MOF-type adsorbents, their preparation methods, and applications

Abstract

This invention relates to the field of hexamethylenediamine purification, and discloses a MOF-type adsorbent, its preparation method, and its application. The method includes: reacting an acidified MOF material, a functional monomer, and a crosslinking agent in the presence of a catalyst, a monoamine, and a first dispersant, followed by the removal of the monoamine. The MOF-type adsorbent prepared by this invention has a large specific surface area and specific adsorption sites for monoamines, enabling selective adsorption of trace amounts of monoamines in crude hexamethylenediamine products with high adsorption capacity. This allows for further purification of the hexamethylenediamine obtained from distillation, achieving a purity level comparable to that required for the polymerization of nylon 66.

Description

Technical Field

[0001] This invention relates to the field of hexamethylenediamine purification, specifically to a MOF-type adsorbent, its preparation method, and its application. Background Technology

[0002] Hexamethylenediamine (HDME) is one of the three major raw materials for nylon. It is a colorless, transparent crystal at room temperature and is a strongly alkaline organic compound. Its main use is in the production of nylon 66 and nylon 610, and with the addition of functional additives, it is used to produce engineering plastics, military-grade and civilian-grade fibers. This type of product has strong tensile strength and weather resistance, and has extremely wide applications in the machinery and electrical fields. It can replace traditional metal materials in the manufacture of mechanical parts and load-bearing components.

[0003] As a key intermediate in the production of Nylon 66, the purity and types of impurities of hexamethylenediamine (HDMA) significantly impact the product quality. The HDMA produced by the ammoniation process using hexanediamine as a raw material requires precise analysis of its purity and impurities. The purity requirement for HDMA is >99.7%. Monoamine compounds formed during the ammoniation of hexanediamine, such as hexylamine and cyclohexylamine, can easily cause chain breakage in high-molecular-weight nylon fibers during the polymerization of HDMA into Nylon 6 and Nylon 66. These are strictly controlled toxic compounds in HDMA products.

[0004] Currently, the monoamine impurities that may be present in 1,6-hexanediamine prepared by the 1,6-hexanediamine amination process are mainly 1-hexylamine and cyclohexylamine. These impurities easily cause chain breakage in high-molecular-weight nylon fibers during the hexanediamine polymerization reaction and are strictly controlled toxic compounds in hexanediamine products. CN113441118A discloses a method for removing 3,4,5,6-tetrahydro-2H-azaphenes from hexanediamine, but it cannot specifically remove 1-hexylamine and cyclohexylamine. Therefore, a mild method for removing the monoamines 1-hexylamine and cyclohexylamine from hexanediamine is urgently needed to meet the needs of downstream nylon 66 production. Summary of the Invention

[0005] In view of the above situation, the present invention provides a MOF type adsorbent, its preparation method and application. The MOF type adsorbent can specifically adsorb 1-hexylamine and cyclohexylamine in crude hexamethylenediamine, which solves the problem that the trace monoamines in crude hexamethylenediamine are difficult to remove and affect the production of nylon 66.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a MOF-type adsorbent, the method comprising: reacting an acidified MOF material, a functional monomer, and a crosslinking agent in the presence of a catalyst, a monoamine, and a first dispersant, and then performing an operation to remove the monoamine.

[0007] A second aspect of the present invention provides a MOF-type adsorbent prepared by the method described above;

[0008] Alternatively, MOF type adsorbents with a specific surface area of ​​500-1200 m² 2 / g, with a particle size in the range of 0.2-5μm.

[0009] A third aspect of the present invention provides a method for removing monoamine impurities from crude hexamethylenediamine, the method comprising: contacting the above-described MOF-type adsorbent with crude hexamethylenediamine;

[0010] Alternatively, prepare the MOF-type adsorbent according to the above method, and then contact the MOF-type adsorbent with crude hexamethylenediamine.

[0011] When crude hexamethylenediamine is treated directly using MOF materials as adsorbents, the contents of hexamethylenediamine, hexylamine, and cyclohexylamine remain almost unchanged before and after treatment, indicating that there are almost no specific adsorption sites for hexylamine and cyclohexylamine on the MOF materials. However, the MOF-type adsorbent prepared using this invention has a large specific surface area and specific adsorption sites for monoamines (hexylamine and cyclohexylamine), enabling selective adsorption of trace amounts of monoamines in the crude hexamethylenediamine product. Furthermore, it has a high adsorption capacity (i.e., requires less adsorbent), allowing for further purification of the hexamethylenediamine obtained from distillation, achieving the purity required for the polymerization of nylon 66.

[0012] The preparation method of the MOF-type adsorbent of this invention is simple, and the prepared MOF-type adsorbent can be recycled, thus reducing production costs. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the MOF-type adsorbent in Example 1. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] The first aspect of the present invention provides a method for preparing a MOF-type adsorbent, the method comprising: reacting an acidified MOF material, a functional monomer and a crosslinking agent in the presence of a catalyst, a monoamine and a first dispersant, and then performing an operation to remove the monoamine.

[0016] According to the present invention, the catalyst can be a monoprotic strong acid catalyst commonly used in the art, preferably, the catalyst is concentrated hydrochloric acid; preferably, the mass fraction of concentrated hydrochloric acid is greater than 20%, more preferably 30-40%.

[0017] According to the present invention, preferably, the amount of catalyst used is 0.1-2 mL per gram of functional monomer, more preferably 0.15-0.5 mL.

[0018] According to the present invention, preferably, the monoamine is hexylamine and / or cyclohexylamine.

[0019] According to the present invention, the type of the first dispersant can be selected from a wide range, but in order to uniformly disperse the template monoamine and the functional monomer, the first dispersant is preferably a C1-C4 monohydric alcohol and / or acetonitrile, more preferably at least one of methanol, ethanol, acetonitrile, propanol and isopropanol, and more preferably methanol and / or ethanol. In the present invention, "C1-C4" refers to substances with 1-4 carbon atoms.

[0020] According to the present invention, preferably, the amount of the first dispersant is 10-100 mL, more preferably 30-50 mL, relative to each gram of monoamine.

[0021] According to the present invention, preferably, the amount of acidified MOF material used is 5-12g, more preferably 7-9g, relative to each gram of monoamine.

[0022] According to the present invention, the functional monomer can be a commonly used functional monomer in adsorbent preparation. Considering the reactivity of the functional monomer with the MOF material and the effect of the coating film formed on the MOF material surface on removing monoamine impurities from crude hexamethylenediamine, preferably, the functional monomer is selected from (3-aminopropyl)triethoxysilane and / or (3-mercaptopropyl)triethoxysilane. This preferred embodiment not only effectively removes monoamines from crude hexamethylenediamine but also further reduces the amount of adsorbent used, thereby reducing production costs.

[0023] According to the present invention, preferably, the molar ratio of monoamine to functional monomer is 1:1-10, more preferably 1:3-5.

[0024] According to the present invention, the crosslinking agent is any substance capable of undergoing a polycondensation reaction with the functional monomer, but considering the coating performance of the film formed by the reaction of the crosslinking agent and the functional monomer on the MOF material, the crosslinking agent is preferably selected from tetramethoxysilane and / or tetraethoxysilane.

[0025] According to the present invention, preferably, the molar ratio of functional monomer to crosslinking agent is 1:1-10, more preferably 1:2-4.

[0026] According to the present invention, preferably, the reaction conditions include: a temperature of 15-40°C and a time of 0.5-5 h, preferably 1-2 h.

[0027] The present invention may further include cleaning the reaction product (solid product) of the acidified MOF material, functional monomer and crosslinking agent (3-5 times) with a cleaning agent, wherein the cleaning agent includes at least one of methanol, ethanol, propanol, isopropanol and acetonitrile, preferably methanol and / or ethanol.

[0028] According to the present invention, preferably, the process of removing the monoamine includes washing the reaction product with a mixture of acid and alcohol. The volume ratio of acid to alcohol in the acid-alcohol mixture can be 1:5-20, preferably 1:8-12. The acid in the acid-alcohol mixture can be formic acid and / or acetic acid, and the alcohol in the acid-alcohol mixture can be methanol and / or ethanol.

[0029] According to the present invention, there is no particular limitation on the number of times the reaction product is washed with a mixture of acid and alcohol, which can be determined according to the actual situation. Preferably, the number of times the reaction product is washed with a mixture of acid and alcohol is sufficient to ensure that no monoamine molecules are detected in the washing solution.

[0030] According to the present invention, preferably, the method further includes washing the product after the removal of the monoamine with a cleaning agent, wherein the cleaning agent is at least one selected from methanol, ethanol, acetonitrile, propanol and isopropanol, preferably methanol and / or ethanol.

[0031] According to the present invention, preferably, the method further includes drying the washed product; more preferably, the drying is carried out under vacuum. The vacuum drying conditions can be those commonly used in the art. The drying temperature is 30-90°C, the pressure is 0-150 Pa, and the time is 0.5-10 h.

[0032] According to the present invention, in order to increase the amount of carboxyl functional groups exposed on the MOF material, preferably, the acidified MOF material is obtained by treating the MOF material with an organic acid in the presence of a second dispersant.

[0033] According to the present invention, preferably, the second dispersant is selected from benzene compounds, more preferably at least one of toluene, benzene, ethylbenzene and xylene, and more preferably toluene.

[0034] According to the present invention, preferably, the amount of the second dispersant is 10-30 mL, more preferably 15-25 mL, relative to each gram of MOF material.

[0035] According to the present invention, the MOF material can be a conventional commercially available MOF material. Preferably, the MOF material is selected from at least one of repeating network MOFs (e.g., IRMOFs), zeolite imidazolium ester framework MOFs (e.g., ZIFs), Levasil framework materials (e.g., MILs), and pore-channel framework materials (e.g., PCNs). More preferably, the MOF material is selected from at least one of MIL-101 material, UIO-66 material, and PCN-250 material.

[0036] In this invention, in order to better coat the surface of the acidified MOF material with the film formed by the functional monomer and the crosslinking agent, the specific surface area of ​​the MOF material is preferably 500-4000 m². 2 / g, preferably 1000-3000m 2 / g. More preferably, the pore volume of the MOF material is 0.5-3 cm³. 3 / g. More preferably, the particle size of the MOF material is in the range of 0.2-5μm.

[0037] According to the present invention, preferably, the organic acid treatment conditions include a temperature of 60-120°C and a time of 5-24 hours.

[0038] According to the present invention, taking into account the structural properties of MOF materials and the amount of carboxyl functional groups exposed on MOF materials, preferably, the amount of organic acid used is 0.5-2g, more preferably 0.8-1.2g, relative to each gram of MOF material.

[0039] According to the present invention, preferably, the organic acid is selected from at least one of formic acid, acetic acid and propionic acid, more preferably formic acid.

[0040] The present invention may also include cleaning the reaction product (solid product) of MOF material with acid (3-5 times) with a cleaning agent, wherein the cleaning agent includes at least one of methanol, ethanol, propanol, isopropanol and acetonitrile, preferably methanol and / or ethanol.

[0041] A second aspect of the present invention provides a MOF-type adsorbent prepared by the method described above;

[0042] Alternatively, the specific surface area of ​​MOF-type adsorbents is 500-1200 m². 2 / g, preferably greater than 800m 2 / g, with a particle size in the range of 0.2-5μm.

[0043] A third aspect of the present invention provides a method for removing monoamine impurities from crude hexamethylenediamine, the method comprising: contacting the above-described MOF-type adsorbent with crude hexamethylenediamine;

[0044] Alternatively, prepare the MOF-type adsorbent according to the above method, and then contact the MOF-type adsorbent with crude hexamethylenediamine.

[0045] In this invention, it is understood that the crude hexamethylenediamine is the hexamethylenediamine before it is treated by the method of this invention, that is, the hexamethylenediamine before purification.

[0046] According to the present invention, the source of crude hexamethylenediamine is not particularly limited. Preferably, the crude hexamethylenediamine is hexamethylenediamine after distillation. More preferably, the content of hexamethylenediamine in the crude hexamethylenediamine is >99.5 wt%, the content of hexylamine in the crude hexamethylenediamine is <0.5 wt%, and the content of cyclohexylamine in the crude hexamethylenediamine is <0.5 wt%.

[0047] According to the present invention, preferably, the contact conditions include a temperature of 40-60°C and a time of 10-30 hours.

[0048] In this invention, the method for removing monoamine impurities from crude hexamethylenediamine can employ any adsorption method known to those skilled in the art, such as batch adsorption, fixed bed adsorption, tower adsorption, or moving bed adsorption.

[0049] According to the present invention, preferably, the mass ratio of MOF type adsorbent to crude hexamethylenediamine is 1:300-1000.

[0050] In this invention, the method for removing monoamine impurities from crude hexamethylenediamine further includes regenerating the molecularly imprinted material after contact with the crude hexamethylenediamine. The regeneration process can be performed using any method well-known to those skilled in the art suitable for adsorbent regeneration; preferably, the regeneration method includes any one of solvent washing, Soxhlet extraction, gas purging, solid-phase extraction, and supercritical fluid extraction.

[0051] The present invention will be described in detail below through embodiments. In the following embodiments,

[0052] The room temperature is approximately 25°C.

[0053] Example 1

[0054] (1) Weigh 10g of MIL-101(Cr) material (BET specific surface area 1500m²) 2 / g, pore volume 2.0-2.4cm 3 (g, particle size 500-800nm) was added to a reaction vessel, followed by 200mL of toluene. After stirring until homogeneous, 10g of formic acid was added, and the mixture was refluxed at 85℃ for 12h. After the reaction was completed, the mixture was cooled and filtered. The resulting solid was washed three times with methanol and dried under vacuum (pressure <150Pa) at 50℃ for 2h to obtain the acidified MIL-101 material.

[0055] (2) 0.5 g hexylamine, 0.5 g cyclohexylamine, and 8.8 g (3-aminopropyl)triethoxysilane were added to 40 mL of ethanol and stirred at room temperature. 8 g of acidified MIL-101 material was added and mixed. Then, 24 g tetraethoxysilane and 2.1 mL of concentrated hydrochloric acid (37 wt%) were added, and the mixture was stirred at room temperature for 1 h. After the reaction was complete, unreacted raw materials were washed away with ethanol. Then, the mixture was washed with a 1:9 mixture of methanol and formic acid until no template molecules were detected. The MIL-101 adsorbent was obtained by vacuum drying.

[0056] Scanning electron microscope image of the adsorbent is shown below. Figure 1 As shown in the figure, the material has a uniform morphology, and the particles have distinct angular shapes. The morphology of the prepared adsorbent is consistent with that of the MOF material of MIL-101(Cr). The specific surface area of ​​the MIL-101 adsorbent, as determined by BET analysis, is 893 m². 2 / g.

[0057] Example 2

[0058] (1) Weigh 10g of UIO-66(Zr) material (specific surface area of ​​1000m²). 2 / g, pore volume 0.8cm 3 (g, particle size approximately 0.7 μm) was added to a reaction vessel, followed by 250 mL of toluene. After stirring until homogeneous, 9 g of acetic acid was added, and the mixture was refluxed at 80 °C for 10 h. After the reaction was complete, the mixture was cooled and filtered. The resulting solid was washed three times with methanol and dried under vacuum (pressure <150 Pa) at 50 °C for 2 h to obtain the acidified UIO-66 material.

[0059] (2) 0.5 g hexylamine, 0.5 g cyclohexylamine, and 7.5 g (3-aminopropyl)triethoxysilane were added to 40 mL of ethanol and stirred at room temperature. 9 g of acidified UIO-66 was added and mixed. Then, 20 g of tetramethoxysilane and 2 mL of concentrated hydrochloric acid (37 wt%) were added, and the mixture was stirred at room temperature for 1 h. After the reaction was complete, unreacted raw materials were washed away with ethanol. Then, the mixture was washed with a 1:9 volume ratio of ethanol and acetic acid until no template molecules were detected. The UIO-66 adsorbent was obtained by vacuum drying.

[0060] Example 3

[0061] (1) Weigh 9g of PCN-250(Fe) material (specific surface area of ​​1200m²). 2 / g, pore volume 0.85cm 3 / g (particle size approximately 0.6μm) was added to a reaction vessel, followed by 200mL of ethylbenzene. After stirring until homogeneous, 10g of acetic acid was added, and the mixture was refluxed at 85℃ for 12h. After the reaction was completed, the mixture was cooled and filtered. The resulting solid was washed three times with ethanol and dried under vacuum (pressure <150Pa) at 50℃ for 2h to obtain the acidified PCN-250 material.

[0062] (2) 0.5 g hexylamine, 0.5 g cyclohexylamine, and 9 g (3-mercaptopropyl)triethoxysilane were added to 40 mL of ethanol and stirred at room temperature. 10 g of acidified PCN-250 was added and mixed. Then, 20 g of tetramethoxysilane and 3 mL of concentrated hydrochloric acid (37 wt%) were added, and the mixture was stirred at room temperature for 1 h. After the reaction was complete, unreacted raw materials were washed away with ethanol. Then, the mixture was washed with a 1:10 mixture of methanol and formic acid until no template molecules were detected. The PCN-250 adsorbent was obtained by vacuum drying.

[0063] Example 4

[0064] The procedure was carried out according to Example 1, except that formic acid was replaced with an equimolar amount of benzoic acid.

[0065] Example 5

[0066] The procedure was carried out according to Example 1, except that (3-aminopropyl)triethoxysilane was replaced with an equal weight of tetraethoxysilane.

[0067] Example 6

[0068] The procedure was carried out according to Example 1, except that the amount of (3-aminopropyl)triethoxysilane used was 2g.

[0069] Comparative Example 1

[0070] The procedure was carried out according to the method of Example 1, except that hexylamine and cyclohexylamine were not added in step (2).

[0071] Test case

[0072] The adsorbents prepared in the above examples and comparative examples were used to purify crude hexamethylenediamine (the crude hexamethylenediamine was distilled hexamethylenediamine with a content of 99.85 wt% hexamethylenediamine, 0.06 wt% hexylamine, and 0.05 wt% cyclohexylamine). The purification method included adding 0.1 kg of adsorbent to a certain amount of crude hexamethylenediamine, stirring and adsorbing at 50°C for 20 h, and then filtering to separate the adsorbent. The filtrate was the purified hexamethylenediamine. The purity of the purified hexamethylenediamine and the contents of hexylamine and cyclohexylamine in the purified hexamethylenediamine were tested by gas chromatography. The results are shown in Table 1.

[0073] Recovery rate of hexamethylenediamine = (Mass of purified hexamethylenediamine ÷ Mass of hexamethylenediamine before purification) × 100%

[0074] Table 1

[0075]

[0076] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method of preparing a MOF type adsorbent, characterized in that, The method includes: reacting an acidified MOF material, a functional monomer, and a crosslinking agent in the presence of a catalyst, a monoamine, and a first dispersant, followed by a process of removing the monoamine; The catalyst is concentrated hydrochloric acid; The monoamine is hexylamine and / or cyclohexylamine; Method for obtaining acidified MOF materials: In the presence of a second dispersant, MOF materials are treated with organic acids to obtain acidified MOF materials; The functional monomer is selected from (3-aminopropyl)triethoxysilane and / or (3-mercaptopropyl)triethoxysilane; The crosslinking agent is selected from tetramethoxysilane and / or tetraethoxysilane.

2. The method of claim 1, wherein, The amount of catalyst used is 0.1-2 mL per gram of functional monomer; And / or, the first dispersant is a C1-C4 monohydric alcohol and / or acetonitrile; And / or, the amount of the first dispersant is 10-100 mL relative to each gram of monoamine.

3. The method of claim 1, wherein, The mass fraction of concentrated hydrochloric acid is greater than 20%. And / or, the first dispersant is at least one of methanol, ethanol, acetonitrile, propanol and isopropanol; And / or, the amount of the first dispersant is 30-50 mL relative to each gram of monoamine.

4. The method of claim 1, wherein, The mass fraction of concentrated hydrochloric acid is 30-40%. And / or, the first dispersant is methanol and / or ethanol.

5. The method of claim 1, wherein, The amount of acidified MOF material used is 5-12g per gram of monoamine.

6. The method of claim 5, wherein, The amount of acidified MOF material used is 7-9g per gram of monoamine.

7. The method of claim 1, wherein, The molar ratio of monoamine to functional monomer is 1:1-10.

8. The method of claim 7, wherein, The molar ratio of monoamine to functional monomer is 1:3-5.

9. The method of claim 1, wherein, The molar ratio of functional monomer to crosslinking agent is 1:1-10; And / or, the reaction conditions include: a temperature of 15-40℃ and a time of 0.5-5h.

10. The method of claim 9, wherein, The molar ratio of functional monomer to crosslinking agent is 1:2-4; And / or, the reaction conditions include: a temperature of 15-40℃ and a time of 1-2h.

11. The method of claim 1, wherein, The process of removing monoamines includes washing the reaction products with a mixture of acid and alcohol.

12. The method of claim 1, wherein, The second dispersant is selected from benzene series compounds; And / or, the amount of the second dispersant is 10-30 mL relative to each gram of MOF material; And / or, the MOF material is selected from at least one of repeating network MOF, zeolite imidazolium ester framework MOF, Levasil framework material and pore-channel framework material; And / or, the conditions for organic acid treatment include a temperature of 60-120°C and a time of 5-24 hours; And / or, the amount of organic acid treatment is 0.5-2g per gram of MOF material; And / or, the organic acid is selected from at least one of formic acid, acetic acid and propionic acid.

13. The method of claim 12, wherein, The second dispersant is at least one of toluene, benzene, ethylbenzene, and xylene; And / or, the amount of the second dispersant is 15-25 mL relative to each gram of MOF material; And / or, the amount of organic acid treatment is 0.8-1.2 g per gram of MOF material; And / or, the organic acid is formic acid.

14. The method of claim 12, wherein, The second dispersant is toluene.

15. The MOF-type adsorbent prepared by the method according to any one of claims 1-14.

16. The MOF-type adsorbent of claim 15, wherein, MOF-type adsorbents have a specific surface area of 500-1200 m 2 / g, with a particle size in the range of 0.2-5 μm.

17. A process for removing monoamine impurities from a crude hexamethylenediamine, characterized by, The method includes contacting the MOF-type adsorbent of claim 15 or 16 with crude hexamethylenediamine.

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