Cationized polyethyleneimine modified nano carbon black demulsifier as well as preparation method and application thereof
The cationic polyethyleneimine demulsifier is prepared by modifying nano-carbon black, which solves the problem of poor water phase quality of existing carbon-based material demulsifiers, achieves efficient demulsification and wide applicability, and is suitable for stable oily wastewater treatment.
Patent Information
- Application Number
- CN202410321223.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-20
- Publication Date
- 2025-09-23
AI Technical Summary
The existing carbon-based material demulsifiers have poor water phase quality after demulsification, and traditional demulsifiers are toxic and non-biodegradable, making it difficult to effectively treat stable oily wastewater.
Nano-carbon black was used as the central core and modified by oxidation, grafting polyethyleneimine and grafting quaternary ammonium salt to prepare cationic polyethyleneimine modified nano-carbon black demulsifier, and the flocculation and aggregation ability were improved by π-π and electrostatic neutralization.
It achieves efficient demulsification, with the water phase transmittance reaching 95.7% after demulsification and the residual oil content as low as 15 mg/L. It is applicable to a wide range of pH values and salinity and is easy to operate.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of oilfield chemicals, and particularly relates to a cationic polyethyleneimine modified nano carbon black demulsifier, a preparation method and an application thereof. Background Art
[0002] The extraction of fossil fuels inevitably produces a large amount of produced water contaminated by emulsified oil droplets. The type of produced water is an oil-in-water emulsion, which may cause environmental pollution. In recent years, due to the increasing awareness of environmental protection, oil-water separation technology has attracted much attention. Commonly used demulsification methods include electrical demulsification, chemical demulsification, and biological demulsification. Among these methods, chemical demulsification is widely used in the petroleum industry due to its high cost-effectiveness. However, due to the presence of natural surfactants such as asphaltenes and resins, the emulsified oil droplets are very stable and difficult to separate effectively. Therefore, from a scientific and environmental perspective, the further development of new demulsifiers to treat oily wastewater remains a top priority.
[0003] Chemical demulsifiers are highly anticipated due to their amphiphilicity and ability to reduce interfacial film stability. However, with growing environmental awareness, traditional demulsifiers are being discouraged due to concerns about toxicity and non-biodegradability. In recent years, recycled magnetic demulsifiers, nanomaterials, carbon-based demulsifiers, and hyperbranched polymers have been used to treat oil-water emulsions. Carbon materials have recently been used to prepare demulsifiers due to their ability to displace asphaltenes through π-π and n-π interactions. However, existing carbon-based demulsifiers often suffer from poor aqueous phase quality after demulsification. Summary of the Invention
[0004] The main purpose of the present invention is to overcome the problems and shortcomings of the above-mentioned prior art and provide a cationic polyethyleneimine-modified nano-carbon black demulsifier and its preparation method and application. The cationic polyethyleneimine-modified nano-carbon black demulsifier can demulsify stable oily wastewater and has the characteristics of high efficiency, low dosage, short time and high quality of separated water phase; and the applicable pH value and salinity range of oily wastewater is wide, which is suitable for promotion and application.
[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:
[0006] A cationic polyethyleneimine-modified nano-carbon black demulsifier is obtained by sequentially oxidizing, grafting polyethyleneimine, and grafting quaternary ammonium salt on nano-carbon black.
[0007] In the above solution, the particle size of the nano carbon black is ≤100 nm.
[0008] In the above scheme, the oxidation step comprises: adding nano carbon black to a persulfate / sulfuric acid solution, reacting at 20-60° C. for 1-24 hours to obtain oxidized carbon black.
[0009] In the above scheme, the polyethyleneimine grafting step includes: adding oxidized carbon black and polyethyleneimine to a solvent, then adding a condensing agent and an activator, and reacting at 20-60° C. for 1-12 hours to obtain polyethyleneimine grafted modified nano carbon black.
[0010] In the above scheme, the condensing agent is one or more of dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and the like.
[0011] In the above scheme, the activator is one or more of 4-N, N-dimethylpyridine, 4-pyrrolidinopyridine, 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole, N-hydroxyphthalimide, etc.
[0012] In the above scheme, the step of grafting the quaternary ammonium salt comprises: adding the quaternary ammonium salt to the polyethyleneimine-modified nano-carbon black, heating the reaction, removing impurities and solvents, and obtaining the cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0013] In the above scheme, the quaternary ammonium salt is one or more of 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and (3-carboxypropyl)trimethylammonium chloride.
[0014] The preparation method of the above-mentioned cationic polyethyleneimine modified nano carbon black demulsifier comprises the following steps:
[0015] 1) Oxidation of nanocarbon black: Add nanocarbon black to a persulfate / sulfuric acid solution and react at 20-60° C. for 1-24 hours to obtain oxidized carbon black;
[0016] 2) Grafting polyethyleneimine: adding oxidized carbon black and polyethyleneimine to a solvent, then adding a condensing agent and an activator, and reacting at 20-60° C. for 1-12 hours to obtain polyethyleneimine-modified nanocarbon black;
[0017] 3) Grafting quaternary ammonium salt; adding the quaternary ammonium salt to the polyethyleneimine-modified nano-carbon black, heating the reaction, removing impurities and solvents, and obtaining a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0018] In the above scheme, in the persulfate / sulfuric acid solution, the concentration of persulfate is 0.5-2.5 mol / L; the concentration of sulfuric acid is 0.1-2 mol / L.
[0019] Preferably, the persulfate is one or more of ammonium persulfate, sodium persulfate, potassium persulfate, etc.
[0020] In the above solution, the molecular weight of the polyethyleneimine is 300-4500.
[0021] Preferably, the molecular weight of the polyethyleneimine is 300-2500.
[0022] In the above scheme, the solvent is one or more of dichloromethane, chloroform, tetrahydrofuran, dioxane, acetone, N,N-dimethylformamide, etc., and the solid-liquid ratio of the oxidized carbon black to the solvent is 1g: (10-50)mL.
[0023] In the above scheme, the mass ratio of the oxidized carbon black to the polyethyleneimine is 1:(2-5).
[0024] Preferably, the mass ratio of the condensing agent to the oxidized carbon black is (2-5):1; the mass ratio of the activator to the condensing agent is (0.01-1):1.
[0025] In the above scheme, the mass ratio of the quaternary ammonium salt to the polyethyleneimine-modified nano-carbon black is (1-2):1.
[0026] In the above scheme, the temperature of the heating reaction is 30-80°C and the time is 2-12 hours.
[0027] According to the above preparation method, a cationic polyethyleneimine modified nano-carbon black demulsifier is prepared. It uses nano-carbon black as the hydrophobic central core and branched polyethyleneimine as the hydrophilic end. Its positive charge is enhanced by quaternary ammonium salt modification, thereby improving the electrostatic neutralization ability and the flocculation and aggregation ability. At the same time, demulsification is achieved through the synergistic effect of π-π or n-π interaction and electrostatic neutralization.
[0028] Application of the above-mentioned cationic polyethyleneimine modified nano carbon black demulsifier in oily wastewater.
[0029] Furthermore, the concentration of the cationic polyethyleneimine modified nano-carbon black demulsifier in the oily wastewater is 25 to 100 mg / L.
[0030] Furthermore, the pH value of the oily wastewater is 3-11.
[0031] Preferably, the pH value of the oily wastewater is 3 to 9.
[0032] Furthermore, the salinity of the oily wastewater is 10,000 to 50,000 mg / L.
[0033] After demulsifying oily wastewater using the cationic polyethyleneimine modified nano-carbon black demulsifier described in the above scheme, the resulting water phase transmittance can be as high as 95.7%, and the residual oil content in the water phase can be as low as 15 mg / L.
[0034] The principles of the present invention include:
[0035] The present invention provides a cationic polyethyleneimine-modified nano-carbon black demulsifier. The surface of the nano-carbon black has a large delocalized π conjugated system that can interact with asphaltene to form n-π or π-π interactions. The characteristics of the nano-carbon black give it better dispersibility and penetrability. At the same time, the hydrophilicity, rich N content and high reactivity of the terminal amino group of polyethyleneimine are utilized to graft-modify the oxidized nano-carbon black with polyethyleneimine (with a relatively low molecular weight). This can change the surface wettability of the nano-carbon black, making the nano-carbon black amphiphilic and carrying a positive charge on the surface, thereby improving its flocculation and aggregation capabilities and enhancing its interfacial activity and demulsification capabilities. In addition, grafting quaternary ammonium salt on the surface of polyethyleneimine modified nano carbon black can further enhance its surface positive charge and interfacial activity, enabling it to diffuse faster in oily wastewater, have stronger flocculation and aggregation ability, and quickly adsorb at the oil-water interface, replacing the asphaltene interfacial film, softening or demulsifying the interfacial film, reducing the stability of the interfacial film, and being able to undergo electrostatic neutralization with the interfacial film, further reducing the stability of the interfacial film, promoting demulsification, and effectively ensuring the quality of the aqueous phase separated after demulsification.
[0036] Compared with the prior art, the present invention has the following beneficial effects:
[0037] 1) The present invention first utilizes the inherent characteristics of nano-carbon black, which can interact with surface active substances and the like through π-π or n-π interactions, and then grafts and modifies the carbon black with polyethyleneimine to make it amphiphilic (the carbon black center is hydrophobic, and the grafted polyethyleneimine is hydrophilic). The branched low-molecular-weight polyethyleneimine can enhance flocculation and agglomeration. Grafting a quaternary ammonium salt can further enhance the positive charge and promote the electrostatic neutralization ability of the demulsifier, thereby enhancing its flocculation and agglomeration ability and promoting demulsification. The resulting cationic polyethyleneimine-modified nano-carbon black demulsifier is a cationic demulsifier with a π conjugated system, which has the advantages of high demulsification efficiency, low dosage, strong salt and acid resistance, and high quality of separated aqueous phase.
[0038] 2) The preparation method of the demulsifier of the present invention is relatively simple and easy to operate, and the pH value and salinity range of the applicable oily wastewater are wide, which is suitable for promotion and application.
[0039] Figures in the specification
[0040] Figure 1 This is the FTIR spectrum of the cationic polyethyleneimine modified nano-carbon black demulsifier obtained in Example 1.
[0041] Figure 2 Schematic diagram of the preparation process of cationic polyethyleneimine modified nano carbon black demulsifier. DETAILED DESCRIPTION
[0042] The present invention will be further described in detail below with reference to the embodiments for a clearer understanding of the present invention, but they do not limit the present invention.
[0043] In the following examples, the nano carbon black used was provided by Shanghai MacLean Biochemical Technology Co., Ltd., and its average particle size was 30 nm.
[0044] Example 1
[0045] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0046] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 5 g of polyethyleneimine (Mw = 2500) were added to 20 mL of chloroform, and then 3 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.1 g of 1-hydroxybenzotriazole were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 3 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0047] Depend on Figure 1 It can be seen from the FTIR spectrum of the cationic polyethyleneimine modified nano carbon black demulsifier prepared in Example 1 that the 3400 cm -1 The characteristic peak at 1750cm is the absorption peak of hydroxyl group. -1 The characteristic peak at 1605cm belongs to the absorption peak of carboxyl group. -1 The characteristic peak at 1480 cm is the absorption peak of C=C. -1 and 958cm -1 The characteristic peak at 1080 is the absorption peak of CN, and the characteristic peak at 1080 is the absorption peak of COC, which proves that the target cationic polyethyleneimine modified nano-carbon black demulsifier is successfully synthesized.
[0048] Example 2
[0049] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0050] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 4 g of polyethyleneimine (Mw = 1800) were added to 20 mL of tetrahydrofuran, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 2.5 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0051] Example 3
[0052] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0053] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 3 g of polyethyleneimine (Mw = 1200) were added to 20 mL of dioxane, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-pyrrolidinopyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 2.5 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0054] Example 4
[0055] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0056] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 2 g of polyethyleneimine (Mw = 600) were added to 20 mL of chloroform, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 1.5 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0057] Example 5
[0058] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0059] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 2 g of polyethyleneimine (Mw = 300) were added to 20 mL of acetone, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 1.5 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0060] Example 6
[0061] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0062] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 2 g of polyethyleneimine (Mw = 2500) were added to 20 mL of chloroform, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 3 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0063] Comparative Example 1
[0064] A modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0065] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 5 g of polyethyleneimine (Mw = 2500) were added to 20 mL of chloroform, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain a polyethyleneimine-modified nano-carbon black demulsifier.
[0066] Comparative Example 2
[0067] An oxidized carbon black demulsifier, the preparation method of which comprises the following steps:
[0068] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and reacted at 60°C for 3 h to obtain oxidized carbon black.
[0069] Comparative Example 3
[0070] A quaternary ammonium salt modified polyethyleneimine demulsifier, the preparation method of which comprises the following steps:
[0071] 2 g of polyethyleneimine (Mw=2500) was added to 20 mL of tetrahydrofuran, and then 2 g of epoxypropyltrimethylammonium chloride was added, and the mixture was reacted at 60° C. for 4 h to obtain a quaternary ammonium salt-modified polyethyleneimine demulsifier.
[0072] Comparative Example 4
[0073] A cationic polyethyleneimine modified nano carbon black demulsifier, the preparation method of which comprises the following steps:
[0074] 1 g of nano-carbon black was added to 20 mL of persulfate / sulfuric acid solution (wherein the concentration of ammonium persulfate was 2 mol / L, the concentration of H2SO4 was 1 mol / L, and the rest was water), and the reaction was carried out at 60°C for 3 h to obtain oxidized carbon black; 1 g of oxidized carbon black and 2 g of polyethyleneimine (Mw = 5000) were added to 20 mL of chloroform, and then 3 g of dicyclohexylcarbodiimide and 0.1 g of 4-N,N-dimethylpyridine were added, and the reaction was carried out at 60°C for 4 h to obtain polyethyleneimine-modified nano-carbon black; then 1.5 g of polyethyleneimine-modified nano-carbon black and 3 g of epoxypropyltrimethylammonium chloride were added to 20 mL of chloroform, and the reaction was carried out at 60°C for 4 h to obtain a cationic polyethyleneimine-modified nano-carbon black demulsifier.
[0075] Application Examples
[0076] 1. Application effects of different demulsifiers
[0077] The demulsifiers prepared in Examples 1-6 and Comparative Examples 1-3 were respectively applied to demulsify oily wastewater, and the specific steps included:
[0078] 1) 1 part by weight of crude oil was added to 99 parts by weight of water, stirred and mixed, heated to 60° C., and then stirred in a homogenizer at a speed of 11,000 r / min for 30 minutes until stable oily wastewater was formed;
[0079] 2) adding the demulsifier obtained in Example 1-6 or Comparative Example 1-3 to 20 parts by weight of water to prepare a demulsifier aqueous dispersion with a mass fraction of 0.1%;
[0080] 3) 1 part by volume of the obtained demulsifier aqueous dispersion was added to 20 parts by volume of the obtained oily wastewater, shaken thoroughly to mix evenly, and allowed to stand at room temperature for 30 minutes. The transmittance of the aqueous phase was then measured using an SP2100 spectrophotometer, and the residual oil content in the separated aqueous phase was measured in accordance with the provisions of the standard SY / T 0530-2011 "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method". The results are shown in Table 1.
[0081] Table 1
[0082]
[0083]
[0084] As shown in Table 1, the cationic polyethyleneimine-modified nano-carbon black demulsifier provided by the present invention has a high demulsification efficiency at low concentrations, a clear aqueous phase after demulsification, and a low residual oil content in the aqueous phase. The demulsifier obtained in Comparative Example 1 has a low transmittance of the aqueous phase after demulsification, and a high residual oil content in the aqueous phase; the demulsification efficiency of the nano-carbon black obtained by simple oxidation modification in Comparative Example 2 is even lower. The demulsification efficiency of the quaternary ammonium salt-modified polyethyleneimine obtained in Comparative Example 3 is also low. In Comparative Example 4, a high molecular weight polyethyleneimine is used for modification, and the demulsification efficiency is also low.
[0085] 2. Application Effect of Different Concentrations of Cationic Polyethyleneimine Modified Nano-carbon Black Demulsifier Based on the demulsifier prepared in Example 1, the application effect of different concentrations of cationic polyethyleneimine modified nano-carbon black demulsifier in demulsifying oily wastewater was characterized. The specific steps are as follows:
[0086] 1) 1 part by weight of crude oil was added to 99 parts by weight of water, stirred and mixed, heated to 60° C., and then stirred in a homogenizer at a speed of 11,000 r / min for 30 minutes until stable oily wastewater was formed;
[0087] 2) A certain amount of the demulsifier prepared in Example 1 was added to 20 parts by weight of deionized water to prepare demulsifier aqueous dispersions with mass fractions of 0.2%, 0.15%, 0.1%, 0.05%, and 0%, respectively, which were recorded as experimental groups 1-5;
[0088] 3) 1 part by volume of the above demulsifier aqueous solution was added to 20 parts by volume of the above oily wastewater, shaken thoroughly to mix evenly, and allowed to stand at room temperature for 30 minutes. The transmittance of the aqueous phase was then measured using an SP2100 spectrophotometer, and the residual oil content in the separated aqueous phase was measured in accordance with the provisions of the standard SY / T 0530-2011 "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method". The results are shown in Table 2.
[0089] Table 2
[0090]
[0091] As shown in Table 2, the cationic polyethyleneimine modified nano-carbon black demulsifier provided by the present invention can exhibit good demulsification efficiency at low concentrations.
[0092] 3. Application effect on oily wastewater with different pH values
[0093] Based on the demulsifier prepared in Example 1, the application effect of the cationic polyethyleneimine modified nano-carbon black demulsifier in demulsifying oily wastewater at different pH values is characterized, and the specific steps are as follows:
[0094] 1) 1 part by weight of crude oil was added to 99 parts by weight of water, stirred and mixed, heated to 60°C, and the pH value was adjusted to 3, 5, 7, 9, and 11 using hydrochloric acid and sodium hydroxide (respectively, denoted as experimental groups 6-10). The mixture was then stirred in a homogenizer at a speed of 11,000 rpm for 30 minutes until stable oily wastewater was formed.
[0095] 2) adding a certain amount of the demulsifier prepared in Example 1 to 20 parts by weight of deionized water to prepare a demulsifier aqueous dispersion with a mass fraction of 0.1%;
[0096] 3) 1 part by volume of the above demulsifier aqueous solution was added to 20 parts by volume of the above oily wastewater, shaken thoroughly to mix evenly, and allowed to stand at room temperature for 30 minutes. The transmittance of the aqueous phase was then measured using an SP2100 spectrophotometer, and the residual oil content in the separated aqueous phase was measured in accordance with the provisions of the standard SY / T 0530-2011 "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method". The results are shown in Table 3.
[0097] Table 3
[0098]
[0099] As shown in Table 3, the cationic polyethyleneimine modified nano-carbon black demulsifier provided by the present invention has good demulsification efficiency at different pH values.
[0100] 4. Application effect on oily wastewater with different salinity
[0101] Based on the demulsifier prepared in Example 1, the application effect of the cationic polyethyleneimine modified nano-carbon black demulsifier in demulsifying oily wastewater with different salinities was characterized. The specific steps are as follows:
[0102] 1) 1 part by weight of crude oil was added to 99 parts by weight of water, stirred and mixed, heated to 60°C, and the salinity was adjusted with sodium chloride (0, 10,000, 20,000, 30,000, 40,000, and 50,000 mg / L, respectively, denoted as experimental groups 11-16). The mixture was then stirred in a homogenizer at 11,000 rpm for 30 minutes until stable oily wastewater was formed.
[0103] 2) A certain amount of the demulsifier prepared in Example 1 was added to 20 parts by weight of deionized water to prepare a demulsifier aqueous dispersion with a mass fraction of 0.1%.
[0104] 3) 1 part by volume of the above demulsifier aqueous solution was added to 20 parts by volume of the above oily wastewater, shaken thoroughly to mix evenly, and allowed to stand at room temperature for 30 minutes. The transmittance of the aqueous phase was then measured using an SP2100 spectrophotometer, and the residual oil content in the separated aqueous phase was measured in accordance with the provisions of the standard SY / T 0530-2011 "Determination of Oil Content in Oilfield Produced Water - Spectrophotometric Method". The results are shown in Table 4.
[0105] Table 4
[0106]
[0107] As shown in Table 4, the cationic polyethyleneimine modified nano-carbon black demulsifier provided by the present invention has good demulsification efficiency at different salinities.
[0108] In summary, the cationic polyethyleneimine modified nano-carbon black demulsifier provided by the present invention can demulsify stable oily wastewater at room temperature, and the demulsifier dosage is small, the demulsification rate is fast, the demulsification efficiency is high, the transmittance of the separated water phase after demulsification is high, and the residual oil content is low.
[0109] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.
Claims
1. A cationic polyethyleneimine modified nano carbon black demulsifier, characterized in that: The nano carbon black is obtained by sequentially oxidizing, grafting polyethyleneimine, and grafting quaternary ammonium salt modification.
2. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 1, characterized in that: The molecular weight of the polyethyleneimine is 300-4500.
3. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 1, characterized in that: The quaternary ammonium salt is one or more of 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and (3-carboxypropyl)trimethylammonium chloride.
4. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 1, characterized in that: The oxidation step comprises: adding nano carbon black into a persulfate / sulfuric acid solution, reacting at 20-60° C. for 1-24 hours to obtain oxidized carbon black.
5. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 1, characterized in that: The polyethyleneimine grafting step comprises: adding oxidized carbon black and polyethyleneimine into a solvent, then adding a condensing agent and an activator, and reacting at 20-60° C. for 1-12 hours to obtain polyethyleneimine grafted modified nano carbon black.
6. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 5, characterized in that: The condensing agent is one or more of dicyclohexylcarbodiimide, diisopropylcarbodiimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; the activating agent is one or more of 4-N,N-dimethylpyridine, 4-pyrrolidinylpyridine, 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole, and N-hydroxyphthalimide.
7. The cationic polyethyleneimine modified nano carbon black demulsifier according to claim 1, characterized in that: The grafting step of quaternary ammonium salt comprises: adding quaternary ammonium salt to polyethyleneimine modified nano carbon black, performing heating reaction, removing impurities and solvent, and obtaining cationic polyethyleneimine modified nano carbon black demulsifier.
8. A method for preparing the cationic polyethyleneimine modified nano-carbon black demulsifier according to any one of claims 1 to 7, comprising the following steps: 1) Oxidation of nanocarbon black: Add nanocarbon black to a persulfate / sulfuric acid solution and react at 20-60° C. for 1-24 hours to obtain oxidized carbon black; 2) Grafting polyethyleneimine: adding oxidized carbon black and polyethyleneimine to a solvent, then adding a condensing agent and an activator, and reacting at 20-60° C. for 1-12 hours to obtain polyethyleneimine-modified nanocarbon black; 3) Grafting quaternary ammonium salt; adding the quaternary ammonium salt to the polyethyleneimine-modified nano-carbon black, heating the reaction, removing impurities and solvents, and obtaining a cationic polyethyleneimine-modified nano-carbon black demulsifier.
9. The preparation method according to claim 8, characterized in that The mass ratio of the oxidized carbon black to the polyethyleneimine is 1:(2-5); the mass ratio of the quaternary ammonium salt to the polyethyleneimine-modified nano-carbon black is (1-2):
1.
10. Use of the cationic polyethyleneimine-modified nano-carbon black demulsifier according to any one of claims 1 to 7 or the cationic polyethyleneimine-modified nano-carbon black demulsifier prepared by the preparation method according to any one of claims 8 to 9 in oily wastewater.