[Show abstract][Hide abstract] ABSTRACT: Ozonation of aspen sawdust of various moisture content (MC) values was investi-gated. Ozone consumption corresponding to the completion of the ozonation process was shown to be governed by the wood MC. Cellulose-containing material of a low (1–3 %) residual lignin content (LC) was produced under ozonation. It is proposed that ozone dis-solved in water is responsible for delignification. The conversion of lignin during softwood ozonation was investigated by UV and Fourier transform-infrared (FT-IR) spectroscopy. The pathways of lignin transformations are influenced by wood MC value. Keywords: FT-IR spectra of wood; lignin UV second derivative spectra; softwood delignifi-cation; softwood lignin conversions; wood ozonation.
[Show abstract][Hide abstract] ABSTRACT: The effect of active hydrogen accumulation on the surface of the Ni-nanodiamond catalysts has been demonstrated. Lower bound estimation of the hydrogen capacity is 1.3 wt%. Oxygen-containing functional groups on the nanodiamond surface are presumably responsible for the hydrogen accumulation.
[Show abstract][Hide abstract] ABSTRACT: On the basis of the results of investigations carried out by differential scanning calorimetry, X-ray diffraction, nuclear magnetic resonance, high-resolution transmission electron microscopy, and Raman spectroscopy, a scheme for the transformation of detonation nanodiamonds (which are agglomerates of smaller particles) into onion-like carbon nanoparticles during vacuum annealing is verified. At high temperatures, the transition of an individual nanodiamond occurs in a short period of time and may proceed via an amorphous state.
Journal of Surface Investigation X-ray Synchrotron and Neutron Techniques 01/2013; 7(6). · 0.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbon nanotubes (CNTs) of the conic and cylindrical structure were studied by X-ray photoelectron spectroscopy in the initial state and after carboxylation and decarboxylation reactions. The O=C—O and C—O groups were revealed on the surface of the chemically modified samples. It was found that both the carboxylated and decarboxylated cylindrical CNTs contain a smaller amount of oxygen than the corresponding conic CNTs apparently due to differences in their structures.
Russian Chemical Bulletin 01/2013; 62(3). · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Present work deals with development of the synthetic procedures for nitrogen and phosphorous substituted multiwall carbon nanotubes (MWCNT) by pyrolytic technique followed by surface modification by cobalt nanoparticles and utilization of the composite obtained in Fischer-Tropsch (FT) synthesis. It is shown that heterosubstitution in CNT structure changes the electron capacity and acid-based properties of the system, allow effectively stabilize metal nanoparticles of 2-4 nm size and yields to thermally stable and effective catalyst for cobalt FT synthesis.
[Show abstract][Hide abstract] ABSTRACT: The most recent advances in magnetometric methods of investigation of supported Co-, Ni- and Fe-containing catalysts are outlined. Magnetic characteristics provide comprehensive information on (i) catalytic reactions, (ii) the size and distribution of ferromagnetic nanoparticles in topochemical reactions during the catalyst preparation and in the catalytic process and (iii) chemisorption on ferromagnets. The characteristic features and advantages of different magnetometric methods and their combinations with traditional methods of investigation of catalysts are considered.
Russian Chemical Reviews 07/2011; 80(6):579. · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbonaceous deposits formation was established as the primary reason of Pd/TiO2 catalyst deactivation during reductive processing of CCl4 to form hydrodechlorination and oligomerization products. Three methods of carbonaceous deposits elimination were tested: (1) extraction by supercritical CO2, (2) oxidation by ozone in supercritical CO2, and (3) low-temperature glow-discharge oxygen plasma treatment. Synchronic thermal analysis confirms effective carbonaceous deposits removal during regeneration by ozone or low temperature glow-discharge oxygen plasma; by XPS deep oxidation of surface Pd after oxidative treatment (by ozone or oxygen plasma) was found. Thus H2 reduction was proposed as the second step making possible full regeneration of initial catalytic activity of Pd/TiO2.
Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/2011; 58(2):263-271.
[Show abstract][Hide abstract] ABSTRACT: The sonochemical deposition of nickel nanoparticles onto the multiwall carbon nanotube aggregates leads to a uniformly distributed metal phase at high loadings and an average nickel crystal size of 4–8 nm at a 25–50 wt% nickel content. Its application enhances the catalytic activity of Ni/multiwall carbon nanotube material in the selective hydrogenation of chloroacetophenone by factors of 2–18, as compared with that prepared by traditional decoration methods.
[Show abstract][Hide abstract] ABSTRACT: Hierarchical porous biomorphic catalyst Ce0.5Zr0.5O2 for oxidation of soot was prepared by calcination of sawdust, impregnated by solutions of Ce and Zr nitrates. SEM analysis revealed total reproducibility of biotemplate morphology by final oxide. Biomorphic Ce-Zr oxide has certain advantages over coprecipitated one: it possesses larger surface area, is thermally stable, has higher amount of mobile lattice oxygen and lower temperature of its release. Thanks to its filamentous-like morphology and improved redox properties biomorphic catalyst is more active in combustion of soot.
Studies in Surface Science and Catalysis - STUD SURF SCI CATAL. 01/2010; 175:305-309.
[Show abstract][Hide abstract] ABSTRACT: Present work points out the differences between possible tubular carbon structures: nanotubes and nanofibers, as well as describes ways of their modification for utilization for new materials design. For material characterization, XRD, XPS, Raman spectroscopy, thermal analysis, HRTEM and SEM, pore size distribution, EELS, elemental analysis and adiabatic bomb calorimetry were used. Heats of formation for nanotubes and nanofibers and their dependence on carboxylation extent as well as properties of the modified materials are also discussed. The perspectives of applications of modified carbon nanotubes in catalysis and polymers chemistry are given.
[Show abstract][Hide abstract] ABSTRACT: Hydrodechlorination (HDC) is a remarkable environment friendly and cost saving alterative to the traditional methods for utilization of chlorinated pollutants. The development of new catalysts and revelation of general approaches to catalysts design are discussed in present work. In this work several directions for catalyst design were considered: (1) change of support nature to influence on a formation of Pd-containing active site; (2) modification of active site by second metal addition; (3) varying of metal deposition method and reduction agent on an active site formation.
Studies in Surface Science and Catalysis - STUD SURF SCI CATAL. 01/2010; 175:293-296.
[Show abstract][Hide abstract] ABSTRACT: Alkylation of Sn(OCH2CH2NMe2)2 (1) by MeI or MeOTf leads to a mixture of quaternary ammonium salts by alkylation of the NMe2 moiety. Reaction of Sn(acac)2 (2) with MeOTf gives unexpected redistribution product Sn(acac)OTf (3), which is a rare example of mono acetylacetonato tin (II) derivatives. Pentacoordinated monoorgano stannyl cation PhSn(OCH2CH2NMe2)2+ was generated by salt metathesis from PhSn(OCH2CH2NMe2)2Cl (5) and Ag[Al(OCH(CF3)2)4] or Ag[B(C6F5)4]. This cation was not isolated due to its strong electrophilic nature. It abstracts substituents from aluminate and borate weakly coordinating anions (WCAs) leading to redistribution products [Al[OCH(CF3)2]2OCH2CH2NMe2]2 (6) and [Ph(C6F5)Sn(OCH2CH2NMe2)2][H2OB(C6F5)3] (9), respectively. Structures of 3 and 6 were established by single-crystal X-ray diffraction analysis.
Journal of Organometallic Chemistry 01/2010; 695(3):365-369. · 2.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The high prospects of galvanic displacement for the preparation of high-reactivity mixed catalysts with a small content of platinum metal have been shown for a Pd(Cu)/support system.
[Show abstract][Hide abstract] ABSTRACT: Nanocomposites based on Pd and Ni encapsulated (@) in carbon have been prepared by condensation of nanoparticles in the flow of gas mixture (Ar and hydrocarbons) and characterized by TEM, TGA-MS, XRD spectroscopy and BET adsorption measurements. Ni@C, NiPd@C nanocomposites consist of metal core 3–10nm in size covered by a few carbon layers; Pd particles are 10–15nm in size, have no carbon shell and are joined in chains. Catalytic properties were investigated in hydrodechlorination (HDC) of chlorobenzene in gas phase and 1,2,4-trichlorobenzene in liquid phase. Totally carbon covered particles of Ni and Pd-Ni demonstrate high activity and stability in gasphase hydrodechlorination of chlorobenzene at 100–350°C and in liquid phase HDC of 1,2,4-trichlorobenzene at 130°C under middle pressure.
Studies in Surface Science and Catalysis - STUD SURF SCI CATAL. 01/2010; 175:289-292.
[Show abstract][Hide abstract] ABSTRACT: The results of DFT study of the reaction between binuclear ZrIV hydride complex (≡SiO)2(H)Zr(H)2Zr(H)(OSi≡)2 and propane show that centres of this type would be more prospective catalysts for alkane hydrogenolysis under mild conditions (T < 450 K, P ∼ 1 atm) than previously studied mononuclear ZrIV complexes.
[Show abstract][Hide abstract] ABSTRACT: The relationship between the catalytic activity and Pd particle size in Pd/ultradispersed diamond catalysts is established in the hydrodechlorination of 1,3,5-trichlorobenzene under multiphase conditions.
[Show abstract][Hide abstract] ABSTRACT: A series of organotin compounds bearing two intramolecular N → Sn coordination bonds RSn(OCH2CH2NMe2)2Cl (R = Me (4), n-Bu (5), Mes (6)) were synthesized in good yields. These compounds as well as 2 (R = Ph) react with PhSnCl3 to give redistribution products RPhSnCl2 and (Me2NCH2CH2O)2SnCl2 (3). The direction of redistribution reactions is reverse to Kocheshkov reaction. DFT calculations have shown that the driving force of the reactions is formation of intramolecular N → Sn coordination bonds in (RO)2SnCl2 (3), the Lewis acid stronger than RSn(OR)2Cl (2, 4–6). The mechanism of the redistribution reaction between 2 and PhSnCl3 consists of two steps: (1) initial exchange of OCH2CH2NMe2 and Cl to give PhSn(OCH2CH2NMe2)Cl2 (7) followed by (2). Ph and OCH2CH2NMe2 exchange.
Journal of Organometallic Chemistry 12/2008; 693(26):3847–3850. · 2.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The number of in vitro experimental studies was carried out with the use of intact tissues to establish a mechanism of laser-tissue interaction. However, in the process of degeneration, both biochemical composition and behavior of the disc were altered drastically. The objective of this study was to evaluate the role of the main matrix components in laser modification of annulus fibrosus (AF) under IR laser irradiation.
The samples of AF in a motion segment after hyaluronidase treatment, trypsin digestion and glycation by glyceraldehyde were heated in hydrothermal bath (95 degrees C, 2 min) or irradiated by laser at 1.56 microm. Specimens were imaged by cross-polarization optical coherence tomography (CP-OCT), and then analyzed by differential scanning calorimery (DSC).
According to CP-OCT and DSC data non-significant alteration was revealed in AF after hyaluronidase treatment, glycation led to stabilization of annulus collagen and trypsin digestion resulted in a noticeable impairment of collagen fibrils. Laser treatment induced subsequent damages of AF matrix but these damages cannot be explained by laser heating only. The specificity of chemical modification of AF matrix has an influence on a character of collagen network alteration due to IR laser effect. Minimal and maximal alterations are observed for hyaluronidase and trypsin treated samples respectively. Glyceraldehyde fixed samples showed failure of the collagen structure after moderate laser treatment; at the same time thermal denaturation of collagen macromolecules was negligible. We assume that a mechanical effect of laser irradiation plays an important role in laser-induced annulus collagen modification and propose the scheme of physico-chemical process occurring under non-uniform IR laser treatment in AF tissue.
CP-OCT and DSC techniques allow us to record the alteration of collagen network organization as a result of chemical modification. There were detected significant and specific effects of the biochemical composition and material properties on the response of AF collagen network on laser irradiation. The results go in accordance with our hypothesis that the primary effect of laser influence on collagen network under tension is the mechanical damage of collagen fiber.
Lasers in Surgery and Medicine 08/2008; 40(6):422-32. · 2.46 Impact Factor