NaAlO_2为铝源时不同碱源对MCM-22分子筛合成的影响

研究了以Na Al O2为铝源时不同碱源对MCM-22分子筛合成的影响。以KOH为碱源时,得到纯相MCM-22分子筛的K/Si O2比值范围变窄;在体系中引入含羟基的低聚物以后,合成纯相K/Si O2的比值范围得以扩大,其原因是羟基与碱羟基的作用降低了碱羟基的活度;在体系中引入硝酸钾,对合成没有影响。可以扩大在Si O2-Na Al O2-HMI-Na OHH2O体系中,以KOH为碱源,加入多羟基低聚物扩大了合成纯相MCM-22的K/Si O2比值范围;而KNO3的引入对合成结果影响较小。以Ba(OH)2为碱源时,当Ba/Si O2≤0.061时,可以得到纯相MCM-22分子筛,且样品的结晶度随着Ba/Si O2比值的增大出现一个最高点,当Ba/Si O2比值继续增大时,也即体系的碱度增大,合成产物则发生从无定形物-混晶的转变。在体系OH-/Si O2比值不变时,以(KOH+Na OH)为碱源,合成产物均为纯相MCM-22,且产物的结晶度随KOH/Na OH比值的增大而有所提高。采用KOH+Ba(OH)2作碱源,保持K/Si O2比值不变,随着Ba/Si O2比值的增大,产物MCM-22的结晶度逐渐减小。当其他因素不变时,合成产物随体系碱度的增大而逐步发生从MCM-22-无定形-转晶的变化;同时,MCM-22分子筛的结晶度随体系碱度的变化出现最大值。     

Nano-preparation promoting effectively luminescent properties of one-dimensional rare earth oxides

Rare earth (La,Nd and Tb) oxides with one-dimensional micro/nanostructures were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction (XRD), thermal gravimetry (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence. The results showed that the synthesized rare earth oxides behaved regular nano-and micro-scale structures. And the morphologies of samples depended on the radii of rare earth ions, with the help of two surfactants of sodium dodecyl sulfonic and PEG 600. Nanocrystalline La2O3:Eu3+ possessed good photoluminescence (PL) property and might be used as a nanosized phosphor, its PL intensity was altered by the doping Eu3+ concentration and the optimum concentration of Eu3+ was 3 mol.%. In comparison with bulk Eu3+/La2O3, Eu3+/nano-La2O3 showed better photoluminescence property, nearly equal to that of nanocrtstal-line La2O3:Eu3+. Tb4O7 microwires showed interesting photoluminescence properties.     

Effect of water vapor on the CO and CH4 catalytic oxidation over CeO2-Mox (M=Cu,Mn,Fe,Co,and Ni) mixed oxide

CeO2-MOx (M=Cu, Mn, Fe, Co, and Ni) mixed oxide catalysts were prepared by a citric acid complexation-combustion method. CeO2-MOx solid solutions could be formed with M cations doping into CeO2 lattice, while NiO and Co3O4 phases were detected on the surface of CeO2-NiO and CeO2-Co3O4 by Raman spectroscopy. The presence of M in CeO2 could obviously promote its catalytic activity for CH4 catalytic combustion and CO oxidation. Among the prepared samples, CeO2-CuO exhibited the best performance for CO oxidatio...     

Synthesis and characterization of mesostructured ceria-zirconia solid solution

Mesostructured Ce0.6Zr0.4O2 solid solutions were synthesized by coprecipitation combined with evaporation-induced self-assembly process. The obtained materials were characterized by X-ray diffractometer (XRD), Raman, transmission electron microscopy (TEM), N2 sorption, and hydrogen temperature programmed reduction (H2-TPR). The results showed that the solid solutions consisted of uniform nanocrystals, which piled homogeneous mesopores of about 4 nm. Furthermore, different surfactants had little influence on the mesoporous structures. All these samples exhibited high thermal stability.     

培养优秀拔尖人才的实践与思考

本文论述了理工优秀生部作为培养优秀拔尖人才,在实施素质教育、贯彻因材施教、尊重个性发展、培养创新精神方面作的一些有益的探索与实践.     

高温稳定的Al2O3基复合氧化物的制备与性能

采用反相微乳液法制备了在高温条件下结构稳定的Al2O3基复合氧化物.经BET比表面积和XRD测定表明,用本方法制备的Al2O3、钡改性Al2O3、硅改性Al2O3都具有很高的热稳定性,经1100℃焙烧10h后,Al2O3的比表面积为51m2·g-1,钡改性Al2O3的比表面积为90m2g-1,硅改性Al2O3的比表面积为175m2·g-1,远高于用sol-gel法制备的同组成的样品.制备方法不同,所得产物的物相结构和孔径分布也存在较大的差异,用反相微乳液法制备的样品主要以活性Al2O3相存在,粒度分布均匀,为纳米级粒子.钡和硅的存在提高了活性Al2O3的相转变温度,抑制了高温条件下粒子的长大,从而使样品的热稳定性提高.     

Crystal structures and fluorescence properties of lanthanide complexes prepared with 2,2’-biphenyldicarboxylic acid and 2,2’：6’,2’’-terpyridine

Five lanthanide complexes of Ln₂(dpdc)₂(tpy)₂(NO₃)₂(H₂O)₂ [Ln=La (1), Ce (2), Pr (3), Sm (4), Gd (5), H₂dpdc=2,2’-biphenyldicarboxylic acid and tpy=2,2′:6′,2″-terpyridine] were prepared at room temperature and characterized by X-ray diffraction, FT-IR and thermo-gravimetric analysis. The results showed that complexes 1–5 were isostructural and consisted of dinuclear units [Ln₂(dpdc)₂(tpy)₂(NO₃)(H₂O)₂] bridged by two dpdc^2? ligands. The dinuclear units with strong intramolecular hydrogen bonds were assembled into 2D supramolecular layers by the weak π^…π staking interactions between pyridine rings of tpy. The TG analysis showed that the complexes 1–5 behaved higher thermal stability with no mass loss at < 320 °C. The lanthanide contraction effect and the solid state luminescence properties of complexes 1–5 were also investigated. The luminescence emission spectra of complexes 1–5 exhibited ligands emission bands and complex 3 and 4 had no typical emission in the visible region.     

氧化镁改性HZSM-5分子筛的酸性及在合成气直接制二甲醚反应中的应用——镁前驱体的影响

以乙酸镁为前驱体采用浸渍法制备了一系列不同氧化镁(MgO)含量(0%～20%)的镁改性HZSM-5分子筛,并采用X射线衍射(XRD)、N2吸附、X射线光电子能谱(XPS)、氨程序升温脱附(NH3-TPD)和吡啶吸附红外光谱(Py-IR)方法对其结构和酸性进行了表征.在连续流动加压固定床反应器中及温度260℃、压力4 Mpa和气体空速1500 mL·gcat·h)-1条件下,考察了以上述HZSM-5分子筛为甲醇脱水活性组分与铜基甲醇合成活性组分(CuO-ZnO-Al2O3)所组成的双功能催化剂对合成气直接制二甲醚反应的催化性能.结果表明,HZSM-5分子筛经适量的MgO改性后,产物中二甲醚的选择性由49.1%提高到68%以上,而二氧化碳和烃类副产物的选择性则分别由37.1%和9.3%降低到27%和0.1%以下.烃类和二氧化碳副产物减少的原因是MgO改性降低了HZSM-5分子筛强酸中心的酸量,尤其是减少了强Br?nsted酸的酸量.另外,与以硝酸镁为前驱体制备的MgO/HZSM-5不同,MgO在较大的范围(2.5%～20%)内对其催化性能几乎无影响.     

焙烧条件对B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应的影响

考察了催化剂焙烧条件对B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应性能的影响,确定了其最佳的焙烧条件为温度600℃、时间12 h.反应5 h内环己酮肟转化率和己内酰胺选择性的平均值分别高达99.7%和97.0%.采用N2吸附、XRD和NH3-TPD等方法,研究了焙烧温度对B2O3/TiO2-ZrO2催化剂结构和酸性的影响.结果表明,适当提高焙烧温度有利于B2O3与TiO2-ZrO2的相互作用,生成更多的Beckmann重排反应所需的中等强度酸中心,从而使催化剂的活性和选择性增大;但过高的焙烧温度又造成催化剂中大量的B2O3晶粒析出,使比表面积、酸中心数量和催化活性均明显下降.     

固体酸催化合成邻苯二甲酸二辛酯

介绍了工业邻苯二甲酸二辛酯（DOP）的生产现状，分析了国内生产技术特点与存在问题，综述了采用固体酸催化剂合成DOP的新进展。