Russian Journal of Physical Chemistry A最新文献

The paper describes the synthesis and characterization of a set of chromium oxide catalyst systems that contain 5 wt % of chromium and are supported on various commercial supports: 5Cr/SiO₂, 5Cr/Al₂O₃, 5Cr/Al₂O₃(Si), 5Cr/Al₂O₃(Ca,Mg), 5Cr/Al₂O₃(Si,Na), 5Cr/TiO₂, 5Cr/ZrO₂(W), 5Cr/ZrO₂(Si), and 5Cr/ZrO₂(La). The catalyst systems are studied by XRD, UV–Vis diffuse reflectance spectroscopy, and SEM–EPMA methods; all the samples are tested in the CO₂-assisted oxidative dehydrogenation of propane. The catalyst system exhibiting the highest activity in the propane dehydrogenation reaction in the presence of CO₂ in the gas phase is studied under supercritical conditions. The prospects for using high pressure in the studied reaction are shown.

As crucial additives and solvents in organic synthesis, the efficient separation of the cyclohexane + 1-propanol azeotropic system holds significant industrial importance. This study systematically evaluates the separation efficiency of ionic liquids for this azeotropic system using the COSMO-RS model. First, a database containing 364 ionic liquids was constructed by combining 26 anions with 14 cations, from which the high-performance extractant C5A20 was selected. Subsequently, vapor-liquid phase equilibrium experiments verified the reliability of the model predictions, demonstrating that the azeotropic point completely disappears when the mole fraction of C5A20 reaches 0.02. Further analysis through σ-profiles and hydrogen bonding interactions revealed the selective separation mechanism of C5A20 towards 1-propanol, providing molecular-level theoretical insights for the rational design of efficient ionic liquid extractants.

The conformational rearrangement of single or paired homogeneous polypeptide macromolecules of the same length, including those with different types of units, lying on the surface of a carbon nanotube were studied by molecular dynamics simulation at different pH levels. A mathematical model of macrochain conformations is presented, which allows for interactions in the complex of two similar polypeptides on the surface of the carbon nanotube, at different pH values of the solvent. When pH departed from the isoelectric point, the single polypeptide uncoiled and wound around the nanotube, while the two identical polypeptides repelled each other, shifting to the opposite ends of the nanotube. When two oppositely charged polypeptides were adsorbed on the surface of the carbon nanotube, they became tightly intertwined, forming a generally neutral polyelectrolyte complex. If the electric charge of one of the polypeptides in the complex did not change with a change in the pH level, while the electric charge of the other polypeptide decreased in magnitude, then the first polypeptide unfolded, dragging the second one along with it, and together they wound around the carbon nanotube.

A kinetic model of the catalytic hydroisomerization of n-hexadecane is developed. It is shown that the relevance of this process is attributed to the necessity to improve the low-temperature properties of diesel fuel and Group III and IV oils. The process is run for the selective isomerization of normal alkanes contained in the feedstock in the presence of a Pt/SAPO-11 catalyst based on platinum supported on SAPO-11 with a one-dimensional channel pore structure. The studies are conducted at temperatures of 300–360°C in increments of 20°C. Rate constants for the steps, preexponential factors, and activation energies for kinetic models for simplified and detailed n-hexadecane hydroisomerization schemes are calculated by solving the inverse kinetic problem. Numerical solution methods, in particular, the multistep variable-order Gear method and a genetic algorithm, are used. According to the calculated kinetic parameters, the dehydrogenation and protonation reactions that initiate the process are characterized by high activation energies. It is shown that an increase in temperature leads to an abrupt increase in the cracking rate relative to the isomerization rate.

The Y₂O₃ catalyst was prepared by using citric acid complexation method and the decorated Y₂O₃ catalyst was obtained through industrial carbonic acid (CA) impregnation. The phase structure characterization confirmed that the cubic phase of Y₂O₃ was not destroyed by CA impregnation, but C–O functional groups were still present on the surface. After impregnating with CA, the surface contour of Y₂O₃ particles becomes clearer and the agglomeration phenomenon is weakened. The average particle size of the decorated Y₂O₃ is approximately 60 nm. Element mapping characterization also confirmed the presence of a small amount of C element in the decorated Y₂O₃. The photoresponse capability of the decorated Y₂O₃ catalyst can be extended from 400 nm to a visible light range of 800 nm. The optical bandgap value of the decorated Y₂O₃ decreased from the undecorated 3.15 to 2.88 eV. The degradation experiment carried out with chlortetracycline hydrochloride as the degradation target pollutant found that when the catalyst content was 1 g/L, the pollutant concentration was 150 mg/L and pH 5, the degradation percentage of the decorated Y₂O₃ catalyst reached 94.6%. Experiments and band theory have confirmed that the decorated Y₂O₃ catalyst has a high photocatalytic activity, which is related to the free radicals and its point of zero charge (PZC). The use of this new processing technology enables the expansion of the application range of wide bandgap semiconductor materials in the field of photocatalysis.

This study investigates the removal of malachite green (MG) dye from aqueous solutions using the strong acid cation-exchange resin, Purolite C100. Batch adsorption experiments were conducted to evaluate the influence of key operational parameters, including initial pH, resin dosage, initial dye concentration, and temperature. Kinetic analysis revealed that the pseudo-second-order (PSO) model provided an excellent fit to the experimental data (R² > 0.99), suggesting that the rate-limiting step involves chemisorption-type interactions. Equilibrium data were best described by the Redlich–Peterson isotherm model, indicating a hybrid adsorption mechanism. The Langmuir model also provided a good fit, yielding a high maximum monolayer sorption capacity (qₘ) of 277.80 ± 9.63 mg g^–1 at 50°C. Thermodynamic analysis revealed that the process is thermodynamically favorable under standard conditions (∆G° < 0), endothermic (ΔH° = +7.7 ± 0.1 kJ mol^–1), and characterized by an increase in system entropy (ΔS° = +84.0 ± 1.1 J mol^–1 K^–1). Overall, this study confirms that Purolite C100 is a highly efficient and promising material for the sequestration of malachite green from contaminated wastewater.

In this work, we prepared perovskite by the addition of KI and investigated its effect on the efficiency of perovskite solar cells with carbon electrodes. We found that the addition of appropriate amounts of KI to perovskite precursor solution led to the increase in the crystalline size and crystallinity of perovskite and improved the light absorption of the prepared films. When the concentration of KI additive was 0.075 mol/L, the perovskite solar cell efficiency was 14.21%, which was 1.2-fold higher than that of the control (11.78%). The analysis showed that the addition of KI improved the characteristics of the device due to the improved crystallinity and crystallinity of perovskite and effective suppression of non-radiative recombination.

All calculations in hand have been investigated by using the first-principles method within the full-potential linearized augmented plane wave (FP-LAPW) method implemented in wien2k package. The framework of generalized gradient approximation (GGA96) has been used to describe the exchange-correlation potential. It has been found that the substitution and the increase of pressure cause a decrease in the bond length, lattice constant, and volume. Noticeably, the energetic properties are improved after applied pressure variations and the substitution, such as after the substitution of La with Y and Sc the heat of formation value reduces by about 20 and 10%, respectively. Otherwise, the gravimetric hydrogen storage (wt %) is increased after the substitution. Furthermore, the pressure variations and the substitution led to the Fermi energy value increased and the density of states at the Fermi level decreased.

A system with three or more components (n ( geqslant ) 3) is quasi-simple if the isotherms–isobars–isopotentials of the system’s components (the solvents of solubility diagrams) are line segments (n = 3), sectors of planes (n = 4), or hyperplanes (n ( geqslant ) 5). This work presents evidence that all figurative points on monovariant branches of the joint crystallization of two identical solid phases in different quasi-simple quaternary systems (n = 4) (with two identical and one different component) belong to a single curve. Systems of equations are given for thermodynamic calculations of such curves exclusively from data on binary subsystems. Examples of calculating these monovariant curves are provided, and agreement is shown between non-model calculations and experimental data on the compositions of saturated solutions using quaternary systems with a common cation, a common anion, and quaternary reciprocal systems as examples. Agreement is also seen between results from thermodynamic calculations and numerous experimental data. The results can naturally be extended to monovariant crystallization lines of three or more identical solid phases on the solubility diagrams of quasi-simple systems with five or more components (and one that is different).

The LiNi_1/3Co_1/3Mn_1/3O₂ cathode material was successfully synthesized by the co-precipitation-assisted polymer network gel method. The prepared LiNi_1/3Co_1/3Mn_1/3O₂ material had a relatively small particle size and exhibited excellent electrochemical performance. The sample can provide an initial discharge specific capacity of 196.0 mA h g^–1 (0.2 C). At a 2 C rate, the initial discharge reached 160.2 mA h g^–1, and the capacity retention rate was 62.7% after 100 cycles. In addition, at a high magnification of 5 C, the capacity retention rate still remained at 56.0%, after 100 cycles. Electrochemical data indicated that the LiNi_1/3Co_1/3Mn_1/3O₂ material exhibits superior rate performance. The excellent electrochemical performance of the material was attributed to the constraints of the gel grid and the generation of flowing gas during the calcination of the carbonate precursor, which hinder the agglomeration of the powder and further enhances the dispersibility of the particles. The obtained LiNi_1/3Co_1/3Mn_1/3O₂ cathode material with uniform particle size reduced the charge transfer resistance and enhanced the lithium ion diffusion capacity.