CN100999317A - Nitrogen-containing ordered mesopore carbon and its synthesis method - Google Patents

Abstract

The invention discloses a novel nitrogen-containing ordered mesoporous carbon, its synthesis method and its preliminary application in the field of adsorption. Synthesis method: In an organic solvent, the soluble resin reacts with the nitrogen-containing organic precursor, and then uses this precursor to self-assemble with the non-ionic surfactant to obtain the nitrogen-containing resin-non-ionic surfactant composite material. The nitrogen-containing ordered mesoporous polymer is obtained by roasting, and further carbonized to obtain the nitrogen-containing ordered mesoporous carbon; or the nitrogen-containing resin-nonionic surfactant composite material is carbonized at a high temperature in one step to obtain the nitrogen-containing ordered mesoporous carbon. The prepared mesoporous carbon has a pore diameter of 2.0-6.0 nm, a pore volume of 0.10-1.00 cm ³ /g, a specific surface area of 500-1200 m ² /g, and a carbon-nitrogen molar ratio of 100:0.20-100:10.00. The invention has simple operation and low cost, and can be used as an adsorbent for phenolic compounds in waste water. At the same time, it is expected to have broad applications in catalysis, adsorption of heavy metal ions, dye molecules, and electrode materials.

Description

Nitrogen-containing ordered mesoporous carbon and its synthesis method

technical field

The invention belongs to the technical field of material preparation, and specifically relates to a novel nitrogen-containing ordered mesoporous carbon material, a preparation method and an application in the field of adsorption.

Background technique

Mesoporous carbon materials have attracted widespread attention because on the one hand, these materials have mesoscopically ordered structures, uniform mesoporous channels, high specific surface area and large pore volume, and on the other hand, they have the characteristics of carbon materials themselves. Therefore, it has broad applications in the fields of adsorption, catalysis, separation, electrochemical electrodes, photoelectric devices, protein adsorption and separation, etc. The functionalized mesoporous carbon materials obtained by further functionalization will surely show more excellent performance and expand the field of practical application. However, compared with traditional mesoporous silica, the chemical inertness of the surface of carbon materials makes it difficult to functionalize. At present, several common functionalization methods are: (1) direct carbonization of organic mesoporous silica; (2) surface treatment; (3) nano-casting method.

Ordered mesoporous materials synthesized from bridged organosilanes and supramolecular templates, that is, periodic mesoporous organosilica materials, referred to as PMOs (Periodic Mesoporous Organosilicas), represent a novel class of organic-inorganic nanocomponents. Its main advantages are (1) the content of organic functional groups can be greatly increased, and 100% of silicon atoms are connected to organic groups, while the connection rate of the terminal organic groups of the above-mentioned mesoporous silica can only reach 25%. The degree of apparent order is already very low; (2) the organic groups are evenly distributed in the skeleton, thus effectively avoiding the problem of orifice blockage; The introduction of the group into the pore wall can well adjust the physical and chemical properties of the material. After further carbonization, a multi-component hybrid material retaining some functional groups, silicon oxide and carbon, can be obtained. However, in such materials, expensive bridged organosilanes are used, and due to the limitations of such silanes, the introduction of functional components is relatively simple. This method is also not applicable to mesoporous materials other than silica components.

In the surface treatment method, a strong oxidizing agent or a strong reducing agent can be used to oxidize or reduce the surface and introduce functional components. Fluorine gas purging can also be used to fluorinate the surface of the carbon material. However, these methods have complicated steps and are difficult to control.

The functionalization of ordered mesoporous carbon can also adopt the method of nano-casting, which is mainly used for the preparation of nitrogen-containing ordered mesoporous carbon at present. That is to prepare ordered mesoporous silica materials (such as SBA-15, MCM-48, etc.), and then use such materials as hard templates to infuse nitrogen-containing carbon sources (such as: ethylenediamine/tetrachloride) in the mesoporous channels. carbonization, polypyrrole, acetonitrile, polyacrylonitrile, etc.), high-temperature carbonization, and finally dissolving and removing silicon oxide by hydrofluoric acid or sodium hydroxide solution, to obtain a nitrogen-containing mesoporous carbon material with a reverse-phase replication template mesostructure. The preparation process of this kind of method is loaded down with trivial details, and the period is long. Therefore, there is an urgent need for a method to introduce functional groups into mesoporous carbons self-assembled from surfactants.

Contents of the invention

In view of the deficiencies in the prior art, one of the problems to be solved in the present invention is to provide a novel nitrogen-containing ordered mesoporous carbon material;

The second problem to be solved in the present invention is to provide a synthesis method for the nitrogen-containing ordered mesoporous carbon material;

The technical scheme that the present invention solves the problems of the technologies described above is as follows:

A nitrogen-containing ordered mesoporous carbon, the pore diameter is 2.0-6.0nm, the pore volume is 0.10-1.00cm ³ /g, the specific surface area is 500-1200m ² /g, and the carbon-nitrogen molar ratio is 100:0.20-100: 10.00.

The synthesis method of this nitrogen-containing ordered mesoporous carbon comprises the following steps:

(1) At room temperature, disperse the soluble resin precursor in an organic solvent, add a nitrogen-containing organic precursor, and react to obtain a clear solution; the mass ratio of the nitrogen-containing organic precursor to the soluble resin precursor is 0 to 1.00, and the reaction time is 1 to 5 hours;

(2) dissolving the nonionic surfactant in an organic solvent to obtain a clear solution;

(3) then mix the two solutions of (1) and (2) steps, stir and make the solvent volatilize; Low-temperature roasting under atmosphere, the low-temperature roasting temperature is 350-500°C; the heating rate is 1-5°C/min. The nitrogen-containing ordered mesoporous polymer is obtained, and the nitrogen-containing ordered mesoporous polymer is further carbonized to obtain the nitrogen-containing ordered mesoporous carbon of the present invention, or the nitrogen-containing resin-nonionic surfactant composite material is carbonized at a high temperature in one step to obtain The nitrogen-containing ordered mesoporous carbon of the present invention.

The low-temperature curing temperature in the above step (3) is 80° C. to 120° C., and the time is 12 to 72 hours.

The inert atmosphere in the above step (3) can be nitrogen or argon.

The nitrogen-containing ordered mesoporous polymer described in the above step (3) is further carbonized under an inert atmosphere to obtain nitrogen-containing ordered mesoporous carbon. 1-5°C/min.

The nitrogen-containing resin-nonionic surfactant composite material described in the above (3) step is carbonized at a high temperature in an inert atmosphere in the next step to obtain nitrogen-containing ordered mesoporous carbon. The carbonization process is: roasting at 350-500° C. hours, then raise the temperature to 600-900°C, and bake for 4-10 hours at a heating rate of 1-5°C/min.

The reaction mechanism of the present invention is: in an organic solvent, the soluble resin reacts with the nitrogen-containing organic precursor, and then utilizes the organic-organic self-assembly of the precursor and the nonionic surfactant to obtain the nitrogen-containing resin-nonionic surfactant Composite materials, low-temperature roasting in an inert atmosphere to remove the surfactant, that is, to obtain a nitrogen-containing ordered mesoporous polymer, which is further carbonized to obtain a nitrogen-containing ordered mesoporous carbon with a corresponding structure; or the nitrogen-containing resin obtained by self-assembly-non- Nitrogen-containing ordered mesoporous carbon obtained by one-step high-temperature carbonization of ionic surfactant composites.

The organic solvent used is one or more of alcohols, benzenes, tetrahydrofuran, ether, chloroform or dichloromethane, etc., and the present invention utilizes the volatilization of organic solvents to induce self-assembly of nonionic surfactants to form highly ordered media Pore structure, organic solvents can be protic solvents, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, tetrahydrofuran, etc., or aprotic solvents, such as benzene, toluene, ether, chloroform, dichloro methane etc.

The soluble resin used can be one or more of phenolic resin, urea-formaldehyde resin, polyimide, polyacrylamide, polyacrylonitrile, etc., and their molecular weight is 200-5000; the nitrogen-containing organic precursor used can be One or more of aniline, m-aminophenol, p-aminophenol, etc.

In the present invention, the nonionic surfactant used is polyethylene oxide-polypropylene oxide, polyethylene oxide-polybutylene oxide, alkane-polyoxyethylene type diblock or triblock Surfactants such as copolymers. Such as C _n H _2n+1 EO _m , EO _n PO _m EO _n , EO _n BO _m EO _n , EO _n BO _m , EO _n PO _m and so on.

结构。In the present invention, the nonionic surfactants used mainly include Brij35 (C ₁₂ H ₂₅ EO ₂₃ ), Brij56 (C ₁₆ H ₃₃ EO ₁₀ ), Brij76 (C ₁₈ H ₃₇ EO ₁₀ ), P123 (EO ₂₀ PO ₇₀ EO ₂₀ ), F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ ), F108 (EO ₁₃₂ PO ₅₀ EO ₁₃₂ ), etc. The pore space symmetry of the resulting product can be a two-dimensional hexagonal structure, the space group includes the p6mm structure, or a three-dimensional cubic structure, the space group includes the structure

structure.

In the present invention, a soluble resin is used as a precursor for synthesizing a polymer mesoporous material, which has a low molecular weight at the initial stage of the reaction, can be well dissolved in an organic solvent, and forms a homogeneous system with an organic solvent and a nonionic surfactant. After solvent volatilization induces the formation of mesoscopic structure, the temperature is raised to the reaction temperature, and the soluble resin precursor can be further cross-linked, and finally an insoluble and infusible polymer material is obtained. Compared with nonionic surfactants, the polymer materials used have higher thermal stability or chemical stability.

In the present invention, the soluble resin used may be a commercial polymer precursor, or a self-made polymer oligomer precursor. They can be one or more of phenolic resin, urea-formaldehyde resin, polyimide, polyacrylamide, polyacrylonitrile, etc. The molecular weight of the precursor is generally between 200 and 5000.

In the present invention, the nitrogen-containing organic precursor used may be one or more of aniline, m-aminophenol, p-aminophenol and the like.

The invention synthesizes ordered mesoporous carbon with continuous and open pore structure through organic-organic self-assembly. For further functionalization, nitrogen-containing carbon sources were introduced into the system, and nitrogen-containing ordered mesoporous carbons were prepared by solvent evaporation-induced organic-organic self-assembly method. This type of material has an open framework structure, and it was applied for the adsorption of the target pollutant phenol for the first time.

The preparation method of the mesoporous material of the invention is simple and easy, and the cost is low. The nitrogen-containing ordered mesoporous carbon prepared by the invention contains nitrogen atoms in the skeleton, and has highly ordered pores, high specific surface area, large pore diameter and large pore volume. These new nitrogen-containing mesoporous materials have good adsorption capacity in the treatment of phenol-containing wastewater. Under the same conditions, the phenol adsorption capacity of activated carbon is 50-200 mg/g, and the phenol adsorption capacity of nitrogen-containing mesoporous carbon is 150 mg/g. ~500mg/g. At the same time, the nitrogen-containing ordered mesoporous material has broad application prospects in catalysis, adsorption of heavy metal ions in wastewater, adsorption of dye molecules, and electrode materials.

Description of drawings

Fig. 1 is a characteristic X-ray diffraction (XRD) pattern of the nitrogen-containing ordered mesoporous carbon material with a two-dimensional hexagonal p6mm structure of the present invention.

Fig. 2 is a characteristic nitrogen adsorption-desorption isotherm diagram of the nitrogen-containing ordered mesoporous carbon material with a two-dimensional hexagonal p6mm structure of the present invention.

Fig. 3 is a TEM image of nitrogen-containing ordered mesoporous carbon with a two-dimensional hexagonal p6mm structure of the present invention.

结构的含氮有序介孔碳的特征X-射线衍射(XRD)图谱。Fig. 4 is that the present invention has three-dimensional cube

The characteristic X-ray diffraction (XRD) pattern of nitrogen-containing ordered mesoporous carbon.

Fig. 5 is that the present invention has three-dimensional cube Characteristic nitrogen adsorption–desorption isotherm diagrams of nitrogen-containing ordered mesoporous carbons.

结构的含氮有序介孔碳的TEM图。Fig. 6 is that the present invention has three-dimensional cube

TEM images of nitrogen-containing ordered mesoporous carbons.

Fig. 7 is a graph showing the phenol adsorption capacity of the mesoporous carbon of the present invention.

in:

Figure 1 shows solution A obtained after dissolving 0.02g m-aminophenol in 5.00g soluble resin precursor and stirring for 2 hours. Dissolve 0.61g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 30 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 100°C for 48 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. Calcined at 350°C for 5 hours to obtain a nitrogen-containing mesoporous polymer, and then calcined at 900°C for 5 hours to carbonize to obtain the characteristic X-ray diffraction (XRD) spectrum of nitrogen-containing ordered mesoporous carbon materials.

Figure 2 shows solution A obtained after dissolving 0.02g m-aminophenol in 5.00g soluble resin precursor and stirring for 2 hours. Dissolve 0.61g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 30 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 100°C for 48 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. Calcined at 350°C for 5 hours to obtain nitrogen-containing mesoporous polymers, and then calcined at 900°C for 5 hours to carbonize to obtain the characteristic nitrogen adsorption-desorption isotherm diagram of nitrogen-containing ordered mesoporous carbon materials.

Figure 3 shows solution A obtained after dissolving 0.05g m-aminophenol in 5.00g soluble resin precursor and stirring for 3 hours. Dissolve 0.61g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 60 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 90°C for 48 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. Calcined at 900°C for 5 hours in one-step method, and carbonized to obtain the TEM image of nitrogen-containing ordered mesoporous carbon material.

Figure 4 shows solution A obtained after dissolving 0.02g m-aminophenol in 5.00g soluble resin precursor and stirring for 2 hours. Dissolve 0.42g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 10 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 90°C for 32 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. The next step method is calcining at 900°C for 6 hours, and carbonization to obtain the characteristic X-ray diffraction (XRD) pattern of nitrogen-containing ordered mesoporous carbon.

Figure 5 shows solution A obtained after dissolving 0.02g m-aminophenol in 5.00g soluble resin precursor and stirring for 2 hours. Dissolve 0.42g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 10 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 90°C for 32 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. The next step method is roasting at 900°C for 6 hours, and carbonization to obtain the characteristic nitrogen adsorption-desorption isotherm diagram of nitrogen-containing ordered mesoporous carbon.

Figure 6 shows solution A obtained after dissolving 0.05g m-aminophenol in 5.00g soluble resin precursor and stirring for 3 hours. Dissolve 0.42g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix A and B solutions, stir for 30 minutes and pour them into a petri dish. After the solvent evaporates, cure at a low temperature of 100°C for 24 hours to obtain a nitrogen-containing resin-nonionic surfactant composite material. The TEM image of nitrogen-containing ordered mesoporous carbon was obtained by one-step calcination at 900°C for 6 hours and carbonization.

Figure 7 shows that a nitrogen-containing mesoporous carbon material with a mass ratio of m-aminophenol to soluble resin precursor of 0.05 is placed in a 100mL dry iodine flask, and 40mL of a phenol solution with a concentration of 0.564mg/mL is placed at a constant temperature of 25°C. Shake the adsorption for 24 hours, measure the phenol concentration with an ultraviolet absorption photometer, and calculate the figure obtained by calculating the amount of phenol adsorption.

Detailed ways

The present invention will be further described below through specific embodiments, and these examples are listed only for illustration and not to limit the present invention in any way.

Example 1

The preparation of soluble resin precursor solution, 8.00g phenol is put in three-necked flask, 42 ℃ of water-bath heatings, make phenol be transparent liquid, prepare 20% sodium hydroxide solution (take by weighing 0.34gNaOH, add 1.36g distilled water), Slowly drop into the phenol liquid. After 10 minutes, 14.16 g of formaldehyde solution with a mass percentage of 37% was added, refluxed at 70° C. for 1 hour, cooled to room temperature, and adjusted to neutral pH with 2 mol/L hydrochloric acid. Distill under reduced pressure at 45°C to 50°C, cool to room temperature, and prepare 20% ethanol or ether solution.

Example 2

0.02 g of m-aminophenol was dissolved in 5.00 g of the soluble resin precursor obtained in Example 1, and the solution A was obtained after stirring for 2 hours. Dissolve 0.61g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix solutions A and B and stir for 30 minutes. Then spread the mixed solution evenly in a petri dish, leave it at room temperature for 7 hours, and finally transfer it to an oven at 100°C. After 24 hours, the product was baked at 350°C for 5 hours under a nitrogen atmosphere to obtain a nitrogen-containing mesoporous polymer, and then 900 The nitrogen-containing mesoporous carbon material was obtained by calcination at ℃ for 5 hours. As shown in Figure 1, the XRD spectrum proves that the material has a two-dimensional hexagonal structure (space group p6mm), the pore diameter is 4.3nm, and the pore volume is 0.63cm ³ /g. The specific surface area is 1177m ² /g, and its N ₂ adsorption-desorption isotherm belongs to type IV (as shown in Figure 2). Elemental analysis proves that the molar ratio of carbon to nitrogen in the nitrogen-containing mesoporous carbon is 100:0.85.

Example 3

0.05g m-aminophenol was dissolved in the ether solution of the soluble resin obtained in 5.00g Example 1, and after stirring for 2 hours, A solution was obtained. Dissolve 0.61g of F127 in 8.00g of ether and stir for 10 minutes to obtain solution B. Mix solutions A and B and stir for 60 minutes. Then spread the mixture evenly in a petri dish, leave it at room temperature for 7 hours, and finally transfer it to an oven at 120°C. After 24 hours, the product is baked at 600°C and 900°C under the protection of nitrogen for 6 hours respectively to obtain nitrogen-containing mesoporous cells. Carbon materials, all have a two-dimensional hexagonal structure (space group p6mm), the pore diameters are 5.2nm and 4.0nm, the pore volumes are 0.42cm ³ /g and 0.43cm ³ /g, and the specific surface areas are 705m ² /g and 890m ² /g.

Example 4

0.02 g of m-aminophenol was dissolved in 5.00 g of the soluble resin precursor obtained in Example 1, and after stirring for 2 hours, A solution was obtained. Dissolve 0.42g of F127 in 8.00g of absolute ethanol and stir for 10 minutes to obtain solution B. Mix solutions A and B and stir for 10 minutes. Then spread the mixture evenly in a petri dish, leave it at room temperature for 7 hours, and finally transfer it to an oven at 90°C. After 32 hours, the product was calcined at 900°C for 6 hours under an argon atmosphere to obtain a nitrogen-containing mesoporous carbon material. The mesoporous carbon material has a three-dimensional cubic structure (space group As shown in Figure 4), the pore diameter is 3.9nm, the pore volume is 0.31cm ³ /g, the specific surface area is 709m ² /g, and its N ₂ adsorption-desorption isotherm belongs to type IV (as shown in Figure 5).

Example 5

Put activated carbon in a 100mL dry iodine flask, put 40mL of phenol solution with a concentration of 0.564mg/mL, and absorb at a constant temperature of 25°C for 24 hours, filter, take 1mL of the clear liquid and dilute it into a 100mL aqueous solution, and measure it with an ultraviolet absorption photometer its phenol concentration. At equilibrium, the relationship between the adsorption capacity Qe (mg/mL) and the equilibrium concentration is: Qe=(Co-Ce)V/grams of resin. In the formula: Co-the initial concentration of phenol (mg/mL), Ce-the concentration of phenol at equilibrium (mg/mL), V-the total volume of the solution (mL). The calculated phenol adsorption capacity is 50mG/g, as shown in Figure 7.

Example 6

Put nitrogen-containing mesoporous carbon with a mass ratio of m-aminophenol to soluble resin precursor of 0.05 in a 100mL dry iodine flask, put 40mL of phenol solution with a concentration of 0.564mg/mL, and absorb at a constant temperature of 25°C for 24 hours , filtered, take 1mL of the clear solution and dilute it into 100mL aqueous solution, and measure the phenol concentration with an ultraviolet absorption photometer. Calculated according to example 5, its phenol adsorption capacity is 288mg/g, as shown in Figure 7.

Claims (12)

1. A nitrogen-containing ordered mesoporous carbon, characterized in that the nitrogen-containing ordered mesoporous carbon has a pore diameter of 2.0-6.0 nm, a pore volume of 0.10-1.00 cm ³ /g, and a specific surface area of 500-1200 m ² / g, the molar ratio of carbon to nitrogen is 100:0.20 to 100:10.00. 2. The synthesis method of nitrogen-containing ordered mesoporous carbon according to claim 1, comprising the steps of: (1) At room temperature, disperse the soluble resin precursor in an organic solvent, add a nitrogen-containing organic precursor, and react to obtain a clear solution; the mass ratio of the nitrogen-containing organic precursor to the soluble resin precursor is 0 to 1.00, and the reaction time is 1 to 5 hours; (2) dissolving the nonionic surfactant in an organic solvent to obtain a clear solution; (3) then mix the two kinds of solutions of (1) and (2) steps, stir and make the solvent volatilize; Roasting at low temperature under the atmosphere can obtain the nitrogen-containing ordered mesoporous polymer, which can be further carbonized to obtain the nitrogen-containing ordered mesoporous carbon of the present invention, or one-step high-temperature carbonization of the nitrogen-containing resin-nonionic surfactant composite material to obtain the present invention. Nitrogen ordered mesoporous carbon. 3. The synthesis method according to claim 2, characterized in that: the low-temperature curing temperature in the step (3) is 80-120° C., and the curing time is 12-72 hours. 4. The synthesis method according to claim 2, characterized in that: the low-temperature calcination temperature in the step (3) is 350-500°C; the heating rate is 1-5°C/min. 5. The synthesis method according to claim 2, characterized in that: the inert atmosphere used for roasting in the step (3) is nitrogen or argon. 6. The synthesis method according to claim 2, characterized in that: in step (3), the nitrogen-containing ordered mesoporous polymer is further carbonized under an inert atmosphere to obtain a nitrogen-containing ordered mesoporous carbon with a carbonization temperature of 600 ~900°C, the firing time is 4-10 hours, and the heating rate is 1-5°C/min. 7. The synthesis method according to claim 2, characterized in that: the nitrogen-containing resin-nonionic surfactant composite material in the step (3) is carbonized at a high temperature in the next step in an inert atmosphere to obtain nitrogen-containing ordered mesoporous carbon The carbonization process is as follows: roasting at 350-500°C for 5-10 hours, then raising the temperature to 600-900°C, roasting for 4-10 hours, and the heating rate is 1-5°C/min. 8. The synthesis method according to any one of claims 2-7, wherein the soluble resin is one of phenolic resin, urea-formaldehyde resin, polyimide, polyacrylamide, and polyacrylonitrile Or more than one mixture, their molecular weight is 200-5000. 9. The synthesis method according to any one of claims 2-7, characterized in that: the nitrogen-containing organic precursor is one or a mixture of aniline, m-aminophenol, p-aminophenol . 10. The synthesis method according to any one of claims 2-7, characterized in that: the nonionic surfactant is polyethylene oxide-polypropylene oxide, polyethylene oxide-polycyclic One or more mixtures of oxybutylene, alkane-polyethylene oxide type di-block or tri-block copolymer surfactants. 11. The synthesis method according to claim 10, characterized in that: the non-ionic surfactant is C _n H _2n+1 EO _m , EO _n PO _m EO _n , EO _n BO _m EO _n , EO _n BO _m , EO _n PO _m neutralize one or more mixtures. 12. The synthesis method according to claim 11, characterized in that: the nonionic surfactant is C ₁₂ H ₂₅ EO ₂₃ , C ₁₆ H ₃₃ EO ₁₀ , C ₁₈ H ₃₇ EO ₁₀ , EO ₂₀ PO ₇₀ EO _20. One or more mixtures of EO ₁₀₆ PO ₇₀ EO ₁₀₆ , EO ₁₃₂ PO ₅₀ EO ₁₃₂ .

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