Polyvinylsulfonamides as Kinetic Hydrate Inhibitors

Kinetic hydrate inhibitor (KHI) polymers have been used for over 25 years to prevent gas hydrate formation in oil and gas production flow lines. KHI polymers are water-soluble at hydrate formation conditions, and most of them contain amide (-NH-C(=O)-) functional groups. The water solubility is due to their strong hydrophilicity and hydrogen-bonding ability. In this report, we have investigated various classes of polyvinylsulfonamides as KHIs for the first time. The carbonyl moiety in the amide group can be replaced with the sulfonyl moiety to give the isosteric sulfonamide group (-NH-S(=O)(2)-) which has two oxygen atoms. Similar to amides, the hydrogen atoms in sulfonamides are relatively acidic because the charge formed in the conjugate base can be stabilized by resonance. In addition, sulfonamides are not easily hydrolyzed under hot acidic conditions, a problem that is known for some polyamide KHIs which can affect their performance in the field. Here, we report the synthesis and KHI performance of a range of polyvinylsulfonamides. Tests were conducted under high pressure with a structure II-forming natural gas mixture in steel rocking cells. The performance of the best polymers was similar to that of poly(N-vinylcaprolactam) with comparable molecular weight, which is a well-known commercial KHI polymer.