Oxyvinylenelactam Polymers-A New Class of Lactam-Based Kinetic Hydrate Inhibitor Polymers

Malcolm A Kelland; Radhakanta Ghosh; Audun Undheim; Erik G Dirdal; Hiroharu Ajiro

doi:10.1021/acsomega.2c03644

Oxyvinylenelactam Polymers-A New Class of Lactam-Based Kinetic Hydrate Inhibitor Polymers

ACS Omega. 2022 Sep 27;7(40):35686-35693. doi: 10.1021/acsomega.2c03644. eCollection 2022 Oct 11.

Authors

Malcolm A Kelland¹, Radhakanta Ghosh¹, Audun Undheim¹, Erik G Dirdal¹, Hiroharu Ajiro²

Affiliations

¹ Department of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway.
² Division of Material Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan.

Abstract

The deployment of kinetic hydrate inhibitors (KHIs) is a chemical method for the prevention of gas hydrate plugging in gas, condensate, and oil production flow lines. Polymers made using the monomer N-vinylcaprolactam (VCap) are one of the most common KHI classes. Alternative classes of polymers containing caprolactam groups are rare. Here, we present a study on oxyvinylenelactam polymers and copolymers with pendant piperidone or caprolactam groups. Low-molecular-weight homo- and copolymers were obtained. The nonrotating vinylene groups impart rigidity to the polymer backbone. Poly(oxyvinylenecaprolactam) (POVCap) was insoluble in water, but poly(oxyvinylenepiperidone) (POVPip) and OVPip:OVCap copolymers with 60+ mol % OVPip were soluble with low cloud points. KHI screening tests were carried out using the slow constant cooling method in steel rocking cells. POVPip was water soluble with no cloud point up to 95 °C but showed a poor KHI performance. In contrast, OVPip:OVCap copolymers with about 60-70 mol % OVPip were also water soluble and showed a reasonable KHI performance, better than that of poly(N-vinylpyrrolidone) but not as good as that of poly(N-vinylcaprolactam). Surprisingly, several additives known to be good synergists for VCap-based polymers showed negligible synergy or were antagonistic with the 62:38 OVPip:OVCap copolymer with regard to lowering the onset temperature of hydrate formation. However, a blend with hexabutylguanidinium chloride showed a strong effect to delay the onset of rapid hydrate formation.