Hydrate Equilibrium Conditions for Tetra- n -butyl Ammonium Bromide

The equilibrium pressure–temperature relations of the tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate were measured at pressures of up to 80 MPa by high-pressure differential scanning calorimetry. As a pressurizing medium, tetrafluoromethane (CF4), which cannot occupy any hydrate cages in the TBAB semiclathrate hydrate at the present experimental pressures, was used. The dissociation temperature of tetragonal TBAB semiclathrate hydrate (TBAB·26H2O) increases with the increase in pressure, whereas the dissociation enthalpy is (192 ± 3) J·g–1 and almost constant at pressures of up to 80 MPa. The temperature difference between formation and dissociation at the same pressure, that is, the maximum allowable degree of supercooling, is (17.7 ± 0.7) K and independent of the pressure.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dissociation and Nucleation of Tetra-n-butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures

Sugahara

Machida

2017

“…Quaternary ammonium salts (QASs), such as tetrabutylammonium bromide (TBAB) − and tetrabutylammonium chloride (TBAC), ,− are SCH formers and could form SCHs with water molecules. The structure of these SCHs is characterized by the polyhedral water–anion host lattice, built by water molecules together with halide anions through hydrogen bonding, encaging the butyl groups in large cages and typically leaving small dodecahedral cages (5) vacant to store or capture small gas molecules. − Presently, many studies focusing on the thermodynamic stability of SCHs at ambient pressure have been reported.…”

Section: Introductionmentioning

confidence: 99%

Dissociation Temperatures of Mixed Semiclathrate Hydrates Formed with Tetrabutylammonium Bromide Plus Tetrabutylammonium Chloride

Shi¹,

Yi²,

Shen

et al. 2016

Dissociation temperatures of mixed tetrabutylammonium bromide (TBAB) + tetrabutylammonium chloride (TBAC) semiclathrate hydrates were determined by using the DSC technique. The system was measured in five groups with a fixed total mole fraction (x = 0.0100, 0.0200, and 0.0337), TBAB mole fraction (x TBAB = 0.0370) or TBAC mole fraction (x TBAC = 0.0337). The obtained results demonstrated that at a given x, the dissociation temperatures of mixed (TBAB + TBAC) semiclathrate hydrates were all higher than that of pure TBAB hydrate, and the maximum dissociation temperature appeared at x TBAB /x = 0.25 instead of x TBAB /x = 0 or 1 (corresponding to pure TBAC or TBAB hydrate). In addition, for systems with fixed x TBAB or x TBAC , TBAC gained the control of forming TBAC semiclathrate hydrate preferentially.

“…Semiclathrate hydrate formers comprise of a large number of ammonium salts, phosphonium salts, sulfonium salts, and amines. Tetrabutlyammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), tetrabutylammonium fluoride (TBAF), tetrabutylphosphonium bromide (TBPB), and tetrabutylphosphonium chloride (TBPC) , are widely used for semiclathrate hydrate formation. Semiclathrate hydrate, similar to clathrate hydrates, possesses many of the physical and structural properties as common clathrate hydrate, while it has particular features.…”

Section: Introductionmentioning

confidence: 99%

Stability Conditions for Semiclathrate Hydrates Formed with Tetrabutylammonium Chloride + Tetrabutylphosphonium Chloride + CH₄

Shi

et al. 2021

Semiclathrate hydrate is a promising method to ease the thermodynamic conditions of gas hydrate formation for hydrate-based gas storage and transportation on the industrial scale. The phase equilibrium conditions of mixed semiclathrate hydrate formed with tetrabutylammonium chloride (TBAC) + tetrabutylphosphonium chloride (TBPC) + CH4 were measured systematically by employing the isochoric pressure-search method. The data revealed that mixed TBAC + TBPC exerted relatively higher stabilization effect on CH4 hydrate than pure TBAC or TBPC, and the strongest stabilization effect showed up in system with 0.0300 total salt mole fraction (x salt) and 0.75 TBAC salt ratio (x TBAC/x salt). In addition, the dissociation enthalpies of mixed (TBAC + TBPC + CH4) hydrate were calculated with the obtained experimental data by using the simplified Clausius–Clapeyron equation and the Peng–Robinson equation of state. It was found that the mean dissociation enthalpies for mixed (TBAC + TBPC + CH4) hydrate with different salt concentration relied on a (153.04 to 203.92 kJ/molCH4) scale, which was significantly higher than that of the pure CH4 hydrate. The data generated in this work showed that mixed TBAC + TBPC could enhance CH4 hydrate stability and the stored energy effectively.