Hydrate generation inhibitor and preparation method thereof

Abstract

The invention relates to the field of gas hydrate inhibition, in particular to a hydrate generation inhibitor and a preparation method thereof.The hydrate generation inhibitor is composed of glycine and pectin, the pectin is dissolved in deionized water, then the glycine is added, and N, N-dimethyl formamide is added under the low-temperature ice bath condition; the method comprises the following steps: catalyzing and activating carboxyl-COOH in pectin by using N, N '-dicyclohexylcarbodiimide, subsequently heating at a high temperature to react with amino-NH2 in glycine to finally generate an amido bond-CONH-on a pectin branch chain, maintaining a solution in a neutral state in an experiment process, and then cooling, separating, purifying and drying to obtain glycine modified pectin. And dissolving the mixture in deionized water to prepare the water-based cleaning agent. By using the hydrate generation inhibitor, the generation amount of the hydrate can be reduced, the generation rate of the hydrate is reduced, the induction time of hydrate generation is prolonged, and the inhibition effect on the gas hydrate is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas hydrate formation inhibition and oil and gas pipeline anti-blocking, and particularly relates to a hydrate formation inhibitor and a preparation method thereof. Background Technique

[0002] During the exploitation and transportation of natural gas, when encountering high pressure and low temperature conditions, the gas (such as CH4, C2H6, etc.) transported in the pipeline will form a non-stoichiometric clathrate complex, namely hydrate, with water droplets in the gas phase. These hydrate particles will aggregate as the fluid in the pipeline flows, forming hydrate clusters, which will ultimately lead to the blockage of the pipeline interior, and then cause a sudden increase in local pressure, thus generating potential safety problems and directly affecting the exploitation efficiency of natural gas wells and the transportation efficiency of pipelines.

[0003] Currently, the commonly used measure for preventing and controlling hydrates in pipelines is to add hydrate inhibitors, and some traditional hydrate inhibitors still have some inevitable disadvantages, such as failure at high supercooling degrees, excessive dosage, high cost, poor recyclability, environmental pollution, etc. With the increasingly strict environmental regulations for deep-sea oil and gas exploitation, the green biodegradability of natural gas hydrate inhibitors has attracted more and more attention from researchers and has become a research hotspot for hydrate inhibitors. In addition, it also has better economy compared with other inhibitors. Different inhibitors have different inhibition effects and cost problems. For example, in CN201510310186.5, a green composite hydrate inhibitor and a preparation method thereof, the green composite hydrate inhibitor is composed of methylated pectic acid and amino acids, and the two types of single inhibitors are used in combination to achieve kinetic effects. Although it can provide a certain hydrate inhibition effect, it is difficult to further improve the inhibition effect. Therefore, it is urgent to develop a new type of green natural biodegradable inhibitor with high efficiency and economy. Summary of the Invention

[0004] Aiming at the problems in the background technique, the present invention proposes a hydrate formation inhibitor and a preparation method thereof, which use glycine and pectin to improve the hydrate inhibition effect. The present invention modifies the functional functional groups in the molecular structures of these natural kinetic hydrate inhibitor molecules such as glycine and pectin, affects the arrangement of water molecules, reduces the possibility of forming a stable hydrogen bond network between water molecules, thereby destroying the cage structure of hydrates, and preparing an improved hydrate kinetic inhibitor. It solves the problems of poor biodegradability, low inhibition effect, high cost, etc. of current hydrate inhibitors.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a hydrate formation inhibitor, and the structural formula of the modified pectin monomer is shown as follows:

[0007]

[0008] Among them, n:m represents that the mass ratio of pectin monomer to glycine monomer is 5-20.

[0009] The preparation method of the natural gas hydrate inhibitor glycine-modified pectin of the present invention uses low-esterified pectin as a raw material, introduces an activator in a neutral environment, and through a free radical polymerization reaction with a glycine solution, synthesizes glycine-modified pectin, which is dissolved in water to obtain a hydrate formation inhibitor.

[0010] Furthermore, dissolve the low-esterified pectin in deionized water, add glycine, add N,N'-dicyclohexylcarbodiimide (DCC) as a catalyst under a low-temperature ice bath condition, then carry out a high-temperature heating reaction, continuously measure the pH and titrate the phosphate buffer solution during the experiment to maintain the solution in a neutral state, and then carry out cooling, separation, purification and drying to obtain glycine-modified pectin.

[0011] The mass fraction of glycine-modified pectin in the hydrate formation inhibitor is 0.1%-0.3%, and the balance is deionized water.

[0012] Preferably, the methoxy group content of the low-esterified pectin is 5%-10%, and the galacturonic acid content is 80%-85%.

[0013] Preferably, the activator is N,N'-dicyclohexylcarbodiimide. This activator can activate the carboxyl group in pectin and effectively promote the amidation reaction between the carboxyl group in pectin and the amino group of glycine, thereby realizing the modification of pectin. Secondly, DCC can only play a role under neutral conditions, which helps to protect other functional groups of pectin from being damaged and maintain its structural and functional characteristics.

[0014] Preferably, the mass ratio of the galacturonic acid functional group monomer, glycine and N,N'-dicyclohexylcarbodiimide is (20-25):(1-5):(1-3). Preferably, the mass fraction of glycine in pectin is 5%-20%.

[0015] The present invention also provides a preparation method of a hydrate formation inhibitor, comprising the following steps:

[0016] (1) Weigh pectin and dissolve it in deionized water. The pectin content in the solution is 1%-10%. Stir magnetically until the pectin is completely dissolved, measure the pH of the solution and adjust the pH value of the solution to 7-8 with a phosphate buffer solution, and continue to stir until uniform.

[0017] (2) Add glycine accounting for 5%-20% of the mass of pectin to the pectin solution, stir until uniform, measure the pH of the solution and adjust the pH value of the solution to 7-8 with a phosphate buffer solution.

[0018] (3) Place the mixed solution in an ice bath and maintain it for 15 min. After the solution approaches the ice bath temperature (0 °C), add N,N'-dicyclohexylcarbodiimide as a catalyst and stir until homogeneous.

[0019] (4) Heat the mixed solution to 60 °C and maintain for 2 - 4 h. Measure and titrate the pH every 30 min to maintain it at 7 - 8.

[0020] (5) After heating, cool the solution to room temperature, titrate its pH, then separate the solid and liquid, wash the solid with deionized water to purify it, and finally dry it to a constant weight to obtain glycine-modified pectin. Dissolve it in deionized water to obtain a hydrate formation inhibitor.

[0021] Preferably, the stirring time in steps (1) to (3) is 15 - 20 min.

[0022] Preferably, a centrifuge is used for solid-liquid separation in step (5).

[0023] Preferably, during the reaction of adding the catalyst DCC to the solution of the present invention, the pH is frequently measured and phosphate buffer solution is added to maintain the neutral environment of the solution and prevent the hydrolysis of the amide groups in the pectin side chains in acidic or alkaline environments.

[0024] Preferably, the methoxy content in the pectin is 5% - 10%, and the galacturonic acid content is 80% - 85%. According to the proportion of methoxylated galacturonic acid units in the pectin molecule, it is classified as low-esterified pectin.

[0025] The present invention also provides an application of a hydrate formation inhibitor in inhibiting the formation of carbon dioxide hydrates. The application steps are as follows: Inject the hydrate formation inhibitor into the reaction kettle at a temperature of 274.65 - 287.85 K, inject carbon dioxide gas into the kettle until the pressure is 4 - 5 MPa, and start magnetic stirring for the reaction to finally obtain solid hydrates.

[0026] Preferably, the magnetic stirring rate is 600 r / min and the reaction time is 6 - 10 h.

[0027] Compared with the prior art, the technical advantages of the present invention are:

[0028] (1) Compared with some previous composite hydrate inhibitors of pectin and amino acids, the inhibitor of the present invention does not combine two single inhibitors to achieve combined kinetic and thermodynamic effects. Instead, under high-temperature neutral conditions, a catalyst is added to break and recombine the carboxyl groups in glycine and pectin to produce a new type of modified pectin, solving the problems that the single pectin inhibitor has poor water solubility and hydrophilicity and general inhibition effect. By modifying pectin with glycine, on the one hand, its water solubility and hydrophilicity are improved, and on the other hand, by introducing a matrix with stronger electronegativity, the arrangement of water molecules is affected, reducing the possibility of forming a stable hydrogen bond network between water molecules.

[0029] (2) During the process of inhibiting hydrate formation, the hydrate formation inhibitor adopted in the present invention has a small dosage and high biodegradability, reducing pollution to the ecological environment. Moreover, the hydrate formation inhibitor adopted in the present invention can significantly reduce the initial hydrate formation rate while reducing the amount of hydrate formation, effectively preventing pipeline blockage, reducing risks, and improving the efficiency of mining operations.

[0030] (3) The preparation method of the hydrate inhibitor provided by the present invention is relatively easy and has a low cost, showing prospects for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the predicted nuclear magnetic resonance hydrogen spectrum diagram of the structural formula of the hydrate inhibitor of the present invention.

[0032] Figure 2 It is the comparison between the nuclear magnetic resonance hydrogen spectrum diagram of the actually prepared hydrate inhibitor and the predicted nuclear magnetic resonance hydrogen spectrum diagram.

[0033] Figure 3 It is the temperature-pressure diagram of the hydrate formation experiment of the modified pectin in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0034] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the following further describes the present invention in detail in conjunction with specific embodiments: However, the embodiments of the present invention are not limited thereto.

[0035] The pectin used in the examples, CAS No.: 9000-69-5, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; glycine, CAS No.: 56-40-6; N,N'-dicyclohexylcarbodiimide, CAS No.: 538-75-0.

[0036] Example 1

[0037] This example provides a hydrate formation inhibitor, and the preparation process is as follows:

[0038] (1) Weigh 5 g of pectin and 0.5 g of glycine separately using an electronic balance. Dissolve the pectin in 100 ml of deionized water, stir for 20 min until completely dissolved, add phosphate buffer solution to make the pH value of the solution 7, and stir for 15 min until homogeneous to obtain a pectin solution.

[0039] (2) Add 0.5 g of glycine to the pectin solution, stir for 15 min until homogeneous, measure the pH of the solution and adjust the pH value of the solution to 7 using phosphate buffer solution.

[0040] (3) Place the mixed solution in an ice bath at 0 °C and maintain for 15 min. After the solution approaches the ice bath temperature, add 0.6 g of N,N'-dicyclohexylcarbodiimide catalyst and stir for 20 min.

[0041] (4) Heat the mixed solution to 60 °C and maintain for 3 h. Measure and titrate the pH every 30 min to maintain it at 7.

[0042] (5) After heating, cool the solution to room temperature, titrate its pH, then separate the solid and liquid, wash the solid with deionized water to purify it, and finally dry it to a constant weight to obtain glycine-modified pectin. Weigh 0.1403 g of glycine-modified pectin, dissolve it in 70 g of deionized water, and stir for 20 min until completely dissolved to obtain a hydrate formation inhibitor with a mass fraction of 0.20%.

[0043] Application experiment:

[0044] This application experiment is carried out in a reactor with a volume of 250 mL, and the gas selected by the laboratory is carbon dioxide. Before the experiment, wash the reactor with deionized water and ethanol reagent at least three times repeatedly, and then purge the reactor with gas to remove the excess gas in the reactor. And conduct a leak inspection operation with soapy water. If no bubbles appear, it proves that the airtightness is good. Then inject the prepared solution into the reactor. Subsequently, immerse the reactor in a low-temperature constant-temperature bath. After completion, turn on the data acquisition system and the low-temperature constant-temperature bath, and set to record the temperature and pressure change data every 2 s. When the temperature in the reactor reaches 289.15 K, inject CO2 gas to pressurize to 4.5 MPa, and then start magnetic stirring at a speed of 600 r / min. When the gas reaches dissolution equilibrium, the temperature in the reactor drops to the set temperature of 275.15 K at a rate of 0.15 K / min to form hydrates.

[0045] According to the analysis of the experimental results, the gas consumption rate of the modified pectin prepared in Example 1 is 0.0425 mmol / min in the first 10 minutes and 0.83 mmol / min in the first 20 minutes in the carbon dioxide hydrate formation kinetics experiment, and the induction time for carbon dioxide hydrate formation is 241 min.

[0046] Example 2

[0047] This embodiment provides a hydrate formation inhibitor, and the preparation process is as follows:

[0048] (1) Weigh 5 g of pectin and 0.25 g of glycine separately with an electronic balance. Dissolve the pectin in 100 ml of deionized water, stir for 20 min until completely dissolved, add phosphate buffer solution to make the pH value of the solution 7, and stir for 15 min until homogeneous.

[0049] (2) Add 0.25 g of glycine to the pectin solution, stir for 15 min until homogeneous, measure the pH of the solution and adjust the pH value of the solution to 7 with phosphate buffer solution.

[0050] (3) Put the mixed solution into an ice bath at 0 °C and maintain it for 15 min. After the solution approaches the ice bath temperature, add 0.6 g of N,N'-dicyclohexylcarbodiimide for catalysis and stir for 20 min.

[0051] (4) Heat the mixed solution to 60 °C and keep it for 3 h. Measure and titrate the pH every 30 min to maintain it at 7.

[0052] (5) After the heating is completed, cool the solution to room temperature, titrate its pH, then separate the solid and liquid, wash the solid with deionized water to purify it, and finally dry it to constant weight to obtain glycine-modified pectin. Weigh 0.1403 g of the modified pectin, dissolve it in 70 g of deionized water, and stir for 20 min until completely dissolved to obtain a hydrate formation inhibitor with a mass fraction of 0.20%.

[0053] Application experiment: The same as in Example 1.

[0054] According to the analysis of the experimental results, it can be obtained that the modified pectin prepared in Example 2 has a gas consumption rate of 0.161 mmol / min in the first 10 minutes and a gas consumption rate of 0.418 mmol / min in the first 20 minutes in the carbon dioxide hydrate formation kinetics experiment, and the induction time for the formation of carbon dioxide hydrate is 33 min.

[0055] Example 3

[0056] This embodiment provides a hydrate formation inhibitor, and the preparation process is as follows:

[0057] (1) Weigh 5 g of pectin and 1 g of glycine separately with an electronic balance. Dissolve the pectin in 100 ml of deionized water, stir for 20 min until completely dissolved, add phosphate buffer solution to make the pH value of the solution 7, and stir for 15 min until homogeneous.

[0058] (2) Add 1 g of glycine to the pectin solution, stir for 15 min until homogeneous, measure the pH of the solution and adjust the pH value of the solution to 7 with phosphate buffer solution.

[0059] (3) Place the mixed solution in an ice bath at 0 °C and maintain it for 15 min. After the solution approaches the ice bath temperature, add 0.6 g of N,N'-dicyclohexylcarbodiimide for catalysis and stir for 20 min.

[0060] (4) Heat the mixed solution to 60 °C and keep it for 3 h. Measure and titrate the pH every 30 min to maintain it at 7.

[0061] (5) After the heating is completed, cool the solution to room temperature, titrate its pH, then separate the solid from the liquid, wash the solid with deionized water to purify it, and finally dry it to a constant weight to obtain pectin modified with glycine. Weigh 0.1403 g of the modified pectin, dissolve it in 70 g of deionized water, and stir for 20 min until it is completely dissolved to obtain a hydrate formation inhibitor with a mass fraction of 0.20%.

[0062] Application experiment: The same as Example 1.

[0063] According to the analysis of the experimental results, it can be obtained that for the modified pectin prepared in Example 3 in the carbon dioxide hydrate formation kinetics experiment, the gas consumption rate in the first 10 minutes is 0.271 mmol / min, the gas consumption rate in the first 20 minutes is 0.574 mmol / min, and the induction time for carbon dioxide hydrate formation is 204 min.

[0064] Example 4

[0065] In this example, pectin with a mass fraction of 0.1% is used as the kinetic inhibitor. The source of the pectin raw material is the same as that in Example 1.

[0066] Weigh 0.0701 g of pectin respectively with an electronic balance. Add the pectin to 70 g of high-purity water and stir well to obtain a gas hydrate formation inhibitor with a mass fraction of 0.10%.

[0067] Application experiment: The same as Example 1.

[0068] According to the analysis of the experimental results, it can be obtained that for the 0.1% mass fraction of pectin prepared in Example 4 in the carbon dioxide hydrate formation kinetics experiment, the gas consumption rate in the first 10 minutes is 0.0655 mmol / min, the gas consumption rate in the first 20 minutes is 0.459 mmol / min, and the induction time for carbon dioxide hydrate formation is 24 min.

[0069] Example 5

[0070] In this example, pectin with a mass fraction of 0.2% is used as the kinetic inhibitor.

[0071] Weigh 0.1403 g of pectin separately using an electronic balance. Add the pectin to 70 g of high-purity water and stir well to obtain a gas hydrate formation inhibitor with a mass fraction of 0.20%.

[0072] Application experiment: The same as Example 1.

[0073] According to the analysis of the experimental results, the gas consumption rate of the 0.2% mass fraction of pectin prepared in Example 5 was 0.612 mmol / min in the first 10 minutes and 0.765 mmol / min in the first 20 minutes in the carbon dioxide hydrate formation kinetics experiment, and the induction time for carbon dioxide hydrate formation was 43 min.

[0074] Example 6

[0075] In this example, pectin with a mass fraction of 0.3% was used as the kinetic inhibitor.

[0076] Weigh 0.2106 g of pectin separately using an electronic balance. Add the pectin to 70 g of high-purity water and stir well to obtain a gas hydrate formation inhibitor.

[0077] Application experiment: The same as Example 1.

[0078] According to the analysis of the experimental results, the gas consumption rate of the 0.3% mass fraction of pectin prepared in Example 6 was 0.151 mmol / min in the first 10 minutes and 0.8 mmol / min in the first 20 minutes in the carbon dioxide hydrate formation kinetics experiment, and the induction time for carbon dioxide hydrate formation was 34 min.

[0079] Comparative Example 1

[0080] In this comparative example, no inhibitor was used for the hydrate kinetic formation experiment.

[0081] This application experiment was carried out in a 250 mL reaction kettle, and the gas selected in the laboratory was carbon dioxide. Before the experiment, the reaction kettle was repeatedly cleaned with deionized water and ethanol reagent at least three times, and then the reactor was purged with gas to remove the excess gas in the reaction kettle. And the airtightness was checked with soapy water. If no bubbles appeared, it proved that the airtightness was good. Then 70 g of pure aqueous solution was injected into the reaction kettle, and then the reaction kettle was immersed in a low-temperature constant-temperature bath. After completion, the data acquisition system and the low-temperature constant-temperature bath were turned on, and the temperature and pressure change data were recorded every 2 s. When the temperature in the kettle reached 289.15 K, CO2 gas was injected to pressurize to 4.5 MPa, and then the magnetic stirring was started at a speed of 600 r / min. When the gas reached the dissolution equilibrium, the temperature in the reaction kettle decreased to the set temperature of 275.15 K at a rate of 0.15 K / min to form hydrates.

[0082] According to the analysis of experimental results, the gas consumption rate of the modified pectin in the carbon dioxide hydrate formation kinetics experiment was 0.682 mmol / min in the first 10 minutes, 0.882 mmol / min in the first 20 minutes, and the induction time for the formation of carbon dioxide hydrate was 20 min.

[0083] Comparative Example 2

[0084] In this comparative example, glycine with a mass fraction of 0.5% was used as the kinetic hydrate inhibitor.

[0085] Weigh 0.3518 g of glycine and 70 g of deionized water separately with an electronic balance. Disperse glycine in deionized water and ultrasonically oscillate for 20 min to obtain the gas hydrate formation inhibitor.

[0086] Application experiment: The same as Example 1.

[0087] According to the analysis of experimental results, for glycine with a mass fraction of 0.5% in the carbon dioxide hydrate formation kinetics experiment, the gas consumption rate was 0.133 mmol / min in the first 10 minutes, 1.095 mmol / min in the first 20 minutes, and the induction time for the formation of carbon dioxide hydrate was 13 min.

[0088] Comparative Example 3

[0089] In this comparative example, a compound of low-esterified pectin with a mass fraction of 0.1% and glycine with a mass fraction of 0.5% was used as the kinetic hydrate inhibitor.

[0090] Weigh 0.0704 g of low-esterified pectin, 0.3521 g of glycine and 70 g of deionized water separately with an electronic balance. Disperse glycine in deionized water and ultrasonically oscillate for 20 min to obtain the gas hydrate formation inhibitor.

[0091] Application experiment: The same as Example 1.

[0092] According to the analysis of experimental results, for the compound of low-esterified pectin with a mass fraction of 0.1% and glycine with a mass fraction of 0.5% in the carbon dioxide hydrate formation kinetics experiment, the gas consumption rate was 0.057 mmol / min in the first 10 minutes, 0.834 mmol / min in the first 20 minutes, and the induction time for the formation of carbon dioxide hydrate was 10 min.

[0093] Comparative Example 4

[0094] In this comparative example, a compound of low-esterified pectin with a mass fraction of 0.2% and glycine with a mass fraction of 0.5% was used as the kinetic hydrate inhibitor.

[0095] Weigh 0.1410 g of low-esterified pectin, 0.3525 g of glycine, and 70 g of deionized water separately using an electronic balance. Disperse glycine in deionized water and perform ultrasonic dispersion for 20 min to obtain a gas hydrate formation inhibitor.

[0096] Application experiment: The same as Example 1.

[0097] According to the experimental results, it is analyzed that for the compound of 0.2% mass fraction of low-esterified pectin and 0.5% mass fraction of glycine, the gas consumption rate in the first 10 minutes of the carbon dioxide hydrate formation kinetics experiment is 0.256 mmol / min, the gas consumption rate in the first 20 minutes is 0.717 mmol / min, and the induction time for carbon dioxide hydrate formation is 16 min.

[0098] Comparative Example 5

[0099] In this comparative example, a compound of 0.3% mass fraction of low-esterified pectin and 0.5% mass fraction of glycine is used as a kinetic hydrate inhibitor.

[0100] Weigh 0.2117 g of low-esterified pectin, 0.3528 g of glycine, and 70 g of deionized water separately using an electronic balance. Disperse glycine in deionized water and perform ultrasonic dispersion for 20 min to obtain a gas hydrate formation inhibitor.

[0101] Application experiment: The same as Example 1.

[0102] According to the experimental results, it is analyzed that for the compound of 0.3% mass fraction of low-esterified pectin and 0.5% mass fraction of glycine, the gas consumption rate in the first 10 minutes of the carbon dioxide hydrate formation kinetics experiment is 0.460 mmol / min, the gas consumption rate in the first 20 minutes is 1.005 mmol / min, and the induction time for carbon dioxide hydrate formation is 27 min.

[0103] Comparative Example 6

[0104] In this comparative example, a compound of 0.2% mass fraction of low-esterified pectin and 0.1% mass fraction of glycine is used as a kinetic hydrate inhibitor.

[0105] Weigh 0.1404 g of low-esterified pectin, 0.0702 g of glycine, and 70 g of deionized water separately using an electronic balance. Disperse glycine in deionized water and perform ultrasonic dispersion for 20 min to obtain a gas hydrate formation inhibitor.

[0106] Application experiment: The same as Example 1.

[0107] According to the experimental results, in the kinetic experiment of carbon dioxide hydrate formation, the gas consumption rate of the compound of low-esterified pectin with a mass fraction of 0.2% and glycine with a mass fraction of 0.1% was 0.366 mmol / min in the first 10 minutes, 1.062 mmol / min in the first 20 minutes, and the induction time for carbon dioxide hydrate formation was 13 min.

[0108] Comparative Example 7

[0109] In this comparative example, the compound of low-esterified pectin with a mass fraction of 0.2% and glycine with a mass fraction of 1% was used as a kinetic hydrate inhibitor.

[0110] Weigh 0.1417 g of low-esterified pectin, 0.7085 g of glycine and 70 g of deionized water respectively with an electronic balance. Disperse glycine in deionized water and ultrasonically oscillate for 20 min to obtain a gas hydrate formation inhibitor.

[0111] Application experiment: the same as Example 1.

[0112] According to the experimental results, in the kinetic experiment of carbon dioxide hydrate formation, the gas consumption rate of the compound of low-esterified pectin with a mass fraction of 0.2% and glycine with a mass fraction of 1% was 0.167 mmol / min in the first 10 minutes, 0.220 mmol / min in the first 20 minutes, and the induction time for carbon dioxide hydrate formation was 7 min.

[0113] Table 1: The temperature, pressure, gas consumption rate in the first 10 min, gas consumption rate in the first 20 min and induction time of the hydrate inhibitors in each example in the hydrate kinetic experiment.

[0114]

[0115] Figure 1 It is the predicted nuclear magnetic resonance hydrogen spectrum of the pectin after modification of the hydrate inhibitor in Example 1. Figure 2 It is the comparison of the predicted nuclear magnetic resonance hydrogen spectra of pectin before and after modification. From Figure 1 and Figure 2It can be seen that under certain conditions, pectin and glycine react using N,N'-dicyclohexylcarbodiimide as a catalyst, and the characteristic peak of the modified pectin appears in the 1H NMR δ value range of 6.5 - 8.5 ppm. By comparing with the 1H NMR spectrum of pectin, it can be known that an amide bond is formed by the radical polymerization of the carboxyl group and amino group on the side chain of the pectin monomer molecule. As can be seen from Table 1, the induction time and gas consumption rate obtained by the hydrate kinetics experiment of the pectin modified with glycine are better than those of single pectin and glycine and their mixture, and are much better than the inhibition effect of the hydrate formation experiment under pure water conditions. The inhibition effect is the best when the modification ratio of pectin to glycine is 10:1, and the induction time is more than 10 times that of pure water. The modification with other ratios also has good inhibition ability, indicating that the effect of the modified pectin has been greatly improved.

[0116] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A hydrate formation inhibitor, characterized in that, Its monomer structural formula is shown as follows: Among them, n:m = 5 - 20, representing the mass ratio of pectin monomer to glycine monomer.

2. The preparation method of the hydrate inhibitor according to claim 1, characterized in that, Using low-esterified pectin as raw material, an activator is introduced in a neutral environment, and through free radical polymerization reaction with glycine solution, pectin modified by glycine is synthesized, dissolved in water to obtain a hydrate formation inhibitor.

3. The preparation method of the hydrate inhibitor according to claim 2, characterized in that, The methoxy content in the low-esterified pectin is 5% - 10%, and the galacturonic acid content is 80% - 85%.

4. The preparation method of the hydrate inhibitor according to claim 2, characterized in that, The activator is N,N'-dicyclohexylcarbodiimide.

5. The preparation method of the hydrate inhibitor according to claim 2, characterized in that, The mass ratio of the pectin, glycine, and N,N'-dicyclohexylcarbodiimide is (20 - 25):(1 - 5):(1 - 3).

6. The preparation method of the natural gas hydrate inhibitor according to claim 2, wherein It includes the following steps: (1) Weigh low-esterified pectin and dissolve it in deionized water. The pectin content in the solution is 1% - 10%. Stir magnetically until the pectin is completely dissolved. Measure the pH of the solution and adjust the pH value of the solution to the range of 7 - 8 with phosphate buffer solution. Continue stirring until it is uniform. (2) Add glycine accounting for 5% - 20% of the mass of pectin to the pectin solution, stir until it is uniform, measure the pH of the solution and adjust the pH value of the solution to the range of 7 - 8 with phosphate buffer solution. (3) Put the mixed solution obtained in step (2) into an ice bath environment. After the solution approaches the ice bath temperature, add the activator to catalyze the reaction and stir until it is uniform. (4) Heat the mixed solution obtained in step (3) to 55 - 65 °C, maintain the heating reaction for 2 - 4 h, measure and titrate the pH every 30 min to maintain it in the range of 7 - 8. (5) After the heating reaction ends, cool the solution to room temperature, titrate its pH, then let it stand to separate the solid and liquid, wash the solid with deionized water to purify it, and finally dry it to a constant weight to obtain pectin modified by glycine, dissolve it in deionized water to obtain a hydrate formation inhibitor.

7. The preparation method of the natural gas hydrate inhibitor according to claim 6, wherein The mass fraction of the pectin modified by glycine after being dissolved in deionized water in step (5) is 0.1% - 0.3%.

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