Clean production method of bio-based valerolactam

Abstract

The invention discloses a clean production method of bio-based valerolactam. The monomer valerolactam is prepared by taking bio-based cyclopentanone as a raw material through two-step reaction of ammoximation and Beckmann rearrangement. The method mainly comprises the following steps: 1) mixing raw materials, namely cyclopentanone, ammonia water and hydrogen peroxide, and reacting under the action of a catalyst to generate cyclopentanone oxime; 2) recycling the catalyst through solid-liquid separation, and distilling a reaction liquid phase to obtain a high-purity intermediate product cyclopentanone oxime; 3) gasifying the cyclopentanone oxime, feeding the gasified cyclopentanone oxime into a rearrangement reactor filled with an all-silicon molecular sieve, and carrying out catalytic rearrangement reaction on the cyclopentanone oxime to generate valerolactam; and 4) carrying out heat exchange condensation and rectification purification on the gas-phase material flow from the rearrangement reactor to obtain the polymer-grade valerolactam monomer. The method is high in conversion rate in each step, high in selectivity and good in atom economy, valerolactam is prepared from cyclopentanone in a high-selectivity manner, ammonium sulfate as a byproduct is avoided, meanwhile, no waste acid or waste salt is generated, and the method is a clean industrial production method of the valerolactam monomer.

Description

Technical Field

[0001] The invention relates to the field of new chemical materials, and in particular to a method for producing valerolactam by using bio-based cyclopentanone as a starting material through ammoximation and Beckmann rearrangement reactions. Background Art

[0002] Valerolactam is a widely used chemical product. It can be prepared from cyclopentanone through ammoximation, Beckmann rearrangement and other processes. It is one of the important organic chemical raw materials. It can be polymerized and further processed to produce plastics, fibers and films, and has great application potential in the production of synthetic fibers and plastics. Cyclopentanone oxime is an important intermediate for the synthesis of valerolactam, which has a very wide range of applications in scientific research, medical care and even daily life.

[0003] Caprolactam is currently produced on a large scale in industry, and relevant reports have been published on this technology. CN101429148A introduces a method for producing caprolactam, which uses a strip molecular sieve with an MFI structure as a catalyst and a cyclohexanone oxime alcohol solution to perform a gas-phase Beckmann rearrangement reaction under a nitrogen atmosphere. The strip MFI structure catalyst used in this method has a fast deactivation rate at high space velocity and is prone to carbon deposition, which affects the reaction.

[0004] CN102875468A introduces a method for producing caprolactam by gas phase rearrangement of cyclohexanone oxime, wherein cyclohexanone oxime is mixed with a high temperature solvent and a carrier gas and gasified and passed into a rearrangement reactor equipped with a solid acid catalyst to react and produce caprolactam, thereby reducing the generation of three wastes. The method focuses on how to recover caprolactam from the crude caprolactam product, and does not mention the specific preparation method of cyclohexanone oxime and the catalyst. CN113831271A introduces a method for preparing caprolactam by catalyzing gas phase rearrangement of cyclohexanone oxime, comprising using SCM-14 molecular sieve as a catalyst, dissolving cyclohexanone oxime in a low-carbon alcohol solvent, and synthesizing caprolactam through gas phase rearrangement reaction. The method has the characteristics of high caprolactam selectivity at a lower reaction temperature and a higher space velocity, but is not as good as the all-silicon molecular sieve prepared in CN103896839A.

[0005] Similar to caprolactam, there are related reports on the relevant technology of producing cyclopentanone oxime by ammoximation. CN116924935A provides a method for preparing cyclopentanone oxime, which is to carry out ammoximation reaction of cyclopentanone, gaseous ammonia and hydrogen peroxide under the action of titanium silicon molecular sieve, filter while hot, obtain cyclopentanone oxime aqueous solution, and then cool and crystallize to obtain cyclopentanone oxime product. This method does not add additional solvent, and the poor mixing effect of reactants will lead to poor overall fluidity, short service life of catalyst, and waste of resources, which is difficult to further large-scale industrial application. CN113956177A discloses a method for preparing cyclopentanone oxime, which is to contact cyclopentanone, hydrogen peroxide, ammonia water and catalyst in methanol solvent, and react under the condition of pH 5 to 7. The reaction conditions are mild, but it is easy to cause low conversion rate of cyclopentanone, thus leading to waste of resources.

[0006] Similar to the preparation process of caprolactam, the Beckmann rearrangement reaction with cyclopentanone oxime as raw material is a key step in producing valerolactam monomer. CN113943239A discloses a method and system for preparing valerolactam. The method is similar to the production process of caprolactam. Cyclopentanone oxime is first obtained by ammoximation reaction, and then oleum is used as a catalyst to contact the cyclopentanone oxime solution to carry out a liquid phase Beckmann rearrangement reaction to obtain valerolactam. However, the oleum used in the method is toxic and corrosive, and the byproduct ammonium sulfate has low economic value and is easy to pollute the environment. CN116003303A provides a method for synthesizing valerolactam. Cyclohexanone, a reaction aid, is added to the cyclopentanone ammoximation reaction to improve the extraction and separation effect of the extractant on valerolactam and wastewater. Cyclohexane is used as the extractant and it is found that the conversion rate of cyclopentanone oxime and the selectivity of valerolactam can be improved. However, the method obtains a mixture of caprolactam and valerolactam, and the later separation and refining process is cumbersome and inevitably produces ammonium sulfate as a by-product, and the oleum used is toxic and corrosive. CN116969857A discloses a method for preparing valerolactam by refining and purifying a cyclopentanone oxime crude liquid and gas phase rearrangement. The method is to extract the cyclopentanone oxime crude liquid with methylcyclohexane, cool the extracted organic phase, precipitate the cyclopentanone oxime solid, and perform Beckmann rearrangement reaction on the cyclopentanone oxime solid to obtain valerolactam. The method avoids using oleum or concentrated sulfuric acid as a catalyst, but the overall rearrangement reaction has a low selectivity for valerolactam. Therefore, it is crucial to develop a green, simple and efficient valerolactam preparation technology suitable for industrial large-scale production. Summary of the invention

[0007] In view of the problems existing in the existing valerolactam preparation methods, the present invention aims to provide a green and clean method for preparing valerolactam with high conversion rate and high selectivity. Compared with the existing process, the method has the characteristics of easy reaction control, less by-products produced by the reaction, high cyclopentanone oxime conversion rate, high valerolactam selectivity, and no waste acid or waste salt generated.

[0008] In order to achieve the above object, the present invention provides a method for producing valerolactam by using bio-based cyclopentanone as a starting material through ammoximation and Beckmann rearrangement reaction, the method comprising:

[0009] (1) fully mixing the raw materials cyclopentanone, ammonia water, hydrogen peroxide, a catalyst and a solvent A, and causing the cyclopentanone to undergo an ammoximation reaction under the action of the catalyst to generate a cyclopentanone oxime reaction solution;

[0010] (2) separating the catalyst from the cyclopentanone oxime reaction liquid through solid-liquid separation, and distilling the liquid phase to obtain the intermediate product cyclopentanone oxime;

[0011] (3) After cyclopentanone oxime is mixed with solvent B and dissolved and vaporized, it is sent into a rearrangement reactor equipped with an all-silicon molecular sieve via a carrier gas, and cyclopentanone oxime undergoes a catalytic rearrangement reaction to generate valerolactam.

[0012] In step (1), the reaction solvent A can make the reactants highly soluble in each other, strengthen the mass transfer process of the reactants, reduce the corrosion of ammonia water on the molecular sieve, inhibit the dissolution, loss and deactivation of the catalyst, and extend the service life of the catalyst.

[0013] In step (1), the reaction solvent A is one of methanol, ethanol, isopropanol and tert-butanol.

[0014] In step (1), the molar ratio of cyclopentanone, hydrogen peroxide, ammonia water and solvent A is 1: (0.5-2): (1-3): (2-20), preferably 1: (0.5-1.5): (1-2.5): (2-15).

[0015] In step (1), the catalyst is a molecular sieve selected from at least one of ZSM-5, MCM-22, SiO2, TS-1, TS-2, Ti-MOR and Ti-MWW, and the mass ratio of cyclopentanone to catalyst is 5 to 20:1, preferably 10 to 20:1.

[0016] In step (1), the ammoximation reaction conditions are: normal pressure, reaction temperature of 50-90° C., reaction time of 60-360 min, preferably reaction temperature of 50-80° C., reaction time of 80-360 min.

[0017] In step (2), the liquid phase distillation operation is used to recover the reaction solvent; the extraction operation is used to separate the aqueous phase and the organic phase; and the crystallization operation is used to obtain high-purity cyclopentanone oxime.

[0018] In step (3), the solvent B is an organic solvent, preferably one of methanol, ethanol, isopropanol or tert-butanol; the molar ratio of cyclopentanone oxime to solvent B is 1:(1.5-25).

[0019] In step (3), the all-silicon molecular sieve is formed by molding an aluminum-free MFI structure molecular sieve, and then contacting it with an alkaline buffer solution. The aluminum-free MFI structure molecular sieve is a catalyst with a diameter of 0.01 to 1 mm obtained by mixing water and / or a binder in a mass ratio of 1:0.01 to 100, and then drying and calcining. The alkaline buffer solution contains ammonium salt and alkali, the content of ammonium salt is 0.5 to 20% by weight, the content of alkali is 5 to 30% by weight, and the pH value of the alkaline buffer solution is 8.5 to 13.5.

[0020] In step (3), the vaporization temperature is 100-250° C.; the carrier gas is nitrogen, and the nitrogen flow rate is 50-800 mL / min.

[0021] In step (3), the gas phase rearrangement reaction conditions are: normal pressure, reaction temperature 200-550°C, preferably normal pressure, reaction temperature 240-500°C.

[0022] In the present invention, the condensation and distillation operations are used to obtain high-purity valerolactam.

[0023] In the present invention, the gas phase stream from the rearrangement reactor is separated and purified to obtain a polymerization-grade valerolactam monomer;

[0024] The separation and purification process includes condensation, distillation or crystallization operations to obtain high-purity valerolactam.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The reaction system of the invention has high conversion rate in each step, high selectivity and good atom economy, and can prepare valerolactam from cyclopentanone with high selectivity, avoiding the by-production of ammonium sulfate and also without the generation of waste acid and waste salt. The invention is a clean industrial production method for valerolactam monomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0028] Figure 1 This is the process flow chart for clean production of valerolactam. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the following examples, unless otherwise specified, the reagents and raw materials used are all commercially available products.

[0031] In the following examples, the concentration of aqueous ammonia is 25-28 wt %, and the concentration of hydrogen peroxide is 30 wt %.

[0032] Example 1

[0033] A clean production method for valerolactam comprises the following steps:

[0034] (1) Ammoximation reaction unit: 0.06 mol of cyclopentanone, methanol, 0.5 g of titanium silicalite TS-1 (MFI type, pore size 0.56-0.58 nm) and ammonia water are added to a reactor for mixing, wherein the ratio of cyclopentanone to solvent methanol is 1 mol / L, and the molar ratio of ammonia water to cyclopentanone is 3:1. After heating to 70°C, a mixture of hydrogen peroxide and methanol is added dropwise into the reactor at a rate of 0.1 mL / min using a continuous feed pump. The volume ratio of hydrogen peroxide to methanol in the mixture is 1:1.5, and the molar ratio of hydrogen peroxide to cyclopentanone is 1:1. The reaction is carried out for 6 hours.

[0035] (2) Cyclopentanone oxime separation and purification unit: The catalyst is recovered by filtration, the solvent methanol in the solution after the ammoximation reaction is recovered by distillation, and the organic phase in the solution is extracted with toluene, and then cyclopentanone oxime is separated by distillation at 150°C.

[0036] (3) Gas-phase Beckmann rearrangement reaction unit: treat the all-silicon molecular sieve with an alkaline buffer solution containing 20 wt% ammonium chloride and 10 wt% ammonia water; mix and dissolve the cyclopentanone oxime obtained in step (2) with ethanol in a molar ratio of 1:4, and after gasification, enter the rearrangement reactor containing the treated all-silicon molecular sieve, and the reaction conditions are: reactor temperature 300°C, feed rate 5mL / min, nitrogen flow rate 100mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0037] Example 2

[0038] A clean production method for valerolactam comprises the following steps:

[0039] (1) Ammoximation reaction unit: 0.06 mol of cyclopentanone, ethanol, 0.5 g of titanium silicalite TS-2 (MEL type topology, pore size 0.54 nm) and ammonia water are added to a reactor for mixing, wherein the ratio of cyclopentanone to solvent ethanol is 3 mol / L, and the molar ratio of ammonia water to cyclopentanone is 2:1. After heating to 80°C, a mixture of hydrogen peroxide and ethanol is added dropwise into the reactor at a rate of 0.5 mL / min using a continuous feed pump. The volume ratio of hydrogen peroxide to ethanol in the mixture is 1:2, and the molar ratio of hydrogen peroxide to cyclopentanone is 1.2:1. The reaction is carried out for 4 hours.

[0040] (2) Cyclopentanone oxime separation and purification unit: The catalyst is recovered by filtration, the solvent ethanol in the solution after the ammoximation reaction is recovered by distillation, and the organic phase in the solution is extracted with toluene, and then cyclopentanone oxime is separated by distillation at 150°C.

[0041] (3) Gas-phase Beckmann rearrangement reaction unit: treat the all-silicon molecular sieve with an alkaline buffer solution containing 20 wt% ammonium chloride and 10 wt% ammonia water; mix and dissolve the cyclopentanone oxime obtained in step (2) with ethanol in a molar ratio of 1:6, and after gasification, enter the rearrangement reactor containing the alkali-treated all-silicon molecular sieve, and the reaction conditions are: reactor temperature 350°C, feed rate 10mL / min, nitrogen flow rate 150mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0042] Example 3

[0043] A clean production method for valerolactam comprises the following steps:

[0044] (1) Ammoximation reaction unit: 0.06 mol of cyclopentanone, tert-butanol, 0.6 g of molecular sieve SiO2 and ammonia water are added to a reactor and mixed, wherein the ratio of cyclopentanone to solvent tert-butanol is 3.5 mol / L, and the molar ratio of ammonia water to cyclopentanone is 1.5:1. After heating to 60°C, a mixture of hydrogen peroxide and tert-butanol is added dropwise into the reactor at a rate of 1 mL / min using a continuous feed pump. The volume ratio of hydrogen peroxide to tert-butanol in the mixture is 1:2.5, and the molar ratio of hydrogen peroxide to cyclopentanone is 1.4:1. The reaction is continued for 2 h.

[0045] (2) Cyclopentanone oxime separation and purification unit: The catalyst is recovered by filtration, the solvent tert-butyl alcohol in the solution after the ammoximation reaction is recovered by distillation, and the organic phase in the solution is extracted with toluene, and then cyclopentanone oxime is separated by distillation at 150°C.

[0046] (3) Gas-phase Beckmann rearrangement reaction unit: treat the all-silicon molecular sieve with an alkaline buffer solution containing 20 wt% ammonium chloride and 10 wt% ammonia water; mix and dissolve the cyclopentanone oxime obtained in step (2) with ethanol in a molar ratio of 1:8, and after gasification, enter the rearrangement reactor containing the alkali-treated all-silicon molecular sieve, and the reaction conditions are: reactor temperature 400°C, feed rate 15 mL / min, nitrogen flow rate 200 mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0047] Example 4

[0048] A clean production method for valerolactam comprises the following steps:

[0049] (1) Ammoximation reaction unit: 0.06 mol cyclopentanone, isopropanol, 0.7 g molecular sieve ZSM-5 (silicon-aluminum ratio: 70, pore size 0.53-0.58 nm) and ammonia water are added to a reactor for mixing, wherein the ratio of cyclopentanone to solvent isopropanol is 2.5 mol / L, and the molar ratio of ammonia water to cyclopentanone is 1:1. After heating to 80°C, a mixture of hydrogen peroxide and isopropanol is added dropwise into the reactor at a rate of 0.4 mL / min using a continuous feed pump, wherein the volume ratio of hydrogen peroxide to isopropanol is 1:3, and the molar ratio of hydrogen peroxide to cyclopentanone is 1.3:1, and the reaction is carried out for 1 hour.

[0050] (2) Cyclopentanone oxime separation and purification unit: The catalyst is recovered by filtration, the organic solvent A in the solution after the ammoximation reaction is recovered by distillation, and the organic phase in the solution is extracted with toluene, and then cyclopentanone oxime is separated by distillation at 150°C.

[0051] (3) Gas-phase Beckmann rearrangement reaction unit: treat the all-silicon molecular sieve with an alkaline buffer solution containing 20 wt% ammonium chloride and 10 wt% ammonia water; mix and dissolve the cyclopentanone oxime obtained in step (2) with ethanol in a molar ratio of 1:10, and after gasification, enter the rearrangement reactor containing the alkali-treated all-silicon molecular sieve, and the reaction conditions are: reactor temperature 450°C, feed rate 20mL / min, nitrogen flow rate 300mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0052] Example 5

[0053] The operation was carried out according to the method of Example 1, except that hydrogen peroxide was added to the reactor once in the ammoximation reaction according to the method described in Example 1. The reaction results obtained by GC detection are shown in Table 1.

[0054] Example 6

[0055] The operation was carried out according to the method of Example 1, except that the solvent of the ammoximation reaction was changed from methanol to tert-butyl alcohol according to the method described in Example 1. The reaction results obtained by GC detection are shown in Table 1.

[0056] Example 7

[0057] The operation was carried out according to the method of Example 1, except that the ammoximation reaction temperature was adjusted to 80° C. according to the method described in Example 1. The reaction results obtained by GC detection are shown in Table 1.

[0058] Example 8

[0059] The operation was carried out according to the method of Example 1, except that the ammoximation reaction time was shortened to 4 hours according to the method described in Example 1. The reaction results obtained by GC detection are shown in Table 1.

[0060] Example 9

[0061] The operation was carried out according to the method of Example 1, except that the rearrangement unit reaction conditions were changed to: feed rate 10 mL / min, nitrogen flow rate 200 mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0062] Example 10

[0063] The operation was carried out according to the method of Example 1, except that the rearrangement unit reaction conditions were changed to: reaction temperature 400°C, feed rate 10 mL / min, nitrogen flow rate 200 mL / min. The reaction results obtained by GC detection are shown in Table 1.

[0064] Embodiment 11

[0065] The operation was carried out according to the method of Example 1, except that the reaction solvent B of the gas phase Beckmann rearrangement unit was changed from ethanol to methanol according to the method described in Example 1. The reaction results obtained by GC detection are shown in Table 1.

[0066] Table 1 (1) Ammoximation reaction

[0067]

[0068] (2) Gas-phase Beckmann rearrangement reaction

[0069]

[0070]

[0071] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A clean production method for valerolactam, characterized in that: The following steps are involved: (1) fully mixing the raw materials cyclopentanone, ammonia water, hydrogen peroxide, a catalyst and a solvent A, and causing the cyclopentanone to undergo an ammoximation reaction under the action of the catalyst to generate a cyclopentanone oxime reaction solution; (2) separating the catalyst from the cyclopentanone oxime reaction liquid by solid-liquid separation, and distilling the liquid phase to obtain the intermediate product cyclopentanone oxime; (3) After cyclopentanone oxime is mixed with solvent B and dissolved and vaporized, it is sent into a rearrangement reactor equipped with an all-silicon molecular sieve via a carrier gas, and cyclopentanone oxime undergoes a catalytic rearrangement reaction to generate valerolactam.

2. The clean production method according to claim 1, characterized in that: The solvent A is one of methanol, ethanol, isopropanol and tert-butanol; the molar ratio of cyclopentanone, hydrogen peroxide, ammonia water and solvent A is 1: (0.5-2): (1-3): (2-20), preferably 1: (0.5-1.5): (1-2.5): (2-15).

3. The clean production method according to claim 1, characterized in that: The catalyst in step (1) is a molecular sieve, selected from at least one of ZSM-5, MCM-22, SiO2, TS-1, TS-2, Ti-MOR and Ti-MWW, preferably TS-1 or TS-2; the mass ratio of cyclopentanone to catalyst is 5 to 20:1, preferably 10 to 20:

1.

4. The clean production method according to claim 1, characterized in that: The conditions for the ammoximation reaction in step (1) are: reaction temperature of 50-90° C., reaction time of 60-360 min, preferably reaction temperature of 50-80° C., reaction time of 80-360 min.

5. The clean production method according to claim 1, characterized in that: In step (1), cyclopentanone, a catalyst, aqueous ammonia and solvent A are first mixed, and then a mixture of hydrogen peroxide and solvent A is added dropwise to carry out a reaction.

6. The clean production method according to claim 1, characterized in that: The solvent B in step (3) is an organic solvent, preferably one of methanol, ethanol, isopropanol or tert-butanol; the molar ratio of cyclopentanone oxime to solvent B is 1:(1.5-25).

7. The clean production method according to claim 1, characterized in that: The all-silicon molecular sieve in step (3) is obtained by molding an aluminum-free MFI structure molecular sieve and then contacting it with an alkaline buffer solution; The aluminum-free MFI molecular sieve is a catalyst having a diameter of 0.01 to 1 mm obtained by mixing water and / or a binder in a mass ratio of 1:0.01 to 100, drying, calcining and forming. The alkaline buffer solution contains ammonium salt and alkali, the content of the ammonium salt is 0.5-20% by weight, the content of the alkali is 5-30% by weight, and the pH value of the alkaline buffer solution is 8.5-13.

5.

8. The clean production method according to claim 1, characterized in that: In step (3), the vaporization temperature is 100-250° C., and the feed rate is 2-25 mL / min; the carrier gas is nitrogen, and the nitrogen flow rate is 50-800 mL / min.

9. The clean production method according to claim 1, characterized in that: The gas phase rearrangement reaction conditions in step (3) are: reaction temperature 200-550°C, preferably reaction temperature 240-500°C.

10. The clean production method according to claim 1, characterized in that: The gas phase stream from the rearrangement reactor is separated and purified to obtain a polymerization-grade valerolactam monomer; The separation and purification process includes condensation, distillation or crystallization operations.

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