The alkylation of toluene with diethyl carbonate (DEC) was studied over ZSM-5 (MFI) zeolite catalysts modified with magnesium oxide and palladium. MgO modification effectively suppressed strong Brønsted acid sites, leading to enhanced para-selectivity by inhibiting disproportionation, isomerization, and deep alkylation reactions. The introduction of palladium provided hydrogenation–dehydrogenation functionality, markedly improving catalyst stability by suppressing olefin oligomerization and coke formation. As a result, high selectivity toward p-ethyltoluene was achieved at moderate toluene conversion under optimized conditions. The influence of reaction temperature, space velocity, and toluene/DEC molar ratio on catalytic performance was systematically investigated. Toluene conversion exhibited non-monotonic behavior with respect to these parameters, reflecting a balance between DEC activation, reactant contact time, and catalyst deactivation. Optimal operating conditions provided high para-selectivity while limiting secondary isomerization and polyalkylation reactions. Fresh and spent catalysts were characterized by XRD, N2 physisorption, NH3-TPD, Py-IR, TEM, TGA, and DSC. These analyses revealed that MgO modification alone leads to the formation of condensed, pore-blocking coke, whereas palladium alters the nature of carbonaceous deposits toward less condensed species, thereby enhancing catalyst stability. Compared with literature systems based on alcohols and other carbonates, the developed catalysts operate at lower alkylating-agent excess and higher space velocities while maintaining competitive conversion and para-selectivity.

Oxidative desulfurization technology of petroleum fractions purification is a highly relevant topic. In this study, new molybdate-based catalysts were proven to be highly efficient in the oxidation of model and real diesel fuels. Surface acidification during impregnation of hydroxyapatite promotes the self-assembly of Keggin-type phosphomolybdates alongside with polymolybdate (“molybdenum blue”) clusters and generates a synergistic catalytic system. Controlled thermal treatment preserved polyoxomolybdate structures responsible for enhanced activity. The optimized catalyst demonstrated efficient oxidation of dibenzothiophene over a wide sulfur concentration range (500–8000 ppm). Notably, 99% sulfur removal from straight-run diesel containing 11,700 ppm was achieved at 70 °C within 8 h, confirming applicability to real feedstock. The results highlight hydroxyapatite as a reactive support enabling in situ formation of active polyoxomolybdate species and provide a scalable strategy for deep desulfurization of high sulfur fuels under mild conditions.

The parametrization of the thermomechanical behavior of shape memory alloys (SMAs) under constant load is described in terms of their functional properties. The deformation–temperature–stress behavior of SMAs from various alloy systems—such as Ni-Ti, Ni-Ti-Cu, and Ni-Mn-Ga—was parametrized using a sigmoidal function. This approach enables the characterization of phase transformation parameters, including transformation temperatures, kinetic parameters, and the relationship between recoverable deformation and applied stress. It is shown that the sigmoid function can serve as a universal descriptor of thermoelastic phase transformations across different alloy systems and transformation types, such as B2–R–B19′–R–B2 (Ni-Ti-Cu), B2–R–B19′–B2 (Ni-Ti), and B2 (L21)–B19′ (L20)–B2 (L21). A correlation coefficient of approximately 0.99 was achieved. The present work extends the theoretical framework of diffuse martensitic transitions in SMAs, for which the sigmoid function has been theoretically derived to describe phase fractions. The article’s novelty lies in shifting from pure mathematical approximation (curve fitting) to physical parametrization of SMA behavior specifically under constant stress (actuator mode).

Membrane separation is an efficient approach for volatile organic compound (VOC) recovery from industrial off-gases due to its low energy consumption, compact design, and operational simplicity. Membrane-based VOC recovery critically depends on the membrane material, which must exhibit high VOC permeability and selectivity under mixed-gas conditions. In this study, novel highly selective membranes for VOC removal based on polydecylmethylsiloxane (PAMS-10) were synthesized using both polydimethylsiloxane and various alpha,omega-dienes as cross-linkers: 1,7-octadiene (OD), 1,9-decadiene (DD), and 1,11-dodecadiene (DdD). The influence of cross-linker concentration and length on mechanical, structural, sorption, and transport properties was examined extensively. The combination of three independent experimental methods (time-lag, vapor permeation, and in situ spectroscopic ellipsometry) revealed that increasing alpha,omega-diene concentration and decreasing its length led to a reduction in the diffusivity and permeability of permanent gases, gaseous hydrocarbons, and VOC vapors. For VOC/N-2 separation, the slightly cross-linked OD-1 membrane and the DdD-5 membrane, cross-linked with long 1,11-dodecadiene, demonstrated outstanding mixed-gas selectivities of 950/921/314/840 and 940/1084/233/1106 for toluene/n-octane/i-octane/n-butyl acetate, respectively. Notably, the DD-5 membrane, cross-linked with 1,9-decadiene, matching the length of the PAMS-10 side chain substituent, exhibited the best mechanical properties and mixed-gas selectivity comparable to the ideal selectivity, a unique behavior attributed to optimal supramolecular organization.

Much focus is being dedicated to the development of innovative technologies for producing biodegradable polymers from plant biomass. It is proposed that annual and perennial herbaceous plants, such as miscanthus, be used as promising sources of cellulose. The component composition of miscanthus allows us to consider it as a raw material for obtaining cellulose. This paper proposes methods for cooking miscanthus lignocellulose raw materials, which allow sulfate cellulose to be obtained with a high yield (up to 52%). In the process of obtaining chemical–thermomechanical pulp, the product yield is 71%. The possibility of replacing unbleached sulfate pulp with a semi-finished product from miscanthus for paper production is considered. For all types of raw materials obtained, acceptable paper-forming properties are observed. The best strength and deformation properties are obtained for sulfate cellulose. The addition of this cellulose to the composition of waste paper fluting significantly increases the sheet density, elasticity, and energy capacity without losing tensile strength. Using miscanthus raw materials along with waste paper of grade MS 5B makes it possible to make a composite product. The resulting products have optimal mechanical properties for creating the middle layer of corrugated cardboard. Miscanthus cellulose can be considered a promising raw material for enhancing waste paper fluting. Altering the system composition utilizing miscanthus and waste paper enables a broad modification of the mechanical and optical qualities of the resultant paper. The recommended concentration of miscanthus fraction in waste paper fluting is 30%.

Both annual (cotton, flax, hemp, etc.) and perennial (trees and grasses) plants can serve as a source of cellulose for fiber production. In recent years, the perennial herbaceous plant miscanthus has attracted particular interest as a popular industrial plant with enormous potential. This industrial crop, which contains up to 57% cellulose, serves as a raw material in the chemical and biotechnology sectors. This study proposes for the first time the utilization of miscanthus, namely Miscanthus Giganteus “KAMIS”, to generate spinning solutions in N-methylmorpholine-N-oxide. Miscanthus cellulose’s properties were identified using standard methods for determining the constituent composition, including also IR and atomic emission spectroscopy. The dry-jet wet method was used to make fibers from cellulose solutions with an appropriate viscosity/elasticity ratio. The structural characteristics of the fibers were studied using IR and scanning electron microscopy, as well as via X-ray structural analysis. The mechanical and thermal properties of the novel type of hydrated cellulose fibers demonstrated the possibility of producing high-quality fibers from miscanthus.

A method for obtaining nonwoven precursors of carbon materials based on natural and viscose fibers was developed. Bast (flax and hemp) fibers were used as sources of natural fibers which were previously processed in order to remove impurities and enrich with the alpha fraction of cellulose. The structure, morphology, and chemical composition of natural and viscose fibers were studied by X-ray, SEM, and IR spectroscopy. The mechanical characteristics of the fibers were determined. The results of studies of the thermal behavior of mixed materials based on viscose, flax, and hemp fibers at temperatures up to 1000 °C were presented. The introduction of a small fraction of natural fibers into viscose (up to 30

Nanosized mixed tungsten-iron carbide (FeWC) was successfully applied in aerobic oxidative desulfurization. The combination of catalytically active centers responsible for the activation of oxygen and the oxidation of sulfur-containing compounds made it possible to obtain a highly efficient catalyst. The catalyst was synthesized by microwave irradiation, allowing to obtain a nanoscale catalyst in just 15 min. The catalyst was characterized in detail by a variety of methods: XRD, HRTEM, EDX, SEM, XPS, and low-temperature nitrogen adsorption/ desorption. The key factors influencing the dibenzothiophene (DBT) oxidation were investigated. Under opti-mized conditions DBT conversion was 100% in 1 h at 130 degrees C, 6 atm. The possible mechanisms including oxygen activation, alkyl peroxide formation, and substrate oxidation by tungsten peroxo-complexes were discussed. The catalyst retains its activity for at least 5 cycles of oxidation-regeneration. Aerobic oxidative desulfurization of straight-run gasoline in the presence of FeWC was performed and sulfur content was reduced from 995 to 6 ppm.

A method for obtaining nonwoven carbon materials by the staged heat treatment of cellulose felt is developed. Fabrics produced from fibrous flax cellulose and viscose fibers by needle punching are used as nonwoven precursors. To obtain carbon fabric precursors the optimum ratios of components are chosen from the data on the formation of nonwoven fabrics and the thermal analysis of various blend formulations. It is shown that the content of flax fibers in the system should be at least 50%. Viscose fibers play the role of a reinforcing material and so far cannot be fully excluded from the system. With an increase in the content of flax cellulose the value of carbon yield grows. The mechanical properties of the carbon felt are provided by the physical network of friction and dispersion contacts between individual fibers. Upon heat treatment of the composite nonwoven material, the morphological features of precursor fibers remain unchanged. The interplanar distances of carbon layers in the carbon material are calculated using X-ray diffraction analysis and transmission electron microscopy. The fraction of carbon upon heat treatment to 1700°С is at least 90%, and after graphitization to 2400°С the purity of the product is above 99%. The maximum values of carbon yield at this temperature may be as high as 25‒27%. The coefficients of thermal conductivity of the carbon felt are measured, and the values obtained are 30% lower than the corresponding parameters of carbon fabrics.

The thermo-oxidative stability and gas transport properties of poly(4-methyl-2-pentyne) (PMP) samples of the mixed configurational composition (50

A comprehensive study of phase composition, structural state, parameters of fine atomic structure, mechanical and tribological properties of molybdenum-carbon and tungsten-carbon-based coatings deposited by reactive magnetron sputtering in an acetylene-argon gas mixture has been carried out. It has been shown that the resulting coatings have a nanocomposite diamond-like carbon (DLC) structure based on the metal and the metal carbide phases with close sizes of coherently diffracting domains (CDD), 3–7 nm, and on hydrogenated amorphous carbon. The coating nanohardness values were 13–15 and 20–23 GPa for the Mo-DLC and W-DLC coatings, respectively. The tribological tests have demonstrated that the Mo- and W-DLC coatings can reduce friction and effectively protect the steel surfaces hardened by them both under dry friction and under boundary lubrication conditions.

Effect of the content of tetrafluoroethylene groups on the gas transport properties of vinylidene fluoride-tetrafluoroethylene copolymers has been studied. The experimental values of permeability coefficients P and diffusion coefficients D for gases H2, He, N2, O2, and CO2 as well as lower hydrocarbons CH4, C2H4, and C2H6 are measured, and their solubility coefficients S are calculated. It is shown that the values of the solubility coefficients of СО2 and С2Н4 deviate from the direct correlation dependence of lоg S on the Lennard-Jones potential, and this effect is explained in terms of facilitated transport models. It is demonstrated that an increase in the content of TFE groups leads to a significant rise in the permeability coefficients of the studied penetrants mainly due to an increase in their diffusion coefficients. For example, the permeability coefficient of helium and hydrogen increases by almost 2.5 times, carbon dioxide by 3 times, argon, oxygen, methane and ethylene by 3.5 times, and nitrogen and ethane by 4.4 times, respectively. These gas separation parameters in combination with good film-forming properties and commercial availability make it possible to consider the studied VDF-TFE copolymers to be promising materials for the fabrication of composite gas separation membranes.

The effect of the stereoregularity of poly(1-trimethylsilyl-1-propyne) [PTMSP] (cis-content from 50 to 90%) on physical aging was investigated by measurement of the gas permeability. Films from pure PTMSP as well as those with the addition of the antioxidant Irganox 1076 were exposed to the air. The permeability of pure PTMSP films increases with an increase in cis-stereoregularity and correlates with an increase in interchain distances (according to X-ray analysis). For pure PTMSP films, the most significant aging (up to 50% of permeability drop) was observed for polymers with mixed microstructure, and the slowest aging (10–30% of permeability drop) was observed for polymers with cis-regular structure. For PTMSP films with added Irganox 1076, some decrease in permeability with time is also observed. The addition of Irganox 1076 to PTMSP in mixed as well as cis-enriched configurations visibly slows down aging. In the case of cis-regular PTMSP with a slow aging rate, the introduction of an antioxidant does not provide any advantages. The high stability of cis-regular PTMSP demonstrates the possibility of obtaining more stable membrane materials with the highest equilibrium state of the polymer selective layer prepared by casting solution.

In this work, for the first time, we studied the permeability of individual lower hydrocarbons and in a C1/C4 mixture for films based on PTMSP of a new cis-enriched configurational composition (the content of cis-units in the samples was 80 and 90%). The methane permeability of freshly prepared cis-regular PTMSP films (90% of cis-units) exposed to air for a month is higher than the corresponding values of PTMSP films with 80% cis-units. The X-ray diffraction data indicate a looser packing of the cis-regular PTMSP. The introduction of the antioxidant Irganox 1076 into PTMSP films leads to a decrease in the initial level of the methane flux. At the same time, the permeability of films with the addition of Irganox 1076 over time (within 1 month) decreases much more slowly compared to films without the addition of an antioxidant. The permeability of individual lower hydrocarbons through PTMSP films without and with the addition of Irganox 1076 increases in the order С1 C2 C3 C4. The value of the separation factor in the n-butane/methane mixture reaches 33, which is almost 7 times higher than the selectivity for individual components. The high level of n‑butane permeability of cis-enriched PTMSP is maintained for at least a month of films storage in air.

The thermally activated relaxation of poly(1-trimethylsilyl-1-propyne) (PTMSP) samples of various cis-/trans-compositions (50–80% units of cis-configuration) in the presence of phenolic antioxidants of various structures was investigated. It was pointed out that polymers with a high content of cis-units exhibited greater thermal-oxidative stability due to the greater flexibility of the cis-enriched macrochains. The use of hindered phenols as antioxidants made it possible to prevent the process of thermally initiated oxidative degradation. At the same time, the most effective stabilizing agents were antioxidants with larger molecules such as Vulkanox BKF, Irganox 1010, and Irganox 1076. It was shown that the permeability coefficients of stabilized PTMSP during thermal treatment initially slightly decreased (by 20–30%), which, according to the X-ray diffraction data, was associated with an increase in the density of the macrochain packing, and during further heating remained practically unchanged. Note that for the cis-enriched samples, no signs of oxidation or decrease in the transport characteristics were observed during polymer heating for 240 h at 140 °C.

The one-sided modification of homogeneous polymer films of polyvinyltrimethylsilane (PVTMS), poly(2,6-dimethylphenyl-1,4 oxide) (PPO), and polybenzodioxane (PIM-1) was carried out by liquid-phase fluorination method using a fluorine-nitrogen mixture in perfluorodecalin. The fluorination time ranged from 10 to 60 min. For PPO films the amorphous and β-nanocrystalline phase (48%) was found by X-ray diffraction analysis of the original films. It was shown that fluorination does not significantly affect the degree of PPO crystallinity. The effect of fluorination time on the effective coefficients of permeability, diffusion, and solubility of oxygen and nitrogen has been studied. It was found that the fluorination leads to a decrease in both effective diffusion coefficients and effective gas solubility coefficients, while the resulting increase in permeability selectivity ranged from 30% for PVTMS to a 2 times increase in the case of PPO and PIM-1. It has been noted that this improvement in permeability selectivity is achieved mainly by the solubility selectivity increasing. The permeability of O2/N2 mixture for original and modified films was studied. It was found that the achieved values of the separation factors are close to the ideal selectivity. The results obtained demonstrate the possibility of effective application of the liquid-phase modification method not only for the homogeneous polymer films of the studied polymers treatment, but also for membranes with a selective non-porous layer based on them.

Cellulose and copolymers of acrylonitrile (PAN) are characterized by their chemical resistance to several conventional solvents. Therefore, these polymers are often used to obtain membranes for the recovery of such solvents. In this work, for the first time, composite membranes formed from highly concentrated mixed solutions based on cellulose and PAN are considered (the total content of polymers is 18 wt.%). For mixed solutions, the morphology and rheological behavior were evaluated. It is shown that the resulting solutions are two-phase, and their morphology depends on the components' ratio and the system's history. The non-monotonous change in the viscosity with the PAN content indicates a specific interaction of cellulose and PAN in N-methylmorpholine-N-oxide solutions. The rheological behavior of mixed solutions allows for their processing in conditions identical to those of cellulose solutions. The introduction of PAN into the cellulose matrix promotes a decrease in the structural order in the system, affecting the membranes' transport properties. For composite membranes, it was found that with an increase in the content of the PAN phase, the retention of Remazol and Orange decreases, while the observed values are several times higher than those for cellulose membranes. The permeability of ethanol increases with increasing terpolymer content.

This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope’s drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3–30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.

A simple X-ray powder diffraction procedure is proposed to determine the framework composition of ZSM-5 type zeolites. The procedure is based on a linear relation between the unit cell volume and the framework aluminum content found by analyzing two families of ZSM-5 zeolites with different SiO2/Al2O3 ratios. One family consisted of products synthesized in the presence of TPA+ cations while hydrogen forms were included in the second series of samples. Linear relationships between cell constants, cell volume (Vu.c.), and the framework aluminum content (NAl) were established. For the samples synthesized in the presence of an organic template and sodium cations, the relation between NAl and Vu.c. is given by NAl = (Vu.c. - 5332 angstrom 3)/15.13. A similar equation was computed for H-ZSM-5 zeolites: NAl = (Vu.c. - 5330 angstrom 3)/15.40. Equations derived can be used to evaluate the number of framework aluminum in the unit cell. In this way, the ratio of the framework and nonframework aluminum atoms in the samples of ZSM-5 type zeolites subjected to heat treatment can be estimated.

Morphological transformations in emulsions of cellulose and polyacrylonitrile (PAN) ternary copolymers containing acrylonitrile, methyl acrylate, and methylsulfonate comonomers in N-methylmorpholine-N-oxide were studied over the entire range of concentrations depending on temperature and intensity of the deformation action. Based on the morphological and rheological features of the system, the temperature-concentration range of spinnability of mixed solutions was determined, and composite fibers were spun. The fibers are characterized by a heterogeneous fibrillar texture. Studies of the structure of the fibers, carried out using X-ray diffraction analysis, revealed a decrease in cellulose crystallinity with an increase in the content of PAN. The study of the thermal properties of the obtained fibers, carried out using DSC, and chemical transformations in them in a wide temperature range by high-temperature diffuse reflection IR spectroscopy made it possible to reveal a new intense exothermic peak on the thermograms at 360 °C, which according to the IR spectra corresponds to the transformation of intermacromolecular physical interactions of the PAN and cellulose into covalent bonds between polymers. In addition, the ester groups found during the thermal treatment of the PAN part of the composite fibers in the pyrolysis zone can have a key effect on the process of their further carbonization.