Investigation of the Kinetic Hydrate Inhibitor Performance of a Series of Copolymers of<i>N</i>-Vinyl Azacyclooctanone on Structure II Gas Hydrate

Abstract

A series of copolymers of N-vinylazacyclooctanone (VACO) with more hydrophilic monomers, including the 5–7 ring N-vinyl lactams, N-vinyl-N-methyl acetamide (VIMA), and N-vinyl acetamide (NVA), have been synthesized. Their performance as kinetic hydrate inhibitors (KHIs) was compared to poly(N-vinylazacyclooctanone) (PVACO) homopolymer in high pressure rocking cells using a Structure II hydrate-forming natural gas mixture. The best 1:1 copolymer between any two of the four N-vinyl lactams was found to be for VP/VACO copolymer. 1:1 VACO/VIMA copolymers were also shown to be a superior KHI to PVACO, whereas copolymers of other ratios of these two monomers were less effective KHIs. 2-Butoxyethanol (BGE) was also found to be a good solvent and synergist for 1:1 VACO/VIMA copolymers. Finally, 1:1 N-vinyl lactam/NVA copolymers were shown to have worse KHI performance than the equivalent 1:1 N-vinyl lactam/VIMA copolymers at similar molecular weights.