A continuous method for preparing N-methylpyrrolidone

Abstract

The invention belongs to the technical field of chemical industry, and discloses a continuous preparation method of N-methylpyrrolidone, comprising: putting raw materials into a first mixer and mixing them, and then entering a reaction tower I filled with a balance catalyst through a heat exchanger; the generated monomethylamine, dimethylamine and trimethylamine continuously flow into a rectification tower I from the bottom of the tower to remove unreacted ammonia in the system, and the ammonia is removed as a first light component from the top of the rectification tower I, and the bottom distillate is a first heavy component, which flows into a reaction tower II, and dimethylamine and trimethylamine in the reaction tower II undergo hydrolysis reaction to generate monomethylamine; then the dimethylamine flows into a second mixer, and after mixing with gamma-butyrolactone in the second mixer, flows into a reaction tower III to carry out a synthesis reaction of N-methylpyrrolidone; after the reaction is completed, the raw materials enter the rectification tower II for rectification, and the second heavy component N-methylpyrrolidone crude product obtained in the bottom of the tower enters the rectification tower III for further purification, and the third light component at the top of the tower is N-methylpyrrolidone.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry and relates to a continuous preparation method of N-methylpyrrolidone. Background Art

[0002] N-methylpyrrolidone is a polar solvent with strong selectivity and good stability. It is widely used in aromatic extraction, acetylene purification, lubricating oil refining, etc. It is an extractant for butadiene and isoprene. It can be used for cleaning precision instruments and circuit boards in the semiconductor industry. It is also an electrode auxiliary material for lithium-ion batteries. The existing industrial production methods of N-methylpyrrolidone are mainly divided into three synthetic routes. The first is a non-catalytic synthesis process using γ-butyrolactone and monomethylamine (monomethylamine) as starting materials. The second is a non-catalytic synthesis process using γ-butyrolactone and mixed amines as starting materials. The third is a catalytic synthesis using γ-butyrolactone and monomethylamine as raw materials and a catalytic synthesis process using 1,4-butanediol catalytic dehydrogenation-amination to synthesize N-methylpyrrolidone.

[0003] Although the above method 1 can make the product refining and purification simple, the raw material monomethylamine used in this process route requires an amine separation device (mixed methylamine requires five towers for separation, namely deamination, extraction, dehydration, separation, and environmental protection treatment), which leads to increased investment and operating costs, and reduced profits due to industrial production; the above method 2 uses mixed amines, does not require a mixed amine separation device, has low investment and low consumption, but the proportion of dimethylamine and trimethylamine is too large, which reduces the conversion rate of γ-butyrolactone and has low synthesis efficiency; the above method 3 often requires the addition of a metal oxide catalyst to directly introduce γ-butyrolactone into monomethylamine for dehydration reaction to generate N-methylpyrrolidone, abandoning the process of purifying γ-butyrolactone, which is easy to separate and purify, and the intermediate product in the reaction is easy to separate, but the cost of using and recovering the catalyst is high. In addition, although other dehydrogenation catalysts such as Cr catalysts can increase the yield of N-methylpyrrolidone, they will cause greater harm to the environment and human body, and the cost of wastewater treatment is high. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems in the prior art and to provide a continuous method for preparing N-methylpyrrolidone which is environmentally friendly, simple in procedure, high in yield and energy-saving.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A continuous method for preparing N-methylpyrrolidone, the method comprising:

[0007] The raw materials (methanol and liquid ammonia) are put into the first mixer and mixed, and then enter the reaction tower I filled with a balance catalyst through a heat exchanger; the generated monomethylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA) continuously flow into the distillation tower I from the bottom of the tower to remove the unreacted ammonia in the system, and the ammonia is removed as the first light component from the top of the distillation tower I, and the bottom distillate is the first heavy component, which flows into the reaction tower II, and the dimethylamine and trimethylamine in the reaction tower II undergo hydrolysis reaction to generate monomethylamine; then flow into the second mixer, mix with γ-butyrolactone (GBL) in the second mixer, and then flow into the reaction tower III for N-methylpyrrolidone (NMP) synthesis reaction; after the reaction is completed, enter the distillation tower II for distillation, and the second heavy component N-methylpyrrolidone (NMP) crude product obtained in the bottom of the tower enters the distillation tower III for further purification, and the third light component at the top of the tower is N-methylpyrrolidone (NMP).

[0008] The present application improves the existing method for preparing N-methylpyrrolidone, wherein dimethylamine and trimethylamine in the generated mixed methylamine are first converted into monomethylamine, which is then reacted with γ-butyrolactone, thereby increasing the yield of N-methylpyrrolidone and avoiding the separate separation procedure of methylamine; compared with directly using a monomethylamine solution, the raw material cost and the processing cost are reduced; compared with directly using a mixed methylamine to react with γ-butyrolactone, the conversion rate of GBL can be better improved.

[0009] Preferably, the raw materials in the first mixer include methanol and liquid ammonia.

[0010] More preferably, the molar ratio of ammonia to methanol, N / C, is (1.0-5.0):1.

[0011] More preferably, the molar ratio of ammonia to methanol, N / C, is (1.5-3.5):1.

[0012] Preferably, the equilibrium catalyst loaded in the catalyst bed of the reaction tower I is a zeolite molecular sieve.

[0013] More preferably, the equilibrium catalyst in the reaction tower I is filled to the middle of the reactor, with a filling amount of 40% to 60%.

[0014] Preferably, the content ratio of monomethylamine, dimethylamine and trimethylamine generated in the reaction tower I is (30-55):(25-35):(10-45).

[0015] Preferably, the temperature in the reaction tower I is 415-430°C, and the reaction space velocity is 2-5h -1 , the pressure is 1.7~3.5MPa.

[0016] Preferably, the first heavy component in the distillation tower I includes mixed methylamine, water, and a small amount of unreacted methanol.

[0017] Preferably, the top outlet temperature of the distillation tower I is 30-50° C., and the absolute pressure is 1-3 MPa.

[0018] Preferably, after the reaction, the content of dimethylamine in the reaction tower II is 0-2 wt%, the content of trimethylamine is 0-4 wt%, and the water content is 30-50%.

[0019] Preferably, the temperature of the reaction tower II is 220-300° C., and the reaction time is 4-8 hours.

[0020] Preferably, the amount of water added to the reaction tower II is 35-55% of the first heavy component.

[0021] Preferably, the mass ratio of monomethylamine to γ-butyrolactone in the second mixer is (1-3):1.

[0022] Preferably, the temperature of the reaction tower III is 250-300° C., and the pressure is 6-14 MPa.

[0023] Preferably, the second light component, including unreacted monomethylamine, dimethylamine, trimethylamine, and water and methanol produced by the reaction, is taken out from the top of the rectification tower II and fed back into the reaction tower II to continue the hydrolysis reaction.

[0024] Preferably, the pressure of the distillation tower II is atmospheric pressure, the tower top temperature is 40-130°C, and the tower bottom temperature is 120-170°C.

[0025] More preferably, the reflux time in the distillation tower II is 0.1 to 2 h.

[0026] Preferably, the pressure of the rectification tower III is reduced pressure, and the high vacuum degree is 10 mmHg; the tower top temperature is 80-84°C, and the tower bottom temperature is 100-160°C.

[0027] Further preferably, the heavy components in the bottom of the distillation tower III are treated as waste liquid.

[0028] Preferably, the reaction residence time of the whole process is 4 to 16 hours.

[0029] More preferably, the reaction residence time of the whole process is 5 to 10 hours.

[0030] Preferably, the yield of N-methylpyrrolidone (NMP) is 99.6-99.9%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. In the continuous preparation method of N-methylpyrrolidone of the present invention, the participation of dimethylamine (DMA) and trimethylamine (TMA) with low conversion rate in NMP synthesis is reduced, the conversion rate of γ-butyrolactone is increased, the production cost is reduced, and the overall benefit is improved.

[0033] 2. The continuous preparation method of N-methylpyrrolidone of the present invention does not require a separate distillation process for separating ammonia, thereby reducing the distillation cost for separating ammonia, and the mixed methylamine obtained by the amination reaction is directly subjected to a hydrolysis reaction, thereby saving procedures.

[0034] 3. In the continuous preparation method of N-methylpyrrolidone of the present invention, the reflux ratio of dimethylamine (DMA) and trimethylamine (TMA) in the distillation tower II to the reaction tower II is adjusted to reduce the separation cost of the mixed amines, improve the conversion rate of γ-butyrolactone, and reduce the process energy consumption.

[0035] 4. The continuous preparation method of N-methylpyrrolidone of the present invention is a continuous production method, which avoids the problems of long reaction cycle in traditional intermittent production and makes the reaction process more stable and safe.

[0036] 5. The continuous preparation method of N-methylpyrrolidone of the present invention is easier to achieve closed and automated, reduces labor costs, increases reaction yield, and improves product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a continuous process flow chart for preparing N-methylpyrrolidone.

[0038] 1. first mixer, 2. reaction tower I, 3. distillation tower I, 4. reaction tower II, 5. second mixer, 6. reaction tower III, 7. distillation tower II, 8. distillation tower III, 9. heat exchanger, 10. feed pump, 11. condenser, 12. storage tank; A. methanol, B. liquid ammonia, C. monomethylamine, D. dimethylamine, E. trimethylamine, F. water, G. γ-butyrolactone, H. crude N-methylpyrrolidone, I. N-methylpyrrolidone, J. waste liquid. DETAILED DESCRIPTION

[0039] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0040] The process flow chart of continuous N-methylpyrrolidone of the present invention is as follows Figure 1 As shown, specifically including:

[0041] Methanol A and liquid ammonia B with a N / C molar ratio of (1.5-3.5):1 are put into the first mixer 1 and mixed, and then enter the reaction tower 2 filled with a balanced catalyst (zeolite molecular sieve) through the heat exchanger 9; the temperature in the reaction tower 2 is 415-430°C, the reaction time is 0.5h, the pressure is 1.7-3.5Mpa, and the air velocity is 2-5h -1 The generated monomethylamine (MMA) C, dimethylamine (DMA) D, and trimethylamine (TMA) E continuously flow from the bottom of the tower through the feed pump 10 into the distillation tower 3.

[0042] Including the following reaction equation:

[0043]

[0044] After the reaction in the distillation tower I 3, unreacted ammonia B in the system is removed, and ammonia B is removed as the first light component from the top of the distillation tower I 3. The top temperature is 30-50°C, and the absolute pressure is 1-3 MPa. The top component is cooled by the condenser 11, and the liquid ammonia B returns to the mixer 1. The other components after condensation are stored in the storage tank 12 and returned to the distillation tower I 3; the first heavy component (monomethylamine C, dimethylamine D, trimethylamine E, water F, and a small amount of unreacted methanol A) enters the reaction tower II 4 as the bottom distillate through the feed pump 10.

[0045] Water F is added to the reaction tower II 4 to undergo a hydrolysis reaction with dimethylamine D and trimethylamine E at a temperature of 220 to 300° C. Under normal pressure, the monomethylamine C with a high conversion rate is generated, wherein the mass ratio of the first heavy component to water F is 1:(0.35 to 0.55). After the reaction, the content of dimethylamine in the mixed amine solution is 0 to 7 wt%, the content of trimethylamine is 0 to 6 wt%, and the water content is 30 to 50%.

[0046] Including the following reaction equation:

[0047]

[0048] The mixed liquid flows into the second mixer 5 through the feed pump 10, and is evenly mixed with the γ-butyrolactone (GBL) G in the second mixer 5, and the mass ratio of monomethylamine C and γ-butyrolactone (GBL) G is (1-3):1; it continues to flow into the reaction tower III 6 through the feed pump 10 for N-methylpyrrolidone (NMP) synthesis reaction, the temperature is 250-300°C, the time is 1-6 hours, and the pressure is 5.0-10.0Mpa.

[0049] After the reaction is completed, it enters the distillation tower II 7 through the feed pump 10 for distillation, the tower top temperature is 40-130°C, the time is 1-3h, and the pressure is normal pressure; the second light component at the top of the tower includes monomethylamine C, dimethylamine D, trimethylamine E, water F, and methanol A generated by the reaction, which returns to the reaction tower II 4 and re-enters the reaction system, and the reflux time is 0.1-2h; the tower bottom temperature of the distillation tower II 7 is 120-170°C, and the second heavy component N-methylpyrrolidone (NMP) crude product H is obtained in the tower bottom.

[0050] Including the following reaction equation:

[0051]

[0052] The crude N-methylpyrrolidone (NMP) H enters the distillation tower III 8 through the feed pump 10 for further purification. The pressure in the distillation tower III 8 is 10 mmHg, the top temperature is 80-84°C, the third light component at the top is N-methylpyrrolidone (NMP) I, the bottom temperature is 100-160°C, and the third heavy component in the bottom is waste liquid J.

[0053] Example 1

[0054] Methanol A and liquid ammonia B with a N / C molar ratio of 3:1 are put into the first mixer 1 and mixed, and then enter the reaction tower 2 filled with a balanced catalyst (zeolite molecular sieve HZSM-5) through the heat exchanger 9; the temperature in the reaction tower 2 is 420°C, the residence time is 0.5h, the pressure is 2.3Mpa, and the reaction space velocity is 2.3h -1 The generated monomethylamine (MMA) C, dimethylamine (DMA) D, and trimethylamine (TMA) E continuously flow from the bottom of the tower through the feed pump 10 into the distillation tower 3.

[0055] After the reaction in the distillation tower I 3, unreacted ammonia B in the system is removed, and ammonia B is removed as the first light component from the top of the distillation tower I 3. The top temperature is 40°C and the absolute pressure is 2 MPa. The top component is cooled by the condenser 11, and the liquid ammonia B returns to the mixer 1. The other components after condensation are stored in the storage tank 12 and returned to the distillation tower I 3; the first heavy component (monomethylamine C, dimethylamine D, trimethylamine E, water F, and a small amount of unreacted methanol A) enters the reaction tower II 4 as the bottom distillate through the feed pump 10.

[0056] Water F is added to the reaction tower II 4 to undergo a hydrolysis reaction with dimethylamine D and trimethylamine E at a temperature of 270° C. for 6 hours. Monomethylamine C with a high conversion rate is generated by hydrolysis under normal pressure, wherein the mass ratio of the first heavy component to water F is 1:0.4, and the mass ratio of monomethylamine C, dimethylamine D, and trimethylamine E in the mixed solution after the reaction is 97:0.9:2.1.

[0057] The mixed liquid flows into the second mixer 5 through the feed pump 10, and is evenly mixed with the γ-butyrolactone (GBL) G in the second mixer 5, and the molar ratio of monomethylamine C to γ-butyrolactone (GBL) G is 1.6:1; it continues to flow into the reaction tower III 6 through the feed pump 10 for N-methylpyrrolidone (NMP) synthesis reaction, the temperature is 270°C, the time is 3 hours, and the pressure is 7 MPa.

[0058] After the reaction is completed, it enters the distillation tower II 7 through the feed pump 10 for distillation. The tower top temperature is 90°C and the pressure is normal pressure. The second light component at the top of the tower includes monomethylamine C, dimethylamine D, trimethylamine E, water F, and methanol A generated by the reaction. After the reflux time is 0.5h, the second light component is applied to the reaction tower II 4 to re-enter the reaction system. The bottom temperature of the distillation tower II 7 is 150°C, and the bottom of the tower obtains the second heavy component N-methylpyrrolidone (NMP) crude product H.

[0059] The crude N-methylpyrrolidone (NMP) H enters the distillation tower III 8 through the feed pump 10 for further purification. The pressure in the distillation tower III 8 is 10 mmHg, the tower top temperature is 82°C, the third light component at the top of the tower is N-methylpyrrolidone (NMP) I, the tower bottom temperature is 140°C, and the third heavy component in the tower bottom is waste liquid J.

[0060] The purity of N-methylpyrrolidone (NMP) I was 99.99%, and the yield was 99.9%.

[0061] Embodiments 2 to 47

[0062] Compared with Example 1, the difference is that the preparation is carried out according to the parameters in Table 1, and the specific yield is shown in Table 1.

[0063] Comparative Example 1

[0064] Compared with Example 1, the difference is that the mixed methylamine obtained in the distillation tower I is directly mixed with γ-butyrolactone and then reacted in the reaction tower III, and the subsequent steps are the same.

[0065] The purity of N-methylpyrrolidone (NMP) I was 99.99% and the yield was 94.5%.

[0066] Comparative Example 2

[0067] Compared with Example 1, the difference is that a conventional process is used to prepare mixed methylamine, and the content ratio of monomethylamine, dimethylamine and trimethylamine is 27:23:50; the mixed methylamine is directly mixed with γ-butyrolactone and reacted in the reaction tower III, and the subsequent steps are the same.

[0068] The purity of N-methylpyrrolidone (NMP) I was 99.99% and the yield was 93.1%.

[0069] Table 1. Preparation process parameters and product yield data

[0070]

[0071] In summary, in the continuous preparation method of N-methylpyrrolidone of the present invention, the participation of dimethylamine (DMA) and trimethylamine (TMA) with low conversion rate in NMP synthesis is reduced, the conversion rate of γ-butyrolactone is increased, the production cost is reduced, and the overall benefit is improved.

[0072] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A continuous method for preparing N-methylpyrrolidone, characterized in that: The preparation method comprises: adding raw material methanol and liquid ammonia into a first mixer and mixing them, and then passing through a heat exchanger to a reaction tower I filled with a balance catalyst; the generated monomethylamine, dimethylamine and trimethylamine continuously flow into a rectification tower I from the bottom of the tower to remove unreacted ammonia in the system, and the ammonia is removed as a first light component from the top of the rectification tower I, and the bottom distillate is a first heavy component, which flows into a reaction tower II, and dimethylamine and trimethylamine in the reaction tower II undergo hydrolysis reaction to generate monomethylamine; then the dimethylamine and trimethylamine flow into a second mixer, and after mixing with gamma-butyrolactone in the second mixer, flow into a reaction tower III to perform an N-methylpyrrolidone synthesis reaction; after the reaction is completed, the dimethylamine and trimethylamine flow into the rectification tower II for rectification, and the second heavy component N-methylpyrrolidone crude product obtained in the bottom of the tower flows into the rectification tower III for further purification, and the third light component at the top of the tower is N-methylpyrrolidone.

2. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The molar ratio of ammonia to methanol in the first mixer is (1.0-5.0):

1.

3. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The equilibrium catalyst loaded in the catalyst bed of the reaction tower I is zeolite molecular sieve.

4. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The content ratio of monomethylamine, dimethylamine and trimethylamine generated in the reaction tower I is (30-55): (25-35): (10-45).

5. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The temperature in the reaction tower I is 415-430°C, and the reaction space velocity is 2-5h -1 , pressure is 1.7~3.5MPa.

6. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: After the reaction, the content of dimethylamine in the reaction tower II is 0-2wt%, the content of trimethylamine is 0-4wt%, and the water content is 30-50%.

7. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The second light component, including unreacted monomethylamine, dimethylamine, trimethylamine, and water and methanol produced by the reaction, is taken out from the top of the rectification tower II and returned to the reaction tower II to continue the hydrolysis reaction.

8. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The temperature of the reaction tower II is 220-300° C., and the reaction time is 4-8 hours.

9. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The amount of water added to the reaction II tower is 35-55 wt % of the first heavy component.

10. The continuous method for preparing N-methylpyrrolidone according to claim 1, characterized in that: The mass ratio of monomethylamine to γ-butyrolactone in the second mixer is (1-3):1.

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