Interaction in fullerene—ammonia system at 423—773 K

The interaction of C₆₀ fullerite and C₆₀—NH₄Cl mixture (8 wt. % of NH₄Cl, promoter of reaction) with ammonia was investigated at a starting NH₃ pressure of 0.6—0.7 MPa in the temperature range 423—773 K. Raising the temperature to 723 K is accompanied by hydrogenation and nitrogenation of the C₆₀ matrix. Treatment of fullerite with ammonia at 773 K is followed by the decomposition of the fullerene framework and formation of X-ray amorphous product. The physico-chemical properties of hydride-nitride phases formed during the interaction were investigated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 217—219, February, 2006.     

Effect of conducting additives on the properties of composite cathodes for lithium-ion batteries

In an attempt to achieve lithium-ion batteries with high rate capability, the effect of conducting additives with various shapes and contents on the physical and electrochemical performances was evaluated. Although the density of the cathode decreased upon the addition of the additives, the electrical conductivity and electrochemical performance were greatly improved. The composite cathodes with well-dispersed multi-walled carbon nanotubes (MWCNTs) exhibited excellent high rate capabilities and cyclabilities. In the case of cathode with 8 wt.% of MWCNTs (low density—LD), the highest discharge capacity of 136 mAh/g was obtained at 5 C-rate and capacity retention of 97% for 50 cycles was observed at 1 C-rate of discharge. The cathode with a mixture of 2 wt.% of Super P and 4 wt.% of MWCNTs (LD) also exhibits improved cycle performances. The volume changes in the charge and discharge processes were successfully controlled by the bundles distributed between the host particles.     

Thermal behavior of aromatic polyamic acids and polyimides containing oxadiazole rings

Two aromatic polyimides and the corresponding poly(amic acid)s, with oxadiazole and para/meta phenoxyphenylene rings in the backbone, were synthesized and the structure — thermal properties correlation was followed by dynamic mechanical analysis. Concerning the poly(amic acid)s, the glass transition domain was emphasized only for the compound with meta-oriented rings because the process of imidization takes place with increasing temperature. A multiplex experiment was performed to calculate the activation energy of the transition localized under 200°C. Consecutive heating-cooling-heating cycles were accomplished. All phenomena are discussed by cross-examination of the storage modulus (E′), loss modulus (E″) and loss factor tanδ variation with temperature.     

Effect of the alkyl chloride-to-aluminum molar ratio in the catalysts of dec-1-ene oligomerization on the product distribution and the chlorine content in the products

Dec-1-ene oligomerization in the presence of an aluminum—1-dodecyl chloride system was studied. A mixture of low-molecular-weight oligodecenes containing 25–40 wt.% dimers and 30–52 wt.% dec-1-ene trimers is formed at the molar ratios RCl/A1 = 0.5–1.5. The oligomerization was assumed to occur under the action of cationic active sites, which are formed during the reaction of 1-chlorodedecane with aluminum. At temperatures of 120–130°C and molar ratios RCl/A1 = 0.5–1.5 metallic aluminum completely dechlorinates 1-chlorododecane in a dec-1-ene medium. The character of the effect of highly dispersed Al and the RCl/A1 molar rato on the fractional composition and chlorine content in oligodecenes was revealed. The latter are formed by an aluminum—tert-butyl chloride system used in the industrial oligomerization of dec-1-ene. A mechanism of Al dissolution by alkyl chlorides with the simultaneous dechlorination of alkyl chloride and formation of cationic active sites in A1-RCl systems was proposed to explain the results obtained. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 661–665, March, 2008.     

Determination of 11 priority pollutant phenols in wastewater using dispersive liquid—liquid microextraction followed by high-performance liquid chromatography—diode-array detection

Dispersive liquid—liquid microextraction coupled with high-performance liquid chromatography—diode-array detection was applied for the extraction and determination of 11 priority pollutant phenols in wastewater samples. The analytes were extracted from a 5-mL sample solution using a mixture of carbon disulfide as the extraction solvent and acetone as the dispersive solvent. After extraction, solvent exchange was carried out by evaporating the solvent and then reconstituting the residue in a mixture of methanol–water (30:70). The influences of different experimental dispersive liquid—liquid microextraction parameters such as extraction solvent type, dispersive solvent type, extraction and dispersive solvent volume, salt addition, and pH were studied. Under optimal conditions, namely pH 2, 165-μL extraction solvent volume, 2.50-mL dispersive solvent volume, and no salt addition, enrichment factors and limits of detection ranged over 30–373 and 0.01–1.3 μg/L, respectively. The relative standard deviation for spiked wastewater samples at 10 μg/L of each phenol ranged between 4.3 and 19.3% (n = 5). The relative recovery for wastewater samples at a spiked level of 10 μg/L varied from 65.5 to 108.3%.     

Evaluation and interlaboratory validation of a GC-MS method for analysis of pesticide residues in teas

A method was described for simultaneous determination of nine organic heterocyclic pesticide residues by gas chromatography-mass spectrometry-selected ion monitoring. Atrazine, vinclozolin, procymidone, triflumizole, imazalil, buprofezin, propiconazole, fenarimol, and pyridaben were clearly separated from each other, extracted with acetone—hexane mixture, purified with graphitized carbon black cartridge and neutral Al₂O₃ cartridge, eluted with acetone—hexane mixture, simultaneously determined by GC-MS, and then quantified with an external standard method. Recoveries of pesticides ranged from 73 % to 116 % at the spiked level of 0.01–30 mg kg⁻¹, while the relative standard deviation was between 3 % and 27 %. In addition, the limits of determination (0.01 mg kg⁻¹ to 5.0 mg kg⁻¹) and linearity (0.02–40 μg mL⁻¹) revealed that simultaneous determination of multi-residues in Chinese teas (like Oolong tea, green tea, red tea, etc.) was possible. Furthermore, an interlaboratory study among 5 labs was conducted to further validate the method, and the results were satisfactory.     

Highly sensitive determination of polycyclic aromatic hydrocarbons in ambient air dust by gas chromatography-mass spectrometry after molecularly imprinted polymer extraction

A method based on solid--phase extraction with a molecularly imprinted polymer (MIP) has been developed to determine five probable human carcinogenic polycyclic aromatic hydrocarbons (PAHs) in ambient air dust by gas chromatography-mass spectrometry (GC-MS). Molecularly imprinted poly(vinylpyridine-co-ethylene glycol dimethacrylate) was chosen as solid-phase extraction (SPE) material for PAHs. The conditions affecting extraction efficiency, for example surface properties, concentration of PAHs, and equilibration times were evaluated and optimized. Under optimum conditions, pre-concentration factors for MIP-SPE ranged between 80 and 93 for 10 mL ambient air dust leachate. PAHs recoveries from MIP-SPE after extraction from air dust were between 85% and 97% and calibration graphs of the PAHs showed a good linearity between 10 and 1000 ng L⁻¹ (r = 0.99). The extraction efficiency of MIP for PAHs was compared with that of commercially available SPE materials—powdered activated carbon (PAC) and polystyrene-divinylbenzene resin (XAD)—and it was shown that the extraction capacity of the MIP was better than that of the other two SPE materials. Organic matter in air dust had no effect on MIP extraction, which produced a clean extract for GC-MS analysis. The detection limit of the method proposed in this article is 0.15 ng L⁻¹ for benzo[a]pyrene, which is a marker molecule of air pollution. The method has been applied to the determination of probable carcinogenic PAHs in air dust of industrial zones and satisfactory results were obtained.     

Mechanics of polymer nanocomposites modified with fulleroid nanofillers

Polymer nacomposites based on thermosetting (epoxy resins) and thermoplastic (PA-12) polymer matrices with fulleroid and carbon modifiers are synthesized through in situ polymerization, and the mechanical properties are investigated. The introduction of fulleroid modifiers has almost no effect on the mechanical properties of thermosetting formulations; however, in the case of thermoplastic formulations, Young’s modulus and tensile strength increase by 30–40% after introduction of 0.02–0.06 wt % fulleroid modifiers.     

Nonoxidative conversion of methane into aromatic hydrocarbons on Ni-Mo/ZSM-5 catalysts

The nonoxidative conversion of methane into aromatic hydrocarbons on high-silica zeolites ZSM-5 containing nanosized powders of molybdenum (4.0 wt %) and nickel (0.1–2.0 wt %) was studied. Data on the acid characteristics of the catalysts and the nature and amount of coke deposits formed on the surface of the catalysts were obtained using the thermal desorption of ammonia and thermal analysis. The microstructure and composition of Ni-Mo/ZSM-5 catalysts were studied by high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The formation of various chemical species in the samples was detected: oxide-like clusters of Mo within zeolite channels (∼1 nm), molybdenum carbide particles (5–30 nm) on the outer surface of the zeolite, and Ni-Mo alloy particles with different compositions (under reaction conditions, carbon filaments grew on these particles). It was found that, as the Ni content was increased from 0.1 to 2.0 wt %, the rate of deactivation of the catalytic system increased because of blocking pores in the zeolite structure by filamentous carbon up to the formation of condensed coke deposits.     

Thermochemistry of CuCl2 dissolution in a water—2-propanol—NaCl mixture at 298.15 K

The enthalpies of solution of CuCl₂ (m < 0.07 mol per kg of the solvent) in a water—2-propanol—NaCl mixture at a NaCl content from 0 to 5 mol % and a 2-propanol content from 0 to 40 mol % were determined by calorimetry at 298.15 K. The effect of the electrolyte and organic component on the solvation of CuCl₂ is discussed.     

Immobilization of Ru — TsDPEN catalyst on functionalized MCM — 41

A Ru — TsDPEN (RuCl[(1S,2S)-N-p-tosyl-1,2-diphenylethylendiamine]p-cymene) catalyst of the Noyori type was immobilized in the channels of MCM — 41 molecular sieve functionalized by (3 — aminopropyl)triethoxysilane (APTES). The resulting compound was tested as a catalyst for the hydrogenation of 1-methyl-3,4-dihydroisoquinoline (MIQ) under laboratory conditions using an azeotropic mixture of formic acid and triethylamine (5:2) as the source of hydrogen and compared to the results acquired in the corresponding system.     

Detection of organic products of polymer pyrolysis by thermogravimetry-supersonic jet-skimmer time-of-flight mass spectrometry (TG-Skimmer-SPI-TOFMS) using an electron beam pumped rare gas excimer VUV-light source (EBEL) for soft photo ionisation

A commercial thermogravimetry—supersonic jet-skimmer quadrupole mass spectrometer system (TG-Skimmer-QMS, Netzsch GmbH, Germany) was successfully converted for soft single photon ionisation time-of-flight mass spectrometric (SPI-TOFMS) detection of organic compounds. VUV light for SPI was generated by an electron beam pumped argon excimer light source (EBEL; E _photon = 9.8 eV). Furthermore, the versatility of the system was conserved, as high temperature TG and DSC measurements as well as electron ionisation mass spectrometry for the detection of inorganic compounds are still possible. The new system was tested with two polymers and a hydrocarbon mixture (diesel). It was demonstrated that aliphatic and aromatic organic compounds can be detected without fragmentation. Thus the system allows the recording of a readily interpretable organic signature of, e.g. thermal polymer decomposition. The thermal degradation of polystyrene shows a rich signature of the monomer, some oligomers and minor products of irregular cleavings of carbon chains. Polycarbonate exhibits a thermal decomposition fingerprint which is dominated by products of bisphenol A. The bisphenol A monomer, however, is also detectable.     

Capillary complexation gas chromatography in analysis of cyclic and aromatic hydrocarbons

Summary Results of studies on stationary phases containing copper(II), nickel(II) and cobalt(II) chloride chemically bonded via cyano—or thiol groups are presented. The retention parameters—i.e. retention factor (k), retention index (I) and molecular retention index (ΔMe) and specific retention volume (Vg)-enabled the characteristics of specific interaction between aromatic and cyclic hydrocarbons and metal complexes chemically bonded to stationary phases to be determined. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Xylanase and β-Xylosidase Production by <Emphasis Type="BoldItalic">Aspergillus ochraceus</Emphasis>: New Perspectives for the Application of Wheat Straw Autohydrolysis Liquor

The xylanase biosynthesis is induced by its substrate—xylan. The high xylan content in some wastes such as wheat residues (wheat bran and wheat straw) makes them accessible and cheap sources of inducers to be mainly applied in great volumes of fermentation, such as those of industrial bioreactors. Thus, in this work, the main proposal was incorporated in the nutrient medium wheat straw particles decomposed to soluble compounds (liquor) through treatment of lignocellulosic materials in autohydrolysis process, as a strategy to increase and undervalue xylanase production by Aspergillus ochraceus. The wheat straw autohydrolysis liquor produced in several conditions was used as a sole carbon source or with wheat bran. The best conditions for xylanase and β-xylosidase production were observed when A. ochraceus was cultivated with 1% wheat bran added of 10% wheat straw liquor (produced after 15 min of hydrothermal treatment) as carbon source. This substrate was more favorable when compared with xylan, wheat bran, and wheat straw autohydrolysis liquor used separately. The application of this substrate mixture in a stirred tank bioreactor indicated the possibility of scaling up the process to commercial production.     

Dynamics of joint adsorption of mutually soluble substances by activated carbons

A model for the dynamics of isothermal absorption of a binary mixture of an organic substance, soluble in water, and water vapor in a fixed bed of activated carbon was proposed. It includes the equations of material balance and the Myers—Prausnitz model for equilibrium adsorption. The possibility of formation of the condensed phase during the adsorption of an organic substance on moist activated carbon was shown. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1491–1495, August, 1998.     

Laser desorption/ionization fourier transform mass spectrometry of thin films deposited on silicon by plasma polymerization of acetylene

Thin films deposited on silicon substrate by three different methods of plasma polymerization of acetylene were analyzed by direct laser desorption/ionization Fourier transform mass spectrometry. High-resolution mass spectra showed the presence of carbon clusters and hydrocarbon oligomers in different relative abundances. During unipolar and continuous discharge polymerization of acetylene-hydrogen gas mixtures, quadrupole mass spectra of the plasma constituents showed the presence of molecular species with m/z lower than 100 — mainly peaks of C₄H₂ and C₆H₂. Films produced had smooth surfaces and the corresponding LDI-FTMS spectra displayed only carbon cluster signals in the positive ion mode and both hydrocarbon and carbon cluster signals (with much higher relative abundance of carbon cluster signals) in the negative ion mode. Alternatively, during bipolar discharge with either higher acetylene gas flux (>40 cm³/min) or longer deposition times (>10 min), quadrupole mass spectra of the plasma constituents showed signals corresponding to polycyclic aromatic hydrocarbons (PAH) with m/z higher than 100. SEM pictures of the bipolar thin films demonstrated the presence of “flower” structures and nanoparticles developed on the surface. LDI-FTMS spectra of such thin films showed either total absence or lower relative abundance of carbon cluster signals, compared with hydrocarbon signals.     

Color reactions of hederagenin and its glycosides

The spectrophotometric reactions of triterpene compounds with concentrated sulfuric acid, a mixture of sulfuric acid and ethanol, and a mixture of sulfuric and acetic acids has been studied with hederagenin and its glycosides — caulosides A, C, and D, isolated from the Far Eastern plantCaulophyllum robustum Maxim — as examples. Conditions for performing the reaction which exclude the influence of the carbohydrate components of the glycosides from the determination of hederagenin have been suggested. The reaction with a mixture of sulfuric acid and ethanol has been used to determine the amounts of caulosides A and C in a total preparation after their separation by the TLC method. The relative error of the determination did not exceed 5 rel.%. Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 643–646. September–October, 1980.     

The interaction of organic ammonium cations with polyacrylate and copolyacrylates

Summary The interaction of aromatic ammonium cations with a series of polyacrylates has been investigated by a study of equilibrium dialysis of the sodium polyacrylate against aromatic ammonium halide solutions. The degree of association was measured — after correcting for theDonnan effect — over a wide range of organic cation — polyanion concentration ratios; uncorrected equilibrium constants for the polyion —counterion binding were then determined by the graphical method. For any particular aromatic cation, the degree of interaction increases in the order, 80/20 copolyacrylamide-acrylate < 50/50 copolyacrylates < polyacrylate. Interaction is greatest with acridinemethonium, acridine ammonium and long-chain alkyl pyridinium cations. The overall interaction, then, involves two types of binding.Debye- Hückel (orψ-type) electrostatic andBjerrum (orP-type): the latter may, in turn, depend on both electrostatic forces between adjacent carboxyl ammonium groups and onvan der Waals interactions between the aromatic ring of the counterion and the organic section of the polymer backbone. The free energy contribution from thesevan der Waals effects have been estimated from the uncorrected equilibrium constants: and are appreciable for high molecular weight cations. For examples, for interaction with 0.01 N polyacrylate, the values were as follows:

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Zusammenfassung Die Wechselwirkung von aromatischen Ammonium-kationen mit einer Reihe von Polyacrylaten wurde durch Studium der Gleichgewichtsdialyse von Natrium-Polyacrylat gegen aromatische Ammonium-Halogen-L?sungen untersucht. Der Assoziationsgrad — nach Korrektur für denDonnan-Effekt — wurde über einen weiten Bereich des Verh?ltnisses organischer Kationen zu Poly-Anionen-Konzentrationen gemessen. Die unkorrigierten Gleichgewichtskonstanten für die Verbindung Poly-Ionen/Gegenionen wurde graphisch bestimmt. Für irgendein spezielles aromat. Kation w?chst der Grad der Wechselwirkung in der Reihe 80/20 Copolyacrylamid-Acrylat < 50/50 Copolyacrylat < Polyacrylat. Die Wechselwirkung ist am gr?\ten mit Acridin-Methonin, Acridin-Ammonium und langkettigen Alkyl-Pyridin-Kationen. Die Gesamtwechselwirkung umfa\t 2 Bindungstypen.Debye/Hückel (oderψ-Type) elektrostatisch undBjerrum (oder (P-Type): letztere kann sowohl von elektrostatischen Kr?ften zwischen benachbarten Carboxyl-Ammoniumgruppen oder vonvan der Waals-Wechselwirkung zwischen dem aromatischen Ring des Gegenions und dem organischen Teil der polymeren Hauptkette abh?ngen. Der Beitrag der freien Energie aus diesemvan der Waals-Effekt wurde aus den unkorrigierten Gleich-gewichtskonstanten abgesch?tzt und ist für Kationen hohen Molekulargewichts betr?chtlich. Z. B. sind für die Wechselwirkungen zwischen 0,01 N Polyacrylat die (−δG) _p van der Waals-Werte wie folgt:

     

β-Glucosidase production by Trichoderma reesei

The hydrolysis of cellulose to the water-soluble products cellobiose and glucose is achieved via synergistic action of cellulolytic proteins. The three types of enzymes involved in this process are endoglucanases, cellobiohydrolases, and β-glucosidases. One of the best fungal cellulase producers is Trichoderma reesei RUT C30. However, the amount of β-glucosidases secreted by this fungus is insufficient for effective cellulose conversion. We investigated the production of cellulases and β-glucosidases in shake-flask cultures by applying three pH-controlling strategies: (1) the pH of the production medium was adjusted to 5.8 after the addition of seed culture with no additional pH adjustment performed, (2) the pH was adjusted to 6.0 daily, and (3) the pH was maintained at 6.0 by the addition of Tris-maleate buffer to the growth medium. Different carbon sources—Solka Floc 200, glucose, lactose, and sorbitol—were added to standard Mandels nutrients. The lowest β-glucosidase activities were obtained when no pH adjustment was done regardless of the carbon source employed. Somewhat higher levels of β-glucosidase were measured in the culture filtrates when daily pH adjustment was carried out. The effect of buffering the culture medium on β-glucosidase liberation was most prominent when a carbon source inducing the production of other cellulases was applied.     

A new cellular carbon support for catalysts: preparation and study of structure

Cellular carbon has been prepared by pyrolysis of a propane—butane mixture in a flow reactor at 700–1250 K. Its structural characteristics were studied by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and adsorption methods. It was shown that cell-type carbon possesses a unique structure in contrast to carbon composite “Sibunnit” and filamentous carbons and it may be a promising support for catalyst preparation.