System and process for purifying diamino maleic dinitrile crude product

Abstract

The invention discloses a system and a process for purifying a diamino maleic dinitrile crude product, and relates to the technical field of purification, the system comprises a crystallization centrifugal assembly, an impurity removal centrifugal assembly and a crude product dryer; the impurity removal centrifugal assembly comprises a reflux impurity removal kettle communicated with a discharge hole of the first centrifugal machine, a second centrifugal machine communicated with a material outlet of the reflux impurity removal kettle, a reflux condenser communicated with an air outlet of the reflux impurity removal kettle, and an impurity removal solvent metering tank respectively communicated with the second centrifugal machine and the reflux impurity removal kettle; the impurity removal solvent temporary storage tank is communicated with a liquid outlet of the second centrifugal machine; and the crude product dryer is communicated with a discharge hole of the second centrifugal machine. The device is compact and reasonable in design, can effectively remove hydrocyanic acid oligomerization impurities, simplifies equipment, reduces operation procedures, improves the operation automation level, and reduces material loss.

Description

Technical Field

[0001] The present invention relates to the technical field of purification, and more specifically to the technical field of a system and process for purifying crude diaminomaleonitrile. Background Art

[0002] Diaminomaleonitrile is also called diaminomaleonitrile, which is a stable tetramer of hydrocyanic acid and is also known as an important precursor for synthesizing nitrogen-containing cyclic compounds such as imidazole, pyrazine and purine. One preparation method of diaminomaleonitrile is to use a catalyst not limited to one type in the presence of an organic solvent, control the reaction temperature and pressure to make hydrocyanic acid undergo polymerization reaction, and obtain diaminomaleonitrile. After the polymerization reaction of diaminomaleonitrile is completed, the added catalyst and the oligomeric impurities generated by the reaction need to be separated in time in the polymerization reaction solution, and the first crude product purification of diaminomaleonitrile is carried out. Existing patents disclose the following technology:

[0003] The patent with publication number US3839406 discloses the following content: a method for preparing diaminomaleic dinitrile comprising the following steps: diluting the solution with hot water after the polymerization is completed, and removing the black amorphous polymer by filtering. No further treatment measures and corresponding equipment schemes are taken for the oligomeric impurities of hydrocyanic acid having similar solubility characteristics to diaminomaleic dinitrile in the mixed system.

[0004] The patent with the publication number of JP59116254 discloses the following content: a method for preparing diaminomaleic dinitrile by polymerization of hydrogen cyanide under the action of an alkali catalyst and a sulfur-containing auxiliary agent, wherein the separation of the reaction product is to use a high-performance evaporation device such as a rotary evaporator to evaporate the solvent under vacuum, collect the residual solid, and after crushing, use acetonitrile, ethyl acetate, toluene, etc. to dissolve and filter to remove insoluble impurities, and the solution is crystallized and separated to obtain the finished diaminomaleic dinitrile. Since diaminomaleic dinitrile is easy to polymerize again to form a high polymer under a heated state, the solvent can be separated and recycled during the solution concentration process, but the product is easy to deteriorate and lose under a heated state, and the solid formed after evaporation has not been free of impurities, the diaminomaleic dinitrile content in the crude product is low, and the solid formed by evaporation and concentration is difficult to collect and crush.

[0005] In the method for producing diaminomaleic dinitrile disclosed in the above patent, oligomeric impurities of hydrocyanic acid are not effectively removed. In order to further remove oligomeric impurities of hydrocyanic acid in the crude product, it is necessary to design a system for purifying the crude diaminomaleic dinitrile. Summary of the invention

[0006] The purpose of the present invention is to solve the above technical problems and provide a system and process for purifying crude diaminomaleonitrile.

[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0008] The first aspect of the present invention provides a system for purifying a crude diaminomaleonitrile, comprising a crystallization centrifugal assembly, an impurity removal centrifugal assembly, and a crude product dryer which are sequentially arranged using a height difference;

[0009] The crystallization centrifugal assembly comprises a crude product crystallization tank, a first centrifuge connected to a discharge port at the bottom of the crude product crystallization tank, a crystallization condenser connected to a gas outlet at the top of the crude product crystallization tank, and a centrifugal solvent temporary storage tank connected to a liquid outlet of the first centrifuge;

[0010] The impurity removal centrifugal assembly includes a reflux impurity removal kettle connected to the material outlet of the first centrifuge, a second centrifuge connected to the material outlet of the reflux impurity removal kettle, a reflux condenser connected to the gas outlet of the reflux impurity removal kettle, an impurity removal solvent metering tank connected to the reflux impurity removal kettle, and an impurity removal solvent temporary storage tank connected to the liquid outlet of the second centrifuge;

[0011] The crude product dryer is communicated with the discharge port of the second centrifuge.

[0012] In one embodiment, the crude product crystallization tank includes a tank body, a crystallization material liquid inlet arranged at the top of the tank body, a crystallization gas outlet arranged at the top of the tank body, a crystallization material liquid outlet arranged at the bottom of the tank body, a stirring mechanism arranged in the tank body, and a driving motor arranged at the top of the tank body to drive the stirring mechanism to rotate. The tank body includes an inner shell and an outer shell, and the inner shell and the outer shell form a temperature control cavity. The outer shell is provided with a chilled water inlet pipe and a chilled water outlet pipe connected to the interior of the temperature control cavity.

[0013] In one embodiment, the crystallization condenser includes a condenser body, a condensation air inlet disposed at one end of the condenser body and communicating with the crystallization air outlet, and a condensation air outlet disposed at the other end of the condenser body and communicating with the atmosphere.

[0014] In one embodiment, the first centrifuge includes a centrifuge body, a centrifuge feed port disposed at the top of the centrifuge body, a centrifuge discharge port disposed at the bottom of the centrifuge body, and a centrifuge liquid outlet disposed at the bottom of the side wall of the centrifuge body;

[0015] The centrifugal feed port is connected to the crystallization material outlet and the desalted water main pipe respectively;

[0016] The centrifugal discharge port is connected to the reflux impurity removal kettle;

[0017] The centrifugal liquid outlet is connected with the centrifugal solvent temporary storage tank and the washing water temporary storage tank pipeline, and the liquid outlet of the washing water temporary storage tank is connected with the top of the tank body of the crude product crystallization tank through a pipeline.

[0018] In one embodiment, the centrifugal solvent temporary storage tank includes a centrifugal solvent temporary storage shell, a centrifugal solvent temporary storage liquid outlet provided at the bottom of the centrifugal solvent temporary storage shell, a centrifugal solvent temporary storage liquid inlet provided at the top of the centrifugal solvent temporary storage shell, and a centrifugal solvent temporary storage gas outlet provided at the top of the centrifugal solvent temporary storage shell.

[0019] In one embodiment, the structure of the reflux condenser is the same as that of the crystallization condenser.

[0020] In one embodiment, the reflux impurity removal kettle comprises an impurity removal kettle body, a filter cake feeding port, an impurity removal gas outlet and an impurity removal liquid inlet all arranged at the top of the impurity removal kettle body, an impurity removal material liquid outlet arranged at the bottom of the impurity removal kettle body, a stirring component arranged in the impurity removal kettle body, and a driving mechanism arranged at the top of the impurity removal kettle body to drive the stirring component to rotate;

[0021] The impurity removal liquid inlet is connected to the impurity removal solvent metering tank;

[0022] The impurity removal gas outlet is connected to the reflux condenser;

[0023] The filter cake feeding port is connected with the centrifugal discharge port;

[0024] The impurity-removing material liquid outlet is connected to the second centrifuge;

[0025] The impurity removal kettle body is a double-layer shell, which surrounds a temperature control cavity. The double-layer shell is provided with a circulating water inlet pipe and a circulating water outlet pipe connected to the interior of the temperature control cavity, and is also provided with a low-pressure steam inlet and a steam condensate outlet connected to the interior of the temperature control cavity.

[0026] In one embodiment, the structure of the second centrifuge is the same as that of the first centrifuge, and the centrifugal feed port of the second centrifuge is respectively connected to the impurity removal material outlet and the desalted water rinsing pipeline;

[0027] The centrifugal liquid outlet of the second centrifuge is respectively connected to the pipelines of the impurity removal solvent temporary storage tank and the washing water temporary storage tank;

[0028] The centrifugal discharge port of the second centrifuge is connected to the crude product dryer;

[0029] The structure of the impurity removal solvent metering tank is the same as that of the centrifugal solvent temporary storage tank.

[0030] In one embodiment, the crude product dryer includes a single cone dryer shell, a single cone feed port disposed at the top of the single cone dryer shell, and a single cone discharge port disposed at the bottom of the single cone dryer shell, and also includes a venting outlet disposed at the top of the single cone dryer shell.

[0031] In one embodiment, a material spiral rotating heating assembly having a heating chamber is disposed inside the single cone dryer housing, and a drying hot water inlet and a drying hot water outlet communicating with the heating chamber are disposed on the single cone dryer housing.

[0032] Another aspect of the present invention provides a process for purifying a crude diaminomaleic dinitrile, using the above-mentioned system for purifying a crude diaminomaleic dinitrile, comprising the following steps:

[0033] S1. Adding dimethylformamide as solvent, a base catalyst and a catalyst promoter in a quantitative manner into a reaction vessel, controlling the reaction temperature and pressure, and adding hydrocyanic acid to carry out a polymerization reaction. The generated diaminomaleonitrile will continue to polymerize under continuous heating conditions, resulting in a low yield of the target product.

[0034] S2. By controlling the reaction time, when the polymerization reaction reaches the end point, the polymerization reaction liquid is added into pre-cooled desalted water, stirred and cooled to 5° C., and crystallized;

[0035] S3, after the crystallization liquid is fully precipitated with crystals, centrifugation is performed, and the centrifugal filter cake is rinsed with desalted water to remove water-soluble impurities to obtain a crude product;

[0036] S4. Put the impurity removal solvent and crude product into the reflux impurity removal tank, stir and heat, cool and then centrifuge and wash to obtain a wet crude product;

[0037] S5. The primary wet crude product mainly contains diaminosuccinic acid dinitrile and insoluble polymers after drying. The target product is obtained through the following secondary purification operation, which is as follows: dissolve diaminosuccinic acid dinitrile in an organic solvent such as ethanol or acetonitrile under heating to below the boiling point, filter to remove polymer impurities, cool the filtrate, crystallize it by centrifugation, and finally dry it to obtain the product.

[0038] Working principle:

[0039] In this scheme, the diaminomaleic dinitrile polymerization reaction liquid is transferred to a crystallization tank, water is added, stirred, cooled, and crystallized, and then centrifuged and washed with water in a crude centrifuge. The obtained crude crystal product is transferred to a reflux impurity removal kettle, and an impurity removal solvent is added to heat and dissolve and keep warm, and then the temperature is reduced, and then it is placed in an impurity removal centrifuge for centrifugation. After the centrifugation is completed, the impurity removal solvent remaining in the centrifuged solid is washed with desalted water, and then the centrifuged solid is manually transferred to a crude product drying room for drying to obtain a primary diaminomaleic dinitrile crude product.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1. The present invention has a reasonable design. During the production process, the crude crystal product is transported to a reflux impurity removal kettle, and an impurity removal solvent is added to heat up for dissolution and insulation, and then the temperature is lowered. Then, the product is placed in an impurity removal centrifuge for centrifugation. After the centrifugation is completed, the impurity removal solvent remaining in the centrifuged solid material is washed with desalted water, which can effectively remove oligomeric impurities of hydrocyanic acid. In addition, the solid material is rinsed with desalted water, and the solid material contains less impurity removal solvent. This solution has the advantages of less drying solvent loss, reduced production cost, environmental protection, shorter drying time, and reduced energy consumption.

[0042] 2. The present invention has a compact and reasonable design, simplifies the equipment, reduces the operating procedures, and improves the automation of operation; reduces the material loss and safety risks caused by leakage caused by multi-device material transfer, reduces the investment in equipment such as machines and pumps, and reduces the land occupation of factory buildings.

[0043] 3. Based on the heat-sensitive characteristics of the material during processing, the equipment layout makes full use of the height difference, the equipment is compactly connected, and the material flow is smooth, reducing product loss caused by the material retention time and the maintenance safety risks brought about. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 It is a schematic diagram of the structure of the present invention;

[0046] Figure 2 It is a structural schematic diagram of a crude product crystallization tank;

[0047] Figure 3 is a schematic structural diagram of a first centrifuge;

[0048] Figure 4 It is a structural schematic diagram of a centrifugal solvent temporary storage tank;

[0049] Figure 5 It is a structural schematic diagram of a reflux impurity removal kettle;

[0050] Figure 6 It is a schematic diagram of the structure of the crude product dryer;

[0051] Reference numerals: 1-crystallization condenser, 2-crude product crystallization tank, 3-first centrifuge, 4-centrifugal solvent temporary storage tank, 5-reflux condenser, 6-impurity removal solvent metering tank, 7-reflux impurity removal kettle, 8-second centrifuge, 9-impurity removal solvent temporary storage tank, 10-crude product dryer;

[0052] 21-driving motor, 22-crystallization material inlet, 23-inner shell, 24-outer shell, 25-stirring mechanism, 26-crystallization material outlet, 27-chilled water inlet pipe, 28-chilled water outlet pipe, 29-crystallization gas outlet;

[0053] 31-centrifuge body, 32-centrifuge discharge port, 33-centrifuge liquid outlet, 34-centrifuge feed port, 35-desalted water main pipe, 36-wash water temporary storage tank pipeline;

[0054] 41-centrifugal solvent temporary storage liquid inlet, 42-centrifugal solvent temporary storage gas outlet, 43-centrifugal solvent temporary storage shell, 44-centrifugal solvent temporary storage liquid outlet;

[0055] 71-driving mechanism, 72-impurity removal liquid inlet, 73-impurity removal kettle body, 74-stirring assembly, 75-impurity removal material liquid outlet, 76-circulating water liquid inlet pipe, 77-filter cake feeding port, 78-impurity removal gas outlet, 79-circulating water liquid outlet pipe;

[0056] 101- single cone dryer housing, 102- single cone feed port, 103- vent outlet, 104- drying hot water inlet, 105- single cone discharge port, 106- drying hot water outlet. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0058] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0059] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0060] In the description of the embodiments of the present invention, it should be noted that the terms "inside", "outside", "upper", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0061] Example 1

[0062] like Figures 1 to 6 As shown, this embodiment provides a system for purifying a crude diaminomaleic dinitrile, comprising a crystallization centrifugal assembly, an impurity removal centrifugal assembly, and a crude product dryer 10 which are arranged in sequence;

[0063] The crystallization centrifugal assembly comprises a crude product crystallization tank 2, a first centrifuge 3 connected to the discharge port at the bottom of the crude product crystallization tank 2, a crystallization condenser 1 connected to the gas outlet at the top of the crude product crystallization tank 2, and a centrifugal solvent temporary storage tank 4 connected to the liquid outlet of the first centrifuge 3;

[0064] The impurity removal centrifugal assembly includes a reflux impurity removal kettle 7 connected to the discharge port of the first centrifuge 3, a second centrifuge 8 connected to the material outlet of the reflux impurity removal kettle 7, a reflux condenser 5 connected to the gas outlet of the reflux impurity removal kettle 7, an impurity removal solvent metering tank 6 connected to the reflux impurity removal kettle 7, and an impurity removal solvent temporary storage tank 9 connected to the liquid outlet of the second centrifuge 8;

[0065] The crude product dryer 10 is communicated with the discharge port of the second centrifuge 8 .

[0066] The crude product crystallization tank 2 includes a tank body, a crystallization material inlet 22 arranged at the top of the tank body, a crystallization gas outlet 29 arranged at the top of the tank body, a crystallization material outlet 26 arranged at the bottom of the tank body, a stirring mechanism 25 arranged in the tank body, and a driving motor 21 arranged at the top of the tank body to drive the stirring mechanism 25 to rotate. The tank body includes an inner shell 23 and an outer shell 24, and the inner shell 23 and the outer shell 24 form a temperature control cavity. The outer shell 24 is provided with a chilled water inlet pipe 27 and a chilled water outlet pipe 28 connected to the inside of the temperature control cavity.

[0067] The crystallization condenser 1 includes a condenser body, a condensation air inlet disposed at one end of the condenser body and communicating with the crystallization air outlet 29 , and a condensation air outlet disposed at the other end of the condenser body and communicating with the atmosphere.

[0068] The first centrifuge 3 includes a centrifuge body 31, a centrifuge feed port 34 disposed at the top of the centrifuge body 31, a centrifuge discharge port 32 disposed at the bottom of the centrifuge body 31, and a centrifuge liquid outlet 33 disposed at the bottom of the side wall of the centrifuge body 31;

[0069] The centrifugal feed port 34 is connected to the crystallization material outlet 26 and the desalted water main 35 respectively;

[0070] The centrifugal discharge port 32 is connected to the reflux impurity removal kettle 7;

[0071] The centrifugal liquid outlet is connected to the centrifugal solvent temporary storage tank 4 and the washing water temporary storage tank pipeline 36, and the washing water temporary storage tank pipeline 36 is connected to the top of the tank body of the crude product crystallization tank 2.

[0072] The centrifugal solvent temporary storage tank 4 includes a centrifugal solvent temporary storage shell 43, a centrifugal solvent temporary storage liquid outlet 44 arranged at the bottom of the centrifugal solvent temporary storage shell 43, a centrifugal solvent temporary storage liquid inlet 41 arranged at the top of the centrifugal solvent temporary storage shell 43, and a centrifugal solvent temporary storage gas outlet 42 arranged at the top of the centrifugal solvent temporary storage shell 43.

[0073] The structure of the reflux condenser 5 is the same as that of the crystallization condenser 1 .

[0074] The reflux impurity removal kettle 7 comprises an impurity removal kettle body 73, a filter cake feeding port 77, an impurity removal gas outlet 78 and an impurity removal liquid inlet 72 all arranged at the top of the impurity removal kettle body 73, an impurity removal material liquid outlet 75 arranged at the bottom of the impurity removal kettle body 73, a stirring assembly 74 arranged in the impurity removal kettle body 73, and a driving mechanism 71 arranged at the top of the impurity removal kettle body 73 to drive the stirring assembly 74 to rotate;

[0075] The impurity removal liquid inlet is connected to the impurity removal solvent metering tank 6;

[0076] The impurity removal gas outlet 78 is connected to the reflux condenser 5;

[0077] The filter cake feeding port 77 is connected to the centrifugal discharge port 32;

[0078] The impurity-removing material outlet 75 is connected to the second centrifuge 8;

[0079] The impurity removal kettle body 73 is a double-layer shell, which encloses a temperature control cavity. The double-layer shell is provided with a circulating water inlet pipe 76 and a circulating water outlet pipe 79 connected to the interior of the temperature control cavity, and is also provided with a low-pressure steam inlet and a steam condensate outlet connected to the interior of the temperature control cavity.

[0080] The structure of the second centrifuge 8 is the same as that of the first centrifuge 3. The centrifugal feed port 34 of the second centrifuge 8 is connected to the impurity removal material outlet 75 and the impurity removal solvent metering tank 6 respectively;

[0081] The centrifugal outlet of the second centrifuge 8 is connected to the temporary storage tank 9 for the impurity removal solvent and the desalted water rinsing pipeline respectively;

[0082] The centrifugal discharge port 32 of the second centrifuge 8 is connected to the crude product dryer 10;

[0083] The structure of the impurity removal solvent metering tank 6 is the same as that of the centrifugal solvent temporary storage tank 4 .

[0084] The crude product dryer 10 includes a single cone dryer housing 101, a single cone feed port 102 disposed at the top of the single cone dryer housing 101, and a single cone discharge port 105 disposed at the bottom of the single cone dryer housing 101, and also includes a venting outlet 103 disposed at the top of the single cone dryer housing 101.

[0085] A material spiral rotating heating assembly having a heating chamber is arranged inside the single cone dryer housing 101 , and a drying hot water inlet 104 and a drying hot water outlet 106 communicating with the heating chamber are arranged on the single cone dryer housing 101 .

[0086] Example 2

[0087] A process for purifying crude diaminomaleonitrile is as follows:

[0088] The solvent dimethylformamide, the base catalyst and the catalytic aid are quantitatively added into the reaction container, the reaction temperature and pressure are controlled, and hydrocyanic acid is added to carry out polymerization reaction. The generated diaminomaleic dinitrile will continue to polymerize under continuous heating conditions, resulting in a low yield of the target product. By controlling the reaction time, when the polymerization reaction reaches the end point, the polymerization reaction liquid is added into pre-cooled desalted water, stirred and cooled to 5°C for crystallization. After the crystallization liquid is fully precipitated, the crystal is centrifuged, and the centrifugal filter cake is rinsed with desalted water to wash away water-soluble impurities to obtain a crude product; a low-boiling halogenated hydrocarbon solvent, preferably an aliphatic chlorinated hydrocarbon, including dichloromethane, 1,1-dichloroethane, and 1,2-dichloroethane, is selected as an impurity removal solvent to remove oligomers and catalytic aids in the crude product; the impurity removal solvent and the crude product are placed in a reflux impurity removal tank, stirred and heated, and centrifuged after cooling to obtain a wet crude product. After drying, the wet crude product mainly contains diaminosuccinic acid dinitrile and insoluble polymers. The target product is obtained through the following secondary purification operation, which is as follows: using an organic solvent such as ethanol or acetonitrile to dissolve diaminosuccinic acid dinitrile in a state heated to below the boiling point, filtering to remove polymer impurities, cooling the filtrate, crystallizing, centrifuging, and finally drying to obtain the product. The commonly used base catalyst in this reaction is sodium hydroxide, and the commonly used catalytic aid is diphenyl disulfide.

[0089] Selecting cooled water as a reaction blocking agent and crude product precipitation solvent has the following effects: first, the polymerization reaction cannot continue under the condition of rapid temperature reduction and the presence of water, so that the reaction can be quickly terminated; second, the diaminosuccinic acid dinitrile, polymer and catalytic aid generated by the polymerization reaction are quickly precipitated into particles; third, compared with other materials used for reaction blocking and product precipitation, desalted water has the advantages of low cost and environmental friendliness.

[0090] After selecting cooled water as a reaction blocker and a solvent for the crude product precipitation, the catalyst promoter will precipitate in the mixed solvent along with the target product, making it difficult to obtain qualified products in the subsequent secondary purification. The selection of low-boiling-point halogenated hydrocarbon solvents has the following effects: First, it can fully dissolve the residual catalytic promoter without dissolving the product, and fully remove impurities while maintaining low product loss, which is beneficial to improving product quality; second, the qualified primary crude product treated by the above process can meet the long-term circulation of the purified crystallization mother liquor in the secondary purification; third, low-boiling-point halogenated hydrocarbons have good volatility and are easy to recover, which is beneficial to reduce costs while ensuring product quality.

[0091] Example 3

[0092] This embodiment is based on the laboratory data selected in Embodiment 2 as a specific example.

[0093] 280g of desalted water was placed in a 500ml flask and cooled to 5℃ for standby use. 44.08g of dimethylformamide, 0.43g of alkali catalyst and 1.33g of co-catalyst were mixed, heated and stirred, and 38.56g of hydrocyanic acid was added to react at 45℃±5℃ to obtain 84.4g of diaminomaleic dinitrile polymerization reaction liquid. The reaction liquid contained 37.29% of diaminomaleic dinitrile, 2.60% of oligomer content and 1.56% of co-catalyst content by HPLC, and 3.47% of high polymer content by weight method. The reaction liquid was quickly added to the pre-cooled desalted water and stirred for crystallization, and the stirring speed was controlled to 20-30r / min. The crystallized liquid was cooled to 5℃ and kept warm for 4 hours for filtration. The filter cake was washed and filtered with 60g of desalted water to obtain 38.2g of wet filter cake containing water. HPLC determined that the content of diaminomaleic dinitrile was 77.40%, the content of cocatalyst was 2.74%, the content of oligomer was 0.12%, the content of high polymer was 7.3%, and the content of water was 11.3% by weight method. (The solubility of water has a good effect on the removal of oligomers, but a poor effect on the removal of cocatalysts. High polymers are difficult to dissolve in water systems, thus forming the above separation effect) The wet filter cake was transferred to a 500ml flask, 1,2-dichloroethane solvent 120g was added, stirred and heated to 80℃ for 30min, then cooled to 20℃, filtered again, the filter cake was washed with 60g of deionized water and filtered, and the filter cake was dried to obtain 32.2g of a crude product of diaminomaleic dinitrile. Analysis showed that the content of diaminomaleic dinitrile in the crude product was 91.0%, the content of high polymer was 8.4%, the water content was 0.5%, and there were trace amounts of cocatalysts and oligomers.

[0094] In the above process, the reaction conversion rate is 94.9% based on the standard reaction raw material hydrocyanic acid, the reaction selectivity is 86.0% based on diaminomaleic dinitrile, and the reaction process yield is 81.6%. The yield of the reaction liquid treatment and the primary crude product purification process is 93.1%. The main impurities of the primary crude product after purification are insoluble polymers, which meets the requirements of secondary purification.

[0095] Example 4

[0096] This embodiment selects fixed synthesis process parameters for the production device based on Embodiment 2 as a specific example.

[0097] 2800kg of desalted water was placed in a crude crystallization tank and cooled to 5℃ for standby use. 440.8kg of dimethylformamide, 4.3kg of alkaline catalyst and 13.3kg of co-catalyst were mixed, heated and stirred, and 385.6kg of hydrocyanic acid was added to react at 45℃±5℃. After the reaction was completed, the reaction liquid contained 37.35% of diaminomaleic dinitrile, 2.54% of oligomers, and 1.48% of co-catalysts by HPLC. The polymer content was 3.32% by weight method. The reaction liquid was quickly added to the pre-cooled desalted water and stirred for crystallization. The stirring speed was controlled at 20-30r / min. After the crystallization liquid was cooled to 5℃, it was kept warm for 4 hours and centrifuged in the first centrifuge. The centrifugal filtrate was collected in the centrifugal solvent temporary storage tank. After rinsing the filter cake with 60 kg of desalted water, it was transferred to a reflux decontamination kettle pre-added with 1200 kg of 1.2-dichloroethane solvent, stirred and heated to 80°C, then kept warm for 30 minutes, cooled to 20°C, and then centrifuged in a second centrifuge. The centrifugal filtrate was collected in a temporary storage tank for the decontamination solvent. After rinsing the centrifugal filter cake with 60 kg of desalted water, it was placed in a crude product dryer for drying to obtain 318 kg of a primary crude product. Analysis showed that the content of diaminomaleic dinitrile in the primary crude product was 92.0%, the polymer content was 7.4%, the moisture content was 0.5%, and it contained trace amounts of co-catalysts and oligomers.

[0098] In the above process, the reaction conversion rate is 94.6% based on the standard reaction raw material hydrocyanic acid, the reaction selectivity is 86.4% based on diaminomaleic dinitrile, and the reaction process yield is 81.8%. The yield of the reaction liquid treatment and the primary crude product purification process is 92.8%. The main impurities of the primary crude product after purification are insoluble polymers, which meets the requirements of secondary purification.

[0099] Similarly, Examples 5 to 8 are specific examples in which the ratio of the amount of desalted water is adjusted on the basis of Example 4, and the remaining operations are performed in accordance with Example 4.

[0100]

[0101] The test data of Examples 4 to 8 above show that by adjusting the ratio of desalted water to the reaction solution within a certain range, a satisfactory primary crude product can be stably obtained through further treatment. However, too low a water consumption will lead to increased product loss in the mixed solution of DMF and water, and too high a water consumption will lead to increased polymer content.

Claims

1. A system for purifying crude diaminomaleonitrile, characterized in that: It comprises a crystallization centrifugal assembly, an impurity removal centrifugal assembly, and a crude product dryer (10) which are arranged in sequence; The crystallization centrifugal assembly comprises a crude product crystallization tank (2), a first centrifuge (3) connected to a discharge port at the bottom of the crude product crystallization tank (2), a crystallization condenser (1) connected to a gas outlet at the top of the crude product crystallization tank (2), and a centrifugal solvent temporary storage tank (4) connected to a liquid outlet of the first centrifuge (3); The impurity removal centrifugal assembly comprises a reflux impurity removal kettle (7) connected to the material outlet of the first centrifuge (3), a second centrifuge (8) connected to the material outlet of the reflux impurity removal kettle (7), a reflux condenser (5) connected to the gas outlet of the reflux impurity removal kettle (7), an impurity removal solvent metering tank (6) connected to the reflux impurity removal kettle (7), and an impurity removal solvent temporary storage tank (9) connected to the liquid outlet of the second centrifuge (8); The crude product dryer (10) is in communication with the discharge port of the second centrifuge (8).

2. A system for purifying crude diaminomaleonitrile according to claim 1, characterized in that: The crude product crystallization tank (2) comprises a tank body, a crystallization material liquid inlet (22) arranged at the top of the tank body, a crystallization gas outlet (29) arranged at the top of the tank body, a crystallization material liquid outlet (26) arranged at the bottom of the tank body, a stirring mechanism (25) arranged in the tank body, and a driving motor (21) arranged at the top of the tank body to drive the stirring mechanism (25) to rotate, the tank body comprises an inner shell (23) and an outer shell (24), the inner shell (23) and the outer shell (24) enclose a temperature control cavity, and the outer shell (24) is provided with a chilled water inlet pipe (27) and a chilled water outlet pipe (28) connected to the interior of the temperature control cavity.

3. A system for purifying crude diaminomaleonitrile according to claim 2, characterized in that: The crystallization condenser (1) comprises a condenser body, a condensation air inlet arranged at one end of the condenser body and connected to the crystallization air outlet (29), and a condensation air outlet arranged at the other end of the condenser body and connected to the atmosphere.

4. A system for purifying crude diaminomaleonitrile according to claim 3, characterized in that: The first centrifuge (3) comprises a centrifuge body (31), a centrifuge feed port (34) arranged at the top of the centrifuge body (31), a centrifuge discharge port (32) arranged at the bottom of the centrifuge body (31), and a centrifuge liquid outlet (33) arranged at the bottom of the side wall of the centrifuge body (31); The centrifugal feed port (34) is respectively connected to the crystallized material outlet (26) and the desalted water main pipe (35); The centrifugal discharge port (32) is in communication with the reflux impurity removal kettle (7); The centrifugal liquid outlet is in communication with the centrifugal solvent temporary storage tank (4) and the washing water temporary storage tank pipeline (36), and the washing water temporary storage tank pipeline (36) is in communication with the top of the tank body of the crude product crystallization tank (2).

5. A system for purifying crude diaminomaleonitrile according to claim 4, characterized in that: The centrifugal solvent temporary storage tank (4) comprises a centrifugal solvent temporary storage shell (43), a centrifugal solvent temporary storage liquid outlet (44) arranged at the bottom of the centrifugal solvent temporary storage shell (43), a centrifugal solvent temporary storage liquid inlet (41) arranged at the top of the centrifugal solvent temporary storage shell (43), and a centrifugal solvent temporary storage gas outlet (42) arranged at the top of the centrifugal solvent temporary storage shell (43).

6. A system for purifying crude diaminomaleonitrile according to claim 3, characterized in that: The structure of the reflux condenser (5) is the same as that of the crystallization condenser (1).

7. A system for purifying crude diaminomaleonitrile according to claim 5, characterized in that: The reflux impurity removal kettle (7) comprises an impurity removal kettle body (73), a filter cake feeding port (77), an impurity removal gas outlet (78) and an impurity removal liquid inlet (72) all arranged at the top of the impurity removal kettle body (73), an impurity removal material liquid outlet (75) arranged at the bottom of the impurity removal kettle body (73), a stirring component (74) arranged in the impurity removal kettle body (73), and a driving mechanism (71) arranged at the top outside the impurity removal kettle body (73) for driving the stirring component (74) to rotate; The impurity removal liquid inlet is connected to the impurity removal solvent metering tank (6); The impurity removal outlet (78) is in communication with the reflux condenser (5); The filter cake feeding port (77) is in communication with the centrifugal discharge port (32); The impurity-removed material liquid outlet (75) is in communication with the second centrifuge (8); The impurity removal kettle body (73) is a double-layer shell, which encloses a temperature control cavity. The double-layer shell is provided with a circulating water inlet pipe (76) and a circulating water outlet pipe (79) which are connected to the interior of the temperature control cavity, and is also provided with a low-pressure steam inlet and a steam condensate outlet which are connected to the interior of the temperature control cavity.

8. A system for purifying crude diaminomaleonitrile according to claim 7, characterized in that: The structure of the second centrifuge (8) is the same as that of the first centrifuge (3), and the centrifugal feed port (34) of the second centrifuge (8) is respectively connected to the impurity removal material outlet (75) and the desalted water rinsing pipeline; The centrifugal liquid outlet of the second centrifuge (8) is respectively connected to the impurity removal solvent temporary storage tank (9) and the washing water temporary storage tank pipeline (36); The centrifugal discharge port (32) of the second centrifuge (8) is in communication with the crude product dryer (10); The structure of the impurity removal solvent metering tank (6) is the same as that of the centrifugal solvent temporary storage tank (4).

9. A system for purifying crude diaminomaleonitrile according to claim 8, characterized in that: The crude product dryer (10) comprises a single-cone dryer housing (101), a single-cone feed port (102) arranged at the top of the single-cone dryer housing (101), and a single-cone discharge port (105) arranged at the bottom of the single-cone dryer housing (101), and also comprises an air vent (103) arranged at the top of the single-cone dryer housing (101); a material spiral rotating heating component having a heating chamber is arranged inside the single-cone dryer housing (101), and a drying hot water inlet (104) and a drying hot water outlet (106) which are communicated with the heating chamber are arranged on the single-cone dryer housing (101).

10. A process for purifying crude diaminomaleonitrile, using a system for purifying crude diaminomaleonitrile according to any one of claims 1 to 9, characterized in that: The steps include: S1. Adding dimethylformamide as solvent, a base catalyst and a catalyst promoter in a quantitative manner into a reaction vessel, controlling the reaction temperature and pressure, and adding hydrocyanic acid to carry out a polymerization reaction. The generated diaminomaleonitrile will continue to polymerize under continuous heating conditions, resulting in a low yield of the target product. S2. By controlling the reaction time, when the polymerization reaction reaches the end point, the polymerization reaction liquid is added into pre-cooled desalted water, stirred and cooled to 5° C., and crystallized; S3, after the crystallization liquid is fully precipitated with crystals, centrifugation is performed, and the centrifugal filter cake is rinsed with desalted water to remove water-soluble impurities to obtain a crude product; S4. Put the impurity removal solvent and crude product into the reflux impurity removal tank, stir and heat, cool and then centrifuge and wash to obtain a wet crude product; S5. The primary wet crude product mainly contains diaminosuccinic acid dinitrile and insoluble polymers after drying. The target product is obtained through the following secondary purification operation, which is as follows: dissolve diaminosuccinic acid dinitrile in ethanol or acetonitrile under heating below the boiling point, remove polymer impurities through filtration, cool the filtrate, crystallize it by centrifugation, and finally dry it to obtain the product.

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