First Study of Poly(3-methylene-2-pyrrolidone) as a Kinetic Hydrate Inhibitor

Abstract

Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with nonpolymeric synergists, that are used to prevent gas hydrate blockages. They have been used in the field successfully since 1995. In this paper, we present the first KHI results for the polymer, poly(3-methylene-2-pyrrolidone) (P(3M2P)), which is structurally similar to poly(N-vinylpyrrolidone) (PVP), one of the first KHIs to be discovered. 3M2P polymers with different molecular weights (5500 and 2500 g/mol) and at different concentrations (2500, 5000, and 7500 ppm) were investigated for their KHI performance on structure II hydrates in high-pressure rocking cells. We also investigated the synergistic effect of P(3M2P) with n-butyl glycol ether (BGE), a known synergist for some KHI polymers. At the lower concentrations, P(3M2P) gives a similar performance to PVP (Mw = 8000–9000 g/mol). However, PVP outperforms both samples of P(3M2P) at 7500 ppm, with and without BGE. We suggest that the reasons for the performance level of P(3M2P) are related to greater resonance stabilization of the amide group in P(3M2P) compared to PVP. Also, the pyrrolidone ring of the PVP repeat unit has a larger hydrophobic sequence of three methylene units compared to the two methylene units in the pyrrolidone ring of P(3M2P). This relates well to previous studies where larger hydrophobic groups are preferable in KHI polymers as long as they are water-soluble at hydrate-forming temperatures.