Rinat M. Iskakov

В условиях роста объёмов пластиковых отходов и увеличения спроса на экологически чистые источники энергии разработка эффективных катализаторов для получения водорода приобретает особую актуальность. Целью настоящего исследования является синтез, физико-химическая характеристика и оценка каталитической активности таганского бентонита, модифицированного полидиметилакриламидом (ПДМА), в процессе каталитической конверсии углеводородов с получением водородсодержащего газа. В качестве носителя использован природный бентонит месторождения «Таган», предварительно подвергнутый кислотной активации и модифицированный 1 мас.% ПДМА методом пропитки. Структурные и морфологические особенности полученного катализатора исследованы методами рентгенофазового анализа (XRD), инфракрасной спектроскопии с преобразованием Фурье (FTIR), сканирующей и просвечивающей электронной микроскопии (СЭМ и ПЭМ). Каталитические испытания проводили в реакторе с фиксированным слоем при температуре 650 °С с последующим анализом газообразных продуктов методом газовой хроматографии. Результаты исследований показали, что модификация полидиметилакриламидом не приводит к разрушению кристаллической структуры монтмориллонита, а способствует формированию полимер-минерального нанокомпозита с развитой пластинчатой морфологией и улучшенными поверхностными характеристиками. В составе газообразных продуктов каталитической конверсии установлено содержание водорода 35,9 об.%, метана 34,1 об.% и углеводородов фракции C₂–C₃ 29,5 об.%. Выход водорода составил 1,28 ммоль/г, а отношение H₂/CH₄ достигло 1,05, что свидетельствует об эффективном протекании реакций крекинга и дегидрирования на поверхности катализатора. Полученные результаты подтверждают перспективность использования ПДМА-модифицированного таганского бентонита в качестве доступного и эффективного гетерогенного катализатора для термокаталитической переработки полимерных отходов с получением водородсодержащего газа и могут служить основой для разработки экологически безопасных технологий утилизации пластиковых отходов и производства альтернативных энергоносителей.

Natural bentonite, dominated by montmorillonite-type layered aluminosilicates, is increasingly considered as an inexpensive and environmentally acceptable support or catalyst for the thermochemical conversion of waste carbon streams. Its relevance to catalysis arises from a combination of cation-exchange capacity, swelling behavior, hierarchical porosity after modification, and the possibility of generating Brønsted, Lewis, redox and metallic active sites. This review critically evaluates bentonite modification strategies—acid activation, alkaline and sodium exchange, inorganic oxide pillaring, transition- and noble-metal impregnation, organosilane or surfactant functionalization, and carbon-based hybridization—with emphasis on their consequences for texture, acidity, thermal stability, metal dispersion and catalytic behavior. The review then connects these structure–property relationships with the emerging application of modified bentonites in plastic-waste thermocatalysis and hydrogen-rich product formation. The recent literature indicates that acid-modified bentonite can substantially improve liquid hydrocarbon formation from polyethylene, binder-free bentonite pellets can operate at kilogram-batch scale for drop-in fuels, and Ni-, Fe- or Ni–Fe-modified bentonite-type catalysts can promote tar cracking, reforming and gas upgrading. However, direct evidence for high hydrogen yields from plastic waste over bentonite remains narrower than the evidence for liquid-fuel production, biomass pyrolysis or model-compound reforming. Therefore, this article distinguishes between direct plastic-waste evidence and transferable evidence from biomass, acetic acid, tar and hydrocarbon reforming studies. The analysis identifies Ni-impregnated acid-activated or pillared bentonite, Ni–Fe/bentonite, and La/Ca-promoted Ni/bentonite as the most promising routes for plastic-derived hydrogen-rich syngas, while acid activation alone is best regarded as a pretreatment rather than a complete catalyst design. Key limitations include catalyst deactivation by coke, metal sintering, chloride poisoning from PVC, inconsistent reporting of gas yields, and insufficient life-cycle and techno-economic analysis. A roadmap is proposed for designing reproducible, scalable bentonite catalysts for circular plastic-waste valorization.

In this study, a new approach to stabilizing polypropylene (PP) melts using the bio-based antioxidant propyl gallate (PG) is considered. Since PG is extensively used in the food and cosmetics fields and its low doses do not cause reactions in humans, producing PP melts with PG is an interesting approach. Furthermore, PG is already actively used in the processing of natural polymers, for example, in the NMMO process. It is shown that introducing up to 0.2 wt.% PG into the system is sufficient to significantly reduce the decrease in melt viscosity during repeated PP processing. After five processing cycles, the viscosity of systems with PG decreases by less than an order of magnitude, while for melts without the antioxidant the viscosity drops by almost three orders of magnitude to 10 Pa s. For melts with antioxidant additives, the crossover point position in the frequency dependences remains virtually unchanged, indicating the preservation of the system’s elastic properties. Macrofibers were spun from the resulting melts, which can then be used for concrete reinforcement. For the spun fibers with PG, the strength decreased to 68.1 MPa after five passes, whereas for the PP fibers, the values did not exceed 31 MPa. The structure and properties of the fibers were studied using X-ray diffraction and IR spectroscopy, and contact angles were determined.

The study examines an industrial raffinate distillation column operating as part of an aromatic hydrocarbons recovery unit, for which a persistent deterioration in the sharpness of separation between the desorbent and C8 aromatic components has been observed during operation. Based on the analysis of plant data and steady-state process simulation using the Peng–Robinson equation of state, a comparison between the design and actual operating conditions was performed. It was established that the observed carryover of para-diethylbenzene into the side draw and the contamination of the bottoms product cannot be explained solely by operating parameters. To reproduce the actual temperature profile of the column in the model, it was necessary to reduce the overall tray efficiency in the upper section of the column to 17% (Murphree efficiency), indicating the presence of hydrodynamic disturbances and a decrease in the effective mass-transfer performance of the contacting devices. The product quality was shown to be highly sensitive to the combined variation of column pressure and reflux temperature, particularly under conditions of limited heat removal capacity during summer operation. The results demonstrate the need to reassess the condition of the internal contacting devices and substantiate the feasibility of hardware modernization of the column as a means of improving process stability and efficiency.

This review examines scientific and engineering strategies for adapting bituminous and asphalt concrete materials to the highly diverse climates of Central Asia. The region’s sharp gradients—from arid lowlands to cold mountainous zones—expose pavements to thermal fatigue, photo-oxidative aging, freeze–thaw cycles, and wind abrasion. Existing climatic classifications and principles for designing thermally and radiatively resilient pavements are summarized. Special emphasis is placed on linking binder morphology, rheology, and climate-induced transformations in composite bituminous systems. Advanced characterization methods—including dynamic shear rheometry (DSR), multiple stress creep recovery (MSCR), bending beam rheometry (BBR), and linear amplitude sweep (LAS), supported by FTIR, SEM, and AFM—enable quantitative correlations between phase composition, oxidative chemistry, and mechanical performance. The influence of polymeric, nanostructured, and biopolymeric modifiers on stability and durability is critically assessed. The review promotes region-specific material design and the use of integrated accelerated aging protocols (RTFOT, PAV, UV, freeze–thaw) that replicate local climatic stresses. A climatic rheological profile is proposed as a unified framework combining climate mapping with microstructural and rheological data to guide the development of sustainable and durable pavements for Central Asia. Key rheological indicators—complex modulus (G*), non-recoverable creep compliance (Jnr), and the BBR m-value—are incorporated into this profile.

Polypropylene (PP) is a highly sought-after synthetic polymer. Due to its properties, it has wide applications in a number of industries. One-dimensional molded materials (fibers and strands) are widely used in the textile and construction sectors. Concrete reinforcing using PP fiber is an intriguing use in construction. Fiber can be provided in two forms: fine fibers (microfiber) and extrudates (macrofiber). The macrofiber has a length of up to 60 mm and a thickness of up to 300 microns. The aim of the work was to obtain PP-based macrofibers from recycled polymer using the natural antioxidant tocopherol. The initial polymer is used to produce the fiber, whereas, in this work, it is proposed to use a secondary PP. Vitamin E, a natural antioxidant, was added to the system to stabilize the melts. It has been demonstrated that adding up to 0.5% Vitamin E reduces the heat degradation of the polymer and yields melts with the appropriate viscoelastic characteristics. Rheological data was used to determine the fiber’s formability window. Macrofibers were derived from melts with varying histories. Their structure was investigated using X-ray structural analysis and IR spectroscopy, and their mechanical characteristics were assessed.

In this study, polymer composites based on a polypropylene (PP) matrix with the addition of cellulose and ES-40, used as a silica precursor, were investigated. These composites were designed to achieve enhanced biodegradability through the incorporation of bioavailable cellulose and to enable subsequent carbonization into carbon–silicon carbide systems. Rheological investigations revealed that the multicomponent mixtures exhibited pseudoplastic behavior over the shear rate range typical of injection molding, ensuring process stability without additional plasticization. Morphological analysis demonstrated that an optimal balance of PP, cellulose, and ES-40 promoted the formation of a three-dimensional network structure, leading to a significant increase in flexural modulus at the equal flexural strength despite some reduction in tensile strength. It was further shown that substituting fibrous cellulose with microcrystalline cellulose improved the composite homogeneity, thereby enhancing the density and mechanical properties, especially in systems with low polymer contents. Preliminary pyrolysis experiments indicated that these injection-molded composites can serve as precursors for fabricating bulk thermally stable products containing silicon carbide particles. The obtained results underscore the high potential of the developed materials for applications in conventional injection molding, the possibility of additive manufacturing, and processes requiring subsequent carbonization.

This study focuses on the development of environmentally sustainable polypropylene (PP)-based composites with the potential for biodegradability by incorporating cellulose and the oligomeric siloxane ES-40. Targeting industrial applications such as fused deposition modeling (FDM) 3D printing, ES-40 was employed as a precursor for the in situ formation of silica particles via hydrolytic polycondensation (HPC). Two HPC approaches were investigated: a preliminary reaction in a mixture of cellulose, ethanol, and water, and a direct reaction within the molten PP matrix. The composites were thoroughly characterized using rotational rheometry, optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis. Both methods resulted in composites with markedly reduced crystallinity and shrinkage compared to neat PP, with the lowest shrinkage observed in blends prepared directly in the extruder. The inclusion of cellulose not only enhances the environmental profile of these composites but also paves the way for the development of PP materials with improved biodegradability, highlighting the potential of this technique for fabricating more amorphous composites from crystalline or semi-crystalline polymers for enhancing the quality and dimensional stability of FDM-printed materials.