Kinetic Hydrate Inhibition of Poly(<i>N</i>-isopropylacrylamide)s with Different Tacticities

Chua, Pei Cheng; Kelland, Malcolm A.; Hirano, Tomohiro; Yamamoto, Hiroaki

doi:10.1021/ef300178u

Cited by 50 publications

(54 citation statements)

References 19 publications

(40 reference statements)

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“…This has been demonstrated for poly(isopropylmethacrylamide)s, where it was possible to evaluate the polymer tactcity by NMR spectroscopy. 23 We are currently investigating methods to determine the tacticity of poly(N-vinyl lactam)s.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Poly(N-vinyl azacyclooctanone): A More Powerful Structure II Kinetic Hydrate Inhibitor than Poly(N-vinyl caprolactam)

Chua

Kelland

2012

Energy Fuels

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Poly(N-vinyl azacyclooctanone) (PVACO) has been synthesized for the first time. Dependent upon the method of polymerization and polymer molecular weight, the cloud point of a 1.0 wt % solution in water can be varied between approximately 14 and 22°C. Using identical polymerization conditions for the four N-vinyl lactams with 5−8-membered rings, the polymer molecular weight decreases as the ring size increases. This is probably due to the relative steric effect of the monomers in the polymerization process. In high-pressure rocking cell experiments with a structure-II-forming hydrocarbon gas mixture, PVACO was shown to be a more powerful kinetic hydrate inhibitor (KHI) than the other 5−7-ring poly(N-vinyl lactam)s of similar molecular weight made using an otherwise identical method to PVACO. The synergistic effect of mono-nbutyl glycol ether with PVACO and the effect of the polymer molecular weight on KHI performance are also discussed. ■ INTRODUCTIONKinetic hydrate inhibitors (KHIs) are now a well-known technology for preventing gas hydrate plugs in upstream oilfield operations. 1−4 KHIs are water-soluble polymers, often with added synergists that improve their performance. KHIs delay the nucleation and usually also the crystal growth of gas hydrates. The nucleation delay time (induction time), which is the most critical factor for field operations, is dependent upon the subcooling (ΔT) in the system: the higher the subcooling, the lower the induction time. The absolute pressure is also an important factor. 5−8Probably the commonest class of polymers used in commercial KHI formulations are homo-polymers and copolymers of the N-vinyl lactams N-vinyl pyrrolidone (VP) and N-vinyl caprolactam (VCap). 9−16 Recently, we showed that the homo-polymer of the 6-ring N-vinyl lactam monomer N-vinyl piperidone (VPip) had an intermediate KHI gas hydrate performance between that of poly(N-vinyl pyrrolidone) and poly(N-vinyl caprolactam). 17,18 Thus, the KHI performance increases with an increasing lactam ring size. The structures of the homo-polymers of VP, VPip, and VCap are given in Figure 1. It was therefore of great interest to investigate whether the homo-polymer of an even larger ring N-vinyl lactam would perform better than homo-polymers with the smaller lactam rings. The 8-ring N-vinyl lactam monomer N-vinyl azacyclooctanone (VACO) has not been reported previously nor have any polymers from this monomer. We were also uncertain if the homo-polymer poly(N-vinyl azacyclooctanone) (PVACO) was even water-soluble and, therefore, could be tested as a KHI, because the cloud points of the poly(N-vinyl lactam)s decrease with lactam ring size. For example, PVCap as a 1.0 wt % solution in water has a cloud point of about 30−40°C depending upon the polymerization method and molecular weight, whereas cloud points for PVPip are generally in the range of 60−80°C. 17,18 In this paper, we report the synthesis and structure II (SII) gas hydrate KHI performance of PVACO for the first time and compare the results to other poly(N-vinyl la...

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Poly(N-vinyl azacyclooctanone): A More Powerful Structure II Kinetic Hydrate Inhibitor than Poly(N-vinyl caprolactam)

Chua

Kelland

2012

Energy Fuels

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“…Hydrate formation is divided into two stages: nucleation and crystal growth. In the nucleation stage, KHIs postpone the hydrate nucleation by increasing the induction time. − It is believed that induction time is the most important and key parameter in describing the performance and strength of the KHIs. Induction time is the time interval between the time that the system enters the hydrate equilibrium zone and the time that the hydrate is formed.…”

Section: Introductionmentioning

confidence: 99%

Experimental Determinations of the Complete Inhibition, the Slow Growth, and the Rapid Failure Regions of Methane Hydrate Formation in the Presence of Polyvinylpyrrolidone and Polyvinylcaprolactam Aqueous Solutions

et al. 2021

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Gas hydrate formation in gas transmission pipelines is one of the most critical troubles in the petroleum industry. One of the most convenient techniques to intercept gas hydrate formation is using inhibitors: e.g., thermodynamic hydrate inhibitors and kinetic hydrate inhibitors (KHIs). KHIs postpone the hydrate nucleation and slow down the hydrate growth rates by increasing the induction time. Because hydrate nucleation is probabilistic, the measurement of the induction time is difficult, and the measured data are normally nonrepeatable. It was observed that KHIs have repeatable behaviors by evaluating the KHIs based on the crystal growth inhibition approach in which the regions of inhibited hydrate growth can be considered as a function of subcooling: by increasing the subcooling from the complete inhibition region (CIR), reaching the slow growth rate region (SGR), and finally reaching the rapid failure region (RFR). In this study, the CIR, the SGR, and the RFR of methane hydrate formation in the attendance of polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap) aqueous solutions were experimentally measured. Also, in the pressure range of 35−80 bar, the effects of KHIs concentrations, i.e., 0.0025, 0.0050, and 0.0100 mass fractions for PVP and 0.0010 and 0.0025 mass fractions for PVCap, were investigated in these regions. It was concluded that the optimum concentration of PVP was 0.0050 for CIR and SGR. Also, by comparing the CIR, SGR, and RFR of PVP and PVCap aqueous solutions, it was observed that PVCap has a stronger inhibition impact with respect to PVP.

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“…This means that, when M n (which is around equal to M w , for the three polymers mentioned here) is around 4 kg/mol, the PGAOs with a larger size of the pendant ring groups gave better KHI performance. Interestingly, in 2012, Chua and Kelland already reported that an increasing ring size leads to improved KHI performance for the poly( N -vinyl lactam)s at M w ≈ 4 kg/mol, and they presumed that the reason for this tendency may involve polymer tacticity. ,, They hypothesized that the increasing steric bulk of the N -vinyl lactam probably leads to a more syndiotactic structure of the polymer when polymerized, and syndiotactic structures can maximize the polymer surface/volume ratio. It is the pendant amphiphilic groups of the polymer that interfere with the hydrate nucleation and crystal growth processes.…”

Section: Results and Discussionmentioning

confidence: 99%

N-Oxide Polyethers as Kinetic Hydrate Inhibitors: Side Chain Ring Size Makes the Difference

et al. 2021

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The formation of gas hydrates in flow lines is one of the most severe problems for flow assurance in the gas and oil industry. Developing effective kinetic hydrate inhibitors (KHIs) to avoid the problem of gas hydrate formation has attracted widespread attention. In this study, a series of poly(glycidyl amine N-oxide)s (PGAOs) with 5–7-membered rings as side chains, poly(pyrrolidine glycidyl amine N-oxide)s (PPyrGAOs), poly(piperidine glycidyl amine N-oxide)s (PPiGAOs), and poly(azepane glycidyl amine N-oxide)s (PAzGAOs), with varying molecular weights, have been synthesized. The KHI performance of these glycidyl amine N-oxide polyethers has been evaluated in high-pressure rocking cells with the synthetic natural gas (SNG) mixture. The PGAOs with lower molecular weights gave better KHI performance, and at 2500 ppm, the best one gave an average T o value of 9.8 °C (ΔT = 10.4 °C), which is on a par with polyvinylcaprolactam (PVCap). Even in high concentration of brine solution, none of the PGAOs showed a cloud point up to 95 °C. Employing molecular weights of around 4 kg/mol, the KHI performance of the PGAOs follows the following trend, correlating with the ring size: PPyrGAO < PPiGAO < PAzGAO. However, at higher molecular weight, the ring size of the pendant group did not affect the KHI performance of the PGAOs. PPiGAO with the smaller piperidine ring groups gave better inhibition effect than PAzGAO when the molecular weights were at approximately 8 kg/mol. In addition, the KHI performance of one of the best PAzGAOs was tested in the concentration range from 1000 to 5000 ppm, and an increase of the KHI performance with increasing concentration of polymer was observed. The amine N-oxide functional group is critical for the KHI performance of these polymers, as poly(pyrrolidine glycidyl amine)s (PPyrGAs) and poly(azepane glycidyl amine)s (PAzGAs) with amine groups instead of the N-oxide gave a negligible inhibitory effect.

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Kinetic Hydrate Inhibition of Poly(N-isopropylacrylamide)s with Different Tacticities

Cited by 50 publications

References 19 publications

Poly(N-vinyl azacyclooctanone): A More Powerful Structure II Kinetic Hydrate Inhibitor than Poly(N-vinyl caprolactam)

Poly(N-vinyl azacyclooctanone): A More Powerful Structure II Kinetic Hydrate Inhibitor than Poly(N-vinyl caprolactam)

Experimental Determinations of the Complete Inhibition, the Slow Growth, and the Rapid Failure Regions of Methane Hydrate Formation in the Presence of Polyvinylpyrrolidone and Polyvinylcaprolactam Aqueous Solutions

N-Oxide Polyethers as Kinetic Hydrate Inhibitors: Side Chain Ring Size Makes the Difference

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