Henry's Constants Research Articles

Geometric investigation of the three-coefficient Redlich-Kister expansion global phase diagram for binary mixtures

The Redlich-Kister (RK) three-coefficient expansion for gE is investigated geometrically and its global phase diagram is presented. The azeotropy and stability conditions yield surfaces (envelopes) in the three-dimensional azeotropy space and stability space respectively, whose axes represent variables determined from Henry's constants, pure substance vapor pressures and the highest-order RK coefficient. Zeotropy, single, double, triple, and tangent azeotropy (or saddle-point azeotropy), as well as stability, are identified in regions of the azeotropy and stability spaces. The connection between the two spaces is established. Envelopes for gE = 0 and dgE/dx=0 are also constructed in the azeotropy or stability spaces, to indicate the gE shape. Some results regarding the shape of gE are transferable to hE and vE when these are described independently by three-coefficient Redlich-Kister expansions. The analysis is applied to eleven actual mixtures, whose state is represented in the azeotropy and stability space. Fitting temperature-dependent RK coefficients allows to estimate the continuous path the mixture follows in both spaces at varying temperature, revealing possible intermediate states and the mixture tendency at the extreme temperatures.

Supercritical adsorption in micro- and meso-porous carbons and its utilisation for textural characterisation

Understanding supercritical gas adsorption in porous carbons requires consistency between experimental measurements at representative conditions and theoretical adsorption models that correctly account for the solid’s textural properties. We have measured unary CO2 and CH4 adsorption isotherms on a commercial mesoporous carbon up to 25 MPa at 40 °C, 60 °C and 80 °C. The experimental data are successfully described using a model based on the lattice Density Functional Theory (DFT) that has been newly developed for cylindrical pores and used alongside Ar (87K) physisorption to extract the representative pore sizes of the adsorbent. The agreement between model and experiments also includes important thermodynamic parameters, such as Henry constants and the isosteric heat of adsorption. The general applicability of our integrated workflow is validated by extending the analysis to a comprehensive literature data set on a microporous activated carbon. This comparison reveals the distinct pore-filling behaviour in micro- and mesopores at supercritical conditions, and highlights the limitations associated with using slit-pore models for the characterisation of porous carbons with significant amounts of mesoporosity. The lattice DFT represents a departure from simple adsorption models, such as the Langmuir equation, which cannot capture pore size dependent adsorption behaviour, and a practical alternative to molecular simulations, which are computationally expensive to implement.

Investigation of micropollutants removal from landfill leachate in a full-scale advanced treatment plant in Istanbul city, Turkey

Although the levels of micropollutants in landfill leachate and municipal wastewater are well-established, the individual removal mechanisms and the fate of micropollutants throughout a landfill leachate treatment plant (LTP) were seldom investigated. Therefore, the determination of the removal efficiencies and the fates of micropollutants in a full-scale leachate treatment plant located in the largest city of Turkey were aimed in this study. Some important processes, such as equalization pond, bioreactor, ultrafiltration (UF) and nanofiltration (NF), are being operated in the treatment plant. Landfill leachate was characterized as an intense pollution source of macro and micropollutants compared to other water types. Chemical oxygen demand (COD), NH3, suspended solids (SS) and electrical conductivity (EC) values of the landfill leachate (and their removal efficiencies in the treatment plant) were determined as 18,656 ± 12,098 mg/L (98%), 3090 ± 845 mg/L (99%), 4175 ± 1832 mg/L (95%) and 31 ± 2 mS/cm (51%), respectively. Within the scope of the study, the most frequently and abundantly detected micropollutants in the treatment plant were found as heavy metals (8 ± 1.7 mg/L), VOCs (38 ± 2 μg/L), alkylphenols (9 ± 3 μg/L) and phthalates (8 ± 3 μg/L) and the overall removal efficiencies of these micropollutants ranged from −11% to 100% in the treatment processes. The main removal mechanism of VOCs in the aerobic treatment process has been found as the volatilization due to Henry constants greater than 100 Pa·m3/mol. However, the molecular weight cut off restriction of UF membrane has caused to less or negative removal efficiencies for some VOCs. The biological treatment unit which consists of sequential anoxic and oxic units (A/O) was found effective on the removal of PAHs (62%) and alkylphenols (87%). It was inferred that both NO3 accumulation in anoxic reactor, high hydraulic retention time (HRT) and sludge retention time (SRT) in aerobic reactor provide higher biodegradation and volatilization efficiencies as compared to the literature. Membrane processes were more effective on the removal of alkylphenols (60–80%) and pesticides (59–74%) in terms of influent and effluent loads of each unit. Removal efficiencies for Cu, Ni and Cr, which were the dominant heavy metals, were determined as 92, 91 and 51%, respectively and the main removal mechanism for heavy metals has thought to be coprecipitation of suspended solids by microbial biopolymers in the bioreactor and the separation of colloids during membrane filtration. Total effluent loads of the LTP for VOCs, semi volatiles and heavy metals were 1.0 g/day, 5.2 g/day and 1.5 kg/day, respectively. It has been concluded that the LTP was effectively removing both conventional pollutants and micropollutants with the specific operation costs of 0.27 $/(kg of removed COD), 0.13 $/(g of removed VOCs), 0.35 $/(g of removed SVOCs) and 2.6 $/(kg of removed metals).

Computation of gas solubilities in choline chloride urea and choline chloride ethylene glycol deep eutectic solvents using Monte Carlo simulations

Deep eutectic solvents (DESs) are considered as green alternatives to room temperature ionic liquids (RTILs), due to their lower-cost synthesis and more environmentally friendly nature. In this work, Monte Carlo (MC) simulations have been used to compute the solubilities of CO2, H2S, CH4, CO, H2, and N2 in choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs. Due to the strong intermolecular interactions of DESs, leading to high viscosities, MC simulations present significant challenges with respect to system equilibration and solute molecule insertions. The Continuous Fractional Component Monte Carlo (CFCMC) method has been used with our open-source code, Brick-CFCMC, to improve molecule insertions and equilibration of the system, and directly compute the excess chemical potential and solubility (in terms of the Henry constant) of the gas molecules in the DESs. Pure DES properties, such as density and radial distribution functions (RDFs), were well reproduced by MC simulations. The solubilities of gases were, however, underestimated by the CFCMC simulations compared to available experimental data from literature. The order of solubilities of the different gases in ChClU at 328 K was obtained as H2S > CO2 > CH4 > H2 > CO > N2, which reasonably agrees with experimental data from literature. The OPLS force field resulted in larger average Henry constants in ChClEg, compared to the GAFF force field, implying the better suitability of the GAFF force field for the calculations. Smaller ionic charge scaling factors were shown to increase the solubilities of the gases in the DESs, but result in lower densities. The differences between the computed Henry constants from MC simulations and experimental data from literature may be caused by the unsuitability of the used force field parameters of the DESs in combination with those of the solute gases. Nonetheless, experimental data from literature is scarce (except for CO2) and in some cases contradictory, which makes the comparison with the computational results difficult.

Properties of symmetric 1,3-diethers based on glycerol skeletons for CO2 absorption

CO2 absorption is at the forefront of separation processes due to the attention given to greenhouse gas emission control and its potential to slow global climate change. This report describes the study of new physical solvents for CO2 absorption through a single step etherification of epichlorohydrin, yielding symmetric 1,3-diethers based on a glycerol skeleton. Five such compounds were obtained in this manner: 1,3-dimethoxypropan-2-ol (DMP, 623-69-8), 1,3-diethoxypropan-2-ol (DEP, 4043-59-8), 1,3-di(propan-2-yloxy)propan-2-ol (DIPP, 13021-54-0), 1,3-bis(2-methoxyethoxy)propan-2-ol (DMEP, 130670-52-9), and 1,3-bis(2,2,2-trifluoroethoxy)propan-2-ol (DTEP, 691-26-9). Screening of synthesis methods was conducted and aqueous sodium hydroxide solution was found to be the best reaction medium. All compounds were purified through rigorous distillation and drying techniques. Density and viscosity values for each compound were collected in the range of 293.15–353.15 K. CO2 absorption capacities of these solvents were measured at 303.15, 318.15, 333.15 and 348.15 K at CO2 partial pressures in the range of 2–6 atm. Miscibility of these compounds with common organic solvents and water was also determined. Dipole moments were calculated for exploration of structure – property relationship. Among these solvents, DMEP and DTEP exhibited the largest affinity for CO2 with Henry's constants of 48.0 and 45.4 atm, respectively, at 303.15 K, reaching the same level as diglyme used industrially while allowing further modification for improvement in CO2 capture ability. Data obtained in this work should be useful as a guide for further design and synthesis of solvents based on glycerol skeletons for CO2 absorption applications.

Correlation and prediction of thermodynamic properties of dilute solutes in water up to high T and P. II. Normal fluids CO2, C2H4, C2H6, C3H8, n-C4H10, i-C4H10, functional groups CH3 and CH2

Fugacity coefficients of dilute aqueous solutions of six species belonging to normal fluids (CO2, C2H4, C2H6, C3H8, n-C4H10, i-C4H10) as well as functional groups CH3 and CH2 have been evaluated from ambient conditions (298 K, 0.1 MPa) to high temperatures (up to 2000 K) and water densities (up to 1500 kg m−3). The basis of the approach is a correlation developed for the function, A12∞=V2∞/κTRT, that includes known constraints: second virial coefficients at low water densities, hard sphere behavior at high water densities, near-critical principles, and corresponding-states relations. A comparison with literature data at subcritical (Henry's and vapor-liquid distribution constants) and supercritical temperatures (fugacity coefficients) is made. For aqueous CO2, the agreement with literature data is generally satisfactory. It is shown that for other solutes existing disagreements can be traced mostly to the values of the second cross virial coefficients employed in the literature models, suggesting the room for improvement of existing recommendations.

Henry's law constant as a function of temperature and pressure to calculate the solubility of difluoromethane (R-32) in ionic liquids

Abstract The Henry's law constant of the refrigerant difluoromethane (R-32) in various ionic liquids is determined. The topic is interest for the capture of refrigerant gases by ionic liquids that could be used as lubricants or additives for refrigerant fluids in refrigerating processes. This topic has received especial attention in the latest years and various studies on the solubility of these systems have been presented in the literature. The so-called VPT equation of state (a generalization of the Patel-Teja model) with the mixing rules of Kwak and Mansoori are employed to correlate solubility data and to check the thermodynamic consistency of the experimental data used in the study. The VPT model contains three generalizing parameters that are determined using experimental data and by optimizing bubble pressure correlation. The calculated Henry's constants are correlated in terms of the temperature, to finally propose a generalized Pade-type expression for The Henry's constant.

Thermodynamic and process modeling of the recovery of R410A compounds with ionic liquids

• A soft-SAFT model is used to describe the solubility of R410A compounds in ILs. • Henry constants, the enthalpy and entropy of dissolution are predicted. • [C 2 mim][Tf 2 N] is chosen based on selectivity and solubility predictions. • The ternary diagram IL-R32-R125 is built to evaluate the competitive selectivity. • A process recovery simulation unit using [C 2 mim][Tf 2 N] is optimized. European regulations are limiting the use of hydrofluorocarbons (HFCs) as refrigerants because of their elevated global warming potentials (GWPs). Apart from their substitution by other compounds with lower environmental impact, one of the plausible approaches to meet the legal requirements is the formulation of new refrigerant blends containing a low GWP compound (e.g., hydrofluoroolefins) mixed with one HFC that provides the necessary thermodynamic characteristics to act as an effective refrigerant. Thus, the recovery and reuse of HFCs seems a promising approach to increase their lifespan and reduce their production. However, current regeneration technologies that are based on distillation are highly energy-intensive. Therefore, the development of novel separation processes to selectively separate HFCs is needed for the practical implementation of circular economy principles in the use of refrigerants. This work is a step forward on using ionic liquids (ILs) to selectively separate F-gases. The advanced molecular-based soft-SAFT equation of state (EoS) is used as a tool to assess the potential of ILs as a solvent platform for the selective separation of the compounds forming the R410A refrigerant blend: R32 and R125. Soft-SAFT is employed to model the absorption of these HFCs into different ILs with different fluorinated anions. Ternary diagrams are then predicted for the absorption of R32/R125 mixtures into selected ILs to evaluate the competitive selectivity between both compounds. Based on this study, a potential ionic liquid candidate is chosen and a process simulation is performed to estimate the approximate energy cost of the separation and recovery process.

CO2 solubility in some amino acid-based ionic liquids: Measurement, correlation and DFT studies

The solubility of carbon dioxide (CO2) gas in three amino acid–based ionic liquids (AAILs), 1–butyl–3–methylimidazolium glycinate ([BMIm][Gly]), 1–butyl–3–methylimidazolium alaninate ([BMIm][Ala]), and 1–butyl–3–methylimidazolium valinate ([BMIm][Val]) has been experimentally investigated by quartz crystal microbalance (QCM). Solubility of CO2 has been evaluated at temperatures from 288.15 to 318.15 K and pressures up to 4 bars. According to the sorption mechanism, CO2 solubility in AAILs was correlated by a reaction equilibrium thermodynamic model. The thermodynamic parameters including Henry's constant, reaction equilibrium constant, enthalpy of physical dissolution, and the chemical reaction were calculated and compared with assess the CO2 absorption performance in AAILs. The obtained results indicate that glycinate anion ([Gly]) has more CO2 sorption capacity compared to alaninate ([Ala]) and valinate ([Val]). The chemical sorption of CO2 via carbamate formation was confirmed using FT-IR spectroscopy. Furthermore, density functional theory (DFT) calculations have been performed to investigate the interactions between the amino acid anion–based ionic liquids and CO2.

Thermodynamics analysis of the adsorption of CH4 and CO2 on montmorillonite

The greater adsorption ability of shale to CO2 offers an alternative method to enhance shale gas recovery, where a potential solution for CO2 sequestration into a deep shale reservoir can also be realized. Clay minerals are the important storage space for shale gas. In this work, the isotherm adsorption curves of CH4 and CO2 on montmorillonite at 288 K, 308 K and 328 K were obtained using gravimetric apparatus. The selectivity factor of CO2 over CH4 (SCO2/CH4) and Henry's constants (KH) of CH4 and CO2 were calculated. More importantly, the thermodynamics parameters of CH4 and CO2, including Gibbs free energy change (ΔG), surface potential (Ω), isosteric heat of adsorption (Qst) and entropy change (ΔS), were thoroughly analysed. The results indicate that all SCO2/CH4 values are obviously greater than one, and injecting CO2 into a clay-rich shale reservoir to enhance the shale gas recovery is feasible. CH4 has smaller KH than CO2, which shows that CH4 has a weaker affinity on the montmorillonite surface. Low temperature helps to enlarge KH and promote the adsorption of CH4 and CO2. Increasing the pressure causes the increase in ΔG and Ω of CH4 and CO2. The higher ΔG and Ω of CO2 compared to CH4 reveal that the CO2 adsorption on montmorillonite is more favourable and spontaneous. When the loading increases, the Qst values of CH4 and CO2 reduce. CH4 has a smaller Qst than CO2, which suggests the stronger interaction of CO2 with montmorillonite. CH4 and CO2 have decreasing ΔS with the loading. Under larger surface coverage conditions, the disorder of the adsorbed molecules is larger, and most of the injected molecules are trapped as a free state in the pore space. The higher ΔS of CO2 illustrates that CO2 molecules constitute a much more stable rearrangement than CH4 molecules. The temperature has a slight effect on the ΔS of CH4 and CO2.

The Henry constant and isosteric heat at zero loading for adsorption on energetically heterogeneous solids absolute versus excess

We present a self-consistent analysis of adsorption of gases on energetically heterogeneous solids and derive expressions for the Henry constant and the isosteric heat at zero loading, qst(0), for both excess and absolute amounts of molecules; the latter being amenable to thermodynamic analysis. Results obtained by Monte Carlo integration are shown to depend on the system size for calculations using the total number of molecules in the adsorbed and gas phases of the system. In the limit when loading approaches zero, the thermodynamic variables obtained from the fluctuation theory in a grand canonical simulation are in agreement with the Henry constant and the isosteric heat at zero loading calculated from Monte Carlo integration, establishing the consistency of the analysis of isotherm and isosteric heat for the full range of loading. The equations for the isotherm (and the Henry constant), and the isosteric heat for a complex substrate, can be written in terms of the local isotherms and the local isosteric heats of the components comprising the substrate for all loadings. This results in a significant saving in computing time for the calculation of the thermodynamic variables of a complex substrate.

Fabrication of Functionalized Porous Silica Nanocapsules with a Hollow Structure for High Performance of Toluene Adsorption-Desorption.

Functionalized mesoporous silicas are an emerging kind of adsorbents for the removal of volatile organic compounds (VOCs). Breaking the limitations of traditional mesoporous silica, in this study, porous silica nanocapsules (PSNs) functionalized with phenyl and n-octyl groups (named as p-PSN and n-PSN, respectively) were developed for the first time. Under dry conditions, the PSNs exhibited highest dynamic adsorption capacity and desorption efficiency among the ever-reported typical adsorbents (i.e., SBA-15, KIT-6, silicalite-1, and activated carbon). Under wet conditions, the functionalized PSNs made up the defects of pure PSNs, displaying excellent hydrophobicity. The QWET for n-PSN and p-PSN increased by 44 and 76%, respectively, as compared with that of pure PSNs in 50% relative humidity. The Henry constant of static adsorption demonstrated that p-PSN had a better capture ability for toluene, which was owing to the π-interaction between the phenyl groups and the toluene molecules. In addition, p-PSN showed considerable stability after six consecutive dynamic adsorption–desorption cycles in 50% relative humidity.

Theoretical and experimental study of foam stability mechanism by nanoparticles: Interfacial, bulk, and porous media behavior

Abstract Foam flooding has been applied as a promising method in enhanced oil recovery to obviate the challenges of gas flooding such as fingering, channeling and overriding. However, long-term foam stability is crucial for mobility control. In this work, the effective mechanisms on foam stability in the presence of CaCO3 nanoparticles were assessed both theoretically and experimentally. The static and dynamic behaviors of cationic surfactant (HTAB) foam in the presence of CaCO3 nanoparticles with different hydrophobicity were evaluated. The CaCO3 nanoparticles were treated with a series of long-chain fatty acids to generate a range of wettability. Afterward, the underlying mechanisms were revealed by conducting the supplementary experiments, including measurements of effective diffusion coefficient (Deff), Henry's constant (KH), interfacial tension (IFT), and zeta potential of nanoparticles. Further, efforts were made to analyze the interfacial interactions using xDLVO theory. By increasing of nanoparticles hydrophobicity, the continuous reduction of effective diffusion coefficient, solubility, and IFT was observed, which means higher foam stability. However, the adsorption of modified nanoparticles on the air-solution interface could reduce the total disjoining pressure between two parallel plates, supported by xDLVO prediction. This phenomenon has an adverse effect on the thin film stability. Therefore, there would be an optimum extent of nanoparticles surface modification to obtain the most stable foam stability, which was in agreement with the both bulk and porous media observations. The optimum condition was shifted to the nanoparticles modified with the lower chain fatty acids by increasing the concentration of fatty acid solutions. In this case, the negative effect of reduced disjoining pressure was more pronounced.

Effect of salt on CO2 solubility in salmon (Salmo salar L) stored in modified atmosphere

Salt and CO2 in the form of modified atmosphere (MA) packaging are often used forms of preservation of seafood, as they both are known for their ability to reduce spoilage and health risks. However, little is known regarding interaction between the two when applied to seafood. Hence this experiment investigated CO2 solubility in salmon injected with various brines and packaged using MA packaging or soluble gas stabilization (SGS) followed by MA packaging. Regardless of packaging method, increasing NaCl concentration decreased the absorbed CO2 concentration, as seen from analysis of head space composition, calculations of Henry's constant, and absorbed amount of CO2 within the product. However, the effect was only significant after long storage, as no effect of NaCl was observed in the samples before MA packaging in retail trays. Furthermore, use of SGS significantly increased amount of absorbed CO2 as compared to regular MA packaging. The effect of SGS outnumbered the negative effect of NaCl, thus making the use of both NaCl and CO2 possible without losing effect of either.

Effect of physicochemical properties of ammonium-based ionic liquids on CO2 capturing: An insight into structure-activity relationship

The physicochemical properties including density, viscosity and refractive index of five ionic liquids (ILs) consisting of 2-acrylamido-2-methylpropanesulfonate [AMPS] as anion source with ammonium-based cations (tetrabutylammonium [TBA], tetrapropylammonium [TPA] and tetraethylammonium [TEA], tetramethylammonium [TMA] and (vinylbenzyl)trimethylammonium [vbn]) were measured and influence of these properties upon CO2 sorption was investigated. The viscosity and density measurements were taken at atmospheric pressure within the temperature range of (293.15–363.15) K, whereas refractive indexes were determined within (288.15–333.15) K. An increase in the side-carbon chain length of ammonium-based cations resulted in decreased density with a corresponding increase in viscosity and refractive index. Among the studied ILs, [TBA][AMPS] gave the highest viscosity and least density over the whole range of temperature and a higher CO2 sorption of 0.51 mol fraction at 298.15 K and 1 MPa was observed showing dependency of CO2 solubility on the thermophysical properties of studied ILs. Moreover, among investigated ILs, molar volume of [TBA][AMPS] was found to be largest (433.3729 cm3mol-1), which resulted in the higher amount of CO2 sorption in comparison to other investigated ILs. Also, Henry's constant of 1.51 MPa was found for [TBA][AMPS] which was 10.9, 33.4, 44.3 and 24.8% less than [TPA][AMPS], [TEA][AMPS], [TMA][AMPS] and [vbn][AMPS], respectively. The current work offers an in depth study to understand structure-activity relation between physicochemical properties and CO2 solubility of investigated ILs and explores the ways for enhanced CO2 sorption.

A Comparative Study of Adsorption of Isomeric Molecules on Carbon Sorbents from a Gas and a Liquid

A comparative study of adsorption of isomeric alkylbenzenes, alkylphenols, and alkanes on carbon sorbents from a gas and a liquid phase using an extended variant of molecular statistics calculations is carried out. In simulation, conformational non-rigidity of molecules is taken into account. This method is shown to satisfactorily estimate proportions between the adsorption characteristics for isomers of hydrocarbons adsorbed on graphitized thermal carbon black from a gas phase. In the case of adsorption from a liquid phase on porous graphitized carbon, additionally, the effect of a solvent and polarizability of the sorbent surface by charged sites of a sorbate molecule are considered. It is demonstrated that, for correct prediction of the ratio between the Henry constants for adsorption of isomers of alkylphenols and alkylbenzenes from solutions, it is necessary to consider both these factors.

Dynamics of Monolayer Physisorption in Homogeneous Mesoporous Media

A model for monolayer physisorption of a one-component gas on the pore surface of a homogeneous macroporous or mesoporous porous medium is presented. It originates from an averaging over many pores of a macroporous medium filled with a one-component fluid. The resulting model does not assume anything about pore shape, but assumes that the pores are so large that capillary condensation does not occur. Mathematically, the model gives coverage as the solution of an ordinary, first-order, differential equation, where the time derivative of coverage is proportional to the difference between the chemical potential of the adsorbate and the chemical potential of the ambient gas. Coverage is determined by the ambient gas density, with temperature, adsorbate critical temperature, and the Henry adsorption constant as parameters. The rest of this abstract describes what is deduced from the equations of the model. Adsorbate phase transitions are built into the model by the use of van der Waals equations of state. Equilibrium isotherms are derived from the equality of the chemical potentials. The differential equation for coverage makes it possible to determine the mathematical stability of the equilibrium isotherms, and a number of properties of the isotherms are derived, the most important being as follows: (i) an adsorbate phase transition is always accompanied by a well-defined hysteresis loop, although “loop” is somewhat misleading as its vertical boundaries do not consist of equilibrium states; (ii) the vertical boundaries are exactly located; (iii) the upper and lower boundaries consist of states that are mathematically stable, while being either physically stable or metastable, and if physical metastability is the case, then the actual state of the adsorbate (mono- or bi-phasic) will not be visible on the equilibrium isotherm. The shapes of the equilibrium isotherms are largely determined by the value of the Henry constant, whether the isotherms are subcritical or supercritical. Expressions for the location of an equilibrium isotherm’s region of fastest variation and for the locations of the vertical boundaries of its hysteresis loop are found that also show the importance of Henry’s constant. Dynamical, that is, time-dependent isotherms are presented for the case describing the variation of coverage resulting from forcing the ambient gas to undergo a compression–decompression loop. Two subcases are considered: the subcritical and the supercritical adsorbate. It is shown that coverage in terms of ambient pressure exhibits closed loops, even in supercritical isotherms. However, supercritical loops shrink when the cycle time increases, reminiscent of rate-dependent hysteresis observed in piezoelectricity. The model is used to interpret two experiments on the sorption of CO2 and CH4 on coal that showed hysteresis loops in isotherms of supercritical adsorbates and that were originally interpreted as leading to different Henry constants for adsorption and for desorption. The interpretation set forth here uses the inherent dynamics of the model and looks at the loop as just one isotherm evolving in time, thus leading to a unique Henry constant.

Technical support of aerobic fermentation processes

The article shows that aerobic fermentation of sugar-containing media requires the presence of dissolved oxygen in them. In most cases, the latter condition is fulfilled by the introduction and dispersion in the liquid phase of the air, which is compressed to levels corresponding to hydrostatic pressures with some exaggeration. The formation of the dispersed gas phase is accompanied by the interaction of the inlet air and the liquid phase, the efficiency of which is determined by the formed contact surface. The study presents generalizations that relate to the dynamics of biomass growth and correlate with the amount of oxygen introduced into the system. It is important that oxygen refers to gases with limited solubility, and therefore the hydrodynamic state and the interfacial surface are among the factors of intensification of mass transfer processes. It is also shown that the nominal estimation of the hydrodynamic state of gas-liquid media should begin with an assessment of the aeration intensity and it is proposed to take the reduced gas phase velocity as the ratio of the volume air flow to the cross-sectional area of the apparatus. Turning to the indicator of the reduced speed negates the influence of geometrical parameters in the form of the ratio of height and diameter. The results of the process and the efficiency of the equipment used are determined by the performance indicators in the form of concentrations of microorganisms and the output rate of the input power supply. The combination of these requirements leads to the need to combine the maximum achievable concentrations of dissolved oxygen and the minimum concentrations of sugars. The features of the double influence of ambient temperatures in the manifestations of the optimal for microorganisms and for the solubility of gases in accordance with Henry's law are shown, the values of Henry constants are given. The list of factors of influence includes such physical parameters of the environment as viscosity, surface tension, osmotic pressure, hydrostatic pressure, temperature. It is determined that the presence of dissolved nitrogen has an influence on the hydrodynamics of gas-liquid media due to changes in hydrostatic pressure in the circulation circuits.

Silicon distribution in SAPO-11 molecular sieves: Simulation and experimental adsorption study

Abstract A method for investigation of the Si distribution in the SAPO-11 structure based on the aggregate of simulation and experimental adsorption methods is suggested. Twelve possible configurations of the silicon location in the SAPO-11 framework corresponding to substitution of one P atom for a (Si,H+) pair in the elementary cell were simulated. The probabilities of silicon localization in each studied configuration were calculated. Hydrogen adsorption at 77 K on AlPO/SAPO was simulated by GCMC method for a fragment of the AEL structure consisting of 2 × 2 × 3 elementary cells. A comparison of the experimental and calculated Henry constants made it possible to estimate the silicon concentrations in the bulk of the zeolite crystallites.

Tuning the Molecular and Cationic Affinity in a Series of Multifunctional Metal-Organic Frameworks Based on Dodecanuclear Zn(II) Carboxylate Wheels.

A series of new zinc(II)-thiophene-2,5-dicarboxylate (tdc) MOFs based on novel dodecanuclear wheel-shaped building blocks has been synthesized in almost quantative yields. Single-crystal X-ray diffraction analyses reveal 3D porous frameworks with a complex composition [Zn12(tdc)6(glycolate)6(dabco)3] where glycolate is a deprotonated polyatomic alcohol (ethylene glycol, EgO2, 1; 1,2-propanediol, PrO2, 2; 1,2-butanediol, BuO2, 3; 1,2-pentanediol, PeO2, 4; glycerol, GlO2, 5) and dabco is 1,4-diazo[2.2.2.]bicyclooctane. All compounds 1-5 are isostructural except for pendant groups of the diols decorating the surface of channels. The adsorption of small gases (N2, CO2, CH4, C2H2, C2H4, C2H6) and larger hydrocarbons (benzene, cyclohexane) both in liquid and vapor phases was thoroughly investigated for all compounds. The zero-coverage adsorption enthalpies, Henry constants, and selectivity factors by various models are calculated and discussed. The versatile adsorption functionality of the title series results from the variable nature of the diol and could be tailored for a specific adsorbate system. For example, 1 shows excellent selectivity of benzene over cyclohexane (20:1 for vapors, 92:1 for liquid phase), while 4 demonstrates unprecedented adsorption preference of cyclohexane over benzene (selectivity up to 5:1). The compound 5 demonstrates great adsorption selectivity for CO2/N2 (up to 75.1), CO2/CH4 (up to 7.7), C2H2/CH4 (up to 14.2), and C2H4/CH4 (up to 9.4). Also, due to polar nature of the pores, 5 features size-selective sorption of alkaline metal cations in order Li+ > Na+ > K+ > Cs+ as well as a notable luminescent response for cesium(I) ions and urea.