CN110563570A - Method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid - Google Patents
Method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid Download PDFInfo
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- C07C209/62—Preparation of compounds containing amino groups bound to a carbon skeleton by cleaving carbon-to-nitrogen, sulfur-to-nitrogen, or phosphorus-to-nitrogen bonds, e.g. hydrolysis of amides, N-dealkylation of amines or quaternary ammonium compounds
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Abstract
the invention belongs to the field of recycling and resource utilization of waste high polymer materials, and particularly relates to a method for preparing terephthalic acid and p-phenylenediamine by degrading para-aramid. Mainly solves the technical problem of recycling the para-aramid. According to the invention, the amide bond is selectively broken by utilizing metal ion coordination catalysis, and the para-aramid is controllably degraded through the exchange reaction of organic carboxylic acid and the amide bond, so that the terephthalic acid and the p-phenylenediamine acyl derivative are obtained. The terephthalic acid can be separated firstly by utilizing the water solubility and acidification precipitation characteristics of the terephthalate. Then, strong base is used as a catalyst to carry out alcoholysis reaction on the p-phenylenediamine acyl derivative, and p-phenylenediamine is separated out through cooling crystallization. The invention realizes the controllable chemical degradation of para-aramid and recovers and prepares monomer terephthalic acid and p-phenylenediamine.
Description
Technical Field
The invention belongs to the field of recycling and resource utilization of waste high polymer materials, and particularly relates to a method for preparing terephthalic acid and p-phenylenediamine by degrading para-aramid.
Background
the poly (p-phenylene terephthalamide) can be prepared by direct polycondensation of terephthalic acid and p-phenylenediamine or by polycondensation of terephthaloyl chloride and p-phenylenediamine. It belongs to a lyotropic liquid crystal polymer and can be processed into fibers called aramid 1414 or para-aramid, and the product name of DuPont is Kevlar. Currently, the major producers of aramid fiber in the world are the us dupont company and the japanese imperial company, and the aramid fiber yields of both companies add up to approximately 79.1% of the global production capacity. In 2016, the production capacity of the p-aramid fiber is about 81kt/a, and the total production capacity of DuPont and Diren is 74kt/a, so that DuPont is the biggest p-aramid fiber production company in the world at present. With the continuous improvement of the production technology, the production cost of the aramid fiber is reduced day by day, so that the application field of the aramid fiber is promoted to be continuously expanded, and the demand is continuously increased. The production capacity of the aramid fiber 1414 in 2016 of China reaches 4200t/a, wherein the production capacity of the Futaitai and new material company Limited is 1500t/a, and the production scale is the largest; the production capacity of the blue star new material company Limited is 1000t/a, and the blue star new material company is located secondly.
the para-aramid fiber is a high-performance fiber, has excellent performances of high strength, high modulus, high temperature resistance, acid and alkali resistance, light weight and the like, has the specific strength of 5-6 times that of a steel wire, the specific modulus of 2-3 times that of the steel wire or glass fiber, the toughness of 2 times that of the steel wire and the weight of only about 20 percent of that of the steel wire, and therefore, has wide application in the fields of national defense and civil use. Para-aramid fiber is an important national defense and military material, in order to meet the requirements of modern wars, body armor of developed countries such as America, English and the like is made of aramid fiber, and the aramid fiber body armor and helmets are light in weight, so that the rapid response capability and the killing power of army are effectively improved. Besides military applications, para-aramid has been widely used as a high-technical-content fiber material in various fields such as aerospace, electromechanics, buildings, automobiles, sports goods and the like. At present, because the yield of the para-aramid is relatively low, the recycling problem of the waste para-aramid fibers does not attract extensive attention in the industry and the research field. However, the chemical properties of the waste para-aramid are relatively stable, and the waste para-aramid cannot be decomposed and converted in natural environment, so that the waste para-aramid can be used as solid waste to influence the environment to a certain extent. Meanwhile, the waste para-aramid contains terephthalic acid and p-phenylenediamine structural units with high added values, and if the waste para-aramid can be recycled, the resource waste can be reduced. The application prospect of the para-aramid is wide, the recycling of the waste para-aramid in the future limits the large-scale production application of the waste para-aramid, the para-aramid is chemically degraded to recycle monomer polymers of the waste para-aramid, an industrial chain of the para-aramid industrial production is perfected, and a closed loop is formed.
Disclosure of Invention
the invention provides a method for preparing terephthalic acid and p-phenylenediamine by degrading para-aramid for solving the technical problem of recycling para-aramid.
A method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: mixing a soluble metal salt catalyst and a reaction solvent to prepare a reaction system I, mixing the para-aramid fiber and the reaction system I, adding the mixture into a reaction kettle, sealing the reaction kettle, and then putting the reaction kettle into a homogeneous reactor for heating reaction; cooling to room temperature after the reaction is finished, adding deionized water for washing, and filtering to remove the catalyst and the reaction solvent, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives; adding a strong base aqueous solution, dissolving the generated salt of the terephthalic acid, and filtering and separating to obtain a p-phenylenediamine acyl derivative and a terephthalic acid salt solution; adding hydrochloric acid into the terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain terephthalic acid;
Step 2: preparing a reaction system II from strong base and a reaction solvent, mixing the p-phenylenediamine acyl derivative prepared in the step 1 and the reaction system II, adding the mixture into a reaction kettle, sealing the reaction kettle, and then putting the reaction kettle into a homogeneous reactor for heating reaction; and cooling to room temperature after the reaction is finished, evaporating the organic solvent to remove the organic solvent, adding deionized water into the product, cooling, and separating out crystals, namely p-phenylenediamine. The method obviously reduces the degradation temperature of para-aramid through metal ion coordination catalysis; monomers with high added values, namely terephthalic acid and p-phenylenediamine, can be recovered through a two-step method, and the recovery method is simple and easy to implement and does not produce secondary pollution.
The invention utilizes soluble metal salt catalyst to selectively activate amido bond in para-aramid fiber, controllably degrade para-aramid fiber, and recover terephthalic acid and p-phenylenediamine through separation and purification of degradation products. The structural formula of the para-aramid is shown as follows:
wherein n is more than or equal to 1 and less than or equal to 1000.
Further, the soluble metal salt catalyst in step 1 is any one of aluminum chloride, ferric chloride, copper chloride, zinc chloride, aluminum sulfate, ferric sulfate, copper sulfate, zinc sulfate, aluminum nitrate, ferric nitrate, copper nitrate, zinc nitrate, aluminum acetate, ferric acetate, copper acetate or zinc acetate. The catalyst selected by the scheme has a good coordination catalysis effect on amido bonds, and has a good catalysis effect on selective breakage of the amido bonds.
still further, the reaction solvent in step 1 is an organic carboxylic acid solvent, including formic acid, acetic acid or propionic acid. The micromolecular organic carboxylic acid selected by the scheme has good swelling effect and reaction performance on degradation of the para-aramid fiber.
Furthermore, the mass fraction of the soluble metal salt catalyst in the reaction solvent in the reaction system I in the step 1 is 1-50%; the mass ratio of the para-aramid fiber to the reaction system I in the step 1 is 1: 1-100. Within the range of the technical scheme, the degradation of the para-aramid is sufficient.
Furthermore, the heating reaction temperature in the step 1 is 100-280 ℃, and the reaction time is 1-72 hours. Within the range of the technical scheme, the para-aramid can be fully degraded.
Furthermore, the concentration of the strong alkali aqueous solution in the step 1 is 1-20%, and the strong alkali is potassium hydroxide, sodium hydroxide or lithium hydroxide. Within the range of the technical scheme, the terephthalic acid can be fully converted into terephthalate to be dissolved in water, thereby being beneficial to the separation of the terephthalic acid.
Further, the strong base in step 2 is potassium hydroxide, sodium hydroxide or lithium hydroxide. According to the technical scheme, strong base is selected as a catalyst, so that the p-phenylenediamine acyl derivative can directly react to generate the p-phenylenediamine.
Further, the reaction solvent in step 2 is an alcohol solvent, including methanol, ethanol, n-propanol or isopropanol. The selected micromolecule alcohols in the technical scheme are used as solvents, and can react with p-phenylenediamine acyl derivatives under the condition that strong alkali is used as a catalyst to recover p-phenylenediamine.
Furthermore, the mass fraction of the strong base in the reaction solvent in the reaction system II in the step 2 is 1-50%; the mass ratio of the p-phenylenediamine acyl derivative in the step 2 to the reaction system II is 1: 1-100. Within the range of the technical scheme, the p-phenylenediamine acyl derivative can be completely reacted to generate the p-phenylenediamine.
Furthermore, the heating reaction temperature in the step 2 is 100-280 ℃, and the reaction time is 1-72 hours; the cooling temperature in the step 2 is-20-0 ℃, and the cooling time is 1-24 hours. Within the range of the reaction conditions of the technical scheme, the p-phenylenediamine acyl derivative can be completely reacted to generate p-phenylenediamine; within the cooling condition range of the technical scheme, p-phenylenediamine can be separated out.
Compared with the prior art, the invention has the following beneficial effects:
(1) the para-aramid is controllably degraded by selectively activating amide bonds, and monomers with high added values, namely p-phenylenediamine and terephthalic acid, are recovered.
(2) The reaction process has relatively mild conditions, and the solvent and the catalyst used in the reaction process can be recycled.
Drawings
FIG. 1 is a nuclear magnetic resonance carbon spectrum of a recovered terephthalic acid monomer;
FIG. 2 is the NMR spectrum of the recovered p-phenylenediamine monomer.
Detailed Description
The following embodiments of the present invention will be described in detail with reference to the accompanying examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features in the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
Example 1
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from aluminum chloride and formic acid according to 10% of the mass fraction of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:1, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 280 ℃, and reacting for 36 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove aluminum chloride and formic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding potassium hydroxide aqueous solution, dissolving potassium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the potassium terephthalate salt solution. Adding hydrochloric acid into potassium terephthalate salt solution to precipitate terephthalic acid, washing, filtering and drying to obtain terephthalic acid.
Step 2: preparing a reaction system II from potassium hydroxide and methanol according to the mass fraction of 20%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:30, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 220 ℃, and reacting for 24 hours. And cooling to room temperature after the reaction is finished, evaporating and removing the methanol, adding deionized water into the product, cooling for 12 hours at the temperature of minus 10 ℃, and separating out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 2
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from ferric chloride and acetic acid according to the mass percent of 1% of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:50, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 180 ℃, and reacting for 1 hour. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove ferric chloride and acetic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding sodium hydroxide aqueous solution, dissolving sodium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the sodium terephthalate aqueous solution. Adding hydrochloric acid into the sodium terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing a reaction system II from sodium hydroxide and ethanol according to the mass fraction of 15%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:20, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 200 ℃, and reacting for 8 hours. And cooling to room temperature after the reaction is finished, evaporating ethanol to remove the ethanol, adding deionized water into the product, and cooling at the temperature of minus 20 ℃ for 16 hours to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
example 3
in this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from copper sulfate and propionic acid according to the mass percent of a catalyst of 30%, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:100, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 100 ℃, and reacting for 72 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove copper sulfate and propionic acid to obtain reaction products, namely terephthalic acid and p-phenylenediamine acyl derivatives. Adding lithium hydroxide aqueous solution, dissolving lithium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the terephthalic acid lithium salt solution. And (3) adding hydrochloric acid into the terephthalic acid lithium salt solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing lithium hydroxide and n-propanol into a reaction system II according to the mass fraction of 1%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:70, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the reaction kettle to 100 ℃, and reacting for 72 hours. And cooling to room temperature after the reaction is finished, evaporating and removing the n-propanol, adding deionized water into the product, and cooling for 24 hours at the temperature of 0 ℃ to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 4
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from zinc nitrate and acetic acid according to the mass fraction of 50% of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:10, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 160 ℃, and reacting for 48 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove zinc nitrate and acetic acid to obtain reaction products, namely terephthalic acid and p-phenylenediamine acyl derivatives. Adding sodium hydroxide aqueous solution, dissolving sodium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the sodium terephthalate aqueous solution. Adding hydrochloric acid into the sodium terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing sodium hydroxide and isopropanol into a reaction system II according to the mass fraction of 40%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:60, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 220 ℃, and reacting for 10 hours. And cooling to room temperature after the reaction is finished, evaporating isopropanol to remove the isopropanol, adding deionized water into the product, cooling for 20 hours at the temperature of minus 15 ℃, and separating out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 5
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from zinc acetate and formic acid according to the mass percent of 30 percent of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:70, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 200 ℃, and reacting for 36 hours. After the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove zinc acetate and formic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding potassium hydroxide aqueous solution, dissolving potassium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the potassium terephthalate salt solution. Adding hydrochloric acid into potassium terephthalate salt solution to precipitate terephthalic acid, washing, filtering and drying to obtain terephthalic acid.
Step 2: preparing a reaction system II from potassium hydroxide and methanol according to the mass fraction of 15%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:80, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the reaction kettle to 150 ℃, and reacting for 60 hours. And cooling to room temperature after the reaction is finished, evaporating and removing the methanol, adding deionized water into the product, and cooling for 20 hours at the temperature of minus 10 ℃ to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
example 6
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
step 1: preparing a reaction system I from aluminum acetate and acetic acid according to 35% of the mass fraction of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:90, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 250 ℃, and reacting for 50 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove aluminum acetate and acetic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding sodium hydroxide aqueous solution, dissolving sodium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the sodium terephthalate aqueous solution. Adding hydrochloric acid into the sodium terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
step 2: preparing a reaction system II from sodium hydroxide and ethanol according to the mass fraction of 50%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:100, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the reaction kettle to 100 ℃, and reacting for 72 hours. And cooling to room temperature after the reaction is finished, evaporating the organic solvent to remove the organic solvent, adding deionized water into the product, and cooling for 24 hours at the temperature of minus 20 ℃ to separate out crystals, namely p-phenylenediamine.
in particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 7
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing a reaction system I from zinc chloride and formic acid according to the mass fraction of 10% of a catalyst, mixing the para-aramid fiber and the reaction system I according to the mass ratio of 1:20, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 180 ℃, and reacting for 24 hours. After the reaction is finished, cooling to room temperature, adding deionized water for washing, filtering to remove zinc chloride and formic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding potassium hydroxide aqueous solution, dissolving potassium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the potassium terephthalate salt solution. Adding hydrochloric acid into potassium terephthalate salt solution to precipitate terephthalic acid, washing, filtering and drying to obtain terephthalic acid.
Step 2: preparing a reaction system II from potassium hydroxide and ethanol according to the mass fraction of 15%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:20, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the reaction kettle to 250 ℃, and reacting for 1 hour. And cooling to room temperature after the reaction is finished, evaporating ethanol to remove the ethanol, adding deionized water into the product, and cooling at the temperature of minus 20 ℃ for 1 hour to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 8
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: copper nitrate and acetic acid are prepared into a reaction system I according to the mass fraction of 30% of a catalyst, para-aramid fiber and the reaction system I are mixed according to the mass ratio of 1:60 and added into a reaction kettle, and the reaction kettle is sealed and then placed into a homogeneous reactor to be heated to 200 ℃ for reaction for 36 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove copper nitrate and acetic acid to obtain reaction products, namely terephthalic acid and p-phenylenediamine acyl derivatives. Adding sodium hydroxide aqueous solution, dissolving sodium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the sodium terephthalate aqueous solution. Adding hydrochloric acid into the sodium terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing sodium hydroxide and methanol into a reaction system II according to the mass fraction of 40%, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:1, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 180 ℃, and reacting for 20 hours. And cooling to room temperature after the reaction is finished, evaporating and removing the methanol, adding deionized water into the product, cooling for 1h at the temperature of minus 10 ℃, and separating out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 9
In this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: copper chloride and propionic acid are prepared into a reaction system I according to the mass fraction of 20% of a catalyst, para-aramid fiber and the reaction system I are mixed according to the mass ratio of 1:30 and added into a reaction kettle, and the mixture is sealed and then placed into a homogeneous reactor to be heated to 230 ℃ for reaction for 12 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove copper chloride and propionic acid, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives. Adding lithium hydroxide aqueous solution, dissolving lithium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the terephthalic acid lithium salt solution. And (3) adding hydrochloric acid into the terephthalic acid lithium salt solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing 45% of lithium hydroxide and isopropanol by mass percent to prepare a reaction system II, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:60, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 190 ℃, and reacting for 60 hours. And cooling to room temperature after the reaction is finished, evaporating isopropanol to remove the isopropanol, adding deionized water into the product, and cooling at the temperature of minus 5 ℃ for 24 hours to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
Example 10
in this embodiment, a method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid comprises the following steps:
Step 1: preparing ferric nitrate and acetic acid into a reaction system I according to the mass fraction of a catalyst of 15%, mixing the para-aramid fiber and the reaction system according to the mass ratio of 1:60, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 250 ℃, and reacting for 12 hours. And after the reaction is finished, cooling to room temperature, adding deionized water for washing, and filtering to remove ferric nitrate and acetic acid to obtain reaction products, namely terephthalic acid and p-phenylenediamine acyl derivatives. Adding sodium hydroxide aqueous solution, dissolving sodium salt generated by terephthalic acid, and filtering and separating to obtain the p-phenylenediamine acyl derivative and the sodium terephthalate aqueous solution. Adding hydrochloric acid into the sodium terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain the terephthalic acid.
Step 2: preparing a reaction system II from 25% of sodium hydroxide and ethanol by mass percent, mixing the p-phenylenediamine acyl derivative and the reaction system II according to the mass ratio of 1:80, adding the mixture into a reaction kettle, sealing the reaction kettle, putting the reaction kettle into a homogeneous reactor, heating the mixture to 160 ℃, and reacting for 72 hours. And cooling to room temperature after the reaction is finished, evaporating ethanol to remove the ethanol, adding deionized water into the product, and cooling at the temperature of minus 20 ℃ for 8 hours to separate out crystals, namely p-phenylenediamine.
In particular, the aluminum chloride in this embodiment may also be aluminum sulfate, iron sulfate, zinc sulfate, aluminum nitrate, iron acetate, or copper acetate.
FIG. 1 is a nuclear magnetic resonance carbon spectrum of a recovered terephthalic acid monomer; FIG. 2 is the NMR spectrum of the recovered p-phenylenediamine monomer. It can be seen from FIGS. 1 and 2 that the terephthalic acid and the p-phenylenediamine recovered are high in purity and almost have no impurity peak. The method can effectively realize the chemical degradation of the waste para-aramid and recover the monomers terephthalic acid and p-phenylenediamine with higher added value.
Claims (10)
1. A method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid is characterized by comprising the following steps: the method comprises the following steps:
Step 1: mixing a soluble metal salt catalyst and a reaction solvent to prepare a reaction system I, mixing the para-aramid fiber and the reaction system I, adding the mixture into a reaction kettle, sealing the reaction kettle, and then putting the reaction kettle into a homogeneous reactor for heating reaction; cooling to room temperature after the reaction is finished, adding deionized water for washing, and filtering to remove the catalyst and the reaction solvent, wherein the reaction products are terephthalic acid and p-phenylenediamine acyl derivatives; adding a strong base aqueous solution, dissolving the generated salt of the terephthalic acid, and filtering and separating to obtain a p-phenylenediamine acyl derivative and a terephthalic acid salt solution; adding hydrochloric acid into the terephthalate solution to precipitate terephthalic acid, washing, filtering and drying to obtain terephthalic acid;
step 2: preparing a reaction system II from strong base and a reaction solvent, mixing the p-phenylenediamine acyl derivative prepared in the step 1 and the reaction system II, adding the mixture into a reaction kettle, sealing the reaction kettle, and then putting the reaction kettle into a homogeneous reactor for heating reaction; and cooling to room temperature after the reaction is finished, evaporating the organic solvent to remove the organic solvent, adding deionized water into the product, cooling, and separating out crystals, namely p-phenylenediamine.
2. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the soluble metal salt catalyst in the step 1 is any one of aluminum chloride, ferric chloride, copper chloride, zinc chloride, aluminum sulfate, ferric sulfate, copper sulfate, zinc sulfate, aluminum nitrate, ferric nitrate, cupric nitrate, zinc nitrate, aluminum acetate, ferric acetate, cupric acetate or zinc acetate.
3. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the reaction solvent in the step 1 is an organic carboxylic acid solvent, and comprises formic acid, acetic acid or propionic acid.
4. the method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the mass fraction of the soluble metal salt catalyst in the reaction solvent in the reaction system I in the step 1 is 1-50%; the mass ratio of the para-aramid fiber to the reaction system I in the step 1 is 1: 1-100.
5. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the heating reaction temperature in the step 1 is 100-280 ℃, and the reaction time is 1-72 hours.
6. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the concentration of the strong alkali aqueous solution in the step 1 is 1-20%, and the strong alkali is potassium hydroxide, sodium hydroxide or lithium hydroxide.
7. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the strong base in the step 2 is potassium hydroxide, sodium hydroxide or lithium hydroxide.
8. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the reaction solvent in the step 2 is an alcohol solvent, and comprises methanol, ethanol, n-propanol or isopropanol.
9. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: in the reaction system II in the step 2, the mass fraction of the strong base in the reaction solvent is 1-50%; the mass ratio of the p-phenylenediamine acyl derivative in the step 2 to the reaction system II is 1: 1-100.
10. The method for preparing terephthalic acid and p-phenylenediamine by degrading p-aramid according to claim 1, wherein the method comprises the following steps: the heating reaction temperature in the step 2 is 100-280 ℃, and the reaction time is 1-72 hours; the cooling temperature in the step 2 is-20-0 ℃, and the cooling time is 1-24 hours.
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