Arium mini plus ultra pure water system

Isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), polyethylene glycol 400 (PEG), triethylamine (TEA) and deuterated dimethyl sulfoxide-d₆ (99.8% d) were purchased from Sigma-Aldrich. 2,2-Bis(hydroxymethyl)propionic acid (DMPA), ethanolamine (EA) and tetrahydrofuran were obtained from Merck Chemical Co. All reagents were used without further purification. Methane gas of 99.95% purity was used for experiments. Water used for methane hydrates formation experiments and for preparation of inhibitors solution of desired concentration was carefully purified. On the first step it was twice distillated. On the second step it was deionized using Arium mini plus ultra-pure water system (Sartorius, Germany) to achieve resistivity 18.20 MΩ·cm at 25 °C.

All reagents were obtained from commercial sources and were used without further purification unless otherwise stated. Deionized water prepared by Arium mini plus ultra-pure water system (Sartorius, Goettingen, Germany) to achieve resistivity 18.20 MΩ∙cm at 25 °C was used in all experiments. Commercial KHI Luvicap 55 W (BASF, Ludwigshafen, Germany) and corrosion inhibitor Armohib CI-28 (AkzoNobel, Amsterdam, Netherlands) were used for comparison. The former one is copolymer of N-vinyl caprolactam and N-vinyl pyrrolidone (hereinafter P(VCap-VP)) with molar ratio of 1:1 and molecular mass of 2–8 kDa. The latter one belongs to the class of fatty acid imidazolines. Binary mixture of 4.34 mol% C₃H₈ + 95.66 mol% CH₄ was employed as hydrate-forming gas. This mixture forms the hydrate of cubic structure II (sII) which is common one encountered in the field.