Synthesis method of 1, 8-diazabicyclo (5, 4, 0)-7-undecene

Abstract

The invention discloses a synthesis method of 1, 8-diazabicyclo (5, 4, 0)-7-undecene, and belongs to the technical field of organic alkali compounds. The synthesis method comprises the following steps: S1, in a fixed bed reactor I, enabling a solution containing caprolactam and acrylonitrile to be in contact I with a layered double-metal hydroxide catalyst, and reacting I to obtain an addition product N-(beta-cyanoethyl) caprolactam; and S2, in a fixed bed reactor II, enabling the addition product N-(beta-cyanoethyl) caprolactam in the step S1 and hydrogen to be in contact II with a molecular sieve catalyst loaded with noble metal, and reacting II to obtain the 1, 8-diazabicyclo (5, 4, 0)-7-undecene. The synthesis method is mild in reaction condition, simple to operate and capable of being continuously carried out.

Description

Technical Field

[0001] The present application relates to a method for synthesizing 1,8-diazabicyclo(5,4,0)-7-undecene, and belongs to the technical field of organic base compounds. Background Art

[0002] Organic bases not only have good solubility in organic solvents, but also can be widely used in the field of organic chemical synthesis through fine tuning of molecular structure. 1,8-diazabicyclo(5,4,0)-7-undecene (DBU) as a strong organic base plays an important role in CO2 capture and conversion, medicine, polyurethane and other fields. The synthesis methods of DBU reported in the literature mainly include aziridine Lactam method, lactam Acrylonitrile Hofmann reaction, lactone The main problems of the ethylenediamine method, etc. are low yield, large catalyst loss, complicated separation operation, high production cost, flammability of Raney nickel in the air, and explosion of high-pressure hydrogen reactor.

[0003] The patent with publication number CN 112500418 A uses KOH or NaOH as a catalyst to carry out an acrylonitrile addition reaction, and then undergoes hydrogenation and cyclization to prepare DBU. However, there are problems such as high addition reaction temperature, easy generation of by-products, and low overall DBU yield of only 82%. The patent with publication number CN114478540A reports a method of using aromatic hydrocarbons as solvents and an organic base and a phase transfer catalyst as a mixed catalyst to carry out an addition reaction to obtain an intermediate The crude (cyanoethyl) caprolactam product is then subjected to cyano hydrogenation reduction via Raney Ni / methanol / auxiliary agent, and finally a cyclization reaction is performed to obtain DBU. This process improves the overall yield of the reaction to a certain extent, but there are problems such as low yield of Raney nickel hydrogenation, large catalyst loss, high production cost, flammability of Raney nickel in the air, and explosion of high-pressure hydrogen reactors. In addition, the overall reaction uses two solvents, methanol and xylene, which makes solvent recovery and management difficult. Therefore, it is of great significance to develop a DBU preparation process with mild reaction conditions, simple operation, and continuous operation. Summary of the invention

[0004] In order to solve the problems of poor reaction conditions safety, great difficulty in post-treatment and difficulty in continuous operation in the prior art for preparing 1,8-diazabicyclo (5,4,0)-7-undecene, the present application proposes a new synthesis method with mild reaction conditions, simple post-treatment and continuous operation, which replaces the traditional kettle reaction hydrogenation process with a fixed bed reaction process, and can effectively reduce the production safety risk of 1,8-diazabicyclo (5,4,0)-7-undecene.

[0005] This application adopts the following technical solutions:

[0006] According to the first aspect of the present application, a method for synthesizing 1,8-diazabicyclo (5,4,0)-7-undecene is provided, comprising the following steps:

[0007] S1, in a fixed bed reactor I, contacting a solution containing caprolactam and acrylonitrile with a layered double metal hydroxide catalyst I, and reacting I to obtain an addition product N-(β-cyanoethyl) caprolactam;

[0008] S2. In a fixed bed reactor II, the addition product N-(β-cyanoethyl)caprolactam of step S1 and hydrogen are contacted with a noble metal-loaded molecular sieve catalyst II, and the 1,8-diazabicyclo(5,4,0)-7-undecene is obtained by reaction II.

[0009] Reaction II is a hydrogenation-dehydration cyclization process.

[0010] Optionally, in step S1, the layered double metal hydroxide catalyst is selected from at least one layered double metal hydroxide of MgAl-LDH, ZnAl-LDH, NiAl-LDH, and NiFe-LDH.

[0011] Optionally, in step S2, the molecular sieve in the noble metal-loaded molecular sieve catalyst is selected from at least one hydrogen-type molecular sieve selected from HY, H-Beta, and H-ZSM-5.

[0012] Optionally, in step S2, the noble metal in the noble metal-loaded molecular sieve catalyst is selected from at least one of Ru, Rh, Pd, Pt, and Ir.

[0013] Optionally, in step S1, the conditions of contacting I include: the solution containing caprolactam and acrylonitrile is introduced simultaneously with the inert gas, and the rate of the solution containing caprolactam and acrylonitrile is 5 to 10 mL / min;

[0014] The rate of inactive gas is 5 to 15 L / min.

[0015] Optionally, in step S1, the conditions of reaction I include: reaction temperature of 20 to 80°C, reaction pressure of 1 to 8 atm, reaction space velocity of 0.1 to 2 h -1 .

[0016] Optionally, in step S1, the conditions for reaction I include: a reaction temperature of 30 ～ 75℃, reaction pressure 1~5atm, reaction space velocity 0.2~1.5h -1 .

[0017] Optionally, in step S2, the conditions of contacting II include: the rate of N-(β-cyanoethyl)caprolactam is 20 to 30 mL / min;

[0018] The rate of inactive gas is 20-30 L / min.

[0019] Optionally, in step S2, the conditions of reaction II include: a reaction temperature of 120 ～ 200℃, reaction pressure 3~10MPa, reaction space velocity 0.5~5h -1 .

[0020] Optionally, in step S2, the conditions of reaction II include: a reaction temperature of 150 ～ 180℃, reaction pressure 4~8MPa, reaction space velocity 1~3h -1 .

[0021] Optionally, in step S1, in the solution containing caprolactam and acrylonitrile, the molar ratio of caprolactam to acrylonitrile is 1:1 to 1.1.

[0022] Optionally, in step S1, in the solution containing caprolactam and acrylonitrile, the molar ratio of caprolactam to acrylonitrile is 1:1 to 1.05.

[0023] Optionally, in step S1, the solution containing caprolactam and acrylonitrile further includes a solvent, and the solvent is selected from at least one of methanol, m-xylene, o-xylene, and p-xylene.

[0024] The beneficial effects of this application include:

[0025] The synthetic method of 1,8-diazabicyclo (5,4,0)-7-undecene provided in the present application adopts a multiphase catalyst-fixed bed reactor in the reaction process, which can effectively improve the yield of the target product and reduce the occurrence of hydrogenation side reactions compared with the traditional method; the fixed bed reactor is simpler to separate the products and has higher safety than the traditional kettle reactor. The synthetic method of 1,8-diazabicyclo (5,4,0)-7-undecene provided in the present application has mild reaction conditions, simple post-treatment, high raw material conversion rate, continuous reaction, and high product purity. DETAILED DESCRIPTION

[0026] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0027] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0028] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0029] Example 1

[0030] A) 1L Mg-Al LDH catalyst was added to a fixed bed reactor, and a solution 1 prepared by caprolactam (90.5kg, 800mol), acrylonitrile (43.3kg, 816mol) and 400L m-xylene was introduced into the reactor at a rate of 8.3ml / min and nitrogen (10L / min). Reaction temperature: 30°C, reaction pressure: 1atm, space velocity: 0.5h -1 The conversion rate of caprolactam is greater than 98%, and the selectivity of N-(β-cyanoethyl)caprolactam is greater than 99%.

[0031] B) Fill the next hydrocyclization reactor with 1 L of Pt / HY molecular sieve (silicon-aluminum ratio: 5), and introduce the product N-(β-cyanoethyl)caprolactam from the previous step reaction A) into the reactor at a rate of 24.9 ml / min and hydrogen (25 L / min). Reaction temperature: 150°C, reaction pressure: 5 MPa, space velocity: 1.5 h -1 , a distillation tower is used to recover meta-xylene and separate DBU, with a GC purity of 99.5%, and the overall yield of the process is 92.0%.

[0032] Example 2

[0033] Step A) The air velocity was changed to 1h -1 , the rest was prepared in the same manner as described in step A) of Example 1, the conversion of caprolactam was >95%, and the selectivity of N-(β-cyanoethyl)caprolactam was >99%.

[0034] Step B) The air speed was changed to 2h -1 , the rest was prepared in the same manner as described in step B) of Example 1, the GC purity of DBU was 99.0%, and the overall yield of the process was 88.0%.

[0035] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for synthesizing 1,8-diazabicyclo (5,4,0)-7-undecene, characterized in that: The steps include: S1, in a fixed bed reactor I, contacting a solution containing caprolactam and acrylonitrile with a layered double metal hydroxide catalyst I, and reacting I to obtain an addition product N-(β-cyanoethyl) caprolactam; S2. In a fixed bed reactor II, the addition product N-(β-cyanoethyl)caprolactam of step S1 and hydrogen are contacted with a noble metal-loaded molecular sieve catalyst II, and the 1,8-diazabicyclo(5,4,0)-7-undecene is obtained by reaction II.

2. The synthesis method according to claim 1, characterized in that In step S1, the layered double metal hydroxide catalyst is selected from at least one layered double metal hydroxide of MgAl-LDH, ZnAl-LDH, NiAl-LDH, and NiFe-LDH.

3. The synthesis method according to claim 1, characterized in that In step S2, the molecular sieve in the noble metal-loaded molecular sieve catalyst is selected from at least one hydrogen-type molecular sieve selected from HY, H-Beta, and H-ZSM-5.

4. The synthesis method according to claim 1, characterized in that In step S2, the noble metal in the noble metal-loaded molecular sieve catalyst is selected from at least one of Ru, Rh, Pd, Pt, and Ir.

5. The synthesis method according to claim 1, characterized in that In step S1, the conditions of contacting I include: the solution containing caprolactam and acrylonitrile is introduced simultaneously with the inert gas, and the rate of the solution containing caprolactam and acrylonitrile is 5 to 10 mL / min; The rate of inactive gas is 5 to 15 L / min.

6. The synthesis method according to claim 1, characterized in that In step S1, the conditions of reaction I include: reaction temperature of 20 to 80°C, reaction pressure of 1 to 8 atm, reaction space velocity of 0.1 to 2 h -1 .

7. The synthesis method according to claim 1, characterized in that In step S2, the conditions of contacting II include: the rate of N-(β-cyanoethyl)caprolactam is 20 to 30 mL / min; The rate of inactive gas is 20-30 L / min.

8. The synthesis method according to claim 1, characterized in that In step S2, the conditions of reaction II include: the reaction temperature is 120 ～ 200℃, reaction pressure 3~10MPa, reaction space velocity 0.5~5h -1 .

9. The synthesis method according to claim 1, characterized in that In step S1, in the solution containing caprolactam and acrylonitrile, the molar ratio of caprolactam to acrylonitrile is 1:1 to 1.

1.

10. The synthesis method according to claim 1, characterized in that In step S1, the solution containing caprolactam and acrylonitrile also includes a solvent, and the solvent is selected from at least one of methanol, m-xylene, o-xylene, and p-xylene.