硫化对聚乙炔结构和性能的影响

本文利用DSC, FT-IR光谱对聚乙炔硫化产物进行了表征, 研究了聚乙炔硫化前后结构和性能的变化。采用量子化学CNDO/2晶体轨道方法, 首次对硫化聚乙炔的分子结构及电子性质进行理论计算, 探讨了硫化对聚乙炔结构和性能的影响。     

碳纤维复合聚乙炔膜合成及其p-型电池的性能

聚乙炔(PA)膜作为电极材料实用化的主要困难在于稳定性较差.虽然对这一问题进行了不少研究,但至今成效不大.我们从提高聚乙炔膜的强度、导电性及整体电流分布出发,用冷等离子体方法首次合成了碳纤维复合聚乙炔膜.结构分析结果表明,在复合膜中碳纤维和聚乙炔形成了一定程度的接枝,其空气和热稳定性均高于纯PA膜.用这种膜构成的p-型电池具有较高的化学掺杂度,各项电性能均有所提高.     

聚乙炔顺、反式结构对硫化聚乙炔的稳定性及其电子性质的影响

采用量子化学一维紧束缚的LCAO-SCF-MO法,讨论了顺、反式聚乙炔经硫化得到的硫化聚乙炔的稳定性以及电子性质的变化规律,揭示了顺反结构对其性质影响的原因.计算结果表明,聚乙炔最佳结构为反式,硫化聚乙炔的反式结构更加稳定,这与我们的实验结果一致,为进一步的实验合成提供了理论依据.     

单元轨道线性组合近似理论——端基官能团对聚乙炔体系电子结构的影响

采用单元轨道线性组合近似方法对不同端基官能团的聚乙炔体系作了量子化学计算,结果表明卤素对聚乙炔能带结构影响很小,含有氧、氮的官能团(羧基、醛基和硝基)对聚乙炔能带结构有强烈的类似掺杂作用的影响。     

稀土聚乙炔电化学

本文研究了稀土聚乙炔在水溶液中进行电化学掺杂和化学掺杂,及稀土聚乙炔的电位;用掺杂后的稀土聚乙炔作为水溶液体系一次电池的阴极,以镁作阳极构成半塑料电池;并研究了以稀土聚乙炔作为有机电解质体系可再充式电池的阴极,以锂作阳极的化学电源的电性能。     

可溶性稀土聚乙炔的某些结构特征

本文利用UV、IR、Ramaan、ESR和X射线衍射等方法研究了可溶性聚乙炔的某些结构特征。发现非结晶的可溶性聚乙炔的光谱和波谱性质与结晶的膜状及粉末状聚乙炔有明显的差异,可能是由于它们的分子量相差悬殊造成的。实验结果表明,线型聚乙炔可能存在可溶的临界分子量,其值在=500 左右。     

硫化聚乙炔结构对其电子性能的影响

本文用硫原子和共轭多烯的复合物模拟硫化聚乙炔结构, 并采用一维紧束缚的LCAO-SCF-MO法, 探讨了硫化聚乙炔结构对其电子性能的影响, 揭示出影响的原因, 确定了最佳结构, 为实验合成提供了理论依据。     

氧化和硫化对聚乙炔导电性能的影响

本文采用量子化学CNDO/2晶体轨道方法,对硫化聚乙炔和氧化聚乙炔的分子结构及电子质进行了了理论计算和分析,探讨了氧化和硫化对聚乙炔导电性能的影响,揭示了硫化抑制聚乙炔氧化,从而在空气中稳定的本质。     

硫化聚乙炔结构对其电子性能的影响

本文用硫原子和共轭多烯的复合物模拟硫化聚乙炔结构,并采用一维紧束缚的LCAO-SCF-MO法,探讨了硫化聚乙炔结构对其电子性能的影响,揭示出影响的原因,确定了最佳结构,为实验合成提供了理论依据。     

聚乙炔热氧化过程的研究

本文测定了聚乙炔在氮气、空气和氧气中的等速升温热重曲线,测定了不同聚乙炔样品热氧化的恒温热重曲线,比较了聚合体系和顺反结构等对热氧化行为的影响。观察到钕催化聚乙炔的热氧化诱导现象。动力学分析表明,氧化反应对聚乙炔和氧气浓度都接近表观一级反应,顺式聚乙炔的表观活化能为42±6ki/mol,反式聚乙炔为51±6kJ/mol。用红外光谱跟踪氧化过程,表明含氧基团可分两类,分属于中间和最终产物,由此推断了可能的氧化反应。     

Ln（acac）3—BuMgCl催化甲基丙烯酸甲酯聚合

开发了催化甲基丙烯酸甲酯聚合的一类新型催化剂，由稀土乙酰基丙酮配合物Ｌｎ（ａｃａｃ）３和格氏试剂ＢｕＭｇＣｌ组成．研究了不同稀土元素、催化剂陈化时间和温度、溶剂、ＣＣｌ４添加剂、聚合时间和温度的影响．结果表明，在石油醚中单体聚合转化率和聚合物相对分子质量高于芳烃和其它极性溶剂，过量ＢｕＭｇＣｌ可能起链转移作用，降低温度可提高聚合物的间同含量．     

Vanadium-based Ziegler-Natta catalyst supported on MgCl2(THF)2 for ethylene polymerization

A supported magnesium-vanadium-aluminium catalyst was prepared by depositing –with the use of a milling technique–VOCl₃ on the MgCl₂(THF)₂ support and subsequent activation with diethylaluminium chloride. Catalytic activity of the obtained system for ethylene polymerization was evaluated as a function of Mg/V and Al/V ratios as well as catalyst ageing time and polymerization temperature. High concentrations of THF in the catalytic system and considerable excess of an organoaluminium co-catalyst were found to have no deactivating action on vanadium active sites. The catalyst obtained is stable and its activity for ethylene polymerization is high. It yields polyethylene with higher molecular weight and higher melting point than offered by the materials produced with the use of a corresponding unsupported vanadium catalyst or a titanium-based system on the same magnesium support. Kinetic investigations confirmed stability of this catalyst irrespective of its concentration in the polymerization medium or of monomer concentration. Moreover, analysis of the kinetic findings revealed that over 80% of vanadium employed forms active polymerization sites.     

Polymerization of 4-phenyl-1-butyne catalyzed by metathesis and Ziegler–Natta catalysts

The polymerization of 4-phenyl-1-butyne was carried out using metathesis and Ziegler-Natta catalysts. Especially, the Fe(acac)₃-AlEt₃ catalyst with toluene as a solvent produced an extremely high molecular weight polymer of M_w ≈ 10⁶. Solubility of the polymers at room temperature in organic solvents such as benzene, toluene, dichloromethane, chloroform, and THF was excellent despite their high molecular weights. It has been indicated that the polymer prepared by the Fe(acac)₃-AlEt₃ catalyst is of cis form with a high stereoregularity. © 1993 John Wiley & Sons, Inc.     

Gas Phase Selective Catalytic Oxidation of Toluene to Benzaldehyde on V2O5-Ag2O／η-Al2O3 Catalyst

Gas phase selective catalytic oxidation of toluene to benzaldehyde was studied on V2O5-Ag2O/η-Al2O3 catalyst prepared by impregnation. The catalyst was characterized by XRD, XPS, TEM,and FT-IR. The catalytic results showed that toluene conversion and selectivity for benzaldehyde on catalyst sample No.4 (V/(V Ag)=0.68) was higher than other catalysts with different V/Ag ratios. This was attributed to the higher surface area, larger pore volume and pore diameter of the catalyst sample No.4 than the other catalysts. The XRD patterns recorded from the catalyst before and after the oxidation reaction revealed that the new phases were developed, and this suggested that silver had entered the vanadium lattice. XPS results showed that the vanadium on the surface of No.4 and No.5 sample was more than that in the bulk, thus forming a vanadium rich layer on the surface. It was noted that when the catalyst was doped by potassium promoter, the toluene conversion and selectivity for benzalde hydewere higher than those on the undoped catalyst. This was attributed to the disordered structure of V2O5 lattice of the K-doped catalyst and a better interfacial contact between the particles.     

V（acac）3—AI（i—BU）2CI催化体系相态的研究

研究了V(acac)3-AI(i-BU)2CI催化体系的相态。通过Tyndall效应、电镜观察和超过渡实验,证明了在溶有丁二烯的甲苯溶剂中V(acac)3-AI(i-BU)2CI催化体系以小颗粒分散,粒径在1－100nm之间,为胶体催化剂,属于高度分散的多相催化体系。催化剂颗粒是无定形的,其活性中心位于胶粒表面,以较佳配比所得到的催化剂颗粒较小、分布均匀,对丁二烯聚合反应具有较高的催化活性。     

Synthesis of a telechelic polypropylene with a vanadium-based living polymerization catalyst

The V(acac)₃ (acac = acetylacetonato)/AlEt₂Cl catalyst is known to promote the living polymerization of propylene at low temperature. In the present study, the catalyst was modified by contacting with α,ω-unconjugated diene compounds, and the resulting catalyst was applied to propylene polymerization. The polymer produced shows a bimodal molar mass distribution, where the molecular weight of the higher molecular weight portion is twice that of the lower molecular weight portion. By using the CO quenching technique, it was found that the polymer with the higher molecular weight has a telechelic structure.     

Gas Phase Selective Catalytic Oxidation of Toluene to Benzaldehyde on V2O5-Ag2O/η-Al2O3 Catalyst

Gas phase selective catalytic oxidation of toluene to benzaldehyde was studied on V2O5-Ag2O/η-Al2O3 catalyst prepared by impregnation. The catalyst was characterized by XRD, XPS, TEM,and FT-IR. The catalytic results showed that toluene conversion and selectivity for benzaldehyde on catalyst sample No.4 (V/(V Ag)=0.68) was higher than other catalysts with different V/Ag ratios. This was attributed to the higher surface area, larger pore volume and pore diameter of the catalyst sample No.4 than the other catalysts. The XRD patterns recorded from the catalyst before and after the oxidation reaction revealed that the new phases were developed, and this suggested that silver had entered the vanadium lattice. XPS results showed that the vanadium on the surface of No.4 and No.5 sample was more than that in the bulk, thus forming a vanadium rich layer on the surface. It was noted that when the catalyst was doped by potassium promoter, the toluene conversion and selectivity for benzaldehyde were higher than those on the undoped catalyst. This was attributed to the disordered structure of V2O5 lattice of the K-doped catalyst and a better interfacial contact between the particles.     

钒基催化剂在双氧水存在下对甲、乙苯液相选择氧化的研究

研究了若干钒基催化剂在双氧水存在下对甲、乙苯的液相选择性氧化催化性能.结果表明:在乙腈为溶剂的反应体系中,所研究的钒基催化剂包括VPO,VOPO₄,V₂O₅,VO(acac)₂和NH₄VO₃等均表现出以苯甲醛为甲苯选择性氧化主产物和以苯乙酮为乙苯选择氧化主产物的反应结果;从反应活性和主产物选择性来看,按以下顺序递减:VPO＞V₂O₅＞VOPO₄＞VO(acac)₂＞NH₄VO₃.对于具有(VO)₂P₂O₇晶相的VPO催化剂,在双氧水存在下对甲苯选择性氧化主产物苯甲醛的最高选择性为58.8%,乙苯选择性氧化主产物苯乙酮的最高选择性为67.8%;其催化性能与P/V比、焙烧条件、双氧水的使用量、反应溶剂等有关.从已有的实验结果推测,钒基催化剂在双氧水存在下的甲、乙苯选择氧化反应与V⁵⁺/V⁴⁺的"氧化-还原"作用密切相关.     

Polymerization of ethylene at high temperature by vanadium-based heterogeneous Ziegler–Natta catalysts. I. Study of the deactivation process

Kinetics of the polymerization of ethylene initiated by heterogeneous vanadium-based Ziegler-Natta catalysts (VCI₃-1/3 AICI₃) have been studied at high temperature (160°C, 5 bars) and compared with a titanium-based system. For the V catalyst, the dependence of the polymerization activity versus time, with the nature and the concentration of the associated aluminum alkyl, has been investigated. Kinetic results have also been correlated with the oxidation state of vanadium in the polymerization conditions. Despite the relatively high initial activity a low productivity is obtained; it can be attributed to a very fast deactivation of the active sites due to the reduction of vanadium III into vanadium II. The effect of the nature of the alkyl aluminum component of the catalytic system on the reduction process is shown. A kinetic model for the polymerization is proposed. © 1993 John Wiley & Sons, Inc.     

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300 ?C) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ?C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4+ and Pd2+ species on the surface, which might be favorable for the formation of active sites.