A Review of Kinetic Hydrate Inhibitors from an Environmental

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A Review of Kinetic Hydrate Inhibitors from an Environmental Perspective Malcolm A. Kelland*

Energy Fuels Downloaded from pubs.acs.org by UNIV OF WINNIPEG on 12/19/18. For personal use only.

Department of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway ABSTRACT: Kinetic hydrate inhibitors (KHIs) have been used in the upstream petroleum industry for about 25 years to prevent plugging of flow lines with gas hydrates. The main ingredients in current commercial KHI formulations are one or more water-soluble polymers which contain both hydrophobic and hydrophilic functionalities. Although the vast majority of KHIs are low in acute toxicity and bioaccumulation, very few commercial products show good biodegradability, and for that reason, there is always some concern of long-term chronic toxicity from partially degraded products if discharged into the environment. This report reviews all efforts to develop more biodegradable KHIs, and outlines the fact that some classes of so-called “green” chemicals are not necessarily readily biodegradable or low in toxicity. The review also covers methodologies to recover or destroy KHIs and reduce their discharge to the environment.

1. INTRODUCTION In the late 1980s, the upstream oil industry began research projects to develop low dosage hydrate inhibitors (LDHIs) to go alongside low dosage inhibitors that were already available for other flow assurance issues such as wax, asphaltene, and scale formation. All of these low dosage inhibitors are noncolligative, which means they do not depend on the ratio of the number of solute particles to the number of solvent molecules in a solution. LDHIs are usually subdivided into two main classes, kinetic hydrate inhibitors (KHIs) and anti-agglomerants (AAs). AAs allow gas hydrate formation under controlled conditions, causing a dispersion of small transportable particles to form.1−5 AAs will not be discussed further in this review. The key ingredient in KHI formulations is a water-soluble polymer or oligomer which contains both hydrophobic and hydrophilic functionalities. These functionalities interact with both free water and water found in gas hydrate particles to prevent macroscopic hydrate formation and plugging of flow lines in oil and gas fields. The exact KHI mechanism is still not clear, but there is good evidence that nucleation inhibition and crystal growth inhibition are involved with many of the oligomers and polymers.6

Figure 1. Repeating units in classic commercial KHI polymers: clockwise from top left, N-vinyl-2-pyrrolidone, N-vinyl-2-caprolactam, N-isopropylmethacrylamide, and a polyesteramide unit made from diisopropanolamine and hexahydrophthalic anhydride.

This general trend holds true, with the noticeable exception of polyvinyl alcohol (PVA) homopolymer, for many water-soluble materials, including poly(N-vinyl-2-pyrrolidone), poly(acrylamide)s, and several other polycarboxylates.7 In a later study in water-soluble polymers, efficient mineralization in a reasonable time frame ( 10 mg/L and bioaccumulation log Pow < 3 when the chemical molecular weight is less than 600 g/mol. Aqueous media biodegradation tests, such as the OECD301 series, generally give faster and higher biodegradation rates than in seawater. Although the bacterial community may be different than those in seawater, the bacteria levels allowed to be spiked to the fresh water (e.g., from sewage water) are generally several orders of magnitude higher.12 Besides N-vinyl lactam and N-alkylacrylamide polymers, the other main class of commercial KHI polymers are the hyperbranched polyesteramides (HPEAs) (Figure 1). The HPEA polymers have ester and amide linkages in the backbone which can be biodegraded by enzyme hydrolysis if these functional groups are not sterically difficult to access.13 However, although HPEAs may show some seawater biodegradation in 28 days, the partially degraded products after hydrolysis could be toxic and less degradable.14 End groups such as polyglycol chains or ionic functionalities such as zwitterions can improve the performance and raise the cloud point in aqueous fluids, but this will probably have a minimal effect on the biodegradation of the backbone of these HPEAs.15−18 Besides the main KHI polymer, KHI formulations often contain several components which act synergistically. This could be other KHI polymers, nonpolymeric molecules, and one or more solvents. The high flash point solvent n-butyl glycol ether (BGE) is used as a synergist with some N-vinyl caprolactambased KHI polymers.19,20 It has been tested for seawater biodegradation, giving a BOD28 value of 28−34%.13 Potentially more environmentally friendly solvents such as propylene carbonate, propylene glycol butyl ether, and (S)-n-butyl lactate have been proposed to be used; poly(N-vinyl caprolactam) (PVCap) made in the latter solvent was shown to give longer delay times in high pressure isothermal KHI tests than PVCap made in BGE.21

3. METHODS TO AVOID DISCHARGE OF LESS BIODEGRADABLE KHIS Although commercial KHI polymers generally have low bioaccumulation and low toxicity, the low biodegradation rate of many of them can prevent their use (and discharge) in some environmentally sensitive areas. Several methods have been investigated to avoid any possible environmental impact of poorly biodegraded KHI polymers. They include:

4. CLASSES OF KHIS PROPOSED TO HAVE SOME ENVIRONMENTAL ADVANTAGE Classes of KHIs discussed below have been separated into two sections, polymeric and nonpolymeric. Not surprisingly, since all commercial KHIs are based around polymers as the main active ingredient, the best of the polymers in the categories below also appear to have greater potential as KHI than the nonpolymeric classes. In fact, the two classes of nonpolymeric chemicals,

• Recycle KHI polymers • Degrade and destroy the KHI polymers to smaller and benign chemicals • Reinject KHI via wells into the formation • Develop readily biodegradable KHI polymers B

DOI: 10.1021/acs.energyfuels.8b03363 Energy Fuels XXXX, XXX, XXX−XXX

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groups, but polymer backbones containing either of these functional groups should be more biodegradable than polyvinyl backbones.4 Where data is available, I have reported seawater biodegradation rates for the polyester or polyamide polymers in this section. Polyesters or polyethyleneimines with pendant pyroglutamate groups have been developed as high cloud-point, biodegradable KHIs.46,47 One of these polymers has already been used on a low-subcooling, small field application in Europe.48−50 A seawater biodegradation test over 28 days by the OECD306 test method gave a BOD28 value of 62%. This readily biodegradable version in this class is proposed for use at maximum 4−5 °C subcooling with added synergists. An example of a polypyroglutamate is given in Figure 3. The

amino acids and ionic liquids, have also been investigated as thermodynamic inhibitors due to their low molecular weights. 4.1. Graft Polymers. The idea here is to use a more biodegradable polymer as the backbone and graft vinylic monomers onto it. This may require some prior modification of the biodegradable polymer to obtain the correct functional groups so that reaction with vinylic monomers is achieved. The grafted polyvinyl chains may well be shorter than a pure homopolymer KHI of the same monomer, but unless they are very short, they could still be just as poorly biodegradable as the homopolymer. The overall biodegradability may be improved compared to the pure polyvinyl homopolymer such as PVCap or PNIPMAM, but can lead to a relatively lower performance. This may simply be an effect of the lower molar concentration of hydrate-inhibiting active groups in the grafted polymer due to the extra molecular weight of the biodegradable backbone. For example, the use of N-vinyl lactams grafted onto a backbone of preferably a polyalkylene glycol, polyalkyleneimine, polyether, or polyurethane has been claimed (Figure 2). Grafting is carried out using radical initiators.36,37

Figure 2. N-Vinyl caprolactam (VCap) and vinyl acetate (VA) grafted onto polyethylene glycol (PEG).

Figure 3. One class of pyroglutamate polyester kinetic hydrate inhibitors.

The heteroatoms in the backbone are proposed to help increase the biodegradability of the polymer. The use of polymers with protein or peptide backbones onto which are grafted N-vinyl lactam and other vinylic monomers, as KHIs, has been claimed.38 Examples use gelatin (which is collagen protein, made from boiling bones), reacted with maleic anhydride and sodium hydroxide. This product is reacted with VCap (or a mix with VP or VIMA monomers) with other additives and an azo initiator to get a graft polymer. A graft polymer of this class has been commercialized.39,40 Grafting of VP, VCap, N-alkyl(meth)acrylamides, and other vinylic monomers onto polyaspartates and other polypeptides has also been claimed.41 Polysaccharides, such as maltodextrins, have also been used as the biodegradable backbone for KHI graft polymers.42,43 Reverse graft KHI polymers have also been reported in which the backbone is still polyvinyl-based (e.g., PVCap), but the side chains are grafted with more biodegradable polymer chains. For example, polylactide, a well-known biodegradable plastic, has been grafted onto the hydroxyl groups present in certain Nvinyllactam or vinyl amide copolymers. The comonomer could be, for example, hydroxyethylmethacrylate or vinyl alcohol.44,45 4.2. Other Synthetic Polyester and Polyamide KHI Polymers. Besides the commercialized hyperbranched poly(ester amide)s discussed earlier, several other ester or amidebackboned polymer classes have been investigated as KHIs. Ester groups are generally faster to be biodegraded than amide

pendant groups resemble those found in PVP, although the point of attachment to the polymer backbone is different. Therefore, the subcooling performance is not expected to be very high, but it is claimed to be somewhat better than PVP. Polymers in this class, for example, with fatty acid ester groups, appear to show some performance as hydrate AAs.90 The polyesters are made by condensing substituted dicarboxylic acids with diols or polyols, followed by reaction with pyroglutamic acid. Polyester polymers with a plurality of ammonium or amine functional groups pendant from the backbone have been claimed as KHIs.51 The general structures are given in Figure 4. Typical examples are made by the reaction of aspartic acid with polyols, such as sorbitol, triethylene glycols, polyethylene glycols (PEGs), and hyperbranched polyhydroxy polymers based on 2,2-dimethylol propionic acid (Bis-MPA). PEGs, polyethylene oxide (PEO), and polypropylene oxide (PPO) are generally poor KHIs when used by themselves but have been used as synergists to boost the performance of commercial KHI polymers such as PVCap.4,6 Citric acid is a natural polyacid, which is edible and readily biodegradable. Derivatization to citramides has been shown to give molecules with some KHI effect (Figure 5).52 Related unsaturated amides, and optionally esters, are also included in C


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In an attempt to increase the performance of the monomeric citramides, a series of low molecular weight polymers containing citramide units were synthesized and investigated as KHIs (Figure 6).53 These poly(ethylene citramide)s contain amide groups along the branches of the chains which should allow good biodegradation in a similar way to polypeptides. Only a few polymers in this class have been investigated, with the best performance being for the cyclohexyl derivative. 4.3. Pseudo-polypeptides. Several classes of pseudopolypeptides have been investigated as potentially more biodegradable KHIs than the commercial polyvinyl-based KHI polymers. Pseudo-polypeptides are structural variations on natural polypeptide chains found in proteins (Figure 7). The Figure 4. Polyester KHIs with ammonium groups. A and B are preferentially alkylene or polyoxyalkylene groups

Figure 7. General structure of natural polypeptide chains.

meaning of the words protein, polypeptide, and peptide can be a little confusing. Protein is generally used to refer to the complete biological molecule in a stable conformation, whereas peptide is generally reserved for short amino acid oligomers (maybe 20− 30 residues) often lacking a stable three-dimensional structure.54 Polypeptide can refer to any single linear chain of amino acids, usually regardless of length, but often implies an absence of a defined conformation. One of the first classes of pseudo-polypeptides to be investigated as KHIs was the polyaspartamides (Figure 8).55,56 The related polyaspartates are well-known biodegradable scale inhibitors used in the water treatment and oil industry.4 It was mentioned earlier that they can be used as backbones for grafting on vinylic monomers. Polyaspartamide derivatives with small pendant C3−C4 alkyl groups gave good KHI performance on Structure II gas hydrate-forming systems and were also shown to have good biodegradability. By incorporating some amide and some carboxylic acid groups, it was possible to achieve both

Figure 5. Citramides and related unsaturated amides (R1 = H or acetyl, R2 = alkyl).

the claims of the patent. Typical alkyl groups for best performance include isopropyl or isobutyl. However, in the examples given, the performance was not very high, which probably is reflected in there being too few (three) alkylamide groups in the molecule.

Figure 6. General structures of poly(ethylene citramide) (R = H), and its N-alkyl urea derivatives. D


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The adsorption inhibition mechanism of antifreeze proteins is a noncolligative phenomenon where AFPs are irreversibly adsorbed on the ice crystal. However, the process is not well understood, and different mechanistic explanations are discussed in the literature.65,66 Both ice and gas hydrates have lattice structures made of water molecules, but the evidence suggests that the inhibition mechanism toward ice and hydrate formation is different. In ice, AFPs allow the formation of nuclei, to which they bind, after which growth is inhibited. In hydrates, the nucleation itself can also be inhibited, although direct crystal growth inhibition is also possible for many KHIs.67 Shell, the energy company, was the first to speculate that artificial AFPs and AFGPs might bind to the surface of gas hydrate nuclei.2 The AFPs and AFGPs themselves were found to be expensive and fairly poor KHIs, but this led to Shell and other companies searching for cheaper and synthetic polymers that could mimic the same structural features, such as amide groups and hydrophobic groups. This resulted in the development of the synthetic polymer KHIs, such as PVP, PVCap, and later poly(N-alkylacrylamide)s and the hyperbranched poly(ester amide)s discussed at the beginning of this review.68,69 The discovery of poly(N-isopropylmethacrylamide) (PNIPMAM) as a KHI may well have been fueled by a look at the pendant groups in the AFPs. Figure 10 shows the pendant groups from the 20 amino acids that are found in natural proteins. In proteins, the polyamide backbone is connected to pendant groups that can be hydrophilic or hydrophobic (Figure 11). They can also be anionic or cationic depending on the pH in

Figure 8. Structure of polyaspartamides, showing the two possible monomers that form.

reasonable scale inhibition (CaCO3 or Ba/SrSO4) as well as kinetic hydrate inhibition.57 The KHI performance of a series of poly(N-alkylglycine)s has been reported (Figure 9).58 A low molecular weight polymer

Figure 9. General structure of poly(N-alkylglycines) (left) and homopoly(β-peptoid)s (right).

with pendant n-propyl groups gave the best performance. These pseudo-polypeptides are susceptible to acid hydrolysis, but their biodegradation by the OECD306 test has not been carried out. The same is also true of a series of poly(β-peptoid)s, which are made by copolymerization of alkylated aziridine derivatives and carbon monoxide (Figure 9).59 In comparison to the poly(Nalkylglycine)s, these polymers performed worse as KHIs. This may be due to the extra backbone methylene group in each monomer unit creating a larger space between the pendant alkyl groups. 4.4. Proteins, Polypeptides, and Polyamino Acids. One of the very first ideas that led to today’s KHI technology came from antifreeze proteins and glycoproteins (AFPs and AFGPs) in fish and other organisms.2 These AFPs and AFGPs prevent ice crystals from forming by binding to the surface of ice nuclei.60−62 This allows the fish to survive in subzero temperatures. Insect AFPs, such as found in beetles or fleas, generally show greater ice inhibition activity than fish AFPs, lowering the freezing point of the body fluids by as much as 6 °C.63,64

Figure 11. Zwitterionization of amino acids in water.

the system. (In this diagram, the stereochemistry of the chiral amino acids pendant groups is not shown but could also be important for optimum KHI performance.) For example, among the hydrophobic groups, valine contains an isopropyl group and leucine an isobutyl group. Besides PNIPMAM, many other classes of polymer with these size of alkyl groups have been

Figure 10. Structure of polypeptides (above) and the hydrophobic (middle) and hydrophilic (bottom) side chains from natural amino acids. E


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through an MEG regeneration process. The KHI did not lose its performance. Evidence that proteins can survive elevated temperatures come from living microbes in oil deposits 3−4 km beneath the surface, or in geysers as so-called hyperthermophilic life. These microbes contain various proteins and can withstand enormous hydrocarbon loads, intense heat, high salt, and immense pressure.99,100 Artificial proteins and polypeptides could be tailor-made to function specifically as KHIs. This would require a good understanding of the KHI mechanism in order to get good performance. But the potential is there. My own research group has reported a small amount of work in this area.95 We designed and had made for us a few short polypeptides with several valine or leucine amino acid residues to give the polypeptides hydrophobic groups. Asparagine and/or histidine were used as comonomers to give the polypeptides water-solubility. Both showed some KHI effect using a Structure II-forming natural gas mixture, but the leucine polypeptide gave the better performance, fairly similar to PVP. We reasoned that the symmetry of any clathrate hydrate is high enough that one does not need many different amino acids residues as found in natural proteins, but that the correct amount and spacing of just 2 or perhaps 3 residues is enough to make a good KHI. Whatever the correct answer, bespoke or designer proteins synthesized from genemodified biotechnology may one day lead to very powerful KHIs. Another structural aspect that needs to be addressed is the chirality/stereochemistry of amino acids and the subsequent changes in the 3-dimensional structure of polypeptides which could affect KHI performance. Although homopolypeptides of natural amino acids are not found in nature, they could still act as KHIs. However, homopolypeptides such as those with hydrophobic groups shown on the middle row of Figure 10 are insoluble in water. Among those polypeptides with pendant hydrophilic groups, very few contain some hydrophobicity in the side chains and are still water-soluble. Some hydrophobicity is essential for KHI performance to either perturb the bulk water structure or interact with hydrate particle surfaces, whether sub- or supercritical nuclear size. Poly-L-proline (far right of the bottom row of Figure 10) stood out as a polypeptide worth investigating as a KHI as it has some structural similarities to PVP in that it contains a 5-membered ring and a ring heteroatom, nitrogen. This polymer gave a performance similar to PVP of similar molecular weight.2 4.5. Amino Acids. Most amino acids have fairly good water solubility despite some of them containing hydrophobic groups. Examples are leucine (iso-butyl), valine (iso-propyl), phenylalanine (benzyl), or tyrosine (4-hydroxybenzyl). This is because amino acids have the ability to self-ionize to form zwitterions (Figure 11). Only tryptophan (indolyl group) shows poor water solubility due to the large and fairly nonpolar indole group. One of the earliest ever studies on KHIs was by BP energy company with a study on the KHI performance of amino acids. Tyrosines and related chemicals gave some weak KHI effect, and the results were patented.101 BP tried a whole range of amino acids, none of which gave very good performance, so they moved on from this to more powerful KHIs such as polymers of the Nvinyl lactams, VP and VCap.2 The weak performance of amino acids is not surprising considering the wealth of evidence from many research groups which shows that multiple functional groups in a molecule (i.e., polymers but sometimes also oligomers) are critical to good KHI performance.1,4,6,53,102

shown to behave as good KHIs. Examples are poly(Nvinylamide)s, poly(N-alkylglycine)s, polymaleamides, poly(Nvinylcarbamate)s, and polyaspartamides.2,55,56,58,59,70,71 However, these polymers were not natural polymers and most showed limited biodegradability. Due to this realization, there have been efforts by a number of research groups to return to the natural proteins but with a view to find the best structures for kinetic hydrate inhibition rather than ice inhibition. For example, we recently, reported work on a cheap and natural protein-based product which was useful as a stand-alone KHI for low subcooling applications but could also be used to replace or reduce the amount of thermodynamic hydrate inhibitor (THI), such as MEG, where the THI pumping capacity has been reached.72 The high cost of producing AFPs on a large scale, even via GM technology, has not stopped a plethora of research projects being carried out on them.73−91 Certain AFPs have the ability to eliminate the memory effect from melted hydrates.92 One study provided further evidence that SI hydrates are coproduced with SII hydrates using a synthetic natural gas mixture.93 AFPs, or ice structuring proteins (ISPs) as they are also called, have been made in multi-kilo quantities by companies wishing to control the ice formation in ice cream, making the product smoother to eat. An example is the use of an AFP from the pouter fish manufactured on at least a 100 kg/year scale used gene-modification (GM) technology and added at about 50 ppm to the mixture before cooling to make ice cream.94 This product has been tested in my own laboratories as a KHI and shown to have a reasonable performance.95 However, the product is still much too expensive for field applications. However, all of these AFPs were created to modify or prevent ice formation, not gas hydrate formation. Therefore, it is not unreasonable to think that other natural proteins that were not designed to be AFPs might also function as KHIs. In fact, KHIs have even been found among proteins with no AFP activity.96 The AFPs or active fragments, originally isolated from fish, insects, plants, fungi, or bacteria, can presumably be made in an enzymatic process. Such a process would allow for large-scale manufacture, as isolation of large quantities of AFPs from these sources is prohibitively expensive. My own research group has investigated a range of natural protein-based products that are not designed to be AFPs. These products are low molecular weight partially hydrolyzed proteins such as peptones and tryptones. They are mainly products of wheat, beef, and milk proteins.95 The best of these products, such as casein peptones, gave better KHI performance than a low molecular weight PVP on a Structure II-forming natural gas mixture but not as good performance as PVCap. The performance of these protein-based products could be correlated to the percentage of hydrophobic groups (leucine, valine, etc.) and the molecular weight distribution. An interesting feature of protein-based products is that they also function as scale inhibitors, as they often contain a substantial amount of carboxylic acid groups from the aspartic acid or glutamic acid residues.97 Soya sauce containing soya proteins was shown to have a good KHI effect, even though it contains salts and other products that can have an additional thermodynamic effect.98 Although natural proteins are readily biodegradable, there has been concern that they may not have sufficient thermal stability for injection into hot well streams. Recently, we addressed this issue in a study on another natural protein-based KHI.72 This KHI was heated to 160 °C for 1 h in MEG to simulate passing F


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positive effect in the same test, and together these polymers led to a theory (later shown to be false) that ring structures might be critical for good performance.121,122 20 years later, HEC was also part of a KHI study on Structure I methane hydrates in blends with other polymers. The performance was generally weak compared to commercial KHIs described earlier in this review.123 Carboxymethylcellulose sodium salt (CMC-Na) has been claimed to be more than 300 times as efficient as methanol at the same dosage (Figure 12).124 The test method was isothermal, raising the pressure until hydrate formation occurs. The results suggest, for example, that 2−3 wt % methanol is about as efficient as 0.008 wt % CMC-Na. In my own laboratories, CMCNa has very little KHI effect, even at 0.5 wt %. This is also true for other polycarboxylate salts such as polyacrylate and polyaspartate sodium salts, indicating that carboxylate groups alone are not sufficient for polymers to exhibit good KHI performance.57 Other bioactive plant polysaccharides besides cellulose have been investigated for KHI activity. As stated in the section on graft polymers, polysaccharides, such as maltodextrins, have also been used as the biodegradable backbone for KHI graft polymers.42,43 Another example of polysaccharides is the xylomannans obtained from a beetle.125,126 Their performance was compared to a known AFP and PVP on methane hydrate, but they only showed fairly weak activity. Derivatives of chitosan (made by hydrolysis of chitin from the shells of crustaceans) have also been investigated as KHIs (Figure 13).127,128 In test with methane hydrate, the induction

However, in the past decade, several groups have revisited amino acids as KHIs, mainly from the perspective of finding environmentally friendly KHIs, also for studies on CO2 hydrate and CO2 sequestration. Some studies have also been done on amino acids as THIs. There appear to be some conflicting reports regarding amino acids as KHIs. In studies from one research group, amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure.103−105 In a study from another group, the feasibility of using amino acids as both potential KHI and THI for methane hydrate was investigated.106 The types of amino acids tested included L-alanine, L-phenylalanine, glycine, histidine, and Lasparagine. The experimental results obtained showed that the amino acids with lower solubility (i.e., most hydrophobic) provided a significant KHI effect, but no THI effect. However, the amino acids with higher solubility (most hydrophilic) provided both THI and KHI effects simultaneously. In contrast to this study, another group has proposed leucine as an environmentally benign kinetic promoter of methane hydrate formation.107 The same group also reported work on promotion of methane hydrate with three different types of amino acids tryptophan (aromatic, hydrophobic side group), histidine (aromatic but hydrophilic side group), and arginine (aliphatic hydrophilic side group). The best kinetic promotion for methane hydrate formation was achieved by tryptophan.108 In another study, the amino acids arginine and valine showed hydrate formation rate enhancement compared to pure water. In addition, the total methane uptake at the end of the experiments was increased in the presence of these amino acids.109 Similar results were found for valine and some other amino acids on CO2 hydrate.110 In another study on several water-soluble amino acids, alanine in particular showed some useful KHI synergy with PVCap or polyethylene oxide (PEO) on Structure I methane hydrate.111,112 Blends of tyrosine with PEO or polypropylene oxide have also been investigated, giving only weak KHI effects.113 Another group observed a synergy effect on preventing Structure I methane hydrate formation when glycine was mixed with PVCap.114 Amino acids have also been investigated as KHIs and THIs on ethane and CO 2 hydrate.115−119 4.6. Other Natural Polymers. Proteins are not the only natural polymer class that has been investigated for KHI performance. In fact, one of the very first polymers to show some KHI activity was a derivative of the natural polymer cellulose, called hydroxyethylcellulose (HEC) (Figure 12). HEC is on the PLONOR list of chemicals “Posing Little Or NO Risk” to the environment.120 HEC was tested for its ability to prevent tetrahydrofuran hydrate formation and agglomeration, but the positive effect was fairly weak compared to the best polymers known today. Poly(N-vinylpyrrolidone) (PVP) also gave a

Figure 13. Structure of chitosan.

time for gas hydrate formation increased with the degree of deacetylation of chitin to amine groups, up to 80% deacetylation. This seems at odds with general KHI theory that some hydrophobicity is needed in the pendant groups of a polymer for good KHI activity. The performance might have been better if the amine groups in chitosan had been converted to acylamide groups somewhat larger than acetamide, although water solubility might be a problem with increased hydrophobicity. Starch is another polysaccharide that has been tested as a KHI.129 As with many natural polymers, some KHI activity was found, but the performance was low. This was true even as a cationic modified starch, as well as in the presence of polyoxides such as polyethylene oxide or polypropylene oxide.130 Pectin is a family of heteropolysaccharides that contains Dgalacturonic acid units, some as methyl ester (Figure 14). The first reports on pectin as a KHI came from extracts taken from mango seeds. It showed good inhibition of THF hydrates.131,132 A later report on a different pectin source claimed that this product could inhibit Structure I methane hydrate at up to 12.5 °C subcooling, giving a better performance than PVCap.133 This was such a significant claim that we carried out our own work on pectins, and we report our findings here briefly for the first time. We bought commercial samples and extracted pectin from

Figure 12. Hydroxyethylcellulose (R = H or CH2CH2OH) or carboxymethylcellulose (R = H or CH2COOH). G


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means by this is that ionic liquids are polar solvents that could be used for many industrial reactions, but they have negligible vapor pressure compared to classic organic solvents. This means they are green with regards negligible pollution to the atmosphere.138,139 Ionic liquids can also be reused after separation of reaction products. This means there is little or no discharge of ionic liquids to the environment from industrialscale reactions, and in this sense, they also can be seen as green. However, most ionic liquids are relatively costly to manufacture compared to common organic solvents, and the most common ones are poorly biodegraded.140 This includes, tetra-nbutylammonium bromide (TBAB), the ethylimidazolium salt EMIM-Br, and pyridinium salts (Figure 15, middle, top, and bottom of left panel, respectively). Some ionic liquids are more biodegradable if hydrolyzable leaving groups are included but leave persistent metabolites, and some do pass as readily biodegradable. However, most available data is for biodegradation tests carried out in freshwater spiked with sewage, such as the OECD301 test, where the level of microorganisms that can contribute to biodegradation is much higher than in seawater. Many ionic liquids are also toxic.141−143 Therefore, although they are included in this review on green KHIs, the vast majority of ionic liquids do not possess the characteristics required for discharge in areas with strict environmental regulations. In addition, as we shall see below, ionic liquids are poor KHIs as you would expect for nonpolymeric molecules. Better inhibition is obtained for molecules with multiple functional groups, i.e., oligomers or polymers. For example, homopolymers of 3-alkyl1-vinylimidazolium bromides and tributylammoniumethyl acrylate bromide (TBAEABr), with many pendant groups similar to those found in ionic liquids, gave good KHI performance in THF hydrate and gas hydrate experiments.144 However, it is doubtful that these polyvinyl derivatives show good biodegradability. A review published in 2014 summarizes the recent advances in ionic liquid research as dual-function gas hydrate inhibitors, i.e., KHI and/or THI effects.145 Most of the review looks at ionic liquids as THIs. References therein to ionic liquids as KHIs often refer to reports using test conditions and test methods quite different to those found in oilfield production scenarios. For example, the KHI activity of the imidazolium salts [EMIM]-

Figure 14. Repeating unit in pectin.

mango skins and seeds. All the samples we isolated gave negligible effect on THF hydrate crystal growth inhibition, Structure I methane hydrate inhibition, and gas hydrate inhibition with a Structure II-forming synthetic natural gas mixture using test methods we have reported previously.134,135 It is possible the pectin samples reported by others contained other components not present in our samples. Pancreatic lipase, which is a lipolytic enzyme, is possibly the most complex polymeric substance tested as a KHI.136,137 Pancreatic lipase was found to be a better inhibitor than PVP for THF hydrates and also suppressed the “memory effect” more efficiently. It was investigated with a view to using it as a green hydrate inhibitor in drilling fluids. 4.7. Ionic Liquids. An ionic liquid is a salt in which the ions are poorly coordinated, which results in these solvents being liquid below about 100 °C, or even at room temperature (room temperature ionic liquids, RTILs). This definition therefore includes quaternary ammonium salts such as tetra-n-butylammonium bromide (TBAB) and tetra-n-pentylammonium bromide (TPAB) which are solids at room temperature but melt at 103 and 101 °C, respectively. More classical ionic liquids include salts of the cations 1-alkyl-3-methylimidazolium, 1-alkylpyridinium, and N-methyl-N-alkylpyrrolidinium (Figure 15, top left, bottom left, and bottom right, respectively). The anions can be simple halides, which generally suffer high melting points, to inorganic anions such as tetrafluoroborate and hexafluorophosphate, and to large organic anions like triflate, tosylate, formate, alkylsulfate, or even glycolate. Ionic liquids are sometimes touted as green chemicals or green solvents for clean synthesis. What the literature usually

Figure 15. Ionic liquids: poorly biodegradable (top row), more biodegradable but leave persistent metabolites (middle row), readily biodegradable to CO2 (bottom row). H


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[BF4] and [BMIM][BF4] were originally reported as being high (Figure 16).146−148 A later study under more realistic conditions

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +47 51831823. Fax: +47 51831750. E-mail: malcolm. [email protected]. ORCID

Malcolm A. Kelland: 0000-0003-2295-5804 Notes

Figure 16. 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4, left) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4, right).

The author declares no competing financial interest.

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REFERENCES

(1) Kelland, M. A. Energy Fuels 2006, 20, 825. (2) Sloan, E. D.; Koh, C. A. Clathrate Hydrates of Natural Gases, 3rd ed.; CRC Press: Boca Raton, FL, 2008; Vol. 119. (3) Sloan, E. D. Natural Gas Hydrates in Flow Assurance; Elsevier Gulf Professional Publishing: Amsterdam, Netherlands, 2011. (4) Kelland, M. A. Production Chemicals for the Oil and Gas Industry, 2nd ed.; CRC Press: Boca Raton, FL, 2014; DOI: 10.1201/b16648. (5) Shahnazar, S.; Bagheri, S.; Termeh Yousefi, A.; Mehrmashhadi, J.; Abd Karim, M. S.; Kadri, N. A. Rev. Inorg. Chem. 2018, 38 (1), 1−19. (6) Kelland, M. A. A review of kinetic hydrate inhibitors - Tailormade water-soluble polymers for oil and gas industry applications. In Advances in Materials Science Research; Wytherst, M. C., Ed.; Nova Science Publishers, Inc.: New York, 2011; Vol. 8, Chapter 5. (7) Swift, G. Degradability of commodity plastics and specialty polymers: An overview. In Agricultural and synthetic polymers, biodegradability and utilization; ACS Symposium Series; Glass, J. E., Swift, G., Eds.; American Chemical Society: Washington, DC, 1990; pp 2−12. (8) Chiellini, E.; Corti, A.; D’Antone, S.; Solaro, R. Prog. Polym. Sci. 2003, 28 (6), 963−1014. (9) OSPAR. Guidelines for Completing the Harmonised Offshore Chemical Notification Format (2005-13). http://www.ospar.org. (10) Glover, S.; Still, I. HMCS (Harmonised Mandatory Control Scheme) and the Issue of Substitution. In Ninth Annual International Petroleum Environmental Conference, Albuquerque, NM, Oct 22−25, 2002. (11) Thatcher, M.; Payne, G. Impact of the OSPAR Decision on the Harmonised Mandatory Control System on the Offshore Chemical Supply Industry. In Proceedings of the Chemistry in the Oil Industry VII Symposium, Manchester, U.K., Nov 13−14, 2001; Royal Society of Chemistry: Cambridge, U.K., 2002. (12) Madigan, M.; Martinenko, J.; Stahl, D.; Clark, D. Biology of microorganisms, 13th ed.; Pearson Education Inc.: San Francisco, CA, 2012. (13) Klomp, U. C. International Patent Application WO/2001// 77270, 2001. (14) Del Villano, L.; Kelland, M. A. Chem. Eng. Sci. 2009, 64, 3197− 3200. (15) Klomp, U. C. International Patent Application WO/2013/ 096212, 2013. (16) Klomp, U. C. International Patent Application WO/2013/ 096205, 2013. (17) Klomp, U. C. International Patent Application WO/2013/ 096201, 2013. (18) Rivers, G. T.; Crosby, D. L. International Patent Application WO2004/022909, 2004. (19) Fu, B. The Development of Advanced Kinetic Hydrate Inhibitors. In Proceedings of Chemistry in the Oil Industry VII, Manchester, U.K., Nov 13−14, 2002; Royal Society of Chemistry, 2002; p 264. (20) Cohen, J. M.; Wolf, P. F.; Young, W. D. U.S. Patent Application 5,723,524, 1998. (21) Clements, J.; Pakulski, M. K.; Riethmeyer, J.; Lewis, D. C. International Patent Application WO2017048424, 2017. (22) Organisation for Economic Co-operation and Development (OECD). OECD Guideline for Testing of Chemicals: Biodegradability in Seawater; OECD: Paris, France, July 17, 2002; p 27.

of temperature, subcooling, and reactor design indicated that theses ionic liquids provide no kinetic inhibition effect; instead, they catalyzed the gas hydrate formation process.149 However, they did exhibit a positive synergistic effect with commercial hydrate inhibitors like PVCap in the same way as tetra-nbutylammonium bromide. These two ionic liquids were also subjected to the OECD306 seawater biodegradation test. After 28 days using duplicate bottles, neither chemical showed any sign of biodegradation. Sodium benzoate gave a 28 day biodegradation of about 91−96% without assimilation under identical conditions. Another imidazolium salt, 1-hexyl-1-methylpyrrolidinium tetrafluoroborate (HMP-BF4), gave good KHI synergy performance with PVCap.150 When used alone, this ionic liquid exhibited much lower natural gas hydrate inhibition performance than PVCap. Other similar synergistics blends have also been reported.151 Another study observed that N-hydroxyethylN-methylpyrrolidine tetrafluoroborate [HEMP][BF4] was a better synergist with PVCap on SI hydrate than N-butyl-Nmethylpyrrolidine tetrafluoroborate.152,153 Ionic liquids of 1-hydroxyethyl-1-methylmorpholinium chloride (HEMM-Cl) and 1-hydroxyethyl-1-methylmorpholinium tetrafluoroborate (HEMM-BF4) have been investigated for kinetic promotion and thermodynamic inhibition of methane hydrate formation.154 Another study reported on methane hydrate inhibition in the presence of five structurally variable ionic liquids (ILs) belonging to the ammonium familyviz., tetra-alkylammonium acetate (TMAA), choline butyrate (ChBut), choline iso-butyrate (Ch-iB), choline hexanoate (ChHex), and choline octanoate (Ch-Oct).155 A study in a high pressure micro differential scanning calorimeter showed that some ionic liquids gave greater KHI inhibition power than PVP, but other ionic liquids promoted methane hydrate formation.156

5. CONCLUSION The best readily biodegradable polymers studied to date give a poorer KHI performance than the best commercial KHI polymers. However, some categories of polymers discussed here that are not commercially available have not been tested for biodegradability. Pectin extracts from fruit are the only natural polymers that have been reported to have higher KHI performance than the benchmark PVCap, but more work is needed to confirm these results and the exact nature of the extracts. Currently, it appears that one of the best biodegradable KHIs is a graft polymer with a biodegradable backbone with pendant caprolactam groups. Other biodegradable KHIs include a natural protein-based product and polypyroglutamates. In the long term, it may be possible to design and make a highperformance protein-based KHI using biotechnology, although due to the cost of production and size of the demand for KHI, this is currently not economically viable. I


Review

Energy & Fuels (23) Talley, L. D.; Colle, K. International Patent Application WO/ 2006/110192, 2006. (24) Kaasa, B.; Hemmingsen, P. V. International Patent Application WO/2013/041143, 2013. (25) Moen, K.; Calvo, A. S. International Patent Application WO/ 2013/093789, 2013. (26) Xu, S. R.; Fan, S. S.; Wang, Y. H.; Lang, X. M. Chem. Eng. Sci. 2017, 171, 293−302. (27) Rithauddeen, M. A.; Al-Adel, S. I.; Mohammad, A. F. International Patent Application WO/2017/053269, 2017. (28) Anderson, R.; Tohidi, F.; Mozaffar, H.; Tohidi, B. J. Pet. Sci. Eng. 2016, 145, 520−526. (29) Anderson, R.; Tohidi, B. International Patent Application WO/ 2015/022480, 2015. (30) Tian, J.; Bailey, C. T. International Patent Application WO/ 2011/123341, 2011. (31) Schrader, G. A. International Patent Application WO/2012/ 041785, 2012. (32) Hussain, A.; Gharfeh, S.; Adham, S. Study of Kinetic Hydrate Inhibitor Removal Efficiency by Physical and Chemical Processes. In SPE International Production and Operations Conference & Exhibition, Doha, Qatar, May 14−16, 2012; SPE, 2012; SPE-157146-MS. DOI: 10.2118/157146-MS (33) Spencer, H. J.; Lehmann, M. N.; Ionescu, T. C.; Garza, T. Z.; Jackson, S. J. International Patent Application WO/2012/135116, 2012. (34) Minier-Matar, J.; Gharfeh, S.; Hussain, A.; Adham, S. U.S. Patent Application 20160376171, 2016. (35) Bartels, J. W.; Jones, R. A.; Lucente-Schultz, R. M. U.S. Patent Application US20170225978, 2017. (36) Maximilian, A.; Neubecker, K.; Sanner, A. U.S. Patent 6,867,262, 2005. (37) Widmaier, R.; Wegmann, L.; Mauri, A.; Mathauer, K.; Jahnel, W.; Herrera, T. L.; Neubecker, K.; Khvorost, A. International Patent Application WO/2007/051742, 2007. (38) Reichenbach-Klinke, R.; Neubecker, K. International Patent Application, WO/2009/083377, 2009. (39) Frenzel, S.; Assmann, A.; Reichenbach-Klinke, R. Green Polymers For The North Sea − Biodegradability As Key Towards Environmentally Friendly Chemistry For The Oilfield Industry. In Proceedings of the RSC Chemistry In The Oil Industry XI, Manchester, U.K., Nov 2−4, 2009; Royal Society of Chemistry, 2009. (40) Daraboina, N.; Pachitsas, S.; von Solms, N. Fuel 2015, 139, 554− 560. (41) Patil, D. R.; Fan, G. L.; Fan, J. C.; Yu, J. U.S. Patent Application 20090326165, 2009. (42) Holt, S.; Thomaides, J. S. International Patent Application WO/ 2012/089654, 2012. (43) Holt, S.; Unebäck, I. Kinetic Hydrate Inhibitors with Improved Biodegradation. In Tekna 23rd International Oil Field Chemistry Symposium, Geilo, Norway, March 18−21, 2012; (Tekna) The Norwegian Society of Graduate Technical and Scientific Professionals, 2012. (44) Musa, O. M.; Cuiyue, L. International Patent Application, WO/ 2010/114761, 2010. (45) Musa, O. M.; Cuiyue, L.; Zheng, J.; Alexandre, M. M. Advances in Kinetic Gas Hydrate Inhibitors. In Proceedings of RSC Chemistry in the Oil Industry XI, Manchester, U.K., Nov 2−4, 2009; Royal Society of Chemistry, 2009. (46) Leinweber, D.; Feustel, M. International Patent Application WO/2006/084613, 2006. (47) Leinweber, D.; Feustel, M. International Patent Application WO/2007/054226, 2007. (48) Arjmandi, M.; Leinweber, D.; Allan, K. Development of A New Class of Green Kinetic Hydrate Inhibitors. In The 19th International Oilfield Chemical Symposium, Geilo, Norway, March, 2008; (Tekna) The Norwegian Society of Graduate Technical and Scientific Professionals, 2008.

(49) Leinweber, D.; Feustel, M. U.S. Patent Application 20080214865, 2008. (50) Leinweber, D.; Roesch, A. R.; Feustel, M. U.S. Patent Application 20090054268, 2009. (51) Cole, R. A.; Grinrod, A.; Cely, A. International Patent Application WO/2014/078163, 2014. (52) Gonzáles, R.; Djuve, J. International Patent Application WO/ 2010/101477, 2010. (53) Reyes, F. T.; Kelland, M. A.; Sun, L.; Dong, J. Energy Fuels 2015, 29, 4774−4782. (54) Lodish, H.; Berk, A.; Matsudaira, P.; Kaiser, C. A.; Krieger, M.; Scott, M. P.; Zipurksy, S. L.; Darnell, J. Molecular Cell Biology, 5th ed.; WH Freeman and Company: New York, NY, 2004. (55) Del Villano, L.; Kommedal, R.; Kelland, M. A. Energy Fuels 2008, 22, 3143. (56) Kelland, M. A. Additives for Inhibiting Gas Hydrate Formation. International Patent Application WO/2008/023989, 2008. (57) Chua, P. C.; Sæbø, M.; Lunde, L.; Kelland, M. A. Energy Fuels 2011, 25, 5165. (58) Reyes, R. T.; Guo, L.; Hedgepeth, J. W.; Zhang, D.; Kelland, M. A. Energy Fuels 2014, 28, 6889−6896. (59) Reyes, R. T.M.; Kelland, M. A.; Kumar, N.; Jia, L. Energy Fuels 2015, 29, 695−701. (60) Voets, I. K. From Ice-binding Proteins to Bio-Inspired Antifreeze Materials. Soft Matter 2017, 13, 4808. (61) Yeh, Y.; Feeney, R. Chem. Rev. 1996, 96 (2), 601−618. (62) Venketesh, S.; Dayananda, C. Properties, potentials, and prospects of antifreeze proteins. Crit. Rev. Biotechnol. 2008, 28, 57−82. (63) Lin, F. H.; Graham, L. A.; Campbell, R. L.; Davies, P. L. Biophys. J. 2007, 92, 1717−1723. (64) Graham, L. A.; Davies, P. L. Science 2005, 310, 461. (65) Wen, D. Y.; Laursen, R. A. A Model for Binding of an Antifreeze Polypeptide to Ice. Biophys. J. 1992, 63 (6), 1659−1662. (66) Kristiansen, E.; Zachariassen, K. E. The Mechanism by Which Fish Antifreeze Proteins Cause Thermal Hysteresis. Cryobiology 2005, 51 (3), 262−280. (67) Ohno, H.; Susilo, R.; Gordienko, R.; Ripmeester, J.; Walker, V. K. Interaction of Antifreeze Proteins with Hydrocarbon Hydrates. Chem. Eur. J. 2010, 16 (34), 10409−10417. (68) Edwards, A. R. In Proceedings of the 1st International Conference on Natural Gas Hydrates; New York Academy of Sciences: New York, 1994; p 543. (69) Anselme, M. J.; Reijnhout, M. J.; Klomp, U. C. WO Patent Application 93/25798, 1993. (70) Zhang, Q.; Kawatani, R.; Ajiro, H.; Kelland, M. A. Energy Fuels 2018, 32, 4925−4931. (71) Kelland, M. A.; Abrahamsen, E.; Ajiro, H.; Akashi, M. Energy Fuels 2015, 29, 4941−4946. (72) Magnusson, C.; Abrahamsen, E.; Kelland, M. A.; Cely, A.; Kinnari, K.; Li, X.; Askvik, K. M. As Green As It Gets: An Abundant Kinetic Hydrate Inhibitor from Nature. Energy Fuels 2018, 32, 5772− 5778. (73) Walker, V. K.; Zeng, H.; Ohno, H.; Daraboina, N.; Sharifi, H.; Bagherzadeh, S. A.; Alavi, S.; Englezos, P. Antifreeze proteins as gas hydrate inhibitors. Can. J. Chem. 2015, 93 (8), 839−849. (74) (a) Walker, V.; Ripmeester, J. A.; Zeng, H. International Patent Application WO03/087532, 2003. (b) Zeng, H.; Brown, A.; Wathen, B.; Ripmeester, J. A.; Walker, V. K. Antifreeze Proteins: Adsorption to Ice, Silica and Gas Hydrates. In Proceedings of the 5th International Conference on Gas Hydrates (ICGH 2005), Trondheim, Norway, June 13−16; Tapir: Trondheim, 2005. (75) Daraboina, N.; Ripmeester, J.; Walker, V. K.; Englezos, P. Energy Fuels 2011, 25, 4392. (76) Daraboina, N.; Linga, P.; Ripmeester, J.; Walker, V. K.; Englezos, P. Energy Fuels 2011, 25, 4384. (77) Jensen, L.; Thomsen, K.; von Solms, N. Energy Fuels 2011, 25, 17. (78) Jensen, L.; Ramløv, H.; Thomsen, K.; von Solms, N. Ind. Eng. Chem. Res. 2010, 49 (4), 1486−1492. J


Review

Energy & Fuels

(99) Gerday, C.; Glansdorff, N. Physiology and Biochemistry of Extremophiles; ASM Press: Washington, DC, 2007. (100) Singh, O. V. Extremophiles: Sustainable Resources and Biotechnological Implications; Wiley-Blackwell: Hoboken, NJ, 2012. (101) Duncum, S.; Edwards, A. R.; Osborne, C. G. European Patent Application 0536950 A1, 1993. (102) Perrin, A.; Musa, O. M.; Steed, J. W. The Chemistry of Low Dosage Clathrate Hydrate Inhibitors. Chem. Soc. Rev. 2013, 42, 1996− 2015. (103) Sa, J.-H.; Kwak, G. H.; Lee, B. R.; Park, D. H.; Han, K.; Lee, K. H. Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation. Sci. Rep. 2013, 3, 2428. (104) Sa, J.-H.; Lee, B.; Park, D.-H.; Han, K.; Chun, H. D.; Lee, K.-H. Amino acids as natural inhibitors for hydrate formation in CO2 sequestration. Environ. Sci. Technol. 2011, 45, 5885−5891. (105) Sa, J. H.; Kwak, G. H.; Han, K.; Ahn, D.; Cho, S. J.; Lee, J. D.; Lee, K. H. Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids. Sci. Rep. 2016, 6, 31582. (106) Atilhan, M.; AlTamash, T.; Qureshi, F.; Tohidi, B.; Aparicio, S. Effect of Low-Dosage Aminoacids Based Kinetic Hydrate Inhibitors. In 17th AIChE Spring Meeting and Global Congress on Process Safety, San Antonio, TX, March 24−28, 2017; American Institute of Chemical Engineers, 2017. (107) Veluswamy, H. P.; Kumar, A.; Kumar, R.; Linga, P. An innovative approach to enhance methane hydrate formation kinetics with leucine for energy storage application. Appl. Energy 2017, 188, 190−199. (108) Veluswamy, H. P.; Lee, P. Y.; Premasinghe, K.; Linga, P. Effect of bio-friendly amino acids on the kinetics of methane hydrate formation and dissociation. Ind. Eng. Chem. Res. 2017, 56 (21), 6145− 6154. (109) Bavoh, C. B.; Nashed, O.; Khan, M. S.; Partoon, B.; Lal, B.; Sharif, A. M. The impact of amino acids on methane hydrate phase boundary and formation kinetics. J. Chem. Thermodyn. 2018, 117, 48− 53. (110) Prasad, P. S. R.; Kiran, B. S. Are the amino acids thermodynamic inhibitors or kinetic promoters for carbon dioxide hydrates? J. Nat. Gas Sci. Eng. 2018, 52, 461−466. (111) Altamash, T.; Qureshi, M. F.; Aparicio, S.; Aminnaji, M.; Tohidi, B.; Atilhan, M. Gas hydrates inhibition via combined biomolecules and synergistic materials at wide process conditions. J. Nat. Gas Sci. Eng. 2017, 46, 873−883. (112) Qureshi, M. F.; Atilhan, M.; Altamash, T.; Tariq, M.; Khraisheh, M.; Aparicio, S.; Tohidi, B. Gas Hydrate Prevention and Flow Assurance by Using Mixtures of Ionic Liquids and Synergent Compounds: Combined Kinetics and Thermodynamic Approach. Energy Fuels 2016, 30, 3541−3548. (113) Talaghat, M. R. Fluid Phase Equilib. 2010, 289, 129. (114) Xu, S.; Fan, S.; Fang, S.; Wang, Y.; Lang, X. Fuel 2017, 206, 19− 26. (115) Rad, S. A.; Khodaverdiloo, K. R.; Karamoddin, M.; Varaminian, F.; Peyvandi, K. Kinetic study of amino acids inhibition potential of glycine and l-leucine on the ethane hydrate formation. J. Nat. Gas Sci. Eng. 2015, 26, 819−826. (116) Naeiji, P.; Arjomandi, A.; Varaminian, F. Kinetic study of amino acids inhibition potential of glycine and l-leucine on the ethane hydrate formation. J. Nat. Gas Sci. Eng. 2014, 21, 64−70. (117) Roosta, H.; Dashti, A.; Mazloumi, S. H.; Varaminian, F. The dual effect of amino acids on the nucleation and growth rate of gas hydrate in ethane plus water, methane plus propane plus water and methane plus THF plus water systems. Fuel 2018, 212, 151−161. (118) Roosta, H.; Dashti, A.; Mazloumi, S. H.; Varaminian, F. Inhibition properties of new amino acids for prevention of hydrate formation in carbon dioxide−water system: Experimental and modeling investigations. J. Mol. Liq. 2016, 215, 656−663. (119) Bavoh, C. B.; Partoon, B.; Lal, B.; Gonfa, G.; Khor, S. F.; Sharif, A. M. Chem. Eng. Sci. 2017, 171, 331−339. (120) https://www.cefas.co.uk/media/1384/13-06e_plonor.pdf.

(79) Ohno, H.; Susilo, R.; Gordienko, R.; Ripmeester, J.; Walker, V. K. Chem. - Eur. J. 2010, 16 (34), 10409−10417. (80) Zeng, H.; Wilson, L. D.; Walker, V. K.; Ripmeester, J. A. Effect of antifreeze proteins on the nucleation, growth, and the memory effect during tetrahydrofuran clathrate hydrate formation. J. Am. Chem. Soc. 2006, 128, 2844−2850. (81) Sun, T. J.; Davies, P. L.; Walker, V. K. Structural Basis for the Inhibition of Gas Hydrates by alpha-Helical Antifreeze Proteins. Biophys. J. 2015, 109 (8), 1698−1705. (82) Daraboina, N.; Perfeldt, C. M.; von Solms, N. Testing antifreeze protein from the longhorn beetle Rhagium mordax as a kinetic gas hydrate inhibitor using a high-pressure micro differential scanning calorimeter. Can. J. Chem. 2015, 93, 1025−1030. (83) Cruz-Torres, A.; Romero-Martínez, A.; Galano, A. Computational study on the antifreeze glycoproteins as inhibitors of clathratehydrate formation. ChemPhysChem 2008, 9, 1630−1635. (84) Bagherzadeh, S. A.; Alavi, S.; Ripmeester, J. A.; Englezos, P. Why ice-binding type I antifreeze protein acts as a gas hydrate crystal inhibitor. Phys. Chem. Chem. Phys. 2015, 17, 9984−9990. (85) Zhou, H. X.; Ferreira, C. I. Effect of type-III Anti-Freeze Proteins (AFPs) on CO2 hydrate formation rate. Chem. Eng. Sci. 2017, 167, 42− 53. (86) Sharifi, H.; Walker, V. K.; Ripmeester, J.; Englezos, P. Insights into the Behavior of Biological Clathrate Hydrate Inhibitors in Aqueous Saline Solutions. Cryst. Growth Des. 2014, 14, 2923−2930. (87) Sharifi, H.; Walker, V. K.; Ripmeester, J.; Englezos, P. Inhibition Activity of Antifreeze Proteins with Natural Gas Hydrates in Saline and the Light Crude Oil Mimic, Heptane. Energy Fuels 2014, 28, 3712− 3717. (88) Perfeldt, C.; Chua, P. C.; Daraboina, N.; Friis, D.; Kristiansen, E.; Ramløv, H.; Woodley, J. M.; Kelland, M. A.; von Solms, N. Inhibition of Gas Hydrate Nucleation and Growth: Efficacy of an Antifreeze Protein from the Longhorn Beetle Rhagium mordax, Malmos. Energy Fuels 2014, 28, 3666−3672. (89) Sharifi, H.; Ripmeester, J.; Englezos, P. Recalcitrance of gas hydrate crystals formed in the presence of kinetic hydrate inhibitors. J. Nat. Gas Sci. Eng. 2016, 35, 1573−1578. (90) Gordienko, R.; Ohno, H.; Singh, V. K.; Jia, Z.; Ripmeester, J. A.; Walker, V. K. Towards a Green Hydrate Inhibitor: Imaging Antifreeze Proteins on Clathrates. PLoS One 2010, 5 (2), No. e8953. (91) Udegbunam, L. U.; DuQuesnay, J. R.; Osorio, L.; Walker, V. K.; Beltran, J. G. Phase equilibria, kinetics and morphology of methane hydrate inhibited by antifreeze proteins: application of a novel 3-in-1 method. J. Chem. Thermodyn. 2018, 117, 155−163. (92) Walker, V. K.; Zeng, H.; Gordienko, R.; Kuiper, M.; Huva, E.; Wu, Z.; Miao, D.; Ripmeester, J. The Mysteries of the Memory Effect and Its Elimination with Antifreeze Proteins. In Proceedings of the 6th International Conference on Gas Hydrates (ICGH), Vancouver, British Columbia, Canada, July 6−10; University of British Columbia: Vancouver, 2008. (93) Daraboina, N.; Ripmeester, J.; Walker, V. K.; Englezos, P. Energy Fuels 2011, 25, 4398. (94) Meldolesi, A. Nat. Biotechnol. 2009, 27, 682. (95) Kelland, M. A.; Zhang, Q.; Chua, P. C. A Study of Natural Proteins and Partially Hydrolyzed Derivatives as Green Kinetic Hydrate Inhibitors. Energy Fuels 2018, 32, 9349−9357. (96) Myran, D.; Middleton, A.; Choi, J.; Gordienko, R.; Ohno, H.; Ripmeester, J. A.; Walker, V. K.Genetically-Engineered Mutant Antifreeze Proteins Provide Insight into Hydrate Inhibition. In Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), Edinburgh, Scotland, U.K., July 17−21, 2011, https://www.pet. hw.ac.uk/icgh7/. (97) Mady, M. F.; Kelland, M. A. Study on Various Readily Available Proteins as New Green Scale Inhibitors for Oilfield Scale Control. Energy Fuels 2017, 31, 5940−5947. (98) Li, X.; Askvik, K. M.; Yi, Y.; Kelland, M. A.; Magnusson, C. D. Testing of Soya Sauce and Soya Proteins as Kinetic Hydrate Inhibitors. In Proceedings of the 8th International Conference on Gas Hydrates (ICGH8-2014), Beijing, China, July 28−August 1, 2014. K


Review

Energy & Fuels (121) Sloan, E. D. U.S. Patent 5,420,370, May 30, 1995. (122) Long, J.; Lederhos, J.; Sum, A.; Christiansen, R. L.; Sloan, E. D. In Proceedings of the 73rd Annual GPA Convention, New Orleans, LA, March 7−9, 1994. (123) Jokandan, E. F.; Naeiji, P.; Varaminian, F. The synergism of the binary and ternary solutions of polyethylene glycol, polyacrylamide and hydroxyethyl cellulose to methane hydrate kinetic inhibitor. J. Nat. Gas Sci. Eng. 2016, 29, 15−20. (124) Ishmuratov, F. G.; Rakhimova, N. T.; Ishmiyarov, E. R.; Voloshin, A. I.; Gusakov, V. N.; Tomilov, Yu. V.; Nifant’yev, N. E.; Dokichev, V. A. New ″Green″ Polysaccharidal Inhibitor of Gas Hydrate Formation on the Basis of Carboxymethylcellulose Sodium Salt. Russ. Russ. J. Appl. Chem. 2018, 91, 653−656. (125) Ivall, J.; Servio, P. Next-Generation Anti-freeze Hydrate Inhibitors Based on the Xylomannan Compound. In Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), Edinburgh, Scotland, U.K., July 17−21, 2011, https://www.pet.hw.ac. uk/icgh7/. (126) Liu, J.; Willför, S. M.; Xu, C. A review of bioactive plant polysaccharides: Biological activities, functionalization, and biomedical applications. Bioact. Carbohydr. Diet. Fibre 2015, 5 (1), 31−61. (127) Xu, Y. J.; Yang, M. L.; Yang, X. X. J. Nat. Gas Chem. 2010, 19, 431−435. (128) Zargar, V.; Asghari, M.; Dashti, A. A Review on Chitin and Chitosan Polymers: Structure, Chemistry, Solubility, Derivatives, and Applications. ChemBioEng Rev. 2015, 2 (3), 204−226. (129) Lee, J. D.; Wu, H. J.; Englezos, P. Chem. Eng. Sci. 2007, 62, 6548. (130) Talaghat, M. R. Enhancement of the performance of modified starch as a kinetic hydrate inhibitor in the presence of polyoxides for simple gas hydrate formation in a flow mini-loop apparatus. J. Nat. Gas Sci. Eng. 2014, 18, 7−12. (131) Yánez, F.; Chillón, D.; Orta, L.; Landaeta, F. New Insights for THF Hydrates Detection And Non-Conventional Inhibitors Evaluation. In Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), Edinburgh, Scotland, U.K., July 17−21, 2011, https:// www.pet.hw.ac.uk/icgh7/. (132) Biomorgi, J.; Carrasquero, M. A.; Torín, E.; Nadales, R.; Viloria, A. A New Approach to a Green Chemical Treatment for Hydrates Suppression. In Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011), Edinburgh, Scotland, U.K., July 17−21, 2011, https://www.pet.hw.ac.uk/icgh7/. (133) Xu, S. R.; Fan, S. S.; Fang, S. T.; Lang, X. M.; Wang, Y. H.; Chen, J. Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor. Sci. Rep. 2016, 6, 23220. (134) Abrahamsen, E.; Kelland, M. A. Energy Fuels 2018, 32, 342− 351. (135) Kelland, M. A.; Mady, M. F. Energy Fuels 2016, 30, 3934−3940. (136) Chapus, C.; Rovery, M.; Sarda, L.; Verger, R. Minireview on pancreatic lipase and colipase. Biochimie 1988, 70 (9), 1223−34. (137) Saikia, T.; Mahto, V. Experimental investigations of clathrate hydrate inhibition in water based drilling fluid using green inhibitor. J. Pet. Sci. Eng. 2016, 147, 647−653. (138) Nelson, W. M. Are Ionic Liquids Green Solvents? In Ionic Liquids; ACS Symposium Series; American Chemical Society: Washington, DC, 2002; Vol. 818, Chapter 3, pp 30−41. (139) Shiflett, M. B., Scurto, A. M., Eds. Ionic Liquids: Current State and Future Directions; ACS Symposium Series; American Chemical Society: Washington, DC, 2017; Vol. 1250. (140) Jordan, A.; Gathergood, N. Biodegradation of ionic liquids − a critical review. Chem. Soc. Rev. 2015, 44, 8200−8237. (141) Pham, T. P. T.; Cho, C.-W.; Yun, Y.-S. Environmental fate and toxicity of ionic liquids: A review. Water Res. 2010, 44, 352−372. (142) Bubalo, M. C.; Radošević, K.; Redovniković, I. R.; Slivac, I.; Srček, V. G. Toxicity mechanisms of ionic liquids. Arh. Hig. Rada Toksikol. 2017, 68, 171−179. (143) Zhao, D.; Liao, Y.; Zhang, Z. Toxicity of Ionic Liquids. Clean: Soil, Air, Water 2007, 35, 42−48. (144) Nakarit, C.; Kelland, M. A.; Liu, D.; Chen, E. Y.-X. Cationic kinetic hydrate inhibitors and the effect on performance of

incorporating cationic monomers into N-vinyl lactam copolymers. Chem. Eng. Sci. 2013, 102, 424−431. (145) Tariq, M.; Rooney, D.; Othman, E.; Aparicio, S.; Atilhan, M.; Khraisheh, M. Gas Hydrate Inhibition: A Review of the Role of Ionic Liquids. Ind. Eng. Chem. Res. 2014, 53, 17855−17868. (146) Xiao, C.; Adidharma, H. Dual function inhibitors for methane hydrate. Chem. Eng. Sci. 2009, 64, 1522−1527. (147) Xiao, C.; Wibisono, N.; Adidharma, H. Dialkylimidazolium halide ionic liquids as dual function inhibitors for methane hydrate. Chem. Eng. Sci. 2010, 65, 3080−3087. (148) Adidharma, H.; Xiao, C. International Patent Application WO/ 2009/114674, 2009. (149) Del Villano, L.; Kelland, M. A. An investigation into the kinetic hydrate inhibitor properties of two imidazolium-based ionic liquids on Structure II gas hydrate. Chem. Eng. Sci. 2010, 65, 5366−5372. (150) Lee, W.; Shin, J. Y.; Kim, K.-S.; Kang, S.-P. Synergetic Effect of Ionic Liquids on the Kinetic Inhibition Performance of Poly(Nvinylcaprolactam) for Natural Gas Hydrate Formation. Energy Fuels 2016, 30, 9162−9169. (151) Lee, W.; Shin, J. Y.; Cha, J. H.; Kim, K. S.; Kang, S. P. Inhibition effect of ionic liquids and their mixtures with poly(N-vinylcaprolactam) on methane hydrate formation. J. Ind. Eng. Chem. 2016, 38, 211−216. (152) Kang, S. P.; Kim, E. S.; Shin, J. Y.; Kim, H. T.; Kang, J. W.; Cha, J. H.; Kim, K. S. Unusual synergy effect on methane hydrate inhibition when ionic liquid meets polymer. RSC Adv. 2013, 3, 19920−19923. (153) Kang, S.-P.; Jung, T.; Lee, J.-W. Chem. Eng. Sci. 2016, 143, 270− 275. (154) Lee, W.; Shin, J.-Y.; Kim, K.-S.; Kang, S.-P. Kinetic Promotion and Inhibition of Methane Hydrate Formation by Morpholinium Ionic Liquids with Chloride and Tetrafluoroborate Anions. Energy Fuels 2016, 30, 3879−3885. (155) Tariq, M.; Connor, E.; Thompson, J.; Khraisheh, M.; Atilhan, M.; Rooney, D. Doubly dual nature of ammonium-based ionic liquids for methane hydrates probed by rocking-rig assembly. RSC Adv. 2016, 6 (28), 23827−23836. (156) Nashed, O.; Sabil, K. M.; Ismail, L.; Japper-Jaafar, A.; Lal, B. Mean induction time and isothermal kinetic analysis of methane hydrate formation in water and imidazolium based ionic liquid solutions. J. Chem. Thermodyn. 2018, 117, 147−154.

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