Improved Gas Hydrate Kinetic Inhibition for 5-Methyl-3-vinyl-2-oxazolidinone Copolymers and Synergists

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

doi:10.1021/acsomega.3c03986

Improved Gas Hydrate Kinetic Inhibition for 5-Methyl-3-vinyl-2-oxazolidinone Copolymers and Synergists

ACS Omega. 2023 Jul 25;8(31):28859-28865. doi: 10.1021/acsomega.3c03986. eCollection 2023 Aug 8.

Authors

Malcolm A Kelland¹, Erik G Dirdal¹, Radhakanta Ghosh¹, 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

Kinetic hydrate inhibitors (KHIs) are used to prevent deposits and plugging of oil and gas production flow lines by gas hydrates. The key ingredient in a KHI formulation is a water-soluble amphiphilic polymer. Recently, polymers of a new commercially available 5-ring vinylic monomer 5-methyl-3-vinyl-2-oxazolidinone (VMOX) were investigated as KHIs and shown to perform better than some commercial KHI polymers such as poly(N-vinyl pyrrolidone). This initial study using slow constant cooling (SCC) in rocking cells with a synthetic natural gas has now been expanded to further explore low molecular weight PVMOX homopolymers and VMOX copolymers as well as blends with nonpolymeric synergists. A PVMOX homopolymer with improved KHI performance was found using 3-mercaptoacetic acid as a chain transfer agent in the radical polymerization of VMOX. Among a range of copolymers, VMOX:n-butyl acrylate copolymers in particular gave good KHI performance, better than the PVMOX homopolymer. Among the potential synergists, trialkylamine oxides (alkyl = n-butyl or iso-pentyl) and tetra(n-pentyl)ammonium bromide to 2500 ppm were found to be antagonistic with PVMOX at the test concentrations while some alcohols and glycols were synergetic. The best synergist was 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD). For example, a mixture of 2500 ppm TMDD with 2500 ppm PVMOX (M_w 2400 g/mol) performed significantly better than 5000 ppm PVMOX. Addition of 1250 ppm TMDD to 2500 ppm VMOX:n-butyl acrylate 6:4 copolymer lowered the hydrate onset temperature in SCC tests by a further 3 °C compared to the copolymer alone giving hydrate onset at 4.2 °C.