Solubility Of H2 Research Articles

Effect of Water Saturation on H2 and CO Solubility in Hydrocarbons

The effect of water on the solubility of syngas in hydrocarbons has typically been ignored when developing models for Fischer-Tropsch slurry bubble column reactors (SBCR), despite water being a major by-product. Therefore, a generalized correlation was developed to predict water solubility in hydrocarbons at high temperatures, and was used to calculate the effect of water saturation on H2 and CO solubility in hydrocarbons using the Span Wagner equation of state. The presence of water was shown to have a much more significant effect on H2 solubility in hydrocarbons, compared to CO.

A new approach to the upgrading of the traditional propylene carbonate washing process with significantly higher CO2 absorption capacity and selectivity

Although a series of advanced technologies and materials, like ionic liquids and metal organic frameworks, is being developed for carbon capture, traditional techniques, like propylene carbonate (PC) washing, are still widely applied in industry because of their low material costs and ease of operation. Considering the low CO2 solubility and selectivity in PC, we have tried to improve the PC washing process by adding 2-methylimidazole (mIm) to PC in the presence of ethylene glycol (EG) as cosolvent. A series of EG-mIm-PC complex solvents was prepared and their viscosities measured at different temperatures. The absorption isotherms of CO2 in these complex absorbents, as well as in pure PC, were measured at 293.15, 303.15, and 313.15 K at 0.1–0.8 MPa. The heats of CO2 absorption in these solvent mixtures were calculated using the Clausius-Clapeyron equation. For evaluating the effect of mIm on the selectivity of CO2 over other gas species, the absorption isotherms of CH4, N2, and H2 in pure PC and in 24%-mIm complex solvent with highest CO2 solubility were also measured. The results showed that the viscosities of these complex absorbents, as well as the solubility and heats of absorption of CO2 in all of them, moderately or slowly increased with an increase in mIm mass fraction, when the mIm content was lower than 20 wt%, and rapidly increased when it surpassed 20 wt%. The CO2 solubility could be more than doubled when the mIm content reached 24 wt% while viscosity and absorption heat still remains at low levels, that is, lower than 14 mPa·s and 26 kJ/mol, respectively. More importantly, the solubilities of CH4, N2, and H2 drastically decreased in the presence of mIm; using the 24 wt%-mIm complex absorbent instead of pure PC, the selectivity of CO2 over those other gas species increased by: 0.7–2.8 times for CH4, 3.9–6.3 times for N2, and 3.5–7.7 times for H2, with more significant improvements at lower pressure ranges. This work presents a very promising approach to PC washing technology upgrading.

H2/CO2 Gas Transport Performance in Poly (Ethylene Oxide) Reverse-selective Membrane with Star-like Structures

A series of poly (ethylene oxide) (PEO) membranes with star-like structures for CO2/ H2 separation were prepared by the photo-polymerization method. The structure of PEO membrane was characterized by Fourier transform infrared spectroscopy (FTIR). The thermal property and inter-segmental distance of polymer chain were investigated by differential scanning calorimetry and wide-angle X-ray diffraction, respectively. The density was determined by hydrostatic weighing method. The gas permeability, solubility and diffusivity of CO2 and H2 were investigated in the star-like PEO membranes. The relationship between gas permeation performances and physical properties was also discussed. The membrane exhibits outstanding CO2 permeability (about 9.7×10-11 cm3 (STP) cm/cm2/s/Pa) and CO2/H2 selectivity (about 11) compared with other membranes.

Study on the Electrochemical Hydrogenation of Soybean Oil under H2 Conditions.

The solubility of H2 in electrolytes, H2 reaction consumption and the conductivity of electrolytes under different pressures in an electrochemical hydrogenation reactor were studied. It was found that with an increase in H2 pressure, H2 was electrolyzed at the anode, accompanied by the generation of H+. The solubility of H2 in the electrolytes and the conductivity of the electrolytes also increased. At first, the reaction consumption increased, followed by a tendency to be stable at 3 MPa. Therefore, the electrochemical hydrogenation of soybean oil was carried out at a H2 pressure of 3 MPa. When the current was 120 mA, the temperature was 50°C, the agitation speed was 300 rpm, and the time was 7.5 h, the IV of hydrogenated soybean oil was 99.6 g I2/100 g oil, and the TFA content of the oil was 4.3%.

The Effect of Melting Temperature Aluminum Metal Casting Using Mixed Degasser Based Sodium Fluoride and Sodium Nitrate

The effect of NaF and NaNO3 based degasser on mechanical properties of Al-Si 12% casting has been investigated. The quality of Al-Si casting, especially in mechanical properties, is important in some applications. However, the existence of gas porosity, which is formed due to the high solubility of H2 at melt temperature in casting process, reduces mechanical propertis of Al-Si 12% casting product. In this research, we used NaF and NaNO3 as degasser as an addition in casting process. The experiments were conducted at pouring temperature of 660°C, 680°C, 700°C and 720°C. The mechanical properties (which are determined by tensile test, hardness test and impact test) with and without degasser were measured and compared. We found that in all pouring temperature, the addition of degasser will improve all of mecahnical properties measured. In addition we found that the increase of tensile strength was optimum at pouring temperature of 720°C at 25,5 % of increase, hardness was optimum at pouring temperature of 720°C at 33,3 % of increase and impact strength was optimum at pouring temperature of 720°C at 25 % of increase. The improvement of mechanical properties is due to the role of NaF and NaNO3 by binding H2 gases which is formed in melting process. This H2 binding was shown in microstructure observation which shows that the porosity of casting product visually decreased.

Measurement and prediction of mass transfer coefficients for syngas constituents in a hollow fiber reactor

Syngas fermentation for producing biofuels and other products suffers from mass transfer limitations due to low CO and H2 solubility in liquid medium. Therefore, it is critical to characterize mass transfer rates of these gases to guide bioreactor design and optimization. This work presents a novel technique to measure the volumetric mass transfer coefficients (kia) for H2 and CO using gas chromatography in a non-porous hollow fiber reactor (HFR). The largest measured kia for H2 and CO were 840 and 420 h−1, respectively. A model was developed to predict kia for H2 and CO that agreed well with experimental data. This study is the first to measure, compare, and model both H2 and CO mass transfer coefficients in an HFR. Based on model predictions, HFRs have the potential to be a reactor of choice for syngas fermentation as a result of high mass transfer that can support high cell densities.

Single LiBH4 nanocrystal stochastic impacts at a micro water|ionic liquid interface

LiBH4 is often employed as a reducing agent for metal nanoparticle (NP) preparation but is inherently a solid-state H2 hydrogen storage agent. Herein it is shown, through a combination of electron/optical microscopies and single entity electrochemical study, that LiBH4 is stored in the solid state within an ionic liquid (IL) as nanocrystals (NCs). The electrochemical monitoring of an immiscible water|IL (w|IL) micro-liquid|liquid interface (LLI) shows interfacial charge exchange associated with the stochastic impacts of single NCs. Meanwhile, in situ optical monitoring of a w|metal or w|IL interface shows that such impacts are associated with the development of a H2-in-IL micro/nano-foam related to the poor solubility of H2. Both the presence of solid NCs and the latter H2-in-IL foam suggest that H2 release from LiBH4-in-IL is a slow, but likely controlled process. The rate of H2 production at a macroscopic LLI is further confirmed by gas chromatographic measurements, in very good agreement with microscopic observations. The electrochemical LLI provides unique investigative access to LiBH4 NCs and offers insight into H2 storage in ILs, or for direct borohydride fuel cells, as well as NP synthesis.

Hydrophobic Solvation of Gases (CO2, CH4, H2, Noble Gases) in Clay Interlayer Nanopores

In the past few years, experimental studies have shown that CO2 is roughly 5 times more soluble in water-saturated clay interlayer water than in bulk liquid water. The fundamental basis of this selectivity remains unknown, as does its relevance to other gases. Here, we use molecular dynamics (MD) simulations and gravimetric adsorption experiments to determine the solubilities of CO2, CH4, H2, and noble gases in clay interlayer water. Our results confirm that clay minerals, despite their well-known hygroscopic nature, have a significant hydrophobic character at the atomistic scale. The affinity of dissolved gases for the clay surface shows significant variations related to the size and shape of the adsorbing molecules and the structuring of interfacial water by clay surfaces. Our results indicate that dissolved gases likely do not behave as inert tracers in fine-grained sedimentary rocks such as shale and mudstone, as routinely assumed in groundwater hydrology studies. Our results have implications for the...

Enhanced solubility of hydrogen and carbon monoxide in propane‐ and propylene‐expanded liquids

Conventional propylene hydroformylation occurs in a gas-expanded liquid phase. Reliable knowledge of the phase equilibria of such systems, including the solubilities of CO and H2 in propylene-expanded solvents, is essential for rational process design and development. Herein, we report the vapor–liquid equilibrium (VLE) data of the following ternary systems involving CO, H2, propane, propylene, toluene and NX-795 at temperatures from 70 to 90°C and pressures up to 1.5 MPa: propane/H2/toluene, propane/CO/toluene, propylene/H2/toluene, propylene/CO/toluene, propane/H2/NX-795, propane/CO/NX-795, propylene/H2/NX-795 and propylene/CO/NX-795. The solubilities of H2 and CO in either propane-expanded or propylene-expanded phases are observed to be greater than those in the neat organic solvents, by as high as 78% at 70°C and 1.5 MPa. By modeling the vapor and the liquid phases as pseudo-binary systems, the Peng-Robinson equation of state (PR-EoS) with van der Waals’ mixing rules and binary interaction parameters is shown to satisfactorily predict the experimental VLE data. © 2017 American Institute of Chemical Engineers AIChE J, 64: 970–980, 2018

Molecular Simulation Study of the Performance of Supported Ionic Liquid Phase Materials for the Separation of Carbon Dioxide from Methane and Hydrogen

Molecular dynamics and Gibbs ensemble Monte Carlo simulations were used to compute the self-diffusion coefficients and solubilities of CO2, CH4, and H2 in model membranes consisting of slit pores with diameters of 2 and 5 nm. Solubility selectivities, diffusion selectivities, and permselectivities of CO2 for binary gas mixtures of CO2/CH4 and CO2/H2 were also computed. The calculations were repeated for the same pores filled with the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim]+[Tf2N]−) and for bulk IL. The bulk IL system was used as a model for a supported ionic liquid membrane separator having large pores, while the confined IL systems were used to assess whether extreme nanoconfinement of ILs has an effect on permselectivity. Permselectivities were about a factor of 10 higher in all the IL systems compared to the empty nanopores. Nanoconfinement tends to increase the solubility and decrease the diffusivity of all gases relative to the bulk IL. The bulk IL h...

Hydrodeoxygenation of oleic acid in hexane containing pressurized CO2 using Fe/SBA-15 as catalyst

The hydrotreatment of oleic acid in a green reaction media to produce the major hydrodeoxygenation product octadecane using a 6 wt% nano Fe loaded Fe/SBA-15 as catalyst was demonstrated in this study. The data show that hexane containing pressurized CO2 could dictate the selectivity of the hydrotreatment of oleic acid with high selectivity for hydrodeoxygenation over decarboxylation/decarbonylation. In addition, hexane containing pressurized CO2 could offer beneficial effects including reduction of viscosity of the solution and increase of H2 solubility. As a result, uniform dispersion of the catalyst occurred in the solution and the diffusion resistances were reduced as well due to the increase in mass transfer. At the best operating condition of 290 °C, 6 h, 30 bars H2 and 40 bars CO2, an octadecane yield of 83.3% and a heptadecane yield of 8.7% were observed when compared to 65% and 15%, which were the yields in the absence of CO2. The effects of three independent operation variables namely, temperature, CO2 pressure and time and their interactions on the hydrotreatment of oleic acid were studied using a central composite design and response surface methodology. The results showed that all these three variables were significant factors for increasing the yield of octadecane while CO2 pressure was the most significant variable in decreasing the yield of heptadecane, the major decarboxylation/decarbonylation product.

Thermodynamics of hydrogen absorption (desorption) in unoxidized and internally oxidized Pd–Ti alloys

Hydrogen isotherms have been measured from 273 K to 323 K in solid solution, low Ti content fcc Pd–Ti alloys over H content ranges available up to pH2≈0.10 MPa. ΔHH and ΔSH have been determined from the H2 isotherms in the dilute phase region as a function of the H content of the alloys. Thermodynamic parameters have been determined for hydride formation and decomposition reactions from the temperature dependence of the plateau pressures. Hysteresis has been determined for the alloys up to Pd0.94Ti0.06; the Pd0.92Ti0.08 alloy does not form a hydride phase at T ≥ 273 K. Alloys were internally oxidized to form composites and the H2 solubilities re-determined. The isotherms indicate H trapping at the Pd/TiO2 interfaces. The enthalpies for H trapping have been determined by reaction calorimetry for the internally oxidized Pd0.98Ti0.02 alloy and the relative partial enthalpies for absorption are quite negative compared to H2 solution in the dilute phase of pure Pd. These results probe the properties of metal/oxide interfaces which are important for a number of technological applications.

H2 solubility and mass transfer in anthraquinone working solution: Experimental and modeling study

This work was focused on the measurement of the solubility of hydrogen (H2) in anthraquinone working solution at temperatures of 30.0–80.0°C and pressures of 0.2–3.0MPa by the method of experimental and COSMO-RS model study. The influence of various factors, i.e., including pressure, temperature and solvent volume ratio, on H2 solubility was investigated. According to the experimental results, H2 solubility in anthraquinone working solution increases with the increase of pressure. At low pressures, the temperature had little effect on H2 solubility while under high pressures H2 solubility increases with increasing temperature. Henry's constant lnH has a good linear relationship with 1/T (lnH=−1319.1/T+9.91). The effect of volume ratio of trioctyl phosphate to trimethylbenzene on the solubility of hydrogen was studied and the results showed that increasing the amount of trimethylbenzene was conducive to the dissolution of hydrogen. In addition, there is a linear relationship between ln((P0−Pe)/(Pt−Pe)) and the time t. Gas–liquid mass transfer coefficient was obtained by calculating the slope of the line.

Solubilities of CO2, CH4, H2, CO and N2 in choline chloride/urea

Solubilities of CO2, CH4, H2, CO and N2 in choline chloride/urea (ChCl/Urea) were investigated at temperatures ranging from 308.2 to 328.2 K and pressures ranging from 0.6 to 4.6 MPa. The results show that the solubilities of gases increase with increasing pressure and decreasing temperature. The solubility of CO2 is higher than that of CH4, H2, CO and N2, which indicates that ChCl/Urea may be used as a potential solvent for CO2 capture from the gas mixture. Solubility of CO2 in ChCl/Urea was fitted by Non-Random Two-Liquid and Redlich–Kwong (NRTL-RK) model, and solubility of CH4, H2, CO or N2 in ChCl/Urea was fitted by Henry's Law. The standard enthalpy, standard Gibbs energy and standard entropy of gases were calculated. Additionally, the CO2/CH4 selectivities in water, dry ChCl/Urea and aqueous ChCl/Urea were further discussed.

Molecular Simulations of the Thermophysical Properties of Polyethylene Glycol Siloxane (PEGS) Solvent for Precombustion CO2 Capture

The thermophysical properties for neat polyethylene glycol siloxane solvent (PEGS) along with CO2, H2, H2O, and H2S gas absorption in PEGS at 298–373 K were investigated via molecular simulations. The predicted neat PEGS density, heat capacity, surface tension, and CO2 and H2 solubilities in PEGS solvent agree reasonably well with the experimental data, with typical differences of 0.8–20%, while the predicted PEGS solvent viscosity is 1.7–2.5 times larger than the experimental data. Gas solubility in PEGS at 298 K decreases in the following order, H2O (31000) > H2S (230) > CO2 (33) > H2 (1), which follows the same order as the gas–PEGS interaction. In contrast, gas diffusivity in PEGS at 298 K decreases in an opposite way, H2 (1) > CO2 (0.22) ≈ H2S (0.12) > H2O (0.018). The numbers in parentheses are the corresponding values relative to H2. Compared to the widely studied poly(dimethylsiloxane) (PDMS) solvent, PEGS is more hydrophilic due to its stronger interaction with H2O and fewer branched −CH3 groups,...

H2 Solubility and Mass Transfer in Diesel: An Experimental and Modeling Study

In this work, the solubility and liquid-phase mass transfer coefficient of hydrogen (H2) in catalytic diesel at temperatures (353.2–453.2 K) and pressures (1–6 MPa) were measured experimentally. The solubility increases with the increase of pressure and temperature, and the Henry’s constant follows the relation of ln H (MPa) = 2447.02/T (K) – 0.11 with temperature. The molar fraction of H2 and system pressure at different equilibrium time were measured to estimate the liquid-phase mass transfer coefficient, and the results showed that with the increase of pressure the mass transfer coefficient increases. Furthermore, the solubility of H2 in diesel was predicted by the COSMO-RS model using six virtual model compounds. Both the experimental data and predicted values agree well. Then, the solubility of H2 in several hydrocarbon components with the same carbon atom but different ratios of C to H atoms was also predicted, and the results showed that the solubility decreases with the increase of the degree of unsaturation for hydrocarbons. Moreover, the H2 solubility behavior in catalytic diesel was further explained from a molecular point of view by means of the COSMO-RS model.

Modeling the solubility and volumetric properties of H2 and heavy hydrocarbons using the simplified PC-SAFT

The solubility and volumetric properties of H2 and heavy hydrocarbons are important to the design of many chemical processes. In this paper, a simplified Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) is chosen to model the solubility and volumetric properties of H2/heavy alkanes and H2/bitumen mixtures. The number of reduced density roots given by the simplified PC-SAFT is discussed and a robust procedure is employed to solve for the root with the lowest Gibbs free energy. The development of new H2 parameters and the kij correlation of H2-heavy alkane pairs for the simplified PC-SAFT is completed using extensive experimental data. The new parameters are applied with a developed bitumen characterization method to predict H2 solubility in Athabasca Bitumen. The average absolute deviations (AADs) between the measured solubility data and the modeling results are within 0.57% for the five H2/heavy alkane systems and 0.69% for the H2/Athabasca bitumen systems. Finally, the density, thermal expansion coefficient, and compressibility of the systems are predicted over wide ranges of temperature and pressure.

Measuring Diffusion and Solubility of Slightly Soluble Gases in [CnMIM][NTf2] Ionic Liquids

We report an advanced experimental setup for the reliable determination of diffusion and solubility, especially for slightly soluble gases in ionic liquids. We were able to improve resolution and reproducibility of an isochoric saturation method by using differential pressure measurements. It was also possible to reduce the influence of wall adsorption, too. For the first time we present diffusion coefficients of hydrogen gas (H2) in the ionic liquids [EMIM][NTf2], [BMIM][NTf2], [HMIM][NTf2], and [OMIM][NTf2] at temperatures between 293.15 and 343.15 K. Henry’s Law constants were determined simultaneously by fitting the experimental pressure decay to a one-dimensional diffusion model. With rising temperature, diffusion coefficients and solubility of H2 were increased. Increasing the length of the alkyl side chain of the cation decreased diffusion, whereas solubility of H2 was increased. An empirical correlation equation for H2 diffusion in [CnMIM][NTf2] ionic liquids is presented. Limitations are also poi...

Selective absorption of CO2 from H2, O2 and N2 by 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate

Ionic liquids are promising solvents for extracting CO2 from H2, N2 and O2 using the absorption separation method. Solubilities of these gases in 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][eFAP]) were determined using an isochoric saturation method. Experimental result indicates that solubilities of H2, N2 and O2 in [HMIM][eFAP] are much lower than that of CO2. The performance of [HMIM][eFAP] in separating CO2 from N2, H2 and O2 can be improved by decreasing the temperature. Based on the solubility data, the ideal selectivities of CO2/N2, CO2/H2, and CO2/O2 in different ionic liquids were calculated and the effect of the ionic liquid structure on them were investigated.

Hydrogen permeation through Flinabe fluoride molten salts for blanket candidates

Fluoride molten salt Flibe (2LiF+BeF2) is a promising candidate for the liquid blanket of a nuclear fusion reactor, because of its large advantages of tritium breeding ratio and heat-transfer fluid. Since its melting point is higher than other liquid candidates, another new fluoride molten salt Flinabe (LiF+NaF+BeF2) is recently focused on because of its lower melting point while holding proper breeding properties. In this experiment, hydrogen permeation behavior through the three molten salts of Flibe (2LiF+BeF2), Fnabe (NaF+BeF2) and Flinabe are investigated in order to clarify the effects of their compositions on hydrogen transfer properties. After making up any of the three molten salts and purifying it using HF, hydrogen permeability, diffusivity and solubility of the molten salts are determined experimentally by using a system composed of tertiary cylindrical tubes. Close agreement is obtained between experimental data and analytical solutions. H2 permeability, diffusivity and solubility are correlated as a function of temperature and are compared among the three molten salts.