团聚,易得到粒径小、分散性好的纳米颗粒。对近年来等离子体技术制备负载型金属纳米催化剂及其催化性能进行了综述。     

煅烧过程中影响铁铬催化剂强度的因素

利用Dn饱合最优实验设计方法考察了铁系变换催化剂煅烧过程中强度的影响因素。并用二次型方程关联了强度均值与煅烧时的主要影响因素的关系。结果表明,温度、时间、升温速率和原料含水率对催化剂强度的均值和可靠性都有显著影响。对实验结果进行了初步讨论。     

制备条件对吸附剂脱硫性能的影响

制备了FCC汽油脱硫吸附剂.考察了吸附剂制备条件对吸附剂脱硫性能的影响,确定了适宜的吸附剂制备条件.     

New catalysts with low amounts of active phase for CPO processes

The preparation and characterization of different catalysts containing equal amounts of Ni (0.660 wt.%) and Rh (0.022 wt.%) and their catalytic performances and stability in CPO of methane in hard reaction conditions have been investigated. All the catalysts were obtained from hydrotalcite-type precursors (HT), prepared according to different methodologies: (a) impregnation of the active phase on a support derived from a HT precursor, (b) coprecipitation, inserting Ni and Rh inside the HT precursor, or (c) coprecipitation on a support (-Al₂O₃) of a HT precursor containing the active metals. The different present phases as a function of the preparation method have been identified. The observed scale of activity in CPO of methane may be attributed to the dispersion of the metal particles and to the different surface area values of the catalysts.     

Preparation and properties of supported cobalt catalysts for Fischer-Tropsch synthesis

Alumina-supported cobalt catalysts have been prepared from different cobalt precursors to study the influence of the precursor on the ultimate metal particle size. Furthermore, the effect of the particle size on the catalytic performance (activity and selectivity) during Fischer-Tropsch synthesis has been investigated. The preparation of low-loaded cobalt catalysts (2.5 wt%) by incipient wetness impregnation using cobalt EDTA and ammonium cobalt citrate precursors resulted initially in very small cobalt oxide particles, as determined by XPS. The small oxide particles reacted during the thermal treatment in a reducing gas flow with the alumina support to cobalt aluminate, which was neither active nor selective during Fischer-Tropsch synthesis. The catalysts prepared with cobalt nitrate had larger particles that could be easily reduced to metallic cobalt. These catalysts were active under reaction conditions. High-loaded cobalt catalysts (5.0 wt%) prepared using ammonium cobalt citrate showed a larger particle size than the low-loaded catalyst prepared from the citrate precursor. The extent of reduction to metallic cobalt that could be achieved with the high-loaded catalyst was significantly higher than that with the low-loaded catalyst, as shown by magnetic measurements. Accordingly, the high-loaded catalyst exhibited a reasonable activity and, in addition, an interesting and remarkably high selectivity toward higher hydrocarbons, and also a very high Schultz-Flory parameter.     

Influence of pH and ionic strength on the metal profile of impregnation catalysts

In this study the influence of pH and ionic strength on the final metal distribution is investigated. After impregnation, catalysts are usually dried at temperatures between 50°C and 200°C. During this process, a redistribution of the metal occurs, which is a complex function of the drying conditions, the properties of the impregnating solution and the support material. In our model, transport in the gas and liquid phase is described by the dusty gas model, and the Nernst-Plank equation, respectively. The metal adsorption on the porous support is described by the Revised Physical Adsorption model developed by Agashe and Regalbuto (J. Colloid Interface Sci. 185 (1997) 174). In their model, the adsorption constant is a function of the pH and the ionic strength of the liquid solution. The results show that for a positively charged metal complex, the impact of drying is strong when the initial pH of the liquid solution is below the point of zero charge (PZC). In such a case, the metal accumulates at the particle surface when the convective flow is strong (high temperature), and at the particle center when the solute-metal diffusivity is high. A comparison of our model with a drying model that assumes a constant adsorption equilibrium constant shows that the variations of pH and ionic strength cannot be ignored when the initial adsorption constant is low and the pH below the PZC. In such cases, the adsorption constant increases over several orders of magnitude when pH and ionic strength effects are accounted for.     

超支化结构对水性聚氨酯脲分散液性能的影响

通过聚氧化丙烯二元醇(GE220)、二羟甲基丙酸(DMPA)和异佛尔酮二异氰酸酯(IPD I)和端羟基超支化聚酯(HBP)反应合成了聚氨酯(PU)预聚体,然后以乙二胺(EDA)为扩链剂,合成了一系列不同HBP含量的聚氨酯脲(HPUU)水分散液,讨论了HBP用量对其性能的影响。结果表明,与不含HBP的水性PUU分散液相比,引入交联结构后,所有的HPUU水分散液的粒径和表面张力稍有增大,粘度从39.29 mPa.s降到25.73 mPa.s,水分散液的高温和冻融稳定性基本不变。     

Effect of Dispersion Condition of Calcium Carbonate on the Crystallization and Melting Behavior of Polypropylene/CaCO3 Nanocomposites

Polypropylene/calcium carbonate (PP/CaCO₃) nanocomposites were prepared by melt compounding (C-1) and novel compounding process (C-2), respectively. Scanning electronic microscope (SEM) results illustrated that CaCO₃ nanoparticles were well dispersed at nanoscale in C-2, whereas the nanoparticles were mostly aggregate in C-1. Differential scanning calorimetry (DSC) measurements indicated the onset crystallization temperature was increased by 11.4°C and the supercooling wasdecreased by 13.68°C in C-2. A faster crystallization rate, a higher melting point, and a higher degree of crystallization in C-2 were also detected. Polarization light microscope (PLM) photographs showed the spherulites sizes of C-2 were 60 mm, whereas common spherulites with an average size of about 200 mm were observed in both pure PP and C-1. These phenomena demonstrated that the well-dispersed CaCO₃ nanoparticles could result in heterogeneous nucleation effect on PP even at quite low loading Q2 (1.5% wt.).     

Effect of swelling response of the support particles on ethylene polymerization

Macroporous and modified macroporous poly(styrene-co-methyl methacrylate-co-divinylbenzene) particles (m-PS and mm-PS) supported Cp₂ZrCl₂ were prepared and applied to ethylene polymerization using methylaluminoxane (MAO) as cocatalyst. The influences of the swelling response of the support particles on the catalyst loading capabilities of the supports as well as on the activities of the supported catalysts were studied. It was shown that the Zr loadings of the supports and the activities of the supported catalysts increased with the swelling extent of the support particles. The m-PS or mm-PS supported catalysts exhibited very high activities when the support particles were well swollen, whereas those catalysts devoid of swelling treatment gave much lower activities. Investigation on the distribution of the supports in the polyethylene by TEM indicated that the swelling of the support particles allowed the fragmentation of the catalyst particles. In contrast, the fragmentation of the support particles with poor swelling was hindered during ethylene polymerization.     

Ozone Decomposition over Cobalt Supported on Olive Stones Activated Carbon: Effect of Preparation Method on Catalyst Activity

Aqueous ozone decomposition was studied over highly dispersed cobalt nanoparticles supported on olive stones activated carbon (AC) prepared by: wetness impregnation (Co/AC_w) and incipient wetness impregnation (Co/AC_iw) with respect to pore volume. Nitrogen adsorption-desorption at 77K, SEM, XRD and XPS analyses were used to characterize the catalysts. Analyses results show that Co/AC_w was more uniformly dispersed on the AC than Co/AC_iw. The effect of the presence of tert-butanol as radical scavenger was also studied. Higher catalytic activity was measured for Co/AC_w than Co/AC_iw. Ozone decomposition extent goes to 99% in only 3 min in the presence of Co/AC_w compared to 60% and 58% using Co/AC_iw catalyst and AC, respectively.