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A thermodynamic analysis into the processes of slag accumulation during interaction of lead and lead-bismuth coolants with gaseous oxidants was carried out. It is shown that the oxidation of lead-containing coolants will lead to the formation of lead oxide, while the formation of bismuth oxide is unlikely. The possibility of selective oxidation of iron, chromium, and nickel to their oxides without the formation of slag from solid lead oxide with a dosed supply of a gaseous oxidizer to lead-containing coolants has been determined by calculation. It was revealed that the formation of solid lead oxide is unlikely when water vapor acts on lead-containing coolants. The calculation showed that it is necessary to extract the formed hydrogen from water vapor to a ratio of 1 : 20 000 or less in order to create conditions for the formation of solid lead oxide. The regularities of the formation of lead oxide during depressurization of a circuit with a lead-containing coolant and their interaction with atmospheric oxygen have been investigated. According to the results of the experiment, the largest amount of solid PbO is formed upon contact with oxygen in a circuit not filled with a coolant and cooled to ambient temperature. Short-term depressurization of the loop in the hot state led to the formation of a smaller mass of PbO, and the presence or absence of a coolant in the loop had an insignificant effect on the mass of the PbO formed. The possibility for the formation of solid PbO during a microleak of a steam generator in the TT-2M stand with a Pb–Bi coolant has been investigated. Under the experimental conditions, it was not possible to obtain solid lead oxide, and the achieved limiting content of dissolved lead oxide turned out to be 550 times less than the saturation concentration.

The modification of polyvinyltrimethylsilane under treatment by direct-current discharge at a reduced pressure has been investigated. Polymer films were placed at the anode and cathode, and filtered atmospheric air was used as a process gas. It has been found that the discharge treatment imparts the property of hydrophilicity to the surface of the samples. The chemical composition of the untreated and modified films was investigated by X-ray photoelectron spectroscopy, and their morphology was studied by atomic force microscopy. It has been shown that plasma treatment leads to the formation of a layer chemically close to silicon dioxide on the surface and increases the roughness of the surface of polyvinyltrimethylsilane.

The reactions of boric acid and 4-fluorophenylboronic acid with H- and Cl-terminated Si(100) surfaces in solution were investigated. X-ray photoelectron spectroscopy (XPS) studies reveal that both molecules react preferentially with Cl-Si(100) and not with H-Si(100) at identical conditions. On Cl-Si(100), the reactions introduce boron onto the surface, forming a Si-O-B structure. The quantification of boron surface coverage demonstrates that the 4-fluorophenylboronic acid leads to ∼2.8 times higher boron coverage compared to that of boric acid on Cl-Si(100). Consistent with these observations, density functional theory studies show that the reaction of boric acid and 4-fluorophenylboronic acid is more favorable with the Cl- versus H-terminated surface and that on Cl-Si(100) the reaction with 4-fluorophenylboronic acid is ∼55.3 kJ/mol more thermodynamically favorable than the reaction with boric acid. The computational studies were also used to demonstrate the propensity of the overall approach to form high-coverage monolayers on these surfaces, with implications for selective-area boron-based monolayer doping.

Controlling thickness and morphology of transition-metal thin films used in magnetic random-access memory fabrication is a major challenge. Thermal dry etching has emerged as a method of choice for...

The paper presents the results of applying the membrane gas separation technique to the recovery of CO2 and its subsequent utilization by converting into ammonium carbamate. One-sided surface modification of homogeneous polyvinyltrimethylsilane (PVTMS) films by treating in low-temperature air plasma for 30 and 60 s has been carried out. The transport and gas separation properties of the modified samples has been investigated, and values for the permeability and diffusion coefficients of CO2, N2, and CH4 have been experimentally obtained. On the basis of the experimental data, the effective coefficients of gas solubility in the modified film have been determined. It has been found that by modification within 30 s, the CO2/N2 and CO2/CH4 separation factors are increased by two and three times, respectively, relative to the initial values. To assess the possibility of using the new membranes, mathematical modeling of a single-step membrane process for the separation of biogas components under steady-state and non-steady-state has been carried out. It has been shown that the proposed membrane modification method makes it possible to significantly increase the performance of the membrane unit: for example, the recovery of CH4 under steady-state conditions is increased from 70 to 86%, and the CO2 content in the permeate increases from 68 to 82 mol %. The reaction of ammonium carbamate production from CO2 and ammonia in recycled vegetable oil as a solvent has been successfully conducted using the calculated characteristics of the membrane module based on modified PVTMS.

Carbon sequestration and utilization are currently gaining attention as they help to reduce the emission of greenhouse gases in the atmosphere. This study explores the possibility of using carbon dioxide as a feedstock for the production of ammonium carbamate, a precursor molecule for urea production. Waste cooking oil was used as the indispensable nonaqueous medium for the formation of pure ammonium carbamate. This makes the process completely ecofriendly and cost‐effective. A continuous process of ammonium carbamate production at 20°C results in 88.86% consumption of carbon dioxide. The highest yield of ammonium carbamate was achieved at an NH3/CO2 ratio of 2.5. A three‐stage setup was also found to increase the yield of ammonium carbamate. The reusability of oil after each cycle was checked and it was found that the formation of the product is comparatively less compared to the previous cycle. Lower yield was observed when the same experiment was carried out with fresh oil (sunflower oil). The exit gas from the process was found to be rich in ammonia that can be further used for the production of struvite, a phosphate fertilizer. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

This work considers new possibilities for the use of membrane gas separation technology for target control of the composition of synthesis gas. For this purpose, we propose using highly permeable modified disubstituted polyacetylenes with an improved combination of selectivity of separation of hydrogen, carbon monoxide, and carbon dioxide and a high level of transfer of hydrogen as the main component of synthesis gas. This work presents the description of the modification of polymers and key properties of membrane materials. The process of membrane separation of synthesis gas is modeled using both commercially available membranes and new laboratory membranes. The possibility of creating a combined membrane system providing the preparation of synthesis gas with a wide range of H2 : CO ratios (from 0.5 to 4) and a low residual concentration of CO2 (5 vol %) from biosyngas with the composition H2 (40 vol %)/CO (25 vol %)/CO2 (35 vol %) is also shown.

The paper presents the new data of gas transfer characteristics of semicrystalline poly(4-methyl-1-pentene) (PMP) as for films as for hollow fibers (HFs) with dense selective layer. The experimental data obtained earlier made it possible to calculate the gas transport characteristics of the amorphous and crystalline phases of PMP for some gases at temperature from 10 to 80 °C (below and above Tg). On the basis of these data and using the correlation approach, an assessment of the expected gas transport characteristics of HFs based on PMP was carried out in this work for helium and lower hydrocarbons, as well as for water vapors. It is shown that crystalline phase is very permeable and higher crystallinity degree leads to the increasing of PMP selectivity. Laboratory-scale membrane module with commercial hollow fibers of PMP was prepared and successfully tested by the differential method of gas permeability. Application of crazing method which should increase the crystallinity degree of PMP seems promising for the production of perspective HFs with improved transport and separation performance compared with the existing ones.

Platinum-based supported catalysts for hydrocarbon conversion are among the most effective for selective dehydrogenation and isomerization processes. However, high process temperatures and the poss...

The thermal chemistry of several metal organic compounds with amidinate, diketonate, or cyclopentadienyl (Cp) ligands on oxide surfaces, mainly on silicon dioxide but also on aluminum oxide, was st...

A “green” method to synthesize new composite membranes from a cellulose solution in phosphoric acid on various ultrafiltration substrates is proposed. The method can be used in industry; it differs from the conventional viscose method for producing cellophane and other known methods for synthesizing cellulose-based gas separation membranes by the absence of gaseous emissions and wastewater. The structure of the synthesized samples is studied by electron microscopy, X-ray diffraction, and thermal analysis (DSC). Analysis of the mechanical properties of the samples shows that the new membranes have better mechanical characteristics than those of homogeneous pure cellulose films synthesized in this study and commercial cellophane films. The gas transport properties of new membranes with respect to O2, N2, CO2, CH4, and He are studied. It is found that the proposed membrane synthesis method provides the formation of uniform dense gas separation layers of cellulose; the membranes show a three orders of magnitude higher gas permeability than that of cellophane films. It is shown that the highest ideal selectivity is exhibited by membranes with a gas separation layer of cellulose on viscose fabric substrates.

The specifics of diffusion of water and methanol vapors in nonporous polymer films based on polyvinyltrimethylsilane (PVTMS) have been studied. The vapor diffusion coefficients have been determined by measuring the kinetics of unsteady flow through the membrane (differential method) and subsequent processing the results by functional scaling . The kinetic curves have been found to deviate from those described by classical Fick’s law. It has been theoretically shown that such deviations can be due to the formation of associates of penetrant molecules inside the membrane, and a modified method for calculating diffusion coefficients has been proposed for this case. The behavior of the diffusion coefficients of water and methanol vapors in PVTMS in the temperature range of 50–90°C and the vapor activity range of 0.3–0.9 has been studied. The activation energies of diffusion of water and methanol vapors in PVTMS have been determined to be 23 and 44 kJ/mol, respectively, and the effective kinetic diameters of the molecules have been calculated to be 0.29 and 0.37 nm, respectively. The proposed approach opens the possibility for systematic studies of the diffusion kinetics of vapors of different organic compounds with an assessment of their kinetic contribution to the membrane permselectivity.

This study examines the fundamental and practical aspects of C1-C4 hydrocarbons separation (pure or in binary or ternary mixtures), using highly permeable glassy 1,2-disubstituted polyacetylenes. Poly(4-methyl-2-pentyne) (PMP) was chosen as the main object of study. An attempt is made here to carry out a systematic comparative study of the PMP permeability target parameters using correlation detection and a thermodynamic gas/polymer model. A non-isothermal application method was used, which allowed us to work with each gas individually and with various mixtures to obtain an experimental value for the dependence on temperature of the permeability of C1, C3, C4 hydrocarbons. This is the first time that this method has been used for the study of glassy polymers with high free volume. An interesting phenomenon of an increase in non-additive separation selectivity α was shown (for a value of α of between ∼10 and ∼8000 units) with increase of butane activity (p/psat) from 0.02 to 0.94 in the feed gas mixture. In the current study, an explanation is given for the increase in non-additive selectivity for PMP membrane separation. Modelling was carried out of the separation process of a binary butane/methane mixture using this non-additive phenomenon, which gives rise to concentrated components.

The surface properties of metal-oxide nanomaterials (MONMs) can be tuned by reacting them with a variety of organic compounds. Reactions of the oxides with functionalized carboxylic (R–COOH) or phosphonic acids (R–PO(OH)2) and various approaches utilizing silylation (such as with R–Si(X)3, where the X could be Cl or −OCH3) are often used to deliver the target modifier R to the oxide surface. However, the liquid-phase reactions between metal oxides and these agents often cause agglomeration or multilayer growth, morphology change, or surface etching. In this paper, we report a novel approach that circumvents all of these problems. The proposed two-step functionalization approach utilizes exposure of the oxide materials to prop-2-ynoic acid (HC≡C–COOH, propiolic acid) in the gas phase as a first step. The second step can then utilize the created C≡C for post-modification that introduces any predesigned functionality to the surface via “click” chemistry with azides (R–N3). Gas-phase exposure of prop-2-ynoic ...

A «green» method of obtaining gas separation composite membranes from cellulose solutions and its mixtures with chitosan in orthophosphoric acid is proposed for industrial use, and differs from the viscose method of producing cellophane and other known methods for producing cellulose gas separation membranes without gaseous emissions and wastewater. It is shown that new composite cellulose membranes on a viscose fabric substrate are characterized by high productivity and selectivity for O2/ N2 pairs, comparable to the values obtained for known membranes made of synthetic polymers, as well as increased mechanical strength. The developed composite membranes demonstrate an inverse selectivity for the CH4/CO2 pair, which is not typical for gas separation membranes described in the literature with cellulose-based selective layers.

The adsorption configurations of a technologically relevant model organic adsorbate on the silicon (001) surface were studied using energy scanned x-ray photoelectron diffraction (PhD). Previous work has established the existence of an interesting vertically-aligned (‘flagpole’) configuration, where the acetophenone attaches to Si(001) via the acetyl group carbon and oxygen atoms. Density functional theory calculations have predicted two energetically similar variants of this structure, where the phenyl ring is orientated parallel or perpendicular to the rows of silicon dimers on this reconstructed surface. However, previously published experimental measurements, including scanning tunnelling microscopy, x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure investigations were unable to distinguish between these two configurations. Here, we apply the unique experimental capabilities of the PhD technique to this system and demonstrate that the dominant adsorption configuration has the phenyl ring parallel to the dimer rows (the end-bridge structure). This information in turn facilitates the determination of the dominant reaction pathway for acetophenone on Si(001), which has remained elusive until now. Information about subtle preferences in reaction pathways that affect the alignment and orientation of organic adsorbates such as acetophenone on technologically-relevant semiconductor surfaces such as Si(001) is critical for the fabrication of future atomically-precise atomic and molecular-scale electronic devices utilising the organic-silicon interface, and this work demonstrates the unique and complementary capabilities of PhD for providing this information.

Recent advances in organic surface sensitization of metal oxide nanomaterials focused on two-step approaches with the first step providing a convenient functionalized chemical "hook", such as an alkyne functionality connected to a carboxylic group in prop-2-ynoic acid. The second step then took advantage of copper-catalyzed click chemistry to deliver the desired structure (such as benzyl or perylene) attached to an azide to react with the surface-bound alkyne. The use of this approach on CuO not only resulted in a successful morphology preserving chemical modification but also has demonstrated that surface Cu(I) can be obtained during the process and promote a surface-catalyzed click reaction without additional copper catalyst. Here, it is demonstrated that this surface-catalyzed chemistry can be performed on a surface of the CuO nanomaterial without a solvent, as a "dry click" reaction, as confirmed with spectroscopic and microscopic investigations with X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, solid-state nuclear magnetic resonance, and scanning electron microscopy. Computational studies provided instructive information on the interaction between the surface prop-2-yonate and azide functional group to better understand the mechanism of this surface-catalyzed click reaction.

The reactivity of liquid hydrazine (N2H4) with respect to H-, Cl-, and Br-terminated Si(100) surfaces was investigated to uncover the principles of nitrogen incorporation into the interface. This p...

The structure and gas transport properties of polymer membranes prepared from commercial Lavsan™ (polyethylene terephthalate based material) films by irradiation of the polymer films with Ar ions, followed by etching in an NaOH solution, were studied. Analysis of the polymer structure by differential scanning calorimetry showed that irradiation of the Lavsan™ matrix with Ar ions (energy 2.4 MeV nucleon−1, fluence 6 × 107 cm−2) led to a 20–30% decrease in the degree of crystallinity. The permeability of the new membranes to He, H2, O2, Ar, N2, CH4, CO2, and H2/CH4 mixture was evaluated. UV sensitization allows a fourfold increase in the permeability of the Lavsan™-based films to the gases tested relative to the films etched without preliminary UV irradiation. The composition of the H2/CH4 gas mixture does not influence the separating properties of the membranes, and the mixture separation factor coincides with the ideal value of the gas selectivity.

A three-stage process for the production of motor fuel (MT) components from lignocellulosic raw materials is described. In the first, pretreatment stage, lignocellulose is subjected to hydrolysis with cellulases followed by fermentation of the resulting sugars into ethanol; then, dilute ethanol solutions are concentrated by membrane vapor separation to obtain 70–80% solutions. At the third stage, aqueous ethanol solutions (water content 0–50%) in the presence of a Pd–Zn/Al2O3/MFI catalyst at 350°C and a space velocity of 0.6 h−1 are converted into alkanes, and С3–С8 olefins and С6–C12 aromatic compounds (MT components). It has been found that water in an amount of up to 30% in ethanol solutions effectively inhibits the detrimental hydrocarbon cracking and catalyst coking processes, thereby leading to a decrease in the formation of undesirable C1 and C2 products and an increase in the catalyst on-stream time to 100 h wherein the yield of the desired fraction is reduced only by 10–15%. The subsequent treatment of the catalyst surface with steam and hydrogen completely restores its catalytic activity.

Aim.To study the link of increased serum concentrations of osteoprotegerin (OPG) in patients with chronic heart failure (CHF) associated with type 2 diabetes mellitus (DM 2), osteoporosis or osteopenia with the development of cardiovascular events (primarily, decompensation of CHF, including those requiring hospitalization, death from cardiovascular disease, acute coronary syndrome or acute ischemic stroke) to determine the possibility of using this biomarker as a predictor of a severe course of cardiovascular disease in these patients.Materials and methods.In a 12-month cohort observational study included 75 patients (mean age 57.4 ± 5.4 years) with CHF associated with DM 2, osteoporosis or osteopenia. Cardiovascular events were analyzed in three groups of patients formed based terteling ranges of concentration of the OPG level in serum: in the 1st group (n= 25) included patients with serum OPG concentration is less than 5.0 pmol/l; in the 2nd group (n= 25) OPG level of 5.0–7.2 pmol/l; in the 3rd group (n= 25) - with the content of OPG more than 7.2 pmol/L. The serum OPG, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) serum levels were determined by ELISA. Assessment of bone mineral density (BMD) was performed by a densitometric method using dual-energy X-ray absorptiometry.Results.Highly reliable increased expression of OPG in 2 and 3th tertiles was found in patients with CHF associated with type 2 diabetes in comparison with the control group. The frequency of adverse events gradually increased from the 1st tertile to the 3rd tertile OPG. With the median for OPG more than 5.2 pmol/L and BMD less than -2.5 standard deviations, the highest frequency (60.9%) of adverse cardiovascular events was identified. A close correlation of OPG with the values of pro-inflammatory cytokines-TNF-α (r= 0.46;p= 0.019) and IL-1β (r= 0.4;p= 0.01), glycated hemoglobin (r= 0.55;p= 0.009) and the severity of CHF (r= 0.49;p= 0.013).Conclusions.Osteoprotegerin is an independent risk factor for the development of comorbid cardiovascular pathology: CHF associated with DM 2 and osteoporosis. It seems clinically justified to use OPG to stratify the risk of progression of cardiovascular pathology.

The paper presents the characteristics of a laboratory-made water-selective composite membrane with a selective layer of hydrophobic polyvinyltrimethylsilane (PVTMS) for use in the processes of vapor-phase membrane recovery of alcohols from dilute aqueous alcohol mixtures of biogenic origin. The support is a polyacrylonitrile ultrafiltration membrane, and the PVTMS skin layer of the resulting composite membrane has a thickness of 3 to 4 microns. The vapor transport and separation characteristics of the membrane for water–ethanol and water–butanol mixtures in the temperature range of 60–80°C have been studied. It has been shown that the membrane selectivity varies in the range of 23–39 for the water/ethanol pair or 100–140 for the water/butanol pair. A specific feature of the hydrophobic water-selective membrane as applied to the vapor-phase process is the stability of its characteristics due to the absence of swelling, in contrast to hydrophilic water-selective membranes whose characteristics substantially depend on the activity of water vapor. The process of vapor-phase membrane recovery of ethanol and butanol from dilute aqueous alcohol mixtures of biogenic origin with their initial concentrations of 10 and 1 wt %, respectively, has been mathematically modeled on the basis of the experimental data. The calculation results show that the composite membrane obtained makes it possible to concentrate ethanol and butanol to 95 and 98 wt % with degrees of recovery of more than 0.8 and more than 0.9, respectively.

The use of gas-phase electron-impact activation of metalorganic complexes to facilitate atomic layer depositions (ALD) was tested for the case of (methylcyclopentadienyl)Pt(IV) trimethyl (MeCpPtMe3) on silicon oxide films. Uptake enhancements of more than 1 order of magnitude were calculated from X-ray photoelectron spectroscopy (XPS) data. On the basis of the measured C:Pt ratios, the surface species were estimated to mainly consist of MeCpPt moieties, likely because of the prevalent formation of [MeCpPtMex–nH]+ ions after gas-phase ionization (as determined by mass spectrometry). Counterintuitively, more extensive adsorption was observed on thick SiO2 films than on the native thin SiO2 film that forms on Si(100) wafers, despite the former having virtually no surface OH groups. The adsorption of MeCpPt fragments on silicon oxide surfaces was determined by density functional theory (DFT) calculations to be highly exothermic and to favor attachment to Si–O–Si bridge sites.

High-throughput synthesis of a series of monometallic and bimetallic catalysts (45 bimetallic and 50 monometallic samples) consisting of nickel and one of nine different metal promoters (B, Co, Cu, Fe, Mg, Mn, Sn, V and Zn) supported on one of five different metal oxides (alumina, ceria, magnesia, silica and titania) is carried out via organometallic grafting using a robotic platform. The catalysts are evaluated for their activity and selectivity for the dry reforming of methane at a feed ratio of CH4:CO2 of 1 at 650–800 °C in a parallel flow reactor system. The type of oxide support prevails over the type of additive for both catalyst activity and stability. On Al2O3 and MgO, Fe was found to be the best promoter; on SiO2, Cu is the best promoter at 700 °C and higher, while on TiO2, Mn is found to enhance the conversion at 800 °C. On CeO2, all additives except Fe have beneficial effects. Twenty-five catalysts show > 90% methane conversion with ten catalysts showing > 95% conversion at 800 °C with the H2:CO ratios ranging from 0.8 to 1.2. Amongst the ten highest performers, NiFe/Al2O3 and NiFe/MgO are more active than Ni/Al2O3 and Ni/MgO, respectively and were stable over a period of 25 h at 800 °C. Characterization on the as-prepared samples reveals highly dispersed phase, while after reduction in H2, highly dispersed and reduced nickel particles up to 10 nm are formed. The particles do not increase in size under dry reforming reaction conditions at 800 °C. An increased hydrogen consumption observed during H2-TPR of the nickel particles is positively correlated with methane conversion for Al2O3-based catalysts. The resistance to deactivation by coking and variation in coke structure are investigated by spectroscopic and microscopic methods to identify the relationship between metal promoters, alloy formation, and type of surface carbon deposits. Carbon whiskers were observed on the ten selected spent samples and are preferentially deposited on Ni rather than on the promoters. Carbon nanotube formation and metal particle removal from support were not observed to cause deactivation while amorphous carbon formation was clearly linked to catalyst deactivation, as amorphous carbon could encapsulate Ni, either on the support or at the end of the carbon nanotube. The organometallic grafting technique is an efficient and suitable technique for synthesizing highly dispersed and homogeneous phases which lead to high conversion and high durability for dry reforming of methane.

This paper presents the results of a study of the gas transfer and selective properties of PMP hollow fibres (HFs) produced by melt spinning technology. The HFs are characterized by WAXD, SEM and DSC methods. Transport and separation properties have been determined in relation to N2, CO2, methane, butane and different mixtures in the temperature range from −10 to 80 °C. It has been shown that the permeance of methane in mixture with N2 and CO2 is similar to the pure methane transport, whereas the presence of butane changes PMP properties and influence transport of methane. An increase in the activity of butane in a mixture with methane led to a significant increase in the permeation flux of both butane and methane through the walls of the HFs. It was shown that PMP changes properties from methane-selective at low butane activities to butane -selective at higher butane activities. The changing of butane and methane permeance in a mixture was found well described by an exponential dependence on the activity of butane. The values of permeance parameters were determined by different methods and found to be in good agreement between each other. Discovered effect for methane/butane mixture transfer in PMP HFs allows to perform the simulation of hydrocarbons separation taking into account changing of membrane properties and discovering of promising areas and conditions of practical application for the new PMP HFs.

A novel approach to the evaluation of the C 1 –C 4 hydrocarbon (pure and mixed-gas) permeability parameters in the thin film composite membranes with rubbery or glassy-like selective layers is presented. The permeability measurements are performed for the C 1 –C 4 hydrocarbons on the commercially available membranes MDK (based on polydimethylsiloxane (PDMS)) at the temperature range of −20° up to +40 °C under linear heating. The values of the gas permeability coefficients P and the apparent activation energy E P were measured during same experiment. The solubility data ( S and ΔH S ) were calculated using the Pierotti’s statistical-thermodynamic model. The diffusion coefficients were calculated indirectly using the permeability and solubility data assuming the solution-diffusion model for permeation. The equal data sets were obtained for the polyisoprene membranes and the polyvyniltrimethylsilane ones. It is concluded that the ideal C 1 –C 4 -hydrocarbon separation selectivity is controlled by the kinetic component (selectivity of diffusion). The article also describes the permeability increase of propane, butane (pure and in mixtures) under the temperature pull down in the PDMS (being consistent with the lower activation diffusion energy E D of those hydrocarbons in the typical rubber-like polymeric matrix which is a thin selective layer). The results of this study will be useful in understanding of the fundamental aspects of the membrane C 1 –C 4 separation phenomena, and for the fast separation parameters evaluation of the lower hydrocarbon mixtures using the polymeric membranes as well.

Chemical functionalization of ZnO surface with an alkyne functional group was successfully achieved by exposing ZnO nanopowder to gas-phase propiolic acid in vacuum, which left the alkyne group available for subsequent chemical modification via the azide-alkyne cycloaddition "click" reaction with benzyl azide. The highly selective formation of a bidentate carboxylate linkage and the reaction of benzyl azide were confirmed by solid-state nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Most importantly, scanning electron microscopy revealed that the surface morphology was perfectly preserved by this gas-phase modification, as opposed to the alternative protocols based on liquid phase processing. This simple and precise design can serve as a universal method for the modular functionalization of zinc oxide surface following the initial surface preparation and be further applied to thin films, nanostructures, and powders, where preserving surface morphology during chemical modification is especially important.

The differences between the dissociative adsorption of chloroethane-d5 (C2D5Cl) and iodoethane-d5 (C2D5I) on a Si(100)-2 × 1 surface are compared by analyzing the results of density functional theory (DFT) calculations and temperature-programmed desorption (TPD) experiments. The adsorption mechanism for both chloroethane-d5 and iodoethane-d5 on a clean Si(100)-2 × 1 surface is based on a dissociative chemisorption following halogen–carbon bond cleavage. Further surface transformations upon heating cause hydrogen elimination by ethyl groups, followed by ethylene and hydrogen desorption. The key difference between iodo- and chloro-derivatives is that the corresponding sticking probabilities of chloroethane-d5 and iodoethane-d5 in the same reaction system are extremely different. The experimental study reveals that the exposure for the monolayer saturation of chloroethane-d5 is 20 times higher than that for iodoethane-d5. These differences are attributed to the stability of surface-mediated molecular adsorba...

The development of oxygen-free organic–inorganic interfaces has led to new schemes for the functionalization of silicon surfaces with nitrogen-based chemical groups. However, building layers of large structures directly on this functionalized surface has remained elusive. This work confirms the path to form a stable interface between silicon and buckminsterfullerene C60 based on covalent chemical bonds. The starting point for this modification is the hydrazine-reacted Si(111) surface with the diamine functionality, which is further reacted directly with the C60 molecules. The chemistry of this process is confirmed spectroscopically and microscopically and can be used to form organic–inorganic interfaces separated by a single layer of nitrogen.

Leaching of polymetallic sulfides is often challenging due to the complexity of these systems. The main issues are related to the formation of surface by-products or to the presence of different metals that require a greater consumption of chemicals compared to that needed to extract the target metal during leaching. This latter case is followed in the present work using X-ray photoelectron spectroscopy (XPS) during the leaching of a silver-containing polymetallic (Mn-Fe-Pb) sulfide under three different cyanidation procedures: (1) conventional leaching, (2) ultrasound-assisted leaching, and (3) leaching of a sample pretreated in alkaline media. In all cases, leaching results in the build-up of Pb compounds (oxides/hydroxides) on the surface of the minerals, suggesting a mechanism in which Pb is first leached by hydroxide and cyanide and later is re-adsorbed as an external layer on the minerals. On the other hand, the effect of each process on Mn was quite distinct: 1) Conventional leaching leads to the oxidation of the sulfide (pyrite) surface and a slight increase of surface Mn species; 2) Ultrasound-assisted leaching decreases surface Mn by dissolving oxidized species, which exposes fresh sulfide surfaces and increases Ag extraction; and 3) An alkaline pretreatment at high temperature exposed fresh sulfide surfaces and decreased the surface concentration of Mn. The fact that ultrasound-assisted leaching and leaching after an alkaline pretreatment allow for a higher Ag extraction (60% and 75% of total Ag, respectively, as opposed to the 25% extracted via conventional leaching), indicates that leaching is more efficient if the surface is not oxidized and if Mn is removed from the samples, either before or during leaching.

This study investigates the adsorption and thermal transformations of a bicyclic tertiary amine, triethylenediamine, on the clean Si(100)-2 × 1 surface. Below room temperature, triethylenediamine adsorption leads to the formation of a strong dative bond between one of the nitrogen atoms of this compound and the silicon surface. In contrast to previously studied amines, the datively adsorbed triethylenediamine features a second tertiary amine entity that is not bonded to the surface, with a lone pair orbital that is directed away from the surface and is available for further reactions. The thermal chemistry and electronic properties of triethylenediamine on silicon are studied using thermal desorption spectroscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. Near-edge X-ray absorption fine structure measurements are utilized to clarify the geometry of the adsorbates at room temperature. Density functional theory calculations are used to describe the binding geometry and electronic properti...

Pervaporation and vapor-phase membrane separation methods for the recovery of bioalcohols from dilute aqueous solutions have been critically compared. The importance of taking into account the liquid–vapor equilibrium diagram in studies on the separation of binary aqueous–alcoholic liquid media by these methods has been shown. Previously published experimental data on the transport of water, ethanol, and n-butanol vapors in hydrophobic membranes based on the glassy polymers poly(vinyltrimethylsilane) (PVTMS), poly(1-trimethylsilyl-1-propyne) (PTMSP), and poly(4-methyl-1-pentyne) (PMP) have been analyzed. Schemes of butanol and ethanol recovery by the vapor-phase membrane separation process from fermentation broths for the cases of application of water-selective and alcohol-selective membranes have been presented, as well as the results of mathematical simulation of the process and assessment of energy consumption.

Aim. To study the influence of polymorphism of the gene methyltetrahydrofolate-reductase (MTHFR) — polymorhic locus С 677 Т , and level of homocysteine in blood plasma on the risk of development and course of chronic heart failure (CHF). Material and methods. Totally, 277 persons studied with CHF II-IV functional classes (FC NYHA). The polymorphism С 677 Т of gene MTHFR studied via polymerase chain reaction. With the aim to reveal association of homocysteine with the course of CHF patients were selected by the results of year-long observation to 2 groups: with benign (n=49) and adverse (n=45) course. During the period the following was assessed: increase of symptoms and severity of CHF, hospitalizations rate, dynamics of the left ventricle ejection fraction. Results. Carriage of allele T and genotype T/T of polymorphic locus С 677 Т gene MTHFR was associated with more severe clinical picture of CHF. In CHF patients of II-IV FC homocysteine concentration in serum was significantly, 2-3 times, higher comparing to the controls, regardless of age. In adverse course group the level was highest comparing to benign course. Conclusion. The relation revealed of hyperhomocysteinemia with severity and character of CHF course. Assessment of homocysteine level in serum, and genetic polymorphism С 677 Т of gene MTHFR can be recommended for earlier prediction of severity of CHF.

The presented nonisothermal technique for investigation of membrane gas separation (using MDK-1 membrane as an example) demonstrates possibilities of rapid assessment of the separation power of commercial membranes for both individual components and various mixtures in the temperature range of‒20 to +40°C. The efficiency of the membrane process under these conditions (cross-flow membrane module model) for separation of propane–methane mixtures has been evaluated. It has been shown that the permeability of methane decreases with a decrease in temperature in the Arrhenius coordinates and the propane permeability increases. The separation selectivity in the mixture decreases by more than twofold in comparison with the ideal selectivity. Nevertheless, a significant improvement of separation has been observed at lower temperatures, with the recovery of the desired product and its purity being variable in a wide range depending on the practical goal. The nonisothermal technique is supposed to be useful for rapid selection of conditions (temperature, pressure, components to be separated) for efficient application of polymeric membranes for separation of hydrocarbon-containing mixtures that are close in composition to real gas sources.

Journal of applied polymer science e49630 (2020). doi:10.1002/app.49630, Published by Wiley, New York, NY [u.a.]

Lignocellulose pretreated with dilute alkali and hydrolysed with cellulases was used as substrate for the processing of acetone–butanol–ethanol (ABE) clostridial fermentation followed by the vapour-phase membrane concentration of two alcohols and acetone with up to 99% degree of recovery. ABE concentrate was used for the catalytic synthesis of fuel components over a zeolite catalyst with aliphatic and aromatic hydrocarbons as the main products with up to 60% conversion. The zeolite catalyst was effectively regenerated from coking by hot steam treatment with up to 100% recovery in catalytic activity. The main novelties of the process are in demonstration the effectiveness of vapor-phase ABE concentration, its effective conversion to hydrocarbons followed by of catalyst’ regeneration. The process described paves the way to developing renewable technologies for the production of motor fuel components.

Transport parameters of gases and light hydrocarbons in polymeric membrane materials including their temperature and pressure dependencies are very important to know for estimation of perspective applications and optimal operating conditions of membranes and membrane modules in gas separation processes. Today, transport parameters of gases for more than 2000 polymers and copolymers have been accumulated systematically. Unfortunately, in most of cases only gas permeability coefficients under isothermal conditions have been measured. Studies where the measurements of gas diffusion and solubility coefficients were also carried out are presented to a far lesser extent. The parameters of temperature dependencies of gas transfer (EP, ED, and ΔHS) are mentioned even more rarely. Nevertheless these values are undoubtedly necessary for fundamental knowledge, possibility of membrane gas transport properties prediction for a wide range of gases, understanding of complex and unusual mass transfer effects, and studying and modeling of kinetic (unsteady state) separation processes. This work represents various methods (integral, differential, pulse, and concentration waves) of experimental determination of diffusion coefficient and corresponding mathematical background with examples of application of the experimental data treatment techniques (singular points, functional scale, and statistical moments). Most of methods are known but are either scattered in the literature on various diffusion phenomena or used very narrowly. In the present work, using the “classical” diffusion model of the permeability method, i.e. assuming that the mechanism of nonstationary gas permeability through the polymer membrane is subject to Fick's diffusion laws and Henry's law, the main difficulties in calculating membrane gas transfer parameters, including detection inertia, are considered. Considered approaches are illustrated by examples of theoretical and experimental kinetic curves of diffusion of carbon dioxide, methane, and a number of inert gases (including radon) in such polymers as rubber-like (polydimethylsiloxane, PDMS), glassy (polyvinyltrimethylsilane, PVTMS) and semicrystalline (poly-4-methylpentene-1, PMP; low-density polyethylene, LDPE) ones, as well as in two-phase block copolymers PVTMS/PDMS with different ratios of components.

The reaction of metal-free phthalocyanine molecules with a chlorine-terminated Si(111) surface is investigated to produce a phthalocyanine functionality directly attached to a semiconductor surface, without additional linkers or layers. The carefully prepared Cl–Si(111) surface provides an oxygen-free substrate that is reacted with 29,31-H phthalocyanine (H2Pc) in a wet-chemistry process resulting in HCl elimination. The in situ metalation of this H2Pc-modified silicon surface with cobalt is confirmed, suggesting that the produced functionality is chemically active. These processes are investigated by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry supplemented by density functional theory calculations. The morphology of the surface is monitored by atomic force microscopy. The combined spectroscopic, microscopic, and theoretical investigations demonstrate that additional linkers are not required for phthalocyanine attachment to ...

Aim . To study the interrelation between hyperhomocysteinemia, the expression of endothelin-1, Fas-ligand (Fas-L), atrial natriuretic peptide (NT-proBNP) and the severity and course of chronic heart failure (CHF) in patients with coronary heart disease (CHD) during the 12-month prospective study to develop forecasting models of the probability of adverse cardiovascular events depending on gender. Materials and methods. The study included 94 patients with CHF. The control group included 32 people who did not have cardiovascular disorders. At baseline and after 12 months of observation in the blood serum levels of sFas-L, homocysteine, endothelin-1 and NT-proBNP were measured by enzyme-linked immunosorbent solid phase assay. Results . It is established that predictors of adverse cardiovascular events in men with coronary artery disease are elevated serum levels of homocysteine, the increased expression of NT-proBNP, platelet-derived growth factor AB (PDGF-AB) associated with the size of the left atrium and hypertriglyceridemia when in women are hyperhomocysteinemia with increased expression of NTproBNP, and TNF-α, as well as the enlarged size of the left atrium and hypercreatininemia. The most informative indicators of prognosis of cardiovascular complications in patients with CHF are homocysteinemia and the level of NT-proBNP. Conclusion . It is established that there is the interrelation between hyperhomocysteinemia, elevated levels of endothelin-1, Fas-L and NT-proBNP in the blood serum with the severity and course of CHF in patients with coronary artery disease. Proposed individual values of the integral index of the probability of occurrence of adverse cardiovascular events for men and women that provides the innovative approach to personalize preventive treatment of these patients.

Evaluation of several versions of phenomenological theory of gas permeability in selective polymeric membranes is presented, along with the appropriate experimental methods for verification of these versions. The main focus is on a description of stationary mass transfer across membranes (films) containing dispersion inclusions of various shapes of one polymer in a matrix of another. Considering heterogeneous media as a membrane material, it was assumed that diffusion and sorption properties of inclusions are different from those of the dispersing medium. The problem of choosing optimal shape of inclusions is evaluated from the point of view of targeted permeability and selectivity of a membrane with respect to gases. To confirm this theoretical approach, the experimental results of the studies of diffusion (permeability) of permanent gases in polymeric membranes of different structures were used. The target gases included noble gases, hydrogen, nitrogen, oxygen, CO 2 , and methane. The target polymers included glassy polyvinyltrimethylsilane (PVTMS, T gl = 155–180 °C), rubberlike polydimethylsiloxane (PDMS, T gl = −120 °C), and two-phase block-copolymers based on these materials within a wide range of composition, including the region of phase inversion. In addition, available experimental literature data on gas permeation parameters for polyarylat–polysiloxane, polysulfon–polysiloxane, and polycarbonate–polysiloxane block-copolymers are utilized. In order to describe the stationary gas permeability for two-phase systems (from diluted dispersion of one polymer in another to concentrated dispersion and complete phase inversion) the empiric approaches based on modified Maxwell equations are offered. The requirements for two-phase systems with high permeability and selectivity parameters for gas separation are identified. The permeability parameters are predicted for C1–C4 hydrocarbons in block-copolymers based on PDMS dispersion in PVTMS, phase inversion, and PVTMS dispersion in PDMS. Thus, the perspectives of designing heterogeneous membranes based on block-copolymers with predetermined molecular-selective properties are demonstrated.

The kinetics of the reduction of orthorhombic and tetragonal lead oxides to lead with hydrogen has been investigated in the temperature range from 450 to 525°C. The degree of reduction of lead in the orthorhombic oxide as a function of the reaction time is described by the Erofeev equation in which the exponent n is unity. No significant difference in reactivity toward hydrogen between orthorhombic and tetragonal lead oxides has been revealed. The activation energy of the lead oxide reduction reaction is 85.8 ± 8.3 kJ/mol for the orthorhombic phase and 93.1 ± 5.0 kJ/mol for the tetragonal phase, so these values are equal within the activation energy determination error.

Films of ZnO nanorods grown by chemical vapor deposition were functionalized with a chromophore in a stepwise process that preserves the surface morphology. In the first step, the ZnO nanorods were functionalized by exposure to prop-2-ynoic acid (propiolic acid) in vacuum, which did bind through the COOH group leading to a ZnO surface functionalized with ethyne moieties (ethyne/ZnO). In the second step, 9-(4-azidophenyl)-2,5-di-tert-butylperylene (DTBPe-Ph-N3) was reacted with the ethyne/ZnO surface via copper-catalyzed azide–alkyne click reaction (CuAAC) in solution to form the DTBPe-functionalized surface (DTBPe/ZnO). The ZnO morphology was preserved after each step, as demonstrated by scanning electron microscopy (SEM). Each step was probed by X-ray photoelectron spectroscopy (XPS), and transient absorption spectroscopy (TA) of the resulting DTBPe/ZnO surface shows interfacial electron transfer following visible light excitation. As expected, attempts to bind the reference compound 1-(4-(8,11-ditert-butylperylen-3-yl)-phenyl)-1H-1,2,3-triazole-4-carboxylic acid (DTBPe-Ph-Tz-COOH) directly from solution lead to etched surfaces (confirmed by SEM) and undefined binding modes (confirmed by TA).

A summary of the approaches to chemically functionalize the surfaces of inorganic materials and preserve the chemical functionality for further reactions and postmodification is presented. The target chemical functionalities can be introduced as one of the chemical groups on multifunctional compounds. Procedures for using organic multifunctional hydrocarbons to form organic monolayers will be presented, including the self-assembly on metallic materials and monolayer formation on semiconductors. This approach will be compared with the introduction of a functional group directly to the semiconductor surfaces without the use of organic linkers. The need for protective groups and deprotecting chemistry will be considered.

The fabrication of integrated ZIF-8 membranes via a direct in situ crystallization on a porous polyacrylonitrile material and a composite aluminum zirconate based support was performed for the first time. A novel free-seeding synthetic procedure was accomplished without an elevated temperature and autogeneous pressure. The proper choice of the support in combination with the appropriate synthesis procedure allowed for the preparation of phase-pure polycrystalline ZIF-8 membranes. The gas permeation experiments indicated that dense ZIF-8 selective layers, including a multi-layer coating, were perfectly grown on both the supports. Our results revealed a strong impact of the support on the gas separation characteristics of the resulting ZIF-8 membranes.

Catalytic transformation of multifunctional molecules requires understanding of the competing reactions on a surface of a heterogeneous catalyst. Here the reaction of 2-chlorophenol is investigated with ZnO powder that has a potential to be used in environmental remediation. Since it is important to follow every step of surface-catalyzed processes, adsorption and thermally induced transformations of 2-chlorophenol on ZnO powder catalyst were followed by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and supplemented by density functional theory (DFT) investigations. The room temperature adsorption FTIR results show that O–H dissociation is the primary reaction pathway. Room temperature adsorption studies followed by in situ thermal annealing to desired temperature and then quenching back to room temperature followed by XPS prove that C–Cl dissociation in 2-chlorophenol is competing with the O–H dissociation process on ZnO; however, the majority of chlorine is still bound to carbon and can only be removed by thermal annealing together with the phenyl group. DFT description helps to construct the reaction mechanism diagram and O–H dissociation is found to have a reaction barrier of only 62.4 kJ/mol, while C–Cl bond dissociation has a substantially higher barrier of 111.2 kJ/mol. Thus, this set of studies suggests that the reaction of 2-chlorophenol on ZnO powder proceeds selectively towards the O–H dissociation; however, the products released from its surface following thermal annealing contain chlorinated hydrocarbon fragments. This observation implies that it would be difficult to use unmodified ZnO as a catalyst for a direct utilization and mineralization of chlorophenols.

Interaction of hydrazine with Cl-terminated Si(111) surface was explored in order to understand the pathways for obtaining a reactive functionalized silicon surface that is oxygen-free. Hydrazine-functionalized Si(111) surface with Si–NH–NH–Si species was prepared starting with Cl-terminated Si(111) surface in a reaction with anhydrous hydrazine at 35 °C. This process was followed by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry to characterize the modified surface. DFT calculations were performed to supplement the analysis, to identify major surface species resulting from this reaction, and to provide a mechanistic insight into the initial stages of modification. This work provides a new pathway to obtain a well-defined functionalized silicon surface with a Si–N interface that is oxygen- and carbon-free and that can be used for further functionalization or deposition schemes.

Acetone transformations on ZnO powder encompass a number of practical implications for heterogeneous catalysis, and the interest towards this system has fueled a substantial debate over the nature of the adsorbed molecule and its possible self-reactions. This work combines vibrational analysis and computational density functional theory investigation to reconcile some of the disagreements posed by the previous studies spanning wide range of experimental conditions and a variety of ZnO surfaces. The formation of rehybridized and non-rehybridized enolate species following acetone adsorption is analyzed by varying the molecular coverage in computational investigation using cluster models representing ZnO surfaces, and the resulting vibrational spectra are compared with the experimental measurements. In addition, self-aldol-condensation is explored to offer possible surface-catalyzed reaction pathways. Aldol condensation of acetone results in a stable species – enolized diacetone alcohol. Further transformation of this species into mesityl oxide is found to have a very high kinetic barrier.

The crystal structure of an N-terminal β-strand-swapped consensus-derived tenascin FN3 alternative scaffold has been determined. A comparison with the unswapped structure reveals that the side chain of residue F88 orients differently and packs more tightly with the hydrophobic core of the domain. Dimer formation also results in the burial of a hydrophobic patch on the surface of the domain. Thus, it appears that tighter packing of F88 in the hydrophobic core and burial of surface hydrophobicity provide the driving forces for the N-terminal β-strand swapping, leading to the formation of a stable compact dimer.

The mechanism of thermal dry etching of cobalt films is discussed for a thermal process utilizing sequential exposures to chlorine gas and a diketone [either 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) or 2,4-pentanedione (acetylacetone, acacH)]. The process can be optimized experimentally to approach atomic layer etching (ALE); a sequential exposure to Cl(2) and hfacH dry etchants at 140 °C is shown to proceed efficiently. The use of acacH as a diketone does not result in ALE with chlorine even at 180 °C, but the decrease of surface chlorine concentration and chemical reduction of cobalt is noted. However, thermal desorption analysis suggests that the reaction of chlorinated cobalt surface exposed to the ambient conditions (oxidized) with hfacH does produce volatile Co-containing products within the desired temperature range and the products contain Co(3+). The effect of adsorption of ligands on the energy required to remove surface cobalt atoms is evaluated using the density functional theory.