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831.
Guangdong Zhou Tiexin Cheng Wenxing Li Yingli Bi Kaiji Zhen 《Reaction Kinetics and Catalysis Letters》2003,79(2):295-302
Polyaniline(PAN) supported H6P2W18O62(PW) , H3PMo12O40 (PMo) and H4PMo11VO40(PMoV) catalysts were prepared and their activities for hexanol conversion were tested. IR, XRD, ICP and SEM measurements
proved that the heteropolyacids (HPA) could be supported on this type of polymer. The PAN supported HPA catalysts exhibit
higher redox activities and low acid-base activities for the hexanol conversion. The redox activities increase with increasing
amount of the heteropolyacid. Substitution of Mo ion by V ion results in an increase of redox activities of the catalysts.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
832.
1,3-Propanediol (1,3-PD) has numerous applications from polymers to cosmetics, foods, lubricants, and medicines. Recently,
there are strong industrial interests in a new kind of polyester, polytrimethylene terephthalate, with 1,3-PD as a monomer.
This new polyester shows significant promise for use in carpeting and textiles. In this article we introduce a mild aerobic
fermentation process using a strain screened from Klebsiella pneumoniae ATCC 25955, which is insensitive to oxygen, to produce 1,3-PD. We also describe a two-step fermentation process starting
with glucose that was converted into glycerol with a glycerol-producing yeast, followed by K. pneumoniae that converts glycerol into 1,3-PD without intermediate isolation and purification of glycerol. 相似文献
833.
Chun‐Bo Liu Guang‐Bo Che Chuan‐Bi Li Yun‐Cheng Cui 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(4):m153-m155
An in situ reaction under hydrothermal conditions leads to the formation of the title compound, diaqua(pyridine‐2‐carboxylato)(pyridine‐2,6‐dicarboxylato)indium(II) trihydrate, [In(C6H4NO2)(C7H3NO4)(H2O)2]·3H2O, in which the central InIII atom is seven‐coordinated by one pyridine‐2,6‐dicarboxylate ligand, one pyridine‐2‐carboxylate ligand and two water molecules in a pentagonal–bipyramidal coordination environment. An indium(III)–water chain based on an unusual water pentamer is observed. 相似文献
834.
Guangdong Zhou Zhanlin Xu Xiaohong Guo Hong Zhuang Yanan Li Xueju Lü Tiexin Cheng Wenxing Li Kaiji Zhen 《Reaction Kinetics and Catalysis Letters》2005,85(1):57-64
Summary The oxidation of hexanol in the presence of the Keggin-type heteropoly compounds (HPCs) H3PMonW12-nO40 (denoted as PMonW12-n, n=0,1) and Na5PW11ZO39 (denoted as PW11Z, Z = Mn, Fe, Co, Ni, Cu and Zn) was carried out to produce hexanal and hexanoic acid. The reaction was conducted in tert-butanol (t-BuOH), using cetylpyridinium bromide (CPB) salts of HPA and 15% aqueous H2O2 as oxidant under mild condition. The PMoW11 catalyst showed higher hexanol conversion of 25%, the lowest selectivity to hexanal of 64.4% and an efficient utilization of H2O2 of 34%. Over the transition metal substituted PW11Z catalysts decomposition of H2O2 was rapid. For these PW11Z catalysts, the efficient utilization of H2O2 decreased to 9% or even lower. By means of IR, UV-visible and GC-MS techniques the catalysts were characterized. 相似文献
835.
Xiao-bing Zhang Ben-chen Tang Peng Zhang Min Li Wen-jing Tian 《Journal of Molecular Structure》2007,846(1-3):55-64
The synthesis, optical properties, electrochemical properties, electronic structures and applications in electroluminescent device of three series of 1,3,4-oxadiazole derivatives, 1,4-bis[(4-methylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD1), 5,5′-di-(4-methyl)-2,2′-p-(2,5-bisalkoxyphenylene)-bis-1,3,4-oxadiazole (OXD2–n) and 1,4-bis[(4-alkoxyphenyl)-1,3,4-oxadiazolyl]phenylene (OXD3–n) are reported. The molecular structures of the oxadiazole compounds were confirmed by FT-IR, 1H NMR spectroscopy and elemental analysis. The optical and electrochemical properties of the compounds were investigated by UV–vis absorption and photoluminescence spectroscopy as well as cyclic voltammetry. The results show that introduction of two alkoxy groups whose electron-donating ability is stronger than that of methyl groups increases the electron density of the conjugated segment of OXD2–n (with side-on alkoxy substituents) and OXD3–n (with end-on alkoxy substituents), and thus leads to the absorption maximum bathochromic-shift compared to that of OXD1. The HOMO and LUMO energy levels of the compounds studied are in the range of −2.78 to −2.89 and −5.75 to −6.20 eV. Calculations on the representative compounds by the Dmol3 package of MS Modeling 3.0 revealed that the increase of energy levels in both OXD2–n and OXD3–n was due to the change of the frontier molecular orbital distribution in the central benzene ring. The light-emitting devices have been fabricated using blends of MEH-PPV and these compounds as emissive layers, among which, maximum brightness up to 11810 cd m−2 (8.5 V) has been observed, which is 40 times brighter than that with MEH-PPV. The result of the devices suggested that oxadiazole derivatives studied function well as electron-transporting materials and can be used in LEDs, and thus to enhance the efficiency of LEDs. 相似文献
836.
The influence of the comonomer content in a series of metallocene-based ethylene-1-octene copolymers (m-LLDPE) on thermo-mechanical, rheological, and thermo-oxidative behaviours during melt processing were examined using a range of characterisation techniques. The amount of branching was calculated from 13C NMR and studies using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were employed to determine the effect of short chain branching (SCB, comonomer content) on thermal and mechanical characteristics of the polymer. The effect of melt processing at different temperatures on the thermo-oxidative behaviour of the polymers was investigated by examining the changes in rheological properties, using both melt flow and capillary rheometry, and the evolution of oxidation products during processing using infrared spectroscopy.The results show that the comonomer content and catalyst type greatly affect thermal, mechanical and oxidative behaviour of the polymers. For the metallocene polymer series, it was shown from both DSC and DMA that (i) crystallinity and melting temperatures decreased linearly with comonomer content, (ii) the intensity of the β-transition increased, and (iii) the position of the tan δmax peak corresponding to the α-transition shifted to lower temperatures, with higher comonomer content. In contrast, a corresponding Ziegler polymer containing the same level of SCB as in one of the m-LLDPE polymers, showed different characteristics due to its more heterogeneous nature: higher elongational viscosity, and a double melting peak with broader intensity that occurred at higher temperature (from DSC endotherm) indicating a much broader short chain branch distribution.The thermo-oxidative behaviour of the polymers after melt processing was similarly influenced by the comonomer content. Rheological characteristics and changes in concentrations of carbonyl and the different unsaturated groups, particularly vinyl, vinylidene and trans-vinylene, during processing of m-LLDPE polymers, showed that polymers with lower levels of SCB gave rise to predominantly crosslinking reactions at all processing temperatures. By contrast, chain scission reactions at higher processing temperatures became more favoured in the higher comonomer-containing polymers. Compared to its metallocene analogue, the Ziegler polymer showed a much higher degree of crosslinking at all temperatures because of the high levels of vinyl unsaturation initially present. 相似文献
837.
The influence of Stokes shift in optosensing was discussed. Then, the current status of large Stokes shift-based optosensing was reviewed here. 相似文献
838.
Krasnovsky AA Cheng P Blankenship RE Moore TA Gust D 《Photochemistry and photobiology》1993,57(2):324-330
Measurements of pigment triplet-triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium-free and farnesyl-free analogs. The energies of the pigment triplet states fell in the range 1.29-1.34 eV. The triplet lifetimes in aerobic solutions were 200-250 ns; they increased to 280 +/- 70 microseconds after nitrogen purging in liquid solutions and to 0.7-2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0-2.5) x 10(9) M-1 s-1, which is close to 1/9 of the rate constant for diffusion-controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were 55-75% in air-saturated solutions. Singlet oxygen quenching by ground-state pigment molecules was observed. Quenching was the most efficient for magnesium-containing pigments, kq = (0.31-1.2) x 10(9) M-1 s-1. It is caused mainly by a physical process of singlet oxygen (1O2) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen. 相似文献
839.
Jian Zhun JIANG Wei Hong LI Wei Jin ZHOU Hong Cheng GAO* Jin Guang WU Guang Xian XU Department of Applied Chemistry College of Chemistry Molecular Engineering Peking University Beijing 《中国化学快报》2003,14(4):397-400
During the past decades, there has been a renewed interest in the application of solvent extraction to the recovery of Au (I) from cyanide solutions1,2. Among those various extractants, the amine extractants with the addition of organic phosphorus oxide as cosolvent have been widely investigated3,4. Various diluents and modifiers have been selected to optimize the extraction system so as to increase the loading capacity, improve the selectivity and/or reduce emulsification5. Quaternary amm… 相似文献
840.
合成了硫氰酸铈(Ⅲ)与三缩四乙醇配合物[Ce(C_8H_(18)O_5)(NCS)_3(H_(2)O)].晶体结构分析表明,该配合物晶体属三斜晶系,P(?)空间群.晶胞参数:a=0.8816(3)nm,b=1.0465(2)nm,c=1.2490(2)nm,α=86.46(1)°,β=70.90(2)°,γ=66.37(2)°,ν=0.9943nm~(3),Z=2.D_(计算)=1.769cm~(3),最终偏差因子R=0.049. 相似文献