Hydrate Antiagglomeration Performance for the Active Components

Subscriber access provided by UNIVERSITY OF LEEDS

Article

The Hydrate Anti-agglomeration Performance for the Active Components Extracted from a Terrestrial Plant Fruit Xiao-Qin Wang, Hui-Bo Qin, Qing-Lan Ma, Zhen-Feng Sun, Ke-Le Yan, Zhi-Yu Song, Kai Guo, Dameng Liu, Guangjin Chen, and Changyu Sun Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02305 • Publication Date (Web): 02 Dec 2016 Downloaded from http://pubs.acs.org on December 15, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The Hydrate Anti-agglomeration Performance for the Active Components Extracted from a Terrestrial Plant Fruit Xiao-Qin Wanga,b,c, Hui-Bo Qinb, Qing-Lan Mab, Zhen-Feng Sunb, Ke-Le Yanb, Zhi-Yu Songb, Kai Guob, Da-Meng Liua, Guang-Jin Chenb , Chang-Yu Sunb,∗ a. School of Energy Resources, China University of Geosciences, Beijing, 100083, P. R. China b. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China c. College of Science, China University of Petroleum, Beijing, 102249, P. R. China

ABSTRACT: A terrestrial plant fruit extract was adopted to prevent hydrate accumulation. Four groups with different polarities, water-soluble, n-butanol-soluble, ethyl acetate-soluble and petroleum ether-soluble portion, were obtained by prefractionation of the plant-extract hydrate anti-agglomerant. The hydrate anti-agglomeration effect was tested in a high pressure transparent sapphire cell, and the active components were found mainly in the ethyl acetate-soluble portion that accounts for approximately 4.0 % of the whole plant extract. Through further separation and purification, the five kinds of components obtained proved experimentally to have the effect of preventing hydrate agglomeration. Their molecules and structural formulae were inferred by the high resolution mass spectrum and nuclear magnetic resonance analysis. Compared with the spectrum library, the components were determined to be eriodictyol, apigenin, naringenin, luteolin, and 5-(4-hydroxy-6, 7-dimethoxy-3-methylchroman-2-yl) benzene-1,2,3-triol. The tests on the extracted components and the commercial products verified their effect of preventing hydrate agglomeration, where apigenin and luteolin performed better than others. KEYWORD: plant extracts; hydrate; anti-agglomerant; flavonoids

∗

To whom correspondence should be addressed. Fax: +86 10 89733156. E-mail: [email protected] (C. Y. Sun). 1

ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. INTRODUCTION Gas hydrates are clathrates in which water molecules form a hydrogen-bonded network enclosing roughly spherical cavities that are filled with gas molecules such as methane, ethane, carbon dioxide.1 Most of oil and gas industries are being bored by hydrate forming in the transportation pipelines under elevated pressures and low temperatures.2 Plugs caused by gas hydrate formation are a menace to the oil and gas industry in production lines, during drilling (especially in deep water), and in work-over operations.3 Thermodynamic inhibitors (THIs), such as methanol and monoethylene glycol, have been used to prevent hydrate formation for over half a century.4-6 However, nowadays there are more and more blended transportation in deep seas; such inhibitors are required at or near a peak which will bring about new problems: high cost and environmental issues.7,8 Therefore more effective low dosage hydrate inhibitors (LDHIs) including kinetic hydrate inhibitors (KHIs) and anti-agglomerants (AAs) have been widely concerned.9,10 KHIs are commonly water-soluble polymers which would not change the hydrate thermodynamic equilibrium condition. AAs usually belong to surfactant which can be used in the oil and water. They allow hydrates to form but prevent them from agglomerating and subsequently accumulating into large masses. A high-performance AA enables hydrates to form a kind of transportable non-sticky slurry where hydrate particles disperse in the liquid hydrocarbon phase.11 It has been reported that polyvinylpyrrolidone (PVP), poly (N-vinyl caprolactam) (PVCap) and poly (N-vinyl pyrrolidone/N-vinyl caprolactam/N,N-dimethyl aminoethyl methacrylate) (VC-713), as KHIs, have the better performance on hydrate inhibiting.12,13 The inhibition performance of 2


Page 2 of 37

Page 3 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Poly(N-alkylglycine)s,

N,N-Dimethylhydrazidoacrylamides,

Poly(2-alkyl-2-oxazoline)s

Poly(N-alkyl-N-vinylacetamide)s acted as KHIs were also examined.14-17 As for the synergic reagent, polyethylene oxide (PEO) could not only greatly enhance the effect of inhibiting hydrate for PVCap, but also eliminate the memory effect.18,19 In addition, some ionic liquids20-23 have been reported as KHIs. Additionally, KHIs are often used in conjunction with synergists that can significantly enhance the kinetic inhibition performance of KHIs.10,24 For anti-agglomerants, the French Petroleum Institute（IFP）has developed a series of AAs.25-27 Shell reasoned that quaternary ammonium surfactants would be ideal candidates as hydrate AAs as they are known to be good particle dispersants and have better performance of anti-agglomeration at high subcooling.28,29 Kelland et al.30 found zwitterion surfactant could be used as AA such as 3-[N,N-dibutyl-N-(2-(3-carboxy-pentadecenoyloxy) propyl)] ammonio propanoate that could inhibit hydrate plug at 15.9 K of subcooling. So far, the maximum subcooling achieved by using the best AA, under which hydrate plug does not occur, is much higher than that by using KHIs, and AA is more suitable for the candidate for being applied in deep sea. 31 Since most KHIs and AAs are expensive, less bio-degradable and non-environment-friendly, some natural biomaterials were developed successively to prevent hydrate accumulation in the recent years, for example, antifreeze proteins (AFPs),32 cation starch33 and sorbitan fatty acid ester(Span) 11. Peng et al.34 indicated that Span 20 alone may fail to disperse hydrate particles in some cases, but it was found that a better performance for preventing hydrate plug was attained for the mixture of Span 20 and esters polymer (named as combined anti-agglomerant, CAA) at different ratio even though the initial water cut was up to 30.0 vol%. York et al.35,36 found and 3


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

proved rhamnolipid biosurfactant (RH) as AA could prevent tetrahydrofuran (THF) and cyclo-pentane (CP) hydrate agglomeration. He believed that methanol could be used as synergic reagent for RH. Sun and Firoozabadi37 found a new AA which could even be effective against hydrate agglomeration in pure water. However, there are fewer biosurfactants used as AAs, and the application of plant resources in hydrate inhibition has rarely been reported. Yan et al.38 in our laboratory evaluated a new plant-extract hydrate anti-agglomerant and indicated that the performance would be better for the new anti-agglomerant combined with Span 20. The new plant-extract hydrate AA is cheap and has broad prospects of application, but its active components are still unknown. In order to analyze the active components, the natural plant extract needs to be divided into several different segments or groups with different polarities using different solvents.39,40 The active components can be found by the further separation, and then with high performance liquid chromatography (HPLC), mass spectrometry (MS) and nuclear magnetic resonance (NMR), the structure of component can be identified.41 In this study, the plant-extract hydrate anti-agglomerant was separated and characterized, and its active components were determined. The result of this work is expected to be able to pave the way for synthesizing highly effective and environment friendly hydrate AAs.

2. EXPERIMENTAL APPARATUS AND PROCEDURES 2.1. Materials. All of the chemicals and reagents were analytically pure and commercially available. Methanol, ethanol, formic acid, petroleum ether, n-butyl alcohol, ethyl acetate, acetonitrile, and cyclohexane were all purchased from Aladdin Industrial (United States) 4


Page 4 of 37

Page 5 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Corporation whose Asian headquarters and warehouses are located in Shanghai, China. The double distilled deionized water and plant-extract hydrate anti-agglomerant were both made in our laboratory. The natural gas was used as hydrate forming gas in this work, whose composition was analyzed by gas chromatography HP 7890A and listed in Table 1. To obtain the water-in-oil emulsions containing anti-agglomerant, the diesel with a freezing point of 253.15 K was chosen as the hydrocarbon oil phase. The composition of the diesel was analyzed by the true boiling point (TBP) distillation system of crude oil and listed in Table 2. 2.2. Apparatus and Procedure for Testing Performance of AAs. The schematic diagram of the experimental apparatus used to evaluate the performance of hydrate anti-agglomerant is shown in Figure 1, which has been described particularly in our previous work.42,43 The main part of the apparatus is a cylindrical transparent sapphire cell of high pressure (up to 40 MPa) which is mounted in an air bath with a view window and a magnetic stirrer for accelerating the hydrate formation. The uncertainties of the temperature and pressure measurements are 0.1 K and 0.01 MPa, respectively. The air bath temperature is stabilized with a fluctuation within ± 0.1 K. Before the experiment, the transparent sapphire cell was rinsed twice with ethanol and then with petroleum ether to remove possible residual impurities. After that, it was dried by nitrogen purging to ensure that the cell was thoroughly cleaned. The desired quantity of prepared (diesel + water + anti-agglomerant) fluid was charged into the sapphire cell. Subsequently, the vapor space of the cell was vacuumed to ensure that the absence of air and the stirrer was turned on to ensure that the AA was dissolved in the oil and water system. At the same time, the temperature of air bath was adjusted to the desired value. 5


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

When the temperature in the cell maintained constant, the stirrer was turned off and the gas was injected into the sapphire cell until the desired pressure was achieved. Afterwards, the stirrer was turned on again at a constant speed. The pressure was recorded and the morphology of the hydrate slurry in the cell was observed by naked eyes. 2.3. Preparation and Preliminary Analysis of Plant-Extract Anti-Agglomerant. In this work, a hydrate anti-agglomerant was extracted from the fruit powder of a kind of terrestrial plant. During the process of extract, an appropriate amount of ethanol used as solvent, was added and the temperature maintained constant at a desired value for several hours. Afterwards, the product was filtered under reduced pressure and the filtrate was transferred to a rotary evaporator (RE-52AA) to remove redundant solvent. Lastly, the plant extract as hydrate anti-agglomerant was obtained. Usually, 370.2 g of hydrate anti-agglomerant can be extracted from 1.5 kg of fruit powder. The extraction ratio is approximately 25.0 %. As the content of active components in the plant-extract hydrate anti-agglomerant is very low, the approach of tracing active components was used for the further study.

3. RESULTS AND DISCUSSION 3.1. Separation of Plant Extract. The plant-extract hydrate AA was fractionated into four groups: 17.1 g petroleum ether-soluble portion, 13.0 g ethyl acetate-soluble portion, 197.8 g n-butyl alcohol-soluble portion, and 104.9 g water-soluble phase. 3.6 g of undissolved substance was further separated from the water-soluble phase, which might be the fruit powder entrained in the plant extract during the filtration. The remnant ethanol in the plant extract was the cause of material loss. The detailed process is shown in Figure 2. Therefore, the plant-extract hydrate AA 6


Page 6 of 37

Page 7 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

contains 4.6 % of petroleum ether-soluble portion, 3.5 % of ethyl acetate-soluble portion, 53.4 % of n-butyl alcohol-soluble portion, and 28.3 % of water-soluble phase. From the above results, it can be noticed that the n-butyl alcohol-soluble portion and water-soluble portion, which have stronger polarity, are the major fractions of the plant-extract hydrate AA, while the petroleum ether-soluble portion and ethyl acetate-soluble portion only occupy a small part. When we clean the bottle which was used to hold n-butanol portion, a large amount of foam was observed. As the saponins exist widely in terrestrial plants, and it is a very good biosurfactant, we think the foam was mainly caused by the remaining saponins in the residue of the bottle. Hence we have high expectation that the n-butanol-soluble portion contains the active components. For a further test of AA, the n-butyl alcohol-soluble portion was adsorbed and separated into several subfractions by sephadex column LH-20, one of which was total saponins, where methanol was used as the mobile phase. The petroleum ether-soluble portion and ethyl acetate-soluble portion were adsorbed and separated into a series of subfractions by 200-300 mesh silica gel, respectively, where the mixture of dichloromethane and methanol was used as the gradient eluent for the ethyl acetate-soluble portion and the mixture of petroleum ether and ethyl acetate for the petroleum ether-soluble portion. Afterwards, these subfractions, the water-soluble portion and the undissolved substance were tested for the performance of hydrate anti-agglomeration in the transparent sapphire cell. All the experiments were conducted in the system of 20.0 vol% water + 80.0 vol% diesel. The temperature was fixed at 274.15 K and the pressure ranged from 6.08 MPa to 6.97 MPa. The evaluations of anti-agglomeration effect for the 7


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

plant-extract hydrate AA and its different portions are shown in Table 3 and Figure 3 in detail, respectively. The dosages of AA were all based on water mass and the pressure was all admission pressure in this work. Figure 3(a-c) shows the anti-agglomeration effect of the plant-extract hydrate AA, with the different contents: 3.0 %, 2.0 %, and 1.0 %. The particles in the transparent sapphire cell are incompact and mushy. It manifests a good anti-agglomeration effect. Figure 3(d-l) shows the anti-agglomeration effect of the different portions of plant-extract hydrate AA. The results indicate that most of the subfractions in the n-butyl alcohol-soluble portion and petroleum ether-soluble portion are soluble in water. A series of (diesel + water + anti-agglomerant) fluids were prepared, and total saponins separated from the n-butyl alcohol-soluble portion were evaluated as AA, the dosages of which were 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, and 3.0 wt%, respectively. The evaluations showed that the n-butyl alcohol-soluble portion has poor anti-agglomeration performance. When the dosage of saponin was higher than 0.01 wt%, the prepared liquid system mixed very well with AA but was too sticky to be stirred before injecting the gas. The water-soluble portion and un-dissolved substance were proved to have poor anti-agglomeration performance as well. This means that the active components of the plant-extract AA are not in the n-butyl alcohol-soluble portion, water-soluble portion and undissolved substance, as shown in Figure 3(j-l). Each subfraction in the ethyl acetate-soluble portion used as AA would adhere to the inside wall of beaker and inlet tube easily. As these subfractions were hardly dissolved in the hot water and diesel, a small amount of ethanol was added into the (diesel + water + anti-agglomerant) 8


Page 8 of 37

Page 9 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

system to ensure these subfractions to be dissolved. If the dosage of AA was higher than 1.5 wt%, the stirrer would adhere to the bottom of the transparent sapphire cell without stirring. Some test results on the ethyl acetate-soluble and petroleum ether-soluble portion are shown in Figure 3(d-i). After many experiments, the active components of plant-extract AA were found mainly in the ethyl acetate-soluble portion and the end fraction of petroleum ether-soluble portion. Different subfractions had different effects of anti-agglomeration. Some subfractions added in the (diesel + water) system would make the hydrate slurry fine and smooth, such as subfraction 10*# in the petroleum ether-soluble portion (with ethanol solution) and subfractions 4-2# in the ethyl acetate-soluble portion [as shown in Figure 3(d and g)]. Some subfractions would make hydrate particles coarse, such as subfractions 10# in the petroleum ether-soluble portion (without ethanol solution) and 4-5# in the ethyl acetate-soluble portion [(as shown in Figure 3(e and h)]. The performance of these subfractions might be affected by ethanol. Compared with 10# in the petroleum ether-soluble portion (without ethanol) as shown in Figure 3, the hydrate slurry formed from 10*# in the petroleum ether-soluble portion (with 0.12g ethanol) is fine and the hydrate particles are smaller. It indicates that ethanol can be added as a synergist to enhance the anti-agglomeration effect on the subfractions 10# in the petroleum ether-soluble portion. Some subfractions would hardly prevent the hydrates from gathering some big particles, such as subfractions 12# in the ethyl acetate-soluble portion [(as shown in Figure 3(i)], the final hydrate is in the form of sludge. Some subfractions would put the system into a transition state where the hydrates were muddy before the stable hydrate slurry formed, such as subfractions 8# and 9# in the ethyl acetate-soluble portion. 9


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 37

The pressure-time profiles of hydrate forming process for some subfractions of the plant extract are shown in Figure 4. We can find that there are two pressure descending processes in each curve. The first is the dissolution process of the natural gas in the oil-water solution, and the second is the hydrate formation process. For some groups of curves, there exist significant induction time between the dissolution process and the hydrate formation process. For example, the induction time of hydrate formation of 10*# was greatly extended compared with 10#. 3.2. Determination of Active Components in Plant Extract. Because the same material may exist in the different portions during the extraction of hydrate anti-agglomerant from natural plants, the ethyl acetate-soluble portion was chosen first to separate the effective components. The ethyl acetate-soluble portion was separated by silica gel column, C18 column and HPLC step by step with gradient elution program, the composition of mobile phase was cyclohexane and ethyl acetate, methanol and 0.1 % formic acid aqueous solution，acetonitrile and 0.1 % formic acid aqueous solution, respectively. Then five components were obtained and the HPLC detection results are demonstrated in Figure 5. Their purity is both higher than 95.0 %, and the structural identification could be made. HPLC whose detecting conditions were set as follows: the temperature of chromatographic column (Phenomenex-C18, 250 × 4.6 mm), was kept constant at 308.15 K; the flow rate was 1.0 mL min-1. 3.3. Structural Analysis of Components. The components were detected by high resolution mass spectrum (HRMS, Bruker) and nuclear magnetic resonance (NMR, Bruker 500 MHz) technique. Taking component 1 for example, from HRMS detection it was determined to have a 10


Page 11 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

molecular formula of C15H12O6. 5.0 mg of freeze-dried component 1 was dissolved in hexadeuterio-dimethyl-sulfoxide (DMSO-D6) and then fed into NMR instrument. The 1H NMR spectrograms of component 1 are displayed in Figure 6(a, b and c), and the 13C NMR spectrograms of component 1 are displayed in Figure 6(d, e and f). The analysis of 1H NMR spectrum (DMSO-D6, 500MHz) indicated that component 1 contained 7 signals: proton signal of phenolic hydroxyl group on 5C at δ 12.152 (1H, s), proton signals of aromatic hydrocarbon on 2'C and 6'C at δ 6.876 (1H, s) and 6.742 (1H, s), respectively, hydrogen signal on 6C and 8C at δ 5.870 (2H, d), and hydrogen signals on 2C and 3C at δ 5.382, 5.377, 5.357, 5.353(1H, s) and 3.208, 3.183, 3.170, 3.149(1H, s), respectively. DMSO-D6 signal group appeared at δ 2.687, 2.682, 2.653, 2.648, and 2.500 (others are similar). The signal of 5C-OH appeared in low fields for association and the other 3 signals of active hydrogen hydroxyl group did not appear. The analysis of

13

C NMR spectrum (DMSO-D6) indicated that component 1 contained 14

signals: carbon signal of carbonyl group at δ 196.21 (C-4), hydroxyl carbon signals at δ 166.87 (C-7), 163.45 (C-5), 145.68 (C-4′) and 145.16 (C-3′), quaternary carbon signals at δ 162.84 (C-9), 129.42 (C-1′) and 101.66 (C-10), tertiary carbon signals at δ 117.89 (C-6′), 115.30 (C-5′), 114.30 (C-2′), 95.77 (C-6) and 94.97 (C-8), and secondary carbon signals at δ 42.03 (C-3). DMSO-D6 signal group appeared at δ 42.03, 39.93, 39.76, 39.59, 39.26, 39.09, and 38.93 (others are similar). From the HRMS and NMR detection mentioned above, the structural formula of component 11


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 37

1 can be deduced as displayed in Figure 7(a). Compared with the spectrum library, component 1 was determined to be eriodictyol ((S)- 3',4', 5,7-Tetrahydroxyflavanone). The molecular formula of component 2, component 3, component 4, and component 5 are C15H10O6、C15H10O5, C18H20O7 and C15H10O6, respectively. From HRMS and NMR detection, the structural formula of component 2, 3, 4 and 5 can be deduced as displayed in Figure 7(b) -apigenin(5,7-Dihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one), Figure 7(c)-naringenin (4',5,7-Trihydroxyflavanone), Figure 7(d)- unkown component at present (5-(4-hydroxy-6,7 -dimethoxy-3-methylchroman-2-yl)benzene-1,2,3-triol)

and

Figure

7(e)-luteolin

(2-(3,4-

Dihydroxyphenyl)-5,7-dihydroxy- 4H-chromen-4-one). 3.4. Evaluations on Hydrate Anti-Agglomeration Effect of the Components. Five components separated from the plant extract were investigated for the hydrate anti-agglomerate effect in a (natural gas + diesel + water) system where the initial water cut was 20.0 vol% and the temperature was set at 274.15 K. Accordingly, the effect of hydrate anti-agglomeration for pure eriodictyol, apigenin, naringenin and luteolin which were commercial products (HPLC≥98.0%) were also evaluated under the same conditions. Several pictures taken during the evaluation are shown in Figure 8 and the results are listed in Table 4 where the dosages of AA were all based on water mass. The subcooling in the experiments was more than 10 K. Compared with components extracted in this work with the corresponding pure commercial products, the experimental results indicated that all the samples have hydrate anti-agglomeration effect, and they behaved similarly in hydrate anti-agglomerating. Under the condition of AA content ≤ 2.0%, The more the AA was added, the more homogeneous the hydrate slurry was. 12


Page 13 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

In addition, from the experimental evaluation of hydrate anti-agglomeration effect (as shown in Figure 3 and Figure 8), it can come to a conclusion that the plant-extract AA and the ethyl acetate-soluble portion are much better than the single component. It means that both the plant-extract AA and the ethyl acetate-soluble portion can be viewed as combined AAs which are compounded with different kinds of AAs, and due to the natural cooperative effect of the active components for preventing hydrate agglomeration, the plant-extract AA is hard to be replaced by its single active composition or synthetics. As for the mechanism of hydrate anti-agglomeration for AAs, most researchers suggested that the capillary liquid bridge force might be the main reason for the hydrate agglomeration.44-46 From the structures of monomers as shown in Figure 7, it might be the molecules of these materials which would adhere to the hydrate crystals due to the hydrogen bond and hydroxyl to limit the crystals size. In addition, the oleophilic phenyl group would change the surface wettability of hydrate crystal. Therefore, hydrate crystals could disperse in the oil without agglomeration, which made it possible to transport crude oil in the form of hydrate slurry. According to the experimental evaluation results (as shown in Figure 8), the anti-agglomeration effect was better for luteolin and apigenin than others. Furthermore, eriodictyol, luteolin, apigenin and naringenin almost have the same configuration, except that luteolin and apigenin have a C-C double bond, and luteolin has one more hydroxyl than apigenin. According to their effect of anti-agglomeration, the double bond of luteolin and apigenin would play an important role in preventing hydrate agglomeration. The reasons for that might be that the π bond of C-C double bond could be adsorbed more stably on 13


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 37

the surface of diesel and could reduce the hydrophilicity of hydrate particle. Luteolin has more terminal hydrophilic group than the other components, hydroxyls could affix to the surface or stretch into the cavities of hydrate, which would destroy the regular configurations of hydrate crystals and prevent the hydrate particles from growing up. The mixed substances extracted and commercial products (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin) were also investigated for the hydrate anti-agglomerate effect in the (natural gas + diesel + water) system where the initial water cut was 20.0 vol% and the temperature was set at 274.15 K. The dosages of AA were all set at 0.4 % based on water mass. The evaluation results are list in Table 5 and the morphologies of the hydrate slurry formed are shown in Figure 9. It can be found that the mixture of extracted components [AA1 as shown in Figure 9(a)] and the mixture of commercial products [AA2 as shown in Figure 9(b)] produce the similar anti-agglomeration effect. The hydrate particles are relatively coarse and dispersed in the system with some adhere to the wall of sapphire cell, but both are superior to single component due to the synergistic effect.47-49 However, as shown in Figure 9(c), the hydrate anti-agglomeration effect of plant-extract AA is the best, in which the dispersion of hydrate particles is uniform and the hydrate particles are fine. This means other components which are not separated from the plant extract AA also play a role in the prevention of hydrate, and the four components separated are not all the active substances in the plant extract AA.

4. CONCLUSIONS The active components of the hydrate anti-agglomerant extracted from the fruit of a kind of 14


Page 15 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

terrestrial plant were investigated, which did not exist in the n-butanol-soluble portion (saponins) with high expectations, but were confirmed mainly in the ethyl acetate-soluble portion which account for approximately 4.0 % of the total initial plant extract. Five components were further separated from the ethyl acetate-soluble portion, and all of these belong to flavonoid. The 5-(4-hydroxy -6,7-dimethoxy-3-methylchroman-2-yl) benzene-1,2,3-triol was first discovered. Compared with the hydrate anti-agglomeration effects of these extracted components and commercial product, respectively, it proved that these components have some ability to prevent hydrates from agglomeration. Luteolin and apigenin performed better than other components but were inferior to that of the ethyl acetate-soluble portion and the plant-extract AA. The performance of mixed substances extracted and commercial products (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin) were also not as good as that of the plant-extract AA. It means that the synergy of the compounds in plant-extract AA is hard to be replaced by the effect of its single active composition or synthetics. The result of this work provides a helpful guidance on synthesizing highly effective and environment friendly hydrate AAs in the laboratory.

ACKNOWLEDGEMENTS Financial supports received from the National Natural Science Foundation of China (No. 51676207, 51576209, 21636009) are gratefully acknowledged.

REFERENCES (1) Strobel, T. A.; Koh, C. A.; Sloan, E. D. Hydrogen storage properties of clathrate hydrate materials. 11th International Conference on Properties and Phase Equilibria for Product and Process Design, Crete, Greece, July 261, 382–389, 2007. 15


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 37

(2) Sloan, E. D. Fundamental principles and applications of natural gas hydrates. Nature 2003, 426, 353–359. (3) Kelland, M. A.; Svartas, T. M.; Andersen, L. D. Gas hydrate anti-agglomerant properties of polypropoxylates and some other demulsifiers. J.Petrol. Sci. Eng. 2009, 64, 1–10. (4) Mohammadi, A. H.; Richon, D. Gas hydrate phase equilibrium in the presence of ethylene glycol or methanol aqueous solution. Ind. Eng. Chem. Res. 2010, 49, 8865-8869. (5) Sun, M. W.; Wang, Y.; Firoozabadi, A. Effectiveness of alcohol cosurfactants in hydrate antiagglomeration. Energy Fuels 2012, 26, 5626−5632 (6) Riaz, M.; Yussuf, M. A.; Frost, M.; Kontogeorgis, G. M.; Stenby, E. H.; Yan, W.; Solbraa, E. Distribution of gas hydrate inhibitor monoethylene glycol in condensate and water systems: experimental measurement and thermodynamic modeling using the Cubic-Plus-Association Equation of State. Energy Fuels 2014, 28, 3530–3538. (7) Kelland, M. A. History of the development of low dosage hydrate inhibitors. Energy Fuels 2006, 20, 825–847. (8) Wu, M.; Wang, S. M.; Liu, H. B. A study on inhibitors for the prevention of hydrate formation in gas transmission pipeline. J. Nat. Gas Chem. 2007, 16, 81–85. (9) Chen, J.; Wang, Y. F.; Sun, C. Y.; Li, F. G.; Ren, N.; Jia, M. L.; Yan, K. L.; Lv, Y. N.; Liu, B.; Chen, G. J. Evaluation of gas hydrate anti-agglomerant based on laser measurement. Energy Fuels 2015, 29, 122–129. (10) Perrin, A.; Musa, O. M.; Steed, J. W. The chemistry of low dosage clathrate hydrate inhibitors. Chem. Soc. Rev. 2013, 42, 1996–2015. (11) Huo, Z.; Freer, E.; Lamar, M.; Sannigrahi, B.; Knauss, D. M.; Sloan, E. D. Hydrate plug prevention by anti-agglomeration. Chem. Eng. Sci. 2001, 56, 4979–4991. (12) Lederhos, J. P.; Sloan, E.D. Transferability of kinetic inhibitors between laboratory and pilot plant. SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 6–9, 1996. (13) Ivall, J.; Pasieka, J.; Posteraro, D.; Servio, P. Profiling the concentration of the kinetic inhibitor polyvinylpyrrolidone throughout the methane hydrate formation process. Energy 16


Page 17 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Fuels 2015, 29, 2329–2335. (14) Villano, L. D.; Kommedal, R.; Fijten, M. W. M.; Schubert, U. S.; Hoogenboom, R.; Kelland, M. A. A study of the kinetic hydrate inhibitor performance and seawater biodegradability of a series of poly(2-alkyl-2-oxazoline)s. Energy Fuels 2009, 23, 3665–3673. (15) Ajiro, H.; Takemoto, Y.; Akashi, M.; Chua, P. C.; Kelland, M. A. Study of the kinetic hydrate inhibitor performance of a series of poly(N-alkyl-N-vinylacetamide)s. Energy Fuels 2010, 24, 6400–6410. (16) Reyes, F. T.; Guo, L.; Hedgepeth, J. W.; Zhang, D.; Kelland, M. A. first investigation of the kinetic hydrate inhibitor performance of poly(N-alkylglycine)s. Energy Fuels 2014, 28, 6889–6896. (17) Ree, L. H. S.; Mady, M. F.; Kelland, M. A. N,N-dimethylhydrazidoacrylamides. Part 3: Improving

kinetic

hydrate

inhibitor

performance

using

polymers

of

N,N-dimethylhydrazidomethacrylamide. Energy Fuels 2015, 29, 7923–7930. (18) Karaaslan, U.; Parlaktuna, M. PEO

A new hydrate inhibitor polymer. Energy Fuels 2002,

16, 1387–1391. (19) Lee, J. D.; Englezos, P. A. A powerful synergism to enhance kinetic inhibition. Proceeding of the 5th International Conference on Gas Hydrates, Trondheim, Norway, June 13–16, 2005. (20) Xiao, C. W.; Adidharma, H. Dual function inhibitors for methane hydrate. Chem. Eng. Sci. 2009, 64, 1522–1527. (21) Xiao, C. W.; Wibisono, N.; Adidharma, H. Dialkylimidazolium halide ionic liquids as dual function inhibitors for methane hydrate. Chem. Eng. Sci. 2010, 65, 3080–3087. (22) Long, Z.; Zhou, X. B.; Liang, D. Q.; Li, D. L. experimental study of methane hydrate equilibria in [EMIM]-NO3 aqueous solutions. J. Chem. Eng. Data 2015, 60, 2728–2732. (23) Tariq, M.; Atilhan, M.; Khraisheh, M.; Othman, E.; Castier, M.; García, G.; Aparicio, S.; Tohidi, B. Experimental and DFT approach on the determination of natural gas hydrate equilibrium with the use of excess N2 and choline chloride ionic liquid as an inhibitor. Energy Fuels 2016, 30, 2821–2832. (24) Qin, H. B.; Sun, C. Y.; Sun, Z. F.; Liu, B.; Chen, G. J. Relationship between the interfacial 17


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 37

tension and inhibition performance of hydrate inhibitors. Chem. Eng. Sci. 2016, 148, 182-189. (25) Sugier, A.; Bourgmayer, P.; Behar, E.; Freund, E. 1989. Patent EP0323307. (26) Sugier, A.; Bourgmayer, P.; Stern, R. 1989. Patent EP0323775. (27) Angel, M.; Neubecker, K.; Sanner, A. 2005. Patent US6867262. (28) Klomp, U. C.; Kruka, V. R.; Reijnhart, R.; Weisenborn, A. J. 1995. Patent WO017579. (29) Frostman, L. M. Anti-agglomerant hydrate inhibitors for prevention of hydrate plugs in deepwater systems. Proceedings of the SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, October 1–4, 2000. (30) Kelland, M. A.; Svartaas, T. M.; Ovsthus, J.; Tomita, T.; Chosa, J. Studies on some zwitterionic surfactant gas hydrate anti-agglomerants. Chem. Eng. Sci. 2006, 61, 4048–4059. (31) Kelland, M. A.; Svartaas, T. M.; Ovsthus, J.; Tomita, T.; Mizuta, K. Studies on some alkylamide surfactant gas hydrate anti-agglomerants. Chem. Eng. Sci. 2006, 61, 4290–4298. (32) Zeng, H.; Wilson, L. D.; Walker, V. K.; Ripmeester, J. A. Effect of antifreeze proteins on the nucleation, growth, and the memory effect during Tetranydrofuran clathrate hydrate formation. J. Am. Chem. Soc. 2006, 128, 2844–2850. (33) Lee, J. D.; Wu, H. J.; Englezos, P. Cationic starches as gas hydrate kinetic inhibitors. Chem. Eng. Sci. 2007, 62, 6548–6555. (34) Peng, B. Z.; Chen, J.; Sun, C. Y.; Dandekar, A.; Guo, S. H.; Liu, B.; Mu, L.; Yang, L. Y.; Li, W. Z.; Chen, G. J. Flow characteristics and morphology of hydrate slurry formed from (natural gas + diesel oil/condensate oil + water) system containing anti-agglomerant. Chem. Eng. Sci. 2012, 84, 333–344. (35) York, J. D.; Firoozabadi, A. Comparing effectiveness of rhamnolipid biosurfactant with a quaternary ammonium salt surfactant for hydrate anti-agglomeration. J. Phys. Chem. B. 2008, 112, 845–851. (36) York, J. D.; Firoozabadi, A. Effect of brine on hydrate anti-agglomeration. Energy Fuels 2009, 23, 2937–2946. (37) Sun, M. W.; Firoozabadi, A. New surfactant for hydrate anti-agglomeration in hydrocarbon 18


Page 19 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

flowlines and seabed oil capture. J. Colloid. Interface Sci. 2013, 402, 312–319. (38) Yan, K. L.; Sun, C. Y.; Chen, J.; Chen, L. T.; Shen, D. J.; Liu, B.; Jia, M. L.; Niu, M.; Lv, Y. N.; Li, N.; Song, Z. Y.; Niu, S. S.; Chen, G. J. Flow characteristics and rheological properties of natural gas hydrate slurry in the presence of anti-agglomerant in a flow loop apparatus. Chem. Eng. Sci. 2014, 106, 99–108. (39) Li H. Y.; Hao Z. B.; Wang X. l.; Huang L.; Li J. P. Antioxidant activities of extracts and fractions from Lysimachia foenum-graecum Hance. Bioresour. Technol. 2009, 100, 970–974. (40) Jayaprakasha G. K.; Girennavar B.; Patil B. S. Radical scavenging activities of Rio Red grapefruits and Sour orange fruit extracts in different in vitro model systems. Bioresour. Technol. 2008, 99, 4484–4494. (41) Boligon A.A.; Pereira R. P.; Feltrin A. C.; Machado M. M.; Janovik V.; Rocha J. B. T.; Athayde M. L. Antioxidant activities of flavonol derivatives from the leaves and stem bark of Scutia buxifolia Reiss. Bioresour. Technol. 2009, 100, 6592–6598. (42) Chen, L. T.; Sun, C. Y.; Chen, G. J.; Zuo, J. Y.; Ng, H. J. Assessment of hydrate kinetic inhibitors with visual observations. Fluid Phase Equilib. 2010, 298, 143–149. (43) Wang, X. L.; Sun, C. Y.; Yang, L. Y.; Ma, Q. L.; Tang, X. L.; Zhao, H. W.; Chen, G. J. Vapor-hydrate equilibria for the methane + hydrogen + tetrahydrofuran + water system. J. Chem. Eng. Data 2009, 54, 310–313. (44) Yang, S.; Kleehammer, D. M.; Huo, Z. X.; Sloan, E. D.; Miller, K. T. Temperature dependence of particle–particle adherence forces in ice and clathrate hydrates. J. Colloid Interf. Sci. 2004, 277, 335–341. (45) Anklam, M. R.; York, J. D.; Helmerich, L.; Firoozabadi, A. Effects of antiagglomerants on the interactions between hydrate particles. Am. Ins. Chem. Eng. 2008, 54, 565–574. (46) McCulfor, J.; Himes, P.; Anklam, M. R. The effects of capillary forces on the flow properties of glass particle suspensions in mineral oil. Am. Ins. Chem. Eng. 2011, 57, 2334–2340. (47) Daraboina, N.; Malmos, C.; Solms, N. V. Synergistic kinetic inhibition of natural gas hydrate formation. Fuel 2013, 108, 749–757. 19


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 37

(48) Cohen, J. M.; Wolf, P. F.; Young, W. D. Enhanced Hydrate Inhibitors: Powerful Synergism with Glycol Ethers. Energy Fuels 1998, 12, 216–218. (49) Liu, G.; Zhao, Y. N.; Sun, C. H.; Li, F.; Lu, G. Q.; Cheng, H. M. Synergistic effects of B/N doping on the visible-light photocatalytic activity of mesoporous TiO2. Angew. Chem. Int. Ed. 2008, 47, 4516 –4520.

20


Page 21 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 1. Composition of Original Natural Gas Used in Hydrate Evaluation Experiment Component

CO2

N2

CH4

C 2H 6

C 3H 8

i-C4H10

n-C4H10

i-C5H12

n-C5H12

Mol (%)

2.02

2.13

90.89

3.84

0.73

0.20

0.14

0.03

0.02

Table 2. Composition of Diesel Used in Hydrate Evaluation Experiment Component

mol%

C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C20 C24 C28(C28+)

0.87 0.76 3.58 3.68 5.87 7.69 9.48 10.24 11.31 10.03 9.53 8.67 11.36 6.77 0.17

Total

100

21


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 37

Table 3. Comparisons of Hydrate Anti-Agglomeration Effect for Plant-Extract AA, n-Butyl Alcohol-Soluble Portion, Petroleum Ether-Soluble Portion, Ethyl Acetate-Soluble Portion, Aqueous Phase and Undissolved Substance – the Crude Separations of Plant-Extract AA.

Portion

Subfraction No.

The plant-extract AA

AA dosage (wt%)

P (MPa)

3.0

6.12

2.0 1.0

6.22 6.72

N-butyl alcohol-soluble portion

1

0.01-3.0

6.80~6.97

2 3 4

0.5, 3.0 3.0 1.0

6.80~6.90 6.92 6.83

Petroleum ether-soluble portion

1 2 3 4 5 6 7 8 9

2.9 3.0 3.0 3.1 4.1 2.9 1.9 3.0 2.0

6.20 6.18 6.19 6.17 6.18 6.19 6.16 6.17 6.17

10* 10

2.9 2.8

6.19 6.19

11

3.0

6.18

12 End fraction

3.0 3.0

6.18 6.18

Anti-agglomeration performance Good (hydrate in the form of incompact fine particles) Good Good Viscous fluid hardly stirred before gas injection Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor Barely (Agglomeration at the bottom, big particles at the top) Good Barely (Agglomeration at the bottom, small particles at the top) Barely (Agglomeration at the bottom, big particles at the top) Poor Good

*: In this group for petroleum ether-soluble portion, 0.12 g of ethanol was added.

22


Page 23 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 3. (Continued).

Portion

Subfraction No.

AA dosage (wt%)

Ethyl acetate-soluble portion

1 2 3

0.5 0.9 1.0

6.61 6.08 6.14

Poor Poor Bigger particles, some effect

0.5 0.5 2.0 0.7 0.5 0.5

6.18 6.19 6.19 6.19 6.19 6.19

Good Good Moderate (Bigger particles) Moderate (Bigger particles) Moderate (Bigger particles) Good

0.9

6.09

Barely (Agglomeration at the bottom, small particles at the top)

6-1 6-2

0.5 0.3

6.17 6.18

6-3

0.7

6.18

6-4 6-5

0.6 0.7

6.18 6.18

6-6

0.4

6.19

Poor Barely (Agglomeration at the bottom, big particles at the top) Barely (Agglomeration at the bottom, small particles at the top) Good Barely (Agglomeration at the bottom, big particles at the top) Poor

7 8 9 10 11

1.2 1.0 0.7 0.7 0.8

6.19 6.60 6.53 6.61 6.69

12 13

1.0 0.6

6.67 6.70

14

1.0

6.61

A little effect fine particles, transition state fine particles, transition state A little effect Barely (Agglomeration at the bottom, big particles at the top) Poor Barely (Agglomeration at the bottom, big particles at the top) Poor

3.0 3.0

6.54 6.52

Poor Poor

4

4-1 4-2 4-3 4-4 4-5 4-6

5 6

Water-soluble portion Undissolved substance

P (MPa)

Anti-agglomeration effect

23


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 4. Evaluation Results for Substances as Hydrate AA AA dosage (wt%)

P (MPa)

Extracted

0.7

7.04

Bought

0.7

7.11

1.3

7.12

Extracted

0.3

7.22

Bought

0.3

7.02

1.8

7.06

Extracted

0.5

7.02

Bought

0.6

7.05

1.6

7.10

Extracted

0.6

7.22

Bought

0.6

7.09

1.0

7.01

AA Eriodictyol

Apigenin

Naringenin

Luteolin

The morphology of hydrate particles (a) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (b) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (c) Flocculent and incompact hydrate particles dispersed in the emulsion (d) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (e) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (f) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (g) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (h) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (i) Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion (j) Flocculent hydrate particles dispersed in the emulsion (k) Flocculent hydrate particles dispersed in the emulsion (l) Incompact hydrate particles dispersed in the emulsion

24


Page 24 of 37

Page 25 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 5. Evaluation Results for Mixed Substances Extracted and Commercial Product as Hydrate AA AA dosage (wt%)

P (MPa)

The morphology of hydrate particles

Eriodictyol, Apigenin, Naringenin and Luteolin(extracted), each accounting for 25 wt%

0.4

6.98

Eriodictyol, Apigenin, Naringenin and Luteolin(commercial product), each accounting for 25 wt%

0.4

7.03

0.4

7.19

Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion Some hydrates on the cell wall, incompact hydrate particles dispersed in the emulsion Good

AA

Composition

AA1

AA2

Plant-extract AA

25


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 37

Figure captions Figure 1. Schematic diagram of experimental apparatus for evaluating the performance of hydrate anti-agglomerant. DPT: differential pressure transducer; RTD: resistance thermocouple detector. Figure 2. Extraction schematic diagram of plant-extract hydrate anti-agglomerant. Figure 3. Morphologies of natural gas hydrate slurry formed in the high pressure sapphire cell with different plant-extract hydrate AA added. (a) 3.0 wt% of the plant-extract AA; (b) 2.0 wt% of the plant-extract AA; (c) 1.0 wt% of the plant-extract AA; (d) 10*# in the petroleum ether-soluble portion (with 0.12 g ethanol solution); (e) 10# in the petroleum ether-soluble portion (without ethanol solution) ; (f) The end fraction of the petroleum ether-soluble portion; (g) 4-2# in the ethyl acetate-soluble portion; (h) 4-5# in the ethyl acetate-soluble portion; (i) 12# in the ethyl acetate-soluble portion; (j) 1# in the n-butyl alcohol-soluble portion; (k) The water-soluble portion; (l) Undissolved substance. Figure 4. Pressure-time profiles of hydrate forming process for some subfractions of the Plant extract. Figure 5. HPLC spectrogram of components. (a) HPLC spectrogram of component 1; (b) HPLC spectrogram of component 2. (c) HPLC spectrogram of component 3; (d) HPLC spectrogram of component 4; (e) HPLC spectrogram of component 5. Figure 6. 1H and

13

C NMR spectrogram of component 1. (a), (b), (c) 1H NMR spectrogram; (d),

(e), (f) 13C NMR spectrogram. Figure 7. Structural formula of component 1 to 5. (a) Structural formula of component 1eriodictyol; (b) Structural formula of component 2- apigenin; (c) Structural formula of 26


Page 27 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

component 3- naringenin; (d) Structural formula of component 4- unkown component; (e) Structural formula of component 5- luteolin. Figure 8. Macroscopical morphology of hydrate slurry with four components as hydrate AA. (a) 0.7 wt% eriodictyol (Extracted); (b) 0.7 wt% eriodictyol (Bought); (c) 1.3 wt% eriodictyol (Bought); (d) 0.3 wt% apigenin (Extracted); (e) 0.3 wt% apigenin (Bought); (f) 1.8 wt% apigenin (Bought); (g) 0.6wt% naringenin (Extracted); (h) 0.6 wt% naringenin (Bought); (i) 1.6 wt% naringenin (Bought); (j) 0.6 wt% luteolin (Extracted); (k) 0.6 wt% luteolin (Bought); (l) 1.0 wt% luteolin (Bought). Figure 9. Macroscopical morphology of hydrate slurry with four components mixed as hydrate AA. (a) 0.4 wt% of extracted (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin); (b) 0.4 wt% of commercial (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin); (c) 0.4 wt% of plant-extract AA.

27


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 37

Figure 1. Schematic diagram of experimental apparatus for evaluating the performance of hydrate anti-agglomerant. DPT: differential pressure transducer; RTD: resistance thermocouple detector.

28


Page 29 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Plant-extract hydrate anti-agglomerant Dissolved in hot water

Petroleum ether-soluble portion

Petroleum ether extraction

Raffinate phase Ethyl acetate extraction

Raffinate phase

Ethyl acetate-soluble portion

n-butyl alcohol extraction

Remove ethyl acetate Flavonoids n-butyl alcohol-soluble portion

water-soluble phase with undissolved substance

Concentration Crude saponin Figure 2. Extraction schematic diagram of plant-extract hydrate anti-agglomerant.

29


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 37

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

Figure 3. Morphologies of natural gas hydrate slurry formed in the high pressure sapphire cell with 30


Page 31 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

different plant-extract hydrate AA added. (a) 3.0 wt% of the plant-extract AA; (b) 2.0 wt% of the plant-extract AA; (c) 1.0 wt% of the plant-extract AA; (d) 10*# in the petroleum ether-soluble portion (with 0.12 g ethanol solution); (e) 10# in the petroleum ether-soluble portion (without ethanol solution) ; (f) The end fraction of the petroleum ether-soluble portion; (g) 4-2# in the ethyl acetate-soluble portion; (h) 4-5# in the ethyl acetate-soluble portion; (i) 12# in the ethyl acetate-soluble portion; (j) 1# in the n-butyl alcohol-soluble portion; (k) The water-soluble portion; (l) Undissolved substance.

31


Energy & Fuels

6 .4

10# in the petr ole um ethe r-soluble por tion with ethanol

6 .2

10# in the petr ole um ethe r-soluble por tion without ethanol

6 .0

the end fra ction of the petr oleum e the r-soluble por tion

5 .8

P/MPa

5 .6

OT

5 .4

OT

OT

5 .2 5 .0 4 .8 4 .6 4 .4 -1 0

0

10

20

30

40

50

60

70

80

90

1 00

11 0

T/min (a)

6 .8

4- 2# in the ethyl ace tate-soluble portion 12# in the ethyl acetate -soluble por tion 4- 5# in the ethyl ace tate-soluble portion

6 .6 6 .4 6 .2 6 .0

P/MPa

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 37

OT

5 .8 5 .6

OT OT

5 .4 5 .2 5 .0 4 .8 4 .6 4 .4 -2 0

0

20

40

60

80

1 00

120

140

160

18 0

T/min (b)

Figure 4. Pressure-time profiles of hydrate forming process for some subfractions of the plant extract. (*OT: Onset Time of Hydrate Formation)

32


Page 33 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(a)

(b)

(c)

(d)

(e)

Figure 5. HPLC spectrogram of components. (a) HPLC spectrogram of component 1; (b) HPLC spectrogram of component 2. (c) HPLC spectrogram of component 3; (d) HPLC spectrogram of component 4; (e) HPLC spectrogram of component 5.

33


3.50 ppm (t1) 3.00

Figure 6. H and C NMR spectrogram of component 1. (a), (b), (c) H NMR spectrogram; (d), (e), (f) 1 2.50 2.00 1.50 1.00

13

13

C NMR spectrogram.

34

ACS Paragon Plus Environment 200 ppm (t1)

(c)

1 150

39.50

38.929

39.096

39.262

39.429

39.596 50

39.00

78.400

(b) 40.00

94.976

40.50

95.772

41.00

101.659

41.50 39.763

39.930

100

114.302

42.00

115.302

42.50 ppm (t1)

117.896

5.50 150

129.425

(a)

145.160

ppm (t1)

145.681

200

162.846

0.0

163.449

42.037

5.353

5.357

5.378

5.382

ppm (t1)

166.877

196.212

0.869

6.00

0.892

6.50

1.055

5.0

1.224

5.871

6.743

6.877

10.0

1.247

7.00

1.733

2.500

2.648

2.654

15.0

2.682

7.50

2.688

3.149

3.170

3.183

38.929

39.096

39.262

39.429

39.596

39.763

39.930

42.037

78.400

94.976

95.772

101.659

114.302

115.302

117.896

129.425

145.160

145.681

162.846

163.449

166.877

196.212

0.855

0.869

0.883

0.892

0.905

1.028

1.042

1.055

1.211

1.224

1.247

1.733

2.177

2.500

2.648

2.654

2.682

2.688

3.149

3.170

3.183

3.208

5.353

5.357

5.378

5.382

5.871

6.743

6.877

12.153

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3.208

Energy & Fuels Page 34 of 37

ppm (t1) 0

(d)

38.50

(e)

100

(f)

Page 35 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

OH 3′ 3′

OH

2′ 8

HO

7

6

8

HO

2

5′

2

9

6′

6′

10

6

3

3

4

5 4

5

OH

OH

O

O

(a)

(b) 3′

8

4′

1′

O

7

3′

8

O

6′

10

O

7

6

1′

5′

O

6′

5

OH

3

10

4

OH

4′

2

9

3

5

OH

2′

5′

2

9 6

OH

OH

2′

HO

1′

O

7

5′

9 10

4′

4′

1′

O

OH

2′

4

O OH

(c)

(d) OH 3′

OH

2′ 8

HO

1′

O

7

6′

10

3 4

5

OH

5′

2

9 6

4′

O

(e)

Figure 7. Structural formula of component 1 to 5. (a) Structural formula of component 1- eriodictyol; (b) Structural formula of component 2- apigenin; (c) Structural formula of component 3- naringenin; (d) Structural formula of component 4- unkown component; (e) Structural formula of component 5- luteolin.

35


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 37

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

Figure 8. Macroscopical morphology of hydrate slurry with four components as hydrate AA. (a) 0.7 wt% eriodictyol (Extracted); (b) 0.7 wt% eriodictyol (Bought); (c) 1.3 wt% eriodictyol (Bought); (d) 0.3 wt% apigenin (Extracted); (e) 0.3 wt% apigenin (Bought); (f) 1.8 wt% apigenin (Bought); (g) 0.5wt% naringenin (Extracted); (h) 0.6 wt% naringenin (Bought); (i) 1.6 wt% naringenin (Bought); (j) 0.6 wt% luteolin (Extracted); (k) 0.6 wt% luteolin (Bought); (l) 1.0 wt% luteolin (Bought). 36


Page 37 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(a)

(b)

(c)

Figure 9. Macroscopical morphology of hydrate slurry with four components mixed as hydrate AA. (a) 0.4 wt% of extracted (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin); (b) 0.4 wt% of commercial (25 wt% Eriodictyol + 25 wt% Apigenin + 25 wt% Naringenin + 25 wt% Luteolin); (c) 0.4 wt% of plant-extract AA.

37


Hydrate Antiagglomeration Performance for the Active Components

Recommend Documents