Hydrate Plug Prevention by Quaternary Ammonium Salts

The use of low-dosage inhibitors is an alternative to thermodynamic inhibitors to prevent gas hydrates from plugging oil production pipelines. In this work, quaternary ammonium salts (QAs) with different structures were tested as hydrate plug inhibitors on model systems containing 1/1/4/X proportions (by weight) of water/THF/oil/QA systems. The experimental results suggest that the presence of both small (CH3) groups in their polar moiety and two long alkyl chains in their hydrophobic part has a beneficial effect on their ability to adsorb onto the hydrate surface and form a steric barrier around the hydrate crystals, which limits their agglomeration to larger masses. Above a minimum concentration, the concentration of the double-tailed QAs has no appreciable effect on their ability to prevent hydrates from plugging. Their effectiveness as hydrate plug inhibitors is not dependent on the chain length of the oil.