Study on the Synergistic Properties of Quaternary Phosphonium Bromide Salts with N-Vinylcaprolactam Based Kinetic Hydrate Inhibitor Polymers

Abstract

We have evaluated the synergism of five tetraalkyl phosphonium bromide salts with N-vinylcaprolactam based polymers by carrying out high pressure rocking cell experiments with a structure II-forming natural gas mixture. (n-Pe)4PBr was shown to be a superior synergist than (n-Bu)4PBr when used in combination with three different N-vinylcaprolactam based commercial polymers used in kinetic hydrate inhibitor formulations. These are poly(N-vinylcaprolactam) (PVCap), a N-vinylcaprolactam:N-vinylpyrrolidone 1:1 copolymer, and a N-vinylcaprolactam terpolymer. (n-Pe)4PBr and (n-Pe)4NBr were found to have very similar synergistic capacities and to perform better (n-Bu)4NBr when used with PVCap. (n-Bu)4PBr and (n-Bu)3(iso-Hex)PBr were better synergists than (n-Bu)4NBr with PVCap. They exhibited the same synergistic performances with PVCap even though (n-Bu)3(iso-Hex)PBr had been shown to be a better tetrahydrofuran (THF) hydrate crystal growth inhibitor. (n-Bu)3hexadecylPBr showed a synergistic performance similar ...