Experimental Data on Phase Behavior of Simple Tetrabutylphosphonium Bromide (TBPB) and Mixed CO₂+ TBPB Semiclathrate Hydrates

Abstract

The phase behavior of simple and mixed semiclathrate hydrates formed from CO2 + tetrabutylphosphonium bromide (TBPB) + water mixtures was investigated by pressure-controlled differential scanning calorimetry (DSC) at TBPB concentrations in the range of 0 to 0.073 mole fraction and at CO2 pressure in the range of (0 to 2.0) MPa. In a previous article we demonstrated that TBPB + CO2 mixed hydrates present high dissociation enthalpies and could be used as phase change material, covering the range of temperature from (284.6 to 289.0) K, for secondary refrigeration applications. The present work investigates a broader domain of compositions, resulting in x–T phase diagrams at atmospheric conditions and at various CO2 pressures. These data are required to model the potential latent heat of hydrate slurries as a function of gas pressure and aqueous phase composition over the whole range of interest for refrigeration purposes. The results presented show that adding TBPB to the water at low concentration (0.0058 mole fraction) decreases the pressure of formation of CO2 hydrates to 0.5 MPa at 281.6 K, instead of 3.5 MPa at the same temperature in the absence of a promoter. Crystallization of CO2 + TBPB hydrate could therefore offer an attractive means of capture for CO2.

Modeling of the dissociation conditions of H 2 + CO 2 semiclathrate hydrate formed with TBAB, TBAC, TBAF, TBPB, and TBNO 3 salts. Application to CO 2 capture from syngas

“…5. Note that the experimental data of Deschamps and Dalmazzone [15] are at lower temperatures than other data from the literature [9,20,36,54,55] at w TBPB ¼ 0.37. Here, ε cell ij is fitted to the experimental data of Fujisawa et al [56].…”

Dissociation behaviour of (tetra-n-butylammonium bromide + tetra-n-butylammonium chloride) mixed semiclathrate hydrate systems

“…For example, the following dissociation temperatures have been reported in ascending order of size: T = 301 K for TBAF and TBA hydroxide hydrates [7,14,15], T = 288 K for TBA chloride (TBAC) hydrate [3,11], and T = $286 K for TBAB hydrate [9][10][11]. Such semiclathrate hydrates can be stable at temperatures between T = (273 and 300) K, and are capable of trapping small gas molecules (e.g., H 2 , CH 4 , CO 2 , and N 2 ) under milder conditions than those required for the corresponding pure gas hydrate (e.g., [16] storage materials have been carried out by many research groups (e.g., [16][17][18][19][20][21][22][23][24][25]). In particular, fundamental and applied studies on TBAB hydrates have been conducted in detail because of the relatively noncorrosive nature of this hydrate system.…”

Equilibrium Conditions for Semiclathrate Hydrates Formed with CO2, N2, or CH4 in the Presence of Tri-n-butylphosphine Oxide

“…Unlike ordinary hydrates having well defined structures (Structure I, Structure II, and Structure H), SCHs have diverse structures and have hydrogen-bonding interaction between guests and hosts molecules, which is much stronger than the van der Waals force in ordinary hydrates 5 SCHs have drawn increasingly more interest from researchers for their potential applications in hydrogen storage 8 , carbon dioxide storage 9 , and gas separation [10][11][12][13][14] . The thermodynamic data of SCHs are limited, and the majority of them are for TBAB 8,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] . More phase equilibrium data on SCHs are needed for acquiring in-depth knowledge of gas hydrate formation, optimizing the thermodynamic models, and developing effective gas processing technologies.…”