Russian Journal of Applied Chemistry最新文献

A fin-fluidized bed heat exchanger was examined experimentally to improve the bed-to-surface heat transfer coefficient. The investigation was carried out in four stages (single tube heater, five internals equipped with a tube heater, single longitudinal fin tube heater, and five internals equipped with longitudinal fin tube heater) and was placed and moved at a different position in and around the center. The effect of vertical longitudinal fins with heat-exchanging tube bundles on the heat transfer coefficient (HTC) in a gas-solid fluidized bed has been studied locally and instantly. A sophisticated heat transfer technique and silica sand as a solid particle of 600 µm average size with a bulk density of 1570 kg/m³ were used. The experiments were performed in a Plexiglas fluidized bed reactor 0.13 m diameter with varied gas flow rates (0.215‒0.353 m/s). The study was initially without a fin, the tube heater was 0.012 m in diameter and 40 cm in length, then with a longitudinal fin (1.5 mm thickness, 7 mm height, and 400 mm length). The fluidized bed reactor with longitudinal fins and vertical tubes has been found to have a 47% lower local heat transfer coefficient than the reactor with bare vertical tubes. The findings show that even though using fins reduces the heat transfer coefficient, the overall heat transfer increases due to the increased surface area. It is observed that smooth and finned tube heat transfer coefficients increase as the fluidizing velocity increases.

Energy consumption in buildings has increased significantly over the past decade due to population growth, increased demand for buildings and global climate change. Over forty percent of the main energy used worldwide is presently consumed in buildings. Because of this, creating energy-efficient buildings can offer substantial remedies for the severe danger that carbon emissions and energy shortages pose to our quality of life. Zero Energy Buildings (ZEBs) can be an efficient way to lower energy consumption in the residential building sector in a hot and dry climate like Iraq. In order to achieve ZEB while simultaneously lowering potentially harmful environmental impacts, reducing carbon emissions and reducing the impact of global climate change. This research offers a brief overview of the most recent approaches for ZEBs technologies, which can be summed up in three categories: energy-saving passive technologies, energy-efficient building services systems (active), and renewable energy production technologies.The research aims to develop an advanced solution that combines different scenarios to transform residential buildings into zero-energy or close to zero energy buildings. The scenarios investigated include optimal design, envelope insulation system, shading, glazing treatment, use of smart systems for heating, cooling, and air conditioning (HVAC), the use of smart lighting systems and energy-saving devices, using solar photovoltaic panels as renewable energy technologies. In order to verify the proposed solutions. The research methodology was to apply these treatments to a residential building in Iraq. The energy simulation program (Design Builder) is used to determine the amount of savings in energy consumption and the amount of reduction in carbon emissions in the residential building. The results of the research show that the maximum reduction rate of energy demand for cooling and heating by (87%) was achieved by changing the building insulation, ventilation and shading systems compared to the traditional residential building. In addition, the scenarios of using building insulation and the use of three-layer glass have the greatest impact on reducing energy demand by an overall reduction of (59%) compared to other scenarios. CO₂ emissions were significantly reduced after the use of insulation materials and the highest decline was recorded by 49% after the use of wall insulation material. A solar cell system was used on the roof to provide the building with the energy needed to operate it. The results highlighted that the effects of the main scenarios that were applied in combination to achieve ZEB should be considered. There is a wide possibility of achieving ZEB locally for small buildings, despite the fact that Iraq is located within areas with a hot and dry climate. Most buildings can be developed to reach zero, near-zero or efficient buildings.

Non-metallic carbonaceous materials, among numerous non-mercury catalysts, display great prospects for acetylene hydrochlorination, which are mainly attributed to their wide source of raw materials, low price and easy adjustment of chemical structure. Although the abundant functional groups on the surface of carbon materials may affect the progress of acetylene hydrochlorination, the research on the catalytic mechanism is still scarce. In the present study, biomass-derived-carbon material contained many heteroatoms was prepared by hydro-thermal treatment using kitchen waste onion as raw material. The obtained carbon catalyst enabled excellent catalytic activity with the highest acetylene conversion of 96.4% at an acetylene gas hourly space velocity (GHSV) of 30 h^–1, which was attributed to the high contents of pyridine–N, graphite–N and –C=O. Among them, the high contents of pyridine–N and –C=O species provided abundant alkaline sites, which enhanced the adsorption and activation ability of catalyst for HCl. Simultaneously, the abundant graphite-N species acted as the adsorption site to activate C₂H₂, thus together accelerating the process of acetylene hydrochlorination. This work provides an innovative idea to design the environment-friendly carbon-based catalysts for acetylene hydrochlorination.

The effect of the rubidium nitrate amount on the phase with Dion–Jacobson structure RbBi₂Ti₂NbO₁₀ formation during solid-state synthesis was studied. It was found that the rubidium nitrate content from the stoichiometric amount to 50 mol % favors the formation of a phase with the Dion–Jacobson structure, and at a higher concentration of the salt precursor, the Aurivillius phase is predominantly formed. Moreover, when using a significant excess of rubidium nitrate, the possibility of layered perovskite phase transition from the Aurivillius family to the Dion–Jacobson phase was discovered with an increase in the heat treatment temperature. It is due to the volatility of the rubidium-containing component and the mobility of ions located between the BO₆ octahedra in perovskite blocks (Bi³⁺ cations) and in the interlayer space (Rb⁺ cations). The introduction of excess rubidium nitrate does not significantly affect the unit cell parameters of solid solutions based on RbBi₂Ti₂NbO₁₀, which also indirectly indicates the possibility of mutual migration of rubidium(I) and bismuth(III) cations between the positions occupied in the structure. The symmetry of the unit cell of the obtained phases belongs to the tetragonal syngony. An increase in the loss of the rubidium-containing component from 40 to 47% with an increase in the excess of the initial rubidium nitrate in the mixture is shown.

The physicochemical principles of the bromination of ultra-high molecular weight polyethylene (UHMWPE) have been investigated. The conditions and regimes for conducting the process have been substantiated, and the kinetic characteristics of the process have been studied. Possible mechanisms of the UHMWPE bromination reaction have been considered. The experimental data from the UHMWPE bromination process were characterized using known kinetic models. The kinetic constants of the equations describing the bromination process were calculated. It was established that the Elovich model most adequately describes the process under study. It has been proposed that the bromination of UHMWPE is a three-stage process. In the first stage, molecular bromine migrates from the solvent medium to accessible adsorption centers. The second stage involves chemisorption. The final stage is the direct free-radical bromination. It was found that the conditions of the chosen technology allow for the production of brominated UHMWPE (B-UHMWPE) containing from 10 to 46 wt % bromine. It was shown that partial polymer degradation occurs during the process, resulting in a decrease of the initial polymer molecular weight by approximately 2.54 times. The IR spectra of brominated UHMWPE, alongside absorption bands for methyl and methylene group vibrations, contain absorption bands for C–Br bond vibrations (absorption maxima at 540, 614 cm^–1). Scanning electron microscopy revealed that the supramolecular structure of B-UHMWPE differs from that of UHMWPE, showing some densification of structural elements with a simultaneous increase in their size distribution. Energy-dispersive X-ray analysis confirmed the presence of bromine and its uniform distribution throughout the UHMWPE volume. X-ray photoelectron spectroscopy (XPS) established that in the spectrum of the B-UHMWPE sample, besides the carbon line, peaks appear at 286.9 and 288.4 eV, corresponding to the (C–Br) bond. Also, in the Br3d region, a doublet is observed with a binding energy of the Br3d_5/2 component equal to 70.5 eV, which is characteristic of bromine atoms covalently bonded to carbon atoms (Br–C). The mechanical characteristics of B-UHMWPE and a polymer composite material (PCM) based on UHMWPE with B-UHMWPE were investigated. It was found that the strength characteristics of B-UHMWPE are understandably inferior to those of the initial UHMWPE due to the decrease in molecular weight. The introduction of up to 9.5 wt % B-UHMWPE into the UHMWPE polymer matrix allows for an increase in the elastic modulus of the PCM by 1.4 times but does not lead to a statistically significant change in the elongation at break and tensile strength. Thus, B-UHMWPE can be used as a promising modifier for improving the deformation-strength parameters of UHMWPE-based composite materials.

In this study, we investigate biodiesel extracted from castor oil as an alternative to conventional energy sources. Two significant reasons motivated the exploration of the castor plant. First, castor trees are abundant in southern Algeria, particularly in the El Oued desert. Second, the biodiesel was extracted from castor oil through catalysis with methanol, achieving a yield of around 64%. Also, we compared the properties of our biodiesel with those of castor oil biodiesel from Egypt and Nigeria, as reported in the literature. Furthermore, we tested the biodiesel’s performance by blending it with petrodiesel to fuel an electrical generator. This phase of the study focused on evaluating environmental and energy-related parameters under different engine loads and fuel compositions. The results demonstrated the positive impact of using biodiesel as a green fuel, including reduced emissions and improved engine efficiency. These findings support the potential of biodiesel as a viable alternative fuel. Finally, based on the parameters obtained in this study, Algerian castor seed kernels can be considered a promising feedstock for oil and biodiesel production.

The article is dedicated to studying the potential for enhancing the durability of elastomeric materials based on ethylene–propylene–diene rubber, containing modified aluminosilicate microspheres, against the effects of tropical climates, which include elevated temperatures, humidity, and ultraviolet radiation. The research findings will improve the reliability and extend the service life of rubber products used in tropical regions, which is significant for various industrial sectors—from automotive to construction and energy. Annual field tests of the developed rubbers were conducted in climatic conditions at the Kon Zo and Dam Bay stations in Vietnam. Analysis of the results shows that the addition of unmodified aluminosilicate microspheres to the elastomeric materials has little effect on their resistance to tropical climates. However, the created compositions demonstrated greater durability during testing at the Dam Bay station, where both ultraviolet radiation and high humidity are present. It was shown that the combined treatment of aluminosilicate microspheres with an organoelement modifier and low-temperature plasma contributes to an increased retention of physical and mechanical properties—the samples lose 10–19% less strength and experience virtually no loss in hardness compared to the control sample.

Pyridinium chlorides were obtained in high yield by the reaction of substituted pyridines with benzyl chloride. The obtained compounds proved to be effective corrosion inhibitors for steel in mineralized aqueous media containing dissolved oxygen. The degree of protection is 94–98% at inhibitor dosages of 25–100 mg/L. The substances are highly soluble in water, making them promising for practical applications.

The goal of bone tissue engineering is to develop substitute materials that overcome the limitations of metallic orthopedic implants. Despite the remarkable and successful application of orthopedic surgery and bone replacement, persistent challenges arise from deep infection, double fracture, bone cancer, as well as the prevalence of osteoporosis and post-surgery infections. These complex damage and fractures in bone tissue, which leave remnant deformation, necessitate the development of synthesized biomaterials for bone replacement or repair. This study fabricated novel bio-nano composite bone scaffolds using two types of nanosized fillers: 8 mol % CaO–PSZ (partially stabilized zirconia) and TiO₂ (titanium dioxide) in an HDPE (high-density polyethylene) polymeric matrix. We generated the bio-nano composites using different compression pressures (29, 114 MPa) and a constant temperature of 150°C for 15 min, resulting in disk-shaped specimens with diameters of 14.7 mm and heights ranging from 7 to 10 mm. The primary objective was to identify the ideal mechanical and physical characteristics of the nanocomposite CaO–PSZ–TiO₂/HDPE, which could serve as bone substitute materials in bone tissue engineering. We conducted characterization of the scaffolds using density and porosity for physical analysis, hardness and fracture strength for mechanical analysis, and X-ray diffraction for radiological analysis. The study confirmed that the hybrid bio-composites had good structural integrity, a uniform fibrous structure, and better mechanical properties when ceramic fillers and hot-press pressure were added. Furthermore, the (70% HDPE-15%TiO₂–15%CaO–PSZ) recorded the highest fracture strength (24.02 MPa) at 86 MPA compression pressure, making this bio-nano composite ideal for bone substitutes.