Improving the Kinetic Hydrate Inhibition Performance of 3-Methylene-2-pyrrolidone Polymers by N-Alkylation, Ring Expansion, and Copolymerization

摘要

Poly(N-vinyl lactam)s have been the dominant class of kinetic hydrate inhibitor (KHI) polymer for many years in oil and gas flow assurance applications. Recently, we reported on the KHI performance of a new, but closely related, polymer, poly(3-methylene-2-pyrrolidone), P(3M2P). It was suggested that, like poly(N-vinyl pyrrolidone), the polymer is not sufficiently hydrophobic for optimum KHI performance. We now report on three improvements to this class: (1) by alkylating the pyrrolidone ring, (2) by expanding the ring size from 5 to 6 atoms, and (3) by copolymerization with more hydrophobic monomers. All new polymers were tested in high pressure rocking cells with a Structure II-forming gas mixture. When methyl, ethyl, and n-propyl groups were introduced onto the pyrrolidone ring, the poly(5-n-propyl-3-methylene-2-pyrrolidone) homopolymer, with the lowest cloud point of the three polymers, showed the best KHI efficacy. Expanding the ring size to the 6-ring piperidone group also lowered the polymer cloud point and improved the KHI performance relative to P(3M2P). Copolymers of 3M2P with N-vinyl caprolactam and N-n-butyl methacrylamide (n-BuMAm) were also synthesized. All copolymers showed good improvements over P(3M2P). The best copolymer was the n-BuMAm:3M2P copolymer with the highest n-BuMAm content and lowest cloud point. The best two copolymers were further investigated at different concentrations (500, 1000, 2500, and 5000 ppm), showing an increase in performance with increasing concentration.