Morpholine-Induced Thermodynamic and Kinetic Inhibitions on Gas Hydrate Formation

Abstract

The unexpected formation of gas hydrates during production and transportation processes in petroleum industries is known as a serious problem. To deal with this problem, the oil and gas industry has been searching for hydrate inhibitors that have great performance and cost effectiveness. Recently, ionic liquids (ILs) have been suggested as novel hydrate inhibitors that are able to act in both thermodynamic and kinetic ways (so-called dual-function inhibitors). In this paper, we suggest a non-ionic liquid compound, morpholine, as a dual-function inhibitor by measuring hydrate-phase equilibria and a series of microscopic analyses [powder X-ray diffraction, solid-state C-13 nuclear magnetic resonance (NMR), and Raman spectroscopy]. Moreover, the formation kinetics of gas hydrates in the presence of morpholine was found to be better than two comparators, 1-ethyl-3-methylimidazolium tetrafluoroborate and polyvinylpyrrolidone. Such inhibition effects of morpholine are thought to be mainly attributed to the nucleophilicity of the ring compound forming hydrogen bonds between surrounding water molecules.