A Study of the Kinetic Hydrate Inhibitor Performance and Seawater Biodegradability of a Series of Poly(2-alkyl-2-oxazoline)s

Kinetic hydrate inhibitors (KHIs) have been used successfully in the field for about the last 14 years to prevent gas hydrate formation mostly in gas and oilfield production lines. They work by delaying the nucleation and often also the growth of gas hydrate crystals for periods of time dependent on the subcooling in the system. Poly(2-alkyl-2-oxazoline)s [or poly(N-acylalkylene imine)s] are a known class of KHI, but no work has previously been published detailing a systematic study of structure versus performance. In this paper we report the KHI performance of poly(2-alkyl-2-oxazoline) homopolymers and statistical copolymers with alkyl side groups up to four carbon atoms. The study includes hydrate crystal growth tests on structure II tetrahydrofuran hydrate crystals as well as high pressure nucleation and crystal growth studies on a synthetic natural gas mixture giving structure II hydrates. Seawater biodegradation studies on all the polymers according to the OECD306 procedure indicate that they are all poorly biodegradable (<20% in 28 days).