Effect of ammonium hydroxide-based ionic liquids' freezing point and hydrogen bonding on suppression temperature of different gas hydrates. (November 2022)

• Record Type: Journal Article
• Authors: Khan, Muhammad Saad; Idris, Alamin; Sahith Sayani, Jai Krishna; Lal, Bhajan; Moujdin, Iqbal Ahmed; Sabil, Khalik M.
• Is Part Of: Chemosphere. Volume 307:Part 4(2022)
• Publication Date: 2022-11
• Subjects: Average depression temperature -- CH4 hydrates -- CO2 hydrates -- Freezing point depression -- Hydrogen bonding energy -- Mixed gas hydrates -- THI; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.136102
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The study presents the effect of freezing point depression and hydrogen bonding energy interaction on four ammonium hydroxide-based ionic liquids (AHILs) of gas hydrate systems. The AHILs investigated are tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. The considered hydrate system includes methane (CH4 ), carbon dioxide (CO2 ), and three binary mixed gas hydrates (70-30 CO2 + CH4, 50-50 CO2 + CH4, 30–70 CO2 + CH4 ), which are often encountered in the flow assurance pipelines. The experimental temperature range is between 274.0 and 285.0 K, corresponding to pipeline pressures for different gas systems. The thermodynamic influence, i.e., average suppression temperature (Δ Ŧ) of the studied system, was reported for different mass concentrations (1, 5, and 10 wt%) and correlated with the freezing point depression and hydrogen bonding energy interaction of AHILs. The study also covers the structural impact of AHILs (in the form of alkyl chain variation) on the thermodynamic hydrate inhibition (THI) behaviour via freezing point and hydrogen bonding energy interactions. Findings revealed that the increased alkyl chain length of AHILs reduced the Δ Ŧ due to a decrease in hydrogen bonding ability. The highest THI inhibition (Δ Ŧ = 2.27 K) is attained from the lower alkyl chain AHIL, i.e., TMAOH (10 wt%) for the CO2 hydrate system. The freezing point depression of AHILs is a concentration-dependent phenomenon. Increased concentration of the AHILs in the system yielded lower freezing point temperature, positively influencing hydrate mitigation. Although the study provided the initial insight between the freezing point tendency and hydrogen bonding energies of AHILs on thermodynamic inhibition (ΔŦ). Based on the freezing point depression and hydrogen bonding energy interaction, a more generalized correlation should be developed to predict any potential ionic liquids regarded as promising hydrate inhibitors. Graphical abstract: Image 1 Highlights: THI behaviour of 4 AHILs is evaluated at different concentrations for CO2 and CH4 and three binary mixed gas hydrates. Impact of E HB of AHILs on hydrate mitigation is investigated for CO2, CH4 and three binary mixed gas hydrates. Impact of freezing point depression of AHILs is investigated for CO2, CH4 and three binary mixed gas hydrates.