CN116283637A - Novel method for synthesizing terephthalamide - Google Patents

Abstract

The invention belongs to the field of chemical synthesis, and discloses a novel method for synthesizing terephthalamide, which is characterized in that terephthalic acid and low-melting-point acid are compounded according to a proper proportion, and ammonia gas is introduced to react for proper time at a certain temperature and under a certain pressure under the participation of a proper catalyst, so that both the terephthalic acid and the low-melting-point acid are amidated. The proper temperature is controlled and the mixture is filtered when the mixture is hot. The filter cake (solid) is terephthalamide, and the filtrate is low-melting-point acid to generate corresponding amide. Washing the filter cake with proper solvent while hot, and vacuum drying at 150 ℃ to obtain the high-purity terephthalamide. The combined filtrate (the amide generated by low-melting point acid and the washing liquid generated by hot washing of filter cake) is cooled, crystallized and filtered, and vacuum-dried at 70 ℃ to obtain the amide generated by low-melting point acid.

Description

Novel method for synthesizing terephthalamide

Technical Field

The invention belongs to the field of chemical synthesis, and particularly relates to a method for synthesizing terephthalamide.

Technical Field

Terephthalamide is an important chemical intermediate and has wide application in the fields of synthetic materials, medicines, pesticides, fine organic synthesis and the like.

Terephthalic acid is mainly used as a raw material in industry, terephthaloyl chloride is prepared through an acyl chlorination reaction, and then terephthalamide is obtained through a reaction with ammonia gas (CN 1422843A; journalof theAmericanChemicalSociety,2013,16853.). Common acyl chloride reagents are thionyl chloride, phosphorus trichloride, phosphorus pentachloride, phosgene, etc. The reaction condition of the route is mild, the operation is simple, the product yield is higher, but a large amount of chlorine-containing byproducts are generated, the wastewater discharge amount is large, and the production cost is higher.

It has been reported that terephthalonitrile was hydrolyzed at 80℃for 6 hours under the catalysis of iridium complexes to give 93% terephthalamide (Inorganic chemistry,2020,59 (22): 16582.). The method has clean process and mild condition, but has limited sources of terephthalonitrile, and has higher cost by using a noble metal catalyst. Joshi et al (GreenChemicals, 2019,21 (5): 962) reported that terephthalamide was obtained by oxidation of p-dibenzylamine as a starting material with tetrabutylammonium hydroxide as a catalyst with oxygen at 70℃for 12 hours. The method has mild conditions and clean process, but the prices of the dibenzylamine and the catalyst are higher, and the cost is higher. In general, these methods have mild reaction conditions, but the raw materials are too costly to be suitable for industrial production.

The ammonolysis of terephthalamide is a more cost-effective process. Chinese patent CN113773220 reports that terephthalic acid ester can be reacted with ammonia gas in methanol medium at 80 ℃ under pressure for 24 hours to obtain 85% terephthalamide. There are also documents (Shan Yuhua, petrochemical industry, 2004, 33 (1): 51-3; wo2012123328; wo2012014760; chemistry-AnAsianJ,2015, 2631-2650) reporting a synthetic method for synthesizing terephthalamide with ammonia or aqueous ammonia in a solvent under the action of a catalyst at high temperature and high pressure. The method has harsh reaction conditions, complex process and high equipment requirement, and the production cost is high.

In order to reduce the production cost and reduce the three-waste emission, chinese patent CN105016939 discloses a method, which is to add a proper amount of terephthalic acid into a reaction kettle, charge ammonia gas with the mole number of 2.6 times of that of terephthalic acid, or add ammonium bicarbonate powder with the mole number of 2.8 times of that of terephthalic acid, seal the reaction kettle, and make the reaction at 305-320 ℃ for 0.5h under the stirring condition to obtain terephthalamide. The method adopts cheap raw materials and solvent-free (dry) high-temperature reaction, can effectively reduce the emission of three wastes, but has the defects of high reaction temperature (sublimation at the temperature of more than 300 ℃ of terephthalic acid), high-temperature solid-phase operation difficulty, high equipment requirement and the like.

Disclosure of Invention

The purpose of the invention is that: the novel technology for producing the terephthalamide is provided, and the terephthalamide and the low-melting-point amide are produced through co-dissolution amidation, so that pollutant emission is reduced, production cost is lowered, and the yield and purity of the terephthalamide are improved.

In order to achieve the above purpose, the invention adopts the following technical scheme:

1. terephthalic acid and low-melting-point acid are compounded, ammonia gas is introduced to react under certain reaction temperature and pressure in the presence of a catalyst, so that both terephthalic acid and the low-melting-point acid are amidated.

2. The proper temperature is controlled and the mixture is filtered when the mixture is hot. The filter cake (solid) is terephthalamide, and the filtrate is low-melting-point acid to generate corresponding amide. Washing the filter cake with a proper solvent while the filter cake is hot, and vacuum drying to obtain the high-purity terephthalamide.

3. And (3) cooling, crystallizing, filtering and vacuum drying the combined filtrate (the amide filtrate generated by the low-melting-point acid is combined with the washing liquid generated by the hot washing of the filter cake) to obtain the amide generated by the low-melting-point acid.

Further, the low melting point acid means an acid having a melting point lower than that of terephthalic acid. The low melting point acid selected is an acid having a melting point less than 427 c, if the melting point of terephthalic acid is 427 c. Meanwhile, the acid strength of the low-melting-point acid is required to be smaller than that of terephthalic acid, so that the refractory terephthalic acid can be subjected to amidation reaction preferentially to generate a target product. The acid strength constant PKa of terephthalic acid is 3.5, and it is required that the acid strength constant PKa of the low-melting acid is greater than 3.5 (the greater the PKa value, the smaller the corresponding acid strength). Suitable low melting acids may be, for example: isooctanoic acid (melting point-59 ℃, PKa 4.8), oleic acid (melting point 14 ℃, PKa 4.8), glutaric acid (melting point 98 ℃, PKa 4.4), adipic acid (melting point 152 ℃, PKa 4.5), and the like.

Further, the compounding ratio of terephthalic acid to low-melting-point acid is 1:0.5-1.5 (weight ratio);

further, the catalyst is a proton acid and a lewis acid that catalyze an amidation reaction of an acid. Suitable are: sulfuric acid, phosphoric acid (phosphotungstic acid), zinc compounds (zinc oxide, zinc acetate), tin compounds (stannous oxide, butylstannic acid), and the like. The dosage of the catalyst is 0.05 to 0.5 percent of the total weight of terephthalic acid and low-melting point acid;

further, the amidation reaction temperature is 250 to 300 ℃. The amidation reaction pressure is maintained by introducing ammonia gas, and is generally 0.3-0.7 MPa;

further, the proper time for the reaction by passing ammonia gas is the time required for amidation of terephthalic acid and a so-called low melting point acid, and is usually 6 to 12 hours.

Further, the hot filtration is carried out by controlling the appropriate temperature depending on the melting point of the corresponding amide formed by the low melting point acid, and the appropriate temperature is 20 to 50 ℃ higher than the melting point of the corresponding amide formed by the low melting point acid to ensure the separation from terephthalamide by filtration. The specific method is as follows: the iso-octoic acid amide melting point is 102 ℃, and a suitable heat filtration temperature is 122-172 ℃. The oleamide melting point is 77℃and the appropriate heat filtration temperature is 97-127 ℃. The glutaramide melting point is 98℃and the appropriate heat filtration temperature is 118-148 ℃. The adipoylamine melting point is 220℃and the appropriate heat filtration temperature is 240 to 270 ℃.

Further, a proper solvent is selected to wash the filter cake while the filter cake is hot, and the high-purity terephthalamide is obtained. Suitable solvents are those which dissolve the corresponding amides of the low-melting acids, but not the terephthalamides. These solvents are dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, butyronitrile and the like.

Further, a proper solvent is selected to wash the filter cake while the filter cake is hot, wherein the washing of the filter cake while the filter cake is hot means that the filter cake is washed at 100-160 ℃. The filter cake is washed by maintaining the temperature range, so that the solvent can well dissolve amide generated by low-melting-point acid, but not terephthalamide, thereby obtaining terephthalamide with high purity and high yield.

Further, combining the filtrates, cooling and crystallizing; wherein the crystallization temperature is 30-80 ℃ and the crystallization time is 6-12 hours. The low melting point acid produces a low melting point amide having a melting point lower than the melting point of terephthalamide.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention uses low-melting point acid and the corresponding low-melting point amide as reaction medium to promote amidation reaction. During the high temperature copolyamidation reaction, the low melting acid melts to act as a reaction medium, amidating both terephthalic acid and the so-called low melting acid. The low-melting acid amide produced also serves as a flowing medium for solid particles of terephthalamide under high-temperature conditions, so that the material is easy to transport. No water, or alcohol, or other solvent is required to act as a reaction medium. Reactions at high temperature solid phases (such as CN 105016939) are also avoided, which have two disadvantages: firstly, the reaction is difficult to be uniform, and secondly, the solid phase materials are difficult to be conveyed during large-scale production.

2. The invention has no addition of traditional solvent or medium to the reaction system and no three wastes discharge. The technology of the invention is clean, efficient and low in cost. The material, which is the solvent or medium, is finally also converted into the product. The technology provides a new operation mode for the solid-phase material system reaction.

3. The addition of low melting point weak acid is beneficial to generating higher ammonia concentration in the reaction liquid phase and promoting the rapid amidation of terephthalic acid.

4. The technology of the invention uses acid with lower acid strength and much lower melting point as a medium, so that the target product terephthalic acid can be preferably and completely converted into terephthalamide. The low melting point amide formed has a melting point well below that of terephthalamide (greater than 500 ℃), which in turn makes it easy to isolate terephthalamide by hot filtration.

Drawings

FIG. 1 is a schematic diagram of a co-solvent amidation process for producing terephthalamide and low melting amides.

Detailed description of the preferred embodiments

The invention is further described below in connection with examples, but is not limited thereto.

Example 1: isooctanoic acid as low-melting point copolyamidated acid

1. 166g of terephthalic acid (mass content: 99.8%) and 83g of isooctanoic acid (mass content: 99.5%) and 0.1245g of concentrated sulfuric acid were charged into a high-pressure reaction vessel, and the air in the vessel was replaced with ammonia gas. Heating to 250 ℃, introducing ammonia gas, maintaining the ammonia gas pressure of 0.3MPa for reaction for 10 hours, amidating both terephthalic acid and isooctanoic acid (using liquid chromatography for tracking analysis), stopping introducing the ammonia gas, and ending the reaction.

2. After the reaction, the temperature of the material is reduced to 172 ℃, and the material is filtered when the material is hot. The filter cake (solid) is terephthalamide, and the filtrate is isooctanoic acid amide. The filter cake was washed with butyronitrile at 100℃while hot and dried in vacuo at 150℃to give 160.7g of terephthalamide with a purity of 99.2% and a yield of 97.4%. The isooctanoic acid amide adhering to the filter cake is washed out by the hot butyronitrile and enters the filtrate.

3. The combined filtrate (172 ℃ C. Filtrate isooctanoic acid amide and washing solution generated by hot washing of filter cake) was cooled to 50 ℃ C. And crystallized for 12 hours, and then filtered, and dried under vacuum at 70 ℃ C. To obtain 79.7g of solid isooctanoic acid amide, which has a melting point of 100-102 ℃ C., a purity of 98.8%, and a yield of 96.0%.

Example 2: oleic acid as low-melting copolyamidated acid

1. 166g of terephthalic acid (the mass content is more than 99.8%) and 166g of oleic acid (the mass content is 98.0%) are added into a high-pressure reaction kettle, and 0.332g of phosphotungstic acid are added into the high-pressure reaction kettle to replace air in the kettle by ammonia gas. Heating to 260 ℃, introducing ammonia gas, maintaining the ammonia gas pressure of 0.5MPa for reaction for 6 hours, amidating both terephthalic acid and oleic acid (using liquid chromatography for tracking analysis), stopping introducing the ammonia gas, and ending the reaction.

2. After the reaction, the temperature of the material is reduced to 117 ℃ and the material is filtered when the material is hot. The filter cake (solid) is terephthalamide and the filtrate is oleamide. The filter cake was washed with N-dimethylformamide at 120℃while it is hot and dried under vacuum at 150℃to give 161.6g of terephthalamide with a purity of 99.5% and a yield of 98.2%. The oleamide adhering to the filter cake is washed out by hot N-dimethylformamide and enters the filtrate.

3. The combined filtrate (filtrate oleamide at 117 ℃ C. And washing solution generated by hot washing of the filter cake) was cooled to 30 ℃ C. And crystallized for 10 hours, and then filtered, and dried under vacuum at 70 ℃ C. To obtain 157.9g of solid oleamide, which has a melting point of 75-76 ℃ C. And a purity of 98.1%, and a yield of 95.6%.

Example 3: glutaric acid as low-melting point copolyamidated acid

1. 166g of terephthalic acid (mass content more than 99.8%) and 207.5g of glutaric acid (mass content more than 98.0%) and 1.121g of stannous oxide were added to the autoclave, and the air in the autoclave was replaced with ammonia gas. Heating to 280 ℃, introducing ammonia gas, maintaining the ammonia gas pressure of 0.6MPa for reaction for 12 hours, amidating both terephthalic acid and glutaric acid (using liquid chromatography for tracking analysis), stopping introducing ammonia gas, and ending the reaction.

2. After the reaction, the temperature of the material is reduced to 128 ℃, and the material is filtered when the material is hot. The filter cake (solid) is terephthalamide and the filtrate is glutaramide. The filter cake was washed with dimethyl sulfoxide at 140℃while hot and dried in vacuo at 150℃to give 159.8g of terephthalamide with a purity of 99.6% and a yield of 97.6%. The glutaramide adhering to the filter cake is washed out by hot dimethyl sulfoxide and enters the filtrate.

3. The combined filtrate (the filtrate of the glutaramide at 128 ℃ C. And the washing solution generated by hot washing the filter cake) is cooled to 60 ℃ C. For crystallization for 8 hours, then filtered, and dried in vacuum at 70 ℃ C. To obtain 199.8g of solid glutaramide, the melting point of which is 96-97 ℃ C., the purity of which is 97.9%, and the yield of which is 97.7%.

Example 4: adipic acid as low melting point copolyamidated acid

1. 166g of terephthalic acid (mass content more than 99.8%) and 249g of adipic acid (mass content more than 99.0%) and 2.075g of zinc acetate are added into a high-pressure reaction kettle, and the air in the kettle is replaced by ammonia gas. Heating to 300 ℃, introducing ammonia gas, maintaining the ammonia gas pressure of 0.7MPa for reaction for 8 hours, amidating both terephthalic acid and adipic acid (using liquid chromatography for tracking analysis), stopping introducing the ammonia gas, and ending the reaction.

2. After the reaction, the temperature of the material is reduced to 240 ℃, and the material is filtered when the material is hot. The filter cake (solid) was terephthalamide and the filtrate was adipoylamine. The filter cake was washed with N-methylpyrrolidone at 160℃while it is hot and dried under vacuum at 150℃to give 158.8g of terephthalamide with a purity of 99.8% and a yield of 97.0%. The adipoylamine adhering to the filter cake is washed out by hot N-methylpyrrolidone and enters the filtrate.

3. The combined filtrate (filtrate adipoamide at 240 ℃ C. And washing solution generated by hot washing of the filter cake) was cooled to 80 ℃ C. And crystallized for 6 hours, then filtered, and dried under vacuum at 70 ℃ C. To obtain 237.7g of solid adipoamide, the melting point of which is 216-218 ℃ C., the purity of which is 98.2%, and the yield of which is 96.0%.

Comparative example 1:1, 3-malonic acid as low-melting point copolyamidated acid

1. 166g of terephthalic acid (content greater than 99.8%) and 83g of malonic acid (content greater than 98.5%, melting point 152 ℃, pka=2.9) were added to the autoclave, 0.1245g of concentrated sulfuric acid was added, and the air in the autoclave was replaced with ammonia. Raising the temperature to 250 ℃, introducing ammonia gas, maintaining the ammonia gas pressure of 0.3MPa for reaction for 5 hours, and fully amidating malonic acid, wherein 39.8% of terephthalic acid is still not amidated (analyzed by liquid chromatography tracking), and continuing the reaction for 14 hours, so that the terephthalic acid is completely converted. Stopping introducing ammonia gas, and ending the reaction. The reaction was carried out for 19 hours.

2. After the reaction, the temperature of the materials is reduced to 220 ℃, and the materials are filtered when the materials are hot. The filter cake (solid) was terephthalamide and the filtrate was malonamide (melting point 170 ℃). The filter cake was washed with N-methylpyrrolidone at 160℃while it is hot and dried under vacuum at 150℃to give 156.4g of terephthalamide with a purity of 97.3% and a yield of 93.0%. The malonamide adhering to the filter cake is washed out by hot N-methylpyrrolidone into the filtrate.

3. The combined filtrate (filtrate malononimide at 220 ℃ C. And washing solution generated by hot washing of the filter cake) was cooled to 30 ℃ C. And crystallized for 12 hours, and then filtered, and dried under vacuum at 70 ℃ C. To obtain 77.7g of solid malononimide, the melting point of which is 167-169 ℃ C., the purity of which is 99.4%, and the yield of which is 96.3%.

As seen from comparative example 1, the low melting point acid eutectic amidation reaction using relatively higher acid strength than terephthalic acid brings about the disadvantages that: 1. the amidation reaction of terephthalic acid is significantly slowed down. Because malonic acid, which has higher acid strength than terephthalic acid, is preferentially converted to an amide, the environment of the amidation reaction medium of terephthalic acid is changed. In example 1, terephthalic acid is preferentially reacted, the reaction medium is mainly isooctanoic acid, and ammonia which is easy to complex with alkali enters a liquid phase (namely, the ammonia concentration of the liquid phase is higher) and reacts with solid-phase strong acid terephthalic acid, so that terephthalic acid is completely amidated in a short time. 2. The amide product of terephthalic acid is of low purity. Since terephthalic acid is basically amidated in a malonamide medium in the latter stage of the reaction, ammonia is low in liquid phase concentration, so that the intermediate product is not easy to be completely converted into terephthalamide, and the yield and purity of the terephthalamide product are low.

Comparative example 2: method of adding solvent (without adding low melting point acid)

166g of terephthalic acid (mass content: 99.8%) and 83g of N, N-dimethylformamide and 0.1245g of concentrated sulfuric acid were charged into a high-pressure reactor, and the air in the reactor was replaced with ammonia gas. Heating to 250 ℃, introducing ammonia gas, maintaining the ammonia gas pressure at 0.3MPa for reaction for 22 hours, then completely converting terephthalic acid (using liquid chromatography for tracking analysis), stopping introducing the ammonia gas, and ending the reaction. After the reaction, the material was filtered hot at 172 ℃.

The filter cake is terephthalamide. The filter cake was washed with butyronitrile at 100℃while hot and dried in vacuo at 150℃to give 157.9g of terephthalamide, 99.0% purity and 95.5% yield.

As is apparent from comparative example 2, the addition of a solvent without adding a low melting point acid affects the yield and purity of the phthalamide, and the reaction rate is significantly reduced to the maximum (see example 1). Because the low-melting weak acid is added in the embodiment of the invention, the high ammonia concentration in the reaction liquid phase is facilitated, and the rapid amidation of terephthalic acid is promoted.

Claims (11)

1. A novel method for synthesizing terephthalamide is characterized in that:

(1) Compounding terephthalic acid and low-melting-point acid, adding a catalyst, adjusting the reaction temperature, introducing ammonia gas, and maintaining a certain reaction pressure to perform amidation reaction on the terephthalic acid and the low-melting-point acid;

(2) Filtering while the reaction is hot, collecting a filter cake, washing the filter cake while the reaction is hot with a solvent, and drying to obtain terephthalamide; and collecting amide generated by low-melting-point acid from the filtrate and the washing liquid.

Wherein the low melting point acid means an aliphatic carboxylic acid having a melting point less than that of terephthalic acid and an acid strength less than that of terephthalic acid.

2. The novel process for synthesizing terephthalamide according to claim 1, wherein: the weight ratio of terephthalic acid to low-melting point acid in the step (1) is 1:0.5-1.5.

3. The novel process for synthesizing terephthalamide according to claim 1, wherein: the catalyst in the step (1) is protonic acid and/or Lewis acid capable of catalyzing the acid to carry out amidation reaction, and the dosage of the catalyst is 0.05-0.5% of the total weight of terephthalic acid and low-melting point acid.

4. The novel process for synthesizing terephthalamide according to claim 1, wherein: the reaction temperature is 250-300 ℃; introducing ammonia gas to maintain the pressure at 0.3-0.7 MPa; the amidation reaction time is 6-12 hours.

5. The novel process for synthesizing terephthalamide according to claim 1, wherein: low melting point acids refer to acids having a melting point less than 427 ℃ and an acid strength constant PKa greater than 3.5.

6. The novel process for synthesizing terephthalamide according to claim 5, wherein: the low-melting point acid is one of isooctanoic acid, oleic acid, glutaric acid and adipic acid.

7. The novel process for synthesizing terephthalamide according to claim 1, wherein: the temperature of the hot filtration in the step (2) is 20-50 ℃ higher than the melting point of the corresponding amide generated by the low-melting point acid.

8. The novel process for synthesizing terephthalamide according to claim 1, wherein: the washing solvent in the step (2) is a solvent which can dissolve the corresponding amide formed by the low-melting point acid, but not the terephthalamide.

9. The novel process for synthesizing terephthalamide according to claim 8, wherein: the solvent in the step (2) is one or more of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and butyronitrile.

10. The novel process for synthesizing terephthalamide according to claim 1, wherein: washing the filter cake while it is hot means washing at 100-160 ℃.

11. The novel process for synthesizing terephthalamide according to claim 1, wherein: and collecting the low-melting-point acid from the filtrate and the washing liquid to obtain the amide specifically comprises the following components: and combining the filtrate with a washing solution generated by hot washing the filter cake, cooling to 30-80 ℃ for crystallization, filtering and drying to obtain the amide generated by the low-melting-point acid.

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