Ашық рұқсат
Рұқсат берілді
Тек жазылушылар үшін
Том 15, № 3 (2025)
Articles
Gas permeability of membranes based on crystallizable poly(hexadecylmethylsiloxane)
Аннотация
In this work, the membranes based on crystallizable poly(hexadecy-l-methyl-siloxane) (PHDMS) were obtained and their gas transport properties in relation to a number of light hydrocarbons were investigated with a focus on n-butane and methane permeability and selectivity. A first-order phase transition (crystallization of side alkyl chains) with a melting temperature (Tm) of 26°C was detected for the PHDMS-membranes. It was shown that the membrane transport properties were significantly influenced by their phase state. The gas permeability, diffusivity and solubility undergone a sudden change in the vicinity of Tm. Thus, a decrease in temperature from 30° to 20°C leads to a decrease in the hydrocarbons permeability coefficients by an order of magnitude. On one hand, the membranes n-butane/methane selectivity at a temperature T > Tm did not exceed 25, which is comparable with the results for previously studied polyalkylmethylsiloxanes with shorter alkyl chains. On the other, the n-butane/methane selectivity of semicrystalline membranes (T < Tm), despite a noticeable reduction in gas permeability, can reach selectivity values of ~150.
Membrany i membrannye tehnologii. 2025;15(3):151-161
151-161
Composite Polysiloxane Membranes with High Selecty and Permeability for Monomer Recovery from Propylene Polymerization Purge Gases
Аннотация
The transport properties of composite membranes based on polyalkylsiloxanes POMS/MFFK, PDMS/MFFK and acommercial membrane MDK-3 have been studied for individual gases N2, CO2, He, C3H6 and for a mixture of C3H6/N2 with a concentration ratio of 20/80%. It has been found that the selectivity of the membranes increases with an increase in the proportion of hydrocarbon fragments in the polymer. It has been shown that due to swelling of the selective layer material, it is necessary to study the transport properties during the separation of gas mixtures. It has been found that composite membranes based on polydecylmethylsiloxane surpass the studied polymer membranes in C3H6/N2 selectivity when separating a gas mixture simulating the propylene polymerization blowdown gas. The selectivity of the PDMS/MFFK membrane in a mixture of propylene/nitrogen gases was 21. At the same time, the permeance of the PDMS/MFFK membrane for propylene is at a high level, reaching 550 GPU. This result indicates the potential for using composite membranes with a PDMS-based selective layer for the recovery of monomers from polymerization blowdown gases.
Membrany i membrannye tehnologii. 2025;15(3):162-173
162-173
Extraction mode in a reactor with a membrane catalyst
Аннотация
A kinetic experiment in the process of dry reforming of methane was performed for the first time in a reactor with a membrane catalyst for the extractor mode, in which the hypothesis of activated mass transfer based on the phenomenon of thermal slip was used for the analysis of the results. The results obtained show that in both parts of the reaction space (in the retentate and in the permeate) of the membrane reactor, intensification of the intermediate stages of dry reforming of methane is observed, compared with the contactor modes. Unlike the contactor modes, in which the methane cracking stage is shifted toward the formation of products of this reaction, in the extractor mode, the process occurs near equilibrium, and the constants of the direct and reverse reactions are close. In this mode, the reverse reaction of the water shift is strongly shifted toward the formation of water gas.
Membrany i membrannye tehnologii. 2025;15(3):174-188
174-188
Selection of Anion Exchange Membranes for Optimization of Electrodialytic Extraction of Tartrates from Aqueous Solutions
Аннотация
The challenge of extracting organic acids using membrane technologies highlights the critical issue of reducing production costs and improving environmental efficiency in food and medical industries. Organic acids play a key role in manufacturing a wide range of products. Electrodialysis (ED) has established itself as a highly efficient, environmentally friendly, and economical extraction method, particularly for tartrates. During extensive testing focused on extracting tartrates from solutions via electrodialysis, a comparative study of three types of ion-exchange membranes was conducted: ASE, CJMA-3, and MA-41P. Results showed significant differences in efficiency and energy consumption among these membranes. Data were obtained in NaxH(2–x)T solution with pH 3.0, characterized by the maximum molar fraction of monovalent tartrate anions. It was demonstrated that the ASE membrane exhibits inferior mass transfer characteristics and higher energy consumption during the electrodialytic extraction of tartrates compared to the CJMA-3 membrane, despite having the highest experimental limiting current values. The MA-41P membrane, in turn, demonstrates high mechanical strength, resistance to damage, and extended service life. However, its efficiency in tartrate extraction over the same electrodialysis period proved lower than that of the CJMA-3 membrane. Thus, CJMA-3 is preferable for ED processing of tartrate-containing solutions.
Membrany i membrannye tehnologii. 2025;15(3):189-199
189-199
Diffusion of acetic, malonic and citric acids through commercial anion-exchange membranes and modified anion-exchange membrane Ralex AMH
Аннотация
This work is devoted to the investigation of the neutral salts diffusion, sodium acetate, sodium malonate, and sodium citrate through heterogeneous anion-exchange Ralex AMH, MA-41, and MA-40 membranes, through the homogeneous Lancytom AHT membrane, and the two-layer Ralex AMH/MF-4SK membrane from 0.1–0.5 mol-eq/L solutions into deionized water. Diffusion, as one of the ion transport mechanisms during the synthesis of organic acids from their salts using electromembrane methods, affects the main electrochemical characteristics of these processes. It is shown that the differential diffusion permeability coefficients (K) of salts through the homogeneous membrane are several times lower than those through heterogeneous membranes. In the series “sodium acetate – sodium malonate – sodium citrate,” the slope of the K coefficient dependence on the salt concentration changes from positive to negative. Calculating the ionic composition of the solution formed after the experiment using pH and specific conductivity shows that, in addition to neutral salts, it contains hydrolysis products—acetic acid, hydromalonates, and hydro- and dihydrogen citrates. These hydrolysis products increase the solution’s specific conductivity and may be the cause of the negative slope in the K coefficient dependence on the sodium citrate concentration across membranes. The effect of hydrolysis of neutral salts of polybasic acids must be taken into account when measuring the K coefficient using the salt diffusion method through a membrane into deionized water.
Membrany i membrannye tehnologii. 2025;15(3):200-210
200-210
Ultrafiltration purification of waste motor oil using tubular polymer membranes
Аннотация
This paper considers the process of waste motor oil (WMO) purification using tubular polymer micro- and ultrafiltration membranes based on fluoroplastic with an average pore size of 0.5 and 0.05 μm with varying separation modes: transmembrane pressure of 0.2–0.5 MPa, temperature of the separated medium of 313–353 K. It is shown that the ultrafiltration membrane has a higher retention capacity for asphalt-resinous degradation products compared to the microfiltration membrane. Thus, the kinematic viscosity coefficient in the permeate after the UFFK membrane decreased from 10.84 to 4.76 mm2/s, and after the MFFK membrane - from 10.84 to 7.9 mm2/s. The highest efficiency of the purification process was achieved by the ultrafiltration method at a transmembrane pressure of 0.3–0.4 MPa and a temperature of 343–353 K. Analysis of the IR spectra of the original waste oil and permeate showed that membrane filtration allows for the effective removal of oxidation products from WMO without changing its hydrocarbon composition, which confirms the potential of this technology for the regeneration of waste oils.
Membrany i membrannye tehnologii. 2025;15(3):211-219
211-219