Russian Journal of Physical Chemistry A最新文献

In this work, we use molecular dynamics (MD) method to calculate the monomeric and competitive absorption behavior of six nuclear-industrial elemental gases: H₂, N₂, I₂, Ar, Kr, Xe in the lanthanide-based MOF (Nd-MOF: {[Ln₂(IDA)₃]⋅(H₂O)₂}_n (Ln = Nd; H₂IDA = iminodiacetic acid). Subsequently, the density functional theory (DFT) is employed to calculate the electronic density difference of MOF systems for different gases and adsorption sites. Furthermore, the thermodynamic stability of MOF materials is analyzed by integrating DFT combined MD. The result shows that the MOF system has a higher absorptive selectivity to the inert elemental gases, while the absorptions of I₂ are very weak, due to molecular sieve effect. The channel structure of Nd-MOF exhibits different characteristics depending on the composition of the adsorption sites, and both types of channels have deeper adsorption potential wells for inert gases. Moreover, we note that the lattice remains stable under working conditions (250–400 K), and is prone to thermal decomposition at 700 K with the saturation of heat capacity. The Nd-MOF system is expected for the adsorption and separation of mixed-elemental gases and the purification of I₂.

Aromatic hydrocarbons (benzene, toluene, xylene) are valuable intermediates in the chemical and petrochemical industries, so the conversion of butane into aromatics is an important catalytic process from both scientific and industrial viewpoints. In addition to the production of aromatic compounds, the production of hydrogen during aromatization of lower alkanes is also of interest. This review describes industrial processes and presents the main achievements in the field of scientific research into butane aromatization on heterogeneous catalysts over the past 15 years. Current problems and possible directions of studies on the development of catalysts for aromatization of C₄ hydrocarbons are also discussed.

Expressions for the thermodynamic potentials (TPs) of small systems are traditionally used in thermodynamics by analogy with TPs of ordinary macro-phases. This form of introducing TPs for small systems eliminates their specificity consisting in the presence of dimensional dependences for TP values and all other thermodynamic functions. To take into account the sizes of small systems in the traditional method of introducing TPs, it is necessary to explicitly reflect the presence of an interface and the associated heterogeneity of the internal local properties of a small system. The general case is discussed when dimensional dependences of TPs of small systems in limited volumes are introduced, with macroscopic concepts of the phase and the interface non-autonomy being preserved. Options are considered to introduce size dependences into TPs of small droplets and separated fluid phases inside pores.

Hydrogermylation is used to obtain new compound, tris(pentafluorophenyl)-2-pyridylethylgermane. The structure is confirmed via IR and NMR spectroscopy, and X-ray diffraction analysis. Thermophysical properties are determined using DSC and TGA. Two polymorphic modifications (triclinic and monoclinic) of tris(pentafluorophenyl)-2-pyridylethylgermane are discovered. It is shown that the triclinic modification is more energetically advantageous than monoclinic modification. The topology of the electron density of tris(pentafluorophenyl)-2-pyridylethylgermane is studied theoretically and experimentally. an intramolecular Ge(1)-N(1) contact is discovered and its energy is estimated from the topology of electron density.

The authors study the laws governing the sorption of some derivatives of 1,2,3,4-tetrahydroquinoline and pyridazino[4,5-c]quinoline from water–acetonitrile solutions on an octadecyl-functionalized silica gel under reverse-phase high-performance liquid chromatography. The physicochemical characteristics and retention factors of sorbates at different acetonitrile concentrations in the eluent are determined. Dependences of the change in the retention factor as a function of sorbate structure and eluent composition are analyzed.

Electrochemical impedance spectroscopy is used to study the effect of potential (E) on capacitance (C) of porous tantalum coated with a layer of amorphous Ta₂O₅. It is shown that there is a positive linear dependence 1/C² in a wide range of potentials, and its slope can be used to control an oxide layer in porous tantalum. It is established that the transformation of the oxide layer during annealing in the temperature range 100–700°C strongly affects 1/C²(E)-graphics. Annealing at temperatures of 100–500°C raises the concentration of oxygen vacancies in the oxide layer due to partial transfer of oxygen into tantalum, resulting in lower slope of the 1/C²(E) plots as compared with initial non-annealed sample. After annealing at temperatures of 600 and 700°C, a TaO phase forms in the oxide film, accompanied by a strong increase in capacitance and a weak dependence on potential due to the emergence of a high concentration of donors in the oxide film. The promise is shown of using 1/C²(E) dependences to control a layer of oxide in porous tantalum, which could be useful in tantalum capacitor technology.

Pure and Co (10 mol %)-doped α-Fe₂O₃ (Hematite) nanostructures have been effectively synthesized by hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) have been used for the analysis of crystallography, morphology and functional groups of synthesized samples. The banding nature of synthesized samples is analyzed by Fourier transform infrared spectroscopy (FTIR). Powder XRD results reveal the formation of rhombohedral structured α-Fe₂O₃ nanostructures. Effect of dopant and synthesis conditions, such as precursor change and time duration of heating temperature has been investigated on the morphology of pure and Co (10 mol %)-doped α-Fe₂O₃ nanostructures. It has been observed that the addition of dopant, change of precursor and time duration of the heating temperature of hydrothermal treatment can effectively control the morphology of NPs. Methylene dye (MB) has been used as a test contaminant in aqueous solution to determine the photo-catalytic potential of Fe₂O₃ nanostructures under visible light.

The autowave combustion of ferroalloys (ferrovanadium, aluminum ferrochrome, ferroaluminum silicocirconium) in nitrogen are used to determine the phase composition of iron-containing metal–ceramic composites based on nitrides of aluminum, chromium, and vanadium. The content of iron on the surfaces of the composites is measured via scanning electron microscopy using an X-ray micro analyzer. The Hammett and Tanabe indicator reveals that aprotic Lewis basic centers (pK_a −0.29) and strong acidic Brønsted centers (pK_a 2.01, 4.1) dominate on the surfaces of chromium nitride-based composites. The surfaces of the samples based on vanadium nitride have many acidic Brønsted centers (pK_a 1.3–5.5). The correlation between the adsorption activity of composites and the studied organic pollutants (metamizole, cinnarizine, methylene blue, and methyl orange), plus the type and number of acid-base active centers on the surfaces of the materials, testifies to the dominance of chemisorption, for which mechanisms are proposed. The strong oxidative destruction of organic pollutants (64–96%) upon UV irradiation is due to the adsorption properties of the composites and the combination of heterogeneous photocatalysis and the homogeneous Fenton process.

Near infrared (NIR) Y₂Ti₂O₇:Ce³⁺/Cr³⁺/Nd³⁺ phosphors were synthesized using a solid-state reaction technique. NIR luminescent performance of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors was improved by doping with Ce³⁺ ions. The emission intensity of Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors is significantly higher than that of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors. The external quantum efficiency and internal quantum efficiency of Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺/1.5% Ce³⁺ are 16 and 22.8%, respectively. The luminescent mechanisms of the Y₂Ti₂O₇:Cr³⁺/Nd³⁺ and Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors were investigated. As a result, the effective energy transfer process from Cr³⁺ to Nd³⁺ ions exists in Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors, while the effective energy transfer process from Ce³⁺ to Cr³⁺ and Nd³⁺ ions exists in Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors. NIR emission intensities of LED devices assembled with Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺/1.5% Ce³⁺ phosphors are better than those of LED devices assembled with Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺ phosphors at different work currents. In addition, the temperature-sensitive behavior of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors was also studied. Their LIR and S_a values monotonically increase in the temperature range of 303–393 K. The maximum S_a values of Y₂Ti₂O₇:0.5% Cr³⁺/0.5% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/1.0% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/2.0% Nd³⁺ samples are 0.79 × 10^–2, 0.88 × 10^–2, 1.24 × 10^–4, and 2.53 × 10^–3 K^–1, respectively.

Thermodynamic characteristics are calculated for new products of the transformation of N,N‑dimethylhydrazine, the values of which can be used to reliably identify these compounds and predict their periods of retention. For the first time, the ideal gas–rigid rotator–harmonic oscillator approximation is used to predict entropies in the gas phase, and the Feller–Peterson–Dixon approach is used to obtain reliable enthalpies of formation in the gas phase for the considered compounds. Retention of the considered isomeric triazole derivatives under conditions of reverse phase high-performance liquid chromatography correlates well with the obtained values of thermodynamic characteristics.