Temperature Dependence Of Vapor Pressure Research Articles

Phase Transition Thermodynamics of 1,3,5-Tris-(α-naphthyl)benzene: Theory and Experiment.

1,3,5-Tris-(α-naphthyl)benzene is an organic non-electrolyte with notable stability of an amorphous phase. Its glassy and supercooled liquid states were previously studied by spectroscopic and calorimetric methods. Despite the continuing interest in its amorphous state and, particularly, vapor-deposited glasses, the thermodynamic parameters of the vaporization of 1,3,5-tris-(α-naphthyl)benzene have not been obtained yet. Likewise, the reliable evaluation of the thermodynamic parameters of fusion below the melting point, required to establish the thermodynamic state of its glass, is still an unsolved problem. In this work, the heat capacities of crystalline and liquid phases, the temperature dependence of the saturated vapor pressures, fusion and vaporization enthalpies were determined using differential and fast scanning calorimetry and were verified using the estimates based on solution calorimetry. The structural features of 1,3,5-tris-(α-naphthyl)benzene are discussed based on the computations performed and the data on the molecular refractivity. The consistency between the values obtained by independent techniques was demonstrated.

Gas-to-Particle Partitioning of Products from Ozonolysis of Δ3-Carene and the Effect of Temperature and Relative Humidity.

Formation of oxidized products from Δ3-carene (C10H16) ozonolysis and their gas-to-particle partitioning at three temperatures (0, 10, and 20 °C) under dry conditions (<2% RH) and also at 10 °C under humid (78% RH) conditions were studied using a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) combined with a filter inlet for gases and aerosols (FIGAERO). The Δ3-carene ozonolysis products detected by the FIGAERO-ToF-CIMS were dominated by semivolatile organic compounds (SVOCs). The main effect of increasing temperature or RH on the product distribution was an increase in fragmentation of monomer compounds (from C10 to C7 compounds), potentially via alkoxy scission losing a C3 group. The equilibrium partitioning coefficient estimated according to equilibrium partitioning theory shows that the measured SVOC products distribute more into the SOA phase as the temperature decreases from 20 to 10 and 0 °C and for most products as the RH increases from <2 to 78%. The temperature dependency of the saturation vapor pressure (above an assumed liquid state), derived from the partitioning method, also allows for a direct way to obtain enthalpy of vaporization for the detected species without accessibility of authentic standards of the pure substances. This method can provide physical properties, beneficial for, e.g., atmospheric modeling, of complex multifunctional oxidation products.

Thermodynamic properties of indoline and benzoxazine based spiropyrans studied by Knudsen effusion mass spectrometry

An approach including thermal analysis and Knudsen effusion mass spectrometry was used to investigate the thermal stability range and the thermodynamic properties of sublimation for four indoline and benzoxazine based spiropyrans: 1,3,3-trimethyl-6′- (tert-butyl) −8′-formyl-spiro [indoline-2,2′-2H-chromene] (1), 1,3,3,8′-tetramethyl-6′-formyl-spiro [indoline-2,2′-2H-chromene] (4), 1,3,3-trimethyl-8′-methoxy-6′-formyl-spiro [indoline-2,2′-2H-chromene] (7), and 3-methyl-6′-methoxy-8′-formyl-spiro [1,3-benzoxazin-4-one-2,2′-2H-chromene] (9). The melting and decomposition temperatures as well as the melting enthalpies were obtained by thermal analysis. The electron ionization mass spectra as well as the ionization efficiency curves were measured. Schemes of the formation of the main ions in the mass spectra were suggested. The temperature dependencies of vapor pressures were used to obtain the sublimation enthalpies. All data were obtained for the first time.

Synthesis, crystal structure, thermal properties of a homoleptic Schiff base cobalt complex bis(N-tert-pentyl salicylaldimine)cobalt(II) as precursor for coating Co3O4 thin film by a plasma enhanced MOCVD

A Schiff base complex of cobalt namely, bis(N-tert-pentyl-salicylaldimine)cobalt(II) (2) was synthesized by treating the parent complex, bis(salicylaldehydato)cobalt(II) (1) with n-tert-pentylamine in a methanolic medium. Complex 2 was analysed by dynamic TG/DTA using high purity Ar as purge gas at ambient pressure and was found to be volatile without undergoing decomposition leaving a negligible amount of (1.8 %) residue at 322 °C after melting sharply at 155 °C. The parent complex (1) wherein four oxygen atoms are coordinated to cobalt yielded a residue of 58 % at 400 °C. The dissimilarity in thermal property of 2 (CoN2O2) from that of 1 (CoO2O2) arises from the bonding of nitrogen atoms to cobalt by introducing n-tert-pentylamine which caused replacement of aldehyde O (–CH = O) with azomethine nitrogen (–CH = N). Single crystal XRD analysis of complex 2 revealed it to crystallise in orthorhombic crystal system with a space group of P212121. Further 2 was characterised by FTIR, elemental analysis and mass spectrometry. Transpiration TG technique was employed to evaluate the temperature dependence of saturated vapour pressure (pe) and enthalpy of vaporization (ΔvapH° = 102.3 ± 2.5 kJ mol−1) for 2 in the temperature range of 443–545 K. Complex 2 was transformed in to Co3O4 thin film at 350 °C in an Ar plasma by using a lab made plasma assisted chemical vapour deposition (CVD) process at 1.2 mbar deposition pressure. XRD revealed a preferential growth of cubic Co3O4 in the (311) plane. The SEM images confirmed a dense but scattered growth of cauliflower shaped structures. The particle size was found to be 19.3 nm. Kubelka-Munk function yielded a band gap of 2.01 eV.

Method for Obtaining Isothermal Diagrams of the Liquid - Vapor Equilibrium for the System as Dimethyl Zinc - Dimethyl Telluride

According to the obtained experimental temperature dependences of the saturated vapor pressure on dimethylzinc – dimethyltelluride solutions with dimethylzinc content of 50.0 and 70.32 mol. %, isothermal sections (280, 290, 300, 310, and 320 K) were made. For the dimethylzinc – dimethyltelluride system based on a limited set of experimental data for the “liquid-vapor” equilibrium, the vapor composition was calculated according to the Duhem – Margules equation, as well as the partial pressures and the distribution coefficient.

1,4-Bis(trimethylsilyl)piperazine—Thermal Properties and Application as CVD Precursor

We report an investigation into 1,4-Bis-N,N-(trimethylsilyl)piperazine (BTMSP) as a novel precursor for the synthesis of silicon carbonitride films by chemical vapor deposition (CVD). The thermal stability, temperature dependence of vapor pressure and thermodynamic constants of the evaporation process of BTMSP were determined by static tensimetry with a glass membrane zero manometer. The transformation of the compound in low-power (25 W) plasma conditions was investigated by optical emission spectroscopy. It was shown that BTMSP undergoes destruction, accompanied by H and CH elimination and CN formation. SiCN(H) films were deposited in a hot-wall plasma-enhanced CVD reactor. The optical properties of the films were studied by spectral ellipsometry (refractive index: 1.5–2.2; absorption coefficient: 0–0.12) and UV–Vis spectroscopy (transmittance: up to 95%; optical bandgap: 1.6–4.9 eV). Information on the aging behavior of the films is also provided. The transformation of the films occurred through water adsorption and the formation of Si–O bonds with the degradation of Si–H, N–H and Si–CHx–Si bonds.

Thermodynamic properties of 2-methyl-5-phenylfuran-3-carboxylic

The temperature dependence of the saturated vapor pressure and the combustion energy of 2-methyl-5-phenylfuran-3-carboxylic acid were determined by experimental methods. Based on the obtained data, the values of the enthalpies of combustion and formation in the condensed state were calculated. The enthalpy of sublimation was recalculated to 298K. The additive Benson scheme is supplemented with new fragments for calculating the enthalpies of formation in the gaseous state. The possibility of using the Joback method to calculate the enthalpies of formation of aryl furans in the gaseous state is analyzed.

Temperature Dependence of Water Crossover in Proton Exchange Membrane Water Electrolysis

In this work, we investigated the temperature dependence on the water transport coefficient for proton exchange membrane water electrolysis (PEMWE). The experimental parameters varied between 40 and 80 °C at a current density of 1 A cm-2 geo and ambient pressure. The water crossover to the cathode was measured by cooling the exhaust and weighing the liquid fraction over 4 hours under steady conditions. The remaining water vapor from the gaseous fraction was taken into account by the temperature-dependent vapor pressure curve. The resulting data of the water crossover [mg cm-2 geo min-1] depends on the temperature, time and current density applied. The main driving force of the water crossover is the proton flux through the membrane and can be established by fitting the data of the relative changes in water mass over time with a linear function. For now, the water diffusion which has a minor contribution is not considered. Our results reveal that the water transport coefficient derived from the proton flux increases from 2.4 at 40 °C to 3.1 at 80 °C (growth of +29%). In summary, we have developed a method to more accurately determine the water transport coefficient, which is very useful in modeling the water crossover in PEMWE.

Mass spectrometric study and modeling of the thermodynamic properties of SrO-Al2 O3 melts at high temperatures.

The SrO-Al2 O3 system holds promise as a base for a wide spectrum of advanced materials, which may be synthesized or applied at high temperatures. Therefore, studying vaporization and high-temperature thermodynamic properties of this system is of great practical importance. Samples of the SrO-Al2 O3 system were obtained by solid-state synthesis and identified by X-ray fluorescence analysis, X-ray phase analysis, scanning electron microscopy, electron probe microanalysis, simultaneous thermal analysis, and thermogravimetric analysis. The thermodynamic properties of the SrO-Al2 O3 system were studied by the Knudsen effusion mass spectrometric (KEMS) method and were fitted by the Redlich-Kister and Wilson polynomials. The thermodynamic values obtained were also optimized within the generalized lattice theory of associated solutions (GLTAS). The vapor composition, temperature, and concentration dependences of the partial vapor pressures over the samples under study as well as the SrO activities in melts of the SrO-Al2 O3 system were determined by the KEMS method. Usage of the Redlich-Kister and Wilson polynomials allowed calculation of the excess Gibbs energies, enthalpies of mixing, and excess entropies in the concentration range 0-33 mol% of SrO at temperatures of 2450 and 2550 K. Significant negative deviations from the ideality were observed in the melts of the SrO-Al2 O3 system at 2450, 2550, and 2650 K. The Wilson polynomial was found to be the optimal approach to describe the thermodynamic properties in the system studied. Optimization of the experimental data using the GLTAS approach allowed the characteristic features of the thermodynamic description of the SrO-Al2 O3 system to be elucidated and explained.

Nearest-Neighbour and Non-Nearest-Neighbour Non-Covalent Interactions between Substituents in the Aromatic Systems: Experimental and Theoretical Investigation of Functionally Substituted Benzophenones

Benzophenone derivatives exhibit not only biological activity but also act as photo initiator and UV blocker. We carried out experimental and theoretical thermochemical studies of hydroxy- and methoxy-substituted benzophenones. Standard molar enthalpies of vaporisation were obtained from the temperature dependence of vapour pressures measured by the transpiration method. The thermodynamic data on phase transitions available in the literature (crystal-gas, crystal-liquid, and liquid-gas) were also collected and evaluated. High-level quantum chemical methods G3MP2 and G4 were used to estimate the standard molar enthalpies of formation of substituted benzophenones in the gas phase and establish agreement between experimental and theoretical results. The application of the "centrepiece" group-contribution approach to hydroxy- and methoxy-substituted benzophenones was demonstrated. A quantitative assessment of the hydrogen bond was carried out using various approaches based on experimental data and quantum chemical calculations.

Global Changes in Water Vapor 1979–2020

AbstractGlobal‐scale changes in water vapor and responses to surface temperature variability since 1979 are evaluated across a range of satellite and ground‐based observations, a reanalysis (ERA5) and coupled and atmosphere‐only CMIP6 climate model simulations. Global‐mean column integrated water vapor increased by 1%/decade during 1988–2014 in observations and atmosphere‐only simulations. However, coupled simulations overestimate water vapor trends and this is partly explained by past studies showing that internal climate variability suppressed observed warming in this period. Decreases in low‐altitude tropical water vapor in ERA5 and ground‐based observations before around 1993 are considered suspect based on inconsistency with simulations and increased column integrated water vapor in microwave satellite data since 1979. Atmospheric Infra‐red Sounder satellite data does not capture the increased tropospheric water vapor since 2002 shown by other satellite, reanalysis, and model products. However, global water vapor responses to interannual surface temperature variability are consistent across data sets with increases of ∼4%–5% near the surface and 10%–15% at 300 hPa for each 1°C increase in global surface temperature. Global water vapor responses are explained by thermodynamic amplification of upper tropospheric temperature changes and the Clausius Clapeyron temperature dependence of saturation vapor pressure that are dominated by the tropical ocean responses. Upper tropospheric moistening is larger in climate model simulations with greater upper tropospheric warming.

Thermochemistry of substituted benzenes: acetophenones with methyl, ethyl, cyano and acetoxy substituents

The enthalpies of vaporization/sublimation of 2-, 3- and 4-methyl-acetophenones and 2-, 3-, 4-cyano-acetophenones were derived from the vapor pressure temperature dependence measured with help of the gas saturation method. Enthalpies of fusion of 4-methyl-acetophenone and 2-, 3- and 4-cyano-acetophenone were measured by using DSC. The literature thermochemical data for methyl-, ethyl, cyano- and acetoxy-substituted acetophenones and new results were evaluated using structure–property correlations. The G* quantum chemical methods were validated for reliable estimation of the enthalpies of formation of substituted acetophenones in the gaseous state. The evaluated thermodynamic data were used to design the “centerpiece” method for the assessment of enthalpies of formation and enthalpies of vaporization of substituted benzenes.Graphical abstract

Atomistic simulation framework for molten salt vapor-liquid equilibrium prediction and its application to NaCl.

Knowledge of the vapor-liquid equilibrium (VLE) properties of molten salts is important in the design of thermal energy storage systems for solar power and nuclear energy production applications. The high temperatures involved make their experimental determination problematic, and the development of both macroscopic thermodynamic correlations and predictive molecular-based methodologies are complicated by the requirement to appropriately incorporate the chemically reacting vapor-phase species. We derive a general thermodynamic-based atomistic simulation framework for molten salt VLE prediction and show its application to NaCl. Its input quantities are temperature-dependent ideal-gas free energy data for the vapor phase reactions and density and residual chemical potential data for the liquid. If these are not available experimentally, the former may be predicted using standard electronic structure software, and the latter may be predicted by means of classical atomistic simulation methodology. The framework predicts the temperature dependence of vapor pressure, coexisting phase densities, vapor phase composition, and vaporization enthalpy. It also predicts the concentrations of vapor phase species present in minor amounts (such as the free ions), quantities that are extremely difficult to measure experimentally. We furthermore use the results to obtain an approximation to the complete VLE binodal dome and the critical properties. We verify the framework for molten NaCl, for which experimentally based density and chemical potential data are available in the literature. We then apply it to the analysis of NaCl simulation data for two commonly used atomistic force fields. The framework can be readily extended to molten salt mixtures and to ionic liquids.

Aprotic Ionic Liquids: A Framework for Predicting Vaporization Thermodynamics.

Ionic liquids (ILs) are recognized as an environmentally friendly alternative to replacing volatile molecular solvents. Knowledge of vaporization thermodynamics is crucial for practical applications. The vaporization thermodynamics of five ionic liquids containing a pyridinium cation and the [NTf2] anion were studied using a quartz crystal microbalance. Vapor pressure-temperature dependences were used to derive the enthalpies of vaporization of these ionic liquids. Vaporization enthalpies of the pyridinium-based ionic liquids available in the literature were collected and uniformly adjusted to the reference temperature T = 298.15 K. The consistent sets of evaluated vaporization enthalpies were used to develop the “centerpiece”-based group-additivity method for predicting enthalpies of vaporization of ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquids was established. A small, but not negligible correction term was supposed to reconcile the estimated results with the experiment. The corrected “centerpiece” approach was recommended to predict the vaporization enthalpies of ILs.

Thermal Behavior and Photovoltaic Application of NiII and CoIII Complexes with Substituted o‐Iminobenzoquinone Ligands

AbstractThe thermal properties and an opportunity for photovoltaic applications were studied for a series of transition metal complexes derived on functionalized o‐aminophenols ‐ mixed‐valent CoIII compounds and bis‐o‐iminobenzosemiquinonato NiII complexes. TGA and DSC explored the thermal behavior of compounds in the solid state. EI‐MS established the vapor phase composition. The temperature dependences of a saturated vapor pressure were measured by the Knudsen effusion method with the weight registration of the sublimated substance. Based on the volatility study data, the thermodynamic parameters of a sublimation process were calculated. A high absorptivity distinguishes metal complexes under investigation at visible and NIR regions (i. e., vis/NIR dyes) and, thus, were tested as photosensitizers in the fabricated dye‐sensitized solar cells. The photoelectric conversion efficiency (PCE) was estimated for devices with the NiII derivatives. The CoIII complexes demonstrated the absence of photovoltaic potential.

Reversible storage and release of hydrogen with LOHC: Evaluation of thermochemical data for methyl-quinolines with complementary experimental and computational methods

The liquid organic hydrogen carriers (LOHC) are aromatic molecules, which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen can be loaded and unloaded with a reversible chemical reaction. Methyl-substituted quinolines are available from petroleum, coal processing, wood preservation or they can be synthesized from aniline. Quinolines can be considered as potential LOHC systems, provided they have favorable thermodynamic properties, which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of methyl-quinolines were derived from the vapor pressure temperature dependences. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected, evaluated, and combined with own experimental results. The theoretical standard molar gas-phase enthalpies of formation of methyl-quinolines, calculated using the quantum chemical G3MP2 and G4 methods, agreed well with the evaluated experimental data. The hydrogenation/dehydrogenation reaction enthalpies of methyl-quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC systems.

The comprehensive study of thermal properties of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) related to the chemical vapor deposition of Co-oxide based thin film materials

Using a flow technique, the temperature dependences of saturated vapor pressure of two crystalline modifications of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) – Co(thd)3: stable (P‾3c1) and metastable (Pnma) have been firstly determined. The temperature dependences of saturated vapor pressure of two crystalline modifications of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) – Co(thd)3: stable (P‾3c1) and metastable (Pnma) have been firstly determined using a flow technique. The onset temperatures of thermolysis and decomposition ways of Co(thd)3 vapors in vacuum and in the oxygen and hydrogen presence were established by a means of in situ mass spectrometry. The Co-oxide based materials were obtained via deposition of metastable phase of Co(thd)3 by Pulse-CVD on Si(100) substrates. The composition and microstructure of Co-oxide based materials depending on deposition temperature and career gas was studied by using X-ray diffraction, X-ray photoelectron, Raman spectroscopy and SEM. The (111)-oriented Co3O4 film demonstrates electrochemical stability in 1 M NaOH solution and it has 0.63 V potential which is reached at 10 mA/cm2.

Sublimation Study of Six 5-Substituted-1,10-Phenanthrolines by Knudsen Effusion Mass Loss and Solution Calorimetry.

The vapor pressures of six solid 5-X-1,10-phenanthrolines (where X = Cl, CH3, CN, OCH3, NH2, NO2) were determined in suitable temperature ranges by Knudsen Effusion Mass Loss (KEML). From the temperature dependencies of vapor pressure, the molar sublimation enthalpies, ΔcrgHm0(⟨T⟩), were calculated at the corresponding average ⟨T⟩ of the explored temperature ranges. Since to the best of our knowledge no thermochemical data seem to be available in the literature regarding these compounds, the ΔcrgHm0(⟨T⟩) values obtained by KEML experiments were adjusted to 298.15 K using a well known empirical procedure reported in the literature. The standard (p0 = 0.1 MPa) molar sublimation enthalpies, ΔcrgHm0(298.15 K), were compared with those determined using a recently proposed solution calorimetry approach, which was validated using a remarkable amount of thermochemical data of molecular compounds. For this purpose, solution enthalpies at infinite dilution of the studied 5-chloro and 5-methylphenantrolines in benzene were measured at 298.15 K. Good agreement was found between the values derived by the two different approaches, and final mean values of ΔcrgHm0(298.15 K) were recommended. Finally, the standard molar entropies and Gibbs energies of sublimation were also derived at T = 298.15 K. The volatilities of the six compounds were found to vary over a range of three orders of magnitude in the explored temperature range. The large difference in volatility was analyzed in the light of enthalpies and entropies of sublimation. The latter was tentatively put in relation to the rotational contribution of the substituent group on the phenanthroline unit.

Molecular versus ionic liquids: Development of a thermodynamic framework for predicting vaporization thermodynamics

Ionic liquids based on the pyridinium and quinolinium cations show good result in desulfurization of fuels. The knowledge of their vaporisation thermodynamics is of practical importance. The standard molar enthalpies of vaporization of pyridinium based ionic liquids were derived from the vapor pressure temperature dependences measured by the quartz-crystal microbalance method. We have collected available primary experimental results on vapour pressures, and enthalpies of phase transitions (solid-solid, crystal-gas, and liquid-gas) of analogous molecular species – substituted pyridines and quinolines. These data were evaluated using the structure-property correlations. The consistent sets of evaluated thermodynamic data on the molecular and ionic liquids were used to develop the “centerpiece” based group-additivity method for predicting enthalpies of vaporization of molecular and ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquid has been established.

Температурные зависимости давления насыщенного пара комплексов олова(IV) с полидентатными лигандами

The present paper is a continuation of the previously pursued studies of thermal properties of the Sn(IV) complexes with tridentate iminopyridine ligands. The study of thermal properties including temperature dependences of the saturated vapor pressure for Sn(IV) complexes with the tridentate iminopyridine ligands by differential scanning calorimetry (DSC) and the Knudsen effusion method leads to the use of the studied compounds as luminescent materials, as well as components for nonlinear optics. Coordination compounds of tin (IV) containing tridentate Schiff bases were chosen as objects of research: 2,4-di-tert-butyl-6-((phenyl (pyridin-2-yl)methylene)amino)phenolatotrichlorotin(IV) (1), 4-methyl-2-((phenyl (pyridin-2-yl)methylene)amino)phenolatotrichlorotin(IV) (2), 4-chloro-2-((phenyl (pyridin-2-yl)methylene)amino) phenolatotrichlorotin(IV) (3). These compounds were obtained by tem-plate synthesis from tin tetrachloride, various o-aminophenols, and α-carbonyl substituted pyri-dines; they contain an iminopyridine function and are capable of covalently binding to a metal by a phenolic group. Phase transitions of compounds 1–3 were studied by DSC in the temperature range 25–500 °C. For all studied complexes an endothermic transition correlated to melting was revealed. The melting points of the studied compounds were taken to be the temperature values corresponding to the onset of the transition, according to the standard Netzsch Software Proteus method: 300, 320 and 330 °C for 1–3, respectively. The temperature dependences of the saturated vapor pressure were obtained for the studied complexes, using the Knudsen effusion method with the weight recording of the amounts of sublimated substances. As a result of the experiments it was found that compounds 1–3 sublimated in the temperature ranges of 239–244, 228–260 and 226–256 °C, respectively. Thermodynamic parameters of sublimation processes were calculated.