A method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate

Abstract

The invention discloses a method for recovering imidazole from imidazole hydrochloride produced as a byproduct of anecortave acetate, and belongs to the technical field of recovering imidazole. The method comprises the following steps: adsorption, pH adjustment, primary dehydration, primary dissolution, removal of sodium ions, secondary dehydration, secondary dissolution, concentration, and cooling crystallization; the adsorption comprises adding a first adsorbent to wastewater, stirring at 50-60 DEG C, filtering, taking filtrate, adding a second adsorbent to the filtrate, stirring at 50-60 DEG C, filtering, taking filtrate, and obtaining wastewater after adsorption; the removal of sodium ions comprises adding water and a third adsorbent to the primary dissolved liquid, stirring at 45-55 DEG C, filtering, taking filtrate, standing, and respectively taking a water layer and a dichloromethane layer to obtain an imidazole aqueous solution and a first portion of a concentrated liquid; the method of the invention can improve the appearance of the recovered imidazole, improve the purity and recovery rate of the recovered imidazole, and the recovered imidazole has a uniform particle size distribution.

Description

Technical Field

[0001] The invention relates to the technical field of recovering imidazole, and in particular to a method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate. Background Art

[0002] Imidazole is a type of diazole, a five-membered aromatic heterocyclic compound containing two meta-nitrogen atoms in its molecular structure. The unshared electron pair of the nitrogen atom at position 1 in the imidazole ring participates in cyclic conjugation, and the electron density of the nitrogen atom is reduced, making it easy for the hydrogen on the nitrogen atom at position 1 to leave in the form of hydrogen ions. Imidazole is acidic and alkaline. It has good stability at room temperature, but it will react with strong acids and strong bases. As an important heterocyclic compound, imidazole is widely used in medicine, materials, pesticides and other fields.

[0003] In the preparation of anecortave acetate, it is necessary to first prepare the intermediate anecortave acetate silyl ether. The existing preparation method of anecortave acetate silyl ether is to use anecortave acetate hydroxyl as a raw material, and carry out a 9-hydroxy elimination reaction with an eliminator to obtain a 9-hydroxy elimination product, and then add chloromethyldimethylsilyl chloride, and the 9-hydroxy elimination product and chloromethyldimethylsilyl chloride are subjected to a 17-hydroxy silyl etherification reaction, and then post-processed to obtain anecortave acetate silyl ether. Among them, the 17-hydroxy silyl etherification reaction requires the use of imidazole as a catalyst, and imidazole can provide a weakly alkaline environment. The byproduct hydrochloric acid in the 17-hydroxy silyl etherification reaction will react with imidazole to form imidazole hydrochloride. Since imidazole hydrochloride is easily soluble in water, it will dissolve in the aqueous phase. In the post-processing process, the aqueous phase is separated from the organic phase, and the imidazole hydrochloride enters the wastewater with the aqueous phase.

[0004] Since the cost of imidazole is high and imidazole hydrochloride is toxic, in order to improve economic benefits and reduce environmental pollution, it is necessary to recover the imidazole hydrochloride in the wastewater. The most commonly used recovery method is to adjust the pH of the wastewater, convert the imidazole hydrochloride into imidazole, then dehydrate it, add an organic solvent to dissolve it, separate the solid-liquid, separate the inorganic salt, then concentrate it, cool it down and crystallize it, separate the solid-liquid, separate the imidazole, and finally dry it to obtain the recovered imidazole.

[0005] However, the above recovery method has the following problems: first, the above method cannot completely remove other organic impurities in the wastewater, resulting in the recovered imidazole containing organic impurities, and the presence of organic impurities will affect the appearance and purity of the imidazole; second, in the preparation of anecortave acetate, the raw materials used contain metal ion impurities, resulting in trace metal ion impurities in the wastewater, and the above method cannot completely remove the metal ion impurities in the wastewater. After the imidazole hydrochloride is converted into imidazole, the metal ion and the imidazole have a coordination effect to form a coordination compound of the metal ion and the imidazole, which will be concentrated, cooled and crystallized. The precipitation of the coordination compound will affect the appearance of imidazole; thirdly, sodium hydroxide is needed to adjust the pH value of the wastewater. There is an interaction between sodium ions and imidazole, which leads to incomplete crystallization during cooling crystallization, and the precipitated imidazole contains sodium, and the purity and recovery rate of the recovered imidazole are reduced; fourthly, in the concentration and cooling crystallization, the imidazole solution needs to be concentrated to saturation, cooled to 0-5°C, and crystallized at 0-5°C. Due to the low crystallization temperature, the precipitated imidazole has an irregular shape and a small particle size, and solid-liquid separation is difficult, which further leads to uneven particle size distribution of the recovered imidazole and a reduced recovery rate.

[0006] In order to solve the above problems, the inventors tried the following recovery method: using activated carbon to adsorb the wastewater, after removing organic impurities and metal ions, the pH of the wastewater is adjusted, the imidazole hydrochloride is converted into imidazole, and then dehydrated, and then dichloromethane is added for extraction, the imidazole is transferred to dichloromethane, and then concentrated, cooled and crystallized, and solid-liquid separation is performed to separate the imidazole, wherein the reduction of crystallization is specifically to slowly cool down, then crystallize, and add imidazole as a seed crystal, so as to promote crystallization, increase the crystallization speed, ensure that the precipitated imidazole has a uniform particle size distribution, and a moderate particle size, thereby reducing the difficulty of solid-liquid separation, and finally drying to obtain recovered imidazole. This recovery method can remove organic impurities and metal ions in the recovered imidazole, and improve the appearance and purity of the recovered imidazole, but the following problems still exist: first, activated carbon is usually negatively charged and will adsorb imidazole hydrochloride through electrostatic adsorption, resulting in a decrease in the recovery rate of the recovered imidazole; second, due to the interaction between sodium ions and imidazole, the precipitated imidazole contains sodium ions, which further reduces the purity of the recovered imidazole. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate, which can improve the appearance of the recovered imidazole, increase the purity and recovery rate of the recovered imidazole, and the recovered imidazole has a uniform particle size distribution.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for recovering imidazole from imidazole hydrochloride produced as a byproduct of anecortave acetate, comprising the following steps: adsorption, pH adjustment, primary dehydration, primary dissolution, removal of sodium ions, secondary dehydration, secondary dissolution, concentration, and cooling and crystallization;

[0010] The adsorption comprises adding a first adsorbent to the wastewater, stirring at 50-60° C. and a stirring speed of 50-100 rpm for 1.5-2 hours, filtering, taking a filtrate, adding a second adsorbent to the filtrate, stirring at 50-60° C. and a stirring speed of 50-100 rpm for 2-2.5 hours, filtering, taking a filtrate, and obtaining the adsorbed wastewater;

[0011] In the adsorption, the mass volume ratio of wastewater, the first adsorbent, and the second adsorbent is 10L:80-85g:27-30g;

[0012] The preparation method of the first adsorbent comprises the following steps: activation, silane modification, and cation modification;

[0013] The activation comprises mixing the activated carbon and the nitric acid aqueous solution, stirring and refluxing at 65-75° C. and a stirring speed of 100-150 rpm for 2-2.5 hours, filtering, taking the filter residue, washing the filter residue with water and drying it to obtain activated activated carbon;

[0014] In the activation, the mass volume ratio of activated carbon to nitric acid aqueous solution is 200-220 g: 2000-2500 mL;

[0015] The particle size of the activated carbon is 100 μm;

[0016] The mass fraction of the nitric acid aqueous solution is 10%;

[0017] The silane modification comprises mixing vinyl triethoxysilane and anhydrous ethanol, stirring at room temperature at a stirring speed of 200-300 rpm for 20-30 minutes, adding activated carbon, stirring and reflux at 55-65° C. at a stirring speed of 200-300 rpm for 8-9 hours, filtering, taking the filter residue, washing the filter residue with anhydrous ethanol and drying it to obtain silane-modified activated carbon;

[0018] In the silane modification, the mass volume ratio of vinyl triethoxysilane, anhydrous ethanol, and activated carbon is 120-125 mL: 900-1000 mL: 190-200 g;

[0019] The cationic modification comprises mixing a dimethyldiallylammonium chloride aqueous solution and water, stirring at a stirring speed of 200-300 rpm for 5-10 min at room temperature, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and reflux at a stirring speed of 200-300 rpm at 60-70° C. for 10-20 min, adding azobisisobutyronitrile, stirring and reflux at a stirring speed of 200-300 rpm at 60-70° C. for 7-7.5 h, filtering, taking a filter residue, washing the filter residue with water, and drying to obtain a first adsorbent;

[0020] In the cationic modification, the mass volume ratio of the dimethyldiallylammonium chloride aqueous solution, water, silane-modified activated carbon, and azobisisobutyronitrile is 850-900 mL: 900-1000 mL: 200-210 g: 4.2-4.5 g;

[0021] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0022] The preparation method of the second adsorbent comprises the following steps: cross-linking modification, grafting modification;

[0023] The cross-linking modification comprises mixing a dimethyldiallylammonium chloride aqueous solution, diallylamine and water, stirring at a stirring speed of 200-300 rpm for 5-10 min at room temperature, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and reflux at a stirring speed of 200-300 rpm at 60-70° C. for 10-20 min, adding azobisisobutyronitrile, stirring and reflux at a stirring speed of 200-300 rpm at 60-70° C. for 8-8.5 h, filtering, taking the filter residue, washing the filter residue with water and drying it to obtain the cross-linked modified activated carbon;

[0024] In the cross-linking modification, the mass volume ratio of the dimethyldiallylammonium chloride aqueous solution, diallylamine, water, silane-modified activated carbon, and azobisisobutyronitrile is 750-800 mL: 50-55 g: 1100-1300 mL: 200-210 g: 4.6-5 g;

[0025] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0026] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in the preparation of the first adsorbent;

[0027] The graft modification comprises mixing acrylic acid and water, stirring at room temperature at a stirring speed of 200-300 rpm for 5-10 minutes, adding cross-linked modified activated carbon in a nitrogen atmosphere, stirring and reflux at 65-75° C. at a stirring speed of 200-300 rpm for 10-20 minutes, adding azobisisobutyronitrile, stirring and reflux at 65-75° C. at a stirring speed of 200-300 rpm for 5-5.5 hours, filtering, taking the filter residue, washing the filter residue with water and drying it to obtain a second adsorbent;

[0028] In the graft modification, the mass volume ratio of acrylic acid, water, cross-linked modified activated carbon, and azobisisobutyronitrile is 360-400 mL: 2000-2500 mL: 200-210 g: 3.8-4 g;

[0029] The pH is adjusted by stirring the adsorbed wastewater at a stirring speed of 50-100 rpm at room temperature, then adding sodium hydroxide to adjust the pH to 7-7.5, and continuing to stir at a stirring speed of 50-100 rpm at room temperature for 30-40 minutes to obtain a mixed solution;

[0030] The primary dehydration is to perform vacuum distillation on the mixed solution at 90-95° C. until no water is evaporated to obtain a primary dehydrated material;

[0031] The primary dissolution, adding dichloromethane to the primary dehydrated material, stirring at 25-35°C at a stirring speed of 50-100 rpm for 25-35 minutes, standing for 2-2.5 hours, filtering, taking the filtrate to obtain a primary dissolution solution;

[0032] The volume ratio of the wastewater in the adsorption to the dichloromethane in the primary dissolution is 10:20-22;

[0033] The sodium ions are removed, water and a third adsorbent are added to the primary solution, the mixture is stirred at 45-55° C. at a stirring speed of 300-400 rpm for 50-60 min, filtered, the filtrate is taken, and allowed to stand for 2-2.5 h, and the water layer and the dichloromethane layer are taken respectively to obtain an imidazole aqueous solution and a first portion of the solution to be concentrated;

[0034] The mass volume ratio of the wastewater in the adsorption, the water in the sodium ion removal, and the third adsorbent is 10L:2-2.1L:33-35g;

[0035] The preparation method of the third adsorbent is as follows: after mixing sodium 2-acrylamide-2-methylpropane sulfonate and water, stirring at room temperature at a stirring speed of 200-300 rpm for 5-10 minutes, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and reflux at 70-75° C. at a stirring speed of 200-300 rpm for 10-20 minutes, adding azobisisobutyronitrile, stirring and reflux at 70-75° C. at a stirring speed of 200-300 rpm for 8-8.5 hours, filtering, taking the filter residue, washing the filter residue with water and drying it to obtain the third adsorbent;

[0036] In the preparation of the third adsorbent, the mass volume ratio of sodium 2-acrylamide-2-methylpropane sulfonate, water, silane-modified activated carbon, and azobisisobutyronitrile is 500-510 g: 1400-1500 mL: 200-210 g: 6.5-7 g;

[0037] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in the preparation of the first adsorbent;

[0038] The secondary dehydration comprises distilling the imidazole aqueous solution under reduced pressure at 90-95° C. until no water is evaporated to obtain a secondary dehydrated material;

[0039] The secondary dissolution, adding dichloromethane to the secondary dehydrated material, stirring at 25-35°C at a stirring speed of 50-100 rpm for 25-35 minutes, standing for 2-2.5 hours, filtering, taking the filtrate, and obtaining a second portion of the concentrated solution;

[0040] The volume ratio of the wastewater in the adsorption to the dichloromethane in the secondary dissolution is 10:10-12;

[0041] The concentration comprises mixing the first liquid to be concentrated and the second liquid to be concentrated, and distilling under reduced pressure at 35-40° C. until crystals are precipitated to obtain a concentrated solution;

[0042] The cooling crystallization is performed by adding imidazole to the concentrated solution, stirring at room temperature at a stirring speed of 40-50 rpm for 5-10 minutes, cooling to 3-5°C at a cooling rate of 0.05-0.06°C / min, stirring at 3-5°C at a stirring speed of 40-50 rpm for 2-2.5 hours, filtering, taking the filter residue, and vacuum drying to obtain recovered imidazole;

[0043] In the cooling crystallization, the mass volume ratio of the wastewater in the adsorption to the imidazole in the cooling crystallization is 10L:29-30g;

[0044] The mass purity of the imidazole is 99.7%.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The method for recovering imidazole from imidazole hydrochloride produced as a byproduct of anecortave acetate of the present invention comprises adding an adsorbent before adjusting the pH value of the wastewater, wherein the adsorption is specifically performed by sequentially adding a first adsorbent and a second adsorbent for adsorption, wherein the preparation method of the first adsorbent is to perform an activation treatment on activated carbon, introduce a hydroxyl group, perform silane modification using vinyltriethoxysilane, introduce a vinyl group, obtain activated carbon with a vinyl group, and then perform cation modification on the activated carbon with a vinyl group, introduce a cationic charge of polydimethyldiallylammonium chloride, and obtain a first adsorbent with a cationic charge. The first adsorbent can adsorb organic matter in the wastewater and can also avoid adsorption of imidazole hydrochloride, but has a relatively poor adsorption property for metal ions in the wastewater. The preparation method of the second adsorbent is to use a cationic monomer and a cross-linking agent to cross-link and modify the activated carbon with vinyl, introduce polydimethyldiallyl ammonium chloride with a cationic charge, and introduce a double bond to obtain a cross-linked modified activated carbon, and then use acrylic acid to graft and modify the cross-linked modified activated carbon, introduce polyacrylic acid, and obtain a second adsorbent with an outer layer of polyacrylic acid, a middle layer of cross-linked polydimethyldiallyl ammonium chloride, and an inner core of activated carbon. The polyacrylic acid in the outer layer of the second adsorbent can complex metal ions, and the cross-linked polydimethyldiallyl ammonium chloride in the middle layer can avoid the adsorption of imidazole hydrochloride by the activated carbon due to its cationic charge, thereby improving the purity of the recovered imidazole while improving the recovery rate of the recovered imidazole. In addition, after one dehydration and one dissolution, sodium ion removal is added. In the process of removing sodium ions, water and a third adsorbent are added. The preparation method of the third adsorbent is to modify the activated carbon with vinyl using anionic monomer 2-acrylamide-2-methylpropanesulfonate sodium, introduce poly 2-acrylamide-2-methylpropanesulfonate sodium with anionic charge, thereby obtaining a third adsorbent with anionic charge. In the process of removing sodium ions, sodium ions interact with the anionic charges of imidazole and the third adsorbent. Since the interaction between sodium ions and imidazole is due to the high electron cloud density on the nitrogen atom of imidazole, there is an electrostatic attraction between imidazole and sodium ions, and the anionic charge of the third adsorbent can destroy the electrostatic attraction and recombined with sodium ions. The addition of water can promote the transfer of sodium ions. Finally, the third adsorbent combined with sodium ions is removed by filtration, thereby obtaining high-purity imidazole.

[0047] (2) The method of recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to the present invention can improve the appearance of the recovered imidazole, and the recovered imidazole is a white crystalline powder;

[0048] (3) The method of recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to the present invention can improve the purity of the recovered imidazole, and the mass purity of the recovered imidazole can reach 99.6-99.7%;

[0049] (4) The method of recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to the present invention can improve the recovery rate of the recovered imidazole, and the recovery rate of the recovered imidazole can reach 94.4-95.3%;

[0050] (5) The method of recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to the present invention can ensure that the recovered imidazole has a uniform particle size distribution. DETAILED DESCRIPTION

[0051] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0052] The calculation formula for the recovery rate of imidazole recovered in Example 1-3 and Comparative Example 1-3 is: (the mass of imidazole recovered in the 9th step of cooling crystallization × the mass purity of the recovered imidazole - the mass of imidazole added in the 9th step of cooling crystallization × the mass purity of imidazole added in the 9th step of cooling crystallization) / 2485.8g × 100%;

[0053] The calculation formula for the recovery rate of imidazole recovered in Comparative Example 4 is: the mass of the recovered imidazole obtained in the cooling crystallization in step 9 × the mass purity of the recovered imidazole / 2485.8 g × 100%.

[0054] The calculation method of 2485.8g is: based on the fact that 10L of wastewater contains 3817g of imidazole hydrochloride, the amount of imidazole hydrochloride contained is calculated to be (3817 / 104.54) mol. The theoretical mass of imidazole that can be obtained is further calculated to be (68.08×3817 / 104.54) g, that is, 2485.8g.

[0055] The wastewater used in Examples 1-3 and Comparative Examples 1-4 is from the same batch of wastewater.

[0056] Example 1

[0057] A method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate, specifically comprising:

[0058] 1. Adsorption: add 80g of the first adsorbent to 10L of wastewater, stir at 50°C at a stirring speed of 50rpm for 1.5h, filter, take the filtrate, add 27g of the second adsorbent to the filtrate, stir at 50°C at a stirring speed of 50rpm for 2h, filter, take the filtrate, and obtain the adsorbed wastewater;

[0059] The content of imidazole hydrochloride in the wastewater is 381.7 g / L;

[0060] The preparation method of the first adsorbent is:

[0061] (1) Activation: Mix 200 g of activated carbon and 2000 mL of 10% nitric acid aqueous solution, stir and reflux at 65 °C at a stirring speed of 100 rpm for 2 h, filter, take the filter residue, wash the filter residue with water and dry it to obtain activated activated carbon;

[0062] The particle size of the activated carbon is 100 μm;

[0063] (2) Silane modification: 120 mL of vinyl triethoxysilane and 900 mL of anhydrous ethanol were mixed, stirred at room temperature at a stirring speed of 200 rpm for 20 min, 190 g of activated carbon was added, and the mixture was stirred and refluxed at 55 °C at a stirring speed of 200 rpm for 8 h. The mixture was filtered, the filter residue was washed with anhydrous ethanol, and then dried to obtain silane-modified activated carbon.

[0064] (3) Cationic modification: 850 mL of dimethyldiallylammonium chloride aqueous solution and 900 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 200 rpm for 5 min. In a nitrogen atmosphere, 200 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 60° C. at a stirring speed of 200 rpm for 10 min. 4.2 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 60° C. at a stirring speed of 200 rpm for 7 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain a first adsorbent.

[0065] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0066] The preparation method of the second adsorbent is:

[0067] (1) Cross-linking modification: 750 mL of dimethyldiallylammonium chloride aqueous solution, 50 g of diallylamine and 1100 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 200 rpm for 5 min. In a nitrogen atmosphere, 200 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 60°C at a stirring speed of 200 rpm for 10 min. 4.6 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 60°C at a stirring speed of 200 rpm for 8 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain cross-linked modified activated carbon.

[0068] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0069] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0070] (2) Graft modification: 360 mL of acrylic acid and 2000 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 200 rpm for 5 min. In a nitrogen atmosphere, 200 g of cross-linked modified activated carbon was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 200 rpm for 10 min. 3.8 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 200 rpm for 5 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain a second adsorbent;

[0071] 2. Adjusting pH: Stirring the adsorbed wastewater obtained in the first step of adsorption at room temperature at a stirring speed of 50 rpm, then adding sodium hydroxide to adjust the pH to 7, and continuing to stir at room temperature at a stirring speed of 50 rpm for 30 minutes to obtain a mixed solution;

[0072] 3. Primary dehydration: distill the mixed solution obtained in step 2 of adjusting pH under reduced pressure at 90°C until no water is evaporated to obtain a primary dehydrated material;

[0073] 4. Primary dissolution: add 20 L of dichloromethane to the primary dehydrated material obtained in the primary dehydration in step 3, stir at 25 °C at a stirring speed of 50 rpm for 25 min, let stand for 2 h, filter, and take the filtrate to obtain a primary dissolution solution;

[0074] 5. Removal of sodium ions: add 2L of water and 33g of the third adsorbent to the primary solution obtained in the primary dissolution in step 4, stir at 45°C at a stirring speed of 300rpm for 50min, filter, take the filtrate, let it stand for 2h, take the water layer and the dichloromethane layer respectively, and obtain the imidazole aqueous solution and the first portion of the concentrated solution;

[0075] The preparation method of the third adsorbent is as follows: 500g of sodium 2-acrylamide-2-methylpropane sulfonate and 1400mL of water are mixed, and the mixture is stirred at a stirring speed of 200rpm for 5min at room temperature, 200g of silane-modified activated carbon is added in a nitrogen atmosphere, and the mixture is stirred and refluxed at a stirring speed of 200rpm for 10min at 70°C, 6.5g of azobisisobutyronitrile is added, and the mixture is stirred and refluxed at a stirring speed of 200rpm for 8h at 70°C, filtered, and the filter residue is taken, and the filter residue is washed with water and then dried to obtain the third adsorbent;

[0076] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0077] 6. Secondary dehydration: distill the imidazole aqueous solution obtained by removing sodium ions in step 5 under reduced pressure at 90° C. until no water is evaporated to obtain a secondary dehydrated material;

[0078] 7. Secondary dissolution: add 10L of dichloromethane to the secondary dehydrated material obtained in the second dehydration in step 6, stir at 25°C at a stirring speed of 50rpm for 25min, let stand for 2h, filter, and take the filtrate to obtain the second portion of the concentrated solution;

[0079] 8. Concentration: Mix the first portion of the concentrated solution obtained by removing sodium ions in step 5 and the second portion of the concentrated solution obtained by secondary dissolution in step 7, and distill under reduced pressure at 35° C. until crystals are precipitated to obtain a concentrated solution;

[0080] 9. Cooling crystallization: add 29 g of imidazole to the concentrated solution obtained in step 8, stir at room temperature at a stirring speed of 40 rpm for 5 min, cool to 3°C at a cooling rate of 0.05°C / min, stir at a stirring speed of 40 rpm for 2 h at 3°C, filter, take the filter residue, and vacuum dry to obtain recovered imidazole;

[0081] The mass purity of the imidazole is 99.7%.

[0082] In this embodiment, a total of 2384.8 g of recovered imidazole was obtained, with a mass purity of 99.6% and a recovery rate of 94.4%.

[0083] The imidazole obtained in this example is a white crystalline powder with uniform particle size distribution.

[0084] Example 2

[0085] A method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate, specifically comprising:

[0086] 1. Adsorption: add 82g of the first adsorbent to 10L of wastewater, stir at 55°C at a stirring speed of 80rpm for 1.5h, filter, take the filtrate, add 28g of the second adsorbent to the filtrate, stir at 55°C at a stirring speed of 80rpm for 2h, filter, take the filtrate, and obtain the adsorbed wastewater;

[0087] The content of imidazole hydrochloride in the wastewater is 381.7 g / L;

[0088] The preparation method of the first adsorbent is:

[0089] (1) Activation: Mix 210 g of activated carbon and 2200 mL of 10% nitric acid aqueous solution, stir and reflux at 70 °C at a stirring speed of 120 rpm for 2 h, filter, take the filter residue, wash the filter residue with water and dry it to obtain activated activated carbon;

[0090] The particle size of the activated carbon is 100 μm;

[0091] (2) Silane modification: 122 mL of vinyl triethoxysilane and 950 mL of anhydrous ethanol were mixed, stirred at room temperature at a stirring speed of 250 rpm for 25 min, 195 g of activated carbon was added, and the mixture was stirred and refluxed at 60 °C at a stirring speed of 250 rpm for 8.5 h. The mixture was filtered, the filter residue was washed with anhydrous ethanol, and then dried to obtain silane-modified activated carbon.

[0092] (3) Cationic modification: 870 mL of dimethyldiallylammonium chloride aqueous solution and 950 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 250 rpm for 8 min. In a nitrogen atmosphere, 205 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 250 rpm for 15 min. 4.4 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 250 rpm for 7 h. The mixture was filtered, and the filter residue was taken, washed with water, and then dried to obtain a first adsorbent;

[0093] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0094] The preparation method of the second adsorbent is:

[0095] (1) Cross-linking modification: 780 mL of dimethyldiallylammonium chloride aqueous solution, 52 g of diallylamine and 1200 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 250 rpm for 8 min. In a nitrogen atmosphere, 205 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 250 rpm for 15 min. 4.8 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 65 ° C at a stirring speed of 250 rpm for 8 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain cross-linked modified activated carbon;

[0096] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0097] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0098] (2) Graft modification: 380 mL of acrylic acid and 2200 mL of water were mixed, and the mixture was stirred at room temperature at a stirring speed of 250 rpm for 8 min. In a nitrogen atmosphere, 205 g of cross-linked modified activated carbon was added, and the mixture was stirred and refluxed at 70 ° C at a stirring speed of 250 rpm for 15 min. 3.9 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 70 ° C at a stirring speed of 250 rpm for 5 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain a second adsorbent;

[0099] 2. Adjusting pH: Stirring the adsorbed wastewater obtained in the first step of adsorption at room temperature at a stirring speed of 80 rpm, then adding sodium hydroxide to adjust the pH to 7.2, and continuing to stir at room temperature at a stirring speed of 80 rpm for 35 minutes to obtain a mixed solution;

[0100] 3. Primary dehydration: distill the mixed solution obtained in step 2 of adjusting pH under reduced pressure at 95°C until no water is evaporated to obtain a primary dehydrated material;

[0101] 4. Primary dissolution: add 21L of dichloromethane to the primary dehydrated material obtained in the primary dehydration in step 3, stir at 80 rpm for 30 min at 30°C, let stand for 2 h, filter, and take the filtrate to obtain a primary dissolution solution;

[0102] 5. Removal of sodium ions: add 2L of water and 34g of the third adsorbent to the primary solution obtained in the primary dissolution in step 4, stir at 50°C and 350rpm for 55min, filter, take the filtrate, let stand for 2h, take the water layer and the dichloromethane layer respectively, and obtain the imidazole aqueous solution and the first portion of the concentrated solution;

[0103] The preparation method of the third adsorbent is as follows: 505g of sodium 2-acrylamide-2-methylpropane sulfonate and 1450mL of water are mixed, and the mixture is stirred at a stirring speed of 250rpm for 8min at room temperature, 205g of silane-modified activated carbon is added in a nitrogen atmosphere, and the mixture is stirred and refluxed at a stirring speed of 250rpm for 15min at 72°C, 6.8g of azobisisobutyronitrile is added, and the mixture is stirred and refluxed at a stirring speed of 250rpm for 8h at 72°C, filtered, and the filter residue is taken, and the filter residue is washed with water and then dried to obtain the third adsorbent;

[0104] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0105] 6. Secondary dehydration: distill the imidazole aqueous solution obtained by removing sodium ions in step 5 under reduced pressure at 95°C until no water is evaporated to obtain a secondary dehydrated material;

[0106] 7. Secondary dissolution: add 11L of dichloromethane to the secondary dehydrated material obtained in the second dehydration in step 6, stir at 80 rpm for 30 min at 30°C, let stand for 2 h, filter, and take the filtrate to obtain the second portion of the concentrated solution;

[0107] 8. Concentration: Mix the first portion of the concentrated solution obtained by removing sodium ions in step 5 and the second portion of the concentrated solution obtained by secondary dissolution in step 7, and distill under reduced pressure at 38° C. until crystals are precipitated to obtain a concentrated solution;

[0108] 9. Cooling crystallization: add 29.5 g of imidazole to the concentrated solution obtained in step 8, stir at room temperature at a stirring speed of 45 rpm for 8 min, cool to 4°C at a cooling rate of 0.05°C / min, stir at 45 rpm for 2 h at 4°C, filter, take the filter residue, and vacuum dry to obtain recovered imidazole;

[0109] The mass purity of the imidazole is 99.7%.

[0110] In this embodiment, a total of 2401.3 g of recovered imidazole was obtained, with a mass purity of 99.7% and a recovery rate of 95.1%.

[0111] The imidazole obtained in this example is a white crystalline powder with uniform particle size distribution.

[0112] Example 3

[0113] A method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate, specifically comprising:

[0114] 1. Adsorption: add 85g of the first adsorbent to 10L of wastewater, stir at 60°C at a stirring speed of 100rpm for 2h, filter, take the filtrate, add 30g of the second adsorbent to the filtrate, stir at 60°C at a stirring speed of 100rpm for 2.5h, filter, take the filtrate, and obtain the adsorbed wastewater;

[0115] The content of imidazole hydrochloride in the wastewater is 381.7 g / L;

[0116] The preparation method of the first adsorbent is:

[0117] (1) Activation: Mix 220 g of activated carbon and 2500 mL of 10% nitric acid aqueous solution, stir and reflux at 75 °C at a stirring speed of 150 rpm for 2.5 h, filter, take the filter residue, wash the filter residue with water and dry it to obtain activated activated carbon;

[0118] The particle size of the activated carbon is 100 μm;

[0119] (2) Silane modification: 125 mL of vinyl triethoxysilane and 1000 mL of anhydrous ethanol were mixed, stirred at room temperature at a stirring speed of 300 rpm for 30 min, 200 g of activated carbon was added, and the mixture was stirred and refluxed at 65 °C at a stirring speed of 300 rpm for 9 h. The mixture was filtered, the filter residue was taken, and the filter residue was washed with anhydrous ethanol and then dried to obtain silane-modified activated carbon;

[0120] (3) Cationic modification: 900 mL of dimethyldiallylammonium chloride aqueous solution and 1000 mL of water were mixed, and the mixture was stirred at 300 rpm for 10 min at room temperature. In a nitrogen atmosphere, 210 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 70° C. at 300 rpm for 20 min. 4.5 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 70° C. at 300 rpm for 7.5 h. The mixture was filtered, and the filter residue was taken. The filter residue was washed with water and then dried to obtain a first adsorbent.

[0121] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0122] The preparation method of the second adsorbent is:

[0123] (1) Cross-linking modification: 800 mL of dimethyldiallylammonium chloride aqueous solution, 55 g of diallylamine and 1300 mL of water were mixed, and the mixture was stirred at 300 rpm for 10 min at room temperature. In a nitrogen atmosphere, 210 g of silane-modified activated carbon was added, and the mixture was stirred and refluxed at 70°C at 300 rpm for 20 min. 5 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 70°C at 300 rpm for 8.5 h. The mixture was filtered, and the residue was washed with water and then dried to obtain cross-linked modified activated carbon.

[0124] The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%;

[0125] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0126] (2) Graft modification: 400 mL of acrylic acid and 2500 mL of water were mixed, and the mixture was stirred at 300 rpm for 10 min at room temperature. In a nitrogen atmosphere, 210 g of cross-linked modified activated carbon was added, and the mixture was stirred and refluxed at 75 °C at 300 rpm for 20 min. 4 g of azobisisobutyronitrile was added, and the mixture was stirred and refluxed at 75 °C at 300 rpm for 5.5 h. The mixture was filtered, and the residue was washed with water and then dried to obtain a second adsorbent.

[0127] 2. Adjusting pH: Stirring the adsorbed wastewater obtained in the first step of adsorption at room temperature at a stirring speed of 100 rpm, then adding sodium hydroxide to adjust the pH to 7.5, and continuing to stir at room temperature at a stirring speed of 100 rpm for 40 minutes to obtain a mixed solution;

[0128] 3. Primary dehydration: distill the mixed solution obtained in step 2 of adjusting pH under reduced pressure at 95°C until no water is evaporated to obtain a primary dehydrated material;

[0129] 4. Primary dissolution: add 22 L of dichloromethane to the primary dehydrated material obtained in the first dehydration in step 3, stir at 35 ° C at a stirring speed of 100 rpm for 35 min, let stand for 2.5 h, filter, and take the filtrate to obtain a primary dissolution solution;

[0130] 5. Removal of sodium ions: add 2.1 L of water and 35 g of the third adsorbent to the primary solution obtained in the primary dissolution in step 4, stir at 55°C and 400 rpm for 60 min, filter, take the filtrate, let stand for 2.5 h, take the water layer and the dichloromethane layer respectively, and obtain the imidazole aqueous solution and the first portion of the concentrated solution;

[0131] The preparation method of the third adsorbent is as follows: 510 g of sodium 2-acrylamide-2-methylpropane sulfonate and 1500 mL of water are mixed, and the mixture is stirred at a stirring speed of 300 rpm for 10 min at room temperature; 210 g of silane-modified activated carbon is added in a nitrogen atmosphere, and the mixture is stirred and refluxed at a stirring speed of 300 rpm at 75° C. for 20 min; 7 g of azobisisobutyronitrile is added, and the mixture is stirred and refluxed at a stirring speed of 300 rpm at 75° C. for 8.5 h; the mixture is filtered, and the filter residue is taken, and the filter residue is washed with water and then dried to obtain the third adsorbent;

[0132] The preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in step (2) of the preparation of the first adsorbent;

[0133] 6. Secondary dehydration: distill the imidazole aqueous solution obtained by removing sodium ions in step 5 under reduced pressure at 95°C until no water is evaporated to obtain a secondary dehydrated material;

[0134] 7. Secondary dissolution: add 12 L of dichloromethane to the secondary dehydrated material obtained in the second dehydration in step 6, stir at 35°C at a stirring speed of 100 rpm for 35 min, let stand for 2.5 h, filter, and take the filtrate to obtain the second portion of the concentrated solution;

[0135] 8. Concentration: Mix the first portion of the concentrated solution obtained by removing sodium ions in step 5 and the second portion of the concentrated solution obtained by secondary dissolution in step 7, and distill under reduced pressure at 40° C. until crystals are precipitated to obtain a concentrated solution;

[0136] 9. Cooling crystallization: add 30 g of imidazole to the concentrated solution obtained in step 8, stir at room temperature at a stirring speed of 50 rpm for 10 min, cool to 5°C at a cooling rate of 0.06°C / min, stir at 5°C at a stirring speed of 50 rpm for 2.5 h, filter, take the filter residue, and vacuum dry to obtain recovered imidazole;

[0137] The mass purity of the imidazole is 99.7%.

[0138] In this embodiment, a total of 2405.7 g of recovered imidazole was obtained, with a mass purity of 99.7% and a recovery rate of 95.3%.

[0139] The imidazole obtained in this example is a white crystalline powder with uniform particle size distribution.

[0140] Comparative Example 1

[0141] On the basis of Example 2, in the first step of adsorption, activated carbon is used in equal amounts to replace the first adsorbent and the second adsorbent, and specifically the first step of adsorption is changed to:

[0142] Add 82 g of activated carbon to 10 L of wastewater, stir at 55 ° C at a stirring speed of 80 rpm for 1.5 h, filter, take the filtrate, add 28 g of activated carbon to the filtrate, stir at 55 ° C at a stirring speed of 80 rpm for 2 h, filter, take the filtrate to obtain the adsorbed wastewater;

[0143] The particle size of the activated carbon is 100 μm.

[0144] The remaining operations are the same as those in Example 2.

[0145] In this comparative example, a total of 2315.6 g of recovered imidazole was obtained, with a mass purity of 99.7% and a recovery rate of 91.7%.

[0146] The imidazole obtained in this comparative example is a white crystalline powder with uniform particle size distribution.

[0147] Comparative Example 2

[0148] On the basis of Example 2, the fifth step of removing sodium ions, the sixth step of secondary dehydration, and the seventh step of secondary dissolution are omitted, and the eighth step of concentration is changed to:

[0149] The primary solution obtained in the primary dissolution in step 4 was subjected to reduced pressure distillation at 38°C until crystals were precipitated to obtain a concentrated solution.

[0150] The remaining operations are the same as those in Example 2.

[0151] In this comparative example, a total of 2405.2 g of recovered imidazole was obtained, with a mass purity of 99.1% and a recovery rate of 94.7%.

[0152] The imidazole obtained in this comparative example is a white crystalline powder with uniform particle size distribution.

[0153] Comparative Example 3

[0154] Based on Example 2, the first step of adsorption was omitted, and the second step of pH adjustment was changed to:

[0155] The wastewater was stirred at room temperature at a stirring speed of 80 rpm, and then sodium hydroxide was added to adjust the pH to 7.2, and the stirring was continued at room temperature at a stirring speed of 80 rpm for 35 minutes to obtain a mixed solution;

[0156] The content of imidazole hydrochloride in the wastewater is 381.7 g / L;

[0157] The remaining operations are the same as those in Example 2.

[0158] In this comparative example, a total of 2403.1 g of recovered imidazole was obtained, with a mass purity of 98.5% and a recovery rate of 94.0%.

[0159] The imidazole obtained in this comparative example is a yellow-green crystalline powder with uniform particle size distribution.

[0160] Comparative Example 4

[0161] On the basis of Example 2, in the ninth step of cooling and crystallizing, the addition of 29.5 g of imidazole was omitted, and the ninth step of cooling and crystallizing was specifically changed to:

[0162] The concentrated solution obtained in step 8 was cooled to 4°C at a cooling rate of 0.05°C / min, stirred at 45 rpm for 2 h at 4°C, filtered, and the filter residue was vacuum dried to obtain recovered imidazole.

[0163] The remaining operations are the same as those in Example 2.

[0164] In this comparative example, a total of 2301.4 g of recovered imidazole was obtained, with a mass purity of 99.6% and a recovery rate of 92.2%.

[0165] The imidazole obtained in this comparative example is a white crystalline powder with uneven particle size distribution.

[0166] By comparing the results of Comparative Example 1 with those of Example 2, it can be seen that the use of the first adsorbent and the second adsorbent can improve the recovery rate of the recovered imidazole; by comparing the results of Comparative Example 2 with those of Example 2, it can be seen that the use of the third adsorbent can improve the mass purity and recovery rate of the recovered imidazole; by comparing the results of Comparative Example 3 with those of Example 2, it can be seen that by adsorbing the wastewater, the appearance of the recovered imidazole can be improved and the mass purity of the recovered imidazole can be improved; by comparing the results of Comparative Example 4 with those of Example 2, it can be seen that by adding imidazole during the cooling crystallization, the mass purity of the recovered imidazole can be improved and the uniform particle size distribution of the recovered imidazole can be ensured.

[0167] Unless otherwise specified, all percentages used in the present invention are by mass.

[0168] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate, characterized in that: The process consists of the following steps: adsorption, pH adjustment, primary dehydration, primary dissolution, removal of sodium ions, secondary dehydration, secondary dissolution, concentration, and cooling and crystallization; The adsorption comprises adding a first adsorbent to the wastewater, stirring at 50-60° C., filtering, taking a filtrate, adding a second adsorbent to the filtrate, stirring at 50-60° C., filtering, taking a filtrate, and obtaining the adsorbed wastewater; In the adsorption, the mass volume ratio of wastewater, the first adsorbent, and the second adsorbent is 10L:80-85g:27-30g; The preparation method of the first adsorbent comprises the following steps: activation, silane modification, and cation modification; The activation comprises mixing the activated carbon and the nitric acid aqueous solution, stirring and refluxing at 65-75° C., filtering, taking the filter residue, washing the filter residue and drying it to obtain the activated activated carbon; The silane modification comprises mixing vinyl triethoxysilane and anhydrous ethanol, stirring at room temperature, adding activated carbon, stirring and refluxing at 55-65° C., filtering, taking the filter residue, washing the filter residue and drying it to obtain silane-modified activated carbon; The cationic modification comprises mixing a dimethyldiallylammonium chloride aqueous solution and water, stirring at room temperature, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and refluxing at 60-70° C., adding azobisisobutyronitrile, stirring and refluxing at 60-70° C., filtering, taking a filter residue, washing the filter residue and drying it to obtain a first adsorbent; The preparation method of the second adsorbent comprises the following steps: cross-linking modification, grafting modification; The cross-linking modification comprises mixing a dimethyldiallylammonium chloride aqueous solution, diallylamine and water, stirring at room temperature, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and refluxing at 60-70° C., adding azobisisobutyronitrile, stirring and refluxing at 60-70° C., filtering, taking a filter residue, washing the filter residue and drying it to obtain a cross-linked modified activated carbon; In the cross-linking modification, the preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in the preparation of the first adsorbent; The graft modification comprises mixing acrylic acid and water, stirring at room temperature, adding cross-linked modified activated carbon in a nitrogen atmosphere, stirring and refluxing at 65-75° C., adding azobisisobutyronitrile, stirring and refluxing at 65-75° C., filtering, taking the filter residue, washing the filter residue and drying it to obtain a second adsorbent; The sodium ions are removed, water and a third adsorbent are added to the first dissolved solution, the solution is stirred at 45-55° C., filtered, the filtrate is taken, and the solution is allowed to stand, and the water layer and the dichloromethane layer are taken respectively to obtain an imidazole aqueous solution and a first portion of the solution to be concentrated; The mass volume ratio of the wastewater in the adsorption, the water in the sodium ion removal, and the third adsorbent is 10L:2-2.1L:33-35g; The preparation method of the third adsorbent is as follows: after mixing sodium 2-acrylamide-2-methylpropane sulfonate and water, stirring at room temperature, adding silane-modified activated carbon in a nitrogen atmosphere, stirring and refluxing at 70-75° C., adding azobisisobutyronitrile, stirring and refluxing at 70-75° C., filtering, taking the filter residue, washing the filter residue and drying it to obtain the third adsorbent; In the preparation of the third adsorbent, the preparation method of the silane-modified activated carbon is the same as the preparation method of the silane-modified activated carbon obtained by silane modification in the preparation of the first adsorbent.

2. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: In the activation, the mass volume ratio of activated carbon to nitric acid aqueous solution is 200-220 g: 2000-2500 mL; The particle size of the activated carbon is 100 μm; The mass fraction of the nitric acid aqueous solution is 10%.

3. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: In the silane modification, the mass volume ratio of vinyl triethoxysilane, anhydrous ethanol and activated carbon is 120-125 mL: 900-1000 mL: 190-200 g.

4. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: In the cationic modification, the mass volume ratio of the dimethyldiallylammonium chloride aqueous solution, water, silane-modified activated carbon, and azobisisobutyronitrile is 850-900 mL: 900-1000 mL: 200-210 g: 4.2-4.5 g; The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%; In the cross-linking modification, the mass volume ratio of the dimethyldiallylammonium chloride aqueous solution, diallylamine, water, silane-modified activated carbon, and azobisisobutyronitrile is 750-800 mL: 50-55 g: 1100-1300 mL: 200-210 g: 4.6-5 g; The mass fraction of the dimethyldiallylammonium chloride aqueous solution is 60%; In the graft modification, the mass volume ratio of acrylic acid, water, cross-linked modified activated carbon and azobisisobutyronitrile is 360-400 mL: 2000-2500 mL: 200-210 g: 3.8-4 g.

5. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: The pH is adjusted by stirring the adsorbed wastewater at room temperature, then adding sodium hydroxide to adjust the pH to 7-7.5, and continuing to stir at room temperature to obtain a mixed solution; The primary dehydration is to perform vacuum distillation on the mixed solution at 90-95° C. until no water is evaporated to obtain a primary dehydrated material; The primary dissolution, adding dichloromethane to the primary dehydrated material, stirring at 25-35°C, standing, filtering, taking the filtrate, and obtaining a primary dissolution solution; The volume ratio of the wastewater in the adsorption to the dichloromethane in the primary dissolution is 10:20-22.

6. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: In the preparation of the third adsorbent, the mass volume ratio of sodium 2-acrylamide-2-methylpropane sulfonate, water, silane-modified activated carbon, and azobisisobutyronitrile is 500-510 g: 1400-1500 mL: 200-210 g: 6.5-7 g.

7. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: The secondary dehydration comprises distilling the imidazole aqueous solution under reduced pressure at 90-95° C. until no water is evaporated to obtain a secondary dehydrated material; The secondary dissolution, adding dichloromethane to the secondary dehydrated material, stirring at 25-35°C, standing, filtering, and taking the filtrate to obtain the second portion of the concentrated solution; The volume ratio of the wastewater in the adsorption to the dichloromethane in the secondary dissolution is 10:10-12; For the concentration, the first liquid to be concentrated and the second liquid to be concentrated are mixed, and then distilled under reduced pressure at 35-40° C. until crystals are precipitated to obtain a concentrated solution.

8. The method for recovering imidazole from imidazole hydrochloride produced as a by-product of anecortave acetate according to claim 1, characterized in that: The cooling crystallization is performed by adding imidazole to the concentrated solution, stirring at room temperature at a stirring speed of 40-50 rpm for 5-10 minutes, cooling to 3-5°C at a cooling rate of 0.05-0.06°C / min, stirring at 3-5°C at a stirring speed of 40-50 rpm for 2-2.5 hours, filtering, taking the filter residue, and vacuum drying to obtain recovered imidazole; In the cooling crystallization, the mass volume ratio of the wastewater in the adsorption to the imidazole in the cooling crystallization is 10L:29-30g.