Post-treatment method of acid-containing DNBP crude product

Abstract

The invention provides a post-treatment method of an acid-containing DNBP crude product. The method comprises the following steps: deacidifying and dehydrating an acid-containing DNBP crude product to obtain a neutral DNBP crude product, mixing the neutral DNBP crude product with a crystallization solvent, and carrying out low-temperature recrystallization refining purification, so that a traditional DNBP crude product post-treatment refining process of washing with water and then distilling is abandoned, the refining process is green and environment-friendly, no wastewater is generated, the low-temperature recrystallization refining process does not need to heat a nitride DNBP, and the yield is high. The crystallization mother liquor obtained by recrystallization is rectified and separated to obtain a reaction solvent and a crystallization solvent for cyclic utilization, and meanwhile, after the crystallization solvent is added into the DNBP byproduct obtained after rectification, the DNBP byproduct can be further subjected to low-temperature crystallization purification. Tests show that the purity of the obtained pure DNBP product is more than or equal to 99%, the free acid content (in terms of H2SO4) is less than or equal to 0.01%, the benzene insoluble substance content is less than or equal to 0.1%, and each index meets the industrial requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical product preparation, and in particular relates to a post-processing method for a crude acid-containing DNBP product. Background Art

[0002] Styrene is an important organic chemical raw material and is generally prepared by the dehydrogenation of ethylbenzene. However, since the exocyclic double bonds of styrene are very active, free radical polymerization is initiated by heat during the distillation process to form polymers, which not only consumes styrene monomers and affects product quality, but also seriously threatens the continuous production. Inhibitors are usually added in industry to suppress its polymerization.

[0003] 2-sec-butyl-4,6-dinitrophenol (DNBP) is a high-temperature inhibitor for the distillation of vinyl aromatic compounds such as styrene and methyl styrene. The product has high inhibition efficiency and low cost. Therefore, most of the current styrene production facilities use 70% DNBP ethylbenzene solution as a high-temperature inhibitor for styrene distillation.

[0004] In the synthesis process of DNBP, 2-sec-butylphenol and nitric acid are generally used as raw materials, and acidic catalysts such as sulfuric acid and methanesulfonic acid are mostly used as catalysts. Unreacted nitric acid and catalysts usually remain in the synthesized crude DNBP, and acidic impurities need to be removed by alkali washing and water washing. DNBP has strong biological toxicity and will inactivate water treatment bacteria. Therefore, wastewater containing DNBP cannot be treated by the commonly used biological methods for wastewater treatment, making DNBP wastewater difficult to treat or expensive to treat, thereby significantly increasing the production cost of DNBP. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a post-treatment method for crude acid-containing DNBP. The purity of the DNBP product obtained by the method reaches more than 99%, and zero output of phenol-containing wastewater and zero output of organic waste liquid can be achieved.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a post-treatment method for a crude acid-containing DNBP product, comprising the following steps:

[0008] S1: passing the acidic DNBP crude product through an adsorption column to obtain a neutral DNBP crude product;

[0009] The upper and lower parts of the adsorption column are filled with a dehydration adsorbent, and the middle part of the adsorption column is alternately filled with an acid absorbent and a dehydration adsorbent;

[0010] S2: After mixing the neutral DNBP crude product with the crystallization solvent, programmed cooling crystallization is performed to obtain DNBP solid, which is then washed and dried to obtain pure DNBP.

[0011] Preferably, the acid absorber includes but is not limited to caustic soda flakes.

[0012] Preferably, the dehydration adsorbent includes but is not limited to any one or more of 4A molecular sieve, 13X molecular sieve or activated alumina.

[0013] Preferably, the crystallization solvent includes but is not limited to any one or more of methanol, ethanol, n-propanol, isopropanol or n-butanol.

[0014] Preferably, the programmed cooling crystallization is:

[0015] The cooling rate above 20℃ is ≤5℃ / h; the cooling rate below 20℃ is ≤3℃ / h.

[0016] Preferably, the washing is performed using a crystallization solvent.

[0017] Preferably, the crystallization mother liquor obtained after the programmed cooling crystallization is subjected to distillation treatment to separate the reaction solvent, the crystallization solvent and the DNBP by-product, wherein the reaction solvent and the crystallization solvent are recycled, and the reaction solvent is the solvent used in the process of preparing the crude acid-containing DNBP.

[0018] Preferably, the reaction solvent includes, but is not limited to, any one or more of carbon tetrachloride, ethylene dichloride, dichloropropane, trichloropropane, monochloropentane or monochlorohexane.

[0019] Preferably, the DNBP by-product is purified by programmed temperature-lowering crystallization.

[0020] Preferably, after the crude DNBP is treated according to the above post-treatment method, the purity of the obtained pure DNBP is ≥99%, the free acid content calculated as H2SO4 is ≤0.01%, and the benzene insoluble matter is ≤0.1%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a post-processing method for a crude acid-containing DNBP product. First, the crude acid-containing DNBP product is deacidified by an acid absorber and dehydrated by a dehydrating adsorbent to obtain a crude neutral DNBP product, which is then mixed with a crystallization solvent and subjected to low-temperature recrystallization, refining and purification. The traditional post-processing and refining process of the crude DNBP product of first washing with water and then distilling is abandoned. The refining process is green and environmentally friendly, and no wastewater is generated. The low-temperature recrystallization refining process does not require heating of the nitrate DNBP, thereby avoiding the potential safety hazards caused by the high heat of the nitrate. The crystallization mother liquor obtained by recrystallization can be separated by distillation to obtain a reaction solvent and a crystallization solvent for recycling. At the same time, the DNBP by-product obtained after distillation can be further subjected to low-temperature crystallization and purification after adding a crystallization solvent. Therefore, the post-processing method for the crude DNBP product provided by the present invention can achieve the discharge of zero phenol-containing wastewater and zero organic waste liquid, and belongs to a green and safe refining and purification process for the crude DNBP product, and the steps are simple, and it is easy to achieve large-scale promotion and application.

[0023] After testing, according to the above-mentioned post-treatment method of the crude DNBP product, the purity of the obtained DNBP pure product is ≥99%, the free acid content (calculated as H2SO4) is ≤0.01%, and the benzene insoluble matter is ≤0.1%. All indicators meet the industry requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the liquid chromatogram of the pure DNBP obtained in Example 1;

[0025] Figure 2 This is the liquid chromatogram of the pure DNBP obtained in Example 2;

[0026] Figure 3 This is the liquid chromatogram of the pure DNBP obtained in Example 3;

[0027] Figure 4 This is the liquid chromatogram of the pure DNBP obtained in Example 4. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0029] In the production process of DNBP in the prior art, the residual free acid in DNBP will cause corrosion of downstream equipment pipelines and affect the quality of styrene. In addition, the industry currently requires that the free acid content (in terms of H2SO4) of 70% of the DNBP ethylbenzene solution is ≤0.01%, and the benzene insoluble matter is ≤0.1%. Therefore, the crude DNBP product needs to be firstly alkali-washed to remove the residual free acid in the reaction to ensure that the free acid of the DNBP product is qualified, and then washed with water to remove the residual salts to ensure that the benzene insoluble matter of the DNBP product is qualified. However, the alkali washing and water washing processes will produce a large amount of DNBP-containing wastewater, and DNBP has strong biological toxicity, which makes the wastewater difficult to treat or the treatment cost is expensive. Based on this, the present invention provides a post-treatment method for a crude acid-containing DNBP product, comprising the following steps:

[0030] S1: passing the acidic DNBP crude product through an adsorption column to obtain a neutral DNBP crude product;

[0031] The upper and lower parts of the adsorption column are filled with a dehydration adsorbent, and the middle part of the adsorption column is alternately filled with an acid absorbent and a dehydration adsorbent;

[0032] S2: After mixing the neutral DNBP crude product with the crystallization solvent, programmed cooling crystallization is performed to obtain DNBP solid, which is then washed and dried to obtain pure DNBP.

[0033] In the present invention, the crude acid-containing DNBP can be prepared by technical means well known to those skilled in the art. Specifically, in some embodiments of the present invention, the crude acid-containing DNBP is obtained by mixing nitric acid, a reaction solvent and 2-sec-butylphenol and reacting them. Wherein, the reaction solvent includes but is not limited to any one or more of carbon tetrachloride, ethylene dichloride, dichloropropane, trichloropropane, monochloropentane or monochlorohexane. The reaction temperature is 20~90°C, preferably 30~60°C; the time is 6~12 h, preferably 7~10 h. Furthermore, a catalyst can also be added to the reaction to increase the reaction rate and reduce the reaction temperature. The catalyst can be selected from acidic catalysts such as sulfuric acid and methanesulfonic acid.

[0034] In other embodiments of the present invention, if no reaction solvent is added in the synthesis of the crude acid-containing DNBP, the reaction solvent can be added to the crude DNBP obtained after liquid separation to improve the kinematic viscosity of the crude DNBP so that it can pass smoothly through the adsorption column.

[0035] In some specific embodiments of the present invention, concentrated nitric acid and a reaction solvent, monochlorobutane, are preferably mixed in an ice-water bath, 2-sec-butylphenol is slowly added dropwise using a dropping funnel, and after the addition is completed, the temperature is slowly raised, and the reaction is carried out at normal pressure and 20-90° C. for 6-12 h. After the reaction is completed, the mixture is allowed to stand and separate into layers, and the organic phase is the crude acid-containing DNBP phase.

[0036] After obtaining the crude acid-containing DNBP product, according to the present invention, the crude acid-containing DNBP product is passed through an adsorption column to obtain a crude neutral DNBP product.

[0037] In the present invention, the acid absorber can be an alkaline substance, including but not limited to flake caustic soda; the dehydration adsorbent includes but is not limited to any one or more of 4A molecular sieve, 13X molecular sieve or activated alumina.

[0038] It should be noted that the upper and lower parts of the adsorption column are filled with dehydration adsorbents to better absorb water and provide support. Generally, acid absorbers, such as the above-mentioned caustic soda flakes, will inevitably become hardened over time during use, resulting in a reduction in their service life. Therefore, the present invention preferably alternately fills the acid absorber and the dehydration adsorbent in the middle of the adsorption column, so that the dehydration adsorbent can support the acid absorber to a certain extent, thereby reducing its hardening. Wherein, during the alternating filling process, the upper and lower positions of the acid absorber and the dehydration adsorbent are not particularly limited.

[0039] The present invention has no particular limitation on the space in the upper, middle and lower parts of the adsorption column. Those skilled in the art can make reasonable settings based on the processing volume of the above-mentioned acid-containing DNBP crude product and the service life of the acid absorber and the dehydration adsorbent.

[0040] In the present invention, after the adsorption column is completed, the free acid content of the obtained product can be measured to determine whether the obtained product is a neutral DNBP crude product.

[0041] In the present invention, the obtained neutral DNBP crude product is preferably mixed with a crystallization solvent and then subjected to programmed cooling crystallization to obtain a DNBP solid, wherein the crystallization solvent includes but is not limited to any one or more of methanol, ethanol, n-propanol, isopropanol or n-butanol, preferably methanol.

[0042] In the present invention, if the cooling rate of the programmed cooling crystallization is too fast, the crystal form of the obtained DNBP product will not meet the requirements, and impurities will be contained in the product, while if the cooling rate is too low, the crystallization period will be long and the energy consumption will be high. Therefore, in summary, the present invention preferably has the programmed cooling crystallization as follows: the cooling rate above 20°C is ≤5°C / h; the cooling rate below 20°C is ≤3°C / h.

[0043] In some embodiments of the present invention, it is preferred to add a crystallization solvent to the neutral DNBP crude product, heat and stir to mix evenly, and then perform programmed cooling crystallization.

[0044] After the programmed cooling crystallization is completed, filtration is performed according to the present invention to obtain DNBP solid.

[0045] Furthermore, the DNBP solid was washed and dried to obtain pure DNBP.

[0046] In some embodiments of the present invention, the washing preferably uses a crystallization solvent to quickly elute the DNBP solid to remove residual impurities on the surface, and then vacuum drying is performed to remove the residual solvent to obtain pure DNBP.

[0047] The vacuum drying temperature is below 40° C. and the time is 3 to 5 h.

[0048] After testing, the purity of the DNBP pure product obtained above is ≥99%, the free acid content calculated as H2SO4 is ≤0.01%, and the benzene insoluble matter is ≤0.1%. All indicators meet the industry requirements.

[0049] As a preferred technical solution, after the programmed cooling crystallization is completed, the obtained crystallization mother liquor is subjected to rectification treatment to separate the reaction solvent, the crystallization solvent and the DNBP byproduct, wherein the reaction solvent and the crystallization solvent are recycled. The DNBP byproduct can be further purified by programmed cooling crystallization.

[0050] In summary, the post-treatment method of the acid-containing crude DNBP provided by the present invention abandons the traditional post-treatment refining process of the crude DNBP product of first washing with water and then distilling. After deacidification and dehydration, low-temperature recrystallization is performed. The refining process is green and environmentally friendly, and no waste water is generated. The process does not require heating of the nitrated DNBP, avoiding the safety hazards caused by the high heat of the nitrated product. The crystallization mother liquor obtained by recrystallization can be separated into a reaction solvent and a crystallization solvent for recycling after distillation. At the same time, the DNBP by-product obtained after distillation can be further purified by low-temperature crystallization after adding a crystallization solvent.

[0051] Therefore, the post-treatment method of the crude DNBP provided by the present invention can achieve the discharge of zero phenol-containing wastewater and zero organic waste liquid, and is a green and safe refining and purification process for the crude DNBP product, and the steps are simple and easy to achieve large-scale promotion and application.

[0052] In order to further illustrate the present invention, the following examples are provided for detailed description. The experimental raw materials used in the following examples of the present invention are generally commercially available products.

[0053] Example 1

[0054] In an ice-water bath, 166.8 g of concentrated nitric acid, 15.0 g of methanesulfonic acid, and 40.0 g of monochlorobutane, a reaction solvent, were mixed. 60.2 g of 2-sec-butylphenol was slowly added dropwise using a dropping funnel. After the addition was completed, the temperature was slowly raised. The reaction was carried out at normal pressure and 60°C for 6 hours. After the reaction was completed, the mixture was allowed to stand and separate into layers. The organic phase was the crude acid-containing DNBP phase.

[0055] The acidic DNBP crude product is slowly passed through the adsorption column to obtain the neutral DNBP crude product. The adsorption column is filled with caustic soda flakes and 4A molecular sieves alternately up and down. The upper and lower parts are filled with 4A molecular sieves as support, while absorbing moisture in the system.

[0056] Add 40.0 g of crystallization solvent n-butanol to the neutral DNBP crude product, heat and stir at 50°C to mix evenly, then perform programmed cooling and crystallization. The cooling rate is 5°C / h above 20°C and 2°C / h below 20°C. Filter and separate the DNBP solid, quickly rinse with crystallization solvent n-butanol to remove residual impurities on the surface, and vacuum dry at below 40°C for 3 h to remove residual solvent to obtain 72.8 g of pure DNBP in the form of bright yellow crystals. The pure DNBP was tested, and the DNBP content was 99.2%, the free acid content (in terms of H2SO4) was 0.005%, and the benzene insoluble matter was 0.08%. The liquid chromatogram of the pure DNBP is shown as follows. Figure 1 shown.

[0057] The crystallization mother liquor is separated into reaction solvent monochlorobutane, crystallization solvent n-butanol, and DNBP byproduct by distillation. The reaction solvent and crystallization solvent can be recycled, and the DNBP byproduct can be further purified by low-temperature crystallization by adding the crystallization solvent.

[0058] Example 2

[0059] Mix 166.8 g of concentrated nitric acid and 40.0 g of monochloropentane, a reaction solvent, in an ice-water bath, and slowly add 60.2 g of 2-sec-butylphenol using a dropping funnel. After the addition is complete, slowly increase the temperature and react at normal pressure and 80°C for 9 hours. After the reaction is completed, allow to stand and separate into layers, and the organic phase is the crude acid-containing DNBP phase.

[0060] The acidic DNBP crude product is slowly passed through an adsorption column to obtain a neutral DNBP crude product. The adsorption column is filled with caustic soda flakes and activated alumina alternately, and the upper and lower parts are filled with activated alumina as a support, while absorbing moisture in the system.

[0061] Add 25.0 g of methanol, a crystallization solvent, to the neutral DNBP crude product, heat and stir at 50°C to mix evenly, then perform programmed cooling and crystallization. The cooling rate above 20°C is 4°C / h, and the cooling rate below 20°C is 1°C / h. Filter and separate the DNBP solid, quickly rinse with methanol, a crystallization solvent, to remove residual impurities on the surface, and vacuum dry at below 40°C for 4 h to remove the residual solvent to obtain 73.4 g of pure DNBP in the form of bright yellow crystals. The pure DNBP was tested, and the DNBP content was 99.9%, the free acid content (in terms of H2SO4) was 0.005%, and the benzene insoluble matter was 0.05%. The liquid chromatogram of the pure DNBP is shown below Figure 2 shown.

[0062] The crystallization mother liquor is separated into reaction solvent monochloropentane, crystallization solvent methanol and DNBP byproduct by distillation. The reaction solvent and crystallization solvent can be recycled, and the DNBP byproduct can be further purified by low-temperature crystallization by adding the crystallization solvent.

[0063] Example 3

[0064] In an ice-water bath, 166.8 g of concentrated nitric acid, 40.0 g of concentrated sulfuric acid, and 40.0 g of monochlorohexane, a reaction solvent, were mixed, and 60.2 g of 2-sec-butylphenol was slowly added dropwise using a dropping funnel. After the addition was completed, the temperature was slowly raised, and the reaction was carried out at normal pressure and 80°C for 6 hours. After the reaction was completed, the mixture was allowed to stand and separate into layers, and the organic phase was the crude acid-containing DNBP phase.

[0065] The acidic DNBP crude product is slowly passed through an adsorption column to obtain a neutral DNBP crude product. The adsorption column is filled with caustic soda flakes and 4A molecular sieves alternately, and the upper and lower parts are filled with 13X molecular sieves as support, while absorbing moisture in the system.

[0066] Add 40.0 g of crystallization solvent ethanol to the neutral DNBP crude product, heat and stir at 50°C to mix evenly, then perform programmed cooling and crystallization. The cooling rate is 5°C / h above 20°C and 1.5°C / h below 20°C. Filter and separate the DNBP solid, quickly rinse with crystallization solvent ethanol to remove residual impurities on the surface, and vacuum dry at below 40°C for 3 h to remove residual solvent to obtain 72.5 g of pure DNBP. The product is bright yellow crystals. The pure DNBP was tested, and the DNBP content was 99.8%, the free acid content was 0.005% (in terms of H2SO4), and the benzene insoluble matter was 0.06%. The liquid chromatogram of the pure DNBP is shown as follows. Figure 3 shown.

[0067] The crystallization mother liquor is separated into reaction solvent monochlorohexane, crystallization solvent ethanol, and DNBP byproduct by distillation. The reaction solvent and crystallization solvent can be recycled, and the DNBP byproduct is added to the crystallization solvent for further low-temperature crystallization purification.

[0068] Example 4

[0069] In an ice-water bath, 166.8 g of concentrated nitric acid, 15.0 g of methanesulfonic acid, and 40.0 g of monochlorobutane, a reaction solvent, were mixed. 60.2 g of 2-sec-butylphenol was slowly added dropwise using a dropping funnel. After the addition was completed, the temperature was slowly raised. The reaction was carried out at normal pressure and 60°C for 6 hours. After the reaction was completed, the mixture was allowed to stand and separate into layers. The organic phase was the crude acid-containing DNBP phase.

[0070] The acidic DNBP crude product is slowly passed through an adsorption column to obtain a neutral DNBP crude product. The adsorption column is filled with caustic soda flakes and 4A molecular sieves alternately, and the upper and lower parts are filled with 4A molecular sieves as support, while absorbing moisture in the system.

[0071] Add 40.0 g of crystallization solvent n-butanol to the neutral DNBP crude product, heat and stir at 50°C to mix evenly, then perform programmed cooling and crystallization. The cooling rate is 10°C / h above 20°C and 5°C / h below 20°C. Filter and separate the DNBP solid, quickly rinse with crystallization solvent n-butanol to remove residual impurities on the surface, and vacuum dry at below 40°C for 5 h to remove residual solvent to obtain 75.4 g of pure DNBP. The product is in the form of a yellow solid. The pure DNBP was tested, and the DNBP content was 98.8%, the free acid content (in terms of H2SO4) was 0.006%, and the benzene insoluble matter was 0.09%. The liquid chromatogram of the pure DNBP is shown as follows. Figure 4 shown.

[0072] The crystallization mother liquor is separated into the reaction solvent monochlorobutane, the crystallization solvent n-butanol, and the DNBP byproduct by distillation. The reaction solvent and the crystallization solvent can be recycled, and the DNBP byproduct is further purified by low-temperature crystallization by adding the crystallization solvent.

[0073] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A post-treatment method for crude acid-containing DNBP, characterized in that: The following steps are involved: S1: passing the acidic DNBP crude product through an adsorption column to obtain a neutral DNBP crude product; The upper and lower parts of the adsorption column are filled with a dehydration adsorbent, and the middle part of the adsorption column is alternately filled with an acid absorbent and a dehydration adsorbent; S2: After mixing the neutral DNBP crude product with the crystallization solvent, programmed cooling crystallization is performed to obtain DNBP solid, which is then washed and dried to obtain pure DNBP.

2. The post-processing method according to claim 1, characterized in that: The acid absorber includes but is not limited to flake caustic soda.

3. The post-processing method according to claim 1 or 2, characterized in that: The dehydration adsorbent includes but is not limited to any one or more of 4A molecular sieve, 13X molecular sieve or activated alumina.

4. The post-processing method according to any one of claims 1 to 3, characterized in that: The crystallization solvent includes, but is not limited to, any one or more of methanol, ethanol, n-propanol, isopropanol or n-butanol.

5. The post-processing method according to any one of claims 1 to 4, characterized in that: The programmed cooling crystallization is: The cooling rate above 20℃ is ≤5℃ / h; the cooling rate below 20℃ is ≤3℃ / h.

6. The post-processing method according to any one of claims 1 to 5, characterized in that: The washing is carried out using a crystallization solvent.

7. The post-processing method according to any one of claims 1 to 6, characterized in that: The crystallization mother liquor obtained after the programmed cooling crystallization is subjected to rectification treatment to separate the reaction solvent, the crystallization solvent and the DNBP by-product, wherein the reaction solvent and the crystallization solvent are recycled; The reaction solvent is the solvent used in the process of preparing the crude acid-containing DNBP.

8. The post-processing method according to any one of claims 1 to 7, characterized in that: The reaction solvent includes, but is not limited to, any one or more of carbon tetrachloride, ethylene dichloride, dichloropropane, trichloropropane, monochloropentane or monochlorohexane.

9. The post-processing method according to any one of claims 1 to 8, characterized in that: The DNBP byproduct is purified by programmed temperature-lowering crystallization.

10. The post-processing method according to any one of claims 1 to 9, characterized in that: The purity of the DNBP pure product is ≥99%, the free acid content calculated as H2SO4 is ≤0.01%, and the benzene insoluble matter is ≤0.1%.

Images