A Simple and Direct Route to High-Performance Acrylamido-Based Kinetic Gas Hydrate Inhibitors from Poly(acrylic acid)

(Meth)acrylamido-based polymers are used commercially in kinetic hydrate inhibitor formulations to prevent gas hydrate formation in upstream oil and gas flow lines. The monomers used to make these polymers are relatively expensive. We have now synthesized a series of acrylamido-based polymers directly from low molecular weight poly(acrylic acid) (PAA) in a high-yield process, avoiding the use of expensive monomers. Cloud points of the polymers made from PAA were similar to the homopolymers made from the acrylamido monomers, indicating a good conversion from the acid to the amide group. Slow constant-cooling KHI screening tests were carried out on the new polymers in a series of steel rocking cells using a structure II-forming natural gas mixture. Poly(N-isopropylacrylamide), poly(N-(n-propyl) acrylamide), and polyacryloylpyrrolidine prepared directly from PAA all gave an excellent KHI performance, comparable to the homopolymers made from the acrylamido monomers. This direct synthesis method also allows for a very controlled comparison of the activity of the acrylamido functional groups because every polymer can be derived from the same PAA starting material. Thus, the number of monomer units in each homopolymer is kept constant. Conversion of the poly(methacrylic acid) or poly(methyl methacrylate) by the reaction with amines to give the methacrylamido polymers was not successful, probably due to the steric effect of the backbone methyl groups.