A flotation agent, its preparation method and application in treating produced water from deepwater oil and gas fields

Abstract

This invention discloses a flotation agent, its preparation method, and its application in treating produced water from deepwater oil and gas fields, belonging to the field of wastewater treatment technology. The preparation method of this flotation agent includes the following steps: First, using polyether diamine and methyl acrylate as main raw materials, an addition reaction-transesterification reaction is iterated to obtain a branched intermediate product with eight ester groups on the periphery. Then, a transesterification reaction between the polyether monoamine and the intermediate product yields a branched polyether amide-amine, which serves as the flotation agent. The flotation agent of this invention exhibits excellent oil removal effects from deepwater oil and gas field produced water.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more particularly to deepwater oil and gas field produced water treatment technology. Specifically, it relates to a flotation agent, its preparation method, and its application in treating deepwater oil and gas field produced water. Background Technology

[0002] During the development of deepwater oil and gas fields, hydrates easily form inside the pipelines, causing blockages, reducing gas transmission volume, and affecting normal operation. Therefore, hydrate inhibitors are needed to prevent the formation of natural gas hydrates. Ethylene glycol is widely used as a hydrate inhibitor, and correspondingly, produced water also contains ethylene glycol. Typically, produced water from deepwater oil and gas fields undergoes a three-stage oil removal (condensate oil) process involving coalescence, flotation, and filtration before being discharged into the sea. This produced water treatment process mainly achieves oil-water separation through purely physical methods. When the ethylene glycol content in the produced water is low (less than 200 mg / L), this process can successfully treat the produced water to meet standards. However, when the ethylene glycol content in the produced water is high, ethylene glycol enhances the strength of the oil-water interface film, leading to increased stability of condensate oil droplets, and common cationic surfactants and cationic polymer flotation agents have poor oil removal effects. Summary of the Invention

[0003] To address the aforementioned problems, one objective of this invention is to provide a flotation agent. This invention uses polyether diamine and methyl acrylate as main raw materials, and obtains a branched intermediate product with eight ester groups on the periphery through an iterative addition reaction-transesterification reaction. Then, a branched polyether amide-amine is obtained as a flotation agent through a transesterification reaction between the polyether monoamine and the intermediate product. This flotation agent possesses a branched structure and amphiphilicity, contains polyoxyethylene structural units that strongly interact with ethylene glycol, and exhibits excellent flotation and oil removal performance.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a flotation agent includes the following steps: S1) Polyether diamine and methyl acrylate in a molar ratio of 1:4 are dissolved in methanol, and a 0.5-generation polyether amide-amine with 4 ester groups is obtained through an addition reaction; an equimolar amount of polyether diamine methanol solution is added, and a transesterification reaction is carried out to obtain a 1-generation polyether amide-amine with 4 primary amine groups; a methyl acrylate methanol solution with 2 times the molar amount of primary amine is added, and a 1.5-generation polyether amide-amine with 8 ester groups is obtained through an addition reaction. S2) Add a polyether monoamine methanol solution with an equimolar amount of ester group to the intermediate product obtained in S1, and obtain a branched polyether amide-amine with 8 external branches through an addition reaction, which can be used as a flotation agent.

[0005] In one embodiment of the present invention, in step S1, the polyether diamine is one of Huntsman's D-230, D-400, ED-600 and ED-900.

[0006] In one embodiment of the present invention, the mass concentration of the reactants in step S1 is in the range of 15%-25%.

[0007] In one embodiment of the present invention, the reaction temperature in step S1 is in the range of 20°C-40°C.

[0008] In one embodiment of the present invention, in step S2, the polyether monoamine is one of Huntsman's M600, M1000 and M2005.

[0009] In one embodiment of the present invention, in step S2, the mass concentration of the reactants is in the range of 15-25%.

[0010] In one embodiment of the present invention, the reaction temperature in step S2 is in the range of 40°C-60°C.

[0011] Another object of the present invention is to disclose a flotation agent prepared according to the above method.

[0012] Another object of the present invention is to disclose a method for applying the above-mentioned flotation agent to treat produced water from deep-water oil and gas fields containing ethylene glycol, which has good flotation oil removal performance for such produced water.

[0013] Compared with the prior art, the present invention has the following beneficial effects: Currently, there are no specific flotation agents for this purpose. Because produced water from deep-water oil and gas fields contains high concentrations of ethylene glycol, which enhances the strength of the oil-water interface film, leading to increased stability of condensate droplets, common cationic surfactants and cationic polymers have poor oil removal efficiency. The invented flotation agent contains polyoxyethylene structural units, which have a strong interaction with ethylene glycol, effectively acting on the oil-water interface, reducing the strength of the oil-water interface film, and possessing a branched structure that facilitates the aggregation and coalescence of multiple oil droplets. Furthermore, the flotation agent of this invention is amphiphilic, effectively reducing surface tension, adsorbing onto the surface of air bubbles, and promoting the adhesion between air bubbles and oil droplets. For produced water from a deep-water oil and gas field in the South China Sea (ethylene glycol concentration 2500 mg / L, condensate oil concentration 180 mg / L), the flotation agent of this invention can achieve an oil removal rate greater than 90% at 25 °C and a dosage of 10 mg / L. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the mechanism of the flotation agent preparation process of the present invention; Figure 2 This is the IR spectrum of the flotation agent in Example 1; Figure 3 These are physical images of the flotation evaluation results in Test Example 2, from left to right: blank group, Examples 1 to 10; Figure 4 The images show the flotation evaluation results from Test Example 3. From left to right, they are the blank group, FO4190, FO4290, and CTAB. Detailed Implementation

[0015] To illustrate the present invention more clearly, specific embodiments are described below. Those skilled in the art should understand that the following description is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0016] Example 1 A flotation agent, the preparation mechanism of which is as follows: Figure 1 As shown, it is prepared using the following method: S1) In a three-necked flask, 4.6 g (0.02 mol) of polyether diamine D-230 (molecular weight 230 g / mol) and 13.76 g (0.08 mol) of methyl acrylate were dissolved in 45.92 g of methanol and reacted at 25 °C for 24 h to obtain a 0.5-generation polyether amide-amine with 4 ester groups on the periphery; 18.4 g (0.08 mol) of D230 and 73.6 g of methanol were added to the three-necked flask and reacted at 25 °C for 24 h to obtain a 1-generation polyether amide-amine with 4 primary amine groups on the periphery; 13.76 g of methyl acrylate and 55.04 g of methanol were added to the three-necked flask and reacted at 25 °C for more than 24 h to obtain a 1.5-generation polyether amide-amine with 8 ester groups on the periphery.

[0017] S2) Add 96g of polyether monoamine M-600 to the intermediate product obtained in S1 and react at 45°C for 24h to obtain a branched polyether amide-amine with 8 external branches, which is used as a flotation agent.

[0018] Example 2 The basic implementation method of this embodiment is the same as that of Example 1, except that in S2, the polyether monoamine is M-1000, the amount added is 160g, and the methanol is 640g.

[0019] Example 3 The basic implementation method of this embodiment is the same as that of Example 1, except that the polyether monoamine in S2 is M-2005, the amount added is 320g, and the methanol is 1280g.

[0020] Example 4 The basic implementation method of this embodiment is the same as that of Example 1, except that the polyether diamine in S1 is D-400 (molecular weight of 430 g / mol). When synthesizing the 0.5 generation polyether amide-amine, the amount of D-400 added is 8.6 g and the amount of methanol added is 61.92 g; when synthesizing the 1 generation polyether amide-amine, the amount of D-400 added is 34.4 g and the amount of methanol added is 137.6 g.

[0021] Example 5 The basic implementation method of this embodiment is the same as that of embodiment 4, except that in S2, the polyether monoamine is M-1000, the amount added is 160g, and the methanol is 640g.

[0022] Example 6 The basic implementation method of this embodiment is the same as that of Example 4, except that the polyether monoamine in S2 is M-2005, the amount added is 320g, and the methanol is 1280g.

[0023] Example 7 The basic implementation method of this embodiment is the same as that of Example 1, except that the polyether diamine in S1 is ED-600 (molecular weight of 600 g / mol). When synthesizing 0.5 generation polyether amide-amine, the amount of ED-600 added is 12 g and the amount of methanol added is 75.52 g; when synthesizing 1 generation polyether amide-amine, the amount of ED-600 added is 48 g and the amount of methanol added is 192 g.

[0024] Example 8 The basic implementation method of this embodiment is the same as that of embodiment 7, except that in S2, the polyether monoamine is M-1000, the amount added is 160g, and the methanol is 640g.

[0025] Example 9 The basic implementation method of this embodiment is the same as that of Example 7, except that the polyether monoamine in S2 is M-2005, the amount added is 320g, and the methanol is 1280g.

[0026] Example 10 The basic implementation method of this embodiment is the same as that of Example 1. The difference is that the polyether diamine in S1 is ED-900 (molecular weight of 900 g / mol). When synthesizing the 0.5 generation polyether amide-amine, the amount of ED-600 added is 18 g and the amount of methanol added is 99.52 g; when synthesizing the 1 generation polyether amide-amine, the amount of ED-900 added is 72 g and the amount of methanol added is 288 g.

[0027] To further illustrate the technical effects of the present invention, the present invention also provides relevant tests of the above embodiments in practical applications.

[0028] Test Example 1: Infrared Spectrum of Flotation Agent in Example 1 The IR characterization results of the flotation agent are shown in Figure 2 In the image, 3482 cm -1 The absorption peak for -NH in the amide group is 2866 cm⁻¹. -1 The peak for the stretching vibration of -CH2 is 1641 cm⁻¹. -1 The vibrational peak of the amide carbonyl group is 1092 cm⁻¹. -1 It is the vibrational peak of the ether bond.

[0029] Test Example 2: Performance Evaluation Method of Flotation Agents 400 mL of produced water from a deep-water oil and gas field (ethylene glycol concentration 2500 mg / L, condensate oil concentration 180 mg / L) was added to a flotation column and a 10 mg / L flotation chamber. Flotation was performed for 30 s at 25 ℃ and an air flow rate of 1 L / min. The oil removal rate was calculated by measuring the oil content after flotation. The results are as follows: Figure 3 As shown in Table 1.

[0030] Table 1 shows the performance evaluation results of the flotation agents in different embodiments. The experimental results show that the oil removal rate of all 10 flotation agents is greater than 90%, which indicates that they have good flotation oil removal performance.

[0031] Table 1 Performance evaluation results of flotation agents in different embodiments Test Example 3: Performance Evaluation of the Comparative Example SNF's cationic polymers FO4190 and FO4290, and the small molecule cationic surfactant cetyltrimethylammonium bromide (CTAB) were used as comparative flotation agents. Their evaluation results are shown in Table 2 and... Figure 4 .

[0032] Table 2. Evaluation results of flotation performance of the comparative examples Test Example 4: Results of Determination of Elastic Modulus of Oil-Water Interface under the Action of Flotation Agent in Each Example Under conditions of 25℃ and a flotation agent dosage of 10 mg / L, the elastic modulus of the oil-water interface was determined using a DSA30 droplet morphology analyzer from KRÜSS GmbH, Germany. (The elastic modulus of the oil-water interface can quantitatively reflect the strength of the oil-water interfacial film; the larger the elastic modulus, the greater the interfacial film strength.) The results are shown in Table 3. Table 3 shows that the flotation agents in all 10 examples effectively reduced the elastic modulus of the oil-water interface.

[0033] Table 3 Performance evaluation results of flotation agents in different embodiments Test Example 5: Surface tension of flotation solvent solutions in different embodiments The surface tension of the flotation agent solution was measured using a DSA30 droplet morphology analyzer from KRÜSS GmbH (Germany) at 25°C and a flotation agent dosage of 10 mg / L. The results are shown in Table 4. Table 4 shows that the flotation agents in all 10 examples effectively reduced surface tension and exhibited good surface activity.

[0034] Table 4 Performance evaluation results of flotation agents in different embodiments The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a flotation agent, characterized in that, The synthesis steps are as follows: S1) Polyether diamine and methyl acrylate in a molar ratio of 1:4 are dissolved in methanol, and a 0.5-generation polyether amide-amine with 4 ester groups is obtained through an addition reaction; then, an equimolar amount of polyether diamine methanol solution is added, and a transesterification reaction is carried out to obtain a 1-generation polyether amide-amine with 4 primary amine groups; then, a methyl acrylate methanol solution with 2 times the molar amount of primary amine is added, and a 1.5-generation polyether amide-amine with 8 ester groups is obtained through an addition reaction. S2) Add a polyether monoamine methanol solution with an equimolar amount of ester group to the intermediate product obtained in S1, and obtain a branched polyether amide-amine with 8 external branches through an addition reaction, which can be used as a flotation agent.

2. The method for preparing a flotation agent according to claim 1, characterized in that: In step S1, the polyether diamine is one of Huntsman's D-230, D-400, ED-600 and ED-900.

3. The method for preparing a flotation agent according to claim 1, characterized in that: In step S1, the mass concentration of the reactants is 15%-25%.

4. The method for preparing a flotation agent according to claim 1, characterized in that: In step S1, the reaction temperature is 20℃-40℃.

5. The method for preparing a flotation agent according to claim 1, characterized in that: In step S2, the polyether monoamine is one of Huntsman's M600, M1000 and M2005.

6. The method for preparing a flotation agent according to claim 1, characterized in that: In step S2, the mass concentration of the reactants is 15%-25%.

7. The method for preparing a flotation agent according to claim 1, characterized in that: In step S2, the reaction temperature is 40℃-60℃.

8. A flotation agent, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

9. A method for applying a flotation agent in treating produced water from deepwater oil and gas fields, characterized in that: The flotation agent described in claim 8 is used to treat ethylene glycol-containing produced water.

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