Water-based self-lubricating anti-natural gas hydrate coating

Abstract

The invention discloses a water-based self-lubricating anti-natural gas hydrate coating, which is prepared from the following raw materials in parts by weight: 0.5 to 2 parts of branched polyethyleneimine, 0.1 to 1.5 parts of 3, 4-dihydroxy phenyl propionic acid and 0.1 to 1 part of hyaluronic acid. Due to the existence of the water-based lubricating natural gas hydrate resistant coating, the problem that due to the fact that water drops permeate into surface textures of a super-hydrophobic coating, the mechanical interlocking adhesive force of hydrates and a surface structure is increased is solved. Reversible hydrogen bonds and electrostatic bonds can be generated through layer-by-layer self-assembly, and self-repairing of the coating when the coating is damaged is facilitated.

Description

Technical Field:

[0001] The present invention relates to the field of coating technology, and particularly to an aqueous self-lubricating anti-natural gas hydrate coating. Background Art:

[0002] Hydrates are compounds encapsulated by water molecules, formed by water molecules (H 2 O) and small molecules (CH 4 , CO 2 , cyclopentane, tetrahydrofuran, etc.). Natural gas hydrates are cage-like solid compounds formed by the mixing of water and natural gas under high pressure and low temperature (usually 310 MPa, 0 - 10 °C). Due to the large volume storage potential in the form of hydrates, at 273 K and 1 atm, 1 m3 of methane hydrate contains approximately 163 m 3 of methane. Existing investigations and studies have shown that the storage volume of natural gas hydrates is approximately twice the total amount of traditional fossil energy, and it has become an international consensus as a future alternative energy source. However, the existence of hydrates also poses great challenges to natural gas and oil production and transportation systems. Generally speaking, high pressure, low temperature, and the presence of water are three necessary conditions for hydrate formation, and these three conditions are easily met in subsea oil and gas pipelines. When water is present, natural gas hydrates will nucleate successively at the gas-liquid interface, accumulate and deposit in the pipeline, and eventually block the pipeline. Therefore, preventing the formation of hydrate blockages and safely removing hydrate blockages are very important for ensuring the transportation of deepwater oil and gas pipelines. Currently, the most important method for hydrate prevention and control is to add inhibitors, mainly including thermodynamic hydrate inhibitors (THI), kinetic hydrate inhibitors (KHI), and anti-aggregation agents (AA). However, the addition of inhibitors may lead to large fixed asset investments or environmental hazards. Especially now, new low-dose inhibitors are expensive and have problems such as being difficult to degrade. Therefore, designing a water hydrate-resistant surface coating to reduce hydrate blockages has been regarded as an alternative and effective method in recent years.

[0003] Currently, most reported anti-hydrate coatings utilize superhydrophobic surfaces to reduce the adhesion of hydrates to the pipe wall. For example, CN 103189594 B discloses coating at least a part of the inner surface of the pipeline with a non-metallic surface coating, and the non-metallic surface coating is selected from silicon coatings and coatings formed by applying cross-linked polymeric materials selected from siloxanes, fluorosiloxanes, and fluoropolymers. This surface combines the characteristics of surface micro / nano structures and low surface energy, can effectively block air between surface irregularities, and results in a reduction in the contact area between water and the solid surface, which is beneficial to quickly removing liquid water from the surface before it forms hydrates (ice nuclei) with guest molecules.

[0004] However, once the water droplets penetrate into the pores on the surface of the micro / nano-structured superhydrophobic coating and condense, the mechanical interlocking between the hydrate and the surface structure will lead to an increase in adhesion. Additionally, repeated freeze / thaw cycles may cause the performance of the micro / nano-structure to fail, weakening the anti-hydrate performance of the superhydrophobic coating. Therefore, a new type of coating that can solve the condensation occurring inside the surface texture and improve the cyclic use performance is needed. Summary of the Invention:

[0005] The object of the present invention is to provide an aqueous self-lubricating anti-natural gas hydrate coating, which solves the problem of condensation occurring inside the surface texture of the pipeline and also solves the problem of poor cyclic use performance of the existing superhydrophobic coatings.

[0006] The present invention is achieved through the following technical solutions:

[0007] An aqueous self-lubricating anti-natural gas hydrate coating, which is coated on the inner surface of the pipeline. The raw materials of the coating are: 0.5 - 2 parts by weight of branched polyethyleneimine (PEI), 0.1 - 1.5 parts by weight of 3,4-dihydroxyphenylpropionic acid, and 0.1 - 1 part by weight of hyaluronic acid (HA).

[0008] The material of the pipeline is stainless steel.

[0009] Specifically, 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) is added as a coupling reagent for branched polyethyleneimine (PEI) and 3,4-dihydroxyphenylpropionic acid to the raw materials of the coating.

[0010] Preferably, the coating thickness is 1.1 - 1.5 mm.

[0011] The preparation method of the coating is as follows: It is prepared by layer-by-layer (LbL) self-assembly of branched polyethyleneimine (PEI) crosslinked with 3,4-dihydroxyphenylpropionic acid and hyaluronic acid (HA). The specific steps are as follows: Dissolve branched polyethyleneimine (PEI) in phosphate buffered saline (PBS), adjust the pH value to 5.5 using 1.0 mol / L hydrochloric acid (HCl) solution, then add 3-(3,4-dihydroxyphenyl)propionic acid with a mass percentage of 0.5% and 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) with a mass percentage of 0.85% to the solution, and continuously stir at room temperature for 2 hours to obtain solution A. Dissolve hyaluronic acid in tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust the pH value to 7.0 using 1.0 mol / L sodium hydroxide (NaOH) solution to obtain solution B. Place the pipeline in solution A and solution B for alternate deposition to achieve layer-by-layer self-assembly. In the first deposition cycle, the stainless steel pipeline is soaked in solution A and solution B for 3 hours respectively. In the remaining deposition cycles, the pipeline is soaked in solution A and solution B for 3 minutes respectively.

[0012] The deposition cycle of layer-by-layer self-assembly is 10 to 20 times.

[0013] Hyaluronic acid (HA) is a high molecular polymer containing a large number of carboxyl and hydroxyl groups in its molecules. It forms intramolecular and intermolecular hydrogen bonds in aqueous solutions, which gives it a strong water retention ability and can bind more than 400 times its own weight of water. Polyethyleneimine (PEI) is a water-soluble high molecular polymer with hygroscopicity. Due to its polar group (amino group) and hydrophobic group (vinyl group) structures, it can combine with different substances.

[0014] The water-based self-lubricating anti-natural gas hydrate coating of the present invention is hydrophilic and has strong interactions with interfacial water molecules through hydrogen bonds or electrostatic attractions between two phases, which will disrupt the inherent water network, especially the water molecules lacking tetrahedral coordination in the outermost layer, resulting in the collapse of the interfacial water structure to form a pre-melted QLL layer (containing unfrozen water), thereby delaying the formation of hydrates and synergistically playing a lubricating role.

[0015] The present invention also protects the application of the water-based self-lubricating anti-natural gas hydrate coating, which is applied to the inner surface of pipelines, with an applicable pressure of 1 to 15 MPa and a temperature of -10 to 25 °C.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1) The coating raw materials of the present invention are convenient to obtain, safe and reliable, and simple to prepare. By immersing the substrate in the solution for deposition, the coating can be easily prepared and can be operated at room temperature without any chemical pretreatment of the substrate.

[0018] 2) The presence of the water-based lubricating anti-natural gas hydrate coating of the present invention avoids the problem that the superhydrophobic coating will increase the mechanical interlocking adhesion between the hydrate and the surface structure due to water droplets infiltrating into the surface texture. Layer-by-layer self-assembly will generate reversible hydrogen bonds and electrostatic bonds, which helps the coating to self-repair when damaged. Description of the drawings:

[0019] Figure 1 It is a schematic diagram of the layer-by-layer self-assembly and structure of polyethyleneimine (PEI) and hyaluronic acid (HA) Detailed implementation manners:

[0020] The following is a further description of the present invention, rather than a limitation of the present invention.

[0021] In the examples, branched polyethyleneimine (PEI) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a molecular weight Mw.ca = 70,000 and a 50% aqueous solution, and hyaluronic acid was purchased from Shanghai Macklin Biochemical Co., Ltd., with a molecular weight Mw.ca = 200,000 - 400,000.

[0022] Example 1:

[0023] An aqueous self-lubricating anti-natural gas hydrate coating, the raw materials of the coating are: 0.5 grams of branched polyethyleneimine (PEI), 0.1 grams of 3,4-dihydroxyphenylpropionic acid, and 0.5 grams of hyaluronic acid (HA).

[0024] The preparation method of the coating is as follows: Dissolve the branched polyethyleneimine (PEI) sample in phosphate buffered saline (PBS), adjust the pH value to 5.5 using 1.0 mol / L hydrochloric acid (HCl) solution, then add 0.5% by mass of 3-(3,4-dihydroxyphenyl)propionic acid and 0.85% by mass of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) to the solution, and continuously stir at room temperature for 2 hours to obtain solution A. Dissolve hyaluronic acid in tris(hydroxymethyl)aminomethane (Tris) buffer solution, and adjust the pH value to 7.0 using 1.0 mol / L sodium hydroxide (NaOH) solution to obtain solution B. Alternately deposit the stainless steel sheet in solution A and solution B to achieve layer-by-layer self-assembly. In the first deposition cycle, the stainless steel sheet is soaked in solution A and solution B for 3 hours respectively. In the remaining deposition cycles, the stainless steel sheet is soaked in solution A and solution B for 3 minutes respectively. The deposition cycle of layer-by-layer self-assembly is 10 times.

[0025] Comparative Example 1:

[0026] Referring to Example 1, the difference is that no coating is applied on the stainless steel surface.

[0027] Example 2:

[0028] Referring to Example 1, the difference is that the raw materials of the coating are: 0.8 grams of branched polyethyleneimine (PEI), 1 gram of 3,4-dihydroxyphenylpropionic acid, and 1.5 grams of hyaluronic acid (HA).

[0029] Example 3:

[0030] Referring to Example 1, the difference is that the raw materials of the coating are: 1.2 grams of branched polyethyleneimine (PEI), 0.8 grams of 3,4-dihydroxyphenylpropionic acid, and 0.5 grams of hyaluronic acid (HA), and the deposition cycle of layer-by-layer self-assembly is 15 times.

[0031] Example 4:

[0032] Referring to Example 1, the difference is that the raw materials of the coating are: 2 grams of branched polyethyleneimine (PEI), 0.3 grams of 3,4-dihydroxyphenylpropionic acid, and 0.1 grams of hyaluronic acid (HA), and the deposition cycle of layer-by-layer self-assembly is 20 times.

[0033] Example 5:

[0034] Referring to Example 1, the difference is that the raw materials of the coating are: 0.8 g of branched polyethyleneimine (PEI), 0.3 g of 3,4-dihydroxyphenylpropionic acid, and 0.1 g of hyaluronic acid (HA), and the deposition cycle of layer-by-layer self-assembly is 20 times.

[0035] Example 6:

[0036] Referring to Example 1, the difference is that the raw materials of the coating are: 1.2 g of branched polyethyleneimine (PEI), 0.5 g of 3,4-dihydroxyphenylpropionic acid, and 0.5 g of hyaluronic acid (HA), and the deposition cycle of layer-by-layer self-assembly is 15 times.

[0037] Example 7:

[0038] Referring to Example 1, the difference is that the raw materials of the coating are: 2 g of branched polyethyleneimine (PEI), 0.8 g of 3,4-dihydroxyphenylpropionic acid, and 1.5 g of hyaluronic acid (HA).

[0039] Control the temperature and examine the time when surface hydrates start to form on the stainless steel sheets coated with the anti-natural gas hydrate coating obtained in Examples 1-7 and the stainless steel sheet obtained in Comparative Example 1.

[0040] The natural gas hydrate formation gas uses a mixed gas. The composition of the first group of the mixed gas is: 92 vol% methane, 5 vol% ethane, and 3 vol% propane. The composition of the second group of the mixed gas is 0.208 vol% n-pentane, 0.201 vol% isopentane, 0.493 vol% isobutane, 0.789 vol% n-butane, 3.13 vol% propane, 7.51 vol% ethane, 0.398 vol% nitrogen, and 87.271 vol% methane.

[0041] The test device for the influence of coatings on hydrate formation uses a flow loop. The loop is 30 meters long, built of 316 stainless steel, with an inner pipe diameter of 2.54 cm. The loop contains a 30-cm long transparent section and a transparent window for observing the flow of hydrates at different positions inside the pipe. The temperature of the loop is cooled by a refrigeration unit through a jacket, and the temperature range of the refrigeration unit is -20 to 50 °C. The maximum design pressure is 15 MPa. There are 8 temperature sensors with an accuracy of 0.15 °C, 8 pressure sensors with an accuracy of 0.25% level, 2 differential pressure gauges with an accuracy of ±0.065% F.S, and 1 liquid flowmeter with an accuracy of ±0.065% F.S at different positions of the loop. All data such as temperature, pressure, differential pressure, and flow rate are collected and recorded by a computer. The liquid flow in the loop is achieved by a plunger pump. In this experiment, both gas and liquid do not flow, and it is carried out under static conditions. The stainless steel sheet coating is fixed at both ends on the fixed columns protruding in the stainless steel pipe and is suspended as a whole in the transparent section. The microscope observes the induction time of hydrate formation on the coating surface through the transparent section. The results are shown in Table 1 and Table 2.

[0042] Table 1 Surface test results of anti-natural gas hydrate under different experimental conditions for mixture gas 1

[0043]

[0044]

[0045] Table 2 Surface test results of anti-natural gas hydrate under different experimental conditions for mixture gas 2

[0046]

Claims

1. A water-based self-lubricating anti-natural gas hydrate coating, Characterized in that, This coating is applied to the inner surface of the pipeline, and the raw materials of the coating are: 0.5-2 parts by weight of branched polyethyleneimine, 0.1-1.5 parts by weight of 3,4-dihydroxyphenylpropionic acid, and 0.1-1 part by weight of hyaluronic acid.

2. The anti-natural gas hydrate coating according to claim 1, Characterized in that, 1-Ethyl-(3-dimethylaminopropyl)carbodiimide is also added to the raw materials of the coating as a coupling reagent for branched polyethyleneimine and 3,4-dihydroxyphenylpropionic acid.

3. The anti-natural gas hydrate coating according to claim 1, Characterized in that, The coating thickness is 1.1-1.5 mm.

4. The anti-natural gas hydrate coating according to claim 1, Characterized in that, The material of the pipeline is stainless steel.

5. The anti-natural gas hydrate coating according to claim 1, Characterized in that, The preparation method of the coating is as follows: It is prepared by layer-by-layer self-assembly of branched polyethyleneimine (PEI) crosslinked with 3,4-dihydroxyphenylpropionic acid and hyaluronic acid (HA).

6. The anti-natural gas hydrate coating according to claim 5, Characterized in that, The specific steps of the preparation method are as follows: Dissolve branched polyethyleneimine in phosphate buffered saline, adjust the pH value to 5.5 with hydrochloric acid, then add 3-(3,4-dihydroxyphenyl)propionic acid and 1-ethyl-(3-dimethylaminopropyl)carbodiimide with a mass percentage of 0.85% to the solution, and continuously stir at room temperature for 2 hours to obtain solution A; Dissolve hyaluronic acid in tris(hydroxymethyl)aminomethane buffer solution and adjust the pH value to 7.0 with sodium hydroxide solution to obtain solution B; Alternately deposit the pipeline in solution A and solution B to achieve layer-by-layer self-assembly. In the first deposition cycle, the pipeline is soaked in solution A and solution B for 3 hours respectively. In the remaining deposition cycles, the pipeline is soaked in solution A and solution B for 3 minutes respectively.

7. The anti-natural gas hydrate coating according to claim 6, Characterized in that, The deposition cycle of layer-by-layer self-assembly is 10-20 times.

8. The preparation method of the anti-natural gas hydrate coating according to claim 1 or 2, Characterized in that, The specific steps are as follows: Dissolve branched polyethyleneimine in phosphate buffered saline, adjust the pH value to 5.5 with hydrochloric acid, then add 3-(3,4-dihydroxyphenyl)propionic acid and 1-ethyl-(3-dimethylaminopropyl)carbodiimide with a mass percentage of 0.85% to the solution, and continuously stir at room temperature for 2 hours to obtain solution A; Dissolve hyaluronic acid in tris(hydroxymethyl)aminomethane buffer solution and adjust the pH value to 7.0 with sodium hydroxide solution to obtain solution B; Alternately deposit the pipeline in solution A and solution B to achieve layer-by-layer self-assembly. In the first deposition cycle, the pipeline is soaked in solution A and solution B for 3 hours respectively. In the remaining deposition cycles, the pipeline is soaked in solution A and solution B for 3 minutes respectively.

9. The preparation method of the anti-natural gas hydrate coating according to claim 8, Characterized in that, The concentration of hydrochloric acid is 1 mol / L, the concentration of sodium hydroxide solution is 1.0 mol / L, and the deposition cycle of layer-by-layer self-assembly is 10 - 20 times.

10. The application of the anti-gas hydrate coating according to claim 1, characterized in that: it is applied to the inner surface of oil and gas transmission pipelines, with an applicable pressure of 1 - 15 MPa and a temperature of -10°C to 25°C.

Images