Petroleum Chemistry (v.55, #10)

Titanium dioxide thin films have been prepared by reactive sputtering onto the surface of tracketched polyethylene terephthalate membranes using an inverted dc magnetron, and their structural and physicochemical properties have been examined. A silver film applied onto the membrane surface by physical vapor deposition has been used to protect the polymer from the photocatalytic action of titanium dioxide. The structural characteristics of the composite membranes have been studied by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, spectrophotometry, and atomic force microscopy. The effects of photoinduced surface hydrophilization and catalytic decomposition of the dye rhodamine 6G have been investigated.
Keywords: track-etched membrane; thin films; titanium dioxide; reactive magnetron sputtering; photocatalysis

Evaluating the effectiveness of ion exchangers for the electrodeionization process by D. V. Golubenko; J. Křivčík; A. B. Yaroslavtsev (769-775).
A method for the evaluating the performance of ion exchange resins in the electrodeionization process has been proposed. This method is based on the study of the ion exchange kinetics and involves experimental determination of three parameters: the particle size distribution, the ion-exchange capacity, and ion exchange rate constants. Using these parameters, ionic conductivity has been calculated, the value of which has been used for estimating the effectiveness of ion exchangers. Fourteen brands of cation exchange resins have been studied using the proposed procedure. It has been shown that the best grades are lightly crosslinked Amberlyst BD20 and Amberlyst 131WET. In addition, the “granulate”, a potential ion exchange packing for use in electrodeionization, composed of the ion exchange resin by 60% has been investigated. The rate of ion exchange on the best granulate sample has appeared to be 12 times lower than that on the best ion exchange resins.
Keywords: electrodeionization; ion exchange kinetics; ion exchange resins; ionic conductivity

Simulation of external mass transfer in hollow-fiber membrane contactors by V. A. Kirsch; V. I. Roldugin; S. D. Bazhenov; T. V. Plisko (776-782).
External transverse laminar flow of a viscous incompressible fluid and convective diffusion of a solute in a model membrane contactor with a regular system of monodisperse fibers have been numerically simulated. A row of equally spaced parallel fibers was taken as the simplest model system, for which the dependences of the drag force and the efficiency of solute absorption by the fiber (Sherwood number of fiber) upon the distance between the axes of adjacent fibers, and the Reynolds and Peclet numbers have been calculated. The influence of the flow inertia has been studied, and it has been shown that the flow field and mass transport in the contactor can be described in terms of the linear Stokes approximation up to as high Reynolds numbers as dense is the fiber array.
Keywords: membrane contactor; two-dimensional flow; hollow fiber membrane; fiber row; convective diffusion; Reynolds number; Peclet number; Sherwood number

Study of accessible free volume and transport properties of TFPS-co-TMSP copolymer by A. A. Kossov; A. A. Yushkin; V. S. Khotimskiy; A. V. Volkov (783-790).
Copolymers of 1-trimethylsilyl-1-propyne (TMSP) with 1-(3,3,3-trifluoropropyldimethylsilyl)1-propyne (TFPS) as part of a systematic series with the TFPS content of the final polymer in the range of 0 to 46 mol % have been synthesized. The resulting samples have been characterized by different instrumental methods including NMR, IR, and DSC techniques. It has been shown that the accessible free volume of the polymer decreases from 30.4 to 19.1% with an increase in the proportion of TFPS units. Moreover, the gas transport properties of the membrane materials are reduced by factors of 30 (oxygen), 50 (nitrogen), and 15 (carbon dioxide), although the selectivity for the O2/N2 and CO2/N2 gas pairs increases from 1.6 to 2.5 and 2.5 to 11.5, respectively. A study of nanofiltration of organic media has shown that the ethanol permeability through the TFPS-co-TMSP copolymer material is reduced by no more than 30%, a value that is comparable with the relative decrease in the fractional free volume of the polymer. An increase in the TFPS content has improved the stability of the membrane material in ethanol (swelling ratio decreased from 61 to 39%), thereby resulting in an increase in the retention of the Orange II anionic dye (350 g/mol) from 89 to 94%.
Keywords: PTMSP; TFPS-co-TMSP; nanofiltration; gas separation; free volume

IR spectroscopic and thermogravimetric study of state of water in MGA-95 cellulose acetate membrane by S. I. Lazarev; Yu. M. Golovin; D. S. Lazarev; V. M. Polikarpov (791-794).
The state of water in the MGA-95 composite cellulose acetate membrane has been investigated using the techniques of IR spectroscopy and thermogravimetry. It has been concluded that water, acting a plasticizer, structures macromolecules of the amorphous phase of the cellulose acetate membrane and promotes its transition to a liquid crystal phase forming additional capillary spaces.
Keywords: membrane; IR spectra; thermogravimetric method; liquid crystal phase; amorphous phase

Modification of hollow fiber ultrafiltration membranes by interfacial polycondensation: Monomer ratio effect by E. S. Liubimova; A. V. Bildyukevich; G. B. Melnikova; V. V. Volkov (795-802).
The effect of the component ratio on the permeability and contact angle of ultrafiltration polysulfone hollow fiber membranes modified by interfacial polycondensation of triethylenetetramine (TETA) and isophthaloyl chloride (IPC) has been studied. It has been found that the dependence of the rejection factor on the monomer ratio in the TETA: IPC range from 1: 28 to 20: 1 has two peaks. The first rejection peak is observed in a narrow range of TETA: IPC ratios close to 7: 1. The second peak is observed in a rather broad range of isophthaloyl chloride excess, at TETA: IPC equivalent ratios 1: (5–15). The membrane pure water flux was shown to change conversely to the rejection coefficient. The influence of the average functionality of the system on the change in the selectivity of the modified membranes was studied. A correlation between hydrophilicity and permeability of the modified membranes was revealed: with decreasing contact angle the pure water flux enhances, and the rejection coefficient decreases.
Keywords: polysulfone; hollow fiber membrane; permeability; interfacial polymerization; modification; hydrophilization

Gas transport properties of membranes based on a blend of two silicon-hydrocarbon polymers, poly(trimethylsilylpropyne) (PTMSP) and poly(vinyltrimethylsilane) (PVTMS), have been investigated. The N2 and CO2 permeability of the membranes decreases by two orders of magnitude, and CO2/N2 selectivity increases about threefold with increasing PVTMS content in the blend from 0 to 100%. The effect of the volume contraction of the membranes has been found. The results of the experiments and calculations showed that the membrane properties throughout all the range of concentrations are in good agreement with the single-phase blend permeability model. The results of the research open the possibility of preparing PTMSP/PVTMS membranes with stable gas separation properties combining a high permeability of PTMSP and a rather high selectivity of PVTMS.
Keywords: poly(trimethylsilylpropyne); poly(vinyltrimethylsilane); polymer blends; gas permeability

Evaluation of the catalytic activity of the composite track-etched membranes for p-nitrophenol reduction reaction by A. A. Mashentseva; D. B. Borgekov; D. T. Niyazova; M. V. Zdorovets (810-815).
The catalytic properties of composite materials produced by electroless deposition of gold and silver into nanosized channels of polyethylene terephthalate (PET) track-etched membranes (TeMs) have been addressed. Applying the activation solution with sodium potassium tartrate as a reducing agent makes it possible to prepare PET/Ag/Au composites. The dimension (wall thickness), the structure, and the composition of the deposited metallic nanotubes have been determined by scanning electron microscopy and energy dispersive X-ray diffraction analysis. Liquid-phase reduction of p-nitrophenol as a model system has been used to examine the catalytic activity of the composites, and catalytic ability has been studied as a function of the nanotube wall thickness. It has been found that the mixed PET/Ag/Au composite can mediate the reaction to the most complete extent at the highest rate, with the catalytic activity remaining quite high for five consecutive test cycles.
Keywords: track-etched membranes; template synthesis; silver and gold nanotubes; catalytic activity; reduction of p-nitrophenol

Characteristics of PD-sensors based on hybrid perfluorinated membranes in aqueous solutions of inorganic electrolytes and lysine by A. V. Parshina; E. A. Ryzhkova; E. Yu. Safronova; D. V. Safronov; A. A. Lysova; O. V. Bobreshova; A. B. Yaroslavtsev (816-821).
The characteristics of PD-sensors based on MF-4SC perfluorosulfonic cation-exchange membranes, particularly those containing surface-functionalized silica nanoparticles, in HCl, NaCl, KCl, CaCl2, and lysine monohydrochloride solutions have been studied. It has been revealed that the degree of hydration of inorganic cations has a dominant effect on the magnitude of PD-sensor response in individual electrolyte solutions. It has been shown that the response and sensitivity of PD-sensors based on hybrid materials with respect to lysine cations increase with increasing concentration of amino groups grafted to SiO2. This feature is attributed to an increase in the counterion concentration in the film owing to a decrease in the water uptake and enhancement of the interaction between the counterions and the functional groups (sulfo groups of membrane, amino groups of dopant) in membrane.
Keywords: Donnan potential; PD-sensor; ionic conductivity; hybrid membranes; lysine

Synthesis and study of hybrid materials based on a nafion membrane and hydrated titania by E. Yu. Safronova; D. V. Safronov; A. A. Lysova; O. V. Bobreshova; I. A. Stenina; A. B. Yaroslavtsev (822-826).
The properties of hybrid membranes based on a perfluorosulfonated Nafion polymer and hydrated titania are described. The membranes have been prepared by casting from a solution containing particles of a dopant preformed by precipitation at different pH values or a precursor for further synthesis of titania. The dependence of the conductivity of these samples on relative humidity and temperature has been studied. Modification leads to an increase in the proton conductivity of the membranes; higher values are obtained for the samples prepared using preformed TiO2 particles. It has been shown that the background of the dopant has an effect on the conductivity value: at low relative humidity, higher values are obtained using titania with a higher degree of hydration. The introduction of small amounts of the dopant (1.5–3 wt %) leads to an increase in the cation transport selectivity compared to that of the unmodified membrane.
Keywords: hybrid membranes; Nafion; titania; diffusion permeability; proton conductivity

The entry of high-energy Kr, Xe, and Bi ions into the surface of poly(ethylene terephthalate) (PET) and mica has been imaged. It has been shown that the track images have the shape of protuberances in both cases. The formation of protuberances is associated with the degradation of the material in the track region, in the formation of an amorphous structure, and the release of low-molecular radiolysis products as gaseous compounds. Holding the irradiated PET samples in water and dilute alkaline solution for several hours changes the surface topography due to hydrolysis of the material and escape of the radiolysis products to the solution. The kinetics of track etching in the dilute alkaline solution and pore formation have been studied. The electrical resistance and the permeability of the tracks in KCl, LiCl, MgCl2, and BaCl2 electrolytes have been measured.
Keywords: track; heavy ions; poly(ethylene terephthalate); membrane

The preparation of composite catalytic membranes as a type of heterogeneous catalysts is considered. The necessity of the use of a catalyst material (bulk or supported) for the formation of the functional layers (selective or catalytic) of a catalytic membrane is substantiated. The procedure for the preparation of a catalytic membrane includes two stages: the initial formation of functional layers from a catalyst precursor followed by its activation. Changes in pore structure characteristics at different stages of preparation are exemplified by membranes with catalysts based on molybdenum compounds. The composite membrane structure has been formed from a precursor by chemical vapor deposition. Composite membranes based on a molybdenum carbide catalyst have been prepared using porous base layers with different porous structures. The effect of the stage of activation on the pore structure characteristics of a catalytic composite membrane has been experimentally demonstrated.
Keywords: catalytic membranes; porous structure; bulk catalyst; supported catalyst; catalyst precursor; catalyst activation; carburization; molybdenum carbide

Membrane emulsification in extraction processes by S. A. Sedysheva; L. E. Kopylova; A. A. Svittsov (847-861).
The application of the membrane emulsification (ME) method for extraction of poor target component from multicomponent solutions is analyzed in this review. The principle of ME and the mathematical model for estimation of droplets of the medium size are described. The ceramics is proposed as an optimal material of membrane for the extraction process, it allows one to solve the problem of interaction of membrane with solvents used as an extractants. The methods to supply with the required size and polydispersity of droplets for different types of membranes are considered. The results of investigation of ME processes for different extractants are shown. The different ways of demulsification are described. The separation scheme of the stable poor emulsions, consisting of stages of coalescence and membrane separation, is proposed.
Keywords: membrane emulsification; shear stress; extraction of poor compounds; selective extractant; emulsion droplet size; separation of emulsion; demulsification

Methods for synthesis of MF-4SC composite membranes exhibiting an anisotropic distribution of hydrated zirconia through the thickness have been proposed. The transport and diffusion characteristics of the resulting materials have been studied. It has been shown that the composite membranes with the anisotropic distribution of ZrO2 exhibit ion transport asymmetry.

Current–voltage characteristics and electric breakdown of metal-coated track-etched membranes by S. N. Podoynitsyn; T. V. Tsyganova; B. V. Mchedlishvili (866-870).
Current–voltage characteristics and electric breakdown of metal-coated track-etched membranes has been investigated. Features of current flow through a dielectric membrane that are associated with the presence of field-emission nanostructures have been revealed. The results of the study can be of interest in tackling the engineering problems of fabrication of field-emission nanostructures based on metallized track-etched membranes.
Keywords: track-etched membranes; metal coating; field-emission nanostructures; current–voltage characteristic; electrical breakdown

Principles of utilization of reverse osmosis concentrate at water treatment facilities by A. G. Pervov; A. P. Andrianov; E. B. Yurchevskiy (871-878).
It has been revealed that the use of reverse-osmosis (RO) membrane units for water treatment is complicated by the buildup of their concentrate waste needed to be disposed. A technology for recycling the concentrate, consisting of the removal (crystallization) of calcium carbonate present in the concentrate by seed crystals, has been proposed and experimentally tested. By this process using RO units, it is possible to obtain from natural water highly desalinated (softened) water and water with reduced concentrations of calcium and bicarbonate ions having the same salinity as the source water. The technology can be effectively used in the production of drinking water and integrated treatment of feed water for steam boilers and heat supply systems.
Keywords: reverse osmosis; water softening; desalination; seed crystals; water concentrating; water for steam generation; boiler feed water

Membrane technologies in the solution of environmental problems by A. G. Pervov; A. P. Andrianov; T. P. Gorbunova; A. S. Bagdasaryan (879-886).
The currently available reverse osmosis, nanofiltration, and ultrafiltration membrane technologies can be used in the solution of different problems related to the treatment of strongly polluted waters of different origin and the reuse of effluents. Nevertheless, experience in the operation of membrane facilities shows the existence of specific problems due to membrane fouling and measures for its averting. As a result of the extensive studies of the mechanisms of scaling, a new approach was proposed to decrease the fouling of membranes, which consists in the improvement of the construction of a membrane channel and in the selection of membrane characteristics. The developed design of open-channel spiral-wound modules makes it possible to exploit membrane units almost without the danger of scaling and to create new effective water treatment technologies on this basis. Long-term studies and pilot tests made it possible to develop a procedure for the optimization of membrane unit operations with minimum expenditures on electric power, maintenance, and effluent discharge.

Synthesis, ion exchange, and transport properties of membranes based on sulfonated polycarbonatemethacrylate by S. S. Novikov; S. E. Belova; A. U. Sanderov; A. B. Yaroslavtsev (887-891).
Products with ion-exchange properties have been obtained by heterogeneous sulfonation of polycarbonatemethacrylate (PCM). The resulting polymer and membranes based on it have been studied by means of elemental analysis, titrimetry, and IR spectroscopy. It has been shown that the ion-exchange capacity of the resulting products is 6 mEq/g. Therefore, together with relatively high ionic conductivity and ionexchange capacity, the products hold promise for use as ion-exchange membranes and modified coatings with ion-exchange properties.
Keywords: membranes; ion-exchange polymers; ion exchangers; sulfon

Potentiometric sensors with plastized poly(vinyl chloride) membranes selective to penicillin antibiotics: Properties and applications by E. G. Kulapina; N. M. Makarova; O. I. Kulapina; I. A. Utc; V. V. Baraguzina (892-900).
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection.
Keywords: plasticized poly(vinyl chloride) membranes; potentiometric sensors; penicillins; permeability; ion flux; drugs; biological fluids

Carbon monoxide oxidation over microfiltration ceramic membranes by E. F. Krivoshapkina; A. A. Vedyagin; P. V. Krivoshapkin; I. V. Desyatykh (901-908).
Characteristics of the porous permeable ceramics obtained from natural sources of Komi Republic have been studied. The method of surface self-propagating high-temperature synthesis has been adapted to form a catalytically active layer on the surface of a porous ceramic support. It has been shown that high activity of the synthesized CuO–Co3O4–CeO2/kaolin and CuO–Co3O4–CeO2/cordierite catalytic membranes is due to even distribution of highly dispersed active components both on the surface and in the bulk of microfiltration ceramics.
Keywords: microfiltration ceramic membranes; cordierite; kaolinite; surface self-propagating high-temperature synthesis; oxide systems; carbon monoxide oxidation

Samples of PA-100 ultrafiltration membrane of the Mifil brand have been scanned with an AISTNT SmartSPM-1000 atomic force microscope, and the images have been processed using the program Gwyddion. The pore size distribution data have been subjected to statistical processing and interpretation. The fitting curves of distribution are proposed, with their accuracy having been estimated using the Pearson and Kolmogorov goodness-of-fit criteria. Good agreement of the results with the data obtained by a modified fluid squeezing method has been achieved. It has been shown that the pattern of the distribution curve remains the same for different parts of the membrane.
Keywords: pore size distribution; ultrafiltration membrane; atomic force microscopy

Determining role of hydrogen bonding in electrically driven membrane transport: Quantum-chemical and molecular dynamics study by E. V. Butyrskaya; L. S. Nechaeva; V. A. Shaposhnikov; V. F. Selemenev (918-926).
By quantum chemistry and molecular dynamics analysis of the structure and chemical bond energy of the hydrated ion pair in a sulfonated cation exchange membrane, hydrogen bonding has been shown to play the determining role in electrically driven membrane transport in systems of this kind. The characteristics of hydrogen bridges linking hydrate water molecules in the sulfonated cation exchange membrane have been studied using the molecular dynamics method.

Electrochemically active surface of nanodispersed copper in ion-exchange matrix by E. V. Bulavina; M. Yu. Chayka; A. S. Solyanikova; T. A. Kravchenko (927-931).
Copper nanoparticles have been formed in ion exchange matrices KU-23 and MK-40 by chemical deposition. The size of the metal particles has been determined using scanning electron microscopy, X-ray powder analysis, and transmission electron microscopy. It has been found that the major contribution to the electrochemically active surface of the nanocomposite based on granular ion-exchange carrier make copper particles of a size of 37–47 nm regularly distributed on the bulk of the polymer. In electrode materials based on ion exchange membranes MK-40, copper nanoparticles on the surface are in general electrochemically active.

Dry reforming of methane in contactor and distributor membrane reactors by T. V. Bucharkina; N. N. Gavrilova; A. S. Kryzhanovskiy; V. V. Skudin; D. A. Shulmin (932-939).
Despite the well-known benefits of catalytic membrane reactors, they are still far from industrial implementation. Researchers who work in this area traditionally use catalytic membrane extractor reactors, which require the application of the most difficult to made catalytic membranes. Catalytic contactor and distributor membrane reactors are as yet imperfectly explored, although they have advantages over extractor reactors in many characteristics. This study is an attempt to fill, at least partially, the gap in understanding of the catalytic membrane process. On the assumption that a membrane-supported catalyst is a type of heterogeneous catalysts, the parameters of methane dry reforming in three catalytic reactors: a catalytic fixed-bed reactor, a contactor membrane reactor, and a distributor membrane reactor have been compared in terms of the classical kinetic method. The investigation has been carried out using the same catalytic system having tungsten carbide as the active component. It has been found that membrane reactors afford higher performance characteristics in the process of the dry reforming of methane, which occurs at high temperatures.
Keywords: membrane catalysis; catalytic membrane; contactor reactor; distributor reactor; extractor reactor; dry reforming of methane