Home – Home – Jornals – Chemistry for Sustainable Development 2024 number 1

Gas chromatography with mass spectrometric detection (GC-MS) was used to study the composition of bromides obtained upon selective cleavage (chemolysis) of the C-O bond of ether/ester bridges under the action of BBr₃ in oil components from ten oil and natural bitumen samples. It is shown that most of the samples under study demonstrate the absence of mono- and dibromides of alkanes, alkylcyclohexanes, pregnanes and steranes, cheilanthanes and hopanes in the products of chemolysis. Monobromides of n-alkanes have been identified only in the products of chemolysis of oil components isolated from maltha of the Ashalchinskoye oilfield and the products of its biodegradation under laboratory conditions. In total, the identified products of selective cleavage of ether/ester bridges include mono- and dibromides of alkylbenzenes: mainly (С₁₃-С₂₂)-alkyltrimethylbenzenes, (С₁-С₇)-naphthalenes, phenanthrene, dibenzothiophene and their homologues. Monobromides of C₆-biphenyl, C₄-tetralin, dibromides of (C₂-C₆)-benzothiophenes, (C₂-C₅)-biphenyls, C₁-tetralin, fluorene, and C₂-fluorene have been also identified. Tribromides of (С₂-С₄)-naphthalenes, С₂-phenanthrene, and (С₁-С₂)-fluorenes have been identified in a limited number of samples. In chemolysis products, dibromides occur more rarely than monobromides, while tribromides are much less common than dibromides. The results obtained indicate that the above-mentioned compounds are partially present in oils as structural fragments connected with other fragments of the oil components through one or much less often through two or three ether/ester bridges. The list of structural fragments linked via ether/ester bridges, their composition and relative content differ in oil components of different oil and natural bitumen samples. Ethyl esters of aliphatic acids from C₁₂ to C₃₂, with a clear predominance of even acids and a maximum corresponding to C₁₆ and C₁₈, have been identified in the products of chemolysis of almost all samples.

The influence of pine bark pre-activation conditions - 1) in a planetary mill AGO-2, 2) with water vapor under the conditions of explosive autohydrolysis (EAH) - on the sorption activity of resulting sorbents with respect to methylene blue and gelatin was studied. It is shown that explosive autohydrolysis is a more efficient method to activate pine bark, and under certain conditions it leads to an increase in the sorption of methylene blue and gelatin at least by a factor of 1.8 and 3.8, respectively, compared with the sorbent from non-activated bark. The activating treatment of pine bark in a planetary mill makes it possible to increase the sorption of methylene blue and gelatin not more than by a factor of 1.3 and 1.2, respectively. A mathematical model is obtained that describes the effect of explosive autohydrolysis conditions (water vapour pressure and duration of pine bark treatment) on the sorption properties of the resulting sorbents. Optimal conditions providing the maximal sorption of methylene blue by the obtained sorbent are determined: temperature 155 °C; water vapour pressure 2.62 MPa; processing time 58.6 s. The sorption properties of the sorbent predicted by the mathematical model have been confirmed experimentally. Sorbents from pine bark, activated by explosive autohydrolysis, surpass the industrial enterosorbent Polifepan from hydrolytic lignin in their ability to absorb methylene blue and gelatin, which indicates the prospects for their use as enterosorbents in medicine and veterinary medicine. The results of the conducted research allow us to consider pine bark as an alternative raw material that can replace hydrolytic lignin in the production of effective enterosorbents.

The physicochemical properties and catalytic activity of regenerated spent aluminium-cobalt-molybdenum hydrotreatment catalyst have been investigated under cracking conditions in the model systems n-dodecane - toluene and decalin - toluene - n-hexane. A series of experiments to study the catalytic activity of the sample was carried out using a flow-type laboratory installation within the temperature range 430-470 °C, nitrogen pressure 1.6 MPa, liquid hourly space velocity 0.5-3.0 h^-1. The directions of transformation were determined for paraffin and naphthenic hydrocarbons by means of gas chromatography - mass spectrometry. Paraffin hydrocarbons enter into cracking, isomerisation and compaction reactions. Naphthenic hydrocarbons are transformed into the products of isomerisation, dehydrogenation and compaction. Predominant dehydrogenation of decalin with the formation of naphthalene and hydrogen is observed in the system under investigation. A positive role of hydrogen in thermodestructive processing of heavy oil residues is observed due to the hydrogenation of nonlinear olefin hydrocarbons and aromatic hydrocarbon intermediates, which decreases the rate of coke formation. The corresponding reaction rate constants were calculated, and the results were analysed. Conclusions are drawn about the prospects of introducing a regenerated spent hydrotreatment catalyst into the procedure of thermodestructive processing of heavy oil residues.

The chemical composition and reactivity of the native cellulose of cotton grass ( Eriophorum scheuchzeri ) in the production of cellulose nitroesters based on this type of raw material are investigated to assess the suitability of the native cellulose fibres of the seed pods ( Eriophorum scheuchzeri ) for the production of cellulose nitroesters on this basis. It is shown that the mass fraction of cellulose in the studied plant raw materials reaches 79 %. The degree of cellulose polymerization is 1510 units. The possibility of obtaining cellulose nitroesters in a practical yield of 64 % on the basis of this type of plant raw materials without preliminary delignifying treatment has been revealed. The chemical composition of the obtained cellulose nitroesters has been established. Their technical compliance with colloxylin H is shown. Based on the conducted studies, an intermediate conclusion is made about the potential suitability of this type of plant raw materials for the production of cellulose nitroesters.

The phase compositions and particle morphology of nanostructured Co-Pt system, obtained by the reduction of aqueous solutions of precursors with hydrazine hydrate, have been studied (for the first time in the Pt-rich region) by X-ray diffraction analysis (XRD), transmission electron microscopy (coupled with electron diffraction (ED)), thermogravimetry, small-angle X-ray scattering analysis (SAXS) and elemental analysis of the samples. As determined by XRD, with Co content less than approximately 60 at%, the only phase is determined: the face-centred cubic ( fcc ) phase of the solid solution of Co in Pt, with the upper limit of Co solubility in Pt equal to 18±1 at%. For Co content in the solid solution higher than its solubility limit during the synthesis, diffraction-undetectable phase (phases) is also formed in addition to the fcc solid solution phase. The presence of such phases was confirmed by the results of SAXS, and their metal nature, rather than oxide-hydroxide one, was confirmed by XRD, ED, and thermal analysis.

The catalytic reaction of n-heptane (n-C₇H₁₆) oxidation with molecular oxygen has been studied. Various compositions of the polymer catalyst Mn-P4VP/MBAA (where Mn-P4VP is manganese-immobilised poly-4-vinylpyridine and MBAA is N,N′-methylene-bis-acrylamide) containing 2-5 wt% Mn were prepared and tested. The concentration of manganese in the catalyst based on immobilized metal-polymer complexes is within the range of 2-5 wt% Mn. The oxidation reaction was carried out at a ratio of components n-C₇H₁₆/O₂/polymer catalyst with Mn = 1 : 3.38 : 0.003 and time 6 h within the temperature range 303-383 K. The data on the yield of the major products of n-heptane oxidation are presented, taking into account the initial components, catalyst composition, temperature and the time of oxygen contact with the reacting components. It has been established that during the oxidation of _n-C₇H₁₆ (303-383 K), the yield of alcohols is higher than the yield of other oxidation products. The oxidative conversion of _n-heptane increases from 45 to 75 mol% with an increase in temperature in the range of 303-383 K. For the multistage oxidation of n-heptane with oxygen, a kinetic model was selected and considered. On the basis of this model, the reaction rate constants were calculated in the range of 303-383 K considering the degree of heptane conversion. The activation energy of n-heptane oxidation was estimated, taking into account the method of choosing the most plausible parameter and experimental data on n-heptane convection.

Technological parameters for reforming process are chosen and optimised through an increase in temperature at the reactor inlet and increased selection of benzene-containing fraction during catalysate fractionation, which made it possible to obtain the fraction (100-200 °C), a heavy reformate of the required quality in terms of octane number - 99.5/89.5 (determined by the research/motor method, respectively), and use it as a high-octane component in the production of AI-100-K5 gasoline. Relying on the data of mathematical modelling, requirements to minimise energy consumption, and the standards for the content of aromatic hydrocarbons in commercial motor gasoline, it was proposed to increase the feedstock temperature by 1 °C at the inlet to the reformer unit reactors. A formalised scheme of hydrocarbon transformations in the reforming feedstock that occurs with an increase in process temperature is proposed, which explains the qualitative and quantitative changes in the fractional composition of the catalysate. It has been established that an increase in the extraction of benzene-containing fraction makes it possible to reduce the yield of light reformate, increase the octane number, and reduce the mass fraction of benzene to 1.5 wt% in heavy reformate. Using the Aspen PIMS programme software package, the optimal composition of AI-100-K5 gasoline was modelled, including light straight-run naphtha isomerisate, C₄ hydrocarbon fraction raffinate, high-octane gasoline component (alkylate), methyl tert -butyl ether and heavy reformate obtained under the conditions of optimized scheme. The quality of the manufactured pilot batch (MPB) of fuel fully meets the requirements of TR TS 013/2011, STO 44905015-005-2017 and the standards established for the performance properties of AI-100-K5 gasoline, determined by qualification methods and engine-bench tests. The manufactured MPB of motor gasoline AI-100-K5 exhibits improved operational and environmental characteristics, since sulphur content is reduced to 8.0 mg/kg, benzene content to 0.38 vol%, and the volume fraction of aromatic and olefin hydrocarbons to 28.6 and 4.2 vol%, respectively. As a result of motor-bench tests, it is established that AI-100-K5 gasoline has a reduced tendency to form deposits on intake valves and soot in the engine combustion chamber.

One of the main problems in oil production is the formation of stable oil-water emulsions that cause corrosion of pipelines, malfunction of pumping equipment, and poisoning of catalysts at refineries. The features of the viscosity-temperature behaviour of high-viscosity resinous crude oil from the Russkoye field (Yamal-Nenets autonomous district) and its 30 wt% emulsion after exposure to electromagnetic and low-frequency acoustic fields are investigated. Electromagnetic treatment of crude oil leads to a decrease in the phase transition temperature and the yield strength coefficient. Low-frequency acoustic processing of the emulsion is accompanied by a decrease in the effective viscosity and the yield strength coefficient. After a complex wave action, the viscosity-temperature characteristics of crude oil continue to fall, and the stability of the formed emulsions decreases due to the intense coalescence of water-phase droplets. It is shown that the amount of released asphaltenes in oil-containing systems decreases after wave treatment. On the contrary, after a complex impact, their content in crude oil increases, while in the emulsion it continues to decrease. This is likely to occur due to the release of hydrocarbons occluded in the asphaltene structure into the liquid oil phase.

Chemical modification of phenyl-formaldehyde oligomers (PFO) was carried out, and compositions based on elastomer, co-oligomer and bitumen were developed in order to achieve significant improvement of characteristics and expand the areas of PFO application. The phenol-formaldehyde oligomer was modified with carbamide by co-polycondensation in an alkaline medium. The basic physicochemical, physical-mechanical and performance characteristics of the co-oligomer were studied. The co-oligomer of the new composition, obtained at the first stage of the investigation, was used as a binder. At the second stage of investigation, a three-component composition was developed on the basis of elastomer, co-oligomer and bitumen, and a composite material was prepared. This material was shown to exhibit good protective properties, and it may be recommended to provide anti-corrosive protection of the equipment and installations in oil and gas mining industry. The effect of the amounts of introduced components on the major characteristics of the resulting composition was studied. It is shown that the introduction of a nitrogen-containing modifier (carbamide) into PFO causes a decrease in the content of free phenol and formaldehyde, which is important both from the environmental viewpoint and in relation to the hazardous action of these components on the human organism.

The kinetics and mechanism of hydrogen evolution on the MoSi₂ electrode in x M H₂SO₄ + (0.5-x ) M Na₂SO₄ ( x = 0.50; 0.35; 0.20) solutions have been studied. The cathodic polarization curves of MoSi₂ in the studied solutions are characterized by Tafel region with a slope of (-0.070)±0.002 V. The reaction order of the cathodic process with respect to hydrogen ions at the potentials of Tafel region is ~1.0; the derivative of the electrode potential with a change in electrolyte acidity is ~0.072 V. The impedance spectra of the MoSi₂ electrode in the studied potential range have the shape of a semicircle located in the capacitive half-plane, with the centre in the region of positive values of the imaginary impedance component; in the region of the highest frequencies, a short straight section is recorded on the impedance plots, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on MoSi₂, we used an equivalent electrical circuit, the Faraday impedance of which consists of series-connected charge transfer resistance ( R₁) and a parallel R₂C₂Z_d-chain responsible for the adsorption of atomic hydrogen on the surface and its diffusion into the depth of the electrode material. The equivalent circuit also includes the solution resistance (R_s) and the double layer capacitance impedance, which is modeled by the constant phase element CPE₁. It is shown that the hydrogen evolution reaction on molybdenum disilicide in a sulphuric acid electrolyte proceeds along the discharge - recombination route with a quasi-equilibrium discharge stage when the Temkin logarithmic isotherm for adsorbed atomic hydrogen is fulfilled. The hydrogen evolution reaction is complicated by hydrogen absorption proceeding in the mode of solid-phase diffusion kinetics.

Physicochemical foundations for the technology of nitrogen acid processing of serpentinite from the Karakalpak deposit with the formation of pure magnesium nitrate and magnesium-containing compound fertiliser are developed. The chemical and mineralogical composition of serpentinite from the Karakalpak deposit is studied. As determined by X-ray diffraction analysis, microscopic and thermogravimetric studies, serpentinite sample contains clinoenstatite, pyrope, spinel, magnetites and other minerals with various crystal structures. Data on the extraction of serpentinite components in nitric acid by decomposition under different conditions (temperature, duration, nitric acid concentration) are presented. The subsequent stages of nitric acid extract processing have been carried out: removal of silica residue, ammonisation of the filtrate in order to precipitate undesirable impurities to obtain magnesium nitrate. The process of evaporation and crystallization of the filtrate to obtain pure magnesium nitrate has been studied.

The content of the main groups of biologically active substances in the flowers, leaves, rhizomes of Iris setosa cultivated under the conditions of the forest-steppe zone of the Novosibirsk Region has been determined. The content of tannins, pectins, protopectins, catechins, flavonoids, carotenoids during the seasonal development of plants was determined. It is found that tannin content in the leaves in all phenophases of I. setosa plant development is 6.3-8.5 times higher than in rhizomes. During the flowering period, flavonoid content in the leaves is 29.7 times higher than in rhizomes, during the stage of blossom fading it is 18.1 times higher, and at the stage of fruiting it is 25.1 times higher. The same accumulation of catechins (0.23-0.24 wt%) was found in underground and aboveground organs during the period of blossom fading. Pectin content in leaves during fruiting was detected to be 2.4-2.7 times higher than during flowering and blossom fading. Pectin content in rhizomes is 2.2-2.4 times higher during blossom fading and fruiting than during flowering. The content of carotenoids in flowers during flowering is 2 times higher than in rhizomes, but 2.6 times lower than in leaves. It is noted that the quantitative content of biologically active substances in the organs of I. setosa is determined by the peculiarities of growth and development during the seasonal period.

Pilot-scale tests results and laboratory studies of fire-resistant hydraulic fluid based on the developed hydraulic concentrate Hydrotol-ITCh HFAE are presented. Stable operation and operating parameters preservation of the developed hydraulic fluid physicochemical properties under the real conditions on a contaminated hydraulic system of a mining industry enterprise are shown. It was found that during six months of operation, the range of pH values, electrical conductivity, concentration and bacteriological purity did not change significantly, while the concentrate refilling, as well as the use of special disinfectants and cleansers, was not required. For the first time, the microbial composition of hydraulic fluid exposed to operation in the powered supports of the enterprise was studied using the method of metagenomic sequencing. Molecular genetic methods revealed a wide range of bacterial associates with various types of metabolism, including anaerobic sulphate-reducing bacteria involved in the biological corrosion of metals.