Industrial preparation method of 4-bromophthalic anhydride

Abstract

The invention discloses an industrial preparation method of 4-bromophthalic anhydride, which comprises the following steps: adding phthalic anhydride, sodium hydroxide and a phase transfer catalyst into water, dropwise adding bromine to carry out bromination reaction, cooling, adding a saturated sodium sulfite aqueous solution, precipitating a solid, centrifuging, and collecting the solid to prepare an intermediate crude product as shown in a formula II; adding water into the intermediate crude product as shown in the formula II, and carrying out acidification reaction by using concentrated hydrochloric acid to prepare 4-bromophthalic acid as shown in a formula III; the preparation method comprises the following steps: adding 4-bromophthalic acid as shown in a formula III into an organic solvent, dropwise adding a dehydrating agent, heating to reflux, and carrying out a dehydration reaction to prepare 4-bromophthalic anhydride as shown in a formula IV; the post-treatment reduces the solvent extraction step and the solvent dosage, the final purification process does not need rectification, the crystallization method is simple, the requirement on equipment is low, less three wastes are generated, the energy consumption is low, and the method is very suitable for industrial production. # imgabs0 #

Description

Technical Field

[0001] The invention relates to a method for preparing 4-bromophthalic anhydride, and in particular to a practical and effective industrial preparation method for 4-bromophthalic anhydride. Background Art

[0002] 4-Bromophthalic anhydride is a very important chemical intermediate, widely used in dyes, medicines, polymer industrial production, etc. The synthesis of 4-bromophthalic anhydride reported so far is mostly at the laboratory test level, while industrial preparation requires process flow and operation methods to meet the needs of continuous production, simplify operations, and improve production efficiency. There are significant differences between industrial preparation and ordinary laboratory tests in terms of raw material selection, equipment materials, process flow, and post-processing steps, which need to be improved.

[0003] For example, industrial production will produce waste gas, waste water and waste residue, so it is necessary to consider the treatment of the three wastes, whether it is necessary to increase the treatment and recycling steps, to minimize the amount of solvents in the process, or to change the steps. Each step should consider whether the existing industrial equipment can be implemented, the energy cost consumed, etc. The post-processing steps should be simplified as much as possible to reduce costs while ensuring the product yield and purity.

[0004] Chinese patent CN107082769 reports a three-stage programmed temperature bromination and final product distillation method. This method has very high requirements for equipment, and it is difficult to distill a product with a melting point of 130 degrees. In addition, this patent uses a large amount of solvent extraction after acidification, and the solvent is evaporated after extraction to obtain the product. The amount of solvent used is too large, the cost is high, and it pollutes the environment, which is not suitable for industrial production.

[0005] CN105399712A discloses a method for preparing 4-bromophthalic anhydride, wherein sodium hydroxide is dissolved in water, phthalic anhydride is added, a phase transfer catalyst is stirred evenly, a three-stage program temperature control is adopted and reacted by adding reactants three times, 20% fuming sulfuric acid is added for acidification, sodium bisulfite aqueous solution is added after cooling to remove excess bromine, an organic solvent is added for extraction, the organic solvent is removed by distillation, and then the temperature is raised to obtain a crude 4-bromophthalic anhydride product, and the product is rectified and dehydrated under vacuum conditions, and the fractions are collected to obtain a finished 4-bromophthalic anhydride product. The same problem of this patent is that an organic solvent extraction is required, which consumes solvents. In addition, rectification and dehydration under vacuum conditions are required at the end, and the equipment cost of rectification is high, the difficulty is large, and it is difficult to industrialize.

[0006] In view of the shortcomings of the existing technology, it is of practical significance to develop a method for preparing 4-bromophthalic anhydride suitable for industrialization. Summary of the invention

[0007] The purpose of the present invention is to provide an industrial preparation method of 4-bromophthalic anhydride, which has high reaction yield, simple post-processing steps, less solvent consumption and low production cost.

[0008] The technical solution adopted by the present invention is:

[0009] An industrial preparation method of 4-bromophthalic anhydride, the method comprising the following steps:

[0010] (1) Phthalic anhydride, sodium hydroxide and a phase transfer catalyst are added to water, stirred evenly, heated to 50-80° C., bromine is added dropwise to carry out bromination reaction, and after cooling, a saturated aqueous sodium sulfite solution is added to precipitate a solid, centrifuged, and the solid is collected to obtain a crude intermediate of formula II;

[0011] (2) adding water to the crude intermediate of formula II, heating to 40-50°C, adding concentrated hydrochloric acid for acidification reaction, cooling to 0-5°C to precipitate solid, collecting the solid by centrifugation, washing with water, collecting the solid by centrifugation, and drying to obtain 4-bromophthalic acid of formula III;

[0012] (3) 4-bromophthalic acid represented by formula III is added to an organic solvent, a dehydrating agent is added dropwise, and the mixture is heated to reflux for dehydration reaction, then cooled to room temperature, filtered, and the filtrate is evaporated to remove the solvent, and petroleum ether is added, heated at 40-45° C., and then cooled to 0-10° C. to precipitate a solid, which is collected by centrifugation to obtain 4-bromophthalic anhydride represented by formula IV.

[0013] The reaction formula of the method is shown below:

[0014]

[0015] In the step (1), the mass ratio of phthalic anhydride to sodium hydroxide is 1:0.5-0.6.

[0016] The mass ratio of phthalic anhydride to phase transfer catalyst is 1:0.01-0.02.

[0017] The phase transfer catalyst is at least one of tetrabutylammonium bromide, tetraethylammonium bromide, benzyltriethylammonium chloride and benzyltrimethylammonium chloride, preferably tetrabutylammonium bromide.

[0018] In the step (1), the mass ratio of phthalic anhydride to bromine is 1:1.2-1.5.

[0019] The mass ratio of sodium hydroxide to water is 1:5-6.

[0020] The bromination reaction time is 15 to 25 hours.

[0021] The mass dosage of the saturated sodium sulfite aqueous solution is 40-45% of the mass of phthalic anhydride.

[0022] Bromine can be added dropwise all at once or in two steps.

[0023] The specific reaction steps of adding bromine dropwise in two steps are:

[0024] (1-a) Phthalic anhydride, sodium hydroxide and a phase transfer catalyst are added to water, stirred evenly, heated to 50-60°C, the first part of bromine is added dropwise to carry out bromination reaction, the reaction is carried out for 6-8 hours, and then a saturated aqueous solution of sodium hydroxide is added, stirred evenly, and the remaining bromine is added dropwise to carry out bromination reaction, the temperature is raised to 75-80°C and the reaction is carried out for 10-15 hours; after the reaction is completed, the reaction is cooled to 45-55°C, a saturated aqueous solution of sodium sulfite is added dropwise, and the reaction is cooled to 5-10°C to precipitate a solid, centrifuged, and the solid is collected to obtain a crude intermediate of formula II;

[0025] The mass dosage of the first part of bromine is 60-70% of the mass of the total bromine.

[0026] The mass dosage of the saturated sodium hydroxide solution is 25-30% of the mass of phthalic anhydride.

[0027] The reaction steps of adding bromine dropwise at one time are:

[0028] (1-b) Phthalic anhydride, sodium hydroxide and a phase transfer catalyst are added to water, stirred evenly, heated to 50-60°C, bromine is added dropwise to carry out bromination reaction, and the reaction is carried out for 16-23 hours. After the reaction is completed, the water is cooled and then a saturated aqueous sodium sulfite solution is added. The solid is precipitated by cooling, centrifuged, and the solid is collected. The solid is then washed with water and centrifuged to collect the solid to obtain a crude intermediate of formula II.

[0029] In the step (2), the mass ratio of the crude intermediate represented by formula II to water is 1:2 to 3, preferably 1:2.

[0030] In the step (2), the ratio of the molar number of HCl in the concentrated hydrochloric acid to the molar number of the intermediate represented by formula II is 1:1. The mass fraction of the concentrated hydrochloric acid is 30%.

[0031] Specifically, the mass of concentrated hydrochloric acid is 0.4 to 0.5 times the mass of the crude intermediate represented by formula II.

[0032] In the step (2), the acidification reaction time is generally 20 to 40 minutes.

[0033] In the step (2), the mass of the water used for washing is 80% to 90% of the mass of the crude intermediate represented by formula II.

[0034] In the step (3), the organic solvent is ethyl acetate or toluene.

[0035] The dehydration reaction is carried out by heating to reflux, generally heating to the boiling point of the organic solvent and reflux to carry out the reaction.

[0036] The volume dosage of the organic solvent is generally 3 to 4 L / Kg based on the mass of 4-bromophthalic acid.

[0037] The dehydrating agent is thionyl chloride.

[0038] The mass ratio of the 4-bromophthalic acid to the dehydrating agent is 1:1.

[0039] The dehydration reaction time is 3 to 4 hours.

[0040] In the step (3), the evaporated solvent can be recovered and reused.

[0041] In the step (3), the volume amount of petroleum ether is generally 3 to 4 L / Kg based on the mass of 4-bromophthalic acid.

[0042] After adding petroleum ether, heat at 40-45°C for 5-6 hours.

[0043] The beneficial effects of the present invention are:

[0044] 4-bromophthalic anhydride is obtained by bromination, acidification, dehydration, and crystallization of conventional and readily available phthalic anhydride as raw material. In the bromination reaction, a phase transfer catalyst such as tetrabutylammonium bromide is added to increase the solubility of bromine, reduce the escape of bromine during the dropwise addition, and greatly shorten the reaction time. Sodium sulfite is added in the post-treatment to obtain the sodium salt, which can be directly centrifuged to obtain the product without the need for organic solvent extraction, thereby reducing the amount of solvent used.

[0045] The post-treatment of the acidification reaction is to cool to 0 degrees to precipitate solids, and collect the solids by centrifugation. The obtained solids are then slurried with water and dried to obtain 4-bromophthalic acid of qualified purity. The post-treatment of the acidification reaction also does not require solvent extraction, the washing steps are simple, and the obtained product has high purity.

[0046] In the dehydration cyclization reaction, dehydration is performed by a dehydrating agent, and salt and mechanical impurities are removed by filtering in the post-treatment. After the solvent is removed, petroleum ether is used for crystallization, and 4-bromophthalic anhydride is obtained by filtering. The final purification process of the present invention does not require rectification, the crystallization method is simple, the equipment requirements are low, and the amount of solvent used is greatly reduced compared with the prior art.

[0047] The reaction process of the present invention is obtained through a large number of experiments. It uses economical and readily available raw materials, has a simple process, generates less three wastes, consumes low energy, has low requirements on equipment, can be mass-produced, and is very suitable for industrial production. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0049] Example 1

[0050] Add 165kg sodium hydroxide, 900L water, 300kg phthalic anhydride, 3kg tetrabutylammonium bromide to a 3000L reactor and stir evenly. Control the temperature at 60°C, slowly add 300kg bromine to the reactor and react for 6 hours. Control the temperature at 60°C, add 75kg saturated sodium hydroxide solution to the reactor head tank, stir for half an hour, drop 150kg bromine, heat to 75°C and react for 12 hours. Cool to about 50°C, drop 125kg saturated aqueous solution of sodium sulfite, cool to 10°C, centrifuge to collect solids, add 500kg water to wash, centrifuge, collect solids, and obtain about 600kg crude intermediate of formula II.

[0051] Add 1200kg of water to a 3000L reactor, put 600kg of the crude intermediate back into the reactor, heat to 50°C, drop 246kg of concentrated hydrochloric acid (30%), stir for 30min after the addition, cool to 0-5°C to precipitate the diacid product, and collect the solid by centrifugation. Put it back into the kettle, beat with 500kg of water, collect the solid by centrifugation, and dry to obtain 4-bromophthalic acid.

[0052] Add 200 kg of the intermediate 4-bromophthalic acid and 600 L of ethyl acetate into a 3000 L reactor, slowly add 200 kg of thionyl chloride, heat to 80° C., reflux and stir to react for 3 hours.

[0053] After checking that the reaction is complete, cool to 25°C, filter and transfer to a kettle to remove mechanical impurities, and evaporate ethyl acetate for recovery and reuse.

[0054] The mixture was cooled to about 40°C, 600 L of petroleum ether was added, and heating was continued for 5 hours. The mixture was cooled to 10°C, centrifuged, and dried to collect 452 kg of product with a purity of 98% and a yield of 98.3%.

[0055] Embodiment 2:

[0056] 300 kg of phthalic anhydride was dissolved in 1065 kg of sodium hydroxide aqueous solution (165 kg of sodium hydroxide was dissolved in 900 kg of water) for saponification, and then heated to 50°C, 3 kg of tetrabutylammonium bromide was added, and then 450 kg of bromine was added dropwise for bromination. The reaction was carried out for 18 hours. After the reaction was completed, the temperature was lowered to room temperature, 125 kg of saturated sodium sulfite aqueous solution was added, and the solid was collected by centrifugation. The wet product was then added with 500 kg of water, stirred and washed, and then centrifuged to collect the solid, and about 600 kg of crude intermediate was obtained.

[0057] The product of the previous step was dissolved and dispersed in 1200 kg of water, and the temperature was controlled below 50°C, and 246 kg of concentrated hydrochloric acid (30%) was added for acidification to obtain a 4-bromophthalic acid aqueous solution, and then the temperature was lowered to 0°C to precipitate a solid, which was collected by centrifugation. The obtained solid was then slurried with 500 kg of water and dried to obtain 4-bromophthalic acid with a purity of 99%.

[0058] Disperse 200 kg of 4-bromophthalic acid in 600 L of toluene, add 200 kg of dehydrating agent thionyl chloride dropwise, heat to 110 ° C and reflux for 3 hours, cool and turn the kettle to remove salt and mechanical impurities, evaporate toluene, add 600 L of petroleum ether to precipitate 450 kg of product with a purity of 98.5% and a yield of 97.8%.

[0059] Example 3

[0060] Add 165kg sodium hydroxide, 900L water, 300kg phthalic anhydride, 5kg tetrabutylammonium bromide to a 3000L reactor and stir evenly. Control the temperature at 60℃, slowly add 300kg bromine to the reactor and react for 6 hours. Control the temperature at 60℃, add 75kg saturated sodium hydroxide solution to the reactor head tank, stir for half an hour, drop 100kg bromine, heat to 75℃ and react for 10 hours. Cool to about 50℃, drop 125kg saturated aqueous solution of sodium sulfite, cool to 10℃, centrifuge to collect solids, add 500kg water to wash, centrifuge, collect solids, and obtain about 600kg crude intermediate.

[0061] Add 1200kg of water to a 3000L reactor, put 600kg of crude product back into the reactor, raise the temperature to 50°C, drop 246kg of concentrated hydrochloric acid (30%), cool to precipitate the diacid product, collect the solid by centrifugation, put it back into the reactor, beat with 500kg of water, collect the solid by centrifugation, and dry to obtain 4-bromophthalic acid.

[0062] 200 kg of the intermediate 4-bromophthalic acid and 600 L of ethyl acetate were added to a 3000 L reactor, and 200 kg of thionyl chloride was slowly added, and the mixture was heated to 80° C. and stirred for 3 hours.

[0063] After the reaction is complete, cool to 25°C, filter and transfer to a kettle to remove mechanical impurities, and evaporate ethyl acetate for recovery and reuse.

[0064] The mixture was cooled to about 40°C, 600 L of petroleum ether was added, and heating was continued for 5 hours. The mixture was cooled to 10°C, centrifuged, and dried. 449 kg of solid product was collected with a purity of 99% and a yield of 97.6%.

Claims

1. An industrial preparation method of 4-bromophthalic anhydride, characterized in that The method comprises the following steps: (1) Phthalic anhydride, sodium hydroxide and a phase transfer catalyst are added to water, stirred evenly, heated to 50-80° C., bromine is added dropwise to carry out bromination reaction, and after cooling, a saturated aqueous sodium sulfite solution is added to precipitate a solid, centrifuged, and the solid is collected to obtain a crude intermediate of formula II; (2) adding water to the crude intermediate of formula II, heating to 40-50°C, adding concentrated hydrochloric acid for acidification reaction, cooling to 0-5°C to precipitate solid, collecting the solid by centrifugation, washing with water, collecting the solid by centrifugation, and drying to obtain 4-bromophthalic acid of formula III; (3) 4-bromophthalic acid represented by formula III is added to an organic solvent, a dehydrating agent is added dropwise, and the mixture is heated to reflux for dehydration reaction, then cooled to room temperature, filtered, and the filtrate is evaporated to remove the solvent, and petroleum ether is added, heated at 40 to 45° C., and then cooled to 0 to 10° C. to precipitate a solid, and the solid is collected by centrifugation to obtain 4-bromophthalic anhydride represented by formula IV; The reaction formula of the method is shown below:

2. The method according to claim 1, characterized in that In the step (1), the mass ratio of phthalic anhydride to sodium hydroxide is 1:0.5-0.6; The mass ratio of phthalic anhydride to phase transfer catalyst is 1:0.01-0.02; The mass ratio of phthalic anhydride to bromine is 1:1.2-1.

5.

3. The method according to claim 1, characterized in that In the step (1), the phase transfer catalyst is at least one of tetrabutylammonium bromide, tetraethylammonium bromide, benzyltriethylammonium chloride, and benzyltrimethylammonium chloride.

4. The method according to claim 1, characterized in that In the step (1), the bromination reaction time is 15 to 25 hours.

5. The method according to claim 1, characterized in that The step (1) can be performed in one of the following two ways: (1-a) adding bromine dropwise in two steps: adding phthalic anhydride, sodium hydroxide and a phase transfer catalyst into water, stirring evenly, heating to 50-60° C., adding the first part of bromine dropwise for bromination reaction, reacting for 6-8 hours, then adding a saturated aqueous solution of sodium hydroxide, stirring evenly, and then adding the remaining bromine dropwise for bromination reaction, heating to 75-80° C. for 10-15 hours; after the reaction is completed, cooling to 45-55° C., adding a saturated aqueous solution of sodium sulfite dropwise, and then cooling to 5-10° C. to precipitate a solid, centrifuging, collecting the solid, and obtaining a crude intermediate of formula II; the mass amount of the first part of bromine is 60-70% of the mass of the total bromine; (1-b) Add bromine dropwise at one time: add phthalic anhydride, sodium hydroxide and phase transfer catalyst into water, stir evenly, heat to 50-60°C, add bromine dropwise for bromination reaction, react for 16-23 hours, cool after the reaction, add saturated sodium sulfite aqueous solution, cool to precipitate solid, centrifuge, collect solid, wash with water and centrifuge, collect solid to obtain a crude intermediate of formula II.

6. The method according to claim 1, characterized in that In the step (2), the ratio of the molar number of HCl in the concentrated hydrochloric acid to the molar number of the intermediate represented by formula II is 1:

1.

7. The method according to claim 1, characterized in that In the step (3), the organic solvent is ethyl acetate or toluene.

8. The method according to claim 1, characterized in that In the step (3), the dehydrating agent is thionyl chloride.

9. The method according to claim 1, characterized in that In the step (3), the mass ratio of the 4-bromophthalic acid to the dehydrating agent is 1:

1.

10. The method according to claim 1, characterized in that In the step (3), the dehydration reaction time is 3 to 4 hours.

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