Alcohol-water Mixtures Research Articles

Синтез 5-амино-3-арил-1H-пиразол-4-карбонитрилов на основе гидразинов или бензгидразидов в условиях ультразвуковой активации

Pyrazoles containing amino and carbonitrile groups have a wide range of biological activities, including antimicrobial, antiinflammatory, antitumor, antioxidant, and are used to create pesticides and dyes. Also, these compounds are synthons for the preparation of various polyheterocyclic compounds. New potentially biologically active 5-amino-3-aryl-1H-pyrazole-4-carbonitriles containing pharmacophoric substituents have been obtained via three-component condensation reactions of malonic dinitrile with substituted aromatic aldehydes and benzhydrazides or hydrazines. This work considers the limits of applicability of hydrazines and hydrazides as weak nucleophiles in similar processes. The described target compounds have been synthesized using the «green chemistry» approach under ultrasonic activation in water or a mixture of water and isopropyl alcohol in the presence of triethylamine as base catalyst. The applicability of this environmentally friendly, economical and efficient approach for the synthesis of nitrogen-unsubstituted (7, 8) and N-aryl- (4, 6) or N-aroyl-substituted (1–3) pyrazole-4-carbonitriles has been demonstrated. The target pyrazole-4-carbonitrile (2) is formed and Schiff base (2’) is released as a by-product in the reaction of the weak binucleophile 3-nitrobenzhydrazide with 4-benzyloxy-3-methoxybenzaldehyde and malonic dinitrile. Step-by-step syntheses have shown that the initial reaction of a three-component interaction can be either croton condensation or the formation of a Schiff base. In any case, during subsequent heterocyclization, unstable substituted pyrazolines are formed, which aromatize to the target pyrazoles in the presence of atmospheric oxygen under synthesis conditions. The composition and structure of the products have been confirmed by elemental analysis, NMR 1H, 13C spectroscopy, HSQC, and HMBC heteronuclear correlations.

Deciphering the role of plasticizers and solvent systems in hydrophobic polymer coating on hydrophilic core

The type of plasticizer and the choice of solvent or co-solvents used for coating of a hydrophilic core can greatly impact the permeability, porosity, and mechanical strength of the polymer film. Although, Ethylcellulose (EC) is an old polymer, it is a polymer of choice for modifying the drug release due to its inherent properties. The ability of polymers like EC alone to form a diffusion-controlling membrane with good mechanical properties is limited. To modulate the drug release as per the desired profile and modify the film properties, ethylcellulose is often used with hydrophilic hypromellose (HPMC) along with plasticizers. The main focus of the current study was the identification of an appropriate solvent system and plasticizer for the ethylcellulose-hypromellose polymer combination. The study evaluated the coating solution properties, the feasibility and efficiency of the process, the physical attributes of the tablet, the surface properties of the polymer film, the in-vitro drug release and behavior, and the impact of curing time on surface properties and drug release, among other factors.The isopropyl alcohol-water mixture (9:1) produced a homogeneous film in comparison to films produced by other solvents. Although both hydrophilic and hydrophobic plasticizers produce homogeneous films, hydrophilic plasticizers have a higher rate of drug diffusion than hydrophobic plasticizers. During the tablet curing and stability study, the drug release from the polymeric film coating with triethyl citrate decreased moderately and with polyethylene glycol decreased significantly. The presence of hydrophobic plasticizers, viz., dibutyl sebacate and acetyl tributyl citrate, in the polymeric film coating does not impact drug release. For the combination of ethylcellulose and hypromellose, it was found that a mixture of isopropyl alcohol and water (9:1) worked better as a solvent for coating solutions, and hydrophobic plasticizers lower the risk associated with coating ethylcellulose and hypromellose together.

Short-side-chain perfluorinated polymeric membranes annealed at high temperature: Structure, conductivity, and fuel cell performance

The relationship between the mechanical, electrical, and morphological properties of annealed films based on short-side-chain perfluorinated sulfonic acid ionomer (SSCI) with an Aquivion structure was systematically investigated using dynamic mechanical analysis (DMA), small-angle X-ray scattering (SAXS), and impedance spectroscopy. Annealing the membranes at temperatures of 140, 150, and 160 °C—above the glass transition temperature of SSCI—and the nature of the liquid phase in the polymer dispersion significantly influence the structural parameters of the membranes, specifically the size of the conductive channels formed by hydrophilic sulfonic acid groups. SAXS and AFM analyses revealed that membranes cast from N,N-dimethylacetamide (DMAA) exhibit a denser, less structured morphology, resulting in lower hydrogen permeability (φ = 4.6 ± 0.7 nmol/m/s/MPa), comparable to the commercial Nafion 211 membrane (φ = 6.5 nmol/m/s/MPa), but with significantly lower proton conductivity (35 ± 5 mS/cm) than Nafion 211 (95 mS/cm). In contrast, membranes obtained from a water-alcohol mixture showed a well-defined structure (SAXS, AFM), with proton conductivity values ranging from 70 to 103 mS/cm, comparable to Nafion 211. However, the hydrogen permeability of these membranes varied significantly depending on the annealing conditions (φ = 5.5–65.3 nmol/m/s/MPa). SAXS data indicated that the membranes had a similar degree of crystallinity (11–13%) but differed in the positions of the ionomer peak and matrix knee, which are associated with variations in the size of the conductive channels and account for the observed differences in ionic conductivity. Membranes annealed at 150 °C, which exhibited hydrogen permeability and ionic conductivity values close to those of the commercial Nafion 211 membrane, were used to fabricate membrane electrode assemblies (MEA). The electrochemical characteristics of these MEAs were investigated at 30 and 60 °C, 100% relative humidity, at both atmospheric pressure and 200 kPa overpressure. At a current density of 1.75 A/cm2, the fabricated membranes demonstrated power outputs of up to 550 and 950 mW/cm2, which are comparable to, and even exceed, those of the commercial Nafion 211 membrane (700 mW/cm2). However, despite the high-power performance, significant membrane degradation was observed after 10,000 cycles in durability tests. These findings contribute to a better understanding of the relationship between the electrochemical properties and the structure of short-side-chain perfluorinated sulfonic acid ionomers with an Aquivion-type structure and are expected to enhance their application in fuel cells.

Towards the automation of nanoparticle syntheses: The case study of gold nanoparticles obtained at room temperature

Automation is promising to investigate in detail the effect(s) of parameters that influence the synthesis and properties of nanomaterials. However, it remains challenging to automate even selected key-steps of most wet-chemical syntheses of nanoparticles. Here, a simple, affordable, yet modular, automated station reported for the synthesis of chemicals is adapted to study nanomaterial syntheses, to timely screen larger multi-parameter spaces, to gain a deeper knowledge and awareness on parameters to control, to ultimately achieve more reproducible and sustainable syntheses. As a case study, this automated station is implemented to investigate and develop surfactant-free gold nanoparticles obtained at room temperature in alkaline water-alcohol mixtures. It is shown that the NaOH/Au molar ratio is a to-be-preferred descriptor to control the optical properties and size of the gold colloids for surfactant-free glycerol-mediated syntheses. Size control is simply achieved by carefully tuning the glycerol content and/or amount of base. For ethanol-mediated synthesis, the NaOH/Au molar ratio is also a suitable knob to control the nanoparticle properties. The results pave the way to higher throughput nanoparticle syntheses, ultimately relevant to timely build the missing larger datasets relevant for artificial intelligence, to one day routinely achieve the self-driven discovery of new nanomaterials and their related synthesis.

Effect of Dispersion Media Composition on the Structure and Rheology of the Short-Sidechain Perfluorosulfonic Acid Ionomer Dispersions

Perflourosulfonic acid (PFSA) ionomers are used in many applications including polymer-electrolyte membrane fuel cells and electrolysers owing to their many attractive properties such as excellent ion-conductivity, chemical resistance, mechanical properties, and thermal stability. In polymer-electrolyte membrane fuel cells and electrolysers, they are used as the membrane and as a component in the catalyst layers, to provide proton conductivity and serve as a binder for the catalyst particles, which are two key components of these devices. Understanding the structure and rheological properties of the ionomer dispersions is important for solution-processed fabrication of the membranes and the catalyst layers, and will enable better control their final structure/morphology, and improve the device performance. A water-alcohol solvent mixture is a common dispersion media for ionomer dispersions as well as the catalyst inks. While significant efforts exist on the structure of ionomer dispersions in water-alcohol solvent mixtures, their rheological properties, particularly the effect of solvent composition at non-dilute concentrations remain less explored. In this talk, the effect of water-alcohol (isopropanol) composition of the dispersion media on the rheological properties of ionomer dispersions will be presented. The results of small-angle x-ray scattering characterization of the ionomer dispersions will be also discussed. As a model ionomer, a short sidechain perfluorinated ionomer (PFSA), produced by 3M, was used. In dispersions with low ionomer concentrations, the zero-shear viscosity scaling with concentration was found to be similar for all alcohol fractions in the solvent mixture, following Fuoss’s law for polyelectrolytes. Whereas at higher concentrations, beyond the semi-dilute unentangled regime, their scaling was strongly dependent on alcohol fraction, where the scaling exponent increasing with increasing the alcohol fraction. Furthermore, the dispersions showed dramatic shear-thickening and strain-stiffening behaviors at higher alcohol fractions. The rheological observations suggest water-alcohol composition significantly alters the interactions between ionomer, and consequently their structure, and has strong implications in processing as well as on the morphology/structure of the membranes and the catalyst layers.

Understanding the structures and interactions in gaseous mixtures of water-alcohol by high-resolution infrared spectroscopy

Interactions of water and chemical or bio-compound have a universal concern and have been extensively studied. For spectroscopic analysis, the complexity and the low resolution of the spectra make it difficult to obtain the spectral features showing the interactions. In this work, the structures and interactions in gaseous water and water-alcohol mixtures were studied using high-resolution infrared (HR-IR) spectroscopy. The spectral features of water clusters of different sizes, including dimer, trimer, tetramer and pentamer, were observed from the measured spectra of the samples in different volume concentrations, and the interactions of water and methanol/ethanol in the mixtures were obtained. In the analysis, a method based on principal component analysis was used to separate the overlapping spectra. In water-alcohol mixtures, when water is less, water molecules tend to interact with the OH groups on the exterior of the alcohol aggregate, and with the increase of water, a water cage forms around the aggregates. Furthermore, the ratio of the molecule number of methanol in the aggregate to that of water in the cage is around 1:2.3, and the ratio for ethanol is about 1:3.2.

Amphoteric SnO2 nanoparticles via pH-controlled continuous flow solvothermal synthesis

Amphoteric oxides can be challenging to produce in phase pure form due to their sensitivity to the pH of the reaction mixture. The high-pressure, high-temperature reaction conditions of hydrothermal processes make the pH difficult to control. Here we report a simple approach to obtain nanoparticles of amphoteric oxides, where cheap metal nitrate precursors are reacted in alcohol (2-propanol) water mixtures (25 vol%:75 vol%) to maintain a neutral pH under solvothermal conditions. Phase pure SnO2 nanoparticles were synthesized in a continuous flow solvothermal reactor at 250 °C, 300 °C, 350 °C and 400 °C with sizes ranging from 3 nm to 7 nm. The nanoparticles were characterized using powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, 119Sn MAS NMR spectroscopy, Brunauer-Emmett-Teller nitrogen adsorption, UV–VIS, and as anode material in CR2032 Li-ion battery cells. To demonstrate generality, amphoteric oxides ZnO, Bi2O3, Cr2O3 and γ-AlOOH were also synthesized.

Peculiar wetting behavior of nanodroplets comprising antagonistic alcohol-water mixtures on a graphene surface

Binary mixtures, consisting of partially and totally wetting liquids with respect to a specific substrate and known as an antagonistic mixture, are commonly encountered. Although the wetting behavior of antagonistic mixtures deviates from that of conventional liquids, studies exploring this phenomenon are scarce. At the nanoscale, the wetting behavior of nanodroplets containing such mixtures may diverge even further from our established understanding. Employing Nanoscale Molecular Dynamics simulations, we explore the wetting behavior of nanodroplets containing mixtures of water (partial wetting) and ethanol or isopropanol (total wetting) on a graphene surface. By adjusting the water fraction (xw) in the antagonistic mixture, three distinct wetting states have been identified: (I) In total wetting regime (low xw), spontaneous spreading is observed; (II) In plateau regime (medium xw), alcohol leakage from the droplet occurs, with the apparent contact angle (CA) remaining constant; (III) In partial wetting regime (high xw), the CA increases with xw and alcohol molecules tend to accumulate at the contact line. Unexpectedly, the spreading coefficient (S) remains positive and turns negative only as xw near unity. Furthermore, Young's equation proves to be inapplicable even when S < 0. These peculiar wetting phenomena are comprehensively discussed and elucidated.

АНТИОКСИДАНТНА АКТИВНІСТЬ ЕКСТРАКТІВ SCORZONERA PURPUREA SUBSP. ROSEA

The antioxidant properties of ethanol-water extracts of Scorzonera purpurea subsp. rosea obtained by maceration with ethanol content of 50 % (E50) and 70 % (E70) were studied using the DPPH (E50 – 82 %, E70 – 86 %), ABTS (E50 – 89 %, E70 – 93 %) and FRAP (E50 – 23.01 μmol/ml, E70 – 23.58 μmol/ml) methods. It was determined that the studied extracts differ little in the total content of extractive substances (E50 – 19.86 mg/ml, E70 – 19.4 mg/ml), the sum of polyphenolic compounds (E50 – 2.02 mgGC/ml, E70 – 2.11 mgGC/ml), flavonoids (E50 – 0.235 mgC/ml, E70 – 0.276 mgC/ml). The obtained results indicate the expediency of using an alcohol-water mixture with an ethanol content of 50 % as a cheaper extractant for the preparation of Scorzonera purpurea extracts with a pronounced antioxidant effect.

Co-Adsorption of Alcohols and Water in JUK-8 Studied Using Quasi-Equilibrated Thermodesorption.

JUK-8 ([Zn(oba)(pip)]n, oba2- = 4,4'-oxybis(benzenedicarboxylate), pip = 4-pyridyl-functionalized benzene-1,3-dicarbohydrazide) is a hydrolytically stable flexible metal-organic framework. Owing to its unusual adsorptive properties, JUK-8 can be considered as a promising sensing material for construction of detectors of volatile organic compounds (VOCs) in air. Quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) is a versatile method dedicated to characterization of porous materials. In this work, QE-TPDA was employed to study co-adsorption of water and selected alcohols in JUK-8. For the first time an infrared detector sensitive to organic compounds was used in the QE-TPDA measurements, allowing the study of the influence of water vapor on sorption of VOCs. The QE-TPDA profiles of the studied alcohols, exhibiting two desorption maxima and two adsorption minima, are consistent with the standard sorption isotherms, revealing a two-step adsorption-desorption mechanism. The profiles recorded in the presence of water are noticeably changed in different ways for different alcohols. While at low relative humidity (RH) (ca. 20%) the low temperature adsorption states of ethanol and 1-propanol were only slightly destabilized, for 2-propanol almost complete suppression of adsorption was observed. The results found for moderate RH levels (ca. 50%) indicated that the opening of the JUK-8 structure, responsible for its breathing behavior, was followed by the filling of the just generated pores with a water-alcohol mixture.

Influence of the alcohol and water grades on surfactant-free colloidal syntheses of gold nanoparticles in alkaline water-alcohol mixtures

To make the most of the unique properties of nanomaterials, and to bridge the gap between fundamental and applied research, controlled, green, cheap and energy efficient syntheses of nanoparticles are required. In this respect, room and low temperature surfactant-free colloidal syntheses of nanoparticles obtained in low viscosity and low boiling point solvents, without additives or nature-derived extracts, are promising to develop more active (electro)catalysts. Recently, a room temperature synthesis of surfactant-free gold nanoparticles has been documented (Chem. Mater. 2023, 35, 5, 2173) that requires only water, a base such as NaOH, an alcohol and HAuCl4. Unfortunately, the syntheses of nanomaterials are often sensitive to multiple parameters and it is well acknowledged that reproducibility is a general challenge in the chemical sciences, where the synthesis of nanomaterials is no exception. Here, we investigate the effect of the water conductivity and solvent grade on the surfactant-free low temperature (ca. 30 °C) synthesis of colloidal gold nanoparticles obtained in alkaline mixtures of ethanol and water. The synthesis can be performed with relatively low-grade ethanol but requires high purity water. The importance of water with low conductivity is also stressed for syntheses where ethylene glycol and glycerol are used as source of reducing agents. The results of this study over 100 samples pave the way to greener, more controlled and scalable syntheses of surfactant-free gold nanomaterials.

Magnetocaloric refrigerator with magnetic pump and liquid metals

One-seventh of the worldwide electricity is used for refrigeration related activities. When compared to the predominantly used vapor compression refrigeration system, magnetocaloric refrigeration provides an energy-efficient and eco-friendly alternative. It utilizes a magnetocaloric material which undergoes temperature changes when exposed to magnetic field changes. Nearly 60% of the total system cost is due to the permanent magnets used. For a given cooling power, the amount of permanent magnet needed is determined by the residence time required by the heat transfer fluid in each cycle. The start-of-the-art systems utilizes water-alcohol mixture as the heat transfer fluid, and a mechanical pump for its circulation. By utilizing non-toxic and non-hazardous gallium-indium-tin based liquid metals as heat transfer fluid, which has three order of magnitude higher thermal diffusivity, the residence time and the permanent magnetic material is reduced nearly by a factor of 10. Even accounting for the cost of the liquid metal, it results in considerable savings in the system cost. We present experimental results on the entropy change of using liquid metal with (Mn,Fe)2(P,Si)-based magnetocaloric material, and numerical results on the system level analysis. Further, to improve the reliability of the system, we propose to use magnetic pumping for heat transfer fluid circulation, which does not have any moving parts. The state-of-the art magnetic pump works at frequencies in the range of 100 to 1000 Hz. However, they cause detrimental heating effects due to eddy current losses. To overcome this, we have designed a pump that operates at 1 Hz and still achieves comparable flow rates. We present numerical results on the pump design by studying the dynamics of ferrofluid rise in a vertical pipe with multiple electromagnetic coils.

Investigation of Dielectric Constants of Alcohol-Water Mixtures by Microwave (MW) Spectroscopy Technique

Over the last few decades, the utilization of microwave (MW) spectroscopy applications in industry has grown dramatically. This technique is very useful as it gives very important details about alcohol-water mixtures through the measurement of dielectric parameters (Ɛ’ and Ɛ”). This research determined the dielectric parameters (Ɛ’ and Ɛ”) of ethanol-water and methanol-water mixtures for concentration changes from pure water to pure alcohol. The ethanol-water and methanol-water mixture volume fractions of 43% and 44%, respectively, as well as the molar fractions xet≈ 0.20M and xmet ≈ 0.26M, obtained the breaking points of the dielectric parameters (Ɛ’ and Ɛ”).

3D-Printable Sustainable Bioplastics from Gluten and Keratin.

Bioplastic films comprising both plant- and animal-derived proteins have the potential to integrate the optimal characteristics inherent to the specific domain, which offers enormous potential to develop polymer alternatives to petroleum-based plastic. Herein, we present a facile strategy to develop hybrid films comprised of both wheat gluten and wool keratin proteins for the first time, employing a ruthenium-based photocrosslinking strategy. This approach addresses the demand for sustainable materials, reducing the environmental impact by using proteins from renewable and biodegradable sources. Gluten film was fabricated from an alcohol-water mixture soluble fraction, largely comprised of gliadin proteins. Co-crosslinking hydrolyzed low-molecular-weight keratin with gluten enhanced its hydrophilic properties and enabled the tuning of its physicochemical properties. Furthermore, the hierarchical structure of the fabricated films was studied using neutron scattering techniques, which revealed the presence of both hydrophobic and hydrophilic nanodomains, gliadin nanoclusters, and interconnected micropores in the matrix. The films exhibited a largely (>40%) β-sheet secondary structure, with diminishing gliadin aggregate intensity and increasing micropore size (from 1.2 to 2.2 µm) with an increase in keratin content. The hybrid films displayed improved molecular chain mobility, as evidenced by the decrease in the glass-transition temperature from ~179.7 °C to ~173.5 °C. Amongst the fabricated films, the G14K6 hybrid sample showed superior water uptake (6.80% after 30 days) compared to the pristine G20 sample (1.04%). The suitability of the developed system for multilayer 3D printing has also been demonstrated, with the 10-layer 3D-printed film exhibiting >92% accuracy, which has the potential for use in packaging, agricultural, and biomedical applications.

Do Nanobubbles Exist in Pure Alcohol?

The existence of nanobubbles in pure water has been extensively debated in recent years, and it is speculated that nanobubbles may be ion-stabilized. However, nanobubbles in the alcohol-water mixture and pure alcohols are still controversial due to the lack of ions present in the alcohol system. This work tested the hypothesis that stable nanobubbles exist in pure alcohol. The ultrasound and oscillatory pressure fields are used to generate nanobubbles in pure alcohol. The size distribution, concentration, diameter, and scattering intensity of the nanobubbles were measured by nanoparticle tracking analysis. The light scattering method measures the zeta potential. The Mie scattering theory and electromagnetic wave simulation are utilized to estimate the refractive index (RI) of nanobubbles from the experimentally measured scattering light intensity. The average RI of the nanobubbles in pure alcohols produced by ultrasound and oscillating pressure fields was estimated to be 1.17 ± 0.03. Degassing the nanobubble sample reduces its concentration and increases its size. The average zeta potential of the nanobubbles in pure alcohol was measured to be -5 ± 0.9 mV. The mechanical stability model, which depends on force balance around a single nanobubble, also predicts the presence of nanobubbles in pure alcohol. The nanobubbles in higher-order alcohols were found to be marginally colloidally stable. In summary, both experimental and theoretical results suggest the existence of nanobubbles in pure alcohol.

НАБУХАНИЕ ПОЛИУРЕТАНОВЫХ ПЛЕНОК НА ОСНОВЕ АМИНОЭФИРОВ БОРНОЙ И ОРТОФОСФОРНОЙ КИСЛОТ В ВОДНЫХ РАСТВОРАХ СПИРТОВ

In this work we have carried out studies to determine the sorption capacity (swelling) of polymer polyurethane films based on amino esters of boric and orthophosphoric acids in pure components (water, isopropyl and ethyl alcohols) and water-alcohol mixtures (isopropanol-water, ethanol-water) at temperatures of 22, 40 and 60 °С. On the basis of the data on the sorption capacity of components through polymer films a preliminary assessment of the prospects of using the investigated polymers as a selective layer of pervaporation membranes is made. The changes in the volume-mass concentration of low-molecular-weight components in polymer films depending on the solvent concentration in the initial mixture and the temperature of the process have been determined experimentally. The obtained data are necessary for creating a mathematical model of the pervaporation separation process. The paper describes the developed methodology for the fabrication of polymer films based on amino esters of orthophosphoric and boronic acids. Hyperbranched polyols with high solubility and low characteristic viscosities were used as crosslinking agents in the synthesis of the studied polymers Experimental studies for water-alcohol mixtures were carried out in a wide range of alcohol concentrations (0-99 wt.%). The swelling dynamics of polymer films in water-alcohol mixtures and individual components were measured. For all films, a tendency of decreasing volume-mass concentration with increasing process temperature in isopropyl alcohol and water can be seen, but in ethyl alcohol the volume-mass concentration increases with exceeding the process temperature.

КОЭФФИЦИЕНТЫ ДИФФУЗИИ И АКТИВНОСТЬ КОМПОНЕНТОВ ВОДНОСПИРТОВЫХ СМЕСЕЙ В ПОЛИУРЕТАНОВЫХ ПЛЕНКАХ НА ОСНОВЕ АМИНОЭФИРОВ БОРНОЙ И ОРТОФОСФОРНОЙ КИСЛОТ

The work carried out studies to determine the diffusion coefficients and activities of water, isopropyl and ethyl alcohols in polymer polyurethane films based on amino esters of boric and orthophosphoric acids at temperatures of 22, 40 and 60 °C. To determine the diffusion coefficients, we used data on the dynamics of sorption of low molecular weight components in the polymers under study, presented in our previous study. To describe the process of swelling of a polymer film, the Fick differential equation was used; the process was represented as unsteady diffusion in a flat plate. The initial condition was the absence of a component in the polymer at the initial moment of time; the solution to the differential equation was the non-stationary field of concentrations of the component in the film. The experimental dependences of changes in the volume-mass concentration of components in the polymer were described using the Heaviside switching function; due to the presence of a maximum in the swelling curve, it is associated with a restructuring of the polymer structure that occurs due to possible relaxation processes. By minimizing the discrepancies between the calculated and experimental values of the concentration versus time dependence, the diffusion coefficients of pure components in AEPA and AEBA films were determined. Based on data on the diffusion of components through polymer films, the separation characteristics of polymers were assessed for their use as a selective layer of pervaporation membranes. Based on swelling data over long periods of time for water-alcohol mixtures of various compositions, the parameters of the Flory-Huggins model were determined for calculating the activities of components in the polymer. It was shown that among the solvents under study, water has the highest diffusion coefficient, and isopropyl alcohol has the lowest, regardless of the type of film (AEPA/AEBA). For all films, there is a tendency for the diffusion coefficient to increase with increasing temperature, regardless of the solvent.

ПЕРВАПОРАЦИОННОЕ РАЗДЕЛЕНИЕ ВОДНО-СПИРТОВЫХ СМЕСЕЙ НА ПОЛИУРЕТАНОВЫХ МЕМБРАНАХ НА ОСНОВЕ АМИНОЭФИРОВ БОРНОЙ И ОРТОФОСФОРНОЙ КИСЛОТ: ЭКСПЕРИМЕНТ И МОДЕЛИРОВАНИЕ

In this work, the separation characteristics of a selective layer of pervaporation membranes made of polyurethanes based on amino esters of orthophosphoric acid (AEPA) and amino esters of boric acid (AEBA) were studied during the dehydration of azeotropic water-alcohol mixtures. Polymer compositions of polyurethanes based on various compositions of AEPA and AEBA were studied in order to identify the best options. For polyurethane based on AEPA, moles of orthophosphoric acid influenced the composition of the polymer composition; for polyurethane based on AEBA, the effect of modifiers (bulk adducts of diphenylolpropane diglycidyl ether and copper chloride) was measured. A technology has been developed for the production of polymer pervaporation membranes with a selective layer of restrictive polyurethanes. Experimental studies on the pervaporation dehydration of isopropanol/water and ethanol/water mixtures in various alcohol concentrations (50-99 wt%) and various feedstock temperatures are presented. Obtains permeate flux and separation factor results for membrane confinement when separating confinement mixtures. It has been determined that an increase in the moles of orthophosphoric acid in the composition of the polymer composition AEPA and the use of modifiers in the synthesis of the polymer composition AEBA improve the separation characteristics of pervaporation membranes. It was revealed that when the process temperature increases by 20 °C, the permeate flow through the membrane increases, for example, for polyurethane based on AEPA-5-PEG, the value increases by 2 times, with a practically unchanged separation coefficient. Based on the pervaporation separation index data, promising polymer compositions were selected. The results of the data obtained are compared with the studies of other authors; the membranes we use have high values of permeate flux and separation coefficient, which are consistent with the values for any membranes from the open literature. Based on the concept of dissolution-diffusion, the process of pervaporation of isopropanol/water and ethanol/water mixtures through polymer membranes was simulated. The given calculation system is cyclic, and the results of calculating the permeate flow and separation coefficient using this model are in good agreement with the experimental data obtained.

Heat transfer in a channel with internal intensifiers during azeotropic mixture circulation

Today, the use of mixtures as refrigerants and coolants in various energy systems is widespread. The volatility coefficients for the components of a non-azeotropic binary mixture vary significantly. In an azeotropic binary mixture, the volatility coefficients for both components are the same. This paper presents the experimental results on the intensity of heat transfer to an azeotropic alcohol-water mixture during forced circulation in a round heated channel. Experiments are carried out both in a smooth channel and in a channel with a spiral intensifier. The inner diameter of the channel is D = 7.6 mm, the length is 2 m. The intensifier surface has a hydrophobic coating. The experiments are carried out at low (0.03 – 0.04 MPa) pressure in the system, in the range of mass velocities 36 &lt; M &lt; 376 kg/m2s and Reynolds numbers of 360 – 3700. The heat flux density in these experiments is 8000 W/m2. In the single-phase flow of an azeotropic alcohol-water mixture in the channel with a spiral intensifier, the heat transfer coefficient is up to 5–6 times higher than that in a smooth channel. In this case, the higher the mass flow velocity, the greater the excess of the heat transfer coefficient. In the two-phase flow of the mixture in the channel with a spiral intensifier, the heat transfer coefficient is up to 2–3 times higher than that in a smooth channel.

Modelling of structure and concentration characteristics of water-alcohol solutions

Water-alcohol solutions are widely used in pharmacy, food industry, engineering, etc. The study of their physical and chemical properties has a long history. Nevertheless, due to the complexity of these systems, there is still an interest in their research stimulated by the development of biochemistry in terms of the study and protection of the environment, global climate change, renewable energy resources and cosmochemistry. The purpose of the presented study is the quantum-chemical investigation of water clusters with methyl and ethyl alcohol molecules, as well as the modelling of concentration dependences of the excess molar volume of ethyl alcohol solution in water at different temperatures. Based on quantum-chemical calculations of paired and mixed complexes of water with methanol and ethanol, taking into account solvation effects, study reveals the formation of thermodynamically efficient complexes in liquid, in contrast to the ideal gas state, while in the mixture both individual solvated alcohol molecules and complexes will be in equilibrium. We noted a relative difference in the free energies of solvation of paired and mixed methanol and ethanol complexes. The paper proposes a technique for calculating the excess molar volume in water-alcohol mixtures by approximating the experimental dependences by Lejandre polynomials of the ninth degree. The calculation results showed high accuracy. Hence, continuous functions describe the dependences of the calculated coefficients of Lejandre polynomials on temperature.