Russian Journal of Applied Chemistry最新文献

In this work proposed cascade three-stage oat husk processing for isolation of low crystalline and lignin-free cellulose being perspective for chemical transformations. Such a product seems to be perspective for obtaining products which are important for chemical industry. The approach proposed includes stages of peroxide oxidative delignification, alkali treatment and mechanical activation in planetary mill. The optimal parameters of oxidative delignification were determined: the process temperature 100°C, the solid to liquid ratio 1 : 26, the hydrogen peroxide and acetic acid concentration 6 and 25 wt %, respectively, and the time of preliminary mechanical activation 30 min. Semiproduct was subjected to additional alkaline treatment and mechanical activation in a planetary mill to reduse residual lignin content and crystallinity degree. As a result of the cascade three-stage processing, it was possible to obtain a sample of cellulose with a low residual lignin content of 1.9 wt % and low crystallinity of 35%. To our knowledge, a cascade three-stage processing for the isolation of cellulose from oat husks which includs peroxide oxidative delignification, alkali treatment and mechanical activation has been proposed for the first time. In addition, peroxide oxidative delignification using a manganese sulfate catalyst was also carried out for the thirst time for oat husk biomass.

The possibility of depolymerizing dehydrogenated polyolefins containing double bonds in the chain using the ethenolysis reaction on Grubbs catalysts was studied. Commercial polyoctenamer was used as a model of the dehydrogenated polymer. It was shown that the first generation Grubbs catalyst and the Grubbs–Hoveyda catalyst effectively reduce the molecular weight of the polyoctenamer even at room temperature. An increase in temperature promotes both an increase in the ethenolysis rate and a decrease in the polymer molecular weight. In the presence of the Grubbs–Hoveyda catalyst at 45°C, it was possible to reduce the molecular weight of the polyoctenamer from 120 000 to 480 Da. It was established that the ethenolysis of specially prepared dehydrogenated polyethylene is primarily lead to the isomerization of terminal double bonds with their migration into the chain; effective depolymerization is hindered by the poor solubility of the polymer in the reaction medium.

The article deals with the synthesis of new diacetoxymethyl and dichloromethyl derivatives of 1,4-disubstituted 1,2,3-triazoles by the reaction of acetylation with acetic anhydride and chlorination with thionyl chloride of the starting 2-nitro-1,3-bis(4,4'-dihydroxymethyl)-1,2,3-triazolyl-2-azapropane and 3-nitro-1,5-bis(4,4'-dihydroxymethyl)-1,2,3-triazolyl-3-azapentane. The structure of the obtained compounds is confirmed by IR and NMR spectroscopy. These compounds are of interest as starting materials for the synthesis of new biologically active and high-energy substances.

This paper reviews the synthesis methods of glycerol carbonate, such as phosgene method, oxidative carbonylation, transesterification, urea glycerolysis, and direct carbonylation. The latest advances in the synthesis of glycerol carbonate were outlined and their drawbacks were also pointed out. The research advances and issues in the catalytic carbonylation of glycerol with CO₂ were discussed and assessed in detail. When the carbonylation of glycerol with CO₂ was homogeneously catalyzed by di(n-butyl)tin(IV)oxide and HDBU⁺I^‒ protic ionic liquid catalysts utilizing 13X zeolite and styrene oxide as dehydrating agents, glycerol carbonate yields reached 35% and 79.1%, respectively. In the carbonylation reaction catalyzed by di(n-butyl)tin(IV)oxide catalyst, it was suggested that di(n-butyl)tin(IV)oxide was firstly activated by methanol molecules, glycerol molecules replaced the methoxy groups to be activated, and then CO₂ molecules interacted with the activated glycerol molecules to produce glycerol carbonate. While HDBU⁺I^‒ protic ionic liquid catalyzed the carbonylation reaction, HDBU⁺ and I^‒ ions activated glycerol and CO₂ molecules, resulting in the formation of glycerol carbonate. When the carbonylation of glycerol with CO₂ was heterogeneously catalyzed by ZnO catalyst without using a dehydrating agent and Zn-doped CeO₂ nanorod catalyst using 2-cyanopyridine as a dehydrating agent, yields of glycerol carbonate were 8.1% and 80.9%, respectively. The dehydrating agent in situ eliminates water in the carbonylation process, which improves the forward reaction towards glycerol carbonate and increases glycerol carbonate yield. Various catalytic reaction mechanisms were proposed in direct carbonylation of glycerol with CO₂ towards glycerol carbonate when solid phase catalysts were utilized, which require further investigation. In direct carbonylation of glycerol with CO₂, the key problems are to design effective catalysts for activating stable CO₂ molecule and efficient dehydrating agent inert to both glycerol and CO₂.

Copper oxide powders were synthesized using a low-temperature underwater plasma method with varying discharge currents (0.25–0.8 A). The resulting samples were characterized by X-ray phase analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and thermogravimetric analysis, and were evaluated as sorbents. It was observed that the plasma parameters influenced the phase composition and surface structure of the powders but did not affect their surface morphology. All samples exhibited a high sorption capacity for the antibiotic tetracycline.

This paper investigates the degradation of SDS (a proxy for sodium linear alkylbenzene sulfonate) in water using a SiC/g-C₃N₄ (SCN) composite photocatalyst. The SCN composite was synthesized by calcining melamine and SiC powder and characterized through XRD, SEM, EDS, XPS, UV-Vis DRS analyses. Photocatalytic experiments conducted at room temperature evaluated the degradation performance, stability, and mechanism of SCN. The results confirm the successful synthesis of SCN, which exhibits broader light absorption, higher efficiency compared to pure g- C₃N₄, and enhanced photogenerated electron-hole separation. Under visible light irradiation in the presence of hydrogen peroxide, SCN effectively degrades SDS, maintaining approximately 90% degradation efficiency after three cycles, demonstrating good stability. Sacrificial agent tests indicate that h⁺, OH, ·O₂⁻, and e⁻ all contribute to the degradation process. The degradation mechanism is attributed to the SiC/g-C₃N₄ heterojunction, which promotes charge separation and reactive species generation, making SCN a promising photocatalyst for aqueous SDS degradation.

Nickel-based catalysts supported on mesoporous SBA-15 were synthesized and evaluated for dry methane reforming as a route for simultaneous utilization of CH₄ and CO₂. To enhance catalyst stability and coke resistance, Ce–Zr mixed oxides and La were introduced either by post-synthesis impregnation or by pre-modification of the SBA-15 support. Textural and structural characterization revealed that pre-modified catalysts possess higher specific surface areas and improved Ni dispersion compared to post-modified analogues. All catalysts exhibited high initial activity at 800 °C with CH₄ and CO₂ conversions exceeding 80%. However, significant differences in stability were observed. The unmodified SBA-15/Ni catalyst showed a pronounced gap between CH₄ and CO₂ conversions and H₂/CO ratios below 1, indicating intensive coke formation and reverse water–gas shift activity. Incorporation of Ce–Zr suppressed deactivation by enhancing redox properties and CO₂ activation, while La addition further improved stability through carbonate formation and carbon gasification. The highest resistance to deactivation was achieved for the SBA-15/Ce/Zr/La/Ni catalyst prepared via pre-modification, which exhibited minimal conversion loss, near-stoichiometric H₂/CO ratios, and the smallest conversion gap. These results demonstrate that controlled incorporation of redox-active promoters and optimized preparation strategy are key factors in designing stable Ni/SBA-15 catalysts for DRM.

Using Raman spectroscopy, the features of the hydrolytic polycondensation of tetraethoxysilane (TEOS) with free access of air, as well as the effect of catalytic and excess amounts of the polyether amine Jeffamine T-403 on this process are studied. This amine was used as a curing agent to obtain a pure epoxy polymer and form a polymer matrix of the composite modified with silicon dioxide (2 wt %). Low-viscosity epoxy oligomer Eponex 1510 was used as a polymer binder. Thermophysical properties of film samples of the polymer and composite under tensile and bending loads were studied in detail. Based on TMA and DSC data, parameters characterizing the topological structure of the samples were determined. The effect of silica on the segmental mobility of interstitial chains of the network composite was established, which leads to an increase in the glass transition temperature by 10–16°C and a decrease in the relative deformation of the sample. Thermogravimetric studies have shown that the presence of silicon dioxide in the composite reduces the maximum rate of mass loss of the composite. The resulting composite coatings on the surface of the D16 aluminum alloy retain their integrity under prolonged exposure to salt fog, unlike coatings based on unfilled epoxy polymer.

The article describes the methods for the preparation of two new generation biocide additives, namely zinc oxide immobilized on graphene oxide and a complex biocidal additive based on polyhexamethylene guanidine immobilized on montmorillonite, and their application in two-component polyurethane coatings, which differ in both the polyol and isocyanate components. The antimicrobial activity of these additives against Aspergillus flavus ATCC 9643, Staphylococcus aureus ATCC 6538, and Candida albicans ATCC 9027 has been studied. The coatings were applied by aerosol spraying of solutions in volatile solvents. The adhesion to steel substrate (peel resistance) and hardness of the polyurethane coatings containing these additives were also evaluated. IR spectroscopy was used to compare polyurethane coatings with different polyol components. This method has been used to investigate the interaction between the additives and the components of the reaction system. The effectiveness of biocide additive in polyurethane systems was compared.

The work proposes a simplified kinetic model for Fischer–Tropsch synthesis from CO₂, incorporating the reverse water-gas shift reaction and generalized steps for the formation of methane, C₂–C₄ hydrocarbons, and the C₅⁺ fraction. The kinetic parameters of the model were determined based on experimental data in the temperature range of 260–320°C and pressures of 20–30 atm by solving the inverse chemical kinetics problem using a combination of a genetic algorithm and the Levenberg–Marquardt method. It is shown that the reverse water-gas shift reaction under the studied conditions does not reach thermodynamic equilibrium and limits the overall conversion of CO₂. The analysis of activation energies explains the observed decrease in selectivity towards heavy hydrocarbons in favor of lighter fractions with increasing temperature. Comparing the calculated data (for pure CO₂) with experimental results obtained when feeding ammonia made it possible to estimate the contribution of amination reactions. It was revealed that in the presence of ammonia, a reduction in the selectivity of methane formation as the main undesirable reaction product is achieved.