Henry's Constants Research Articles

On the Informativity of Higher-Order Moments in Chromatography

Analytical solutions have been obtained for ordinary, normalized, and higher-order (third- and fourth-order) central moments using the model of an equilibrium adsorption layer. The solutions are represented by one-term fractions and comprise the length of an adsorbent layer, the velocity of a mobile phase, the effective kinetic constant, and the Henry constant. Expressions for the third- and fourth-order moments have been obtained and analyzed in the case of the rectangular input signal . It has been shown that, when solving the inverse problem of chromatography, the calculation of the higher-order moments provides no new information on the kinetic or any other properties of an adsorbent layer.

Self-Consistent Calculation of the Rates of Dissociative Adsorption and Desorption with the Adsorption Isotherm on the Rough Surface of an Adsorbent

The fulfillment of the self-consistency condition in the description of adsorption and desorption the rates of dissociating vapor molecules on the rough surface of an adsorbent (equilibrium and tempered from an equilibrium state) is considered. The adsorption process causes the reconstruction of the equilibrium near-surface region of the adsorbent, but does not change the state of the tempered surface. The adsorption–desorption rates are calculated taking into account the interaction of the nearest neighbors in the quasi-chemical approximation. Four models are considered for the description of a nonuniform surface: the initial averaged multilayer model with different types of adsorption sites (and Henry constants), a model containing all the sites available for adsorption, and three types of its averaging. The first type of averaging is associated with the transition to a single-layer nonuniform surface containing different types of adsorption sites with different Henry constants, the second is associated with the transition to a set of effective uniform monolayers in the multilayer transition region, and the third is associated with the transition to a single-layer effective uniform surface. The condition of self-consistency is fulfilled in the last two types of averaging and is violated in the first type of averaging, as well as in the averaged model taking into account the differences between the types of sites. It is found that the state of a nonuniform surface (equilibrium or tempered) does not affect the self-consistency of the description of the rates of adsorption and desorption in the latter two types of models. The influence of taking into account the effects of correlation of the interaction of species on the condition of self-consistency is shown. The neglect of the effects of correlation of interacting species leads to the violation of the self-consistency condition in all models.

Thermodynamic and Kinetic Parameters of the Solubility of Ozone in Water

The solubility and decomposition kinetics of ozone in pure water at different temperatures were studied. The Henry constant of ozone, kinetic order, and decomposition rate constant were determined. It was shown that to determine the concentration of dissolved ozone, it is sufficient to use the Henry law [O3] = $${{H}_{{{{{\text{O}}}_{{\text{3}}}}}}}$$ C(O3), where [O3] and C(O3) are the ozone concentrations in solution and gas phase (M), respectively; and the Henry constant is determined by the equality ln $${{H}_{{{{{\text{O}}}_{{\text{3}}}}}}}$$ = –(9.445 ± 1.00) + (2406 ± 300)/T (in the range 20–40°С). The dependence of the solubility on the kinetic characteristics of ozone decomposition and mass transfer, water purity, and reactor characteristics was discussed.

Correlation and prediction of thermodynamic properties of dilute solutes in water up to high T and P. I. Simple fluids He, Ne, Ar, Kr, Xe, Rn, H2, N2, O2, CO, CH4

Fugacity coefficients of dilute aqueous solutions of six noble gases and five simple fluids have been correlated from ambient conditions (298 K, 0.1 MPa) to high temperatures (up to 2000 K) and water densities as high as 1500 kg m−3. A correlation is developed for the function, A12∞=V2∞/κTRT, that includes known constraints: second virial coefficients at low-water densities, rigid-body behavior at high-water densities, near-critical principles, and corresponding-states relations. Reasonable agreement with an extensive, evaluated database of volumetric and solubility measurements has been achieved over the entire range of conditions, though comparisons of calculated with recommended Henry's constants suggest reconsiderations of recommendations for He and CO at temperatures above 550 K.

Impact of dealcoholization on quality properties in white wine at various alcohol content levels.

The reduction of alcohol content in wines has two main objectives, the former is decreasing the wines' strength and the latter is producing new low alcohol beverages. To accomplish the latter, in this study, we focused on the dealcoholization of a white wine (cv Falanghina, 12.5vol%) obtained from an ancient Italian grape variety that has recently aroused a renewed interest. It was dealcoholized at various alcohol content levels ranging from 9.8 to 0.3vol% through the osmotic distillation process, and the main quality parameters of the obtained dealcoholized samples were evaluated. No significant differences (p < 0.05) in total phenols, flavonoids, organic acids and total acidity were observed among the wine samples at different alcohol content levels. On the contrary, the volatile compounds content decreased with increasing alcohol removal. Specifically, almost 50% of higher alcohols with acids and lactones were preserved in dealcoholized wine at 9.8vol% alcohol content, but this percentage reduced to 30% in the sample at 6.8vol%, and was even lower in the dealcoholized wine with lower alcohol content. It was argued that the transport of volatile compounds through the membrane, beside the membrane selectivity, is highly correlated with the Henry constant (R2 > 0.8021 for 9.8vol% of dealcoholized wine). Moreover, results of the sensory evaluation indicated a significant change in terms of acidity, odour, sweetness and body taste in dealcoholized wine (0.3vol%), giving an overall perceived imbalance and unacceptable taste with respect to the original wine. Therefore, in order to balance acid sensation and enhance body and aftertaste, an attempt was made to formulate an alcohol-free wine-based beverage with enhanced odour and sweetness, by adding some floral wine flavours, up to the amount present in the original wine.

Solubility and mass transfer of H2, CH4, and their mixtures in vacuum gas oil: An experimental and modeling study

Abstract In this work, the solubility data and liquid-phase mass transfer coefficients of hydrogen (H2), methane (CH4) and their mixtures in vacuum gas oil (VGO) at temperatures (353.15–453.15 K) and pressures (1–7 MPa) were measured, which are necessary for catalytic cracking process simulation and design. The solubility of H2 and CH4 in VGO increases with the increase of pressure, but decreases with the increase of temperature. Henry's constants of H2 and CH4 follow the relation of ln H = − 413.05/T + 5.27 and ln H = − 990.67/T + 5.87, respectively. The molar fractions of H2 and system pressures at different equilibrium time were measured to estimate the liquid-phase mass transfer coefficients. The results showed that with the increase of pressure, the liquid-phase mass transfer coefficients increase. Furthermore, the solubility of H2 and CH4 in VGO was predicted by the predictive COSMO-RS model, and the predicted values agree well with experimental data. In addition, the gas–liquid equilibrium (GLE) for H2 + CH4 + VGO system at different feeding gas ratios in volume fraction (i.e., H2 85% + CH4 15% and H2 90% + CH4 10%) was measured. The selectivity of H2 to CH4 predicted by the COSMO-RS model agrees well with experimental data. This work provides the basic thermodynamic and dynamic data for fuel oil catalytic cracking processes.

Physicochemical properties of styrene oligomers in the environment

Currently, styrene oligomers (SOs) are persistent contaminants that are present in the environment globally. SOs are artificial substances originating from styrene-based polymer materials, mainly including PS plastic, resin, and rubber. However, the behavior of SOs in the environment is not well-understood yet due to the scarcity of experimental data. The objective of this study was to use in-silico tool to estimate key physicochemical properties of these SOs. The US EPA EPI suite program was used to predict SOs' physicochemical properties including solubility, vapor pressure, LogKow, Henry's constant, LogKoc, and fugacity-based multimedia mass balance. Although styrene monomer (SM) and SOs have structural similarity, the physicochemical properties of SOs are significantly different from those of SM, a precursor of SOs. In particular, it is estimated that as much as the heavy molecular weight, most SOs persist for comparable periods of time in a sandy environment. Although there is uncertainty, this preliminary in-silico study provides a sufficient reason to assure an experimental study to better determine properties of SOs.

A role of the microtextural and surface chemical heterogeneities of porous carbons for the adsorption of CO2, CO and N2

Microtextural and surface chemical heterogeneities of activated carbons (AC) have been studied to see their distinctive role for the adsorption of CO2, CO and N2 at 25 °C and up to 850 Torr. Not only the microtextural properties influence the adsorption of the gases, particularly CO2, but the chemical surface heterogeneity also plays a significant role for CO2 adsorption. The volume of ultramicropores < 7 A is of predominantly importance in high CO2 adsorption at pressures above 30 Torr. However, the average size of micropores and their size distribution, and the chemical surface heterogeneity are much more critical at the Henry’s law region (< 30 Torr). The latter could be well characterized by the amount and Henry constant of CO2 adsorption at the low pressures, the Toth model parameters, the change in CO2/CO and CO2/N2 selectivities with respect to pressure, the amount of CO from the thermal decomposition, and the direct probing of very strong basicity sites using a technique that is the temperature-programmed desorption of CO2 adsorbed. All of them are consistent with the difference in the energetic nonuniformity between ACs studied, except for the last measure whose results could be reasonably explained when combining with the microtextural heterogeneity.

Geometrical investigation and classification of three-suffix margules binary mixtures including single and double azeotropy

The present study investigates the sub-critical behavior of binary fluid mixtures that follow the three-suffix Margules model for the excess Gibbs free energy. It is a systematic and geometric treatment of these binary mixtures that allows a global view of the conditions leading to zeotropy, single azeotropy, and double azeotropy, and provides additional criteria for the mixture classification of Shulgin et al. (Ind. Eng. Chem. Res. 40 (2001) 2742–2747). These conditions are delimited on the Ac-Bc plane, where Ac and Bc are variables determined solely by Henry's constants and pure components' saturation pressures. Based on these mixture properties the azeotropic composition, excess Gibbs free energy shape and criteria for the liquid phase splitting are given, for fluid mixtures obeying Margules model. The study proceeds by mapping real mixture behavior as temperature changes. With varying temperature, the mixture traces a path that crosses regions of different mixture types. Special mention is made on mapping the behavior of mixtures crossing the Bancroft point. The study concludes comparing Margules' model to van Laar's. It is proved that the latter cannot predict double azeotropy.

Critical Conditions of Adhesion and Separation of Functionalized Nanoparticles on Polymer Grafted Substrates

Emerging technologies of production and processing of functionalized nanoparticles (NP) require advanced methods of NP characterization and separation. While various methods are available for NP separation by size, there are no efficient methods for NP separation by surface chemistry. Using extensive dissipative particle dynamics simulations, this work investigates the mechanisms of NP adhesion and flow in polymer brush (PB)-grafted pore channels searching for the conditions for size-independent separation of NPs that are similar to the critical conditions of liquid chromatography of polymers. We consider interactions of NPs functionalized by hydrophilic and hydrophobic ligands with PBs, in which conformation and adhesion properties are controlled by the solvent quality varied with the composition of thermodynamically good and poor solvent components. The NP-PB adhesion is characterized by the free energy landscape calculated by the ghost tweezers simulation method that mimics the experimental technique of optical tweezers. The NP Henry constant and the respective partition coefficient are calculated depending on the NP size and ligand composition at varying solvent quality. Our findings demonstrate that, with the decrease of solvent quality, the NP elution undergoes a transition from the size-exclusion mode with larger NPs having shorter retention time to the adsorption mode with the reverse order of elution. This transition, which occurs in a narrow range of solvent composition, signifies the so-called “critical” point of adsorption that strongly depends on the NP functionalization. The dynamics of NP axial dispersion in the isocratic and gradient elution modes is characterized employing a convective-diffusion model. We show that the NPs can be effectively separated by surface chemistry at the critical points of adsorption, using the gradient mode of interaction NP chromatography with controlled variation of the solvent composition.

Self-Consistency in Calculating the Rates of Adsorption and Desorption and an Isotherm of Adsorption on a Rough Surface of Aerosols

Ways of satisfying the condition for the self-consistent description of adsorption and desorption rates of non-dissociated molecules on a rough aerosol surface are considered. The rates are calculated with allowance for the interaction between nearest neighbors in the quasi-chemical approximation. Four types of models are analyzed. One describes the initial distributed heterogeneous surface, while the other three are variants averaged over the number of monolayers (with a transition to a single-layered heterogeneous surface) and different types of adsorption centers with different Henry constants (with a transition to an effective homogeneous monolayer in a multilayered transition region), or over the number of monolayers and types of adsorption centers (with a transition to the single-layered homogeneous surface) simultaneously. Types of models are distinguished for which the self-consistency condition is strictly satisfied and for which it is violated. Observed discrepancies are explained. The dependence of the degree of discrepancy (if there is one) on the density of the gas in the system, the energy of interaction of the activated complex, and the radius of adsorbent particles is established.

Evaluation of the predictive capability of ionic liquid force fields for CH4, CO2, NH3, and SO2 phase equilibria

Molecular dynamics simulations were performed to systematically compare four all-atom classical ionic liquid force fields and provide recommendations for the appropriate selection of an ionic liquid force field for the calculation of Henry's constants of gases. Four solutes of varying polarity, viz., CH4, CO2, NH3, and SO2 were investigated. The ionic liquids considered in this work contain the same cation, 1-n-butyl-3-methylimidazolium [C4mim]+ paired with four different anions chloride Cl−, methylsulfate [MeSO4]-, dicyanamide [DCA]-, and bis(trifluoromethanesulfonyl)imide [NTf2]-. The calculations were performed at three temperatures of 333, 353, and 373 K to enable the computation of enthalpies and entropies of absorption. Based on a comparison of the predicted results with those available in the literature, it was observed that the recently developed virtual-site ionic liquid force field tends to exhibit an overall better agreement with the published data in comparison to other force fields. Our results further indicate that, in general, SO2 is the most soluble gas due to the strongest interaction with ionic liquids, followed by NH3, CO2 and CH4.

Thermodynamic interpretation and prediction of CO2 solubility in imidazolium ionic liquids based on regular solution theory

Regular solution theory (RST) is the most popular model for the interpretation of the interaction between CO2 and ionic liquids. In the present work, the parameters of this model were determined for the CO2 absorption in eleven imidazolium ionic liquids. The y-intercept (A) of the RST model for the investigated imidazolium liquids increases with increasing temperature whereas the slope (B) remains constant. The values of RST parameters strongly depend on the Hildebrand parameters of the ionic liquids. It has been shown that ionic liquids surface tension and molar volume are the decisive parameters. The influence of the type of fluorinated anion and the length of the alkyl substituent on the solubility of CO2 was investigated. The dispersion of charge and the free space between the ions are key parameters determining the gas dissolution. The partial molar entropy and enthalpy of solvation were determined using a modified temperature dependent function of Henry's constant. It has been shown, that determination coefficient of the Henry's relation has to be larger than 0.9999 in order to estimate heat of salvation reliably. The molar enthalpy of solvation ranged from −11.6 to −14.7 kJ mol−1 at 298 K. Moreover, it is proposed that the entropy is composed of two parts, which explains the decrease in system order along with the elongation of the alkyl chain of the imidazolium substituent. Thus, the decrease of the gas condensation entropy component explains the increase of the partial molar entropy of solvation with temperature. It was shown that the molar volume of theoretically liquefied CO2 in the ionic liquid is lower than the actual value.

New Moment Equations in Chromatography

The exact solution obtained for the direct problem of chromatography within the model of an equilibrium adsorption layer using the integrand of the Euler γ-function has been analyzed. Analytical solutions have been presented for the first three temporal, two normalized, and two central moments as functions, which are represented by one-term fractions and comprise the length of an adsorbent layer, mobile phase velocity, effective kinetic constant, and Henry constant. The new moment equations substantially differ from those being used at present.

Thermodynamic and molecular insights into the absorption of H2S, CO2, and CH4 in choline chloride plus urea mixtures

AbstractDeep eutectic solvents (DESs) are a class of promising media for gas separation. In order to examine the potential application of DESs for natural gas upgrading, the solubilities of H2S, CO2, and CH4 in choline chloride (ChCl) plus urea mixtures were measured in this work. The solubility data were correlated with Henry's law equation to calculate the thermodynamic properties of gas absorption processes, such as Henry's constants and enthalpy changes. Grand‐canonical Monte Carlo simulations and quantum chemistry calculations were also performed to examine the mechanism of gas absorption processes. It is found that the absorption of H2S in ChCl + urea mixtures is governed by the hydrogen‐bond interaction between Cl of ChCl and H of H2S, whereas the absorption of CO2 and CH4 in ChCl+urea mixtures is governed by the free volume of solvents. Based on the different behavior of gas absorption, high H2S/CO2, H2S/CH4, and CO2/CH4 selectivities can be achieved by adjusting the ratio of ChCl/urea in mixtures.

Synthesis‐Gas Absorption under Real Process Conditions: Thermodynamic Aspects

AbstractThe solubility of synthesis gas was measured in the temperature range of 100–300 °C and pressure range of 1.0–5.0 MPa in polar (2‐propanol) and nonpolar (n‐dodecane) solvents. Thermodynamic parameters of the absorption, such as the Henry constant, absorption enthalpy, and apparent activation energy of absorption, were calculated on the basis of the obtained results. The phase equilibrium was calculated by using the Soave‐Redlich‐Kwong cubic equation of state, which could be used to predict the optimal process conditions for liquid‐phase Fischer‐Tropsch reactions in different solvents.

Removal of styrene in air stream by absorption combined with electrochemical oxidation

ABSTRACTAqueous solution absorptions are widely used as an effective way for the treatment of noxious gases discharged from various industrial processes. However, this technology may encounter problems in removing gaseous pollutants with low Henry constants, such as styrene from contaminated air. In this study, a novel electrochemical absorption reactor was devised to remove these air pollutants. The reactor consists of five pairs of stacked mesh electrodes. Each pair of mesh electrodes consists of a Ti/RuO2 anode and a Ti cathode. The dimension of mesh electrode is 100 mm × 100 mm with 3 mm × 5 mm rhombic holes evenly distributed. The distance between two neighbouring electrodes is 25 mm. The simulated gas was introduced into the reactor from the bottom of the reactor by a gas distributor. The experimental result shows that styrene in the air was effectively removed by the electrochemical absorption reactor, and the removal increased with the increase of current density applied to the reactor. It was found that almost 100% styrene removal was achieved in 1% NaCl solution with 1 pH value and a current density of 0.04 A/cm2 applied to the reactor. The major liquid phase products from styrene oxidation were confirmed to be 1-Phenyl-1, 2-ethanediol and benzaldehyde.

Predicting the phase behavior of hydrogen in NaCl brines by molecular simulation for geological applications

Hydrogen is targeted to have a significant influence on the energy mix in the upcoming years. Its underground injection is an efficient solution for large-scale and long-term storage. Furthermore, natural hydrogen emissions have been proven in several locations of the world, and the potential underground accumulations constitute exciting carbon-free energy sources. In this context, comprehensive models are necessary to better constrain hydrogen behavior in geological formations. In particular, solubility in brines is a key-parameter, as it directly impacts hydrogen reactivity and migration in porous media. In this work, Monte Carlo simulations have been carried out to generate new simulated data of hydrogen solubility in aqueous NaCl solutions in temperature and salinity ranges of interest for geological applications, and for which no experimental data are currently available. For these simulations, molecular models have been selected for hydrogen, water and Na+and Cl−to reproduce phase properties of pure components and brine densities. To model solvent-solutes and solutes-solutes interactions, it was shown that the Lorentz-Berthelot mixing rules with a constant interaction binary parameter are the most appropriate to reproduce the experimental hydrogen Henry constants in salted water. With this force field, simulation results match measured solubilities with an average deviation of 6%. Additionally, simulation reproduced the expected behaviors of the H2O + H2 + NaCl system, such as the salting-out effect, a minimum hydrogen solubility close to 57 °C, and a decrease of the Henry constant with increasing temperature. The force field was then used in extrapolation to determine hydrogen Henry constants for temperatures up to 300 °C and salinities up to 2 mol/kgH2O. Using the experimental measures and these new simulated data generated by molecular simulation, a binary interaction parameter of the Soreide and Whiston equation of state has been fitted. The obtained model allows fast and reliable phase equilibrium calculations, and it was applied to illustrative cases relevant for hydrogen geological storage or H2natural emissions.

Combustion analysis of a light duty diesel engine using oxygen-enriched and humidified combustion air

The present work presents the results of 3D CFD combustion simulations of a current production 4-cylinder turbocharged Diesel engine using oxygen-enriched and humidified combustion air. Enriched Air (EA) is supposed to be produced by desorption from water, exploiting the different Henry constants of N2 and O2. Simulation results show that EA permits to increase the engine thermal efficiency (up to 10%) and drastically reduces soot emissions but increases in-cylinder peak pressure and NOx emissions. Combustion air humidification helps to reduce NOx increment, without losing the advantage in terms of thermal efficiency and in soot reduction, even if NOx emissions cannot be reported to the base case values.

Hydrogen Bond OH...ΠGTCB in Adsorption of Isobutanol, Tert-Butanol, and Tert-Amyl Alcohol on Graphitized Thermal Carbon Black

Henry constants K1 are calculated for stable conformers of isobutanol, tert-butano, and tert-amyl alcohol molecules on graphitized thermal carbon black (GTCB). Parameters of the atom-atom potential taking into account the formation of a hydrogen bond between the adsorbate OH group with GTCB π electrons with regard to the direction are found. By density functional theory (DFT) and molecular statistical theory of adsorption the ratio between conformers stable in the gas phase and the adsorbed state are determined. The experimental Henry constants are compared with the results of the molecular statistical calculation for stable conformers of alcohols forming the bond OH...πGTCB.