Characterization and performance of Pd-La/spinel catalyst for preparation of 2,6-diisopropylaniline

The Pd-La/spinel catalyst for the preparation of 2,6-diisopropylaniline (2,6-DIPA) by gas-phase amination of 2,6-diisopropylphenol (2,6-DIPP) has been studied. The catalysts before and after reaction were characterized by BET, XRD, differential thermal analysis (DTA)-thermo gravimetric analysis (TGA), FTIR, and NH₃-TPD techniques. The DTA study results show two kinds of coke deposited on the metal and support of Pd-La/spinel catalyst, and they are combusted at about 242 and 324 °C, respectively. The XRD and FTIR spectra of the Pd-La/spinel catalyst show that the coke contains the aromatic and aliphatic rings, alkyl groups, polynuclear aromatic system, hydroxyl groups, and amine groups. The reason for catalyst deactivation can be expressed as follows: coke formed on palladium metals may move from metal to the interface or boundaries of metal-support and acid sites of the support where further dehydrogenation and polymerization are occurring. The H₂ plays a key role in retarding coke formation, but must be in suitable amount to get relatively high selectivity. The rare earth promoter La not only promotes the activity and selectivity by retaining Pd species in the metallic state, but also decreases the formation of carbon by neutralizing the strong acid sites on the catalyst.     

Glass Formation and Crystallization Behavior of a Novel GeS2–Sb2S3–PbS Chalcogenide Glass System

In the present work, a large glass-forming region was found in the novel GeS₂–Sb₂S₃–PbS system, in which up to 58 at.% PbS could be incorporated without deteriorating the thermal and physical properties of glasses. Infrared (IR) transmitting glass ceramics with a large amount of small-sized crystals (<100 nm) were then produced by choosing sub-stable compositions and annealing at fairly low temperatures (15°–30°C above T _g) for long durations (up to 100 h). Crystals were identified by X-ray diffraction as Pb₂GeS₄, PbGeS₃, PbS, PbSb₂S₄, etc., depending on base glass compositions. Compared with base glasses, glass ceramics showed much improved thermal shock resistance and fracture toughness, making them good candidate materials for IR optics.     

Synergistic effects of doped Fe3+ and deposited Au on improving the photocatalytic activity of TiO2

Fe³⁺ doped together with Au deposited TiO₂ (Au/Fe³⁺–TiO₂) was successfully prepared, which shows excellent photocatalytic activity for degradation of methyl orange (MO) under both UV and visible light (λ > 420 nm) illumination. Fe³⁺ has been confirmed by EPR to substitute for Ti⁴⁺ in the TiO₂ lattice, and Au exists as Au⁰ on the surface of the photocatalyst indicated by the results of XRD. Fe³⁺ and Au have synergistic effects on improving the photocatalytic activity of TiO₂. A proposed mechanism concerning the synergistic effects is discussed to explain the improvement of the photocatalytic activities.     

气体流量对化学气相沉积法制备碳纳米管的影响

用化学气相沉积法裂解乙炔制备无序多壁碳纳米管,以Fe/S iO2粉状物作为催化剂,考察了气体流量等环境因素对碳纳米管生长的影响。通过TEM和SEM分析得出,当N2流量分别为200、500和800 mL/m in时,碳纳米管的平均直径分别为20、36和82 nm,即碳纳米管的直径随着N2流量的升高而增大。当N2流量增加到800mL/m in时,还生成了大量的直径约为20~30 nm的碳纳米球。不通H2制备不出碳纳米管。     

Dendron-functionalized perylene diimides with carrier-transporting ability for red luminescent materials

This paper presents a series of dendrimers via a convergent synthetic approach with three generations, which contain perylene diimide cores, Fréchet-type poly(aryl ether) dendrons, and carbazole (CZ) or oxadiazole (OXZ) peripheral functional groups. The higher generation dendrimer has an obvious site-isolation or dilution effect of dendrons, which results in a relatively small red-shift of absorption and emission spectra when it forms a solid thin film for applications. The interactions between peripheral units and perylene diimide core in the dendrimers are also studied by steady-state and time-resolved fluorescence spectra under both direct and indirect excitation. The fluorescence data show that there exist two possible mechanisms, Förster energy transfer (FRET) and photo-induced electron transfer (PET), for dendrimers bearing carbazole units. No enhanced core fluorescence is observed because the energy transfer or light-harvesting potential of peripheral carbazole is counteracted by PET. While for dendrimers bearing oxadiazole units, no PET can take place between OXZ and perylene diimide since both of them are high electron affinity. The FRET and higher light-harvesting ability of oxadiazole without PET interfering result in the distinct enhancement of core emission in higher generation dendrimers. DSC results indicate that the incorporation of Fréchet-type poly(aryl ether) dendrons can improve the amorphous property and increase glass transition temperature (T_g). The preliminary EL results with single-layer architectures demonstrate that these dendrimers could be utilized as a promising kind of active red luminescent emitters with carrier-transporting ability. EL emission has the same recombination zone as PL, indicating that the recombination of excitons in fabricated EL devices is not close to cathode or anode vicinity. It is suggested that the site-isolation effect of dendron wedges is attributed to prevent the core luminorphores from approaching electrodes efficiently.     

黄腐酸结构、构象和聚集过程的分子模拟研究

自然界中广泛存在着的腐植物质(HS)有多种化学反应能力,诸如矿物质的风化、养分的生物有效利用和污染物的迁移等相关的生物地球化学反应能力。腐植物质的反应性取决于其官能团的化学特性与微观结构,同时又受到周围环境及介质组分的影响。为了更好地了解腐植物质在水、土壤中的结构、构象以及聚集过程,文中描述了以伯明翰东北部庙宇(TNB)的样本,按离子或非离子的黄腐酸分子结构建模研究的过程。该理论研究结果和黄腐酸的溶解度(偶极矩)、电子和振动光谱等一些实验研究的结果能很好的吻合。其中水分子的存在对静电有很大的稳定作用,并且随着离子化程度的增加,这种作用变得更强。在真空中,由于氢键和非键力相互作用增加,未离子化的聚集体比单体更稳定。因此,随着黄腐酸分子的离子化,聚集作用将不再发生。在溶液中,黄腐酸的浓度是聚集的关键因素。若当量浓度太低,含有两个黄腐酸的系统就不可能发生聚集,但是随着当量浓度的提高,系统中聚集体的数量也将上升,情况就发生改变。离子态是聚集的另一个关键因素。离子态的黄腐酸分子有着更高的负电荷,而这会增强能量势垒,阻碍由布朗运动引起的黄腐酸分子的相互接近。     

基体树脂对长玻璃纤维增强PP力学性能的影响

采用在线混合设备制备了长玻璃纤维(LGF)增强聚丙烯(PP)复合材料(LGF-PP),研究了基体性质及界面相容剂对LGF-PP力学性能的影响。基体树脂熔体流动速率的增加,使最终LGF-PP中的玻璃纤维长度从5.63 mm增至8.56 mm,提高了力学性能。与均聚PP比较,以共聚PP为基体树脂的LGF-PP冲击强度高出约10%,但其他性能略差。界面相容剂有利于增强玻璃纤维与PP的界面结合,拉伸强度和拉伸模量明显增加,但是冲击强度降低了20%～30%。     

废渣粉煤灰纤维棉增强PVC复合材料

本文选用废渣制成的粉煤灰纤维棉(FAF)和聚氯乙烯(PVC)树脂作为原料,成功制备了FAF/PVC复合材料,研究了FAF的表面处理及其加入量对复合材料力学性能、热性能和硬度的影响,并用SEM对复合材料的界面进行了表征。实验结果表明,相对于纯PVC树脂而言,复合材料含经KH550处理的FAF40phr时,拉伸强度提高约12%;含经软化剂处理的FAF10phr时,冲击强度提高约110%;含经偶联剂和软化剂联合处理的FAF10phr时,冲击强度提高约70%,拉伸强度提高约11%,维卡软化温度随FAF添加量的增加呈上升趋势。研究结果证明,KH550和软化剂联合使用会对复合材料起到有效的增强增韧效果,因此能提高复合材料中FAF的填充量。制成的环保型FAF/PVC复合材料不仅性能全面高于纯PVC,而且材料成本显著降低,为综合利用废渣FAF开拓了新方向。     

Determination of effectiveness factor of a partial internal wetting catalyst from adsorption measurement

The effect of partial internal wetting of catalyst pellets on apparent reaction kinetics at elevated temperatures and pressures is investigated experimentally and by modeling for benzene hydrogenation. A new method that combines adsorption and chemical reaction is introduced to study the kinetics influenced by capillary condensation of reagents at steady-state conditions. It is shown that the extent of liquid filling in the pellet interior has a critical effect on the global kinetics, and the current state of the catalyst depends on the history. Under certain conditions two steady states of the effectiveness factor exist. Moreover, either a decrease in temperature or increase in total pressure can increase the effectiveness factor. The model exhibits good agreement with experimental results.