A method for recycling rectification still residue

Abstract

A method for resource utilization of distillation vessel residue. A method for preparing pentanamine is provided, the method comprising the following steps: (1) adding water to the distillation vessel residue obtained in the process of preparing caprolactam by the gas-phase Beckmann rearrangement of cyclohexanone oxime, and heating to dissolve to obtain a homogeneous solution; (2) under a hydrogen atmosphere, introducing the homogeneous solution obtained in step (1) into a fixed-bed reactor filled with catalyst to react and obtain pentanamine.

Description

Technical Field

[0001] This application relates to the field of petrochemical technology, specifically to a method for the resource utilization of distillation kettle residues in the preparation of caprolactam via gas-phase rearrangement. Background Technology

[0002] Caprolactam is an important organic chemical raw material, mainly used in the production of nylon 6 engineering plastics and nylon 6 fibers. Currently, 90% of the industrial production processes for caprolactam involve the cyclohexanone oxime Beckmann rearrangement. There are two main Beckmann rearrangement processes for preparing caprolactam from cyclohexanone oxime: liquid-phase Beckmann rearrangement and gas-phase Beckmann rearrangement. Compared to gas-phase rearrangement, liquid-phase rearrangement has several drawbacks: firstly, it consumes high-value liquid ammonia and produces a large amount of low-value ammonium sulfate as a byproduct; secondly, it causes equipment corrosion and environmental pollution. Gas-phase rearrangement uses high-silica molecular sieves or solid acids as catalysts, does not produce ammonium sulfate as a byproduct, and solves the problems of equipment corrosion and environmental pollution associated with traditional processes, making it a green and environmentally friendly new process.

[0003] However, due to the high temperature of the gas-phase Beckmann rearrangement reaction, many side reactions (such as alcoholysis and polymerization) often occur, generating a wide variety of byproducts. As a monomer for synthetic fibers and engineering plastics, caprolactam requires very strict quality control in organic chemical production. Therefore, caprolactam obtained from the cyclohexanone oxime gas-phase rearrangement needs further purification. During the deweighting and distillation purification processes, caprolactam often contains some caprolactam oligomers in the reactor, ultimately forming solid waste residue that pollutes the environment and reduces production efficiency. To improve the economics of the gas-phase rearrangement reaction, further resource utilization and recovery of caprolactam from the deweighting and distillation reactor residues are particularly important.

[0004] Traditional methods for treating distillation vessel residue include incineration or environmental biochemical treatment. Incineration produces not only large amounts of CO2 but also large amounts of NO. X This increases the load and emission concentration of the incinerator's exhaust gas, and polycaprolactam also easily forms sticky residues in the incinerator, making the treatment of distillation kettle residue more difficult. While environmentally friendly biochemical treatment is possible, the high cost is due to the presence of many recalcitrant and non-biodegradable organic impurities.

[0005] Chinese Patent CN 106146374 B discloses a method for recovering and utilizing the heavy residue from the fractionation of cyclohexanone oxime vapor-phase rearrangement products. This method involves dissolving the heavy residue in a solvent, followed by crystallization and distillation to obtain caprolactam. However, this process only extracts caprolactam from the heavy residue, without treating the caprolactam oligomers. Therefore, the caprolactam recovery rate is low, and the use of organic solvents inevitably increases wastewater discharge.

[0006] CN114516838A discloses a method for resource utilization of distillation vessel residue, which obtains caprolactam products through hydrolysis. This method can effectively degrade caprolactam oligomers in distillation vessel residue, thereby improving the recovery rate of caprolactam.

[0007] Pentylamine is an important chemical raw material widely used in antioxidants, emulsifiers, pesticides, rubber chemicals, flotation agents, and in the synthesis of high-value pharmaceuticals, offering significant economic benefits. Currently, the pentylamine production process is predominantly carried out industrially using the pentylonitrile method. This method requires hydrogenation reduction under high-pressure hydrogen conditions to produce pentylamine, but the product contains approximately 30% dipentylamine and tripentylamine, which need to be removed by distillation to obtain higher-purity pentylamine. The aforementioned pentylamine preparation process requires high-pressure reaction conditions, which is detrimental to safe production, and also results in low yields, high production costs, and the generation of significant amounts of the byproducts dipentylamine and tripentylamine.

[0008] Therefore, there is still a need in the field for a new method for the resource utilization of distillation vessel residues in the preparation of caprolactam by gas-phase rearrangement, which can directly form pentanamine with high yield and low cost. Summary of the Invention

[0009] The purpose of this invention is to provide a method for the resource utilization of distillation vessel residue in the preparation of caprolactam by gas-phase rearrangement, which can directly form pentanamine with high yield and low cost.

[0010] The inventors of this application have discovered through extensive research that the distillation vessel residue obtained during the preparation of caprolactam from cyclohexanone oxime via the Beckmann rearrangement in the gas phase can be hydrolyzed and decarboxylated with hydrogen to directly form pentamidine.

[0011] This application provides a method for preparing pentanylamine, the method comprising the following steps:

[0012] (1) Water was added to the distillation vessel residue obtained during the preparation of caprolactam from the vapor-phase Beckmann rearrangement of cyclohexanone oxime, and the solution was heated to dissolve it and obtain a homogeneous solution.

[0013] (2) Under a hydrogen atmosphere, the homogeneous solution obtained in step (1) is fed into a fixed-bed reactor filled with catalyst to react and obtain pentanamine.

[0014] Another aspect of this application provides a pentamidine product prepared by the method of this application. Attached Figure Description

[0015] Figure 1 Gas chromatograms of the pentanamine obtained in Examples 7-10 are described.

[0016] Figure 2 Gas chromatograms of the pentanamine obtained in Examples 11-22 are described.

[0017] Figure 3 Gas chromatograms of the pentanylamine obtained in Examples 23-32 are described. Detailed Implementation

[0018] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0019] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0020] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0021] In this application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0022] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0023] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0024] In this description, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0025] Unless otherwise specified, percentages (%) or parts refer to weight percentages or parts relative to the composition.

[0026] Unless otherwise stated herein, the sum of the contents of the components in the composition is 100%.

[0027] Unless otherwise stated herein, the sum of the parts of each component in the composition may be 100 parts by weight.

[0028] In this document, unless otherwise stated, “combination of” means a multi-component mixture of the elements, such as two, three, four, and up to the maximum possible multi-component mixture.

[0029] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0030] In this paper, unless otherwise stated, all reactions were carried out at room temperature and pressure.

[0031] This application provides a method for preparing pentanylamine, the method comprising the following steps:

[0032] (1) Water was added to the distillation vessel residue obtained during the preparation of caprolactam from the vapor-phase Beckmann rearrangement of cyclohexanone oxime, and the solution was heated to dissolve it and obtain a homogeneous solution.

[0033] (2) Under a hydrogen atmosphere, the homogeneous solution obtained in step (1) is fed into a fixed-bed reactor filled with catalyst to react and obtain pentanamine.

[0034] In this application, the term "distillation kettle residue obtained during the preparation of caprolactam from cyclohexanone oxime via the Beckmann rearrangement" refers to a residue generated during the preparation of caprolactam from cyclohexanone oxime via the Beckmann rearrangement. Specifically, it refers to the residue formed at the bottom of the distillation kettle during the deweighting and distillation treatment of the crude caprolactam product obtained from the cyclohexanone oxime via the Beckmann rearrangement. Therefore, in this application, "distillation kettle residue obtained during the preparation of caprolactam from cyclohexanone oxime via the Beckmann rearrangement" and "distillation kettle residue" have the same meaning, both originating from the process of preparing caprolactam from cyclohexanone oxime via the Beckmann rearrangement. For example, the "distillation kettle residue" in this application comes from Yangnong Group.

[0035] In step (1) of the method of this application, the water can be water commonly used in the art, including but not limited to deionized water and distilled water.

[0036] In step (1) of the method of this application, the weight ratio of the distillation vessel residue to water can be 1:0.1-5, for example 1:0.3-5. In order to better hydrolyze the caprolactam oligomers in the distillation vessel residue, the weight ratio of the distillation vessel residue to water is preferably less than or equal to 1:1, for example 1:1-5, more preferably 1:1-3, and even more preferably 1:1-2.

[0037] In step (1) of the method of this application, the heating temperature can be 30-150°C, for example 40-120°C, preferably 50-90°C, and more preferably 60-80°C.

[0038] In step (1) of the method of this application, the heating and dissolving time can be 0.5-24h, for example 1-20h, preferably 1-10h, and most preferably 4-8h.

[0039] In step (1) of the method of this application, the heating and dissolution can be carried out under the application of physical action to accelerate the hydrolysis of caprolactam oligomers. The physical action includes, but is not limited to, stirring, sonication, oscillation, or a combination thereof.

[0040] Typically, step (1) of the method in this application forms a homogeneous solution, mainly because caprolactam oligomers hydrolyze under heating conditions to form aminocaproic acid. Therefore, the main component in the homogeneous solution is aminocaproic acid, which is the hydrolysis product of caprolactam.

[0041] In step (1) of the method of this application, the homogeneous solution refers to a uniform solution containing no visible solid impurities. In one embodiment of this application, solid impurities in the homogeneous solution may be further removed by filtration.

[0042] In step (2) of the method of this application, the catalyst may be one or more combinations of modified β molecular sieve, modified Y-type molecular sieve or modified ZSM-5 molecular sieve.

[0043] In one example of this application, the modified molecular sieve (e.g., modified β-zeolite, modified Y-type molecular sieve, or modified ZSM-5 molecular sieve) is a molecular sieve catalyst (e.g., β-zeolite, Y-type molecular sieve, or ZSM-5 molecular sieve) supported on one or more metals selected from Mn, Sc, Ni, Fe, Zn, Pt, Pd, Rh, Mo, Ti, Cr, Co, Cu, Ga, V, and Ru). To obtain a higher pentylamine yield, the metal is preferably Ni, Mo, or a combination thereof, more preferably a combination of Ni and Mo.

[0044] In step (2) of the method of this application, the hydrogen atmosphere refers to the introduction of hydrogen into a fixed-bed reactor filled with catalyst. The hydrogen may be commercially available hydrogen or hydrogen produced as a byproduct of petrochemical processes.

[0045] In step (2) of the method of this application, the mass hourly space velocity (MSV) of the homogeneous solution added to the fixed-bed reactor can be 0.01-1 h based on the weight of the residue in the distillation vessel. -1 For example, 0.01-0.5h -1 To obtain a better yield of pentylamine, the preferred mass hourly space velocity (MHSV) is 0.05-0.1 h⁻¹. -1 .

[0046] In step (2) of the method of this application, the reaction temperature in the fixed bed reactor can be 200-900℃, for example 300-800℃, preferably 400-600℃.

[0047] In step (2) of the method of this application, the pressure in the fixed bed reactor can be 0.01-5 MPa, for example 0.05-3 MPa, preferably 0.1-2 MPa, and more preferably 0.3-0.8 MPa.

[0048] In step (2) of the method of this application, the mass ratio of hydrogen to homogeneous solution can be 0.01-1:1, for example 0.01-0.5:1, preferably 0.01-0.2:1. In order to obtain a better pentylamine yield, the mass ratio of hydrogen to homogeneous solution is preferably 0.02-0.1:1.

[0049] Compared with the prior art, the present invention has the following advantages:

[0050] (1) Caprolactam residue in a distillation vessel is converted into pentanamine in one step by a high-temperature hydrolysis decarboxylation process. The process is simple, the conversion efficiency is high, and it is easy to industrialize.

[0051] (2) Convert the low-value caprolactam distillation vessel residue into high-purity, high-value pentylamine to further reduce costs and improve economic benefits.

[0052] (3) The process used realizes the resource utilization of caprolactam distillation kettle residue, reduces the amount of traditional incineration and landfill processes, reduces resource waste and environmental pollution, and conforms to the principles of green chemistry process.

[0053] The following embodiments illustrate the invention in more detail, but are not intended to further limit the invention. Unless otherwise stated, "%" refers to "mass %".

[0054] Table 1 shows the dissolution ratio of oligomers remaining in the distillation vessel (R). d The ratio of the mass of oligomers dissolved in deionized water to the initial mass of residue in the distillation vessel is calculated using the following formula:

[0055]

[0056] Where m 初 m is the initial mass of the distillation vessel residue before dissolution. 剩 This represents the remaining mass of the reactor residue after dissolution.

[0057] Table 2-4 shows the total yield Y of the target product pentylamine. 戊胺 The ratio of the mass of the target product pentylamine obtained from post-processing distillation to the mass of the initial feed residue in the distillation vessel is calculated using the following formula:

[0058]

[0059] Where m 戊胺 To determine the mass of the target product, pentamidine, obtained by post-processing distillation, m 初 This refers to the mass of the residue in the distillation vessel after the initial feed.

[0060] Examples 1-6:

[0061] 100g of distillation vessel residue (Yangnong Group) and different weights of deionized water were added to the reaction vessel. After stirring and dissolving for different time periods under different conditions, the solution was filtered through filter paper to obtain a homogeneous solution. The number average molecular weight of the oligomer polycaprolactam in the homogeneous solution was determined to be between 237 and 1409 by liquid chromatography-mass spectrometry (LCMS). The specific dissolution ratio of oligomers from the distillation vessel residue in the obtained homogeneous solution is shown in Table 1.

[0062] Table 1. Dissolution ratio of oligomer residue in distillation vessel

[0063]

[0064] Examples 7-10:

[0065] 20g of Ni / Mo / ZSM-5 molecular sieve purchased from Nankai Catalyst Factory was loaded into a fixed-bed reactor with a bed length of 50cm and a bed diameter of 0.6cm. The homogeneous solution obtained in Example 5 was then introduced at a mass hourly space velocity (MSW) of 0.1h.-1 The solution was introduced into a fixed-bed reactor, and hydrogen gas at a different mass ratio than that of the homogeneous solution was introduced into the fixed-bed reactor for reaction. The fixed-bed reaction temperature was 500℃, and the reaction pressure was 0.5 MPa. The total yield of pentylamine obtained after distillation of the reaction solution is shown in Table 2. The gas chromatogram of pentylamine is shown in... Figure 1 .

[0066] Table 2

[0067] hydrogen to homogeneous solution mass ratio Total yield of pentamidine / % Example 7 0.01:1 65.34 Example 8 0.02:1 78.62 Example 9 0.1:1 79.89 Example 10 0.2:1 63.37

[0068] Examples 11-22:

[0069] Maintaining a hydrogen-to-homogeneous solution mass ratio of 0.1, 20g of different catalysts were loaded into a fixed-bed reactor with a bed length of 50cm and a bed diameter of 0.6cm. The homogeneous solution obtained in Example 5 was introduced into the fixed-bed reactor at a mass hourly space velocity (MHSV) of 0.1h⁻¹. The fixed-bed reaction temperature was 500℃, and the reaction pressure was 0.5MPa. The total yield of pentylamine obtained by post-distillation of the reaction solution is shown in Table 3. The gas chromatogram of pentylamine is shown in... Figure 2 .

[0070] Table 3. Total Yield of Pentylamine under Different Catalyst Types

[0071] Sample Name Catalyst type Total yield of pentamidine / % Example 11 Ni / ZSM-5 molecular sieve 77.34 Example 12 Ni / Mo / ZSM-5 molecular sieve 80.62 Example 13 Ni / Ru / ZSM-5 molecular sieve 75.89 Example 14 Ni / Rh / Pt / ZSM-5 molecular sieve 78.37 Example 15 Cr / β molecular sieve 75.36 Example 16 Cr / Rh / β molecular sieve 77.96 Example 17 Cr / Pd / β molecular sieve 78.36 Example 18 Cr / Ru / Pt / β molecular sieve 71.15 Example 19 Fe / Y molecular sieve 75.65 Example 20 Fe / Ru / Y molecular sieve 77.16 Example 21 Fe / Pd / Y molecular sieve 75.64 Example 22 Fe / Rh / Pt / Y molecular sieves 73.37

[0072] Examples 23-32:

[0073] Maintaining a hydrogen-to-homogeneous solution mass ratio of 0.1, 20 g of Ni / Mo / ZSM-5 molecular sieve catalyst was loaded into a tubular fixed-bed reactor with a bed length of 50 cm and a bed diameter of 0.6 cm. The homogeneous solution obtained in Example 5 was introduced into the fixed-bed reactor at different mass hourly space velocities (MHSVs) and reacted at different temperatures and pressures. The total yield of pentylamine obtained after distillation of the reaction solution is detailed in Table 4. The gas chromatogram of pentylamine is shown in [Figure 4]. Figure 3 .

[0074] Table 4. Total Yield of Pentylamine under Different Reaction Conditions

[0075]

[0076]

[0077] Comparative Example 1:

[0078] This comparative example provides a method for the resource utilization of residues in the preparation of caprolactam by gas-phase rearrangement. The difference between this method and Example 8 is that no hydrogen is introduced into the fixed-bed system, and the total yield of pentylamine is 49.56%.

[0079] The content described in this invention is not limited to the embodiments described herein.

[0080] This article uses specific examples to illustrate the structure and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the core idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing pentanylamine, the method comprising the following steps: (1) Water was added to the distillation vessel residue obtained during the preparation of caprolactam from cyclohexanone oxime by the Beckmann rearrangement in the gas phase, and the mixture was heated to dissolve it and obtain a homogeneous solution; (2) Under a hydrogen atmosphere, the homogeneous solution obtained in step (1) is fed into a fixed-bed reactor filled with catalyst to react and obtain pentanamine. The catalyst is one or more combinations of modified β-zeolites, modified Y-type zeolites, or modified ZSM-5 zeolites supported on one or more metals selected from Mn, Sc, Ni, Fe, Zn, Pt, Pd, Rh, Mo, Ti, Cr, Co, Cu, Ga, V, and Ru.

2. The method as described in claim 1, wherein, The weight ratio of the distillation vessel residue to water is 1:0.1-5.

3. The method as described in claim 1, wherein, The weight ratio of the distillation vessel residue to water is 1:0.3-5.

4. The method of claim 1, wherein, The heating temperature is 30-150℃.

5. The method of claim 1, wherein, The heating temperature is 40-120℃.

6. The method of claim 1, wherein, The heating temperature is 50-90℃.

7. The method of claim 1, wherein, The heating temperature is 60-80℃.

8. The method of claim 1, wherein, The metal is Ni, Mo, or a combination thereof.

9. The method of claim 1, wherein, The metal is a combination of Ni and Mo.

10. The method of claim 1, wherein, The hydrogen atmosphere refers to the introduction of hydrogen into a fixed-bed reactor filled with catalyst.

11. The method of claim 1, wherein, Based on the weight of the residue in the distillation vessel, the mass hourly space velocity (MSV) of the homogeneous solution added to the fixed-bed reactor is 0.01-1 h⁻¹. -1 .

12. The method of claim 1, wherein, Based on the weight of the residue in the distillation vessel, the mass hourly space velocity (MSV) of the homogeneous solution added to the fixed-bed reactor is 0.01-0.5 h⁻¹. -1 .

13. The method of claim 1, wherein, Based on the weight of the residue in the distillation vessel, the mass hourly space velocity (MSV) is 0.05-0.1 h⁻¹. -1 .

14. The method of claim 1, wherein, The reaction temperature in the fixed-bed reactor is 200-900℃.

15. The method of claim 1, wherein, The reaction temperature in the fixed-bed reactor is 300-800℃.

16. The method of claim 1, wherein, The reaction temperature in the fixed-bed reactor is 400-600℃.

17. The method of claim 1, wherein, The pressure in the fixed-bed reactor is 0.01-5 MPa.

18. The method of claim 1, wherein, The pressure in the fixed-bed reactor is 0.05-3 MPa.

19. The method of claim 1, wherein, The pressure in the fixed-bed reactor is 0.1-2 MPa.

20. The method of claim 1, wherein, The pressure in the fixed-bed reactor is 0.3-0.8 MPa.

21. The method of claim 1, wherein, The mass ratio of hydrogen gas to homogeneous solution is 0.01-1:

1.

22. The method of claim 1, wherein, The mass ratio of hydrogen to homogeneous solution is 0.01-0.5:

1.

23. The method of claim 1, wherein, The mass ratio of hydrogen gas to homogeneous solution is 0.01-0.2:

1.

24. The method of claim 1, wherein, The mass ratio of hydrogen to homogeneous solution is 0.02-0.1:1.

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