Key words: carbon nanotubes, rapid expansion of supercritical suspensions, dispersion
The dependence of the degree of CNT deagglomeration on the multiplicity of their treatment by the method of rapid expansion of supercritical suspensions (RESS) under various conditions has been studied. It was shown that double treatment by the RESS method makes it possible to increase the degree of CNT deagglomeration more effectively than a single one. Three-fold treatment in the case of nitrogen leads to a slight increase in the degree of dispersion compared to two-fold. In the case of CO2, three-fold treatment can lead to both an increase and a decrease in the degree of dispersion compared to twofold. When nitrogen is used as a dispersion medium, changes in temperature and pressure do not lead to a change in the degree of dispersion of CNTs. When using CO2, a decrease in fluid density ensures greater efficiency of CNT processing.
doi:10.34984/SCFTP.2023.19.2.002
Cite
ГОСТ
7.0.100-2018
Dispersion of carbon nanotubes using multiple rapid expansion of supercritical suspensions / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 16-26. - DOI: 10.34984/SCFTP.2023.19.2.002
TRANSLIT
Dispergirovanie uglerodnyh nanotrubok metodom mnogokratnogo bystrogo rasshireniya sverhkriticheskih suspenzij / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 16-26. - DOI: 10.34984/SCFTP.2023.19.2.002
En
Dispersion of carbon nanotubes using multiple rapid expansion of supercritical suspensions. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 16-26 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.002
Key words: supercritical carbon dioxide, betulin, solubility, co-solvent, equation of state
The results of experimental investigation of betulin solubility in pure and modified supercritical carbon dioxide in the range of temperature (313.15 -333.15 K) and pressure (8.00-30.00 MPa) using the dynamic method are presented. It was found that in pure supercritical carbon dioxide betulin does not dissolve but only swells. The addition of 5 %
ethanol as a co-solvent increases the solubility. The pressures corresponding to the first
and second crossover points of - (7.7-8.3) MPa and -(27.1-27.6) MPa, respectively,
are established in this work. The results of the descri ption of the experimental data using
a model based on the Peng-Robinson equation of state are presented.
doi:10.34984/SCFTP.2023.19.2.001
Cite
ГОСТ
7.0.100-2018
Solubility of betulin in supercritical CO<sub>2</sub><br> and CO<sub>2</sub> + ethanol mixture / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 6-15. - DOI: 10.34984/SCFTP.2023.19.2.001
TRANSLIT
Rastvorimost' betulina v sverhkriticheskom CO<sub>2</sub> i v smesi CO<sub>2</sub> + etanol / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 6-15. - DOI: 10.34984/SCFTP.2023.19.2.001
En
Solubility of betulin in supercritical CO<sub>2</sub><br> and CO<sub>2</sub> + ethanol mixture. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 6-15 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.001
Key words: adsorption, palladium hexafluoroacetylacetonate, hypercrosslinked polystyrene, aluminum oxide, supercritical fluid
The paper discusses the adsorption of palladium hexafluoroacetylacetonate (Pd(hfa)2) onto porous carriers (γ-Al2O3 and hypercrosslinked polystyrene) in supercritical CO2 to obtain supported palladium catalysts. The transition conditions of the Pd(hfa 2/CO2 system into the single-phase region have been studied. It is shown that due to the sufficiently high solubility of the palladium precursor in CO2, its deposition can be carried out at relatively low pressures in the system (- 8,5 MPa). The adsorption of Pd(hfa)2 on chosen carriers can be well characterized by the Langmuir equation. The system pressure increase under isothermal conditions negatively affects the amount of adsorbed precursor, due to the competitive CO2 adsorption and the distribution shift in the system. The system temperature increase under isochoric conditions leads to an increase in the adsorption limit.
doi:10.34984/SCFTP.2023.19.2.003
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ГОСТ
7.0.100-2018
Deposition of palladium hexafluoroacetylacetonate on porous matrices by adsorption in a supercritical CO<sub>2</sub> / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 27-43. - DOI: 10.34984/SCFTP.2023.19.2.003
TRANSLIT
Adsorbcionnoe nanesenie geksaftoracetilacetonata palladiya na poristye matricy v srede sverhkriticheskogo CO<sub>2</sub> / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 27-43. - DOI: 10.34984/SCFTP.2023.19.2.003
En
Deposition of palladium hexafluoroacetylacetonate on porous matrices by adsorption in a supercritical CO<sub>2</sub>. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 27-43 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.003
Key words: aerogel, germanium oxide, praseodymium, soakage, impregnation, luminescence
An easy-to-implement technique for obtaining REE-doped GeO2 aerogels is proposed. Optimal synthesis conditions have been determined to achieve a uniform distribution of the ion-dopant in the matrix. The effect of praseodymium on the luminescent characteristics of GeO2 aerogels when excited by radiation with wavelengths of 240, 255 and 390 nm has been established.
doi:10.34984/SCFTP.2023.19.2.004
Cite
ГОСТ
7.0.100-2018
Synthesis of pr-doped GeO<sub>2</sub> aerogels by impregnation method / – Текст : // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 44-58. - DOI: 10.34984/SCFTP.2023.19.2.004
TRANSLIT
Sintez GeO<sub>2</sub>-aerogelej, legirovannyh prazeodimom, metodom propitki / – Tekst : // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 44-58. - DOI: 10.34984/SCFTP.2023.19.2.004
En
Synthesis of pr-doped GeO<sub>2</sub> aerogels by impregnation method. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 44-58 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.004
Key words: critical phenomena, paired correlation function, scale transformations, scale invariance, optical diagnostics of the critical state of fluids
In this paper we have solved the «fluctuation theorem» on the mesoscopic length scale for the first time in a direct way. An analytical expression for the pair correlation function of the critical state of fluid was obtained, where the density variance is the parameter that could be easily defined by optical measurements. By comparison of our result with the Ornstein—Zernike pair correlation function we have got the Fisher index η= 0.25 to increase the convergence. It was shown that the obtained results provide a reliable theoretical basis for optical diagnostics of the critical state of fluids.
doi:10.34984/SCFTP.2023.19.2.005
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ГОСТ
7.0.100-2018
Pair correlation function for equilibrium critical state of fluids on the mesoscopic space scale / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 59-81. - DOI: 10.34984/SCFTP.2023.19.2.005
TRANSLIT
Parnaya korrelyacionnaya funkciya ravnovesnogo kriticheskogo sostoyaniya flyuidov v mezoskopicheskom masshtabe dlin / – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 59-81. - DOI: 10.34984/SCFTP.2023.19.2.005
En
Pair correlation function for equilibrium critical state of fluids on the mesoscopic space scale. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 59-81 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.005
Key words: hydrolysis lignin, depolymerization, n-hexane, supercritical conditions, hydrogenation, Ru/C
Depolymerization of hydrolysis lignin in supercritical n-hexane medium was carried out in two stages: 1) lignin treatment in an autoclave at 250°C and 15 MPa; 2) hydrogenation of the solution obtained in the first stage at 250°C and 9 MPa on a Ru/C catalyst. The products of the first and second stages were analyzed by HPLC, GPC, gas chromatography, chromatography-mass spectrometry, and elemental analysis. At the first stage, the degree of depolymerization was 17 %, the mono- and oligomeric fragments of lignin that passed into solution as a result of depolymerization have an MMD from 65 Da to 270 kDa. Monomer composition of the solution: mono-, di-, tri- and tetraalkyl derivatives of benzene (2.8 wt. %), guaiacol and its alkyl derivatives (0.6 wt. %), including coniferyl alcohol (0.06 wt. %). At the second stage of transformation the following processes occur: 1) depolymerization of oligomers to monomers; 2) hydrogenation of monomeric phenols to derivatives of cyclohexane and its oxo derivatives; 3) formation of gas products, mainly methane (95 vol. %), as a result of hydrocracking of the solvent.
doi:10.34984/SCFTP.2023.19.2.006
Cite
ГОСТ
7.0.100-2018
Two-stage thermal and heterogeneous catalytic transformation of hydrolysis lignin in supercritical <i>n</i>-hexane / – Текст : непосредственный // Сверхкритические Флюиды: Теория и Практика.. – 2024. – Т. 19. – № 2. – С. 82-94. - DOI: 10.34984/SCFTP.2023.19.2.006
TRANSLIT
/ – Tekst : neposredstvennyj // Sverhkriticheskie Flyuidy: Teoriya i Praktika.. – 2024. – Т. 19. – № 2. – S. 82-94. - DOI: 10.34984/SCFTP.2023.19.2.006
En
Two-stage thermal and heterogeneous catalytic transformation of hydrolysis lignin in supercritical <i>n</i>-hexane. Sverhkriticheskie Flyuidy: Teoriya i Praktika, 2, 82-94 (2024). https://doi.org/10.34984/SCFTP.2023.19.2.006