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2024, №4

pp. 3-24

Reviews

Application of Supercritical Fluids for Separation of Group Components of Petroleum Systems (Review)

A.V. Pripakhaylo, R.N. Magomedov, L.S. Foteeva, O.V. Shapovalova.

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Key words: supercritical fluids, group composition, asphaltenes, supercritical fluid extraction, carbon dioxide, anti-solvent, fractionation

The review article examines information on modern methods of separating oils and oil residues in the analysis of group composition using supercritical fluids. The features of the influence of the composition and properties of individual group components of oil samples on further processing has been shown. Traditional methods of separating petroleum feedstock into group components has been briefly reviewed. The results of modern studies of extraction methods for separating oil samples using supercritical fluids has been shown. Information is presented on new methods for the extraction of asphaltenes and fractionation of heavy oils and oil residues using СО2.

doi:10.34984/SCFTP.2024.19.4.001

2024, №4

pp. 25 - 43

Articles

Synthesis, Structure and Catalytic Properties of Mixed Ln—Al Oxides (Ln — La, Ce, Pr) in the Oxidative Coupling of Methan

P.R. Vasyutin, M.Yu. Sinev, E.Yu. Lyubimov, Yu.A. Gordienko, Yu.D. Ivakin, E.A. Lagunova, V.Yu. Bychkov, M. Todoroki.

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Key words: mixed oxides, synthesis, water fluid, rare-earth elements, aluminates, catalytic oxidation, oxidative coupling of methane

The effect of the synthesis method of mixed Ln—Al (Ln — La, Ce, Pr) oxide systems with the atomic ratio Ln : Al = 1 : 1 on the formation of their phase composition and catalytic properties in methane oxidation were studied. The precursors were prepared by impregnation of ashless filter paper with mixed solutions of nitrates of the corresponding metals according to the water absorption capacity, followed by drying and combustion of the obtained mass in air. Further processing was carried out by combining calcination at 600 and 900 °C with treatment in water or water-ammonia fluid (WF, WAF) media. The patterns of the amorphous precursor of Pr-Al oxides transformation in the WF and WAF media and during high-temperature synthesis are similar to those obtained for the La—Al system. In both cases, the amorphous precursor in the water-containing fluid transforms into LnAlO3 with a cubic perovskite structure with an admixture of AlO(OH) (boehmite) and basic REE carbonate phases. The subsequent treatment at 900 °C in air leads to the formation of mixture containing aluminates LnAlO3 and free oxides La2O3 or PrO2. Single-phase samples containing only La and Pr aluminates were obtained by heating the amorphous precursors at 900 °C in air. During the treatment in the watercontaining fluid medium of the Ce—Al system, well-crystallized oxide CeO2 instead of aluminate or Ce-containing hydroxides is formed, and the Al-containing component remains X-ray amorphous. CeAlO3 was obtained by treating the mixture of Ce and Al oxide precursors in a hydrogen stream. It has been established that due to the differences in the values of the 4th ionization potential (IP 4) of La, Ce and Pr atoms (49.9, 36.7 and 39.0 eV, respectively), very different synthesis conditions are required for the formation of perovskite-type aluminates of the LnAlO3 formula containing the REE in the (3+) oxidation state. The catalytic properties of the synthesized samples in methane oxidation have been studied. The efficiency and stability of isostructural aluminates LnAlO3 in the oxidative coupling of methane (OCM) decreases in the La > Pr ≫ Ce series. While PrAlO3 is the most active among them, LaAlO3 shows the highest selectivity in the formation of the OCM products (ethane + ethylene).

doi:10.34984/SCFTP.2024.19.4.002

2024, №4

pp. 44-61

Articles

Dynamics of Water Transition to Supercritical State Under Ultra-Fast Heating by Ultra-Short Laser Pulses

E.I. Mareev, N.M. Asharchuk, V.V. Rozenko, V.I. Yusupov.

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Key words: supercritical water, molecular dynamics, interaction of laser radiation with matter

The dynamics of femtosecond laser action on water was experimentally studied and reconstructed using numerical modeling based on the classical molecular dynamics method in combination with a two-temperature model and dynamic rate equations. This process occurs in several stages: initially, a femtosecond laser pulse interacts with the electron subsystem, generating plasma due to multi photon, tunnel and impact ionization. The energy transfer from plasma electrons to atoms, as shown using the two-temperature model, leads to ultra-fast heating of the substance to a temperature about 10,000 K, and the pressures achieved in the area of action are about 15 GPa, which leads to the generation of a shock wave. The excess of temperatures and pressures over critical values in combination with high density fluctuations and clustering allow us to assert the transition of the substance to a supercritical state. Pressures and temperatures exceeding critical values are achieved in a region slightly exceeding the cavitation region, and this region experiences oscillations with a period close to the period of oscillations of the cavitation bubble. It is shown that in the case of femtosecond laser action, the specific energy input measured experimentally can be immediately used as initial conditions, assuming instantaneous heating of the medium, which significantly simplifies numerical modeling. Within the framework of this approach, both the pressures achieved at the shock wave front and the dynamics of cavitation bubbles are successfully reconstructed.

doi:10.34984/SCFTP.2024.19.4.003

2024, №4

pp. 62-73

Articles

Modeling the Solubility of Palladium Hexafluoroacetylacetonate in Carbon Dioxide

M.O. Kostenko, A.L. Voskov, Y.I. Zuev, M.A. Kurykin, O.O. Parenago.

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Key words: palladium hexafluoroacetylacetonate, carbon dioxide, solubility, Peng— Robinson equation of state, Chrastil equation

The paper considers two approaches for modeling the solubility of palladium hexafluoroacetylacetonate in carbon dioxide under sub- and supercritical conditions based on previously collected experimental data. The first approach uses the Peng—Robinson equation of state, while the second uses the Chrastil equation as an alternative. During the study, optimal parameters for the model equations were determined. Both modeling approaches allowed for a satisfactory approximation of the solubility isotherms within the temperature range of 313—353 K and a molar fraction of the complex of up to 0.8%. Standard deviations for the Peng—Robinson and Chrastil models were 2.6 and 2.0 g/l, respectively.

doi:10.34984/SCFTP.2024.19.4.004

2024, №4

pp. 74-92

Articles

Supercritical Water Co-oxidation of Poultry Manure and Brown Coal in the Flow Mode

O.N. Fedyaeva, S.A. Alekhin, S.V. Morozov, M.Ya. Sokol, D.O. Artamonov, A.V. Shishkin, A.A. Vostrikov.

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Key words: poultry manure, brawn coal, supercritical water oxidation, heat evolution, contaminants

The results of joint supercritical water oxidation (SCWO) on the poultry manure (PM and brown coal (BC) mixtures continuously fed as a NaOH stabilized (0.8 wt. %) slurry into a tubular reactor at 25 MPa, temperature gradient along its vertical axis of 390— 600 °C, varied reactant flow rate and concentrations of PM and BC in the slurry are presented. The addition of BC leads to the 1.5—1.8-fold reduction of the total energy consumption by ohmic heaters depending on the content of combustible matter in the slurry. The forming gas mixture contains CO2, N2, and trace amount of N2O. Calcium and sodium carbonates, phosphates, and aluminosilicates are dominated in the composition of ash residues. The total content of phenols (17—32 μg/dm3) and polycyclic aromatic hydrocarbons (2—4 μg/dm3) in the effluent depends on the PM concentration in the slurry and does not exceed the level of their maximum permissible concentration in wastewater. The formation of HNO3 and H2SO4 during the SCWO process results in corrosion of construction materials and increases the content of chromium, copper and nickel in the aqueous effluent. The mechanisms of transformation of organic and mineral components of PM and BC are discussed.

doi:10.34984/SCFTP.2024.19.4.005

2024, №4

pp. 93-106

Articles

Equilibria in the System Copper Hexafluoroacetylacetonate—СO2—Al2O3

M.O. Kostenko, Y.I. Zuev, A.A. Ovechkina, M.A. Kurykin, O.O. Parenago.

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Key words: adsorption, solubility, copper hexafluoroacetylacetonate, γ-alumina, supercritical fluid.

The data on the solubility of copper(II) hexafluoroacetylacetonate monohydrate Cu(hfa)2⋅H2O in carbon dioxide. The solubility increases with increasing temperature in the range of 303—353 K and a nonlinear increase in the solubility of Cu(hfa)2⋅H2O with increasing CO2 density in the supercritical (SC) range of parameters is observed. The dependence of solubility on the parameters of state (temperature, CO2 density) was described by the Chrastil equation. Adsorption of Cu(hfa)2⋅H2O from its solution in SCCO2 on three samples of γ-Al2O3, differing in the presence of acidic and basic additives, is studied. The adsorption isotherms have a shape characterized by a sharp rise in adsorption at the initial section. This shape indicates a high affinity of the complex to the carrier surface and/or its heterogeneity and the presence of high-energy adsorption centers. An increase in the CO2 density from 355 to 780 kg/m3 at a constant temperature (313 K) leads to a decrease in the adsorption of Cu(hfa)2⋅H2O on all three alumina samples. At the constant density of the medium 355 kg/m3 and the temperature rise from 313 to 343 K, a more complex behavior of the isotherms depending on the carrier characteristics and the range of concentrations of the adsorbed substance is observed.

doi:10.34984/SCFTP.2024.19.4.006

2024, №4

pp. 107-121

Articles

Dynamics of Submicron Gold Particle Formation During Laser Ablation in Supercritical Carbon Dioxide

E.O. Epifanov, N.M. Asharchuk, D.N. Hmelenin, I.V. Trofimov, A.O. Rybaltovskij, G.V. Mishakov, T.A. Semenov, N.V. Minaev, E.I. Mareev.

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Key words: laser ablation, plasmonic nanoparticles, supercritical fluid, supercritical carbon dioxide, Mie Scattering

The dynamics of submicron gold particle formation during laser ablation in supercritical and liquid CO2 have been investigated using time-resolved Mie scattering absorption spectroscopy. It was found that a high density of CO2, approximately 800 kg/m3, regardless of the phase state, leads to the formation of laser-induced medium fluctuations on time scales of 10 to 1000 microseconds, during which the defocusing of subsequent laser pulses may occur. Under conditions of reduced fluid density in the vicinity of the Widom region (P = 8.5 Мра, T = 310 K), it was demonstrated that nanoparticles can leave the interaction zone unhindered, as evidenced by the exponential increase in integral absorption. Data from the absorption spectra allowed for the observation of nanoparticle formation dynamics, with an average diameter of approximately 160 nm and log-normal size.

doi:10.34984/SCFTP.2024.19.4.007

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