Phase Equilibria and Dissociation Enthalpies of Tri-n-butylphosphine Oxide Semiclathrate Hydrates Incorporated with CH4, CO2, and H2

Cha, Jong-Ho; Kim, Eun Sung; Lee, Ki Sun; Kang, Jeong Won; Kim, Ki-Sub

doi:10.1021/je400773k

Cited by 12 publications

(7 citation statements)

References 18 publications

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“…The temperature range of TBPO + CH 4 double hydrate preparation is limited by the dissociation temperature of TBPO + CH 4 hydrate, ∼296 K, and the melting point of the eutectic mixture in the TBPO–H 2 O system, ∼272.9 K . The synthesis of the double TBPO + CH 4 hydrates was carried out at a methane pressure of 8.5 ± 0.5 MPa and temperature of 274 ± 1 K that is somewhat higher than the eutectic melting point.…”

Section: Results and Discussionmentioning

confidence: 99%

“…It has been suggested that several hydrates can be formed in the system, and TBPO·28H 2 O was previously reported as their averaged composition. Most recently reported data on P , T hydrate phase equilibria for aqueous solutions of TBPO + CH 4 , , + CO 2 , , + N 2 , + H 2 , + simulated biogas (60 mol % CH 4 + 40 mol % CO 2 ), + simulated mine ventilation air (0.5 vol % CH 4 + 99.5 vol % air), + simulated flue gas (12.5 vol % CO 2 + 80.5 vol % N 2 + 6.9 vol % O 2 ) showed a shift of the hydrate phase equilibria to lower pressures and higher temperatures, compared to the corresponding gas + water system. These observations are evidence of the inclusion of gas molecules into the cavities of the TBPO hydrate structure.…”

Section: Introductionmentioning

confidence: 98%

“…The temperature range of TBPO + CH 4 double hydrate preparation is limited by the dissociation temperature of TBPO + CH 4 hydrate, ∼296 K, 32 and the melting point of the eutectic mixture in the TBPO−H 2 O system, ∼272.9 K. 30 The synthesis of the double TBPO + CH 4 hydrates was carried out at a methane pressure of 8.5 ± 0.5 MPa and temperature of 274 ± 1 K that is somewhat higher than the eutectic melting point. The maximal subcooling temperature is ∼22 K. The results of the measurements of methane volumes in dependence on the initial Thus, the PXRD data confirmed our interpretation of the single-and two-stage gas evolution curves.…”

Section: ■ Introductionmentioning

confidence: 99%

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Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

et al. 2017

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In the present work, we studied semiclathrate hydrates in the TBPO-HO and TBPO-HO-CH systems. The stoichiometry, temperature, and enthalpy of dissociation of TBPO semiclathrate hydrate crystals formed in the TBPO-HO binary system were found to be TBPO·33.6 ± 0.9HO, 280.0 K, and 253.1 ± 4.7 J g, respectively. The crystal structure determined by single crystal XRD analysis (150 K) was the orthorhombic with space group Pbam and unit cell parameters a = 19.9313(8) Å, b = 23.4660(7) Å, and c = 12.1127(5) Å. The structural stoichiometry is TBPO·34.5HO. The TBPO guest molecules arrangement within the host water framework has been refined for the first time. The discrepancy between the analytically measured and structural stoichiometry is likely to be attributed to the structure defects, which cannot be revealed by the routine single-crystal XRD analysis. The methane capacity of TBPO + CH double hydrate was measured by the thermovolumetric method in the range 14.9-55.8 wt % TBPO aqueous solution at a methane pressure of 8.5 ± 0.5 MPa and temperature of 274 ± 1 and 286 ± 1 K. The maximum included methane volumes of 61.6-74.6 mL/g were observed for the TBPO + CH double hydrates synthesized from ∼26-30 wt % TBPO aqueous solutions. Powder X-ray diffraction measurements of the hydrate samples used in the thermovolumetric experiments revealed that the TBPO + CH double hydrate has the same structural characteristics as the simple TBPO hydrate. The study of the Raman spectra of the TBPO + CH double hydrate and TBPO simple hydrate showed that in the TBPO + CH double hydrate CH molecules selectively occupy the small D cages. The results of the present study did not confirm the earlier suggestion of the formation of several structural types of hydrates in the TBPO-HO system. The obtained results indicate that the TBPO-HO binary system has a potential for application in gas separation and as cold storage and transportation media.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: ■ Introductionmentioning

confidence: 99%

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Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

et al. 2017

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“…In the present work, the phase equilibrium conditions of ventilation air methane hydrate and ventilation air methane + TBAB or TBPO semi-clathrate hydrate at 5 wt%, 15 wt% and 26 wt% are tabulated in Table 1 [30,33]. Note also that with increasing the initial loading from 5 wt% to 26 wt%, the gap between the TBAB and TBPO curves became smaller as the pressure requirement for the formation of ventilation air methane hydrate was not sensitive to the initial TBPO loading but to the initial TBAB loading.…”

Section: Thermodynamic Stability Conditionsmentioning

confidence: 99%

Thermodynamic stability conditions, methane enrichment, and gas uptake of ionic clathrate hydrates of mine ventilation air

Wang

2015

Chemical Engineering Journal

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Abatement of methane from mine ventilation air (MVA) is a significant challenge faced by coal mining industry. A promising method for methane capture from gas mixture is clathrate hydrate formation. In search of suitable and costeffective low-dosage promoters for hydrate-based methane capture processes, this paper reports the pressure requirement for the hydrate formation of simulated MVA (0.5 vol% CH 4 + 99.5 vol% air) and its potential for methane extraction, in the presence of tri-n-butyl phosphine oxide (TBPO) or tetra-n-butyl ammonium bromide (TBAB) at three different initial loadings (5 wt%, 15 wt%, and 26 wt%). An isochoric equilibrium step-heating pressure search method was used to measure the hydrate phase equilibrium conditions at the temperature range of (277.61 to 295.54) K and pressure range of (0.23 to 19.11) MPa. It was found that at a given initial loading, TBPO was largely more effective than TBAB in reducing the pressure requirement for hydrate formation of MVA. At a given temperature, the equilibrium pressures of the clathrate hydrates were indifferent to the change in the initial loading of TBPO from 5 wt% to 26 wt%, in contrast to those of TBAB. Gas composition analysis by gas chromatography confirmed that CH 4 could be significantly enriched in the ionic clathrate hydrates, and the highest methane enrichment ratio obtained in the present work was 300%, with TBPO at initial loading of 5 wt%. At this relatively low loading, within a given period of 5 hours, TBPO also led to higher gas uptake compared with TBAB. The advantages of TBPO as a promoter of MVA hydrate were discussed.

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“…Due to the vast quantity of methane contained in these hydrates, they have been considered a new source of hydrocarbon energy for future. Gas hydrates have also received much attention as new media for energy gas storage, transportation, − and greenhouse gas separation − and as phase changing materials for refrigeration and air conditioning. − Additionally, the hydrate formation has been proposed as an alternative technique in desalinating seawater or frac water to produce fresh water. − At the same time, the undesired formation of gas hydrates is known to be a serious problem in the gas and oil industry . In subsea production, gas hydrates form deposits in pipelines and cause plugging of the pipelines or other processing equipment.…”

Section: Introductionmentioning

confidence: 99%

Experimental Measurement of Phase Equilibrium of Hydrate in Water + Ionic Liquid + CH₄ System

Cha

Han

et al. 2015

J. Chem. Eng. Data

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With the goal of discovering a more effective type of thermodynamic hydrate inhibitors (THIs), the phase equilibrium conditions of CH 4 hydrates were examined in the presence of morpholinium and piperidinium ionic liquids (ILs) at a mass fraction of 0.1. It was observed that the addition of ILs shifted the hydrate equilibrium conditions toward higher pressure and lower temperature compared with those of hydrates formed from pure water. Both cationic and anionic species influenced the equilibrium conditions of the CH 4 hydrate. The piperidinium ILs showed better inhibition effect than did the morpholinium ILs at the same species of counteranions. The result may be due to the more hydrophobic nature of piperidinium ILs, which have a higher affinity for CH 4 molecules. It was also seen that the inhibition effect of BF 4 − ions was stronger than that of Br − ions for both piperidinium and morpholinium ILs. Thus, the inhibition effect became stronger in the order:). The best among these ILs had inhibition effectiveness comparable with ethylene glycol and triethylene glycol, which are used commercially as THIs.

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Phase Equilibria and Dissociation Enthalpies of Tri-n-butylphosphine Oxide Semiclathrate Hydrates Incorporated with CH₄, CO₂, and H₂

Cited by 12 publications

References 18 publications

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

Thermodynamic stability conditions, methane enrichment, and gas uptake of ionic clathrate hydrates of mine ventilation air

Experimental Measurement of Phase Equilibrium of Hydrate in Water + Ionic Liquid + CH₄ System

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Phase Equilibria and Dissociation Enthalpies of Tri-n-butylphosphine Oxide Semiclathrate Hydrates Incorporated with CH4, CO2, and H2

Cited by 12 publications

References 18 publications

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

Thermodynamic stability conditions, methane enrichment, and gas uptake of ionic clathrate hydrates of mine ventilation air

Experimental Measurement of Phase Equilibrium of Hydrate in Water + Ionic Liquid + CH4 System

Contact Info

Product

Resources

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Phase Equilibria and Dissociation Enthalpies of Tri-n-butylphosphine Oxide Semiclathrate Hydrates Incorporated with CH₄, CO₂, and H₂

Experimental Measurement of Phase Equilibrium of Hydrate in Water + Ionic Liquid + CH₄ System