Polydispersity in oligomeric low dosage gas hydrate inhibitors

Abstract

Gas hydrates are solid crystalline mixtures of water and small gas molecules, such as those found in natural gas. They are stable at temperatures and pressures commonly found on the sea floor and in sub-sea pipelines for the transportation of natural gas. It is the propensity of gas hydrates to cause blockages in pipelines that necessitates the addition of inhibitors to prevent hydrate formation. Recent work has focused on developing “low dosage hydrate inhibitors”, LDHIs, which act to delay nucleation or prevent growth while present at low concentrations (typically <1% by weight of water), but identifying new chemicals to provide more active LDHIs has been hindered by the absence of a clear molecular-level understanding of their activity. In this paper we present results of a molecular dynamics simulation study designed to provide this understanding. Simulations have been performed with an active component of a commercial LDHI—poly(dimethylaminoethylmethacrylate), PDMAEMA—at a water/methane interface under conditions for which hydrate growth is simulated in the absence of an inhibitor. Simulations have been performed with a variety in tacticity and initial backbone conformation to determine the effect of polydispersity in a real polymeric inhibitor. The results show increased hydrate growth for additive-containing systems.