A method for producing N-(2-hydroxyethyl)-phthalimide by ammoniolysis of phthalic anhydride residues by ethanolamine

Abstract

The invention discloses a method for producing N-(2-hydroxyethyl)-phthalimide by the aminolysis of phthalic anhydride slag by ethanolamine, and belongs to the technical field of phthalic anhydride slag recycling. The method can convert phthalic anhydride and other components in phthalic anhydride slag into organic chemical and pharmaceutical intermediate N-(2-hydroxyethyl)-phthalimide. The present invention utilizes the aminolysis reaction of ethanolamine and phthalic anhydride, and the phthalic anhydride waste residue aminolysis product can be separated and purified by recrystallization through water while hot, and the product N-(2-hydroxyethyl)-phthalimide purity can reach more than 95%, and the conversion rate of phthalic anhydride in phthalic anhydride slag can reach more than 95%. The process conditions of the present invention are mild, the separation is simple, the product added value is high, the large-scale resource recycling of industrial phthalic anhydride slag can be realized, and a new synthetic route is opened up for the production of N-(2-hydroxyethyl)-phthalimide.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling phthalic anhydride residues, and particularly relates to a method for producing N-(2-hydroxyethyl)-phthalimide by ammoniolysis of phthalic anhydride residues by ethanolamine. Background Art

[0002] Phthalic anhydride residue, also known as phthalic anhydride residue, is a high-boiling point waste residue produced as a byproduct of the preparation of phthalic anhydride by the naphthalene oxide method or the o-xylene oxidation method. The domestic output is as high as about 5,000 tons. The chemical composition of phthalic anhydride residue is relatively complex, consisting of 75-95% phthalic anhydride, acidic oxides, salts, quinones, ash, water, etc. At present, most phthalic anhydride production enterprises at home and abroad use incineration or landfill to treat phthalic anhydride production waste residue. However, landfill and incineration will not only bring a series of environmental problems such as soil poisoning and air pollution, but also the organic resources in phthalic anhydride residue are not fully utilized. Therefore, researchers have developed a series of resource utilization processes for the treatment and recovery of phthalic anhydride residue. In China, sublimation or recrystallization is generally used to recover phthalic anhydride, the main component of phthalic anhydride residue. However, the sublimation method has problems such as unsafe recovery and low product purity; the recrystallization method can obtain phthalic acid, but there are also difficulties such as low phthalic anhydride recovery rate and large sewage discharge. The method of directly recovering phthalic anhydride from phthalic anhydride residue is difficult to be further applied; however, converting phthalic anhydride in phthalic anhydride residue into high-value target organic compounds and then separating them has become a new research direction in this field.

[0003] Patent CN103910635A prepares crude di-n-butyl phthalate by esterification reaction of phthalic anhydride residue waste and n-butanol, and then completes the purification of crude product by washing, neutralization and distillation, and can achieve di-n-butyl phthalate content of more than 99%, and phthalic anhydride utilization rate of more than 90%. The product di-n-butyl phthalate of this method can be used as a plasticizer, and efficient recycling of phthalic anhydride waste residue is achieved. However, sulfuric acid catalysis is required in this method, and it is inevitable to corrode equipment, produce acidic wastewater, increase the difficulty of subsequent product separation, and pollute the environment during production.

[0004] Patent CN1318383C uses crude phthalic anhydride and fusel oil to prepare C4-C5 mixed esters, which can be used as plasticizers. This method uses sodium bisulfate as a catalyst, recovers excess alcohol by distillation, and recovers the catalyst by centrifugation. The recovery rate of phthalic anhydride in this method can reach more than 90%. Since the reaction products all need to be separated by distillation, there are disadvantages such as high heat load and complicated separation process.

[0005] Patent CN101298506 mentions a method of preparing PVC plasticizer from a phthalic anhydride byproduct and corn alcohol mixture. The method uses an organic tin catalyst to catalyze the reaction, and the product is purified by vacuum distillation, which improves the degree to which the plasticizer is affected by crude oil prices. However, the recovery rate of phthalic anhydride is unclear and there is a lack of specific products.

[0006] In summary, the existing phthalic anhydride slag organic resource recycling and reuse technologies all use the esterification reaction of alcohol and phthalic anhydride to prepare plasticizers, which has low product added value and unsatisfactory economic efficiency. The esterification reaction inevitably requires the use of a catalyst, which not only has the difficulty of separating acidic homogeneous catalysts such as sulfuric acid, but also the esterification reaction products are separated by distillation, which greatly increases the separation energy consumption. Therefore, it is urgent to develop an economic technology for the recycling and reuse of phthalic anhydride slag organic resources with low separation difficulty and high phthalic anhydride conversion rate.

[0007] The process for producing organic chemical and pharmaceutical intermediate N-(2-hydroxyethyl)-phthalimide by ammoniolysis of phthalic anhydride residue by ethanolamine proposed by the invention can realize the conversion of phthalic anhydride residue into N-(2-hydroxyethyl)-phthalimide through amination reaction of ethanolamine and phthalic anhydride without adding additional catalyst, and the subsequent product can be separated and purified by mixing with water, and the separation process is simple, the energy consumption is low, and the product purity is high. The method is of great significance to the sustainable development, pollutant control and improvement of economic benefits of phthalic anhydride production enterprises. Summary of the invention

[0008] In order to overcome the shortcomings and deficiencies of the existing phthalic anhydride slag resource utilization process, the object of the present invention is to provide a method for producing N-(2-hydroxyethyl)-phthalimide by hydrolyzing phthalic anhydride slag with ethanolamine and separating the same, wherein the residual phthalic anhydride and residual acid in the phthalic anhydride waste slag are hydrolyzed with ethanolamine, and the hydrolyzed solution after the hydrolysis is directly mixed with water to dissolve impurities so that the target product N-(2-hydroxyethyl)-phthalimide is crystallized and purified.

[0009] In order to achieve the above-mentioned invention object, the present invention specifically adopts the following technical solutions:

[0010] A method for producing N-(2-hydroxyethyl)-phthalimide by ammoniolysis of phthalic anhydride residue with ethanolamine and separation thereof: using ethanolamine as a reactant to ammoniolyze waste residues produced in the production process of phthalic anhydride to prepare and recover N-(2-hydroxyethyl)-phthalimide, and the reaction formula is:

[0011] .

[0012] The specific steps include:

[0013] (1) After the phthalic anhydride waste residue is crushed, it is added into a reactor with a certain proportion of ethanolamine, heated to a specified temperature under normal pressure, and reacted for 3 hours under mechanical stirring to obtain phthalic anhydride residue aminolysis solution;

[0014] (2) Add a certain amount of water to the hot ammine solution of phthalic anhydride residue obtained in step (1) to crystallize the product, and filter to obtain white crystals, namely, the product N-(2-hydroxyethyl)-phthalimide.

[0015] Furthermore, the mass ratio of the phthalic anhydride waste residue powder to the ethanolamine in step (1) is 3:5-2:5.

[0016] Furthermore, the ethanolamine is monoethanolamine.

[0017] Furthermore, the reaction temperature in step (1) is 120-130°C.

[0018] Furthermore, the water added in step (2) includes ice water or saturated salt water.

[0019] Furthermore, in step (2), the volume ratio of water to phthalic anhydride residue aminolysis solution is 2:1-5:1.

[0020] The beneficial effects of the present invention are:

[0021] The process for producing organic chemical and pharmaceutical intermediate N-(2-hydroxyethyl)-phthalimide by aminolysis of phthalic anhydride residue by ethanolamine proposed by the present invention can realize the conversion of phthalic anhydride residue into N-(2-hydroxyethyl)-phthalimide through aminolysis reaction of ethanolamine and phthalic anhydride without adding additional catalyst, and the subsequent product can be crystallized by simply mixing with water, and has the characteristics of high utilization rate of phthalic anhydride residue, high conversion rate, high product added value, simple product separation process, low energy consumption, etc. The method is of great significance to the sustainable development, pollutant control and economic benefit improvement of phthalic anhydride production enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a gas chromatography-mass spectrometry analysis spectrum of the amination products of phthalic anhydride residue by ethanolamine, 1 is ethanolamine, 2 is benzoic acid, 3 is phthalic anhydride, and 4 is N-(2-hydroxyethyl)-phthalimide. Specific implementation methods

[0023] The present invention is further described by the following specific examples, but the protection scope of the present invention is not limited to the following examples.

[0024] Example 1

[0025] (1) The phthalic anhydride residue was crushed into powder, 60.00 g of the phthalic anhydride residue was weighed and added into a reactor, followed by 100.00 g of ethanolamine. The mixture was heated under reflux at 130 °C for 3 h under mechanical stirring to obtain a phthalic anhydride residue ammonium hydrolysis solution. The composition of the ammonium hydrolysis solution was determined by gas chromatography-mass spectrometry to be a mixture of N-(2-hydroxyethyl)-phthalimide, ethanolamine, phthalic anhydride and benzoic acid. The conversion rate of phthalic anhydride in the phthalic anhydride residue was 95.33%.

[0026] (2) Salting out and filtration of phthalic anhydride ammonium hydrolysis solution: The phthalic anhydride residue ammonium hydrolysis solution obtained in (1) was added with saturated saline solution while hot for salting out. The volume ratio of saturated saline solution to ammonium hydrolysis solution was 2:1. After filtration, N-(2-hydroxyethyl)-phthalimide white powder was obtained with a purity of 96.62%. In this separation method, the recovery rate of N-(2-hydroxyethyl)-phthalimide can reach 96.73%.

[0027] Example 2

[0028] (1) The phthalic anhydride residue was crushed into powder, 60.00 g of the phthalic anhydride residue was weighed and added into a reactor, followed by the addition of 150.00 g of ethanolamine. The mixture was heated under reflux at 120 °C for 3 h under mechanical stirring to obtain the phthalic anhydride residue aminolysis solution. The conversion rate of phthalic anhydride in the phthalic anhydride residue was 91.90% by gas chromatography-mass spectrometry analysis.

[0029] (2) Salting out and filtration of phthalic anhydride ammonium hydrolysis solution: The phthalic anhydride residue ammonium hydrolysis solution obtained in (1) is added with saturated saline solution while hot for salting out. The volume ratio of saturated saline solution to ammonium hydrolysis solution is 2:1. After filtration, N-(2-hydroxyethyl)-phthalimide white powder can be obtained with a purity of up to 96.61%. In this separation method, the recovery rate of N-(2-hydroxyethyl)-phthalimide can reach 94.62%.

[0030] Example 3

[0031] (1) The phthalic anhydride residue was crushed into powder, 60.00 g of the phthalic anhydride residue was weighed and added into a reactor, followed by the addition of 110.00 g of ethanolamine. The mixture was heated under reflux at 130 °C for 3 h under mechanical stirring to obtain phthalic anhydride residue aminolysis solution. The conversion rate of phthalic anhydride in the phthalic anhydride residue was 95.50% by gas chromatography-mass spectrometry analysis.

[0032] (2) Crystallization and filtration of phthalic anhydride ammonium hydrolysis solution: The phthalic anhydride residue ammonium hydrolysis solution obtained in (1) is mixed with ice water while hot, with the volume ratio of ice water to ammonium hydrolysis solution being 5:1. After filtration, N-(2-hydroxyethyl)-phthalimide white powder can be obtained with a purity of up to 96.55%. In this separation method, the recovery rate of N-(2-hydroxyethyl)-phthalimide can reach 94.57%.

[0033] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for producing N-(2-hydroxyethyl)-phthalimide by ammoniolysis of phthalic anhydride residues by ethanolamine, characterized in that: The specific steps include: (1) After the phthalic anhydride waste residue is crushed, it is added into a reactor with a certain proportion of ethanolamine, heated to a specified temperature under normal pressure, and reacted for 3 hours under mechanical stirring to obtain phthalic anhydride residue aminolysis solution; (2) adding a certain amount of ice water or saturated brine to the phthalic anhydride residue aminolysis solution obtained in step (1) while it is still hot to crystallize the product, and filtering to obtain white crystals, namely, the product N-(2-hydroxyethyl)-phthalimide; The mass ratio of the phthalic anhydride waste residue powder and ethanolamine in step (1) is 2:5-3:5; The reaction temperature in step (1) is 120-130°C; In the step (2), the volume ratio of ice water or saturated brine to phthalic anhydride slag aminolysis solution is 2:1-5:1.

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