First Investigation of the Kinetic Hydrate Inhibitor Performance of Polymers of Alkylated<i>N</i>-Vinyl Pyrrolidones

Abstract

A series of water-soluble homopolymers and copolymers of 1-alkyl-vinyl pyrrolidones (1-alkyl-VPs) with alkyl groups, including methyl, ethyl, isopropyl, and n-propyl, has been synthesized. Homopolymers with larger alkyl groups had cloud points in water lower than 0 °C. The comonomers used in the copolymers were N-vinyl pyrrolidone (VP) and N-methyl-N-vinyl acetamide (VIMA). The performance of the water-soluble 1-alkyl-VP polymers as kinetic hydrate inhibitors was investigated for the first time. Tests were conducted in high-pressure rocking cells using a structure II hydrate-forming natural gas mixture and compared to poly(N-vinyl lactam)s of similar molecular weight. The best copolymer of this series was the 1:1 nPr-VP/VIMA copolymer. 1-dimethyl-VP and 1-ethyl-VP homopolymers and the 1:1 n-propyl-VP/VP copolymer also showed better performance than poly(N-vinyl caprolactam) and poly(N-vinyl azocyclooctanone) of similar molecular weights. The structure–performance analysis in this study suggests that a more lipophilic ring than PVP gives better structure II gas hydrate kinetic inhibition than PVP itself. Second, alkylation of PVP gives a better kinetic hydrate inhibitor (KHI) than expanding the PVP lactam ring with the same number of carbon atoms as used in the alkylation.