高效WO3掺杂MCF催化剂的合成及其在环戊烯选择氧化制戊二醛反应中的应用

以钨酸钠和正硅酸乙酯为前驱体直接合成高含量WO₃掺杂介孔氧化硅泡沫(MCF)催化剂. 在773 K焙烧后显示出更高的热稳定性. 小角X射线散射, N₂-物理吸附和透射电子显微镜结果表明钨物种嵌入后, 材料仍保持MCF特征的三维织构介孔特征. 紫外拉曼和紫外可见漫反射光谱结果表明钨物种主要以孤立的或者低聚态的氧化钨形式存在, 所以在氧化钨质量分数(w)低于20%时氧化钨物种能够高度分散在载体上. 在环戊烯选择氧化制戊二醛反应中, 反应16 h 后环戊烯的转化率达到100%, 戊二醛的产率达到83.5%. 催化剂重复利用实验表明催化剂的稳定性较好, 没有钨物种的脱落. 这种优异的催化性能归结于合适的氧化钨含量和高分散的钨物种.     

Acylated flavonol glycosides from Sedum aizoon

A new acylated flavonol glycoside (1) and a known compound (2) have been isolated from the whole plant of Sedum aizoon L. Their structures have been established as quercetin 3-O-[β-D-(2‴-O-(E)-feruloyl)-xylopyranosyl]-(1 → 6)-β-D-glucopyranoside (1) and rutin (2) by means of spectroscopic analysis and chemical methods.     

Remarkable difference in catalytic performance of an organoamino-functionalized MCM-41-HPA composite with controlled site-isolation and site-aggregation

The organoamino-functionalized mesoporous silicas with different distribution patterns—site-isolation or site-aggregation are prepared using post-grafting method. We have investigated the effects of the solvents and the catalytic reactivity of these catalysts. It is found that, using the polar ethanol as solvent, the catalytic center is site-isolated. Contrarily, the catalytic center is site-aggregated with the non-polar toluene. Characterization techniques, including transmission electron microscopy, nitrogen sorption experiments, thermogravimetric analysis, and ultraviolet-visible absorbance spectroscopy, demonstrate the most important dependencies of the distribution pattern on the polarity of solvent.     

Near-Infrared Methane Detection Device Using Wavelength-Modulated Distributed Feedback Diode Laser around 1.654 µm

By using a wavelength-modulated distributed feedback laser centered at 1.654 µm, a stand-alone near-infrared methane detection device was experimentally proposed based on the tunable diode laser absorption spectroscopy technique. An intelligent temperature controller, a scan and modulation module, and a cost-effective lock-in amplifier were developed to drive the distributed feedback laser and extract the second harmonic signal. Experimental results show that the relative detection error is less than 7% within the detection range of 0–10⁶ ppm, and the limit of detection is about 11 ppm with an absorption length of 0.2 m. Long-term monitoring on two gas samples (10³ ppm and 2 × 10⁵ ppm) suggests good stability with the maximum detection errors smaller than 7% and 2.5%, respectively. Due to careful design and integration, the developed near-infrared sensor reveals competitive performances compared with our previously reported sensing devices at the mid-infrared region.     

Two New Extended Frameworks Constructed from the Sandwiching Polytungstoantimonate Clusters

Two new tungstoantimonates Na₄H₂[{Co(H₂O)₃}₂Co(H₂O)₂W(H₂O)₂ (B-β-SbW₉O₃₃)₂]·33H₂O (1) and H₄[Mn₂(H₂O)₈Mn_3.5(H₂O)₇W_0.5(H₂O)(B-β-SbW₉O₃₃)₂]·20H₂O (2) have been obtained by the routine synthetic reactions in the aqueous solutions and characterized by elemental analysis, IR, TG analysis. Compound 1 is built from the sandwich-type polyoxoanions [{Co(H₂O)₃}₂Co(H₂O)₂W(H₂O)₂(B-β-SbW₉O₃₃)₂]⁶⁻, linked by Na⁺ cations to construct a 1-D chain-like structure. Compound 2 shows an interesting 2-D structure built up from sandwich-type anions [Mn_3.5(H₂O)₇W_0.5(H₂O)(B-β-SbW₉O₃₃)₂]⁸⁻ linked by additional Mn²⁺ ions, which represents the first example of pure inorganic 2-D structure based on the Mn-containing sandwich-type polytungstoantimonate clusters. The electrochemical and photochemical catalysis activities of compounds 1 and 2 have also been investigated.     

新型WO3/TiO2纳米管催化剂的合成及其在环戊烯选择氧化反应中的性能研究

采用水热合成法以P25为原料制备了介孔TiO2纳米管, 并根据TEM和XPS表征结果对其形成机理进行了初步分析. 然后, 以制备出的介孔TiO2纳米管为载体, 钨酸铵为钨源, 采用传统浸渍方法制备了介孔WO3/TiO2纳米管催化剂. 利用N2吸附, TEM, XRD, XPS及Raman等手段对固载后的多相催化剂进行了表征, 并研究了催化剂在环戊烯选择氧化制备戊二醛反应中的催化性能. 结果表明, 在介孔20% WO3/TiO2纳米管催化下环戊烯的转化率达97.9%, 戊二醛的选择性高达69.3%. 钨物种以高度分散状态存在于催化剂中, 并与载体间存在着较强的相互作用, 使得钨的溶脱量很小, 脱落的钨对反应几乎没有影响. 另外, 催化剂具有较高的稳定性, 可以重复套用7次. 失活后的催化剂可通过简单焙烧的方式再生.     

两亲三元壳寡糖衍生物的合成及其包合物的研究

本文报道了新型水溶性甲氧基聚乙二醇-b-聚己内酯两亲嵌段共聚物接枝壳寡糖(COS-g-PCL-b-MPEG)共聚物的合成, 研究了两亲三元COS衍生物的合成及在水溶液中α-CD与其的包合作用.     

纳米CdS-磺化聚苯胺（SPAn）多层复合膜的光学特性研究

研究了利用层-层自组织生长法制备的磺化聚苯胺-CdS纳米晶体复合膜的光学特性.研究发现，随样品中CdS 纳米晶体尺寸的减小，量子尺寸效应明显增强；在紫外吸收谱中表现为吸收边出现了明显蓝移；在光致发光谱中，不仅激子直接复合产生的带边发射产生了蓝移，而且陷阱态复合产生的宽带发射也发生了蓝移.还发现样品经低温退火处理后，激子复合产生的带边发射显著增强，发射带宽随纳米尺寸的减小而变窄.这说明退火后CdS 纳米晶粒的有序性和均匀度显著增加. 关键词： CdS 纳米晶体 SPAn 吸收 发光     

Implication of the role of oxygen anions and oxygen vacancies for methanol decomposition over zirconia supported copper catalysts

The interaction of methanol with Cu, monoclinic ZrO₂, and Cu/m-ZrO₂ catalysts has been investigated by temperature programmed desorption (TPD) and reaction (TPRS) with the aim of understanding the nature of the surface sites and the mechanism involved in methanol decomposition. A synergetic effect has been detected since the combination of copper and ZrO₂ significantly facilitates the methanol decomposition with the facile evolution of H₂ and CO species at much lower desorption temperature. In conjunction with DRIFTS and H₂-TPD measurements of the Cu/ZrO₂ sample reduced at elevated temperatures, methanol decomposition over Cu/ZrO₂ is suggested to occur primarily on ZrO₂ with the aid of the presence of oxygen anions and oxygen vacancies generated by species-spillover between copper and zirconia. The interface between copper and zirconia is also evidenced to be crucial to the decomposition of methanol, with the main role of metallic Cu being to provide sites for H₂ removal by efficiently recombining the hydrogen atoms formed during the dehydrogenation of species located on zirconia.     

金属塑性变形中位错组态演化模型及其应用

将位错理论与耗散结构、协同学等非线性科学相结合,建立了金属塑性变形中位错组态演化模型。利用该模型,分析和模拟了金属塑性变形、静态回复和蠕变过程中,微观位错组态演化过程及与之相对应的宏观力学行为。结果表明:在一个统一的理论模型基础之上,分析和研究金属塑性变形中出现的各种现象和问题是可行的。