Phase Equilibria of Clathrate Hydrates of Ethane + Ethene

Abstract

Dissociation conditions for simple and mixed hydrates of ethane and ethene (ethylene) have been measured using the isochoric pressure-search technique. Simple hydrate dissociation data for ethane and ethene measured in this work are compared to existing literature data. The agreement between the measured ethane hydrate dissociation data with the literature data is acceptable while some deviations between the measured ethene hydrate dissociation data and those reported in the literature are observed. All new data for simple and mixed hydrates of ethene and ethane are well-correlated using an empirical correlation proposed by Adisasmito and coworkers. However, agreement between the experimental data with the predictions of the CSMGem model is found to be unsatisfactory. A gas chromatography technique combined with the isochoric-pressure search method is used to measure composition of the vapor phase in equilibrium with the hydrate and aqueous phases inside the hydrate stability region. The feed compositions investigated were 0.174, 0.420, and 0.810 mole fractions of ethane. In addition, dissociation points were found to be in the vicinity of the ethane hydrate dissociation conditions regardless of the initial content of ethane in the feed. It was also found that temperature does not have a considerable effect on ethane content of the vapor phase in equilibrium with hydrate and aqueous phases inside the hydrate stability region at given pressures.

Thermodynamic model of phase equilibria of tetrabutyl ammonium halide (fluoride, chloride, or bromide) plus methane or carbon dioxide semiclathrate hydrates

“…Gas hydrate was regarded as the reason for blockage of natural gas transportation pipelines [2] since 1934. In modern society, more attention was focused on gas hydrate, as it became a promising medium for many positive applications, such as gas storage [3,4], gas separation [5,6], energy storage [7], water desalination [8], separation of close-boiling point compounds [9][10][11][12] and so on. However, the condition of high pressure and low temperature required for the hydrate formation is one of the greatest obstacles to realize these hydrate-based technologies.…”

Thermodynamic modeling of phase equilibrium of carbon dioxide clathrate hydrate in aqueous solutions of promoters and inhibitors suitable for gas separation

“…Thus, by maintaining desired pressure and temperature conditions during gas hydrate formation (which is primarily based on the phase behavior), one can separate gases such as CO 2 and H 2 S from flue gas mixtures. Semiclathrate hydrates (SCH) are derivatives of gas hydrate in which the cage‐like crystal structure are formed by the water molecules and anions of tetra‐ n ‐alkyl ammonium/alkyl phosphonium halides (TBAX; X = bromide (Br), chloride (Cl), fluoride (F)) . For example, tetra‐ n ‐alkyl ammonium bromide (TBAB) semiclathrate typically was observed to form at 12°C and at 1 atm, which is higher than the conventional gas hydrate formation temperature at the same pressure .…”

“…For example, tetra‐ n ‐alkyl ammonium bromide (TBAB) semiclathrate typically was observed to form at 12°C and at 1 atm, which is higher than the conventional gas hydrate formation temperature at the same pressure . Semiclathrate hydrate of CO 2 has shown importance in various technological applications as similar to gas hydrate as mentioned previously . In semiclathrate hydrate, the Br − molecules take part in the formation of hydrate cages, while tetra n ‐alkyl ammonium cation (TBA + ) encapsulates into the hydrate structure, and improve the formation pressure and temperature conditions …”

“…Gas hydrates, or clathrate hydrates, are ice‐like crystalline structures that are formed due to inclusion of the ‘guest’ (gas) molecule, such as methane (CH 4 ), ethane (C 2 H 6 ,), carbon dioxide (CO 2 ), nitrogen (N 2 ), and hydrogen sulfide (H 2 S), in the cages formed by the host (water) molecule under suitable pressure and temperature conditions . Gas hydrate has many technological applications in industrial processes such as gas separation, cold storage, CO 2 capture, gas storage, and transportation and for energy recovery . The separation of gases from the multicomponent gas mixture is based on the fact that each gas molecule in the mixture forms hydrate at different pressure and temperature conditions.…”

Continuous separation of CH4/N2 mixture via hydrates formation in the presence of TBAB

“…Hydrates have the potential for many industrial applications: flow assurance in petroleum industry [13][14][15][16], CO 2 capture and sequestration [17][18][19][20][21][22], separation of close-boiling point compounds [23][24][25], water desalination [26], gas (H 2 and CH 4 ) storage [27][28][29], refrigeration and cool storage [30][31][32].…”