French-Ukrainian Journal of Chemistry
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The impact of oxidiser humidity on methane combustion in a gas burner
Get PDFThe improvement of thermodynamic and environmental indicators of energy facilities is a vital and topical problem. Numerical simulation methods are used to investigate the processes of combustion and formation of hazardous substances by computation, and to work out recommendations on increasing the effectiveness of fuel combustion. The paper examines the impact of atmospheric air humidity on the process of combustion of a stoichiometric methane-air mixture in a burner. The combustion process is simulated in the 3D unsteady statement in Cartesian coordinates. In the investigation, the combustion of the methane-air mixture is considered in one stage. Air humidity is considered in the 0 to 100% range. The monoxide nitrogen formation process is described using the extended Zeldovich-Fenimore mechanism. A comparative study has found that increasing air humidity up to 100% reduces the mass emission of monoxide nitrogen by a factor of 1.27, as compared to dry air. The study results can be used for designing equipment that uses methane as fuel
Synthesis of 2-(1,2,4-oxadiazol-5-yl)-2,3-dihydro-4H-chromen-4-ones
Get PDFSimple and efficient synthesis of 2-(1,2,4-oxadiazol-5-yl)-2,3-dihydro-4H-chromen-4-ones is elaborated. The method relies on CDI-mediated cyclocondensation of substituted 4-oxochromane-2-carboxylic acids and amidoximes. The protocol allows the preparation of 2-oxadiazolylchromanones decorated with two pharmacophores (2,3-dihydro-4H-chromen-4-one and 1,2,4-oxadiazole) that are in high demand in drug discovery
Structures and properties of three new homobinuclear nanosized supramolecular copper coordination polymers derived from carboxylate type ligands and benzimidazole
Get PDFThree new homobinuclear nanosized supramolecular copper coordination polymers are hydrothermally synthesized by self-assembly reaction of L-tyrosine (Tyr), terephthalic acid (H2bdc), pyromellitic acid (H4btec) and benzimidazole (Hbzim) with copper chloride salt to generate with formula [[Cu2(tyr)2(bzim)2(Cl)2(H2O)2]]n 1, [[Cu2(bdc)2(bzim)2(H2O)6].3H2O]n 2 and [Cu2(H2btec)(bzim)(H2O)6].2H2O]n 3, which have been investigated by elemental analysis, molar conductivity and magnetic measurements, FT-IR and UV-Vis spectroscopy, (TGA/DTA) thermal analysis and X-ray powder diffraction(XRPD) analysis as well as MM2 theoretical calculations. The magnetic moment and electronic spectra of the complexes are certainly indicating the octahedral geometries. Thermal analysis of the complexes confirms the suggested structures and thermal stability. The results of the XRPD analysis and the average nanosized values of the complexes have nanosized supramolecular polymers in the triclinic system. The MM2 theoretical calculations are supported by the proposed structures
Concentration and sources of polycyclic aromatic hydrocarbons in some commercial herbal drugs used for cholera treatment in southwest Nigeria
Get PDFThe aim of this study was to investigate the cancer risk that could be incurred from the use of some anti-cholera herbal drugs sold in Southwest Nigeria. Three most popular anti-cholera herbal drugs were studied. The cancer risk estimation for the drugs at studied population ranges from 7.119 to 0.338 x 10-8 in children, 9.563 to 0.129 x 10-8 in preteen and 9.541 to 5.196 x 10-8 in adult. The cancer risk estimated values are below the USEPA set value 1 x 10-6. This established that the use of these herbal drugs might not lead to cancer if consumed at low dosage
Solid gas and electrochemical hydrogenation properties of the selected R,R’MgNi4-xMx (R,R’ = La, Pr, Nd; M = Fe, Mn; x = 0.5, 1) alloys
Get PDFNew R,R’MgNi4-xMx (R,R’ = La, Pr, Nd; M = Fe, Mn; x = 0.5, 1) phases with cubic structure have been synthesized by powder sintering method. By the hydrogenation of the parent alloys seven hydrides with cubic (LaMgNi3.5Fe0.5H6.0, PrMgNi3.5Mn0.5H~6 and NdMgNi3.5Mn0.5H~5) and orthorhombic (PrMgNi3.5Fe0.5H4.5, NdMgNi3.5Fe0.5H4.3, La0.5Pr0.5MgNi3.5Fe0.5H4.6 and La0.5Nd0.5MgNi3.5Fe0.5H4.4) structures were obtained. The relationship between the structure, hydrogen content and the relative increase of the lattice volume of the new and early known hydrides is shown. Electrochemical parameters of the electrodes based on new materials are compared with already known ones. Highest discharge capacity is observed for PrMgNi3.5Mn0.5 (271 mAh/g) and NdMgNi3.5Mn0.5 (263 mAh/g). The best cyclic stability was seen for the electrode based on NdMgNi3.5Fe0.5 (S50 = 74%)
Thermochemical activation of hydrogen in the process of desorption from metal hydride
Get PDFThe results of mass spectrometric studies of the energy state of hydrogen molecules with the usage of the electron impact ionization efficiency curves measurement method, both during desorption and in the mode of hydrogen flowing through the metal hydride layer, are presented. The dependences of the breakdown voltage on the pressure in the gas-discharge chamber for an electric discharge in activated hydrogen are obtained. Those dependencies indicate a significant decrease in the ionization potential of hydrogen under the electric current influence. Within the framework of the presented material, the results of hydrogen emission from hydride-forming materials based on LaNi5 are presented and an assessment of its thermodynamic state is given, which made it possible to study the energy-physical characteristics of gas-discharge processes. The possibility of practical use of metal hydride activation to increase the energy and operational efficiency of electric-discharge hydrogen systems is shown
Modified fine-grained concrete for floor heating system
Get PDFThis work shows the influence of components and hardening conditions on linear shrinkage of fine-grain concrete. The floor heating system is one of the most popular options of the heating system these days. The possibility of using this composition for screed for floor heating system is shown. A method of enhancing of strength of the concrete by adding reinforcing fibers and plasticizer has been suggested. Concrete composition has been optimized
Structure and properties of polymer composite based on natural zeolite
Get PDFThis research paper is dedicated to the possibility of expanding directions and increasing the use of natural zeolite as filler (65 – 85 %) for the manufacture of composite material. The structure of composites with varieties of copolymers (Styrene- butadiene, Styrene-acrylate) and revealed the features of the structure (open porosity 5 - 24 %) and material properties of the zeolite concentration are identified
Humic-like acid derived from 1,2-naphthoquinone
Get PDFA new fast and original method for producing synthetic humic acids by oxidation of 1,2-naphthoquinone by oxygen in an alkaline medium has been proposed. The elemental, structural-group composition and spectral characteristics of the obtained humic-like substances correspond to those of natural humic substances. The stoichiometry of the reaction was established by the volumetric method. The redox capacity of humic acids increased from 0.43 to 3.68 mmol∙g-1 with increasing solution from pH 5 to 11. Humic-like acids featured an ESR singlet signal with a width of 3.8 Gauss and g-factor close to the g-factor of the free electron (g = 2.0033)
Development of Extraction Method of Polycyclic Aromatic Hydrocarbons from Sunflower Oil
Get PDFPolycyclic aromatic hydrocarbons (PAHs) adsorption extraction process from sunflower oil on activated carbon was studied. Specific adsorption values on activated charcoal-xenobiotic system for compounds of benzo(a)anthracene, benzo(a)pyrene, benzo(e)pyrene, chrysene, benzo(b)fluoranthene and their mixtures were investigated. Influence of phase contact time of system, ratio of components on degree of PAHs extraction under isothermal conditions (25 ± 0.01ºC) was studied. Degree of oil purification was controlled by method of high performance liquid chromatography with fluorescence detector (HPLC/FLD). Leaning on patterns found, optimal conditions for purification of raw sunflower oil from PAHs using activated charcoal and obtaining the matrix of sunflower oil proposed