Method for continuously synthesizing tetrahydropyrrole and catalyst used in method

Abstract

The invention discloses a method for continuously synthesizing tetrahydropyrrole and a catalyst used in the method. According to the continuous synthesis method disclosed by the invention, by adjusting reaction conditions (reaction temperature, air speed, pressure, ammonia gas proportion and the like), the product can reach a very high yield, and meanwhile, a reaction crude product obtained by the reaction is easy to separate. Compared with a metal ion modified molecular sieve in the prior art, the catalyst adopted in the method can use a single hydrogen type molecular sieve which is simpler in composition, tetrahydropyrrole is synthesized in a high yield in a continuous reaction, the cost is lower, and the production efficiency is higher.

Description

Technical Field

[0001] The present application relates to the field of chemical synthesis, and in particular, to a method for continuously synthesizing pyrrolidine and a catalyst used in this method. Background Art

[0002] Pyrrolidine, CAS No.: 123-75-1, also known as pyrrolidine, has a special odor, is a transparent liquid, turns yellow when exposed to light or humid air, has a boiling point of 89.5 ± 8.0 °C, and a relative density of 0.8 ± 0.1 g / cm 3 , refractive index 1.428, flash point 2.8 °C.

[0003] Pyrrolidine is an important organic synthesis raw material, soluble in water and ethanol, corrosive and flammable, and has the properties and reactions of general amines. It is mainly used for preparing some drugs, fungicides, insecticides, etc., and has extremely wide applications in the fields of medicine, food, pesticides, daily chemicals, coatings, textiles, printing and dyeing, papermaking, photosensitive materials, polymer materials, desulfurizing agents, zeolite template substances, etc.

[0004] Currently, there are many industrial preparation methods for pyrrolidine, which can be roughly divided into gas-phase catalytic synthesis method, hydrogenation method and electrolytic reduction method. The gas-phase catalytic method can be further divided into gas-phase catalytic synthesis method using butanediol and ammonia as raw materials, gas-phase catalytic synthesis method using amino alcohol as raw material, gas-phase catalytic synthesis method using 1,4-diaminobutane as raw material, gas-phase catalytic synthesis method using tetrahydrofuran and ammonia as raw materials, and gas-phase catalytic cyclization method using ethylenediamine as raw material, etc. The hydrogenation method can be further divided into cyclization catalytic hydrogenation method using succinonitrile as raw material, gas-phase catalytic hydrogenation method using pyrrolidone as raw material, and gas-phase catalytic hydrogenation method using pyrrole as raw material. The electrolytic method mainly includes electrolytic reduction method using pyrrole as raw material, etc. The synthesis of pyrrolidine from tetrahydrofuran and ammonia is environmentally friendly. However, due to the large gap in the performance level of domestic catalysts compared with foreign ones in the early stage, the product quality is poor and it is difficult to achieve large-scale production. Yu Xu et al. (Yu Xu. Research on the Gas-Phase Catalytic Synthesis of Pyrrolidine from Tetrahydrofuran and Ammonia [D]. Hangzhou: Zhejiang University, 2003.) synthesized a new type of catalyst. Using tetrahydrofuran and ammonia as raw materials, pyrrolidine was synthesized under the conditions of HZSM-5 catalyst with a silica-alumina ratio of 70, a reaction temperature of 240 °C, and a gas-solid contact time of 60 g / h·mol. The conversion rate of tetrahydrofuran was close to 100%, and the yield of pyrrolidine was about 60%. Using butanediol and ammonia as raw materials, Kulkani et al. (Kulkarni S J, Raghavan K V, Vippagunta R R, et al. Process for the synthesis of an alinphatecyclic amine: US6528647 [P]. 2003-03-04.) focused on investigating the catalytic performance of molecular sieves modified by metal ions. Yarlagadda et al. (Yarlagadda V, Subba R. Shivanand J, et al. Modified ZSM-5catalysts for the synthesis of five-and six-membered het-erocyclics [J]. JOrgChem, 1994, 59: 3998-4000.) used a single ZSM-5 as the catalyst, and the yield of pyrrolidine was only 48%. When preparing pyrrolidine from butanediol and ammonia, using molecular sieves modified by metal ions has a series of problems such as high cost, cumbersome production methods and difficulty in obtaining, and using a single molecular sieve has a low yield, making it difficult to achieve continuous production with high yield. Summary of the Invention

[0005] Technical problem

[0006] In view of the problems existing in the above-mentioned prior art, the present application provides a catalyst for continuously synthesizing pyrrolidine and a method for synthesizing pyrrolidine using the same. The catalyst is a hydrogen-type molecular sieve catalyst modified after ion exchange, with low preparation cost. At the same time, a continuous reactor is adopted, which can realize continuous production with low cost, high yield and high efficiency.

[0007] Technical solution

[0008] According to one aspect of the present invention, an object of the present invention is to provide a method for continuously synthesizing pyrrolidine, comprising the following steps:

[0009] (1) Adding a catalyst into a continuous reactor and heating to the reaction temperature under a nitrogen atmosphere to activate the catalyst;

[0010] (2) After the temperature is stabilized, introducing the raw material and the ammonia source into the continuous reactor for reaction;

[0011] (3) After the reaction is completed, the crude reaction product enters the storage tank after condensation and gas-liquid separation;

[0012] (4) The crude reaction product treated in step (3) is rectified to obtain a product with qualified purity.

[0013] Preferably, the continuous reactor is selected from any one of a continuous stirred tank reactor, a plug flow reactor, a fixed bed reactor and a fluidized bed reactor, or a mixed reactor formed by connecting two or more of these reactors, and preferably a fixed bed reactor or a fluidized bed reactor.

[0014] Preferably, the reaction temperature in step (1) ranges from 250 to 400 °C;

[0015] Preferably, the raw material in step (2) is selected from 1,4-butanediol and tetrahydrofuran;

[0016] Preferably, the ammonia source in step (2) is selected from ammonia gas and ammonia water;

[0017] Preferably, the space velocity of the raw material in step (2) is 0.05 - 50 h -1 ;

[0018] Preferably, the molar ratio of the raw material to the ammonia source in step (2) is 1:2 - 1:100;

[0019] Preferably, the reaction pressure in step (2) is from atmospheric pressure to 2 MPa;

[0020] In step (4), the rectification conditions are atmospheric rectification, with 35 - 40 theoretical plates, a bottom temperature of 95 - 105 °C, a distillate head temperature of 65 - 75 °C, and reflux: withdrawal = 1:1 to 10:1;

[0021] The catalyst is selected from one or more hydrogen - type molecular sieve catalysts of Na - ZSM - 5, Na - Y, Na - β, Na - ZSM - 11, Na - MOR that have undergone ion - exchange treatment, preferably one or more hydrogen - type molecular sieve catalysts of Na - ZSM - 5, Na - Y, Na - β.

[0022] Preferably, the hydrogen - type molecular sieve catalyst is prepared by the following method:

[0023] Mix and stir an ion - exchange solution with a mass ratio of 1:1 to 100:1 and molecular sieve powder of 200 - 240 mesh. After exchanging for a certain time at a certain temperature, perform suction filtration, drying, and calcination. After repeating the above ion - exchange treatment on the obtained dry powder at least 1 more time, use a hydraulic powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the ion - exchanged hydrogen - type molecular sieve catalyst.

[0024] Preferably, the pore diameter range of the molecular sieve powder is 2.5 - 4.0 nm.

[0025] Preferably, the specific surface area of the hydrogen - type molecular sieve catalyst is 330 - 430 m 2 ·g -1 , the total pore volume is 0.33 - 0.36 mL·g -1 , and the pore diameter is 3.2 - 4.8 nm.

[0026] Preferably, the ion - exchange solution is one of 1 mol / L NH4Cl solution, 1 mol / L NH4NO3 solution, and 0.2 mol / L HCl solution.

[0027] Preferably, the mass ratio of the ion - exchange solution used to the molecular sieve powder is 1:1 to 50:1, more preferably 5:1 to 20:1, and even more preferably 10:1.

[0028] Preferably, the molecular sieve powder is one or more of Na - ZSM - 5, Na - Y, Na - β, Na - ZSM - 11, Na - MOR molecular sieve powders, preferably one or more of Na - ZSM - 5, Na - Y, Na - β molecular sieve powders.

[0029] Preferably, the ion - exchange temperature is 50 - 120 °C, preferably 80 - 100 °C.

[0030] Preferably, the ion - exchange time is 2 - 48 h, preferably 12 - 36 h.

[0031] Beneficial effects

[0032] The continuous synthesis method of the present invention can achieve a very high yield of the product by adjusting the reaction conditions (reaction temperature, space velocity, pressure, ammonia ratio, etc.). At the same time, the crude reaction product obtained by the reaction is easy to separate. The catalyst used in the present invention can use a single hydrogen-type molecular sieve with a simpler composition than the molecular sieve modified by metal ions in the prior art, realizing a higher yield in the continuous reaction to synthesize pyrrolidine, with lower cost, higher production efficiency, and being more simple. Specific embodiments

[0033] Hereinafter, the present invention will be described in detail. Before the description, it should be understood that the terms used in this specification and the appended claims should not be construed as limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that allows the inventor to appropriately define the terms for the best explanation. Therefore, the description presented here is only a preferred example for illustrative purposes and is not intended to limit the scope of the present invention. Thus, it should be understood that other equivalent means or improved means can be obtained without departing from the spirit and scope of the present invention.

[0034] The following examples are only listed as examples of the implementation schemes of the present invention and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope not deviating from the essence and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0035] In this article, the terms "comprising", "including", "having", "containing" or any other similar terms are all open-ended connectives, which are intended to cover non-exclusive inclusions. For example, a composition or article containing plural elements is not limited only to these elements listed herein, but may also include other elements that are not explicitly listed but are usually inherent in the composition or article. In addition, unless there is a clear contrary statement, the term "or" refers to the inclusive "or" rather than the exclusive "or". For example, any of the following situations satisfies the condition "A or B": 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), A and B are both true (or exist). In addition, in this article, the interpretations of the terms "comprising", "including", "having", "containing" should be regarded as having been specifically disclosed and simultaneously covering closed or semi-closed connectives such as "consisting of..." and "substantially consisting of...".

[0036] In this text, all features or conditions defined in the form of numerical ranges or percentage ranges are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual values within the range, especially integer values. For example, the description of the range "1 to 8" should be regarded as having specifically disclosed all sub-ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., especially the sub-ranges defined by all integer values, and should be regarded as having specifically disclosed individual values such as 1, 2, 3, 4, 5, 6, 7, 8, etc. within the range. Unless otherwise specified, the foregoing interpretation method applies to all contents of the present invention throughout the text, regardless of the scope being broad or narrow.

[0037] If a quantity or other numerical value or parameter is expressed in the form of a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges formed by any pair of the upper limit or preferred value of the range and the lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are separately disclosed or not. In addition, when a numerical range is mentioned in this text, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0038] In this text, on the premise that the purpose of the invention can be achieved, a numerical value should be understood as having the accuracy of the significant digits of that numerical value. For example, the number 40.0 should be understood as covering the range from 39.50 to 40.49.

[0039] In the method for continuously synthesizing methacrylonitrile according to the present invention, the product is obtained using 1,4-butanediol and ammonia as raw materials. The product is analyzed and detected by gas chromatography (GC). Qualitative analysis of low-boiling products is carried out by gas chromatography-mass spectrometry (GC-MS) and comparison of the GC retention time with that of a standard substance to determine that the raw material participating in the reaction is 1,4-butanediol. Quantitative determination of low-boiling substances is carried out using a Shimadzu-GC 2020 gas chromatograph, and quantitative analysis is carried out by comparing the retention time and peak area size with those of a standard substance. The relevant calculation formulas are as follows:

[0040]

[0041]

[0042] The yield of pyrrolidine = the conversion rate of 1,4-butanediol * the selectivity of pyrrolidine

[0043]

[0044] Among them, the flow rate unit of 1,4-butanediol is g / min, and the unit of the amount of the catalyst used is g.

[0045] The solution used for this catalyst is to perform ion exchange with Na zeolite, which becomes hydrogen-type zeolite after exchange. Since the zeolite and solution used for ion exchange are different, and the temperature and time of ion exchange are different, the Na + mass fraction, specific surface area, pore volume, pore diameter, strong acid amount, and total acid amount of the obtained hydrogen-type zeolite are all different, and thus show different catalytic effects on the reaction: Na + The more the mass fraction decreases compared to before exchange, the deeper the degree of ion exchange; the greater the increase in specific surface area, pore volume, and pore diameter, the better the pore structure of the catalyst; the greater the increase in strong acid amount and total acid amount, the more acidic sites of the catalyst are exposed; the above changes can enhance the catalytic activity of the catalyst for the reaction described in this application. The obtained catalyst is suitable for a continuous reactor, and a fixed-bed reactor is preferably used. During the reaction in a traditional batch reactor, a large amount of raw materials contact a small amount of catalyst, so the contact time and area between the raw materials and the catalyst are limited, resulting in the inability to improve the conversion rate of the raw materials with a small amount of catalyst; by using a fixed-bed reactor, continuous feeding and discharging can be carried out, and the contact time between the raw materials and the catalyst can be flexibly changed by adjusting the space velocity of the raw materials entering the fixed bed, enabling a small amount of raw materials to contact a large amount of catalyst, and reacting according to appropriate reaction conditions matched according to different requirements, thereby improving the conversion rate of the raw materials and the yield of the products. Moreover, the zeolite catalyst after ion exchange can be reused repeatedly for a long time and regenerated in the fixed bed, reducing production costs and labor costs, reducing the generation of waste, and being more environmentally friendly; the continuous production mode of the continuous reactor improves production efficiency.

[0046] Preparation Examples 1-12

[0047] Example 1

[0048] Na-ZSM5 zeolite powder with a particle size of 200 - 240 mesh was pressed into tablets under a pressure of 20 - 30 Mpa using a hydraulic powder press to obtain a Na-ZSM5 catalyst.

[0049] Example 2

[0050] 500 g of 1 mol / L NH4Cl solution was mixed and stirred with 50 g of Na-ZSM5 zeolite powder with a particle size of 200 - 240 mesh. After exchanging at 50 °C for 4 h, suction filtration, drying, and calcination were carried out. After repeating the above exchange treatment 2 times for the obtained dry powder, the powder was pressed into tablets under a pressure of 20 - 30 Mpa using a hydraulic powder press to obtain an HZSM5-1 catalyst.

[0051] Example 3

[0052] Mix 500 g of 1 mol / L NH₄NO₃ solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 50 °C for 4 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder 2 more times, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-2 catalyst.

[0053] Example 4

[0054] Mix 500 g of 0.2 mol / L HCl solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 50 °C for 4 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder 2 more times, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-3 catalyst.

[0055] Example 5

[0056] Mix 500 g of 1 mol / L NH₄Cl solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 90 °C for 4 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder 2 more times, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-4 catalyst.

[0057] Example 6

[0058] Mix 500 g of 1 mol / L NH₄Cl solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 120 °C for 4 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder 2 more times, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-5 catalyst.

[0059] Example 7

[0060] Mix 500 g of 1 mol / L NH₄Cl solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 90 °C for 24 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder 2 more times, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-6 catalyst.

[0061] Example 8

[0062] Mix 500 g of 1 mol / L NH4Cl solution with 50 g of 200 - 240 mesh Na-ZSM5 molecular sieve powder and stir. After exchanging at 90 °C for 48 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment 2 times on the obtained dry powder, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HZSM5-7 catalyst.

[0063] Example 9

[0064] 200 - 240 mesh Na-Y molecular sieve powder, use an oil pressure type powder tableting machine to tablet at a pressure of 20 - 30 Mpa to obtain the Na-Y catalyst.

[0065] Example 10

[0066] Mix 500 g of 1 mol / L NH4Cl solution with 50 g of 200 - 240 mesh Na-Y molecular sieve powder and stir. After exchanging at 90 °C for 24 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment 2 times on the obtained dry powder, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the HY-6 catalyst.

[0067] Example 11

[0068] 200 - 240 mesh Na-β molecular sieve powder, use an oil pressure type powder tableting machine to tablet at a pressure of 20 - 30 Mpa to obtain the Na-β catalyst.

[0069] Example 12

[0070] Mix 500 g of 1 mol / L NH4Cl solution with 50 g of 200 - 240 mesh Na-β molecular sieve powder and stir. After exchanging at 90 °C for 24 h, perform suction filtration, drying, and calcination. After repeating the above exchange treatment 2 times on the obtained dry powder, use an oil pressure type powder tableting machine to tablet the powder at a pressure of 20 - 30 Mpa to obtain the Hβ-6 catalyst.

[0071] The reaction conditions in Examples 1 to 12 and the characterization results of the prepared catalysts are shown in Tables 1 and 2 below.

[0072] Table 1. Characterization Results of Different Ion Exchange Catalysts

[0073]

[0074] Table 2. Reaction Conditions in Examples 1 to 12

[0075]

[0076]

[0077] The characterization results and reaction results of three kinds of molecular sieves without ion exchange prepared in Examples 1, 9, and 11; Examples 2-4 are the screening of ion exchange solutions for ZSM5 molecular sieves at an exchange temperature of 50 °C and an exchange time of 4 h; Examples 2, 5, and 6 are the screening of exchange temperatures for ZSM5 molecular sieves in NH4Cl solution and an exchange time of 4 h; Examples 5, 7, and 8 are the screening of exchange times for ZSM5 molecular sieves in NH4Cl solution and an exchange temperature of 90 °C; Examples 7, 10, and 12 are the screening of molecular sieve types in NH4Cl solution, an exchange temperature of 90 °C, and an exchange time of 24 h.

[0078] Test Examples 1-12

[0079] Pyrrolidine is prepared by the following steps:

[0080] The tablet catalysts prepared in Examples 1 to 12 were crushed to a particle size of 20-40 mesh. The treated catalyst was added to a fixed-bed reaction tube (outer diameter 2.2 cm, inner diameter 1.2 cm, length 50 cm). The same reaction conditions (reaction temperature 320 °C, space velocity 0.06 h -1 , atmospheric pressure, and the molar ratio of 1,4-butanediol to ammonia of 1:20) were fixed. The temperature was raised to the reaction temperature under an ammonia atmosphere. After the temperature and pressure were stabilized, the raw materials were fed into the fixed-bed reactor at a fixed space velocity for reaction. The reaction results using different raw materials and different catalysts are shown in Table 3.

[0081] Table 3. Reaction results of using different ion-exchanged catalysts with 1,4-butanediol as the raw material

[0082]

[0083]

[0084] As can be seen from the data in Table 3, using 1,4-butanediol as the raw material, the catalyst in Example 1 is un-ion-exchanged Na-ZSM5 zeolite, and the pyrrolidine yield is 9.83%. The yields in Examples 2-4 are 49.6%, 37.2%, and 30.9% respectively after Na-ZSM5 is ion-exchanged with NH4Cl, NH4NO3, and HCl solutions. It can be seen that the yield is the highest after ion-exchange with NH4Cl solution; Examples 2, 5, and 6 are for screening different exchange temperatures of Na-ZSM5 zeolite in NH4Cl solution with an exchange time of 4 h. It can be seen that the yield is the highest when the exchange temperature is 90 °C, which is 71.3%; Examples 5, 7, and 8 are for screening different exchange times of Na-ZSM5 zeolite in NH4Cl solution at an exchange temperature of 90 °C. It can be seen that the yields are comparable when the exchange times are 24 h and 48 h, which are 92.4% and 92.7% respectively. Considering the time cost, 24 h is the best; Examples 9 and 11 are un-ion-exchanged Na-Y and Na-β zeolites, and their yields are 6.61% and 7.29% respectively; Examples 10 and 12 are Na-Y and Na-β ion-exchanged with NH4Cl solution, and the yields are 35.6% and 77.1% respectively at an exchange temperature of 90 °C and an exchange time of 24 h. Compared with the yield of 92.4% in Example 7, it can be seen that the result is optimal when Na-ZSM5 is ion-exchanged with NH4Cl solution at an exchange temperature of 90 °C and an exchange time of 24 h.

[0085] Test Examples 13-24

[0086] Pyrrolidine is prepared through the following steps:

[0087] The tablet catalysts prepared in Examples 1 to 12 are crushed to a particle size of 20-40 mesh. The treated catalyst is added to a fixed-bed reaction tube (outer diameter 2.2 cm, inner diameter 1.2 cm, length 50 cm). Under the same reaction conditions (reaction temperature 320 °C, space velocity 0.06 h -1 -1, atmospheric pressure, and the molar ratio of tetrahydrofuran to ammonia is 1:20), it is heated to the reaction temperature in an ammonia atmosphere. After the temperature and pressure are stabilized, the raw materials are fed into the fixed-bed reactor at a fixed space velocity for reaction. The reaction results using different raw materials and different catalysts are shown in Table 4.

[0088] Table 4. Reaction results using different ion-exchanged catalysts with tetrahydrofuran as the raw material

[0089]

[0090]

[0091] As can be seen from the data in Table 4, using tetrahydrofuran as the raw material, the catalyst in Example 1 is un-ion-exchanged Na-ZSM5 zeolite, and the yield of pyrrolidine is 10.3%. The yields of Examples 2-4 are 48.7%, 38.6%, and 31.2% respectively after Na-ZSM5 is ion-exchanged with NH4Cl, NH4NO3, and HCl solutions. It can be seen that the yield is the highest after ion-exchange with the NH4Cl solution; Examples 2, 5, and 6 are used to screen different exchange temperatures of Na-ZSM5 zeolite in the NH4Cl solution with an exchange time of 4 h. It can be seen that the yield is the highest when the exchange temperature is 90 °C, which is 70.0%; Examples 5, 7, and 8 are used to screen different exchange times of Na-ZSM5 zeolite in the NH4Cl solution with an exchange temperature of 90 °C. It can be seen that the yields are equivalent when the exchange times are 24 h and 48 h, which are 92.7% and 93.1% respectively. Considering the time cost, 24 h is the best; Examples 9 and 11 are un-ion-exchanged Na-Y and Na-β zeolites, and their yields are 6.54% and 7.11% respectively; Examples 10 and 12 are Na-Y and Na-β ion-exchanged with the NH4Cl solution. When the exchange temperature is 90 °C and the exchange time is 24 h, the yields are 37.2% and 75.8% respectively. Compared with the yield of 92.7% in Example 7, it can be seen that the result is optimal when Na-ZSM5 is ion-exchanged with the NH4Cl solution, the exchange temperature is 90 °C, and the exchange time is 24 h.

[0092] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for continuously synthesizing pyrrolidine, comprising the following steps: (1) Add a catalyst into a continuous reactor, and heat it to the reaction temperature under a nitrogen atmosphere to activate the catalyst; (2) After the temperature is stabilized, feed the raw materials and the ammonia source into the continuous reactor for reaction; (3) After the reaction is completed, the crude reaction product enters the storage tank after condensation and gas-liquid separation; (4) The crude reaction product after being treated in step (3) is rectified to obtain a product with qualified purity.

2. The method for continuously synthesizing pyrrolidine according to claim 1, wherein, The continuous reactor is selected from any one of a continuous stirred tank reactor, a plug flow reactor, a fixed bed reactor, and a fluidized bed reactor, or a mixed reactor formed by connecting two or more of these reactors as the continuous reactor, preferably a fixed bed reactor or a fluidized bed reactor.

3. The method for continuously synthesizing pyrrolidine according to claim 1, wherein The reaction temperature in step (1) ranges from 250 to 400 °C.

4. The method for continuously synthesizing pyrrolidine according to claim 1, wherein The raw materials in step (2) are selected from 1,4-butanediol and tetrahydrofuran; Preferably, the ammonia source in step (2) is selected from ammonia gas and ammonia water; Preferably, the space velocity of the raw materials in the step (2) is 0.05 - 50 h -1 ; Preferably, the molar ratio of the raw materials to the ammonia source in step (2) is 1:2 to 1:100; Preferably, the reaction pressure in step (2) is from atmospheric pressure to 2 MPa.

5. The method for continuously synthesizing pyrrolidine according to claim 1, wherein The rectification conditions in step (4) are atmospheric rectification, with 35 - 40 theoretical plates, a column bottom temperature of 95 - 105 °C, a distillate head temperature of 65 - 75 °C, and a reflux: take-off ratio of 1:1 to 10:

1.

6. The method for continuously synthesizing pyrrolidine according to claim 1, wherein The catalyst is selected from one or more hydrogen-type molecular sieve catalysts of Na-ZSM-5, Na-Y, Na-β, Na-ZSM-11, and Na-MOR treated by ion exchange, preferably one or more hydrogen-type molecular sieve catalysts of Na-ZSM-5, Na-Y, and Na-β.

7. The method for continuously synthesizing pyrrolidine according to claim 6, wherein The hydrogen-type molecular sieve catalyst is prepared by the following method: Mix and stir an ion exchange solution with a mass ratio of 1:1 to 100:1 with a molecular sieve powder of 200 - 240 mesh. After exchanging for a certain time at a certain temperature, perform suction filtration, drying, and calcination. After repeating the above exchange treatment on the obtained dry powder at least 1 more time, press the powder into tablets at a pressure of 20 - 30 Mpa using a hydraulic powder tablet press to obtain the ion-exchanged hydrogen-type molecular sieve catalyst.

8. The method for continuously synthesizing pyrrolidine according to claim 7, characterized in that, The pore size range of the molecular sieve powder is 2.5 - 4.0 nm; Preferably, the specific surface area of the hydrogen-form molecular sieve catalyst is 330 - 430 m 2 ·g -1 , the total pore volume is 0.33 - 0.36 mL·g -1 , and the pore diameter is 3.2 - 4.8 nm; Preferably, the ion exchange solution is one of a 1 mol / L NH4Cl solution, a 1 mol / L NH4NO3 solution, and a 0.2 mol / L HCl solution; Preferably, the mass ratio of the ion exchange solution used to the molecular sieve powder is 1:1 to 50:1, more preferably 5:1 to 20:1, and even more preferably 10:1; Preferably, the molecular sieve powder is one or more molecular sieve powders of Na-ZSM-5, Na-Y, Na-β, Na-ZSM-11, and Na-MOR, preferably one or more molecular sieve powders of Na-ZSM-5, Na-Y, and Na-β; Preferably, the ion exchange temperature is 50 - 120 °C, preferably 80 - 100 °C; Preferably, the ion exchange time therein is 2 - 48 h, preferably 12 - 36 h.

Images