Carboxylate Surfactants as Efficient and Renewable Promoters for Methane Hydrate Formation

Abstract

Carboxylate surfactants derived from hydrolysis of a renewable triglyceride were adopted as promoters in the synthesis of methane hydrate. The paper investigated the effects of surfactant carbon chain length, different counter ions, salt concentration, and additives on the promotion. It was found that sodium laurate (SL) exhibited better performance than the other surfactants, i.e., sodium decanoate (SD), sodium myristate (SM), sodium palmitate (SP), and sodium oleate (SO). At 4 mmol/L SL, the gas-storage capacity could reach 144 (v/v, the volume of methane stored by one volume of hydrate) during an induction time as short as 17 min. The decomposition of methane hydrate with SL as a promoter could avoid surfactant loss and make its recycling feasible because there was nearly no foam produced. Though sodium chloride, alcohols, and alkane could make the SL solution more surface-active, they have no obvious or even negative effect on methane hydrate formation. The high methane-storage capacity, short reaction time, and no foam generation during hydrate decomposition make SL a promising promoter to be used in large-scale applications.

Sulfonated Castor Oil as an Efficient Biosurfactant for Improving Methane Storage in Clathrate Hydrates

“…However, the rate of hydrate formation and the high degree of conversion of water to hydrate are critical technological parameters for hydrate-based technology . Thus, kinetic GHPs can be more effective because they increase the hydrate formation rate without affecting thermodynamics conditions, leaving the hydrate structure unchanged. , Anionic, cationic, and nonionic surfactants, ,, proteins, amino acids, − some ionic liquids, metal nanoparticles, − and such natural compounds as starches, cyclodextrin, and derivatives of celluloses are the most studied kinetic GHPs. These promoters particularly reduce the formation time of gas hydrates (nucleation time) and increase the growth rate of hydrate crystals. , …”

Dual Promotion–Inhibition Effects of Novel Ethylenediaminetetraacetic Acid Bisamides on Methane Hydrate Formation for Gas Storage and Flow Assurance Applications

“…Today, the storage and transportation of natural gas in the form of gas hydrates is a promising alternative to the technologies discussed above because of some of the inherent advantages listed below: − (1) the process of hydrate formation is environmentally friendly because only water, gas, and a small amount of the gas hydrate promoter (GHP) are present in the system; (2) gas molecules are easily recovered from a hydrate by reducing pressure or heating; (3) moderate temperature and pressure are required for the formation and storage of the gas hydrate (in the presence of a promoter); (4) relatively high energy content per unit volume; and (5) because gas hydrates are not explosive, this method of gas storage is safe. On the other hand, gas hydrates can be used as materials for cold storage because of the high latent heat, separation of gas mixtures, and desalination of seawater. − To implement this technology, it is necessary to control the kinetics of hydrate formation and decomposition by adding appropriate GHPs. − Promoters are classified into two different families, namely, thermodynamic and kinetic GHPs. Tetrahydrofuran, cyclopentane, iodomethane, 1,4-dioxane, and 1,3-dioxolane are the main thermodynamic GHPs. , Kinetic GHPs are more diverse, such as surfactants (anionic, cationic, and nonionic), ,− protein, amino acids, − some ionic liquids, and derivatives of celluloses, cyclodextrin, and starches .…”

“…On the other hand, gas hydrates can be used as materials for cold storage because of the high latent heat, separation of gas mixtures, and desalination of seawater. − To implement this technology, it is necessary to control the kinetics of hydrate formation and decomposition by adding appropriate GHPs. − Promoters are classified into two different families, namely, thermodynamic and kinetic GHPs. Tetrahydrofuran, cyclopentane, iodomethane, 1,4-dioxane, and 1,3-dioxolane are the main thermodynamic GHPs. , Kinetic GHPs are more diverse, such as surfactants (anionic, cationic, and nonionic), ,− protein, amino acids, − some ionic liquids, and derivatives of celluloses, cyclodextrin, and starches . Moreover, nanoparticles, oxides of various metals, and nanoiron oxide coated with surfactant sodium dodecyl sulfate (SDS) are well-known heterogeneous GHPs. − However, it should be noted that the GHPs described above showed several negative properties, such as toxicity, high foam formation during gas recovery, and low storage stability.…”

“…The literature reveals that the GHP candidate should contain two types of functional groups. The first one is a polar group such as sulfonate, sulfate, hydroxyl, amine, amide, and so on to interact with water molecules and guarantee its solubility in water. ,, The second type of effective group is an alkyl chain. ,, In this regard, the present work was devoted to investigating the effect of the different alky chains (C3-C6) on the promotion or inhibition activity of EDTAM bisamides for gas storage and flow assurance applications.…”