Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

Singh, Ankur; Suri, Ajay

doi:10.1021/acs.energyfuels.1c02180

Cited by 39 publications

(39 citation statements)

References 188 publications

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“…Standard constant cooling experiments are to be performed in a high-pressure autoclave to investigate the hydrate-inhibiting performance of the various polysaccharide synergists with the different reference KHIs. The four KHI polymers (PVP, PVCap, Luvicap 55w, and HIOP) are selected based on our previous reviews of KHIs . Similarly, the three plant-based polysaccharides (pectin, k-carrageenan, and guar gum) are selected as synergists based on the preliminary promising hydrate inhibition performance shown. − A brief review of the three polysaccharides along with the hydrate-inhibiting mechanism of KHI and natural synergist hybrid system is presented next.…”

Section: Methodsmentioning

confidence: 99%

“…In all the hydrate inhibition tests, a standard constant cooling rate process is used. , About 150 mL of testing solution (distilled water with the inhibitor dissolved) is loaded in the reactor cell, and the system’s pressure is raised and maintained at 76 bar using methane gas after flushing air from the cell. The initial temperature is brought down to 11 °C from the higher ambient temperature.…”

Section: Methodsmentioning

confidence: 99%

“…The four KHI polymers (PVP, PVCap, Luvicap 55w, and HIOP) are selected based on our previous reviews of KHIs. 32 Similarly, the three plant-based polysaccharides (pectin, k-carrageenan, and guar gum) are selected as synergists based on the preliminary promising hydrate inhibition performance shown. 23−26 A brief review of the three polysaccharides along with the hydrate-inhibiting mechanism of KHI and natural synergist hybrid system is presented next.…”

Section: Methodsmentioning

confidence: 99%

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Enhanced Hydrate Inhibition by Plant-Based Polysaccharides as Synergists with Kinetic Hydrate Inhibitors

Singh

Suri

2022

Energy Fuels

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Three plant-based polysaccharides, pectin, k-carrageenan, and guar gum, are investigated as synergists with four kinetic hydrate inhibitors (KHIs), polyvinylpyrrolidone, polyvinylcaprolactam, Luvicap55w, and HIOP. The enhancement in the hydrate inhibition performance is characterized by measuring the increase in the delay/induction time (IT) taken for hydrate nucleation and the reduction in hydrate growth after nucleation. Standardized constant cooling rate hydrate formation tests are performed. Experimental results provided by 0.5 wt % aqueous solutions of reference KHIs are compared with the results of aqueous solutions made with combining 0.25 wt % reference KHI with 0.25 wt % polysaccharide synergist. K-carrageenan showed exceptional inhibition synergy with all KHIs with ITs enhanced around 20–35% with different reference KHIs and reduced hydrate growth rates up to 90%. Guar Gum did not increase the IT provided by reference KHIs. However, it decreased hydrate growth rates by 77–90% of all KHIs. Pectin showed exceptional hydrate inhibition synergy with HIOP (commercial KHI), boosting its IT by 45%.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Enhanced Hydrate Inhibition by Plant-Based Polysaccharides as Synergists with Kinetic Hydrate Inhibitors

Singh

Suri

2022

Energy Fuels

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“…We have begun a program to develop multi-functional chemicals in an attempt to treat gas hydrates, corrosion, and scale, which are all water-based problems. Regarding the first issue, we have been designing and testing kinetic hydrate inhibitors (KHIs) as a method to prevent gas hydrate solids from forming in flow lines. − KHIs delay the hydrate formation process at the nucleation and crystal growth stages. , KHIs have been shown to both increase the nucleation work required to form critical nuclei and increase the effective number of sites where nucleation could occur …”

Section: Introductionmentioning

confidence: 99%

N-Vinyl Caprolactam/Maleic-Based Copolymers as Kinetic Hydrate Inhibitors: The Effect of Internal Hydrogen Bonding

et al. 2022

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Kinetic hydrate inhibitors (KHIs) have been used for over 25 years to prevent gas hydrate formation in oil and gas production flow lines, but they are some of the most expensive oilfield production chemicals. The main component in KHI formulations is a water-soluble polymer with many amphiphilic groups. Usually, in commercial KHI polymers, the hydrophilic part of these groups is the amide group. In addition, KHI polymers are often incompatible with film-forming corrosion inhibitors. Therefore, we sought to find cheaper but effective KHIs that could also act as a flow line corrosion inhibitor. Continuing earlier work from our group with maleic-based polymers, we have now explored maleic acid/N-vinyl caprolactam (MAcid/VCap) copolymers to introduce VCap, a well-known KHI monomer, together with the cheaper MA monomer. KHI performance screening tests 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. Surprisingly, the MAcid/VCap copolymer showed very poor KHI efficacy. GFN2-xTB molecular dynamics simulations revealed that MAcid/VCap exhibits intra-hydrogen bond networks that trap the polymer morphology in the globular form. In this scenario, the caprolactam ring is encapsulated inside the polymer structure due to the intra-hydrogen bonds and the hydrophobic interactions that minimize its ability to interact with the hydrate surfaces, which significantly reduces the MAcid/VCap kinetic inhibition performance. However, the polymer in such globular forms still displays an important amount of its carboxylic groups exposed to water, which explains the water solubility. In contrast to MAcid/VCap copolymers, maleimide derivatives with dibutylamino end groups were effective KHIs and even better with dibutylamine oxide end groups. A terpolymer of MA/VCap reacted with N,N-dibutylaminopropylamine followed by subsequent oxidation of the end groups to dibutylamine oxide and gave the best performance of any maleic-based polymer reported to date. The combination of caprolactam and dibutylamine oxide groups can be thought of as synergism within the same polymer, akin to the excellent synergy of the separate molecules, tributylamine oxide and PVCap.

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“…KHIs can affect both the gas hydrate nucleation and crystal growth processes, delaying the build-up of gas hydrates for a length of time depending on the driving force (chemical potential) of the system. , KHIs have been shown to both increase the nucleation work required to form critical size nuclei and increase the effective number of sites where nucleation could occur . The driving force of the system is often described in terms of subcooling, but other factors including the absolute pressure must be taken into account. − There is evidence that KHIs can give total inhibition for an indefinite period up to a certain driving force …”

Section: Introductionmentioning

confidence: 99%

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

2021

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Kinetic hydrate inhibitors (KHIs) have been used for over 25 years to prevent gas hydrate formation in oil and gas production flow lines. The main component in KHI formulations is a water-soluble polymer with many amphiphilic groups, usually made up of amide groups and adjacent hydrophobic groups with 3–6 carbon atoms. KHI polymers are one of the most expensive oilfield production chemicals. Therefore, methods to make cheaper but effective KHIs could improve the range of applications. Continuing earlier work from our group with maleic-based polymers, here, we explore maleic acid/alkyl acrylate copolymers as potential low-cost KHIs. Performance 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. Under typical pipeline conditions of pH (4–6), the performance of the maleic acid/alkyl acrylate copolymers (alkyl = iso-propyl, iso-butyl, n-butyl, tetrahydrofurfuryl, and cyclohexyl) was poor. However, good performance was observed at very high pH (13–14) due to the thermodynamic effect from added salts in the aqueous phase and the removal of CO2 from the gas phase. A methyl maleamide/n-butyl acrylate copolymer gave very poor performance, giving evidence that direct bonding of the hydrophilic amide and C4 hydrophobic groups is needed for good KHI performance. Reaction of the maleic anhydride (MA) units in MA/alkyl acrylate 1:1 copolymers with dibutylaminopropylamine or dibutylaminoethanol gave polymers with good KHI performance, with MA/tetrahydrofurfuryl methacrylate being the best. Oxidation of the pendant dibutylamino groups to amine oxide groups improved the performance further, better than poly(N-vinyl caprolactam).

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Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

Cited by 39 publications

References 188 publications

Enhanced Hydrate Inhibition by Plant-Based Polysaccharides as Synergists with Kinetic Hydrate Inhibitors

Enhanced Hydrate Inhibition by Plant-Based Polysaccharides as Synergists with Kinetic Hydrate Inhibitors

N-Vinyl Caprolactam/Maleic-Based Copolymers as Kinetic Hydrate Inhibitors: The Effect of Internal Hydrogen Bonding

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

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