Russian Journal of Applied Chemistry最新文献

The catalytic activity of C,N-chelate diaminocarbene palladium(II) complexes containing the 3,4-diaryl-1Н-pyrrol-2,5-diimine fragment in the Suzuki reaction was studied. Comparative analysis of the catalytic activity of two types of C,N-chelate diaminocarbene complexes containing in the inner sphere, along with the diaminocarbene ligand, two different ligand combinations, (1) organic isocyanide and chloride ligand and (2) two chloride ligands, was performed. The influence of the electronic effects of substituents in the catalyst on the reaction yield was examined.

The possibility of recovering and concentrating Pd(II) from simulated nitrate–nitrite PUREX process raffinate with a highly effective extractant, 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1H-pyrazole (chloroform as a diluent), was examined. The 0.10 M extractant solution rapidly (within 5 min) and completely recovers Pd(II) with its tenfold preconcentration in the organic phase and highly selective separation from Fe(III), Pr(III), and Ni(II). The extracted Pd(II) and coextracted Ag(I) are stripped with a 2 M NH₄OH + 10 g L^–1 NH₄NO₃ solution to more than 99.9 and to 97.1%, respectively.

Composite materials based on blends of low- and high-density polyethylene, containing finely dispersed zinc oxide, were studied by X-ray diffraction analysis, differential thermal analysis, and scanning electron microscopy. The strength and strain characteristics of the composite and its resistance to thermal oxidative degradation are improved on introducing finely dispersed zinc oxide. This is apparently associated with the formation of interphase bonds between zinc-containing nanoparticles and polymer compound components. The nanocomposites based on blends of low- and high-density polyethylene, containing finely dispersed zinc oxide, can be processed by pressing, pressure casting, and extrusion, which expands their application fields.

An optically active norbornene-type monomer was prepared from β-pinene (a monoterpene compound) and cis-5-norbornene-exo-2,3-dicarboxylic anhydride. The metathesis polymerization of this monomer in the presence of the first-generation Grubbs catalyst was studied, and a soluble high-molecular-mass metathesis polymer exhibiting film-forming properties was synthesized in 90% yield. The monomer and polymer structures were confirmed by ¹Н and ¹³С NMR spectroscopy. The metathesis polymers obtained were characterized by thermal gravimetric analysis, differential scanning calorimetry, X-ray diffraction analysis, and polarimetry.

Studies aimed at the development of cheap, safe, and effective carbon materials based on domestic resources for negative electrodes of lithium-ion and post-lithium-ion batteries are topical and have high practical significance. The paper summarizes the results of studying how the temperature of the heat treatment of petroleum coke in a nitrogen flow influences its physicochemical and electrochemical properties. Petroleum coke was kept for 5 h in a nitrogen flow at fixed temperatures of 450, 600, 800, 1000, and 1200°C. Heat treatment of petroleum coke leads to a significant decrease in the specific resistivity (from 4.8 × 10⁷ to 1 × 10^–2 Ω cm), to an increase in the specific surface area, and to a decrease in the pycnometric density (the temperature of 1200°C is an exception). Petroleum coke that has not been heat-treated or has been heat-treated at 450 °С exhibits no electrochemical activity. The carbon electrodes made of petroleum coke heat-treated at 600°C in a nitrogen atmosphere exhibit the maximal anodic capacity for lithium (340–350 mA h/g). However, carbon electrodes based on petroleum coke heat-treated at 600°С exhibit short cyclic duration and high irreversible capacity (58–60%). An increase in the petroleum coke heat treatment temperature to 1200°С leads to a decrease in the irreversible capacity to 40% and in the reversible anodic capacity to 220 mA h/g and to an increase in the cycling duration of the carbon electrodes. The petroleum coke heat-treated un a nitrogen atmosphere at 1000°C is the most promising material for negative electrodes of lithium-ion batteries from the viewpoint of the set of physicochemical and electrochemical properties.

Abstract

Gasoline produced by hydrotreating light and heavy naphtha and reforming hydrotreated heavy naphtha, hydrogen required for both processes produced by the reforming unit as a byproduct, compression, and recycling of hydrogen required for reforming reactions provided by recycle gas compressor (centrifugal multi-stages compressor), due to the design criteria of this compressor the anti-surge system pass 18000 kg/h, of hydrogen from discharge to suction of compressor with 3” control valve, at the low flow situation during the startup of the unit to avoid the lake of gas flow and avoid overpressure in the discharge of the compressor. Anti-surge system in this compressor contains no inter-stage cooler, the suction temperature of the compressor is designed at 43℃, and the discharge of the compressor is 79℃ when the anti-surge system is involved in the process, the suction temperature of the compressor becomes 70℃, and the discharge becomes 108℃ due to the heat accumulation of recycle gas out of the anti-surge system. In an aim to solve this problem, the outlet of the anti-surge system of the compressor connected with the process heat exchanger, to cool down the hydrogen inlet to suction of the compressor to approximately 46℃ and back to the design limits, the disadvantage of this solution is the absorption of the light end associated with recycle gas posing in the process heat exchanger, which reduces the total molecular weight of recycle gas through the anti-surge system from 13.336 to 10.51 kg/kg mol at start of the run, and from 16.155 to 12.15 kg/kg mol at the end of the run.

Electrochemical deposition of Ni–SiC composite coatings with submicrometer silicon carbide powder from a suspension electrolyte stabilized by vibrational mixing was studied. The structural features of the coating are described. Irrespective of the vibrational mixing conditions, thin coatings are layers with pronounced relief. Examination of the cross sections shows that the basic fragments forming the relief are metal–ceramic fragments consisting of SiC particles and nickel. A detailed study of thin sections shows that a nickel film is present on the surface of each particle, which indicates that the metal is reduced, in particular, on the particle surface. In the structure of thick composite coatings, agglomerations of SiC particles are also revealed. A coating formation mechanism consisting in the adsorption of SiC particle agglomerates and instantaneous nickel deposition on their surface was suggested. The results of analysis of the coating metal matrix by backscattered electron diffraction agree with the suggested mechanism.

Vulcanization is one of the most important stages in the production of rubber products. Assigning optimum process parameters will allow obtaining high-quality products at the lowest cost. The cost of physical experiments to establish the required parameters can be reduced by theoretical calculation of the vulcanization kinetics. The most significant parameters are the vulcanization duration and temperature changes in various parts of the rubber compound; therefore, the majority of studies are aimed at determining their optimum values. The vulcanization process includes three stages: induction, curing stage, and reversion. The numerical calculation of the first two stages was performed in order to determine the effect of the heat generation in the reaction on the cure course, depending on the product thickness. Plates with a thickness of 2, 5, and 10 mm were considered. A block diagram of the algorithm for calculating the state of cure of a rubber compound is presented. Graphical dependences of the state of cure and temperature for plates of various thicknesses, made of a rubber compound used in the production of truck tires, were obtained for two cases: with and without taking into account the heat generation in the reaction. Data on the vulcanization duration are also given. With an increase in the product thickness, the effect of the heat generation on the vulcanization course increases significantly. Taking into account the heat generated in the reaction leads to a 1.6% change in the vulcanization duration for the 2 mm thick plate, 13% change for the 5 mm thick plate, and 50% change for the 10 mm thick plate. Thus, it is necessary to take into account the thermal effect when calculating the state of cure of rubber compounds, especially for thick items.

The action of an electron beam on crystals of tetramethylethylenediaminium nitrilotriacetate [HMe₂NCH₂CH₂NMe₂H]²⁺[HN(CH₂COOH)(CH₂COO)₂]^–₂, ammonium heptamolybdate tetrahydrate (NH₄)₆Mo₇O₂₄‧4H₂O, and polymeric zinc nitrilotrimethylenephosphonate trihydrate (ZnH₄L‧3H₂O)_n, on a lamellar crystal of 2,2'-(ethylenedioxy)di(ethylaminium) trifluoroacetate CF₃C(O)O^{‒ +}H₃N(CH₂CH₂O)₂CH₂CH₂NH₃^+‒O(O)CCF₃, and on films of the monoethanolaminium salt of ethylenediaminetetraacetic acid [Н₃NCH₂CH₂OH]⁺₂[(OOCCH₂)₂NCH₂CH₂N(CH₂COOH)₂]^2– was studied. A Tescan VEGA II electron microscope was used as an exposure tool. The microrelief was examined at magnifications from 500× to 50000×. The survey was carried out at an accelerating voltage of 20 kV and a working distance of 2–8 mm, using secondary (SE) and backscattered (BSE) electron detectors. A copper–nickel alloy and silicate glass were used as the substrate material for the films. The crystals and films were irradiated with an electron beam of various powers, forming an area 20 × 20 μm in size. At low power, the area dimensions are strictly 20 × 20 μm, and the surface remains relatively flat. An increase in the power or in the exposure time while maintaining the power causes an increase in the size by 5 to 34%. The maximum impact causes the formation of defects in the form of cracks, swellings, bubbles, holes, and craters. The elevation of the surface increases with increasing radiation dose.

Dielectric properties of isomeric glassy 5-cyclohexyl-2-norbornene polymers synthesized by the metathesis and vinyl-addition schemes were studied in a wide range of electric field frequencies (0.1–1 × 10⁶ Hz) and temperatures (from –100 to +200°С). These polymers have close values of the dielectric constant (2.28–2.29 at the electric field frequency of 1 MHz and 25°С) and low values of dielectric loss caused by dipole-segmental loss. Analysis of the imaginary part of the dielectric spectrum shows that the vinyl-addition polymer is characterized by a single relaxation process and the metathesis polymer, by three processes associated with cooperative segmental motion of backbones, with changes in the conformation of the cyclohexyl substituent, and with local motion in monomeric units.