Clean recovery process of glyphosate acid byproduct chloromethane

Abstract

The invention discloses a clean recovery process of glyphosate acid byproduct chloromethane, and belongs to the technical field of chemical engineering. The clean recovery process for the glyphosate acid byproduct chloromethane comprises the following specific steps: step A1, washing the glyphosate acid synthesis byproduct with water, and then drying; a2, the dried tail gas is introduced into a compression condensation system through a compressor, chloromethane in the tail gas is liquefied and recycled through a compression and three-stage condensation method, and liquefied chloromethane and condensed tail gas containing trace chloromethane are obtained; step A3, introducing the condensed tail gas into an adsorption tower filled with a magnetic impurity removal component, and adsorbing to obtain chloromethane; and A4, returning chloromethane obtained after adsorption to the inlet of the compressor, and repeating the step A2 and the step A3 together with the dried tail gas. The chloromethane recovery rate obtained through recovery is high, and the recovery process is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a clean recovery process of chloromethane produced as a by-product of glyphosate. Background Art

[0002] Glyphosate is a highly effective, broad-spectrum, non-selective, and residue-free post-emergence herbicide. It has become the world's largest-selling and fastest-growing pesticide. Glyphosate acid is typically synthesized using the alkyl phosphite process, which uses phosphite diesters or triesters as starting materials. This production process produces a large amount of chloromethane-containing tail gas. After recovery and purification, the chloromethane can be used in the production of products such as carboxymethyl cellulose and chloroprene rubber, offering broad application prospects.

[0003] Patent publication number CN 106966857B discloses a method for recovering methyl chloride from glyphosate synthesis tail gas. The method comprises the following steps: A) washing the glyphosate synthesis tail gas with water, alkali, and drying; B) recovering the methyl chloride from the tail gas by liquefaction using compression followed by three-stage condensation; C) introducing the condensed tail gas into a pressure swing adsorption system consisting of an adsorption tower filled with a solid adsorbent, separating and enriching the trace methyl chloride through adsorption, and then releasing a product gas rich in methyl chloride through desorption; and D) returning the product gas to the compressor inlet and repeating steps B and C with the dried tail gas. However, the recovery rate of methyl chloride recovered in this patent and prior art is low. Summary of the Invention

[0004] In order to solve the problem of low recovery rate of chloromethane in the prior art, the present invention provides a clean recovery process for chloromethane produced as a by-product of glyphosate acid.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A clean recovery process for glyphosate acid by-product chloromethane comprises the following steps:

[0007] Step A1: washing the glyphosate synthesis by-product with water and then drying;

[0008] Step A2: The tail gas dried in step A1 is introduced into a compression condensation system via a compressor, and compression plus three-stage condensation is adopted to liquefy and recover the chloromethane in the tail gas to obtain liquefied chloromethane and condensed tail gas containing trace amounts of chloromethane;

[0009] Step A3: introducing the condensed tail gas in step A2 into an adsorption tower filled with a magnetic impurity removal component to obtain chloromethane after adsorption;

[0010] Step A4: Return the chloromethane in step A3 to the compressor inlet in step A2, and repeat steps A2 and A3 together with the dried tail gas.

[0011] In the above steps, in view of the extremely low solubility of methyl chloride in water, this method adopts water washing process to remove byproducts such as part methylal, methyl alcohol and hydrogen chloride that produce in the glyphosate acid building-up process. Subsequently, the moisture in the glyphosate acid synthetic byproduct is removed by a drying step. Because the solubility of methyl chloride in water is low, it is possible to effectively separate with above-mentioned impurity realization. But because the solubility of methylal and part impurity in water is limited, in the glyphosate acid synthetic byproduct after washing, still there is methylal and trace carbonic acid gas, and now, can reach the purpose of adsorbing methylal and carbonic acid gas by being filled with the adsorption tower of magnetic impurity removal component.

[0012] Furthermore, the by-products of glyphosate acid synthesis contain 60-70% methyl chloride, 10-20% methylal, 8-20% air, 1-5% hydrogen chloride, 1-5% methanol, and 1-2% water.

[0013] Furthermore, in step A1, the glyphosate acid synthesis by-product is pressurized to 25-35 KPaG and then washed with water.

[0014] Furthermore, the drying in step A1 uses concentrated sulfuric acid as an absorbent for dehydration and drying.

[0015] Furthermore, in step A2, the three-stage condensation method uses circulating water for the first stage condensation, -15°C brine for the second stage condensation, and -35°C R22 direct evaporation condensation for the third stage condensation; the gas pressure in the compression condensation system is 0.8-1.2 MPaG.

[0016] Furthermore, in step A3, the temperature of the adsorption tower is 10-20° C., and the pressure is 0.1-0.4 MPaG.

[0017] Further, the magnetic impurity removal component is prepared by the following steps:

[0018] Methylal, methacrylic acid and methacrylamide are dissolved in anhydrous ethanol and prepolymerized at 25°C for 30 minutes to form a prepolymer solution; a magnetic fluid aqueous solution is added to the prepolymer solution, and then ethylene glycol dimethyl acrylate and 2,2-azobisisobutyronitrile are added under stirring at 800 r / min, and heated at 60°C for 24 hours under N2 protection; after separation in an external magnetic field, the template molecule methylal is eluted with mixed solution b, and then washed with ultrapure water until neutral, and vacuum dried at 60°C for 24 hours to obtain a magnetic impurity removal component.

[0019] In the above steps, methacrylic acid and methacrylamide are used as functional monomers, and methylal is used as a template molecule. The two are combined and dissolved in anhydrous ethanol to prepare a prepolymer solution. Then, under the action of the initiator 2,2-azobisisobutyronitrile, the prepolymer solution is polymerized with a magnetic fluid aqueous solution and ethylene glycol dimethyl acrylate. Finally, the methylal template molecule is eluted and dried to obtain a magnetic impurity removal component. The magnetic impurity removal component forms a hole that is exactly the same shape and size as the methylal molecule and can be specifically identified, which can specifically identify and adsorb the methylal molecule. The functional monomer contains methacrylamide, so that the final prepared magnetic impurity removal component contains an amino group. The amino group has a weak chemical reaction with carbon dioxide, so that the magnetic impurity removal component can adsorb carbon dioxide, further improving the purity of chloromethane.

[0020] The dosage ratio of methylal, methacrylic acid, methacrylamide and anhydrous ethanol is 0.1 g: 0.8-1 g: 0.4-0.6 g: 10 mL; the dosage ratio of prepolymer solution, magnetic fluid aqueous solution, ethylene glycol dimethyl acrylate and 2,2-azobisisobutyronitrile is 10 mL: 10 mL: 2.8-3.4 g: 0.1 g; and the mixed solution b is composed of methanol and acetic acid, and the volume ratio of methanol to acetic acid is 9:1.

[0021] Furthermore, the magnetic fluid aqueous solution is prepared by the following steps:

[0022] Step B1: Add ferric chloride hexahydrate and anhydrous sodium acetate to ethylene glycol, stir at 40°C for 15 minutes to obtain a mixture C, transfer the mixture C to an autoclave, and crystallize at 180°C for 24 hours. After the crystallization, perform magnetic separation, wash with anhydrous ethanol and deionized water three times each, and dry at 80°C for 18 hours to obtain Fe3O4 nanoparticles.

[0023] Among them, the usage ratio of ferric chloride hexahydrate, anhydrous sodium acetate and ethylene glycol is 20g:40g:1L.

[0024] Step B2: Fe3O4 nanoparticles were dispersed in ultrapure water, dispersed at 60°C for 5 minutes, oleic acid was added, and after ultrasonication for 10 minutes, dispersant sodium dodecyl sulfate was added to obtain a magnetic fluid aqueous solution.

[0025] The usage ratio of Fe3O4 nanoparticles, ultrapure water, oleic acid, and sodium lauryl sulfate is 1 g: 100 mL: 700 μL: 670 mg.

[0026] Beneficial effects of the present invention:

[0027] 1. The present invention improves the recovery rate of chloromethane by performing a series of treatments on the by-product of glyphosate acid synthesis through water washing, drying, compression condensation, and an adsorption tower filled with a magnetic impurity removal component, thereby obtaining chloromethane with higher purity.

[0028] 2. The present invention adopts an adsorption tower filled with a magnetic impurity removal component. The magnetic impurity removal component can be regenerated after adsorption saturation to achieve recycling and reduce the overall processing cost. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] The glyphosate synthesis by-product contains 60-70% methyl chloride, 10-20% methylal, 8-20% air, 1-5% hydrogen chloride, 1-5% methanol and 1-2% water.

[0031] Example 1

[0032] The preparation steps of the magnetic fluid aqueous solution of this embodiment are:

[0033] Step B1: 20 g of ferric chloride hexahydrate and 40 g of anhydrous sodium acetate were added to 1 L of ethylene glycol and stirred at 40°C for 15 minutes to obtain a mixed solution c. The mixed solution c was transferred to an autoclave and crystallized at 180°C for 24 hours. After the crystallization, the mixture was magnetically separated, washed with anhydrous ethanol and deionized water three times each, and dried at 80°C for 18 hours to obtain Fe3O4 nanoparticles.

[0034] Step B2: 1 g of Fe3O4 nanoparticles was dispersed in 100 mL of ultrapure water, dispersed at 60°C for 5 min, and then 700 μL of oleic acid was added. After ultrasonication for 10 min, 670 mg of dispersant sodium dodecyl sulfate was added to obtain a magnetic fluid aqueous solution.

[0035] Example 2

[0036] The preparation steps of the magnetic impurity removal component in this embodiment are:

[0037] 0.1 g of methylal, 0.8 g of methacrylic acid, and 0.4 g of methacrylamide were dissolved in 10 mL of anhydrous ethanol and prepolymerized at 25°C for 30 min to form a prepolymer solution; 10 mL of magnetic fluid aqueous solution was added to the 10 mL prepolymer solution, and then 2.8 g of ethylene glycol dimethyl acrylate and 0.1 g of 2,2-azobisisobutyronitrile were added under stirring at 800 r / min. Under N2 protection, the mixture was heated at 60°C for 24 h. After separation in an external magnetic field, the template molecule methylal was eluted with 50 mL of a mixed solution of methanol and acetic acid (the volume ratio of methanol to acetic acid was 9:1), and then the mixture was washed with ultrapure water until neutral and dried in a vacuum at 60°C for 24 h to obtain a magnetic impurity removal component.

[0038] Example 3

[0039] The preparation steps of the magnetic impurity removal component in this embodiment are:

[0040] 0.1 g of methylal, 0.9 g of methacrylic acid, and 0.5 g of methacrylamide were dissolved in 10 mL of anhydrous ethanol and prepolymerized at 25°C for 30 min to form a prepolymer solution; 10 mL of magnetic fluid aqueous solution was added to the 10 mL prepolymer solution, and then 3 g of ethylene glycol dimethyl acrylate and 0.1 g of 2,2-azobisisobutyronitrile were added under stirring at 800 r / min. Under N2 protection, the mixture was heated at 60°C for 24 h. After separation in an external magnetic field, the template molecule methylal was eluted with 50 mL of a mixed solution of methanol and acetic acid (the volume ratio of methanol to acetic acid was 9:1), and then the mixture was washed with ultrapure water until neutral and dried in a vacuum at 60°C for 24 h to obtain a magnetic impurity removal component.

[0041] Example 4

[0042] The preparation steps of the magnetic impurity removal component in this embodiment are:

[0043] 0.1 g of methylal, 1 g of methacrylic acid, and 0.6 g of methacrylamide were dissolved in 10 mL of anhydrous ethanol and prepolymerized at 25°C for 30 min to form a prepolymer solution; 10 mL of magnetic fluid aqueous solution was added to the 10 mL prepolymer solution, and then 3.4 g of ethylene glycol dimethyl acrylate and 0.1 g of 2,2-azobisisobutyronitrile were added under stirring at 800 r / min. Under N2 protection, the mixture was heated at 60°C for 24 h. After separation in an external magnetic field, the template molecule methylal was eluted with 50 mL of a mixed solution of methanol and acetic acid (the volume ratio of methanol to acetic acid was 9:1), and then the mixture was washed with ultrapure water until neutral and dried in a vacuum at 60°C for 24 h to obtain a magnetic impurity removal component.

[0044] Comparative Example 1

[0045] This comparative example is based on Example 2, except that methacrylamide is removed, and the remaining raw materials and preparation process are the same as Example 2.

[0046] Example 5

[0047] This embodiment provides a clean recovery process for glyphosate acid by-product chloromethane, comprising the following steps:

[0048] Step A1: The glyphosate synthesis by-product is pressurized to 25 kPaG and then introduced into a water washing tower for washing, and then dehydrated and dried using concentrated sulfuric acid as an absorbent;

[0049] Step A2: The tail gas dried in Step A1 is introduced into a compression condensation system via a compressor, where the temperature of the chloromethane is reduced to -35°C and the pressure is increased to 0.8 MPaG. A compression plus three-stage condensation process is employed to liquefy and recover the chloromethane in the tail gas, yielding liquefied chloromethane and condensed tail gas containing trace amounts of chloromethane. The three-stage condensation process utilizes circulating water for the first stage, -15°C brine for the second stage, and direct evaporation condensation with -35°C R22 for the third stage.

[0050] Step A3: introducing the condensed tail gas in step A2 into an adsorption tower filled with a magnetic impurity removal component, the adsorption tower temperature is 10°C, the pressure is 0.1 MPaG, and methyl chloride is obtained after adsorption;

[0051] Step A4: Return the methyl chloride obtained in step A3 to the compressor inlet in step A2, and repeat steps A2 and A3 together with the dried tail gas.

[0052] Example 6

[0053] This embodiment provides a clean recovery process for glyphosate acid by-product chloromethane, comprising the following steps:

[0054] Step A1: The by-product of glyphosate synthesis is pressurized to 30 kPaG and then introduced into a water washing tower for washing, and then dehydrated and dried using concentrated sulfuric acid as an absorbent;

[0055] Step A2: The tail gas dried in Step A1 is introduced into a compression condensation system via a compressor, where the temperature of the chloromethane is reduced to -35°C and the pressure is increased to 1 MPaG. A compression plus three-stage condensation process is employed to liquefy and recover the chloromethane in the tail gas, yielding liquefied chloromethane and condensed tail gas containing trace amounts of chloromethane. The three-stage condensation process utilizes circulating water for the first stage, -15°C brine for the second stage, and direct evaporation condensation with -35°C R22 for the third stage.

[0056] Step A3: The condensed tail gas in step A2 is introduced into an adsorption tower filled with a magnetic impurity removal component. The temperature of the adsorption tower is 15°C and the pressure is 0.25 MPaG. Methyl chloride is obtained after adsorption;

[0057] Step A4: Return the methyl chloride obtained in step A3 to the compressor inlet in step A2, and repeat steps A2 and A3 together with the dried tail gas.

[0058] Example 7

[0059] This embodiment provides a clean recovery process for glyphosate acid by-product chloromethane, comprising the following steps:

[0060] Step A1: The by-product of glyphosate synthesis is pressurized to 35 kPaG and then introduced into a water washing tower for washing, and then dehydrated and dried using concentrated sulfuric acid as an absorbent;

[0061] Step A2: The tail gas dried in Step A1 is introduced into a compression condensation system via a compressor, the temperature of the chloromethane is reduced to -35°C, and the pressure is increased to 1.2 MPaG. The chloromethane in the tail gas is liquefied and recovered using a compression plus three-stage condensation method to obtain liquefied chloromethane and condensed tail gas containing trace amounts of chloromethane. The three-stage condensation method uses circulating water for the first stage, -15°C brine for the second stage, and direct evaporation condensation of -35°C R22 for the third stage.

[0062] Step A3: The condensed tail gas in step A2 is introduced into an adsorption tower filled with a magnetic impurity removal component. The temperature of the adsorption tower is 20°C and the pressure is 0.4 MPaG. Methyl chloride is obtained after adsorption;

[0063] Step A4: Return the methyl chloride obtained in step A3 to the compressor inlet in step A2, and repeat steps A2 and A3 together with the dried tail gas.

[0064] Comparative Example 2

[0065] The raw materials and steps of this comparative example are the same as those of Example 5, except that the magnetic impurity removal component is replaced by the product prepared in Comparative Example 1.

[0066] The purity and recovery rate of the liquefied methyl chloride recovered in Examples 5 to 7 and Comparative Example 2 were tested, and the test results are shown in Table 1:

[0067] Table 1

[0068] project purity(%) Recovery rate (%) Example 5 76.2 99.94 Example 6 76.9 99.95 Example 7 77.1 99.98 Comparative Example 2 75.3 99.84

[0069] It can be seen from Table 1 that the purity and recovery rate of the chloromethane recovered in Examples 5 to 7 are higher than the purity and recovery rate of the chloromethane recovered in Comparative Example 2, indicating that the adsorption tower composed of the magnetic impurity removal component can achieve excellent impurity removal effect.

[0070] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0071] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A clean recovery process for glyphosate acid by-product chloromethane, characterized in that: The following steps are involved: Step A1: washing the glyphosate synthesis by-product with water and then drying; Step A2: The tail gas dried in step A1 is introduced into a compression condensation system via a compressor, and compression plus three-stage condensation is adopted to liquefy and recover the chloromethane in the tail gas to obtain liquefied chloromethane and condensed tail gas containing trace amounts of chloromethane; Step A3: introducing the condensed tail gas in step A2 into an adsorption tower filled with a magnetic impurity removal component to obtain chloromethane after adsorption; Step A4: Return the chloromethane in step A3 to the compressor inlet in step A2, and repeat steps A2 and A3 together with the dried tail gas.

2. A clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: The by-products of glyphosate synthesis contain 60-70% methyl chloride, 10-20% methylal, 8-20% air, 1-5% hydrogen chloride, 1-5% methanol, and 1-2% water.

3. The clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: In step A1, the glyphosate synthesis by-product is pressurized to 25-35 kPaG and then washed with water.

4. The clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: In step A1, concentrated sulfuric acid is used as an absorbent for dehydration and drying.

5. The clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: In step A2, the three-stage condensation method is as follows: the first stage condensation uses circulating water, the second stage condensation uses -15°C brine, and the third stage condensation uses -35°C R22 direct evaporation condensation; the gas pressure in the compression condensation system is 0.8-1.2 MPaG.

6. The clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: In step A3, the temperature of the adsorption tower is 10-20° C. and the pressure is 0.1-0.4 MPaG.

7. The clean recovery process for glyphosate acid by-product chloromethane according to claim 1, characterized in that: The magnetic impurity removal component is prepared by the following steps: Methylal, methacrylic acid and methacrylamide are dissolved in anhydrous ethanol and prepolymerized at 25°C to form a prepolymer solution; a magnetic fluid aqueous solution is added to the prepolymer solution, and ethylene glycol dimethyl acrylate and 2,2-azobisisobutyronitrile are added under stirring, and the mixture is reacted at 60°C for 24 hours under N2; separation is carried out in an external magnetic field, and the mixture is eluted with mixed solution b, washed with ultrapure water, and dried at 60°C for 24 hours to obtain a magnetic impurity removal component.

8. The clean recovery process for glyphosate acid by-product chloromethane according to claim 7, characterized in that: The dosage ratio of methylal, methacrylic acid, methacrylamide, and anhydrous ethanol is 0.1 g: 0.8-1 g: 0.4-0.6 g: 10 mL; the dosage ratio of prepolymer liquid, magnetic fluid aqueous solution, ethylene glycol dimethyl acrylate, and 2,2-azobisisobutyronitrile is 10 mL: 10 mL: 2.8-3.4 g: 0.1 g; mixed solution b consists of methanol and acetic acid, and the volume ratio of methanol to acetic acid is 9:

1.

9. The clean recovery process for glyphosate acid by-product chloromethane according to claim 7, characterized in that: The magnetic fluid aqueous solution is prepared by the following steps: Step B1: Add ferric chloride hexahydrate and anhydrous sodium acetate to ethylene glycol, stir at 40°C for 15 minutes to obtain a mixture C, transfer the mixture C to an autoclave, and crystallize at 180°C for 24 hours. After the crystallization, perform magnetic separation, wash with anhydrous ethanol and deionized water three times each, and dry at 80°C for 18 hours to obtain Fe3O4 nanoparticles. Step B2: Fe3O4 nanoparticles were dispersed in ultrapure water, dispersed at 60°C for 5 minutes, oleic acid was added, and sodium lauryl sulfate was added after ultrasonication for 10 minutes to obtain a magnetic fluid aqueous solution.

10. The clean recovery process for glyphosate acid by-product chloromethane according to claim 9, characterized in that: In step B1, the usage ratio of ferric chloride hexahydrate, anhydrous sodium acetate, and ethylene glycol is 20 g:40 g:1 L; in step B2, the usage ratio of Fe3O4 nanoparticles, ultrapure water, oleic acid, and sodium lauryl sulfate is 1 g:100 mL:700 μL:670 mg.