Vinyl lactam-based copolymers and terpolymers as high cloud point kinetic hydrate inhibitors in methane-THF-water system

Abstract A series of vinyl lactam-based polymers were synthesized and then evaluated as kinetic hydrate inhibitors (KHIs) in methane-tetrahydrofuran (THF)-water system. The inhibition performance of synthesized KHIs was examined and compared with commercially-available KHIs using a high-pressure rocking cell. The VCap/1-vinyl-2-pyrrolidone (VP) copolymer with a molar ratio of 3:1 could reduce hydrate growth rate by 18% greater than poly(N-vinylcaprolactam) (PVCap). Moreover, the modification of this copolymer with 3-mercaptopropionic acid (3-MPA) led to producing the novel KHI that more effectively decreased hydrate growth rate than non-modified copolymer. Moreover, the addition of 2-Dimethylaminoethyl methacrylate (DMAEMA) as a third monomer to the polymerization mixture improved the performance of the copolymers by 20%. Cloud point measurements revealed that all the synthesized copolymers, the modified copolymers and the terpolymers had higher cloud point in comparison with PVCap, such that cloud point temperature (Tcl) for mercaptoacetic acid (MAA)-modified copolymer and 3-mercaptopropionic acid (3-MPA)-modified copolymer was 43 and 20 °C higher than that of PVCap and these modified copolymers could be developed as novel high cloud point kinetic hydrate inhibitors even in saline solutions.