Influence of ion-exchange and impregnation modification of zeolite X on its catalytic properties in the alkylation of toluene with methanol

The dependence of the activity and selectivity of ion-exchanged forms of zeolite X with incorporated cesium process in alkylation of toluene with methanol in the side chain on the nature of the ion-exchanged cations (Na⁺, Cs⁺, Mg²⁺, Zn²⁺) has been established. It is shown that introduction of Mg²⁺ and Zn²⁺ in combination with Cs₂CO₃ significantly increased the yields of ethylbenzene and styrene in comparison with their yields on alkali forms of zeolite X. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 33–38, January–February, 2006.     

乙酰胺-氯化锌新型离子液体的合成及物化性质

合成了CH3CONH2-ZnCl2体系离子液体;利用红外光谱仪分析了CH3CONH2-ZnCl2离子液体的化学特征,采用步冷曲线法绘制了CH3CONH2-ZnCl2二元体系熔点图,测定了其物化性质.结果表明,CH3CONH2-ZnCl2二元体系的最低熔点为8℃;当CH3CONH2与ZnCl2的摩尔比为3:1时,Zn2+...     

PAH metabolism in the earthworm Eisenia fetida – identification of phase II metabolites of phenanthrene and pyrene

Polycyclic aromatic hydrocarbons (PAHs) are soil contaminants. Because of their high lipophilicity, PAHs are associated with the organic matter in the soil. Transformation of PAHs generates polar metabolites and the interaction with organic matter in the soil changes. The polar PAH metabolites are persistent, highly water-soluble and potentially leachable from the soil; the understanding of transformation of PAHs to polar metabolites in the responsible organisms is of great importance. Here, we present a study of transformation of the PAHs pyrene and phenanthrene, by the common earthworm Eisenia fetida. The study showed that E. fetida in hydroponic culture was able to transform PAHs to conjugated phase II metabolites. We detected phenanthrene and pyrene metabolites with single- and multiple-phase II-conjugated groups. Sulphate conjugates were excreted to experiment water, and glucuronide and glucoside conjugates and metabolites with several hydroxylations and multiple conjugations were detected in worm tissue. The results demonstrate that earthworms are able to transform PAHs to water-soluble phase II metabolites, which can be excreted to the surrounding environment.     

锌-铟合金电极在浓KOH溶液中的电化学行为

应用动电位扫描,恒流放电等电化学方法研究含铟锌电极的电化学行为.用SEM和EDS观察放电后的Zn-In合金电极表面形貌,初步探讨了不同In含量的锌-铟合金电极在浓KOH溶液中电化学行为及其影响因素.结果表明,与纯锌电极相比,Zn-In合金的电极致钝电流增大,达到钝化的时间缩短,从而明显地提高了该电极的电化学活性.     

The Effect of the Modification of Carbon Spheres with ZnCl2 on the Adsorption Properties towards CO2

Zinc chloride and potassium oxalate are often applied as activating agents for carbon materials. In this work, we present the preparation of ZnO/carbon spheres composites using resorcinol-formaldehyde resin as a carbon source in a solvothermal reactor heated with microwaves. Zinc chloride as a zinc oxide source and potassium oxalate as an activating agent were applied. The effect of their addition and preparation conditions on the adsorption properties towards carbon dioxide at 0 °C and 25 °C were investigated. Additionally, for all tested sorbents, the CO₂ sorption tests at 40 °C, carried out utilizing a thermobalance, confirmed the trend of sorption capacity measured at 0 and 25 °C. Furthermore, the sample activated using potassium oxalate and modified using zinc chloride (a carbon-to-zinc ratio equal to 10:1) displayed not only a high CO₂ adsorption capacity (2.69 mmol CO₂/g at 40 °C) but also exhibited a stable performance during the consecutive multicycle adsorption–desorption process.     

Color tuning of up-conversion emission in ytterbium,erbium, aluminum tri-doped zinc oxide crystal by adjusting aluminum concentration

Ytterbium, erbium, aluminum tri-doped zinc oxide crystal was synthesized, which can turn color from red to green up-conversion luminescence through adjusting aluminum content. When the aluminum concentration reached 4?mol%, the color of up-conversion emission first turn from red to green. Meanwhile, the ratio of red to green emission reduced from 25.32 to 0.26, and the coordinates of chromaticity coordinate calculation changes from (0.5749, 0.3378) to (0.2190, 0.7169) with aluminum concentration range from 0 to 4?mol%. The up-conversion emission peaks at 521, 542, and 660?nm of sample originate from the transitions of ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 of erbium ions, respectively. X-ray diffraction patterns perform the better crystallization degree with increasing aluminum concentration. The scanning electron microscopy images show the porous and lamellar structures with different aluminum concentrations. A convenient but effective design to obtain ytterbium, erbium, aluminum tri-doped zinc oxide up-conversion luminescence is reported, which can turn color from red to green.     

Photo- and cathodoluminescence of the cetylpyridinium chloride: ZnO nanocomposites

The cathodoluminescence and photoluminescence (PL) spectra of ZnO nanoparticles (NPs) embedded into the cetylpyridinium chloride (CPCL) matrix were studied. The composites were obtained by drying an aqueous suspension of CPCL and ZnO NPs, with NaCl and with NaOH additives. We observed that only NaOH addition lead to a significant increase in the PL intensity which we attribute to the surface chemistry of the ZnO NPs. We propose that thin ZnOH₂ and Na₂ZnO₂ layers form on the surface of the NPs; these layers present an increased number of oxygen vacancies, which act as emitting centres.     

Polymer-filler interaction and control of structure in barium sulphate-filled blends of polypropylene

The structure of barium sulphate-filled immiscible blends with a polypropylene (PP) matrix can be controlled with respect to the occlusion of the filler with the aid of maleic anhydride-grafted polypropylene (PP-g-MAH) through the formation of an interlayer around the filler particles. Here we analyze the interlayer and the mechanism of interlayer formation in a blend with a poly(methylmethacrylate) (PMMA) dispersed phase and compare the results with previous studies, which concerned PP blends with polystyrene (PS) and poly(styrene-co-acrylonitrile) (SAN) minority phases. The main analytical tools were scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and Fourier Transform Infrared Spectroscopy (FTIR). The filler is occluded in the PMMA polymer in the PP/PMMA/BaSO₄ (60/20/20 vol.%) blend, but is occluded in the PP phase at the addition of a sufficient amount of PPg-MAH. The reason for the formation of the latter structure is a PP-g-MAH layer surrounding the filler particles, and the most likely mechanism behind this phenomenon is judged to be specific weak interactions between carbonyl groups in the graft copolymer and Ba²⁺ ions at the filler surface.     

An improved method for assay of vitamin C in fish feed and tissues

Summary A method was devised to assay four forms of vitamin C: L-ascorbic acid (AA), dehydroascorbic acid (DHA), ascorbate-2-mono- and polyphosphate (AMP, APP), as well as ascorbate-2-monosulphate (AMS), in sample series of different fish tissues and feed. Direct and indirect detection were combined. Sample extractions were carried out with 0.2 mol L⁻¹ sodium acetate buffer (pH 4.8) and extracts were deproteinized after different chemical or enzymatic reactions, with perchloric acid. The DHA was reduced to AA with dithioerythritol (DTE). Ascorbate oxidase enzyme was used for the detection of background and an acidic phosphatase enzyme for the hydrolysis of different phosphate esters. Ascorbate-2-sulphate was detected directly with help of coinjection of the compound. Chromatographic analysis was carried out with a single column isocratic reverse phase method. The mobile phase was an aqueous buffer of 0.04 M sodium-acetate, 0.05 mM EDTA, 0.5 mM tetrabutylammonium dihydrogen phosphate (TBA) adjusted to pH 3.76 with 85% H₃PO₄ and with 24 mL methanol added to 1000 mL. C-18 columns were used with 0.6 mL min⁻¹ flow rate at 23°C. The vitamin C forms were detected by UV absorption at 250 nm. The determination limit was 1.0–5.0 μg g⁻¹ in AA equivalent. The standard deviations were between 1–6% and depended on the concentrations of vitamin C forms and tissues. Recoveries were between 90–96% in samples. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Developing On-Site Trace Level Speciation of Lead,Cadmium and Zinc by Stripping Chronopotentiometry (SCP): Fast Screening and Quantification of Total Metal Concentrations

Electrochemical stripping techniques are interesting candidates for carrying out onsite speciation of environmentally relevant trace metals due to the existing low-cost portable instrumentation available and the low detection limits that can be achieved. In this work, we describe the initial analytical technique method development by quantifying the total metal concentrations using Stripping Chronopotentiometry (SCP). Carbon paste screen-printed electrodes were modified with thin films of mercury and used to quantify sub-nanomolar concentrations of lead and cadmium and sub-micromolar concentrations of zinc in river water. Low detection limits of 0.06 nM for Pb(II) and 0.04 nM for Cd(II) were obtained by the standard addition method using a SCP deposition time of 180 s. The SCP results obtained for Pb(II) and Cd(II) agreed with those of inductively coupled plasma mass spectrometry (ICP-MS). The coupling of SCP with screen-printed electrodes opens up excellent potential for the development of onsite speciation of trace metals. Due to the low analysis throughput obtained for the standard addition method, we also propose a new, more rapid screening Cd(II) internal standard methodology to significantly increase the number of samples that can be analyzed per day.