Water Mole Research Articles

Structural evolution of water-in-propylene carbonate mixtures revealed by polarized Raman spectroscopy and molecular dynamics.

The liquid structure of systems wherein water is limited in concentration or through geometry is of great interest in various fields such as biology, materials science, and electrochemistry. Here, we present a combined polarized Raman and molecular dynamics investigation of the structural changes that occur as water is added incrementally to propylene carbonate (PC), a polar, aprotic solvent that is important in lithium-ion batteries. Polarized Raman spectra of PC solutions were collected for water mole fractions 0.003 ≤ χwater ≤ 0.296, which encompasses the solubility range of water in PC. The novel approach taken herein provides additional hydrogen bond and solvation characterization of this system that has not been achievable in previous studies. Analysis of the polarized carbonyl Raman band in conjunction with simulations demonstrated that the bulk structure of the solvent remained unperturbed upon the addition of water. Experimental spectra in the O-H stretching region were decomposed through Gaussian fitting into sub-bands and comparison to studies of dilute HOD in D2O. With the aid of simulations, we identified these different bands as water arrangements having different degrees of hydrogen bonding. The observed water structure within PC indicates that water tends to self-aggregate, forming a hydrogen bond network that is distinctly different from the bulk and dependent on concentration. For example, at moderate concentrations, the most likely aggregate structures are chains of water molecules, each with two hydrogen bonds.

Comb-assisted cavity ring-down spectroscopy for ultra-sensitive traceable measurements of water vapour in ultra-high purity gases

We report on the development of a comb-assisted cavity ring-down spectrometer for trace water mole fraction determinations in high purity gases. By tuning the laser light in coincidence with a H2O absorption line at 1.3946 µm, we were able to determine sub-ppm relative concentrations of water vapour in N2 with a sub-percent statistical uncertainty. The sensitivity of the spectrometer was carefully assessed, yielding a detection limit of about 2 nmol/mol.

Mixed micelle formation by sodium dodecylsulfate and dodecyltrimethylammonium bromide in aqueous ionic liquid media

Surfactant self-aggregation within ionic liquid (IL) - based media has been investigated to compare and contrast the role of such media with that of water. Behavior of a surfactant mixture constituting of two surfactants with oppositely charged head groups, namely anionic sodium dodecylsulfate (SDS) and cationic n-dodecyltrimethylammonium bromide (DTAB), is assessed in aqueous IL media. Contrary to what is observed in water, it is shown earlier that effective charge screening of the surfactant headgroups by IL ions in a typical IL 1-ethyl-3-methylimidazolium ethylsulfate ([C2C1im][EtSO4]) results in formation of (SDS + DTAB) mixed micelles with critical micelle concentrations (CMCs) ranging between those of SDS and DTAB, respectively. The miscibility of (SDS + DTAB) mixture in aqueous [C2C1im][EtSO4] reveals that as the content of IL [C2C1im][EtSO4] is increased, the miscibility of the surfactant mixture improves indicating increased charge screening involving ions of the IL and the surfactant headgroups. For water mole fraction (XW) ≤ 0.90, (SDS + DTAB) surfactant mixture is miscible in aqueous [C2C1im][EtSO4] system in all proportions. For 1.00 ≥ XW≥ 0.90, while synergism persists due to the presence of attractive electrostatic attraction between SDS and DTAB headgroups leading to mixture CMCs below the CMCs of SDS and DTAB, respectively, the extent of synergism diminishes with increase in IL [C2C1im][EtSO4] in the solution. For XW = 0.80, the (SDS + DTAB) mixture exhibits CMC values that are closest to the values estimated assuming ideal behavior. For 0.70 ≥ XW ≥ 0.30, the (SDS + DTAB) exhibits antagonistic trend with CMC values higher than those estimated for ideal solution; the antagonistic trend gradually decreases with increase in [C2C1im][EtSO4] and again attains close to ideal behavior in neat IL [C2C1im][EtSO4]. This trend is subsequently manifested in the composition of the mixed micelles as well as in the net interaction parameter, β. Addition of small proportion of IL to water helps in solubilization of surfactant mixture of oppositely charged surfactants due to effective charge screening of the surfactant headgroups and results in formation of mixed micelles in aqueous IL media over complete composition range.

Numerical study on the performance of the thermoelectric generator with different air-water mixtures

Thermoelectric generators (TEGs) have been widely used to convert thermal energy into electrical energy directly. Nowadays, the most popular TEG applications, such as vehicle heat recovery and geothermal power generation, typically utilize water as the cooling working fluid. Water sources, however, may not be available or extremely limited in some cases. Therefore, in this study, we proposed a new method of mixing water and air as the working fluid to save water. It is necessary to find out the suitable ratio of water to air, under which the performance loss could be minimized. A numerical model of TEG was built utilizing COMSOL Multiphysics to investigate the effect of water mole fraction (WMF, representing water to air ratio) on the performance of TEG, where the properties of the air-water mixture (AWM) could vary with WMF. In this study, 5 cases were considered at different flow velocities, different WMFs, and different combinations of air, water, and AWMs. The effects of these parameters on the voltage and the output power of TEGs were studied and analyzed. The TEG module could generate higher voltage and power output with increasing velocity and WMF. When air fixed on one side, only 0.2 of WMF on the other side could boost over 1.5 times of voltage and 3 times of power generation than only using air. Based on the simulation results, TEGs reach the best performance when the value of WMF is equal to 0.5 on both sides.

Supersonic combustion diagnostics with dual comb spectroscopy

Supersonic engine development requires accurate and detailed measurements of fluidic and thermodynamic parameters to optimize engine designs and benchmark computational fluid dynamic (CFD) simulations. Here, we demonstrate that dual frequency comb spectroscopy (DCS) with mode-locked frequency combs can provide simultaneous absolute measurements of several flow parameters with low uncertainty across a range of conditions owing to the broadband and ultrastable optical frequency output of the lasers. We perform DCS measurements across a 6800–7200 cm−1 bandwidth covering hundreds of H2O absorption features resolved with a spectral point spacing of 0.0067 cm−1 and point spacing precision of 1.68 × 10−10 cm−1. We demonstrate 2D profiles of velocity, temperature, pressure, water mole fraction, and air mass flux in a ground-test dual-mode ramjet at Wright-Patterson Air Force Base. The narrow angles of the measurement beams offer sufficient spatial resolution to resolve properties across an oblique shock train in the isolator and the thermal throat of the combustor. We determine that the total measurement uncertainties for the various parameters range from 1% for temperature to 9% for water vapor mole fraction, with the absorption database/model that is used to interpret the data typically contributing the most uncertainty (leaving the door open for even lower uncertainty in the future). CFD at the various measurement locations show good agreement, largely falling within the DCS measurement uncertainty for most profiles and parameters.

Methane Diffusion Through Nanopore-Throat Geometry: A Molecular Dynamics Simulation Study

SummaryMolecular diffusion dominates over pressure-driven convection as the major mass transport mechanism in nanoporous media with <10-nm pores, which is typical pore size for shale gas recovery. To study fluid behavior at this scale, molecular dynamics (MD) simulation has been widely applied. Nevertheless, classic capillary tube or slit models are of uniform geometry that miss the converging-diverging pore-throat feature, while more realistic models lose simplicity and generality.In this work, we propose a novel geometric model that can reproduce the realistic converging-diverging structure in subsurface porous media without any additional complexity compared to classic slit or capillary models. In this pore-throat model, we are able to identify how nonuniform geometry affects the methane diffusion for both pure methane and for methane mixtures with water, carbon dioxide, and helium.For a pure methane system, we demonstrate the fundamental impact of throat width on diffusion coefficient when the throat width is narrower than 20 Å and identify a critical throat width that determines whether methane can self-diffuse though the throat. This critical throat size is regulated by the energy barrier at the throat rather than by molecular size. We then introduce a semianalytical model to predict self-diffusion coefficient as a function of pressure, temperature, and throat width.For mixtures, we observe the key impact of spatially nonuniform fluid distribution in determining diffusion. Water or carbon dioxide can locally concentrate at the throat, which reduces methane diffusivity, while helium prefers to stay in the pore body, which mildly enhances methane diffusivity. Specifically, although residual water reduces methane diffusion (26% reduction for 20% water molar fraction), it completely blocks the throat and thus prohibits pressure-driven methane convection. By comparison, the dominance of molecular diffusion over convection can be extended to larger pores in presence of residual water. It provides an explanation on shale gas production when connate water is expected to block the flow path.

Thermodynamic properties (excess and partial molar volume, Gibbs free energy of activation for viscous flow, enthalpy, and entropy) of propylammonium nitrate/water mixtures

The purpose of this study is to use thermodynamic functions to clarify the change in the solution structure and interaction of the propylammonium nitrate (PAN)/water system in response to changes in the temperature and water concentration. Specifically, the viscosity and density of the PAN/water system were measured over the entire water concentration range and over the temperature range from 278.15 to 323.15 K. The molar free Gibbs energy of activation for viscous flow (ΔGm‡,E), entropy (ΔSm‡,E), and entropy (ΔHm‡,E) and their PAN (ΔGm,PAN‡,E, TΔSm,PAN‡,E, ΔHm,PAN‡,E) and water (ΔGm,H2O‡,E, ΔHm,H2O‡,E and TΔSm,H2O‡,E) partial quantities were calculated, and we investigated the validity of the unique interpretation that water might be accommodated in the cavities of the liquid structure of PAN. In the water concentration dependence, TΔSm‡,E and ΔHm‡,E were consistently negative andTΔSm‡,E < ΔHm‡,E. Therefore, the results suggest that PAN forms a more ordered structure when mixed with water even though the attractive intermolecular interaction decreases. However, the increase of ΔHm‡,E and TΔSm‡,E in the temperature range 278–323 K was 2.35 kJ mol−1 and 1.60 kJ mol−1, respectively, indicating that ΔHm‡,E > TΔSm‡,E. That is, the attractive intermolecular interaction increases with increasing temperature, suggesting that the ordered structure changes toward disorder. In addition, at a water mole fraction of 0.1, which was the lowest concentration of water investigated in this study, the partial molar volume of water is 16% lower than that of pure water and both ΔHm,H2O‡,E and TΔSm,H2O‡,E are reduced, suggesting that the attractive interaction of water is weaker in PAN than in bulk water and that the structure of PAN is closer to that of a pure liquid in this concentration range. Water is speculated to be accommodated into the cavities of the PAN structure.

Slow Migration of Brine Inclusions in First-Year Sea Ice

We derive a thermodynamically consistent model for phase change in sea ice by adding salt to the framework introduced by Penrose and Fife. Taking the salt entropy relative to the liquid water molar fraction provides a transparent mechanism for salt rejection under ice formation. We identify slow varying coordinates, including salt density relative to liquid water molarity weighted by latent heat, and use multiscale analysis to derive a quasi-equilibrium Stefan-type problem via a sharp interface scaling. The singular limit is under-determined and the leading order system is closed by imposing local conservation of salt under interface perturbation. The quasi-steady system determines interface motion as balance of curvature, temperature gradient, and salt density. We resolve this numerically for axisymmetric surfaces and show that the thermal gradients typical of arctic sea ice can have a decisive impact on the mode of pinch-off of cylindrical brine inclusions and on the size distribution of the resultant spherical shapes. The density and distribution of inclusion sizes is a key component of sea ice albedo which factors into global climate models.

Performance of Some Novel Mixed Solvents as Entrainers for Separation of Water and Acetonitrile

Performance of some novel mixed solvents as entrainers was tested for acetonitrile dehydration by extractive distillation. The mixed solvents are composed of ethylene glycol (EG) and choline chloride (ChCl) (EG + ChCl 8:1, EG + ChCl 4:1, EG + ChCl 2:1, and EG + ChCl 4:3), ethylene glycol (EG) and glycerol (EG + glycerol 1:1, EG + glycerol 1:2, EG + glycerol 1:4, and EG + glycerol 1:6), and dimethyl sulfoxide (DMSO) and ChCl (DMSO + ChCl 14:1). Isobaric vapor–liquid equilibrium (VLE) data were measured at 101.3 kPa and at a solvent-free acetonitrile mole fraction of 0.95 for the quaternary systems of water + acetonitrile + EG + ChCl, water + acetonitrile + EG + glycerol, and water + acetonitrile + DMSO + ChCl and for the ternary system of water + acetonitrile + DMSO. The NRTL equation was used for the correlation of the experimental VLE data. For all the three quaternary systems and one ternary system, the mean absolute deviations of equilibrium temperature were no more than 0.33 K, and the mean absolute deviations of water and acetonitrile vapor phase mole fractions were no more than 0.0026 and 0.0047, respectively. The mixed solvent EG + ChCl 4:3, which is also a deep eutectic solvent, showed favorable solvent performance. The azeotrope of water + acetonitrile can be removed at a solvent mass fraction of 0.212 or a solvent mole fraction of 0.104. This amount is less than that of EG (0.367 in mass fraction and 0.227 in mole fraction), EG + glycerol 1:6 (0.341 in mass fraction and 0.195 in mole fraction), and DMSO + ChCl 14:1 (0.266 in mass fraction and 0.153 in mole fraction).

Interfacial Composition of Surfactant Aggregates in the Presence of Fragrance: A Chemical Trapping Study.

In recent years, there has been increasing interest in daily-use chemical products providing a pleasant scent. The added fragrance molecules may induce microstructural transitions of surfactant aggregates, which further affect the physical and chemical properties of the products. Here, the effects of four types of aromatic alcohols (cinnamyl alcohol, phenyl ethanol, phenyl methanol and anisyl alcohol) on cetyltrimethylammonium bromide (CTAB)/KBr aggregates were studied. The combined results from rheology, dynamic light scattering, and transmission electron microscopy measurements showed that cinnamyl alcohol induced significant micellar growth, while increases in micellar growth were less obvious for the other aromatic alcohols. The changes in the interfacial molarities of water, aromatic alcohol, and bromide ions during such transitions were studied using the chemical trapping method. Transitions resulting from added cinnamyl alcohol were accompanied by significant declines in interfacial water and bromide ion molarities, and a rise in interfacial alcohol molarity. The marked decrease in interfacial water molarity was not observed in previous studies of the octanol induced formation of wormlike micelles and vesicles, indicating that a different mechanism was presented in the current system. Nuclear magnetic resonance investigation showed that π–π stacking between cinnamyl alcohols, but not cation–π interactions between alcohols and CTAB headgroups, facilitated the tight packing of alcohol molecules in CTAB aggregates and the repulsion of water from the interfacial region. The current study may provide a theoretical basis for the morphological regulation of surfactant aggregates in the presence of additives.

OH Stretching and Libration Bands of Solitary Water in Ionic Liquids and Dipolar Solvents Share a Single Dependence on Solvent Polarity.

Ionic liquids are an emerging class of materials which are finding application in a variety of technologically important areas. Because of their hydrophilic character, at least a small concentration of water is often present when ionic liquids are used in practical applications. This study employs infrared spectroscopy in the OH stretching and libration regions together with DFT calculations to better characterize the state of dilute water in ionic liquids. Water mole fractions (xw ∼ 0.1) are chosen such that nearly all water occurs in monomeric form and spectra probe the solvation structure and dynamics of solitary water molecules. New data are reported for a series of 1-ethyl-3-methylimidazolium liquids [Im21][X] with X- = (C2F5)3F3P-, (CF3SO2)2N-, BF4-, B(CN)4-, CF3SO3-, C2H5SO4-, NO3-, SCN-, and CH3CO2-, as well as for the two 1-hexyl-3-methylimidazolium liquids [Im61][Cl] and [Im61][I]. For comparison, spectra are also recorded in a variety of dipolar solvents, and much of the available literature data are summarized, providing a comprehensive perspective on monomeric water in homogeneous solution. Most prior studies of dilute water in ionic liquids interpreted OH stretching spectra only in terms of water being specifically bonded to two anions in A-···H-O-H···A- type solvates. The more detailed analysis presented here indicates the additional presence of asymmetrically solvated water, which in some cases includes both singly solvated (A-···H-O-H) and more subtle forms of asymmetric solvation. The same pattern of solvation also pertains to dipolar solvents capable of accepting hydrogen bonds from water. No clear distinction is found between OH spectra in high-polarity conventional solvents and ionic liquids. In all solvents, OH frequencies are strongly correlated to measures of solvent basicity or hydrogen bond accepting ability. Far-infrared spectra of the water libration band also show common trends in ionic and dipolar solvents. Despite the different character of the libration and OH modes, the frequencies of these vibrations show virtually the same solvent dependence (apart from sign) except in weakly polar or nonpolar solvents.

Consideration of transmembrane water exchange in pharmacokinetic model significantly improves the accuracy of DCE-MRI in estimating cellular density: A pilot study in glioblastoma multiforme

Transmembrane water exchange (TWE) including transcytolemmal water exchange and transvascular water exchange is involved in many in vivo measurements and makes different contributions to the measuring results. In this study, we focus on the potential influence of TWE on the cell density parameter, intracellular water mole fraction pi, derived by dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) which has been reported as a technique to characterize perfusion and vascularization of tissues, but its accuracy in measuring cell density (or interstitial space) has been questioned. Sixteen patients with glioblastoma multiforme (GBM) were enrolled since GBM shows strong intratumor heterogeneity in both cell density and TWE. All the subjects were collected with DCE-MRI and apparent diffusion coefficient (ADC) map. The latter was considered as a valid surrogate of cell density. Extended Tofts (eTofts) model considering TWE as infinitely large variables and shutter-speed model (SSM) considering TWE as finite ones were used to fit DCE-MRI data. Monte Carlo (MC) and finite difference (FD) methods were used to simulate the influence of TWE on DCE-MRI-derived pi and ADC, respectively. The eTofts model shows a significant overestimation of pi in comparison with SSM in GBM (P < 0.001), which is in accordance with MC simulations, and this overestimation shows dependence on the intra-to-extracellular water exchange rate constant (kio). Significant negative correlations between ADC and SSM-derived pi were found in both voxel-wise analyses (t-test P < 0.001, average r = −0.74) and inter-subject comparisons (r = −0.63, P = 0.009). But no consistent voxel-wise correlations (P > 0.05) and a weaker inter-subject negative correlation (r = −0.56, P = 0.02) were found between ADC and eTofts-derived pi. Further experimental and FD results revealed that kio made a limited contribution to ADC values in the physiological kio range in GBM, supporting ADC as a valid biomarker of cell density. These results suggest that the DCE-MRI pharmacokinetic shutter-speed model could significantly improve its accuracy in cell density estimation because of the considering transmembrane water exchange.

Numerical simulation and analysis of the thermal stresses of a planar solid oxide electrolysis cell

ABSTRACT Hydrogen production using solid oxide electrolysis cells (SOECs) is a highly efficient and low-carbon pathway to generate high purity hydrogen. However, high working temperatures may result in high thermal stress due to a mismatch in the coefficient of thermal expansion (CTE) between components with a nonuniform temperature distribution. Serious stress concentration may lead to structural failure of the SOEC stack. Hence, this work investigated the thermal stress of SOECs through a three-dimensional planar SOEC unit model. A stress analysis method was proposed via a multi-physics coupling model of SOECs using Comsol Multiphysics software. The impacts of voltage, flow direction, water mole fraction, and operating pressure on the thermal stress were evaluated. Numerical results show that the highest maximum principal stress is located in the electrolyte in the SOEC unit. Raising the water mole fraction and the CTE of the electrolyte could reduce the thermal stress if the voltage is below the thermoneutral voltage.

Ion-Specific Effects on Vesicle-to-Micelle Transitions of an Amino Acid Surfactant Probed by Chemical Trapping.

Ion-specific effects widely exist in biological and chemical systems and cannot be explained by classical theories. The complexity of ion-specific effects in protein systems at the molecular level necessitates the use of mimetic models involving smaller molecules, such as amino acids, oligopeptides, and other organic molecules bearing amide bonds. Therefore, it is of theoretical value to determine the effect of additional salts on the aggregation transitions of acyl amino acid surfactants. Herein, the effects of specific tetraalkylammonium ions (TAA+) on sodium lauroyl glycinate (SLG) aggregation were studied by dynamic light scattering (DLS) and transmission electron microscopy. Although previous studies have shown that the kosmotropic TAA+ ions tend to induce micellar growth or micelle-to-vesicle transitions of some anionic surfactants, TAA+ addition in the present study induced partial vesicle-to-micelle transitions in SLG solutions. The chemical trapping (CT) method was employed to estimate changes in the interfacial molarities of water, amide bonds, and carboxylate groups during such transitions. The vesicle-to-micelle transitions were accompanied by a marked rise in interfacial water molarity and a decline in interfacial amide bonds molarity, suggesting that the hydrated TAA+ entered the interfacial region and disrupted hydrogen bonding, thus preventing the SLG monomers from packing tightly. Molecular dynamic simulation was also performed to demonstrate the salt-induced cleavage of amide-amide bonds between SLG headgroups. Furthermore, both CT and DLS results show that the ability of tetraalkylammonium cations to induce such transitions increased with increasing size and hydrophobicity of the cation, which follows the Hofmeister series. The current study offers critical molecular-level evidence for understanding the specific effects of tetraalkylammonium ions on the aggregation transitions of an acyl amino acid surfactant.

Effect of hydrocarbonic pollutants on the stability and soil water repellency intensity: A case study in Bandar Abbas Oil Refinery, Hormozgan province, Iran

Background: The contamination of soil and water with hydrocarbonic pollutants is a major environmental problem. Soil water repellency will interrupt water infiltration, and may decline plant growth and potentially trigger soil erosion. The aim of this study was to investigate the effect of soil and water contamination by oil on soil water repellency, where the soil has been oil-contaminated due to mismanagement of the lands surrounding the refineries, and many of the trees in the area have dried up. Methods: Water drop penetration time test (WDPT) was performed on contaminated soils. To investigate the effect of the surface water contamination on soil, handmade soil samples were collected and successive dry/wet cycles were applied to them by contaminated and non-contaminated waters. Subsequently, soil water repellency tests, including molarity of ethanol droplet (MED), water and ethanol sorptivity were performed on soil samples. The soils were passed through a 2 mm sieve after being air-dried and the soil texture was determined by pipette method. The SWR was measured by WDPT in the area contaminated with petroleum compounds and 7 to 10 replicates were assigned to each location. In order to determine the effect of water contamination on the area soil and to measure water repellency in the laboratory, disturbed soil samples (36 samples) with a bulk density equal to 80% of the reference bulk density were prepared. Results: The results showed that soil oil-contamination causes water repellency, increased WDPT, a significant increase in water repellency index, and a significant decrease in cosθ at the level of 0.001. The effect of water contamination on the indices and cosθ were statistically significant at the 0.001 and 1% levels, respectively. Therefore, contaminated water increased the water repellency of the soil after successive dry/wet cycles. Conclusion: Significant positive correlations between organic and water repellency indices and significant negative correlations between cosθ and organic indices indicate the effect of oil-contamination of water and soil on creating and increasing the intensity of soil water repellency.

Synthesis, Characterization and Biological Activities of New Schiff Base Compound and Its Lanthanide Complexes.

The thermal condensation of 3-(2-Furyl)acrolein with 2-Amino-6-ethoxybenzothiazole generated a new Schiff base, (1E,2E)-N-(6-ethoxybenzo[d]thiazol-2-yl)-3-(furan-2-yl)prop-2-en-1-imine (L), with general formula of C16H14N2O2S. Also, a series of lanthanide complexes of gadolinium, samarium, and neodymium (La–Lc) were synthesized utilizing acetonitrile as the solvent and triethylamine as a buffer and catalyst. Based on elemental analysis, mass spectroscopy, and FTIR analysis, all of the Bis-(1E,2E)-N-(6-ethoxybenzo[d]thiazol-2-yl)-3-(furan-2-yl)prop-2-en-1-iminetri-nitratolanthanide(III) complexes with the general formula [LnL2(NO3)3]·H2O are solids with a 2:1 molar ratio (ligand: metal). Based on conductivity estimates, they are nonelectrolytes and monoatomic paramagnetic according to the magnetic moment measurements, and one mole of lattice water was found after thermal gravimetric measurements and FTIR analysis. Therefore, the lanthanide complexes show a ten-coordination structure with a deformed bicapped square antiprismatic. The Schiff base and its complexes were screened for their antimicrobial, antifungal, antioxidant, and antitumor properties. Their antimicrobial and antifungal activities were strong, and they also produced good antioxidant and antitumor effects.

Kinetics of ethanol steam reforming over Ni/Olivine catalyst

Olivine, a natural mineral consisting of different metal oxides (mainly Mg, Si and Fe oxides) was used as a support for nickel catalyst used in steam reforming of ethanol. Catalyst containing different wt% of Ni on olivine were prepared by conventional wet-impregnation method and characterized by BET, XRD, SEM (coupled with EDS) and H2-TPR. The reaction was carried out in a tubular fixed bed reactor. Among all the catalysts, 5% Ni on olivine catalyst gave highest hydrogen yield as well as ethanol conversion through ethanol steam reforming reaction. The catalyst activity was analyzed by varying three important process parameters (temperature, ethanol to water molar ratio and space-time). The reaction was performed in the temperature range of 450 °C to 550 °C with 1:6 to 1:12 M feed ratio of ethanol to water at a space-time range 7.21–15.87 kg cat h/kmol ethanol. A maximum yield of 4.62 mol of hydrogen per mole of ethanol reacted was obtained at 550 °C with ethanol to steam molar ratio of 1:10 and space-time of 7.94 kg cat h/kmol ethanol with the ethanol conversion level of 97%. CHNS analysis of the spent catalyst was performed to find the coke deposited over the catalyst surface during the reaction. The power law and LHHW type kinetic models were developed. The power law model predicts the activation energy as 29.07 kJ/mol, whereas the LHHW type model gives the activation energy as 27.4 kJ/mol.

THE DIFFERENTIAL THERMAL ANALYSIS OF COMPLEX CATALYTIC SYSTEM OF 50%Cu3(PO4)2•50%Ni3(PO4)2

The catalytic system of 50% Cu3(PO4)2∙50% Ni3(PO4)2 based on Copper (II) and Nickel (II) orthophosphates was synthesized by the coprecipitation method according to the method developed at the Department of Physical and Colloid Chemistry of Uzhhorod National University. The synthesized system was investigated by the method of differential thermal analysis. The obtained results can be interpreted in favor of the formation of a new phase, which is formed due to the equiatomic interaction of the initial components. Thus, a number of thermal effects different from Cu3(PO4)2∙3H2O and Ni3(PO4)2∙8H2O are observed on the corresponding thermogram. The only endothermic effect at 117 ° C is not recorded on the thermograms of the starting components. In the case of a solid solution or a simple mixture of phases based on starting phosphates, this effect should be observed at intermediate temperatures in the range from 129°C to 268°C. Probably, the newly formed phase, by the number of moles of water of crystallization, differs from the original individual orthophosphates. Information about a more accurate number of molecules of chemically bound water in hydrated forms of the synthesized complex copper-nickel phosphate catalyst will allow to establish the results of additional studies by derivatographic or gravimetric analyzes, which were not performed in this work. After dehydration with a further increase in temperature, no endothermic effect for a complex catalytic system is observed. Instead, four exothermic effects are recorded at once: the first two - at 456ºС and 564ºС (both insignificant in area), and the next two at slightly higher temperatures - 658ºС and 777ºС (larger in area). The effects at 564ºC and 658ºC can be attributed to the crystallization of dehydrated Cu3(PO4)2. The exoeffect at 777°C corresponds to the formation of the structure of dehydrated orthophosphate Nickel Ni3(PO4)2. Thus, the obtained experimental data of differential thermal analysis confirm the effective modifying role of Ni2+ ions on the structure, phase formation and a number of physicochemical properties of copper (II) phosphate in the synthesis of a complex oxide catalyst. This made it possible to obtain a new cheap and active complex acid catalyst with improved catalytic properties of 50 % Cu3(PO4)2∙50 % Ni3(PO4)2, which can be used for the process of converting natural gas components into valuable products of the chemical industry.&#x0D; Keywords: differential thermal analysis (DTA); catalysts; сopper (II) orthophosphate; nickel (II) orthophosphate; catalytic 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 system.

Molar and partial molar thermodynamic functions of [BMIm]BF4/water mixture (Gibbs free energy, entropy and enthalpy)

ABSTRACT The viscosity of a 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4)/water mixture has been reported to be less than one-half that of pure [BMIm]BF4 for water mole fraction (χ w) of 0.3, even though the liquid structure of [BMIm]BF4 has been reported to be similar to that of pure [BMIm]BF4 for 0 ≤ χ w ≤ 0.7. To investigate the relationship between the liquid structure and viscosity, the water content dependence of the viscosity is discussed in terms of the molar and partial molar thermodynamic functions calculated from the density and viscosity of the [BMIm]BF4/water mixture. A schematic model is then proposed based on the results. In the water fraction region of 0–0.3, water molecules enter into the liquid structure of [BMIm]BF4. Water molecules do not interact strongly with [BMIm]BF4 and have much higher mobility than [BMIm]BF4; therefore, it is expected that the water molecules enhance the fluidity of [BMIm]BF4 as a lubricant.

Properties of binary mixtures of a novel natural deep eutectic solvent (glycolic acid + xylitol) and water at several temperatures

The density, viscosity, and conductivity of the binary mixture composed of (glycolic acid + xylitol)(3:1) NaDES and water were measured at atmospheric pressure and different temperatures T = (303.15 K, 313.15 K, 323.15 K, 333.15 K, 343.15 K). The density and viscosity values decrease with increasing temperature, while the conductivity values increase over the entire concentration range. The binary system's excess molar volumes (VE) and viscosity deviations (Δη) were calculated and fitted by the fourth-order Kister equation based on the experimental data. With the increase of the water mole fraction, the conductivity values of the system first increase gradually and then decrease dramatically, and the conductivity reaches the highest when the water mole fraction is 0.9548. In addition, the structures of the binary system were characterized by infrared spectra and optimized by quantum chemical simulation. At the molecular level, the amounts and types of hydrogen bonds in the binary system increase by adding water. It is speculated that hydrogen bonding may affect the excess properties of the system.