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  • Artikel  (468)
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  • Artikel  (468)
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  • 1
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    Enhancement of Separation of Water–Oil Emulsion Using Unipolar Corona-Treated Polysulfonamide Membranes (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: The influence of unipolar-corona discharge treatment on the efficiency of separation of a model oil-in-water emulsion using polysulfonamide membranes with a molecular weight cut-off of 20 kDa (pore size ≈ 0.01 μm) has been investigated. It has been shown that the corona discharge treatment of the membranes leads to the intensification of the separation of water–oil emulsions and the process parameters depend on the processing time and the voltage applied to the corona electrode. The maximum value of the efficiency (95.4%) is noted in the case of the membrane treated in a corona discharge for 5 minutes at a voltage of 5 kV applied onto the electrode. The trends observed have been explained. It has been shown that the corona treatment promotes the hydrophilization of the membrane surface: the contact angle of water is α = 55° for the initial membrane and α = 50° after the corona treatment. Atomic force microscopy has shown a change in the structure of the membrane surface by the corona treatment—an increase in the roughness. A small decrease in the crystallinity of polysulfonamide by its treatment in a unipolar corona discharge has be been revealed.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
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    Production of Pure Hydrogen from Diesel Fuel by Steam Pre-Reforming and Subsequent Conversion in a Membrane Reactor (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: The results of experimental study and mathematical modeling of a fuel processor for the production of pure hydrogen from diesel fuel with a productivity of 600–700 g (H 2 )/h, consisting of an adiabatic reactor for diesel fuel pre-reforming followed by steam conversion of pre-reforming products in a catalytic Pd–Ag membrane reactor for hydrogen extraction are presented. The membrane reactor consists of 32 membrane modules arranged in 8 sections of 4 modules each. A mathematical model has been developed and two schemes of layout of the modules in the membrane reactor have been simulated. One scheme involves the cross-flow distribution of flue gas and fuel gas reformate to individual modules and leads to overheating of the input modules and cooling of the output modules. The other scheme with the cocurrent distribution of streams, along both the reactant path and the flue gas path, is preferable from the viewpoint of the temperature uniformity of different modules within a section. On the basis of the data obtained, an estimated calculation of the parameters of a power generation unit with a battery of low-temperature fuel cells has been made. For the example considered, the thermal efficiency of the fuel processor is 87%. With an efficiency of the fuel cell battery of 42%, the electrical efficiency of the fuel cell power unit will be 36%.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 3
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    Effect of Functionalization and the Nature of Ionogenic Groups of Hyperbranched Polymers on the Electrochemical Characteristics of Asymmetric Bipolar Membranes (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: Asymmetric bipolar membranes modified with phosphorylated and carboxylated hyperbranched polymers with different degrees of functionalization have been synthesized and studied. The effect of the nature of ionogenic groups of functionalized polymers on both individual electrochemical characteristics of asymmetric bipolar membranes and their efficiency in adjusting the pH of dilute solutions by electrodialysis has been studied. It has been found that an increase in the degree of functionalization of hyperbranched polymers leads to an increase in the current efficiency and a decrease in the voltage drop across the asymmetric bipolar membranes.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 4
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    Short Side Chain Aquivion Perfluorinated Sulfonated Proton-Conductive Membranes: Transport and Mechanical Properties (2018)
    Springer
    Details
    Publikationsdatum: 2018-03-07
    Beschreibung: Data on the water uptake, proton conductivity, diffusion permeability, cation transport selectivity, and mechanical properties of short side chain Aquivion sulfonated perfluoropolymer membranes with an equivalent weight of 870 and 965 have been described. Properties of the membranes have been compared with those of a long side chain Nafion 212 membrane (equivalent weight of 1100). An increase in the equivalent weight leads to an increase in the sorption exchange capacity and water uptake of the membranes and a decrease in their proton conductivity. The conductivity of the Aquivion membrane with an equivalent weight of 870 is 1.4–1.5 times higher than that of the Nafion 212 membrane; it reaches 13.6 mS/cm in contact with water and 1.0 mS/cm at a relative humidity of 32% at 25°C. Diffusion permeability and cation transport selectivity exhibit a nonmonotonic dependence on the equivalent weight of the material. The lowest diffusion permeability, the highest Na + cation transport selectivity (99.5%), and the best mechanical properties have been found for the Aquivion membrane with an equivalent weight of 965, which is characterized by the highest degree of crystallinity.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 5
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    Study of Separation Characteristics of a Hybrid Membrane–Sorption System (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: A hybrid membrane–sorption system for air separation at elevated pressures has been studied. A procedure for determining the cyclograms of operation of the hybrid system has been proposed. The effect of vacuum regeneration on the separation characteristics of the hybrid membrane–sorption system has been examined. A new scheme of a hybrid membrane–sorption system with vacuum regeneration of the sorbent is proposed.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 6
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    Influence of Gravitational Convection on Current–Voltage Characteristics of an Electromembrane Stack in Sodium Dihydrogen Phosphate Solution (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: The features of gravitational convection in electromembrane systems with electrolytes whose ions exhibit amphoteric properties have been studied using voltammetry techniques in the vertical and horizontal positions of a membrane stack. It has been shown that gravitational convection has approximately the same effect on these characteristics as in the case of solutions that do not exhibit amphoteric properties (sodium chloride). The main difference in the behavior of systems containing amphoteric compounds is the influence of gravitational convection on the values of the second limiting current, which is not observed in systems containing ions that are not capable of protonation/deprotonation reactions.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 7
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    Mathematical Modeling of Ion Transport and Water Dissociation at the Ion-Exchange Membrane/Solution Interface in Intense Current Regimes (2018)
    Springer
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    Publikationsdatum: 2018-03-07
    Beschreibung: At current densities exceeding the limiting current density, H + and OH − ions are generated at the interface of the ion-exchange membrane with a depleted solution as a result of the dissociation of water molecules. At present, it is generally accepted that water splitting occurs in a thin (a few nanometers) layer inside the membrane, this reaction being catalytic in nature. The mathematical model of ion transport in the diffusion layer near the membrane surface has been constructed and numerically studied under conditions when dissociation and recombination processes involving water molecules and H + and OH − ions occur simultaneously. It has been shown that in overlimiting current regimes under very high voltages, intense noncatalytic dissociation of water molecules in the extended space charge region of the depleted solution can occur irrespective of the catalytic splitting of water. Since this region has macroscopic dimensions, the rate of noncatalytic water dissociation is comparable with the rate of the corresponding catalytic process. The obtained results significantly supplement modern concepts of the mechanism of generation of H + and OH − ions in membrane systems, showing that this process can proceed not only in accordance with the conventional mechanism with the catalytic participation of functional groups and/or other compounds, but also via the noncatalytic mechanism that has not been taken into account to the present.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 8
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    Ultrafiltration of Oil-in-Water Emulsions with a Dynamic Nylon–Polystyrene Membrane (2018)
    Springer
    Details
    Publikationsdatum: 2018-03-07
    Beschreibung: Dynamic nylon–polystyrene membranes with polystyrene contents of 2.6 and 4.1 wt % have been obtained by applying polystyrene with a particle size of 142–452 nm onto the surface of a nylon membrane with a pore size of 0.45 μm. The deposition of polystyrene onto the surface of the nylon membrane was indirectly confirmed by Fourier-transform IR spectroscopy and probe microscopy. The contact angle of distilled water on the membrane has been found to increase from 44.5° to 106.2° as a result of the deposition of polystyrene particles onto the surface of the initial membrane. The specific productivity of the initial and modified membranes with respect to distilled water and a water–oil emulsion was determined. It has been found that the membrane modification leads to an increase in the degree of removal of petroleum products from an oil-in-water emulsion by 62%; the size of particles separated by the membrane after modification decreased from 450 to 151 nm. It has also been revealed that the specific productivity of the nylon–polystyrene membrane and the original nylon membrane is restored to 98 and 90% of the initial values, respectively, by regeneration.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 9
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    Genesis of higher petroleum alkyltoluenes (2018)
    Springer
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    Publikationsdatum: 2018-03-06
    Beschreibung: The genesis of higher alkyltoluenes with a normal alkyl chain ( n -ATs) has been studied. The conditions for their formation from both individual C 18 (oleic and stearic) fatty acids and C 14 alcohol in the thermocatalytic mode and from Tasmanites planktonic algae during noncatalytic thermal treatment have been considered. The feasibility of the formation of n -ATs has been confirmed by determining their composition and structure.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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  • 10
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    Oxidative dehydrogenation of propane over vanadium catalyst supported on nano-HZSM-5 (2018)
    Springer
    Details
    Publikationsdatum: 2018-03-06
    Beschreibung: Vanadium catalyst supported on nano-HZSM-5 was utilized in oxidative dehydrogenation of propane to propylene. The physicochemical properties of the elaborated catalysts were investigated by means of XRD, SEM, FTIR spectra, UV-vis, Raman, NH 3 -TPD and H 2 -TPR techniques. The effect of vanadium loading (2–10 wt %), temperature (500–600°C) and oxygen to propane ratio (0.5–1.5) on conversion, propylene and ethylene selectivity was studied using full factorial design of experiments. The obtained data were statistically analyzed using the Analysis of Variance (ANOVA) and a p 〈 0.05 was considered statistically significant. The mathematical relationship of conversion, propylene and ethylene selectivity on three independent variables approximated by a second-order quadratic model. Two-dimensional contour plots were drawn to investigate the effect of independent variables and their interaction on the chosen responses. The function of temperature, oxygen to propane ratio and vanadium content such as acidity and reducibility on the performance of supported vanadium catalysts were discussed.
    Print ISSN: 0965-5441
    Digitale ISSN: 1555-6239
    Thema: Chemie und Pharmazie
    Publiziert von Springer
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