Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 2

The data on liquid-phase oxidation of acylcyclohexanes by air oxygen in the presence of transition metals (Co, Cr, and Ni) naphthenates are presented. Their physicochemical, thermogravimetric, and spectral characteristics are examined. The introduction of cobalt naphthenate into the system leads to a significant drop in the yield of naphthenic acids, but the content of oxyacids increases significantly (more than 30 %), as established. To achieve the maximum yield of naphthenic acids, the optimum content of chromium naphthenate is 0.2, while that of oxy-naphthenic acids, cobalt naphthenate concentration is 0.3 mass %.

High-silica ZSM-5-type zeolite with silica module of 40 was produced by hydrothermal synthesis using hexamethylenediamine as a structure-forming additive. Its belonging to the pentasyl family and crystallization degree were determined by IR spectroscopy and X-ray phase analysis. Metal-containing zeolite catalysts were prepared by mechanical mixing of zeolite with powders of nickel and zirconium with medium particle size of 50 nm and those of rhenium with that of 770 nm in terms of 0.5 mass %. The specific surface area of samples and parameters of their porous structure were determined by BET according to low-temperature nitrogen adsorption, acidic characteristics - by temperature-programmed ammonia desorption. It was demonstrated that the introduction of metals into zeolite reduced its specific surface area and acidity. Catalytic activity of metal-containing zeolites was studied during transformation of propane-butane fraction and n -heptane. It was found that during their joint transformation over unmodified zeolite, the yield of the liquid product and the content of isoalkanes therein were higher than in case of conversion of only n -heptane. The addition of metals to zeolite led to a decrease in the concentration of n -alkanes, arenes, and alkenes in the resulting liquid products over catalysts and to a simultaneous increase in the fraction of iso- and cycloalkanes therein. Modification of zeolite with rhenium and zirconium increased formation selectivity of isoalkanes, while the introduction of nickel - that of aromatic hydrocarbons. The resulting zeolites might be used as the main component of catalysts for gentrification of the straight-run gasoline fraction of oil and during its joint conversion with hydrocarbon gases.

Thermal solvolysis of thermoreactive polymers in coal tar medium was examined at 360-420 ºС. The cured epoxy diane resin ED-20 and industrial samples of polymer binder based thereon that is part of polymeric composite materials were used as polymers. The composition of liquid products of solvolysis was determined using GC-MS. It was found that coal tar had an effect on the yield and composition of decomposition products of thermoreactive polymers during thermal solvolysis. Characteristics of coal tar were determined after treatment of polymers therein.

Ceramic materials with a density of more than 95% of theoretical containing 1-30 mass % of iron oxide were synthesized in the Al₂O₃-Fe₂O₃ system. During ceramics air sintering, the material with Fe2O3 content below 10 % is monophase and comprises of α-Al₂O₃-based solid solution. With Fe₂O₃ concentration above 10%, iron oxide-based solution is generated in significant amounts. As soon as the material becomes two-phase, the value of its electrical conductivity increases by three orders of magnitude and reaches 10^-8-10^-9 Sm/m. Iron oxide is reduced to metal when trying to increase material density by vacuum sintering or hot isostatic pressing. Furthermore, a composite representing uniformly distributed spherical metallic iron particles in the α-Al₂O₃ matrix is generated.

For the first time, there were offered consecutive stages of algorithm solution, such as phenolic antioxidants in the improvement of mechanical properties of polymers. The first step begins with studies of thermokinetic characteristics of thermolysis reactions of phenolic antioxidants accompanied by determination of their kinetic constants (activation energy, E and pre-exponents, Z). Modifiers of the main group of antioxidants can be distinguished according to the ratio of these constants. Polymer modification effect by them was determined at the second step. It appears in a temperature of the beginning of modifier decomposition under polymer thermal processing conditions. Furthermore, parameters of an increase in product service time under extreme operating conditions were defined. Examples are given of modification and stabilization of properties of polymer-derived composites

Rare metal ores of the Chuktukon deposit (Krasnoyarsk Territory) were explored. It was found that the ores were complex, mainly of iron-manganese composition (iron oxides content of 50% or above), with high contents of lanthanides, yttrium, niobium, vanadium, zinc, and phosphorus. The main mineral forms of rare earth metals are monazite and florencite, of niobium - barium-strontium pyrochlore. As demonstrated by granulometric composition study, above 50 % of ore mass is presented by a particle size of mainly 1-2 µm and ~12 µm. As a rule, elements are almost evenly distributed according to all size grades. According to microscopic study results, the ore is mainly formed by ultrafine micrometre-sized particles (the first micrometres) that, in turn, are nanoscale particle aggregates. The findings explain the complexity of excreting concentrates of rare earth metals and niobium from the ore using enrichment methods.

The causes and ways of reducing losses of zirconium and other rare elements with silica residues upon acid treatment of eudialite concentrate, i.e. a raw source of zirconium, hafnium, and rare earth elements of the middle and yttrium groups, were explored. Metals distribution was examined during acid treatment with 2 mass % solutions of nitric and sulphuric acids in the presence of sulphocationite. It was found that decomposition of the eudialite, the main Zr-containing mineral, proceeded entirely. Herewith, losses of zirconium and other rare elements with silica residues formed during nitric acid and sulphuric acid processing of eudialite concentrate are mainly related to their ingress to silica gels. Rare elements are present therein as bridges of hydrated silica-based polymers that are bridge-coupled by hydroxyl (olation) or oxygen (oxyolation). As demonstrated, zirconium and other elements may be additionally derived by acid treatment. Their losses with silica residues may be reduced during eudialite concentrate decomposition in the presence of sulphocationite with sol production in the initial stage.

An efficient mechanochemical method for producing composites based on LLDPE 6101RQ polyethylene and inorganic additives was investigated. Films with improved barrier and mechanical properties were produced therefrom. In obtaining films without master-batches, the content of additives (TiO₂, CaCO₃, SiO₂, or Na-montmorillonite) was 0.01-5 %. Herewith, gas permeability reduced to 30-50 %; modulus of elasticity (along) increased by 24-60 %, strength - by 15 %.

Natural and technogenic sources of mercury ingress to into ecosystems of Gorny Altai were characterised. The content of mobile Hg forms in polluted soils was determined and its inverse dependence on the gross content of mercury in the soil was revealed. The limited nature of migration of mobile forms of mercury from polluted soils was demonstrated. The main thermoforms of mercury in conditionally background and anthropogenically polluted soils were preliminarily found. Data on levels and forms of its occurrence in components of water ecosystems are presented. Features of their changes in different hydrological periods, and also during the water transfer are revealed. Quantitative characteristics of transfer of various forms of mercury coming from the industrial zone of the Aktash mining and metallurgical enterprise were assessed. A progressive decrease of their content in the waters that transmit pollution of rivers of the fifth-second orders (Yarlyamry, Chibitka, Chuya, and Katun) was shown.

The results of exploring cracking of high-sulphur bitumen (sulphur content of 3.7 %) from the Mordovo-Karmalskoye field with a mass content of fractions boiling out to 200 °C of 6.7 % are presented. The yields of gaseous, liquid, and solid products were determined at 450 °C and process time of 60-120 min. The hydrocarbon composition of liquid products from cracking was analysed. The effect of bitumen thermal treatment length on changes in molecular structures of high molecular mass heteroatomic compounds (resins and asphaltenes) was investigated. It was found that at cracking time of 100 min, molecules of asphaltenes of bitumen from the Mordovo-Karmalskoye field became larger due to an increase in the number of naphthenic rings. Whereas at 120 min, asphaltenes decomposed and got more aromatized.

Using gas chromatography-mass spectrometry (GC-MS), there was explored the composition of organic compounds in snow samples collected in the territory of Tomsk region in areas with diverse technogenic load: at the oilfield, in the forest-park area of the city of Tomsk (Academgorodok), and in wetlands remote from anthropogenic sources. In snow pack samples, there were determined the following components: alicyclic and aromatic hydrocarbons, normal aliphatic acids and their esters, acyclic and aromatic ketones, aldehydes, terpenes, phenols, orthophosphoric acid esters, furans, and thiophenes. According to the results of analysis of the composition of the organic compounds identified, sources of their entry to snow pack (biogenic and anthropogenic) were revealed.

Selection of the optimum synthetic path to the active ingredient for any drug is a complex task. The lack of computational methods for performance assessment of chemical transformations does not allow evaluating the proposed synthesis options and efficiently using computational methods in their development. The method of quantification of syntheses efficiency considering changes in structural complexity of organic compounds, reaction conditions and results is developed.

A thermogravimetric study of vitrinites of bituminous coals of different metamorphic stages was carried out in the oxidizing medium. It was demonstrated that with increasing the metamorphic grade of vitrinites, the temperature range of the oxidation process rose, while the maximum decomposition rates were shifted to higher temperature region. A strong correlation of the ignition temperature of vitrinites and organic (С^daf) and aromatic (С_ar) carbon content therein, and also of vitrinite reflectance values (R_o,r) and volatile matter yield (V^daf) was revealed.

Composition and structure changes of the macromolecules of asphaltenes from the Usinsk deposit were studied during sequential stepwise thermal decomposition at 120, 230, and 370 °C. Component composition data of thermolysis products were acquired and changes in structural-group characteristics of asphalthene molecules during thermal treatment were described. It was found that below 230 °С, asphaltene decomposition reactions prevailed over condensation ones, while above this temperature, compaction reactions were prevalent. It was demonstrated that the trend of heteroatoms towards accumulation in compaction products during stepwise thermolysis of oil asphaltenes from the Usinsk field increased in the series S → N → O.