Phase Equilibria of Double Semiclathrate Hydrates Formed with Tetraamylammonium Bromide Plus CH₄, CO₂, or N₂

Abstract

Dissociation data for the semiclathrate hydrates formed with tetraamylammonium bromide (TAAB: C 20 H 44 NBr) + CH 4 , + CO 2 , or + N 2 were measured in the pressure range of (1.33 to 20.37) MPa and temperature range of (279.8 to 291.9) K at (0.050 and 0.100) mass fraction of TAAB. The experimental data were obtained by employing an isochoric pressure-search method. The results showed that at a given pressure, the temperature required to form double TAAB + CH 4 , + CO 2 , or + N 2 hydrates was higher than that required for the corresponding pure CH 4 , CO 2 , or N 2 hydrates, and as the TAAB concentration increased, its effect of enlarging the hydrate stability zone was strengthened. However, the experimental dissociation temperatures for double semiclathrate hydrates were lower than those for TAAB hydrates formed without guest gases. In addition, the data for double semiclathrate hydrates formed from TAAB generated in this work were compared with those formed from some other semiclathrate hydrate formers (such as tetrabutylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium fluoride) reported in literature.

Experimental Determination of Gas Hydrates Dissociation Conditions in CO2/N2 + Ethanol/1-Propanol/TBAB/TBAF + Water Systems

“…In 2008, Sloan and Koh published several experimental and modeling studies for hydrate properties containing pure and mixed guest gas molecules, according to this study and briefly, the experimental equipment for high-pressure phase equilibria (macroscopic measurements) can be classified as follows: high pressure “visual” cell, − high pressure “blind” cell, − quartz crystal, microbalance (QCM) in a high pressure cell, , cailletet, , rocking cell, , and high-pressure differential scanning calorimetry. , On the other hand, according to the classification of Dohrn et al, there are two main classes of experimental methods for high pressure phase equilibria, depending on how the compositions of the equilibrium phases are determined and whether the mixture under study has been prepared with well-known initial composition (analytical methods and synthetic methods).…”

Phase Equilibrium of Methane Hydrate in the Presence of Aqueous Solutions of Quaternary Ammonium Salts

“…The reason for getting different phase behavior for different methane hydrate + QAS systems may be due to guest and host interactions, change in the activity of water due to TBAB present in an aqueous solution, and formation of unusual water cages by larger TBAB guest molecules than the TMAB and TEAB systems. 6 In a recent study by Su and co-workers, 20 the methane hydrate inhibition in the presence of TMAB and TEAB is accounted for by considering it as a colligative property. It has been said that the methane hydrate inhibition in the presence of TMAB and TEAB aqueous systems is similar to that of NaCl.…”

“…As said above, there is a minor effect of alkyl chain length of QAS (such as, TMAB to TEAB) on methane hydrate inhibition, this observation is in-line with some of the literature observations on the effect of alkyl chain length of ionic liquids on the phase equilibrium of methane hydrate system, which indicate that the shorter alkyl chain length of ionic liquids inhibit hydrate more than the longer alkyl chain length ionic liquids. − It can also be observed from Figures a and b that TBAB has a pronounced promotion effect on methane hydrate system and forms a reasonably stable hydrate at higher temperature and lower pressure conditions. The reason for getting different phase behavior for different methane hydrate + QAS systems may be due to guest and host interactions, change in the activity of water due to TBAB present in an aqueous solution, and formation of unusual water cages by larger TBAB guest molecules than the TMAB and TEAB systems . In a recent study by Su and co-workers, the methane hydrate inhibition in the presence of TMAB and TEAB is accounted for by considering it as a colligative property.…”

“…Gas hydrates have been recognized as a nuisance to the oil and gas industry as they form in the oil and gas pipelines restricting the fluid flow thereby increasing flow assurance issues . With the advent of research, gas hydrates may also play a vital role in numerous industrial applications such as natural gas storage, multicomponent gas separation, seawater desalination, carbon dioxide sequestration, and air conditioning applications. − …”

Effects of multiwalled carbon nanotubes on CH4 hydrate in the presence of tetra-n-butyl ammonium bromide

“…Recently, many researchers have focused on semiclathrate hydrates owing to their possible applications in gas storage and transportation, gas separation, etc. [5][6][7][8] Hydrate technology, as an emerging approach for solidifying natural gas, is considered an alternative to liqueed natural gas (LNG) or compressed natural gas (CNG) technologies for natural gas storage and transportation. 9 The application of hydrate technology to gas storage and transportation has several advantages compared with CNG and LNG, including lower cost, improved safety, and higher efficiency.…”