Macroscopic and spectroscopic identifications of the synergetic inhibition of an ionic liquid on hydrate formations

In order to identify the synergetic inhibition of hydrate formation by a new pyrrolidinium cation-based ionic liquid with a commercial kinetic inhibitor, poly(N-vinylcaprolactam)(PVCap), pure CH4 (structure I) and synthesized natural gas (structure II) hydrate samples are prepared and analyzed with solid-state C-13 NMR spectroscopy. In addition, the time-resolved macroscopic pressure changes and microscopic Raman spectra are also measured using the synthesized natural gas and two inhibitors. Hydrate formation or formed hydrate structure is found to be different for the PVCap-only and the PVCap + [HEMP][BF4] systems. Furthermore, the addition of [HEMPI[BF4] is found to delay the induction time and hydrate growth further when added to the PVCap-only system although some deviations are observed for the induction time. Adding the ionic liquid to the PVCap system can have a synergetic effect on the hydrate formation (natural gas hydrate of the structure II, in particular), which may indicate different inhibition mechanisms of PVCap and [HEMP][BF4]. (C) 2016 Elsevier Ltd. All rights reserved.