Russian Journal of Physical Chemistry A最新文献

A model and a solution method for a plug-flow reactor with pseudo-first-order reactions are proposed. These methods make it possible to identify a dependence of the process duration and the reactor steady-state attainment time on chemical process parameters, such as reactor volume and volumetric feed flow rate. As shown by the calculated data, at least one residence time or inverse volumetric feed flow rate is required for the process to attain steady state. It is also demonstrated that, in a continuous-flow reactor, reactant concentrations always attain steady state sooner than product concentrations; also, the product transition time is independent of the reaction kinetics and is determined by the average mixture contact time within the reactor.

The equilibrium distribution of components between the Dowex 50 sulfocationite and an aqueous solution containing picolinic acid and zinc nitrate was studied. The total concentration of the zinc cation and its complex with picolinic acid in the polymer reached 1.1 M. The possibility of preliminarily calculating the counterionic composition of sulfocationite based on the equilibrium constants of binary ion exchanges and the known composition of solution is shown.

The effects of electrolyte concentration (regulated by varying the amount of ethylene glycol), temperature, and graphene size (adjusted by expanding the original graphene unit cell to different extents) on the diffusion and structure of aqueous electrolytes in graphene supercapacitors were investigated using molecular dynamics simulations. By analyzing the average number of hydrogen bonds, number density distributions, mean square displacement, and diffusion coefficients, we found that temperature and concentration significantly influence the properties of the system, while graphene size has a minimal effect. As the concentration of ethylene glycol increases, the hydrogen bonding network among water molecules is gradually disrupted, leading to a decrease in the average number of hydrogen bonds between water molecules, while the average number of hydrogen bonds between water and ethylene glycol molecules increases. Ethylene glycol demonstrates a greater propensity for hydrogen bond formation compared to water molecules. Consequently, the addition of ethylene glycol effectively protects water molecules toward decomposition via electrolysis.

The results of measurements of adsorption and structural characteristics of ASD-6 powder modified with vanadium pentoxide in different concentrations are presented; the specific surface area and porosity of the powders were calculated. With a 5% vanadium pentoxide addition, the specific surface area of ASD-6 + 5%V₂O₅ increased more than fivefold, and the porosity amounted to 0.036895 cm³/g at an average pore width of 8.2686 nm, whereas pure ASD-6 has a specific surface area of 1.1388 m²/g. Taking into account the data on the specific surface area, porosity, and the results of physicochemical analysis, optimal concentrations of vanadium hydrogel have been proposed, which make it possible to obtain dispersed systems with the required properties.

The physicochemical and transport properties of polymer films based on polyetherimides Ultem-1000 and Siltem-1700 are presented. Using the gravimetric method, the sorption, diffusion, and permeability coefficients for a number of model gases (N₂, CH₄, O₂, CO₂) were determined, and ideal selectivities for key gas pairs (O₂/N₂, CO₂/CH₄) were calculated. It was found that membranes based on Siltem demonstrate significantly higher permeability for all gases studied, but are inferior to Ultem in selectivity. The transport of water (H₂O) and ammonia (NH₃) vapors through continuous polymer films was also investigated. The water vapor permeability coefficient was 2570 Barrer for Siltem and 1720 Barrer for Ultem; for NH₃ these values were 29 and 10 Barrer, respectively. The influence of the composition of the casting solution on the transport characteristics of Ultem membranes was studied: the highest permeability values were achieved using N‑methylpyrrolidone (NMP) as a solvent. The obtained data can be used in the design of membrane systems for the separation of hydrogen-containing gas mixtures, including ammonia recovery and hydrogen purification processes within the framework of low-carbon energy.

The influence of carbon nanotubes (CNT) and graphene on the optical density of polysulfone (PSF) polymer films for radiation in the terahertz range was investigated. The influence of film thickness and nanoparticle concentration on the optical properties of composites was studied. It has been established that an increase in the concentration of nanoparticles and film thickness leads to an increase in the absorption capacity of the material. The studies of the absorption parameters of electromagnetic (EM) radiation in the terahertz (THz) range in films up to 100 µm thick showed the effect of the percolation structure of the embedded phase and the correlation of wavelengths and parameters of the composite material structures.

In the present work, synthesis, and physicochemical investigations of choline-tryptophan [Ch][Trp] based IL have been reported. The synthesized [Ch][Trp] IL was fully characterized by Fourier transform infrared (FTIR), ultraviolet (UV), fluorescence, nuclear magnetic resonance (¹H and ¹³C NMR) spectroscopy. The thermophysical properties namely density and ultrasonic velocity of the synthesized IL in aqueous medium have been monitored in the temperature range of 293.15–313.15 K at 5 K interval. Derived properties like apparent molar volume (({{V}_{phi }})), partial molar expansibility ((E_{phi }^{0})), isentropic compressibility (({{K}_{{text{S}}}})), isothermal compressibility (({{K}_{T}})), apparent molar isentropic compressibility (({{K}_{{{text{s}},phi }}})) and hydration number (({{n}_{{text{H}}}})) have been calculated.The increase in density values with rise in concentration of IL reveals that there is association between the constituents due to closeness. But as the temperature rises, the ionic mobility intensifies leading to expansion in volume and lowering of density. A decreasing trend of ({{V}_{phi }}) has been noticed at higher concentration of IL due to large engagement of water molecules in the solvation process leading to strong electrostriction and overlapping of hydration co-spheres. It has also been observed that the water molecules located in the primary hydration shells are incompressible due to electrostriction but the water molecules out of the electrostatic field are main contributors to the isentropic compressibility of the aqueous IL mixture.

The phase and isotopic equilibria between boron trichloride and its solution in perfluorodecalin have been studied. The results of experiments on saturation of perfluorodecalin with boron trichloride, performed at temperatures from 278 to 303 K, indicate high solubility of BCl₃ in perfluorodecalin, which varies from 16.09 ± 0.02 to 0.099 ± 0.007 mol BCl₃/mol perfluorodecalin. The heat of dissolution of BCl₃ in perfluorodecalin is estimated at –(4–6) kJ/mol BCl₃, which corresponds to the range of the van der Waals interaction. The single separation factor of boron isotopes during the dissolution of BCl₃ in perfluorodecalin was determined based on the results of the isotope analysis of the gas and liquid phases: α = 1.0085 ± 0.0036 and 1.0128 ± 0.0066 at 12 and 5°C, respectively.

The application of polyacrylonitrile (PAN) ultrafiltration membranes to the treatment of used engine oil (UEO) was investigated. A two-stage purification scheme was developed, comprising filtration through PAN membranes with pore sizes of 23 nm (M-20) and 4.9 nm (M-5). The results demonstrated that the M-5 membrane exhibits high permeability, 2.0 ± 0.4 L/(m² h bar), and strong fouling resistance, with toluene washing restoring up to 93% of its initial permeability. Physicochemical and elemental analyses confirmed a reduction in oxygen, sulfur, metals, and high-molecular-weight compounds. Spectroscopic studies (FTIR and NMR) revealed efficient removal of polycyclic aromatic hydrocarbons and oxidation products. The two-stage filtration system employing PAN membranes provides efficient treatment of UEO, making the proposed method promising for further industrial application.

Features and advantages of highly efficient fine-fiber filters for capturing submicron aerosol particles are discussed. Quality criteria for filters made of nanofibers and fibers coated with radial nanowhiskers with account for the gas slip effect at low and intermediate Knudsen numbers are determined.