Results 1 - 10 of 272
Results 1 - 10 of 272. Search took: 0.016 seconds
|Sort by: date | relevance|
[en] Upon γ-irradiation, the product of the polycondensation of petroleum asphaltite with formaldehyde has been found to acquire the properties of a macromolecular initiator for grafting macromolecular chains of acrylic acid. Radiation-resistant ion-exchangers based on the grafted polymer have been prepared
[en] Chromatography-mass-spectrometry was used to examine the stability of admixtures of C1−C7 hydrocarbons, fluorine and chlorinated derivatives of hydrocarbons, alkyl derivatives of silane, homologs of monosilane, and siloxanes in monosilane in its storage in molybdenum-glass ampules and stainless-steel cylinders. It was found that, in the case of storage in glass ampules, the concentration of ethylene and tetrafluoroethylene admixtures decreases and that of ethyl silane and disilane increases. When monosilane is stored in a stainless steel cylinder, the concentration of the acetylene admixture it contains changes.
[en] Additives for diminishing the content of carbon monoxide in gases formed in regeneration of the cracking catalyst without noble metals were synthesized and tested. As additives of this kind can serve mixed oxides based on copper, cerium, magnesium, and aluminum and manganese oxide supported by gamma aluminum oxide. Additives based on mixed oxides possess a high acidity and do not impair the activity of the catalytic system in the cracking reactions. In the efficiency (89.7–95.5%) in lowering the content of carbon monoxide, mixed oxides based on copper and cerium are comparable with the platinum-based additive KO-10 (96.8%). The activity of the additive based on manganese oxide depends on the sample calcination temperature, with the maximum efficiency in lowering the content of carbon monoxide (88.0%) reached at temperatures of 850–920°C.
[en] Spectrophotometric method was used to study the kinetics of the process in which aqueous solutions of selenurea of various compositions are oxidized. Significant differences between the stabilities of selenurea solutions were revealed in relation to the selenurea concentration and also to the acidity, or alkalinity of a medium. It was shown that the stability of selenurea solutions is affected by additives of various antioxidants: sodium sulfite Na2SO3, ascorbic acid C6H8O6, hydroxylamine chloride NH2OH·HCl, hydrazine hydrate N2H4·H2O, and tin chloride SnCl2·2H2O. It was found that using a 1 : 1 mixture of antioxidants Na2SO3 and C6H8O6 substantially raises their antioxidant activity and stabilizes the aqueous solutions of selenurea during up to five days. A hydro-chemical precipitation in the acetate—ethylenediamine reaction system in the presence of the antioxidants under study was used to obtain lead selenide films of stoichiometric composition with thicknesses of 230‒670 nm. With the Na2SO3 + C6H8O6, Na2SO3, C6H8O6, and SnCl2 antioxidants used to stabilize selenurea solutions, a tendency is observed toward a decrease in the lattice constants of PbSe films from 6.1531 ± 0.0003 to 6.1367 ± 0.0002 Å, an increase in the share of nanosize particles, and rise in the PbSe energy gap width from 0.78 to 1.0 e V.
[en] Thermochemical transformations that lead oxide used as filler in a polytetrafluoroethylene matrix undergoes in the course of heat treatment were studied. Samples were prepared from a mixture of the polymer with the filler by pressing followed by heat treatment. X-ray diffraction analysis shows that the heat treatment in air leads to multistep thermochemical reaction of the polymer with the inorganic filler with the formation of Pb2F2O and PbF2. Presumably, dispersed lead oxide particles occurring in intimate contact with the polymer, when heated in air, initiate the polymer degradation via cleavage of the C−F bond to form new compounds. Along with the formation of new compounds, the reduction of lead oxide to the metal is observed.
[en] In order to explore more efficient catalytic oxidation of commonly used polymer catalysts, cysteine as ligand and transition metal ions were used to prepare series complexes for hydrogen peroxide oxidation. Cysteine-Fe(III) was selected to serve as a catalyst for the oxidation degradation of common polymer hydroxypropyl guar gum under different pH, temperature, dosage of catalyst, hydrogen peroxide, ratio of cysteine and Fe(III), amount of H2O2. The final results showed that the temperature was 45°C, pH of 7, H2O2 added amount of hydroxypropyl guar gum was 10.0%, catalyst cysteine-Fe(III) dosage was 10% of the amount of H2O2 material, cysteine-Fe(III) the ratio was 1: 2, cysteine-Fe(III) H2O2 oxidation degradation of hydroxypropyl guar gum have good catalytic effect. After continuous degradation of 40 min, the relative viscosity of hydroxypropyl guar gum can be reduced to 81.6%, and the elimination rate of COD can reach to 97% after increasing the amount of hydrogen peroxide for 4 h.
[en] Process of chlorine removal from middle distillates with catalysts based on mesoporous materials was examined. The physicochemical characteristics of supports and catalysts based on SBA-15, Al-TUD, and MCF materials were compared. It was found that the catalyst based on MCF material can diminish the content of chlorine in a light diesel fraction to below 0.3 mg kg–1 at 360°C, pressure of 5.0 MPa, and LHSV of 2.0 h–1.
[en] Magnetic sorbent MNP@CNT was synthesized on the basis of magnetic nanoparticles of magnetite (MNPs) and carbon nanotubes (CNTs). The sorbent was studied in extraction of toxic elements from aqueous media and its synthesis conditions were optimized. Isotherms of sorption of the metal ions under study from aqueous solutions were plotted in relation to their concentrations and solution pH values. The optimal conditions for extraction of Pb(II), Cr(III), and Bi(III) at pH 6 and Cd(II) at pH 4.5–5.0 were found. It was shown that the sorption capacity of the MNP@CNT sorbent for the elements under study is comparable with the capacity of carbon nanotubes, being 4.0, 3.8, 3.5, and 3.5 mg g–1 for Bi(III), Pb(II), Ct(III), and Cd(II), respectively. An important advantage of the magnetic composite sorbent over carbon nanotubes is the simple separation of the liquid and solid phases, compared with the conventional column variation of the solid-phase extraction. The resulting composite magnetic sorbent can be used both for analytical purposes, to preliminarily concentrate impurities, and for purification of various technological media and water basins in the environment to remove toxic elements.
[en] Fylolflex oligo(resorsinol phenyl phosphate) with terminal phenyl groups is an effective plasticizer for an epoxy polymer, allowing the development of compounds with enhanced levels of physicomechanical properties, heat resistance, softening point, an flame resistance. Introduction of chromite, a cheap and active filler, into the epoxy polymer in amounts of 0.1 and 100 wt parts enhances the physicochemical and mechanical properties of the composite. Namely, the Vicat softening point increases from 132 to 140–250°С, the degradation onset temperature increases, and the yield of carbonized structures increases from 54 to 68–86 wt %, which leads to a decrease in the release of volatile pyrolysis products into the gas phase and in the combustibility of the epoxy composite.
[en] Hydrothermal synthesis was used to obtain lamellar magnetic particles of barium hexaferrite, and colloidal solutions were prepared on their basis. Magneto-optical effects in colloid solutions of barium hexaferrite were examined. It was found that the aqueous colloidal solution of coarse planar particles of barium hexaferrite is a magneto-optical medium that is nearly two orders of magnitude more effective than the colloid formed from isometric cobalt ferrite particles. It was shown that measuring the frequency dependence of the magneto-optical effects and approximating the experimental data with the Debye function makes it possible to find the frequency f0 characteristic of the given colloid and to calculate the characteristic size of particles (or aggregates) creating the optical anisotropy in the colloid under the action of a magnetic field. A dichroism is observed in the aqueous colloid formed by coarse planar barium hexaferrite particles. This phenomenon is due to the change in the light scattering on coarse particles upon their orientation by a magnetic field.