Preparation method of adsorbent, and maa wastewater treatment device and process

Abstract

The application discloses a preparation method of an adsorbent, and a MAA wastewater treatment device and process, the adsorbent is modified by using a hydroxyquinone-polyamine coating, selective adsorption of methyl methacrylate can be realized, compared with a traditional adsorbent, the preparation process of the adsorbent is simple, controllability is strong, adsorption capacity is high, the adsorbent is green and environment-friendly, use of an organic solvent is avoided, the thickness, polarity and electrification of a polymer network can be regulated according to actual application, the adsorbent has good acid and alkali resistance and corrosion resistance, and separation of substances with different polarities can be realized. In addition, the application provides a MAA wastewater treatment process, an alkali neutralization method is used to deeply purify an extractant recovered from a rectification section, the purity of the extractant is improved, and the extraction efficiency is further improved.

Description

Technical Field

[0001] This invention relates to the field of chemical product separation and purification, specifically to an adsorbent, and a device and process for treating methacrylic acid wastewater using the adsorbent. Background Technology

[0002] Methyl methacrylate (MMA) is an important polymer monomer, mainly used in the production of plexiglass. It is also widely used as a resin, crosslinking agent, plasticizer in coatings, and additive. Currently, the main processes for producing MMA are the acetone cyanohydrin method, ethylene carbonylation, and the C4 process. Compared with the first two processes, the C4 process has higher atom utilization, is more environmentally friendly, and has a higher MMA yield, and has gradually replaced the other two processes. Its main process is as follows: isobutylene is catalytically oxidized to produce methacrolein (MAL), which is then oxidized to produce methacrylic acid (MAA), and esterified to obtain MMA. The separation and purification of MAA is a crucial step in the C4 process. Currently, due to the low concentration of MAA in aqueous solution, the economics of producing MAA using distillation are poor. Domestic MMA production facilities all use extraction methods, with the extracted phase further distilled to achieve separation. However, due to the limited separation capacity of extraction, the raffinate still contains a certain concentration of MAA, generating a large amount of MAA-containing wastewater and causing a certain degree of product loss.

[0003] Currently, MAA wastewater is generally treated by incineration or advanced oxidation methods. Incineration is costly, uneconomical, and environmentally harmful. Furthermore, due to high formaldehyde and COD levels, biochemical treatment is not feasible. Some studies have used Fenton oxidation, but this requires large amounts of oxidant, resulting in high costs, and the useful components cannot be recovered. Adsorption can separate organic matter from the wastewater. Traditional adsorbents include activated carbon, resin, cinder, and molecular sieves. However, acrylic acid, propionic acid, and methacrylic acid have similar properties, and traditional adsorbents have relatively poor selectivity for methacrylic acid. On the other hand, the limited separation capacity of subsequent distillation means that the extractant recovered in the distillation section also contains small amounts of MAA and other impurities, reducing the purity of the extractant and hindering extraction efficiency, indirectly leading to significant loss of MAA products in the wastewater. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention improves the traditional MAA separation and purification process by preparing a surface-modified adsorbent to selectively adsorb and recover MAA from the wastewater generated in the extraction section. Furthermore, an alkali neutralization method is used to deeply purify the extractant recovered in the distillation section, thereby improving the purity of the extractant, further enhancing the extraction efficiency, and achieving zero loss of MAA products.

[0005] To achieve the above objectives, the technical solution adopted by the present invention includes the following steps:

[0006] A method for preparing an adsorbent includes the following steps:

[0007] (1) Dissolve polyamine and hydroxyquinone in an alkaline aqueous solution to form an adsorbent coating solution. Immerse microspheres in the adsorbent coating solution and keep them at 20~40℃ for 10~24h.

[0008] (2) Separate, wash with water, and dry.

[0009] In the preparation method of the adsorbent coating described in this invention, polyamines and hydroxyquinones generate oligomer monomers through the Schiff base reaction and Michael addition reaction, and the oligomer monomers are bonded to each other through non-covalent bonds to form a supramolecular network.

[0010] Taking 5-hydroxy-p-naphthoquinone as an example, the reaction is illustrated below:

[0011]

[0012] Taking 5-hydroxy-p-naphthoquinone as an example, the non-covalent interaction is illustrated below:

[0013]

[0014] Since oligomer monomers have two structures and non-covalent interactions have two forms (including hydrogen bonding and π-π interaction), there are a total of 6 types of binding between oligomer monomers. These binding types coexist to form a cross-linked network structure.

[0015] In this invention, the polyamine is one or more of ethylenediamine (EN), diethylenetriamine (DETA), triethylenediamine (TETA), tetraethylenepentamine (TEPA), and polyethyleneimine (PEI) with a weight-average molecular weight of 600, 1800, 10000, or 70000 g / mol, preferably one or more of ethylenediamine, diethylenetriamine, and PEI with a weight-average molecular weight of 600 or 1800.

[0016] In this invention, the hydroxyquinone is one or more of 5-hydroxy-p-naphthoquinone (HNQ), 5,8-dihydroxy-1,4-naphthoquinone (DHNQ), and 1,5-dihydroxyanthraquinone (DHAQ).

[0017] In this invention, the concentration range of the polyamine in the alkaline aqueous solution is 0.1-2 g / L, preferably 0.5-1.2 g / L.

[0018] In this invention, the mass ratio of the hydroxyquinone to the polyamine is 5:1 to 1:5, preferably 2:1 to 1:2.

[0019] In this invention, the alkali in the alkaline aqueous solution is selected from one or more of KOH, NaOH, and Na2CO3.

[0020] In this invention, the concentration of the alkaline aqueous solution is 1~10wt%.

[0021] In this invention, the reaction temperature of step (1) is 20~50℃, preferably 25~40℃, and the reaction time is 4~16h, preferably 5~10h.

[0022] In this invention, the microspheres are selected from one or more of molecular sieves, silica gel particles, polyacrylamide microspheres and polystyrene microspheres, and the average particle size of the microspheres is 0.1~10μm, preferably 1~5μm.

[0023] In this invention, the mass ratio of the microspheres to the alkaline aqueous solution is 1:10 to 1:100, preferably 1:50 to 1:80.

[0024] As a preferred embodiment, in this invention, the number of water washes is 2 to 10 times, preferably 3 to 6 times, and the amount of deionized water used each time is 0.1 to 1 times the mass of the alkaline aqueous solution.

[0025] In this invention, in step (3), the drying temperature is 80~120℃ and the drying time is 2~4h.

[0026] In this invention, the specific surface area of ​​the adsorbent is 1000-1980 m². 2 / g, pore volume of 2.1~3.15dm 3 / g.

[0027] The adsorbent described in this invention is a hydroxyquinone-polyamine coating modified adsorbent microsphere, with abundant amino groups on its surface and adjustable polarity. It has a high specific surface area and high adsorption capacity. Under alkaline conditions, polyamines and hydroxyquinones form a supramolecular network through the Schiff base reaction / Michael addition reaction. Then, hydroxyquinones preferentially adsorb onto the surface of the commercial adsorbent microspheres through non-covalent interactions (such as π-π electrostatic interactions and hydrophobic interactions). The supramolecular network coats the surface of the commercial adsorbent, achieving surface modification of the commercial adsorbent in the form of a coating. By controlling the feed ratio and the amino group density in the polyamine, the thickness, polarity, and charge of the polymer network can be controlled. Compared with substances such as acrylic acid, propionic acid, and acetic acid, MAA has relatively weak polarity. Therefore, selective adsorption of MAA can be achieved by controlling the polarity of the polymer network. That is, by selecting polyamines with different numbers of amino groups or different concentrations of polyamines, the polarity of the supramolecular network on the surface of the microspheres can be controlled. Generally speaking, the more amino groups, the stronger the polarity. According to the principle of like dissolves like, substances with different polarities can be selectively adsorbed.

[0028] The adsorbent described in this invention can be used to selectively adsorb MAA.

[0029] A treatment device for MAA wastewater includes an extraction tower 1, a distillation tower 2, a reaction vessel 3, a settling tank 4, an acid precipitation tank 5, and an adsorption tank 6. The upper part of the extraction tower 1 is equipped with a MAA crude acid aqueous solution feed pipeline 8. The top of the extraction tower is connected to the distillation tower 2 via a liquid phase pipeline 9. The bottom of the extraction tower 1 is connected to the adsorption tank 6 via a liquid phase pipeline 10. The top reflux tank 7 of the distillation tower 2 is connected to the reaction vessel 3 via a liquid phase pipeline 11. The lower part of the reaction vessel 3 is equipped with a discharge pipeline 13 connected to the settling tank 4. The upper part of the oil-water separation interface of the settling tank 4 is equipped with an oil phase discharge pipeline 14 connected to the lower part of the extraction tower 1. The lower part of the settling tank 4 is equipped with an aqueous phase discharge pipeline 15 connected to the acid precipitation tank 5 and the reaction vessel 3. The acid precipitation tank 5 is connected to the MAA crude acid aqueous solution feed pipeline 8 via a liquid phase pipeline 16. The top of the acid precipitation tank 5 is equipped with a sulfuric acid feed pipeline 18. The top of the reaction vessel 3 is equipped with an alkali inlet 17.

[0030] The extraction tower 1 is used for the extraction and dehydration of crude acid solution, separating MAA from the water; the distillation tower 2 is used for the recovery of the extractant; the reaction vessel 3 and the settling tank 4 are used for the neutralization reaction of residual methacrylic acid in the extractant; the acid precipitation tank 5 is used for the acid precipitation of methacrylate salts and the recovery of methacrylic acid therein; and the adsorption tank 6 is used for the further recovery of MAA from the extraction wastewater.

[0031] A MAA wastewater treatment process includes the following steps:

[0032] (a) The crude acid aqueous solution of MAA enters the extraction tower 1. The extract obtained at the top of the tower is denoted as solution A, and the raffinate obtained at the bottom of the tower is wastewater, denoted as solution B.

[0033] (b) Solution A enters distillation column 2, the extractant is obtained at the top of the column, denoted as solution C, and MAA is obtained at the bottom of the column;

[0034] (c) Solution C and alkaline solution enter reaction vessel 3 and are stirred to form an emulsion. The neutralized emulsion enters settling tank 4 for phase separation. The oil phase is circulated to extraction tower 1 and the aqueous phase is circulated to reaction vessel 3.

[0035] (d) Solution B passes through an adsorption tank 6 filled with the adsorbent described in this invention at a certain space velocity, and selective adsorption of MAA is achieved at 10-30°C.

[0036] In this invention, the main components of the MAA crude acid aqueous solution in step (a) are 20-60% methacrylic acid, 6-20% acetic acid, 0.5-5.0% propionic acid, 0.5-9.0% acrylic acid, 30-70% water, and 0.5-2.0% polymerization inhibitor.

[0037] In this invention, the extractant used in step (a) is an alkane or an ester. Preferably, the extractant is n-butyl acetate, isobutyl acetate, isopropyl acetate, heptane, or hexane.

[0038] The main components of solution A are a mixture of extractant and MAA.

[0039] The main components of solution B are 6-20% acetic acid, 0.3-1.0% MAA, 0.5-5.5% propionic acid, 0.5-5.5% acrylic acid, 0.5-2.0% polymerization inhibitor and 70-90% water.

[0040] In this invention, the temperature of the distillation column 2 in step (b) is controlled at 70~80℃, preferably 75~78℃. The solution C contains more than 99% extractant. However, due to incomplete separation, it still contains a small amount of impurities such as acetic acid, acrylic acid, and MAA, resulting in low purity of the extractant. The presence of MAA also reduces the mass transfer driving force of the extraction, leading to a decrease in extraction efficiency.

[0041] In this invention, the alkali in the alkaline solution in step (c) is selected from one or more of NaOH, Na2CO3, NaHCO3, KOH, and K2CO3, with NaOH and Na2CO3 being preferred; the concentration of the alkaline solution is controlled between 5 and 20 wt%, and the amount added is 1 to 5 wt% of solution C.

[0042] In this invention, step (c) involves letting the mixture stand in a settling tank for 30 to 90 minutes.

[0043] In this invention, in step (c), when the pH of the aqueous phase in the settling tank is less than 7, it is transferred to the acid precipitation tank 5. A certain concentration of sulfuric acid is added to the acid precipitation tank 5 to obtain a MAA mixture, denoted as solution D, which is then introduced into the extraction tower 1 and mixed with the original MAA crude acid aqueous solution. Preferably, the concentration of sulfuric acid used is 30~98wt%, more preferably 50~75wt%, and the mass ratio of sulfuric acid solution to alkali solution added is 1:5~1:20.

[0044] In this invention, in step (d), the adsorption space velocity is controlled at 1~10 BV / h, preferably 3~6 BV / h, and the adsorption temperature is preferably 15~25℃.

[0045] In this invention, the adsorbent is regenerated by washing with a regeneration solvent. The solvent flows through the adsorbent bed at a relatively slow flow rate and the temperature is increased to accelerate the desorption rate of organic matter in the pores. The desorption solution containing MAA is reused to recover MAA.

[0046] In this invention, the regenerated solvent is an alcohol or ester, preferably one or more of methanol, ethanol, isopropanol, methyl methacrylate, and butyl acetate. The desorption rate is controlled at 0.1~2 BV / h, preferably 0.5~1.0 BV / h, and the desorption temperature is controlled at 30~60℃, preferably 40~50℃.

[0047] Compared with the prior art, the implementation effects of the present invention are as follows:

[0048] (1) This invention synthesizes a surface-functionalized adsorbent that can selectively adsorb methacrylic acid. Compared with traditional adsorbents, the preparation process of the adsorbent is simple, highly controllable, can be prepared on a large scale, is green and environmentally friendly, and avoids the use of organic solvents. The monomers in the preparation process are widely selected. By adjusting the feed ratio and the amino density in the polyamine, the thickness, polarity, and charge of the polymer network can be controlled. The surface-modified polymer network is covalently linked and has good acid and alkali resistance and solvent resistance stability, which can achieve the separation of two or more substances with different polarities.

[0049] (2) The extractant recovered from the distillation section is purified by alkali neutralization, which improves the purity of the extractant and further improves the extraction efficiency, achieving zero loss of MAA products. The process conditions are mild, the separation efficiency is high, and the discharge of saline wastewater is greatly reduced. It is a greener, more environmentally friendly and sustainable process. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of an apparatus for treating wastewater from the production of methacrylic acid using adsorption resin, as shown in the example.

[0051] Figure 2 The image shows the nuclear magnetic resonance spectrum of the adsorbent synthesized in Example 1. Detailed Implementation

[0052] The technical solution of this patent will be clearly and completely described below with reference to examples. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0053] BET testing instrument: Tristar 3020 N: physical adsorption analyzer from Micron Instruments, USA;

[0054] Nuclear magnetic resonance testing instrument: Swiss Bruker AVANCE 400 nuclear magnetic resonance spectrometer;

[0055] Raw material source: MAA crude acid aqueous solution, whose main components are 32% methacrylic acid, 8% acetic acid, 0.8% propionic acid, 0.8% acrylic acid, 57.9% water and 0.5% polymerization inhibitor, etc.

[0056] Example 1

[0057] (1) Add 1000g of 5wt% sodium hydroxide to the reactor, along with 0.5g of ethylenediamine and 1.0g of 5-hydroxyp-naphthoquinone. Stir and control the reactor temperature at 25℃. After reacting for 5 hours, open the reactor.

[0058] (2) Immerse 20g of molecular sieve (4A molecular sieve, Jiangsu Xianfeng Nanomaterials Technology) with a particle size of 1μm in the above solution and shake it continuously in a constant temperature water bath shaker for about 10h at a water bath temperature of 25℃.

[0059] (3) The modified adsorbent microspheres were recovered by vacuum filtration and washed twice with deionized water, 500g each time. Then, they were dried at 120℃ for 4h to obtain adsorbent A1, as shown in the following schematic formula:

[0060]

[0061] Example 2

[0062] (1) Add 1000g of 3wt% sodium carbonate solution to the reactor, and add 1.2g of diethylenetriamine and 1.8g of 1,5-dihydroxyanthraquinone. Stir and control the reactor temperature at 38℃. After reacting for 10h, open the reactor.

[0063] (2) 12.5g of polystyrene microspheres (Zhongke Leiming Technology Co., Ltd.) with a particle size of 3μm were immersed in the above solution and continuously shaken in a constant temperature water bath shaker for about 12h at a water bath temperature of 40℃.

[0064] (3) The modified adsorbent microspheres were recovered by vacuum filtration and washed three times with deionized water, each time using 600g. Then they were dried at 100℃ for 4h to obtain adsorbent A2.

[0065] Example 3

[0066] (1) Add 1000g of 3.6wt% sodium hydroxide solution to the reactor, and add 0.8g of PEI with a molecular weight of 600g / mol and 0.8g of 5-hydroxy-p-naphthoquinone. Stir and control the reactor temperature at 40℃. After reacting for 8 hours, open the reactor.

[0067] (2) 16.7g of silica gel particles with a particle size of 5μm (Qingdao Xinchanglai Silica Gel Co., Ltd.) were immersed in the above solution and continuously shaken in a constant temperature water bath shaker for about 20h at a water bath temperature of 20℃.

[0068] (3) The modified adsorbent microspheres were recovered by vacuum filtration and washed with deionized water 6 times, each time with a dosage of 1000g. Then, they were dried at 80℃ for 4h to obtain adsorbent A3.

[0069] Example 4

[0070] (1) Add 1000g of 10wt% potassium hydroxide to the reactor, along with 2.0g of PEI with a molecular weight of 1800 and 10g of 5,8-dihydroxy-1,4-naphthoquinone. Stir and control the reactor temperature at 20℃. After reacting for 16h, open the reactor.

[0071] (2) 100g of polystyrene microspheres (Zhongke Leiming Technology Co., Ltd.) with a particle size of 0.1μm were immersed in the above solution and continuously shaken in a constant temperature water bath shaker for about 24h at a water bath temperature of 30℃.

[0072] (3) The modified adsorbent microspheres were recovered by vacuum filtration and washed with deionized water 8 times, each time with a dosage of 100g. Then, they were dried at 120℃ for 4h to obtain adsorbent A4.

[0073] Example 5

[0074] (1) Add 1000g of 1.0wt% sodium carbonate to the reactor, and add 0.1g of PEI with a molecular weight of 70000 and 0.05g of 5,8-dihydroxy-1,4-naphthoquinone. Stir and control the reactor temperature at 50℃. After reacting for 4 hours, open the reactor.

[0075] (2) 33.3g of polyacrylamide microspheres with a particle size of 10μm (Shandong Zhizhuo Chemical Co., Ltd.) were immersed in the above solution and continuously shaken in a constant temperature water bath shaker for about 10h at a water bath temperature of 25℃.

[0076] (3) The modified adsorbent microspheres were recovered by vacuum filtration and washed 10 times with deionized water, each time using 200g. Then they were dried at 100℃ for 4h to obtain adsorbent A5.

[0077] Example 6

[0078] MAA crude acid aqueous solution enters from the top of the extraction column at a flow rate of 10 t / h, and heptane extractant enters from the bottom of the column at a flow rate of 10 t / h. The countercurrent extraction process is adopted. The oil phase solution A at the top of the column enters the next step of the distillation column for purification. The distillation column has 10 theoretical plates, a negative pressure of 20 kPa, and the bottom temperature is controlled at 78℃. Solution A is fed from the 5th plate. The top solution C is heptane with a purity of more than 99%, and the bottom solution is MAA with a purity of 99.9%, which enters the next step of separation.

[0079] Solution C is transferred to the reactor, and 100 kg / h of 5 wt% NaOH solution is added to the reactor. The mixture is stirred at room temperature to form an emulsion to neutralize the residual MAA in the extractant. The neutralized emulsion is then transferred to a settling tank for phase separation. After settling for 30 minutes, the upper oil phase is circulated to the extraction tower, and the aqueous phase is circulated back to the reactor. The pH in the settling tank is controlled at around 7. When the pH of the solution in the settling tank is ≤7, the aqueous phase is transferred to an acid precipitation tank, and 30 wt% sulfuric acid solution is added to the acid precipitation tank at a rate of 20 kg / h to obtain a mixed MAA solution D. Solution D is then transferred to extraction tower 1 for reuse.

[0080] The bottom solution B from the extraction tower enters the adsorption tank, which is then filled with 13.3 mL of adsorbent A from Example 1. 3 The adsorption was carried out at 25℃ for 24 hours. Methanol was used as the adsorbent for desorption. The methanol feed flow rate was 0.5 BV / h, and the desorption temperature was controlled at 30℃. The desorption was carried out until the MAA content at the outlet was less than 50 ppm. Based on the MAA content at the inlet and outlet of the adsorption tank, the MAA recovery rate was calculated to be 96%.

[0081] Example 7

[0082] MAA crude acid aqueous solution enters from the top of the extraction column at a flow rate of 10 t / h, and n-butyl acetate extractant enters from the bottom of the column at a flow rate of 10 t / h. The countercurrent extraction process is adopted. The oil phase solution A at the top of the column enters the next step of the distillation column for purification. The distillation column has 10 theoretical plates, a negative pressure of 20 kPa, and the bottom temperature is controlled at 80℃. Solution A is fed from the 5th plate. The top solution C is n-butyl acetate with a purity of more than 99%, and the bottom solution is MAA with a purity of 99.9%, which enters the next step of separation.

[0083] Solution C is transferred to the reactor, and 200 kg / h of 10 wt% Na2CO3 solution is added. The mixture is stirred at room temperature to form an emulsion to neutralize the residual MAA in the extractant. The neutralized emulsion is then transferred to a settling tank for phase separation. After settling for 30 minutes, the upper oil phase is circulated to the extraction tower, and the aqueous phase is circulated back to the reactor. The pH in the settling tank is controlled at around 7. When the pH of the solution in the settling tank is ≤ 7, the aqueous phase is transferred to an acid precipitation tank, and 20 kg / h of 50 wt% sulfuric acid solution is added to the acid precipitation tank to obtain MAA mixed solution D. Solution D is then transferred to extraction tower 1 for reuse.

[0084] The bottom solution B from the extraction tower enters the adsorption tank, which is then filled with 22.0 mL of adsorbent A from Example 2. 3 The adsorption was carried out at 20℃ for 24 hours. Methanol was used as the adsorbent for desorption. The methanol feed flow rate was 0.5 BV / h, and the desorption temperature was controlled at 30℃. The desorption was carried out until the MAA content at the outlet was less than 50 ppm. Based on the MAA content at the inlet and outlet of the adsorption tank, the MAA recovery rate was calculated to be 98%.

[0085] Example 8

[0086] MAA crude acid aqueous solution enters from the top of the extraction column at a flow rate of 10 t / h, and isopropyl acetate extractant enters from the bottom of the column at a flow rate of 10 t / h. Countercurrent extraction is adopted. The oil phase solution A at the top of the column enters the next step of the distillation column for purification. The distillation column has 10 theoretical plates, a negative pressure of 60 kPa, and the bottom temperature is controlled at 77℃. Solution A is fed from the 5th plate. The top solution C is isopropyl acetate with a purity of more than 99%, and the bottom solution is MAA with a purity of 99.9%, which enters the next step of separation.

[0087] Solution C is transferred to the reactor, and 500 kg / h of 20 wt% NaHCO3 solution is added. The mixture is stirred at room temperature to form an emulsion to neutralize the residual MAA in the extractant. The neutralized emulsion is then transferred to a settling tank for phase separation. After settling for 30 minutes, the upper oil phase is circulated to the extraction tower, and the aqueous phase is circulated back to the reactor. The pH in the settling tank is controlled at around 7. When the pH of the solution in the settling tank is ≤ 7, the aqueous phase is transferred to an acid precipitation tank, and 68 wt% sulfuric acid solution is added at a rate of 62.5 kg / h to obtain MAA mixed solution D. Solution D is then transferred to extraction tower 1 for reuse.

[0088] The bottom solution B from the extraction tower enters the adsorption tank, which is then filled with 31.25 ml of adsorbent A from Example 3. 3 The adsorption was performed at 15℃ for 24 hours. Methanol was used as the adsorbent for desorption. The methanol feed flow rate was 0.5 BV / h, and the desorption temperature was controlled at 30℃. The desorption was carried out until the MAA content at the outlet was less than 50 ppm. Based on the MAA content at the inlet and outlet of the adsorption tank, the MAA recovery rate was calculated to be 97%.

[0089] Example 9

[0090] MAA crude acid aqueous solution enters from the top of the extraction column at a flow rate of 10 t / h, and n-hexane, the extractant, enters from the bottom of the column at a flow rate of 10 t / h. A countercurrent extraction process is adopted. The oil phase solution A at the top of the column enters the next step of the distillation column for purification. The distillation column has 10 theoretical plates, a negative pressure of 80 kPa, and the bottom temperature is controlled at 70℃. Solution A is fed from the 5th plate. The top solution C is n-hexane with a purity of more than 99%, and the bottom solution is MAA with a purity of 99.9%, which enters the next step of separation.

[0091] Solution C is transferred to the reactor, and 100 kg / h of 15 wt% Na2CO3 solution is added to the reactor. The mixture is stirred at room temperature to form an emulsion to neutralize the residual MAA in the extractant. The neutralized emulsion is then transferred to a settling tank for phase separation. After settling for 30 minutes, the upper oil phase is circulated to the extraction tower, and the aqueous phase is circulated back to the reactor. The pH in the settling tank is controlled at around 7. When the pH of the solution in the settling tank is ≤7, the aqueous phase is transferred to an acid precipitation tank, and 75 wt% sulfuric acid solution is added to the acid precipitation tank at a rate of 6.7 kg / h to obtain MAA mixed solution D. Solution D is then transferred to extraction tower 1 for reuse.

[0092] The bottom solution B from the extraction tower enters the adsorption tank, which is then filled with 41.67 mL of adsorbent A from Example 4. 3 The adsorption was performed at 20℃ for 24 hours. After the adsorption was completed, ethanol was used for desorption. The ethanol feed flow rate was 0.5 BV / h, and the desorption temperature was controlled at 30℃. The desorption was carried out until the MAA content at the outlet was less than 50 ppm. Based on the MAA content at the inlet and outlet of the adsorption tank, the MAA recovery rate was calculated to be 95%.

[0093] Example 10

[0094] MAA crude acid aqueous solution enters from the top of the extraction column at a flow rate of 10 t / h, and isobutyl acetate extractant enters from the bottom of the column at a flow rate of 10 t / h. The countercurrent extraction process is adopted. The oil phase solution A at the top of the column enters the next step of the distillation column for purification. The distillation column has 10 theoretical plates, a negative pressure of 25 kPa, and the bottom temperature is controlled at 75℃. Solution A is fed from the 5th plate. The top solution C is n-hexane with a purity of more than 99%, and the bottom solution is MAA with a purity of 99.9%, which enters the next step of separation.

[0095] Solution C is transferred to the reactor, and 500 kg / h of 10 wt% KOH solution is added. The mixture is stirred at room temperature to form an emulsion to neutralize the residual MAA in the extractant. The neutralized emulsion is then transferred to a settling tank for phase separation. After settling for 30 minutes, the upper oil phase is circulated to the extraction tower, and the aqueous phase is circulated back to the reactor. The pH in the settling tank is controlled at around 7. When the pH of the solution in the settling tank is ≤7, the aqueous phase is transferred to an acid precipitation tank, and 50 wt% sulfuric acid solution is added at a rate of 41.7 kg / h to obtain MAA mixed solution D. Solution D is then transferred to extraction tower 1 for reuse.

[0096] The bottom solution B from the extraction tower enters the adsorption tank, which is then filled with 51.00 ml of adsorbent A from Example 5. 3 The adsorption was carried out at 23℃ for 24 hours. After the adsorption was completed, n-butyl acetate was used for desorption. The feed flow rate was 0.5 BV / h, and the desorption temperature was controlled at 30℃. The desorption was carried out until the MAA content at the outlet was less than 50 ppm. Based on the MAA content at the inlet and outlet of the adsorption tank, the MAA recovery rate was calculated to be 91%.

[0097] The specific results of Examples 6-10 are shown in Table 1.

[0098] Table 1. Specific Implementation Results of Examples 6-10

[0099]

[0100] Comparative Example 1

[0101] Untreated commercial molecular sieves (4A molecular sieve, Jiangsu Xianfeng Nanomaterials Technology) were selected as adsorbents, and other process conditions were the same as in Example 6. The composition of the inlet and outlet of the adsorption tank was analyzed.

[0102] Comparative Example 2

[0103] 20g of commercial molecular sieve (4A molecular sieve, particle size 1μm, Jiangsu Xianfeng Nanomaterials Technology) was selected as the adsorbent matrix. 1000g of 5wt% sodium hydroxide, 0.5g of aniline and 1.0g of 1,4-naphthoquinone were added to the reactor. The mixture was stirred and the reactor temperature was controlled at 25℃ to allow for a full reaction. After 5 hours of reaction, the reactor was opened. Other adsorbent preparation conditions were the same as in Example 1. The process conditions are shown in Example 6. The composition of the inlet and outlet of the adsorption tank was analyzed.

[0104] Table 2 Comparative results

[0105]

[0106] Based on Examples 6, 1, and 2, the commercial molecular sieve without any treatment exhibited the worst adsorption effect for MAA. This is because its surface lacks functional group modification, allowing a large amount of impurities such as acetic acid and acrylic acid to enter the pores during adsorption, resulting in fewer MAA adsorption sites. In addition, in Comparative Example 2, the conjugation effect of aniline weakens the electron density of the N atom surface, reducing its basicity and making the reaction effect less effective than that of ethylenediamine and 5-hydroxynaphthoquinone. Furthermore, 1,4-naphthoquinone has poor solubility, lacks hydroxyl groups, and cannot form a covalent network on the adsorbent surface. It can only exist as a monomer on the adsorbent surface, which may lead to uneven coverage. Therefore, its selective adsorption effect for MAA is poor.

Claims

1. A method for preparing an adsorbent, comprising the following steps: (1) Dissolve polyamine and hydroxyquinone in an alkaline aqueous solution to form an adsorbent coating solution. Immerse microspheres in the adsorbent coating solution and keep them at 20~40℃ for 10~24h. (2) Separation, washing, and drying; The polyamine is one or more of ethylenediamine, diethylenetriamine, triethylenediamine, tetraethylenepentamine, and polyethyleneimine with a weight-average molecular weight of 600, 1800, 10000, or 70000 g / mol. The hydroxyquinone is one or more of 5-hydroxy-p-naphthoquinone, 5,8-dihydroxy-1,4-naphthoquinone, and 1,5-dihydroxyanthraquinone.

2. The method according to claim 1, characterized in that, The alkaline aqueous solution is selected from one or more of KOH, NaOH, and Na2CO3; the concentration of the alkaline aqueous solution is 1~10wt%.

3. The method according to claim 1, characterized in that, The mass ratio of the hydroxyquinone to the polyamine is 5:1 to 1:

5.

4. The method according to claim 1, characterized in that, The mass ratio of the hydroxyquinone to the polyamine is 2:1 to 1:

2.

5. The method according to claim 1, characterized in that, The microspheres are selected from one or more of molecular sieves, silica gel particles, polyacrylamide microspheres, and polystyrene microspheres, and the average particle size of the microspheres is 0.1~10μm.

6. The method according to claim 1, characterized in that, The average particle size of the microspheres is 1~5μm.

7. The method according to claim 1, characterized in that, The mass ratio of the microspheres to the alkaline aqueous solution is 1:10 to 1:

100.

8. The method according to claim 1, characterized in that, The mass ratio of the microspheres to the alkaline aqueous solution is 1:50 to 1:

80.

9. The method according to claim 1, characterized in that, The specific surface area of ​​the adsorbent is 1000-1980 m². 2 / g, pore volume of 2.1~3.15dm 3 / g.

10. A treatment device for MAA wastewater, comprising an extraction tower (1), a distillation tower (2), a reaction vessel (3), a settling tank (4), an acid precipitation tank (5), and an adsorption tank (6); the upper part of the extraction tower (1) is provided with a feed pipeline (8) for MAA crude acid aqueous solution, the top of the extraction tower is connected to the distillation tower (2) through a liquid phase pipeline (9), the bottom of the extraction tower (1) is connected to the adsorption tank (6) through a liquid phase pipeline (10), the top reflux tank (7) of the distillation tower (2) is connected to the reaction vessel (3) through a liquid phase pipeline (11), and the lower part of the reaction vessel (3) is provided with a discharge pipe (13) and a settling tank. (4) Connection: An oil phase discharge pipeline (14) is set at the upper part of the oil-water separation interface of the settling tank (4) and connected to the lower part of the extraction tower (1). An aqueous phase discharge pipeline (15) is set at the lower part of the settling tank (4) and connected to the acid precipitation tank (5) and the reaction vessel (3). The acid precipitation tank (5) is connected to the MAA crude acid aqueous solution feed pipeline (8) through the liquid phase pipeline (16). A sulfuric acid feed pipe (18) is set at the top of the acid precipitation tank (5), and an alkaline feed port (17) is set at the top of the reaction vessel (3). The adsorption tank (6) is filled with the adsorbent prepared by the method described in any one of claims 1-9.

11. A MAA wastewater treatment process, comprising the following steps: The apparatus according to claim 10, (a) The crude acid aqueous solution of MAA enters the extraction tower (1), the extract is obtained at the top of the tower, which is denoted as solution A, and the raffinate obtained at the bottom of the tower is wastewater, which is denoted as solution B; (b) Solution A enters distillation column (2), the extractant is obtained at the top of the column, denoted as solution C, and MAA is obtained at the bottom of the column; (c) Solution C and alkaline solution enter the reactor (3), and are stirred to form an emulsion. The neutralized emulsion enters the settling tank (4) for phase separation. The oil phase is circulated to the extraction tower (1), and the aqueous phase is circulated to the reactor (3). (d) Solution B passes through the adsorption tank (6) at a certain space velocity and performs selective adsorption of MAA at 10-30℃.

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