共查询到20条相似文献,搜索用时 0 毫秒
1.
Imtiaz Ahmad Mohammad Arsala Khan Mohammad Shakirullah Mohammad Ishaq Rashid Ahmad Habib‐ur‐Rehman 《中国化学会会志》2004,51(4):723-727
A Pakistani coal was de‐polymerized/liquefied in toluene in a 1000 mL micro autoclave. Experiments have been performed in a pool of hydrogen under varying operating conditions of temperature, residence time, hydrogen pressure (cold), coal/solvent ratio and coal particle size. A pronounced effect of all these process variables has been noted on the yields of liquefied products, i.e., THF solubles, n‐pentane solubles, and n‐pentane insolubles. Extraction temperature of 450 °C, residence time of 1 hour, hydrogen pressure of 30 kgf/cm2, coal/solvent ratio of 1:2 and coal particle size of 53–45 μm were found optimum for maximum conversion of Pakistani coal into liquefied products. 相似文献
2.
Depolymerization of an indigenous coal was studied in a variety of solvents at a temperature of 400 ± 10 °C in a hydrogen environment using a micro autoclave reactor for a time duration of 30 minutes. Some aliphatic, aromatic solvents as well as viscous petroleum based oils and pitches were used for evaluating them as liquefaction solvents. Amongst aliphatic solvents, 2‐propanol, and amongst aromatics, p‐creosol, gave highest yields. Petroleum pitches also proved effective, particularly their blends which caused significant depolymerization of the coal under study leading to formation of liquid products. 相似文献
3.
In this paper, nichrome was adopted as a substrate, to fabricate the pre‐anodized inlaying ultrathin carbon paste electrode (PAIUCPE). The electrochemical behaviors and diffusion mechanisms of three dihydroxybenzene isomers at the electrode were carefully investigated. The effect of pH on oxidation peak current was also detailedly explained. The results were shown that oxidation peak current not only related to the reaction of electroactive materials at the working electrode, but also depended on the reaction variable of reduction at the auxiliary electrode. The oxidation peaks of hydroquinone (HQ), catechol (CC) and resorcinol (RC) located at 0.181 V, 0.288 V and 0.736 V. For CC, RC and HQ, the oxidation peak currents were linear to the concentrations at the range of 5.0 × 10?6~5.0 × 10?4 mol/L, 3.0 × 10?6~5.0 × 10?4 mol/L and 4.0 × 10?6~4.0 × 10?4 mol/L with the detection limits of 2.0 × 10?7 mol/L, 1.2 × 10?7 mol/L and 1.2 × 10?7 mol/L, respectively. The proposed method was successfully applied in the simultaneous determination of dihydroxybenzene isomers in artificial sewage samples with satisfactory results. 相似文献
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Complexes of Uranyl Nitrate with 2,6‐Pyridinedicarboxamides: Synthesis,Crystal Structure,and DFT Study 下载免费PDF全文
Mikhail Alyapyshev Vasiliy Babain Lyudmila Tkachenko Vladislav Gurzhiy Andrey Zolotarev Yuriy Ustynyuk Igor Gloriozov Alexander Lumpov Dmitriy Dar'in Alena Paulenova 《无机化学与普通化学杂志》2017,643(9):585-592
Two complexes of uranyl nitrate with N,N,N′,N′‐tetrabutyl‐2,6‐pyridinedicarboxamide (TBuDPA) and N,N′‐diethyl‐N,N′‐diphenyl‐2,6‐pyridinedicarboxamide (EtPhDPA) were synthesized and studied. The complex of tetraalkyl‐2,6‐pyridinedicarboxamide with metal nitrate was synthesized for the first time. XRD analysis revealed the different type of complexation: a 1:1 metal:ligand complex for EtPhDPA and complex with polymeric structure for TBuDPA. The quantum chemical calculations (DFT) confirm that both ligands form the most stable complexes that match the minimal values pre‐organization energy of the ligands. 相似文献
6.
Kun Qian Tao Tang Tianyu Shi Pingliang Li Jianqiang Li Yongsong Cao 《Journal of separation science》2009,32(14):2394-2400
A new method for glyphosate residue determination in apple has been developed. A SPE cartridge was used to clean up the samples before derivatization. Glyphosate was derivatized with 4‐chloro‐3,5‐dinitrobenzotrifluoride (CNBF) and quantified by reverse ion‐pair liquid chromatography using cetyltrimethylammonium bromide (CTAB) as ion‐pair reagent. In pH 9.5 H3BO3–Na2B4O7 medium, the reaction of glyphosate with CNBF was complete after 30 min at 60°C. The stability of the derivative on exposure to light at room temperature in methanol–water was demonstrated. The labeled glyphosate was separated on a Kromasil C18 column (250×4.6 mm, 5 μm) at room temperature and UV detection was applied at 360 nm. Separation was achieved within 15 min in gradient elution mode. The correlation coefficient for the method was 0.9998 at concentrations ranging from 0.1 to 50 μg/g. The calculated recoveries for glyphosate in apple were from 86.00 to 99.55%, and the relative standard deviations (n = 6) were from 1.43 to 6.32. The limit of detection was 0.01 μg/g for glyphosate in apple. 相似文献
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Lin‐Wen Lee Shih‐Ming Chen Chiung‐Chang Lin Shiow‐Yunn Sheu Pen‐Yuan Lin 《中国化学会会志》2010,57(6):1232-1236
Glycosides, steviolside, and rubaudioside A, which are extracted from the leaves of Stevia rebaudiana, can be used as sweetener for food additive. Intermediates of steviolbioside, steviol, and isosteviol are very stable compounds obtained from benzotriazol‐1‐yloxtri(pyrrolidinol)phosphonium hexafluorophosphate. They are suitable to be used in amide and amide dimer synthesis. These nature product intermediates possess special characteristics. The spectra data showed two tautomeric groups: an ester form and an amide form. Their nuclear magnetic resonance, mass and chromatographic/mass/mass spectra were examined. 相似文献
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Ting Huang Chao Wang Xinping Zhang Chen Wang Dr. Ailing Li Prof. Dr. Dong Qiu 《化学:亚洲杂志》2015,10(3):759-763
A novel method was developed to synthesize organic–inorganic hybrid hollow sub‐microspheres (HHSs) through the addition of colloidal SiO2. The hydrolysis rate of 3‐(methacryloyloxy)propyltrimethoxysilane (MPS) was accelerated by SiO2 particles; meanwhile, the condensation rate of the hydrolytic species was decelerated. Thus, the hydrolytic monomers and oligomers of MPS were preserved as emulsifiers. These emulsifiers can then emulsify the isopentyl acetate (PEA) to form a steady O/W emulsion. The HHSs were produced by subsequent free radical polymerization and removal of the oil core. The hydrolytic MPS acted as emulsifiers and polymerizable monomers at the emulsification and polymerization stage, respectively. Thus, extra emulsifiers, co‐emulsifiers, and organic monomers were omitted, which simplified the synthesis process. The good dispersion of HHSs in water and oil, as well as the EDX results, indicated the organic–inorganic hybrid structure of HHSs. 相似文献
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Cooperative,Reversible Self‐Assembly of Covalently Pre‐Linked Proteins into Giant Fibrous Structures
Saadyah Averick Orsolya Karcsony Jacob Mohin Xin Yong Nicholas M. Moellers Bradley F. Woodman Weipu Zhu Ryan A. Mehl Anna C. Balazs Tomasz Kowalewski Krzysztof Matyjaszewski 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(31):8188-8193
We demonstrate a simple bioconjugate polymer system that undergoes reversible self‐assembling into extended fibrous structures, reminiscent of those observed in living systems. It is comprised of green fluorescent protein (GFP) molecules linked into linear oligomeric strands through click step growth polymerization with dialkyne poly(ethylene oxide) (PEO). Confocal microscopy, atomic force microscopy, and dynamic light scattering revealed that such strands form high persistence length fibers, with lengths reaching tens of micrometers, and uniform, sub‐100 nm widths. We ascribe this remarkable and robust form of self‐assembly to the cooperativity arising from the known tendency of GFP molecules to dimerize through localized hydrophobic patches and from their covalent pre‐linking with flexible PEO. Dissipative particle dynamics simulations of a coarse‐grained model of the system revealed its tendency to form elongated fibrous aggregates, suggesting the general nature of this mode of self‐assembly. 相似文献
10.
Microsecond X‐ray Absorption Spectroscopy Identification of CoI Intermediates in Cobaloxime‐Catalyzed Hydrogen Evolution 下载免费PDF全文
Dr. Grigory Smolentsev Bianca Cecconi Alexander Guda Dr. Murielle Chavarot‐Kerlidou Prof. Jeroen A. van Bokhoven Dr. Maarten Nachtegaal Dr. Vincent Artero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15158-15162
Rational development of efficient photocatalytic systems for hydrogen production requires understanding the catalytic mechanism and detailed information about the structure of intermediates in the catalytic cycle. We demonstrate how time‐resolved X‐ray absorption spectroscopy in the microsecond time range can be used to identify such intermediates and to determine their local geometric structure. This method was used to obtain the solution structure of the CoI intermediate of cobaloxime, which is a non‐noble metal catalyst for solar hydrogen production from water. Distances between cobalt and the nearest ligands including two solvent molecules and displacement of the cobalt atom out of plane formed by the planar ligands have been determined. Combining in situ X‐ray absorption and UV/Vis data, we demonstrate how slight modification of the catalyst structure can lead to the formation of a catalytically inactive CoI state under similar conditions. Possible deactivation mechanisms are discussed. 相似文献
11.
Bao‐Chun Liu Shui‐Hua Tang Qi Liang Li‐Zhen Gao Bo‐Lan Zhang Mei‐Zhen Qu Zuo‐Long Yu 《中国化学》2001,19(10):983-986
A technique has been developed to grow carbon nanotubes by flowing acetylene over pre‐reduced LaCoO3 catalyst in a fluidized‐bed catalytic reactor. Carbon nanotubes were characterized by means of SEM and TEM. The pre‐reduced LaCoO3 catalyst was found to be effective in producing carbon nanotubes with even diameter. The effects of reduction temperature of LaCoO3 on the growth of carbon nanotubes were investigated. This process can easily be scaled up. 相似文献
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Yuanpeng Li Sheming Jiang Xunhua Yuan Binkai Chen Qifu Zhang 《Surface and interface analysis : SIA》2012,44(4):472-477
High‐strength dual phase steels readily exhibit bad galvanizability and coating defects because of selective oxides formed on steel surface during the annealing process prior to galvanizing. To investigate selective oxidation of alloying elements and their effects on glavanizability, a high‐strength dual phase steel was annealed with soaking duration for 45, 90, and 120 s, respectively, and then galvanized using a hot‐dip simulator. Field‐emission scanning electron microscopy characterization revealed that when dual phase steel was soaked for 45 s, selective oxides mainly precipitated along grain boundaries, while only a few of the oxides formed on grains. With soaking duration increased, oxides were so dense that nearly all steel surface was covered, leaving little bare area of the steel surface. Further XPS analysis showed that selective oxides mainly consisted of MnO and Cr2O3. In addition, the chemical nature of oxides did not change at all although soaking duration prolonged. Scanning Auger microprobe depth profiles presented that Mn had a much higher tendency to segregate than Cr and Mo. Oxygen penetration depth to subsurface was promoted as soaking duration increased. The formation of interfacial inhibition layer was founded to be greatly influenced by the density and size of surface oxides. The widely spaced small oxides had virtually no adverse effect on wettability because of aluminothermic reduction of oxides by the bath dissolved Al. As the oxides became dense and considerably big, the grains of the inhibition layer in some certain zones became coarse and the galvanizability tended to deteriorate. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
14.
Cooperative,Reversible Self‐Assembly of Covalently Pre‐Linked Proteins into Giant Fibrous Structures 下载免费PDF全文
Saadyah Averick Orsolya Karácsony Jacob Mohin Dr. Xin Yong Nicholas M. Moellers Bradley F. Woodman Prof. Weipu Zhu Prof. Ryan A. Mehl Prof. Anna C. Balazs Prof. Tomasz Kowalewski Prof. Krzysztof Matyjaszewski 《Angewandte Chemie (International ed. in English)》2014,53(31):8050-8055
We demonstrate a simple bioconjugate polymer system that undergoes reversible self‐assembling into extended fibrous structures, reminiscent of those observed in living systems. It is comprised of green fluorescent protein (GFP) molecules linked into linear oligomeric strands through click step growth polymerization with dialkyne poly(ethylene oxide) (PEO). Confocal microscopy, atomic force microscopy, and dynamic light scattering revealed that such strands form high persistence length fibers, with lengths reaching tens of micrometers, and uniform, sub‐100 nm widths. We ascribe this remarkable and robust form of self‐assembly to the cooperativity arising from the known tendency of GFP molecules to dimerize through localized hydrophobic patches and from their covalent pre‐linking with flexible PEO. Dissipative particle dynamics simulations of a coarse‐grained model of the system revealed its tendency to form elongated fibrous aggregates, suggesting the general nature of this mode of self‐assembly. 相似文献
15.
Silica gel-loaded (E)-N-(1-thien-2'-ylethylidene)-1,2-phenylenediamine (TEPDA) phase was synthesized based on physical adsorption approaches. The stability of a chemically modified TEPDA especially in concentrated hydrochloric acid that was then used as a recycling and preconcentration reagent allowed the further uses of silica gel-loaded immobilized TEPDA phase. The application of this silica gel-loaded phase to sorption of a series of metal ions was performed by using different controlling factors such as the pH of the metal ion solution and the equilibration shaking time by the static technique. This difference was interpreted on the basis of selectivity incorporated in these sulfur containing silica gel-loaded TEPDA phases. Hg(Ⅱ) was found to exhibit the highest affinity towards extraction by these silica gel-loaded TEPDA phases. The pronounced selectivity was also confirmed by the determined distribution coefficients (Kd) of all the metal ions, showing the highest value reported for mercury(Ⅱ) extraction by the silica gel immobilized TEPDA phase. The potential applications of the silica gel immobilized TEPDA phase to selective extraction of mercury(Ⅱ) from aqueous solution were successfully accomplished and preconcentration of low concentration of Hg(Ⅱ) (30 pg·mL^-1) from natural tap water with a preconcentration factor of 200 for Hg(Ⅱ) off-line analysis was conducted by cold vapor atomic absorption analysis. 相似文献
16.
Influence of multiple processing on selected properties of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) 下载免费PDF全文
Krzysztof Moraczewski 《先进技术聚合物》2016,27(6):733-739
The effect of multiple (up to 10 times) injection molding of processed poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3,4HB)) on its phase transition temperatures, degree of crystallinity, degradation temperature, mass flow rate, mechanical properties, dynamic mechanical properties, and Charpy's impact strength is presented. The studies have shown that the multiple injection lowers the degree of crystallinity and the thermal stability of P(3,4HB). The mass flow rate values increased with increasing the injection number. It was found that the multiple injections had no substantial effect on the tensile strength up to 10 injection cycles and the tensile strength at break, tensile strain at tensile strength, and tensile strain at break up to 6 injection cycles. The maximum value of storage modulus at 30 °C and impact strength were recorded for sample after 4 cycles of injection, while the values of storage modulus at 120 °C increased with increase of the injection cycles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
Farhat Waqar Saida Jan Bashir Mohammad Muhammad Hakim Shah Alam Wasim Yawar 《中国化学会会志》2009,56(2):335-340
An analytical method has been developed for the preconcentration of rare earth elements (REEs) in seawater for their determination by inductively coupled plasma optical emission spectrometry (ICP‐OES). An indigenously synthesized chelating resin was used for the preconcentration of (REEs) which was based on immobilization of fluorinated β‐diketone group on solid support styrene divinyl benzene. Sample solutions (adjusted to optimized pH) were passed through a polyethylene column packed with 250 mg of the resin. Experimental conditions consisting of pH, sample flow rate, sample volume and eluent concentration were optimized. The established method has been applied for the preconcentration of light, medium and heavy REEs in coastal sea water samples for their subsequent determination by (ICP‐OES). Percentage recoveries of La, Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb and Lu were ≥ 95%, a preconcentration factor of 200 times, and relative standard deviations < 5% were achieved. 相似文献
18.
《Journal of separation science》2002,25(18):1346-1350
The analysis of alcohol dehydrogenase (ADH) at low concentration using capillary electrophoresis is described. Several simple and effective ways to improve detection limits and sensitivity are investigated. These include large volume sample stacking, head column field amplified sample stacking, and sweeping. Results indicate that by using a combination of head‐column field amplified sample stacking and sweeping, fluorescently labelled alcohol dehydrogenase can be pre‐concentrated online by dissolving samples in water or other low conductivity matrices, and injecting into a high conductivity micellar buffer. The abrupt changes in conductivity cause narrowing of the analyte length and thus enhance the detection sensitivity. Combination of this approach with laser induced fluorescence detection yields a limit of detection of 5×10–13 M. Both qualitative and quantitative aspects of this method are investigated. 相似文献
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Jinzhen Zhang Jing Zhao Jinhui Zhou Xiaofeng Xue Yi Li Liming Wu Fang Chen 《中国化学》2011,29(8):1764-1768
Amantadine (AMA) is an anti‐viral drug used in apiculture to protect honeybee against the sacbrood virus (Morator aetatulae). This study described a reliable high‐performance liquid chromatographic (HPLC) method for analyzing AMA in honey using a solid‐phase extraction (SPE) cartridge (Plexa PCX) for purification, 4‐fluoro‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐F) as a pre‐column derivatization agent, and fluorometric detection (λex=470 nm, λem=530 nm). The chromatographic separation was performed on an XDB C18 column (150×4.6 mm i.d.) using 0.1% trifluoroacetic acid/acetonitrile (35:65,V/V) as the mobile phase at a flow rate of 1.0 mL·min−1 with a run time of 20 min. Under these optimal conditions, a linear relationship was observed in the range of 0.025–1.0 µg· mL−1 with a good correlation coefficient (0.998) and low limit of detection (0.0080 µg·g−1), the recoveries were all above 90%, and the intra‐day and inter‐day precision (RSD) ranged from 3.4%–5.1%. 相似文献