Inhibition effects of poly(N-vinylcaprolactam)/poly(epsilon-caprolactone) amphiphilic block copolymers on methane hydrate formation

Homo- and copolymers of poly(N-vinylcaprolactam) PVCap are widely used in the natural gas industry as hydrate inhibitors. However, seldom studies focus on block copolymers and the biodegradability of the polymers is not taken into account as well. In this work, amphiphilic block copolymers (PVCap-b-PCL) containing different ratio of biodegradable poly(epsilon-caprolactone) (PCL) and PVCap were synthesized. All the synthesized copolymers had narrow molecular distribution which ensured stable properties of the copolymers in the kinetic hydrate inhibition (KHI) performance. They also showed higher cloud point than PVCap. The effect of the PVCap-b-PCL copolymers on methane hydrate formation and hydrate micro-structure were studied. The copolymers used in the KHI experiments were in the form of micelles and they were found performed better than PVCap in the methane hydrate inhibition, providing much longer induction time and increased with higher PCL segment content. The PVCap-b-PCL copolymers have amphiphilic structure similar with surfactants making them also perform like antiagglomerants, effectively suppressing the hydrate agglomeration (less than 40 mu m). The possible inhibition mechanism of PVCap-b-PCL was discussed. The biodegradable PCL segment has increased the biodegradability of PVCap-b-PCL as expected, indicating that environmental friendly hydrate inhibitors can be obtained by adjusting W-PCL/W-PVCap ratio. (C) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved