Poly(N-vinyl azacyclooctanone): A More Powerful Structure II Kinetic Hydrate Inhibitor than Poly(N-vinyl caprolactam)

Poly(N-vinyl azacyclooctanone) (PVACO) has been synthesized for the first time. Dependent upon the method of polymerization and polymer molecular weight, the cloud point of a 1.0 wt % solution in water can be varied between approximately 14 and 22 C. Using identical polymerization conditions for the four N-vinyl lactams with 5-8-membered rings, the polymer molecular weight decreases as the ring size increases. This is probably due to the relative steric effect of the monomers in the polymerization process. In high-pressure rocking cell experiments with a structure-II-forming hydrocarbon gas mixture, PVACO was shown to be a more powerful kinetic hydrate inhibitor (KHI) than the other 5-7-ring poly(N-vinyl lactam)s of similar molecular weight made using an otherwise identical method to PVACO. The synergistic effect of mono-n-butyl glycol ether with PVACO and the effect of the polymer molecular weight on KHI performance are also discussed.