Maleic and Methacrylic Homopolymers with Pendant Dibutylamine or Dibutylamine Oxide Groups as Kinetic Hydrate Inhibitors

Abstract

Kinetic hydrate inhibitors (KHIs) are applied in oil and gas fields to prevent gas hydrate formation, most often in cold subsea flow lines. The main component in industrial KHI formulations is a water-soluble polymer with many amphiphilic groups of which the hydrophilic part is most commonly the amide functional group. In the last decade, we have investigated polyamine oxides as alternatives to polyamides due to the strong hydrogen bonding of the amine oxide group. Here, we report the KHI performance of maleic and methacrylic homopolymers with dialkylamine and dialkylamine oxide pendant groups. Performance screening experiments were conducted under high pressure with a Structure II-forming natural gas mixture in steel rocking cells using the slow (1 °C/h) constant cooling test method. Polymers with dibutylamine groups gave much better KHI performance than polymers with dimethylamine or diethylamine groups. Polyamines formed from polymaleic anhydride reacted with 3-(dibutylamino)-1-propylamine (DBAPA) or 2-(dibutylamino)-ethanol (DBAE) gave good water solubility and good KHI performance, probably due to self-ionization between the dibutylamino and carboxylic acid groups. The lack of self-ionization for the methacryl homopolymers of DBAPA and DBAE explains why these polymers are not water-soluble. Oxidation of the maleic or methacryl polyamines to polyamine oxides gave water-soluble polymers with good compatibility with brines (0.5−7.0 wt % NaCl), but only the DBAPA-based polyamine oxides gave improved KHI performance compared to the polyamines. Poly(3-(dibutylamino oxide)-1-propyl methacrylamide) gave a similar performance to commercial N-vinyl pyrrolidone:N-vinyl caprolactam 1:1 copolymer and without a cloud point in deionized water up to +95 °C.

Tailored Amine Oxides─Synergists, Surfactants, and Polymers for Gas Hydrate Management, a Minireview

“…Ethyl groups are also smaller than the optimal size, as evidenced by the poor KHI performance of a diethylamine oxide derivative of polymaleic anhydride (PMA), PMA-DEtAPA-AO (Table ). Therefore, homopolymers with dibutylamine oxide groups were focused on using the available reagents DBAPA and 2-(dibutylamino)­ethanol (DBAE) . (Figure ).…”

“…Therefore, homopolymers with dibutylamine oxide groups were focused on using the available reagents DBAPA and 2-(dibutylamino)ethanol (DBAE). 57 (Figure 24). A summary of the main findings is in Table 11.…”

Multi-functional Flow Assurance Chemicals: Corrosion and Kinetic Hydrate Inhibition from Maleic Anhydride:N-Vinyl Caprolactam Copolymers and Synergists

“…Reaction of the homopolymer polymaleic anhydride (PMA) with DBAPA or dibutylethanolamine and their amine oxide derivatives gave good KHI performance. 45 As KHIs are limited in their application (subcooling and other factors), we wanted to start with a high-performing maleic-based KHI before modifying it to also inhibit corrosion and scale, since these modifications will probably reduce the KHI's efficacy to some degree. In addition to VCap, another monomer with similar activity and used in commercial KHI polymers is N-isopropylmethacrylamide (NIPMAm).…”

“…Reaction of the homopolymer polymaleic anhydride (PMA) with DBAPA or dibutylethanolamine and their amine oxide derivatives gave good KHI performance …”

“… Reaction of 3-(dibutylamino)-1-propylamine with MA: N -vinyl caprolactam (MA:VCap) copolymer followed by oxidation to give pendant dibutylamine oxide groups gave the best performing MA-based KHI reported to date, MA:VCap-DBAPA-AO Reaction of the homopolymer polymaleic anhydride (PMA) with DBAPA or dibutylethanolamine and their amine oxide derivatives gave good KHI performance …”