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

Muhammad Saad Khan; Alamin Idris; Jai Krishna Sahith Sayani; Bhajan Lal; Iqbal Ahmed Moujdin; Khalik M Sabil

doi:10.1016/j.chemosphere.2022.136102

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

Chemosphere. 2022 Nov;307(Pt 4):136102. doi: 10.1016/j.chemosphere.2022.136102. Epub 2022 Aug 22.

Authors

Muhammad Saad Khan¹, Alamin Idris², Jai Krishna Sahith Sayani³, Bhajan Lal⁴, Iqbal Ahmed Moujdin⁵, Khalik M Sabil⁶

Affiliations

¹ CO(2) Research Center, Universiti Teknologi PETRONAS, Bander Seri Iskander, Perak, Malaysia. Electronic address: muhammad.saad@utp.edu.my.
² Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden; MoRe Research Örnsköldsvik AB, Örnsköldsvik, Sweden.
³ CO(2) Research Center, Universiti Teknologi PETRONAS, Bander Seri Iskander, Perak, Malaysia; School of Chemical & Bioprocess Engineering, University College Dublin, Ireland.
⁴ CO(2) Research Center, Universiti Teknologi PETRONAS, Bander Seri Iskander, Perak, Malaysia; Chemical Engineering Department, Universiti Teknologi PETRONAS, Bander Seri Iskander, Perak, Malaysia. Electronic address: bhajan.lal@utp.edu.my.
⁵ Mechanical Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia.
⁶ PETRONAS Research Sdn Bhd, Bangi, Selangor, Malaysia.

PMID: 36007731
DOI: 10.1016/j.chemosphere.2022.136102

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 (ΔŦ) 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 ΔŦ due to a decrease in hydrogen bonding ability. The highest THI inhibition (ΔŦ = 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.

Keywords: Average depression temperature; CH(4) hydrates; CO(2) hydrates; Freezing point depression; Hydrogen bonding energy; Mixed gas hydrates; THI.