A polymerization inhibitor adsorbent for removing acrylic acid

Abstract

The application provides an adsorbent for removing an inhibitor in acrylic acid, relates to the chemical industry, and is characterized in that bentonite is modified by using an acrylic acid-acrylamide-styrene-hydroxypropyl acrylate quaternary copolymer, the adsorption performance of the bentonite is improved, the bentonite can replace activated carbon in the prior art, the cost is low, the bentonite can be regenerated and reused, the production cost of enterprises is greatly reduced, and the application has good significance for energy saving and environmental protection.

Description

[0001] This application is a divisional application of the application date: 20220323, the application number: 202210290035.8, the invention name: a method for replacing activated carbon adsorption to remove the inhibitor in acrylic acid and adsorbent, the applicant: Jiangmen Xinhui District Zhongsheng Biotechnology Co., Ltd. TECHNICAL FIELD

[0002] The present application relates to the technical field of chemical industry, in particular to a method for replacing activated carbon adsorption to remove the inhibitor in acrylic acid and an adsorbent. BACKGROUND

[0003] It has always been a hot topic on how to remove the inhibitor in acrylic acid monomer to obtain high-performance polyacrylic acid products. The methods for removing the inhibitor include: vacuum distillation, low-temperature recrystallization, ion exchange resin, molecular sieve or activated carbon adsorption separation. The vacuum distillation and low-temperature recrystallization require expensive equipment, high investment, high energy consumption and high cost, and only large factories can consider using them. Moreover, the tail liquid (acrylic acid liquid with high inhibitor content) prepared by distillation method needs further treatment. Although the ion exchange resin method is simple, the treatment capacity is not large, and the regeneration of the resin is difficult and costly. Therefore, most small and medium-sized factories currently use activated carbon adsorption method to remove the inhibitor in acrylic acid. With the increasing environmental protection requirements, the waste residue of activated carbon in the factory is strictly controlled. In addition to the fact that the waste residue of activated carbon must be treated by the relevant departments, the amount of activated carbon waste residue produced by the factory is also strictly controlled, and the amount of waste residue produced is not allowed to exceed the standard, which brings certain difficulties to the factory. SUMMARY

[0004] The present application aims to solve the problem of excessive activated carbon waste residue in the prior art, and the new mineral adsorbent can be regenerated and treated by itself, reducing the cost and secondary pollution.

[0005] To achieve the above-mentioned purpose, the present application provides the following scheme: the present application provides a method for preparing an adsorbent for replacing activated carbon adsorption to remove the inhibitor in acrylic acid:

[0006] S1. Dry bentonite for standby;

[0007] S2. Dissolve acrylic acid-acrylamide-styrene-hydroxypropyl acrylate tetrapolymer in water to prepare a 2-5% aqueous solution;

[0008] S3. Mix the bentonite in S1 and the solution in S2 according to the mass ratio of 1:1, stir uniformly to form mud, and place at a temperature of 25-35℃ for 48 hours;

[0009] S4. The slurry in S3 is dried in an oven and crushed to obtain the adsorbent product.

[0010] As a preferred embodiment of the present application, the preparation method of the acrylic acid-acrylamide-styrene-hydroxypropyl acrylate tetrapolymer, the mass ratio of the four is 4:3:1:1, first, the acrylic acid and acrylamide are dissolved in pure water to form an aqueous phase solution; then, the styrene is dissolved in hydroxypropyl acrylate to form an oil phase solution; then, the oil phase solution is added dropwise into the aqueous phase solution, and the stirring is carried out rapidly during the dropwise adding, so that the uniform emulsion is formed. Then, 0.5% to 0.8% of the monomer initiator potassium persulfate and 0.2% to 0.4% of sodium sulfite are added, and the reaction is carried out at 25 to 30°C for 4 to 6 hours, so that the gel product is obtained, and then the granulation-drying-crushing-screening are carried out.

[0011] As a preferred embodiment of the present application, the bentonite is screened to 200 meshes in step S1.

[0012] The present application also provides the adsorbent prepared by the above method.

[0013] The present application has the following beneficial effects compared with the prior art:

[0014] It can not only solve the problem of exceeding the standard of the waste residue of activated carbon, but also solve the problem of removing the polymerization inhibitor in the acrylic acid, and the new mineral adsorbent can be treated by regeneration, so that the cost is reduced and the secondary pollution is reduced.

[0015] The key of the present application is the modification treatment of the bentonite. As known, the bentonite is mainly montmorillonite mineral structure, Na 0.7 (Al 3.3 ˙Mg 0.7 )Si8O2(0H)4˙nH2O, the crystal structure presents upper and lower two layers of Si-O tetrahedron, and a middle layer of Al-O octahedron, so it has a large specific surface, good adsorption, volume expansion, ion exchange and adhesion. The acrylic acid-acrylamide-styrene-hydroxypropyl acrylate tetrapolymer is a good adsorbent, and has good adsorption effect on various metal ions and some organic matters. When the two are mixed, it is easy to adhere to the surface of the bentonite, so that the bentonite is modified, and the adsorption performance is greatly improved. In addition, there is a slit between the upper and lower two layers of Si-O tetrahedron, if the slit is enlarged, the adsorption capacity will be further improved, therefore, the cationic surfactant such as cetyltrimethylammonium bromide or octadecyltrimethylammonium chloride can be added during the treatment of the bentonite, so as to replace Na+ in the slit and enlarge the slit, and further improve the adsorption performance.

[0016] The method and adsorbent for removing the polymerization inhibitor in acrylic acid by replacing activated carbon adsorption can completely replace the activated carbon in the prior art, has low cost, and can be regenerated and continuously used, greatly reduces the production cost of enterprises, and has good popularization significance for energy saving and environmental protection. DETAILED DESCRIPTION

[0017] The application provides a preparation method of an adsorbent for removing a polymerization inhibitor in acrylic acid by replacing activated carbon adsorption.

[0018] S1. The bentonite is dried for standby;

[0019] S2. The acrylic acid-acrylamide-styrene-hydroxypropyl acrylate quaternary copolymer is dissolved in water to prepare a 2-5% concentration aqueous solution;

[0020] S3. The bentonite in S1 and the solution in S2 are mixed in a mass ratio of 1:1, uniformly stirred into mud, and placed at a temperature of 25-35 DEG C for 48 hours;

[0021] S4. The mud in S3 is dried in an oven and crushed to obtain the finished adsorbent.

[0022] The preparation method of the acrylic acid-acrylamide-styrene-hydroxypropyl acrylate quaternary copolymer is as follows: the mass ratio of the four is 4:3:1:1, acrylic acid and acrylamide are first added to pure water to dissolve into an aqueous phase solution; styrene is added to hydroxypropyl acrylate to dissolve into an oil phase solution; then the oil phase solution is slowly added dropwise into the aqueous phase solution, and stirring is performed rapidly during the dropwise addition, so that a uniform emulsion is formed. Then, 0.5%-0.8% of monomer initiator potassium persulfate and 0.2%-0.4% of sodium sulfite are added, and the reaction is performed at 25-30 DEG C for 4-6 hours to obtain a gel product, which is then cut, dried, crushed and sieved.

[0023] As a preferred embodiment of the application, cationic surfactants such as hexadecyl ammonium bromide or octadecyl trimethyl ammonium chloride are further added in step S1.

[0024] In order to make the above-mentioned objects, characteristics and advantages of the application more obvious and easy to understand, the application will be further described in detail below with reference to the specific embodiments.

[0025] Example 1

[0026] Synthesis of the tetra-copolymer: 15 g of acrylamide was added to 30 g of pure water and dissolved, then 20 g of acrylic acid was added to make an aqueous solution; 5 g of styrene and 5 g of hydroxypropyl acrylate were weighed and made into an oil phase solution. Under stirring, the oil phase solution was slowly added to the aqueous solution, and after the dropwise addition was completed, stirring was continued for 30 minutes to make a uniform solution, then 0.18 g of potassium persulfate and 0.10 g of sodium sulfite were added, and the reaction was carried out at 30°C for 4 hours to obtain the tetra-copolymer. After granulation, drying at 105°C, and pulverization, the powder was passed through a 200 mesh screen and used as needed.

[0027] Preparation of the adsorbent: commercially available Na-bentonite was passed through a 200 mesh screen and dried in an oven at 105°C until the weight was constant. The above-mentioned tetra-copolymer was made into a 4% aqueous solution, and was added to the dried bentonite at a weight ratio of 1:1, and stirred to make a slurry. The slurry was left to stand at 30°C for 48 hours, and then was dried in an oven at 105°C to make a powder.

[0028] Adsorption of the polymerization inhibitor MEHQ (4-methoxyphenol): the adsorbent used was basic acrylic acid, which was neutralized with NaOH to a degree of 90%. The amount of adsorbent added was 5‰ (based on the total amount of sodium acrylate), and the mixture was left to stand and stir for 8 hours, then was filtered. The amount of MEHQ in the filtrate was determined by spectrophotometry, and was converted to a concentration in PPM. In addition, the sodium acrylate treated by adsorption was used as a raw material to polymerize a thickening agent according to a predetermined formulation, and was made into a 2‰ aqueous solution. The viscosity of the solution was measured using a rotary viscometer, Model NDJ-1, and the normal required viscosity was 800 mpa-s or more. The data obtained are shown in the table.

[0029] Example 2

[0030] Example 3

[0031] Example 3

[0032] Example 3

[0033] The data before and after adsorption in the above examples are as follows:

[0034]

[0035]

[0036] The determination of the content of the polymerization inhibitor MEHQ is based on the method specified in "GB / T 17530.5-1998, Determination of polymerization inhibitor in industrial propylene acid and ester", and the content of the determined MEHQ in μg is converted into ppm content.

[0037] From the above data, it can be seen that the three adsorbents of the present application have reached the level of activated carbon adsorption in the adsorption of the polymerization inhibitor from the basic sodium propylene acid solution, and can be used to replace activated carbon.

[0038] Regeneration of the adsorbent: the used adsorbent of the present application has sodium propylene acid and MEHQ attached to its surface, and can be washed or soaked twice with a low concentration lye such as a 15% NaOH aqueous solution, and then washed once with tap water and pure water, and then dried in an oven at 105°C, and then prepared into a modified adsorbent by adding a quaternary copolymer aqueous solution according to the method for preparing the adsorbent of the present application, and then used for the next adsorption of the polymerization inhibitor, and so on, which can be used for 3-4 times. Although the MEHQ removal capacity of the regenerated adsorbent decreases slightly each time, the decrease is small, and the effective rate of the polymerization inhibitor removal of the regenerated adsorbent at the last time can still reach 70%-80% of the original level.

[0039] The principles and implementation modes of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the present application and its core ideas; meanwhile, for those skilled in the art, the specific implementation modes and application ranges can be changed according to the ideas of the present application. In conclusion, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. An adsorbent for removing the polymerization inhibitor MEHQ from acrylic acid, characterized in that it comprises a mixture of a macroporous polymer and a microporous polymer. The following steps are adopted to make the product: S1. Take bentonite and dry for standby; S2. Dissolve acrylic acid-acrylamide-styrene-hydroxypropyl acrylate quaternary copolymer in water to form a 2-5% aqueous solution; the preparation method of acrylic acid-acrylamide-styrene-hydroxypropyl acrylate quaternary copolymer is as follows: first, dissolve acrylic acid and acrylamide in pure water to form an aqueous solution; then, dissolve styrene in hydroxypropyl acrylate to form an oil solution; then, drop the oil solution into the aqueous solution while stirring rapidly to form a uniform emulsion; then, add 0.5%-0.8% initiator potassium persulfate and 0.2%-0.4% sodium sulfite by mass, and react at 25-30°C for 4-6 hours to obtain a gel product, which is then cut, dried, crushed, and sieved; the mass ratio of acrylic acid-acrylamide-styrene-hydroxypropyl acrylate is 4:3:1:1; S3. Mix the bentonite in S1 and the aqueous solution in S2, and stir them evenly to form a mud, with a mass ratio of 1:1, and then place them for 48 hours; S4. Dry the mud in S3 in an oven and crush it to obtain the finished product of the adsorbent.

2. The adsorbent according to claim 1, characterized in that The bentonite in step S1 is sieved to 200 mesh.

3. The adsorbent of claim 1, wherein, Step S1 also includes adding a cationic surfactant to the bentonite.

4. The adsorbent of claim 3, wherein, The cationic surfactant is one or both of cetyltrimethylammonium bromide and octadecyltrimethylammonium chloride.

Images