A method for purifying benzanthrone

Abstract

Benzanthrone is a dye intermediate that can be used to synthesize reduced dyes, such as reduced dark blue, reduced purple, reduced yellow, reduced green, etc. It is usually obtained by reaction with anthraquinone and glycerol as raw materials in the presence of concentrated sulfuric acid and a catalyst. The crude benzanthrone content is generally between 60%-90%. Its content cannot meet the quality requirements of downstream synthesis and commercial applications. The present invention provides a method for purifying crude benzanthrone, specifically using a suitable organic solvent to heat and dissolve the crude benzanthrone, filtering to remove insoluble matter, and the solution is cooled and crystallized to recover benzanthrone, and the cooling and crystallization mother liquor is treated by a solvent recovery tower, and the organic solvent is recovered at the top of the tower, and the tower kettle concentrated phase is deevaporated and crystallized to continue to recover benzanthrone, and the final concentrated mother liquor rich in impurities is discharged. The benzanthrone purification method disclosed in the present invention has the advantages of high product purity, high recovery rate, energy-saving and environmental protection in the process, and less by-product waste.

Description

Technical Field

[0001] The invention relates to the field of chemical separation and purification, and in particular to a method for purifying benzanthrone. Background Art

[0002] Benzanthrone is an important intermediate for the preparation of polycyclic vat dyes (Chen Rongqi, A Century-long History of the Development of Vat Dyes [J], Dyes and Coloring, Vol. 52, No. 5, October 2015), and is usually synthesized by the reaction of anthraquinone with glycerol, sulfuric acid and a reducing agent (usually iron). The reaction includes the reduction of anthraquinone to anthrone, which then undergoes a condensation reaction with acrolein formed by the dehydration of glycerol, and finally is oxidized with sulfuric acid to form benzanthrone. Benzanthrone can be used to produce vat brilliant green FFB, vat olive green B, vat gray M and vat black BBN. ​​In addition, it can also be used as a sensitizer in degradable thermoplastic plastic products.

[0003] The pure benzanthrone is a light yellow needle-shaped crystal, but due to its complex chemical structure and long synthesis process, the crude benzanthrone appears as a brown powder, and the purity is generally not high, between 60% and 90%. The purification method commonly used in industry is the high-temperature alkali boiling method (Su Hang, Purification of crude benzanthrone by high-temperature alkali boiling based on uniform design [J], Science and Technology Innovation and Application, Issue 22, 2014), which specifically involves boiling and washing the crude benzanthrone in ten to dozens of times the amount of alkali solution at 150-200°C under high pressure for a long time, then hot filtering, and then repeatedly washing the solid phase filter cake with a large amount of water to obtain the benzanthrone product. However, the high-temperature alkali boiling method has the following obvious disadvantages, such as low product purity, generally less than 93%, and it is difficult to remove metal ion impurities introduced by the catalyst, and a large amount of wastewater is generated that needs further treatment. In response to the defects of the high-temperature alkali boiling method, Chinese patent CN97107086.5 discloses a method for refining benzanthrone by sublimation. However, to achieve the sublimation conditions of benzanthrone, a higher temperature and extremely low pressure are required. The operating temperature is often higher than 200°C or even above 300°C, and the pressure is lower than several hundred Pascals, even within the range of tens of Pascals or several Pascals, almost close to a vacuum state. Therefore, the sublimation purification process has high requirements for equipment and energy consumption. At the same time, the sublimation process is slow, and can only be operated intermittently for loading and unloading. A production batch is often more than ten hours, and the production efficiency is low. In addition, since benzanthrone itself is flammable when exposed to open flames or high heat, its powder can form an explosive mixture with air, and benzanthrone dust is inevitably produced during solid phase unloading by sublimation. Therefore, there is a certain degree of danger in its purification process, and there have been explosion accidents in the actual operation of the factory. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention discloses a method for purifying benzanthrone, specifically, by using solvent recrystallization, utilizing the difference in solubility of organic solvents to benzanthrone and impurity components, and the difference in solubility with temperature to separate and purify the crude benzanthrone. According to the impurity content in the crude product and the requirements of the downstream application scenario for product purity, the crude benzanthrone can be selected for one or more recrystallization purification. Generally, the purity of the benzanthrone product can reach more than 99% after one recrystallization, and the purity of the benzanthrone can reach more than 99.5% after two or more recrystallization separation and purification.

[0005] In order to achieve the above purpose of benzanthrone purification, the present invention proposes the following technical solution:

[0006] A benzanthrone purification method, characterized in that: an organic solvent is added to a crude benzanthrone, the temperature is increased to dissolve it, solid-liquid separation is performed after the dissolution is complete, insoluble impurities are removed, the liquid phase enters a cooling crystallization section for cooling crystallization, and a solid benzanthrone product and a cooling crystallization mother liquor are obtained after solid-liquid separation of the low-temperature slurry.

[0007] Preferably, the benzanthrone product 1 is added to an organic solvent, the temperature is raised again to dissolve, solid-liquid separation is performed after complete dissolution, insoluble impurities are removed, the liquid phase enters the cooling crystallization section for cooling crystallization, and the low-temperature slurry is subjected to solid-liquid separation to obtain solid benzanthrone product 2 and cooling crystallization mother liquor 2.

[0008] Preferably, the cooling crystallization mother liquor 1 is subjected to solvent recovery treatment to separate and recover part of the organic solvent, and the recovered organic solvent is circulated for the temperature-raising dissolution of the crude benzanthrone or the benzanthrone product 1. As the solvent is recovered, a solid phase product is precipitated, and after solid-liquid separation, a solid benzanthrone product 3 and an effluent mother liquor are obtained, and the cooling crystallization mother liquor 2 is returned to the crude benzanthrone dissolution unit for the temperature-raising dissolution of the crude benzanthrone.

[0009] Preferably, detergent is added to wash the solid phase in the low-temperature slurry solid-liquid separation stage. The washing method can be elution or pulping. A detergent recovery unit is added accordingly. The recovered detergent is recycled for washing the solid phase in the low-temperature slurry solid-liquid separation stage, and the remaining mother liquor enters the solvent recovery unit for organic solvent recovery.

[0010] Preferably, when washing is performed by elution, the detergent is mixed into the corresponding cooling crystallization mother liquor. At this time, the detergent and the organic solvent are separated and recovered by distillation. Both the cooling crystallization mother liquor one and the cooling crystallization mother liquor two enter the distillation separation unit, and the recovered detergent and organic solvent are extracted at the corresponding position of the distillation separation unit according to the difference in boiling points of the detergent and the organic solvent.

[0011] Preferably, when washing is performed by pulping, the detergent will not be mixed into the cooling and crystallization mother liquor, but two independent washing liquids will be formed. The washing liquid 1 and the washing liquid 2 correspond to the washing units of the solid phase benzanthrone product 1 and the solid phase benzanthrone product 2, respectively. The washing liquid 1 and the washing liquid 2 both enter the detergent recovery unit, and the remaining mother liquor after the detergent is recovered and the cooling and crystallization mother liquor 1 both enter the solvent recovery unit, and the cooling and crystallization mother liquor 2 returns to the crude benzanthrone dissolution unit.

[0012] Preferably, the organic solvent is an organic solvent capable of dissolving benzanthrone, and the solubility of benzanthrone in the corresponding organic solvent has a positive correlation with temperature.

[0013] Preferably, the detergent is a solvent miscible with the organic solvent or is the same solvent as the organic solvent. When the detergent and the organic solvent are the same solvent, the detergent separation unit and the solvent recovery unit are combined into the same separation unit.

[0014] Preferably, the organic solvent is a mixture of one or more of hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, acids and anhydrides, esters, and amines.

[0015] Preferably, the detergent is a mixture of one or more organic solvents selected from water, hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, acids and anhydrides, esters, and amines.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention uses solvent recrystallization to purify benzanthrone, which has low operating temperature and normal pressure operation compared with the traditional method, low equipment requirements, low processing cost, safe and reliable process, and easy to achieve continuous production. At the same time, the product has high purity, no side reaction, and higher yield.

[0018] Since the organic solvents and detergents in the purification process can be recycled and reused, only a small amount of mother liquor is discharged with impurities. Compared with the traditional method, the process consumes less reagents and materials, has lower costs, less waste liquid discharge, and is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to facilitate understanding of the technical solution of the present invention, the accompanying drawings of the specification provide corresponding process flow diagrams according to different processing methods. The process flow diagram is only used to illustrate the direction of material flow and does not constitute a limitation on the specific operation method and processing equipment.

[0020] Figure 1 -Simplified process flow chart of benzanthrone recrystallization purification.

[0021] Figure 2-Simplified process flow chart of benzanthrone recrystallization purification and elution.

[0022] Figure 3 -Simplified process flow chart of benzanthrone recrystallization purification plus pulping and washing. DETAILED DESCRIPTION

[0023] In order to further explain the present invention, some specific implementation schemes of the present invention are given below in conjunction with the drawings of the specification. It should be pointed out that the following specific implementation schemes are only examples of the present invention under certain specific conditions and do not constitute limitations to the present invention.

[0024] Embodiment 1

[0025] 150 kg of crude benzanthrone with a content of about 70% produced by a factory was put into a 1.5m 3 In the crystallizer, add 1m 3 Aniline solvent is heated to 80°C using the waste heat of low-pressure steam from the factory, balanced for 1 hour, centrifuged, and insoluble residue is removed. The centrifuged mother liquor is sent to the cooling crystallizer. Under the appropriate stirring speed, the circulating water flux is controlled to slowly cool and crystallize the centrifuged mother liquor. The cooling end temperature is 30°C and the cooling time is 4 hours. Centrifuge again to obtain the solid phase benzanthrone product (product one). The cooling crystallization mother liquor (mother liquor one) goes to the solvent recovery section, and the aniline solvent is recovered by vacuum distillation for recycling. A small amount of remaining suspension is centrifuged to recover low-quality benzanthrone (product three) containing certain impurities, which is returned to the next processing cycle and mixed with the crude benzanthrone as the feed for the separation and purification section. The centrifuged mother liquor goes to the waste liquid storage tank for treatment.

[0026] After drying and weighing analysis, 81 kg of purified benzanthrone product (product 1) was obtained in a single cycle. After liquid chromatography analysis, the purity of the benzanthrone product was 99.23%. The single purification yield of benzanthrone was about 77%. The purity of the product can be further improved by secondary recrystallization. The recovery and treatment of low-quality benzanthrone (product 3) recovered in the solvent recovery section can further improve the overall yield of the separation and purification section.

[0027] Embodiment 2

[0028] 150 kg of the benzanthrone product obtained by intermittent production in the manner of Example 1 was put into a 1.5 m 3 In the crystallizer, add 1m 3Aniline solvent is heated to 80°C by using the waste heat of low-pressure steam in the factory, balanced for 1h, centrifuged, and insoluble residue is removed. The centrifuged mother liquor is sent to the cooling crystallizer. Under the appropriate stirring speed, the circulating water flux is controlled to slowly cool and crystallize the centrifuged mother liquor. The cooling end temperature is 10°C and the cooling time is 4h. Centrifuge again to obtain the solid phase benzanthrone product (product 2). During the centrifugation process, 10kg of ethanol is used to spray and wash the solid phase filter cake layer. Because it is a recrystallization process, the impurity content in the cooling crystallization mother liquor (mother liquor 2) is relatively low, and it contains a certain amount of benzanthrone. Therefore, the cooling crystallization (mother liquor 2) is sent to the intermediate storage tank, and the detergent ethanol is first recovered by vacuum distillation. The remaining aniline solution containing benzanthrone is used for the heating and dissolution process of crude benzanthrone in the next production cycle.

[0029] After drying and weighing analysis, 136 kg of purified benzanthrone product was obtained in a single cycle, and after liquid chromatography analysis, the purity of the benzanthrone product was 99.87%. The single purification yield of benzanthrone recrystallization was about 90.6%.

[0030] Embodiment 3

[0031] The above two embodiments are intermittent operations, and mainly examine the separation efficiency of the solvent crystallization separation and purification process, as well as the product purity that can be achieved by the primary crystallization and secondary recrystallization. However, since part of the benzanthrone is still dissolved in the remaining crystallization mother liquor, its single-pass yield is not high. In actual production, the solvent is recycled and the low-quality benzanthrone product three obtained after the solvent is removed is recovered and used to improve the comprehensive yield of the purification process.

[0032] According to the mass ratio of crude benzanthrone and aniline solvent of 1.5:10, add them to the constant temperature dissolution kettle at 90℃, stir and dissolve, control the dissolution time for 2h, centrifuge and remove insoluble filter residue. Centrifuge the mother liquor to the first cooling crystallizer. The cooling crystallization process is operated continuously, and a forced circulation crystallizer is used to control the temperature of the liquid in the crystallizer to be stable at 10℃. The high-temperature dissolved liquid is fed through the circulation pipeline, and the circulation volume is controlled to ensure that the mixed temperature rise at the feed is not higher than 2℃. Control the flow rate of inlet and outlet to ensure that the residence time in the cooling crystallizer is 4h. After solid-liquid separation, the solid phase benzanthrone product 1 and cooling crystallization mother liquor 1 are obtained. The solid phase benzanthrone product 1 is redissolved in a 90℃ constant temperature dissolution kettle to obtain a high-temperature benzanthrone solution. After filtering out a very small amount of insoluble impurities, the high-temperature dissolved liquid enters the second cooling crystallizer for recrystallization. The operating conditions of the second cooling crystallizer are the same as those of the first cooling crystallizer. After solid-liquid separation, the solid phase and cooling crystallization mother liquor 2 are obtained. The solid phase is slurried and washed with 1:1 ethanol, and then the benzanthrone product 2 and washing liquid are obtained after solid-liquid separation. The washing liquid is recycled by vacuum distillation to recover ethanol. The small amount of mother liquor remaining in the washing liquid recovery section and the cooling crystallization mother liquor one solvent recovery section are recycled by vacuum distillation to recover the aniline solvent (a small amount of detergent will be mixed, but it does not affect the overall purification effect of the process), and are recycled for the high-temperature dissolution process of the crude benzanthrone. The remaining slurry is separated by solid and liquid to obtain benzanthrone product 3 and a small amount of mother liquor. Benzanthrone product 3 is returned to the crude benzanthrone dissolution section for cyclic treatment, and a small amount of mother liquor is discharged with impurities. The cooling crystallization mother liquor two is returned to the crude benzanthrone dissolution section after heating. Since a small amount of organic solvent and detergent will be discharged with impurities, the purification process needs to add fresh detergent and organic solvent in the product washing section and the benzanthrone product one re-dissolution section according to actual needs.

[0033] The above process was run continuously, and after the cumulative production of 5 tons of benzanthrone, the raw material consumption was counted and the product yield was calculated, and the product purity was monitored. After analysis, the purity of the product of the solvent crystallization separation and purification process was stable between 99.83-99.92%, and the comprehensive yield reached 98.3%.

[0034] In addition, based on the results of the small-scale experiment, the applicant unit conducted a continuous scale-up production investigation on the separation and purification effects of other feasible organic solvents and detergents. The relevant results are listed in Table-1.

[0035] Table-1

[0036] Solvents Detergent Product purity% Comprehensive yield% aniline Ethanol 99.92 98.3 o-Dichlorobenzene Methanol 99.68 97.6 Xylene Ethanol 99.83 96.8 Ethanol Ethanol 99.79 97.2 Ethyl acetate water 99.86 96.6

[0037] It should be pointed out that the above examples only verify the purification effects of some feasible organic solvents and detergents. There are many types of industrial solvents, and it is impossible to enumerate all feasible types of solvents. In theory, any solvent that meets the functional limitations of organic solvents and detergents in the content of the present invention can achieve the purpose of the present invention and achieve the effect of purifying benzanthrone. Any person skilled in the art, inspired by the present invention, investigates the specific solvent types not mentioned in the present invention, and the benzanthrone purification scheme formed according to the separation and purification process disclosed in the present invention is within the scope of protection of the present invention.

Claims

1. A method for purifying benzanthrone, characterized in that: The organic solvent is added to the crude benzanthrone, the temperature is increased to dissolve, and solid-liquid separation is performed after the dissolution is complete to remove insoluble impurities, and the liquid phase enters the cooling crystallization section for cooling crystallization, and solid-liquid separation is performed at low temperature to obtain solid benzanthrone product 1 and cooling crystallization mother liquor 1, and the benzanthrone product 1 is added to the organic solvent, the temperature is increased again to dissolve, and solid-liquid separation is performed after the dissolution is complete to remove insoluble impurities, and the liquid phase enters the cooling crystallization section for cooling crystallization, and solid benzanthrone product 2 and cooling crystallization mother liquor 2 are obtained after solid-liquid separation of the low temperature slurry, and the cooling crystallization mother liquor 1 is subjected to solvent recovery treatment, and separation and recovery are performed. Part of the organic solvent is recycled for the temperature-raising dissolution of the crude benzanthrone or the benzanthrone product 1. As the solvent is recovered, a solid phase product is precipitated. After solid-liquid separation, a solid benzanthrone product 3 and an external mother liquor are obtained. The mother liquor 2 is cooled and crystallized and returned to the crude benzanthrone dissolution unit for the temperature-raising dissolution of the crude benzanthrone. The organic solvent is a mixture of one or more of aniline, o-dichlorobenzene, xylene, ethanol, and ethyl acetate as a solvent. The organic solvent is an organic solvent that can dissolve benzanthrone, and the solubility of benzanthrone in the corresponding organic solvent is positively correlated with the temperature.

2. A method for purifying benzanthrone according to claim 1, characterized in that: In the low-temperature slurry solid-liquid separation stage, detergent is added to wash the solid phase. The washing method can be elution or pulping. A detergent recovery unit is added accordingly. The recovered detergent is recycled for washing the solid phase in the low-temperature slurry solid-liquid separation stage, and the remaining mother liquor enters the solvent recovery unit for organic solvent recovery.

3. A method for purifying benzanthrone according to claim 2, characterized in that: When washing is performed by elution, the detergent is mixed into the corresponding cooling crystallization mother liquor. At this time, the detergent and the organic solvent are separated and recovered by distillation. Both the cooling crystallization mother liquor 1 and the cooling crystallization mother liquor 2 enter the distillation separation unit. The recovered detergent and organic solvent are taken out at the corresponding position of the distillation separation unit according to the difference in boiling points between the detergent and the organic solvent.

4. A method for purifying benzanthrone according to claim 2, characterized in that: When washing is performed in a pulping manner, the detergent will not be mixed into the cooling crystallization mother liquor, but two independent washing liquids will be formed. The washing liquid 1 and the washing liquid 2 correspond to the washing units of the solid phase benzanthrone product 1 and the solid phase benzanthrone product 2 respectively. The washing liquid 1 and the washing liquid 2 both enter the detergent recovery unit, and the remaining mother liquor after the detergent is recovered and the cooling crystallization mother liquor 1 both enter the solvent recovery unit, and the cooling crystallization mother liquor 2 returns to the crude benzanthrone dissolution unit.

5. A method for purifying benzanthrone according to claim 4, characterized in that: The detergent is a solvent that is miscible with the organic solvent or is the same solvent as the organic solvent. When the detergent and the organic solvent are the same solvent, the detergent separation unit and the solvent recovery unit are combined into the same separation unit.

6. A method for purifying benzanthrone according to claim 5, characterized in that: The detergent is a mixture of one or more organic solvents selected from water, hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, acids and anhydrides, esters, and amines.

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