Method for synthesizing adiponitrile from butadiene in one step

Abstract

The invention relates to the technical field of adiponitrile synthesis, in particular to the field of IPC C07C253, and more particularly relates to a method for synthesizing adiponitrile from butadiene in one step. Comprising the following steps: S1, respectively preheating butadiene, hydrocyanic acid and a catalytic system; s2, preliminarily mixing the preheated butadiene and hydrocyanic acid to form a first mixture; and S3, uniformly mixing the preheated catalytic system to form a second mixture. And S4, carrying out a microchannel reaction on the first mixture and the second mixture to obtain a crude product, and carrying out rectification separation to obtain the product. Through independent heating of the catalyst and the raw material and control of specific parameters, generation of impurities in a non-reactor can be reduced, thereby greatly improving purity and yield.

Description

Technical Field

[0001] The invention relates to the technical field of adiponitrile synthesis, in particular to the field of IPC C07C253, and more specifically to a method for synthesizing adiponitrile from butadiene in one step. Background Art

[0002] As an important chemical raw material, adiponitrile has a large market demand. At present, there are three main synthetic routes for adiponitrile in my country, namely, butadiene method, acrylonitrile method, and adipic acid method. Among them, the butadiene method is the most widely used, with the most mature technology and large production capacity. The butadiene method is further divided into butadiene direct cyanation method (three-step synthesis method), butadiene two-step synthesis method, and butadiene one-step synthesis method. Butadiene direct cyanation method includes three steps: primary hydrocyanation, isomerization, and secondary hydrocyanation. This process has many production equipment and needs to separate pentene nitrile before re-reaction. The whole process is complicated and the operating cost is high.

[0003] Chinese invention patent CN 103694136B directly adds raw materials and catalytic system into the reactor for decomposition, heating and reaction, and the conversion rate is only about 50%; Chinese invention patent CN108640854A discloses a method for synthesizing adiponitrile: the method for synthesizing adiponitrile includes the steps of reacting butadiene, hydrocyanic acid and catalytic system in a continuous reactor to obtain a product containing adiponitrile. The invention is mainly used to synthesize adiponitrile in a continuous reactor using the butadiene method, converting the intermittent reaction of the prior art into a continuous reaction and simplifying the process flow of adiponitrile synthesis, but the conversion rate is low, only 80%; Chinese utility model patent CN 207567142U preheats the raw materials and adds them into the microchannel reactor, and then mixes with the catalytic system preheated and added into the microchannel reactor, and then heats them together and adds them into the reactor to participate in the reaction, but there is still the problem of low reaction efficiency. Summary of the invention

[0004] The present invention provides a method for synthesizing adiponitrile from butadiene in one step, comprising the following steps:

[0005] Preheating butadiene, hydrocyanic acid and the catalyst system respectively;

[0006] Preliminarily mixing the preheated butadiene and hydrocyanic acid to form a first mixture;

[0007] The preheated catalyst system is mixed uniformly to form a second mixture.

[0008] The first mixture and the second mixture are subjected to microchannel reaction to obtain a crude product, which is then separated by distillation to obtain the product.

[0009] The microchannel reactor used in the microchannel reaction is our company's proprietary equipment (patent number CN114534657A).

[0010] The molar ratio of butadiene to hydrocyanic acid is (1.5-4):1.

[0011] Preferably, the molar ratio of butadiene to hydrocyanic acid is (1.5-3):1.

[0012] More preferably, the molar ratio of butadiene to hydrocyanic acid is (2-3):1.

[0013] More preferably, the molar ratio of butadiene to hydrocyanic acid is 3:1.

[0014] The catalytic system comprises a nickel catalyst, a Lewis acid and a phosphorus ligand, wherein the molar ratio of the nickel catalyst, the Lewis acid and the phosphorus ligand is 1:(3-6):(6-12).

[0015] Preferably, the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:(4-5):(7-10).

[0016] Further preferably, the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:(8-10).

[0017] More preferably, the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:10.

[0018] The preheating temperature is 50-70°C.

[0019] Preferably, the preheating temperature is 50-60°C.

[0020] More preferably, the preheating temperature is 60°C.

[0021] The applicant has found that by preheating the raw materials and the catalytic system and mixing them separately, the raw materials and the catalytic system can be prevented from contacting in advance, while increasing the mixing time of the raw materials in the microchannel reactor and improving the reaction rate. Further research has found that the molar ratio of butadiene to hydrocyanic acid is (1.5-4):1, and the microchannel reactor is used to increase the conversion rate to more than 80%, which may be due to the increase in the contact area between the raw materials while maintaining a high heat transfer efficiency, so that the reaction proceeds at a high speed and smoothly.

[0022] The Lewis acid includes at least one of zinc chloride, aluminum chloride, ferric chloride and aluminum chloride.

[0023] Preferably, the Lewis acid comprises zinc chloride.

[0024] The phosphorus ligand includes at least one of triphenyl phosphite, tri-o-cresyl phosphite, tri-m-cresyl phosphite or tri-p-cresyl phosphite.

[0025] Preferably, the phosphorus ligand comprises triphenyl phosphite.

[0026] The temperature of the microchannel reaction is 80-110° C., the pressure is 0.5-1.5 MPa, and the reaction time is 10-40 min.

[0027] Preferably, the temperature of the microchannel reaction is 80-100° C., the pressure is 1-1.5 MPa, and the time is 10-30 min.

[0028] Further preferably, the temperature of the microchannel reaction is 90° C., the pressure is 1 MPa, and the time is 25 min.

[0029] The distillation specifically comprises: passing the crude product into a dividing wall tower, condensing the butadiene product at the top of the dividing wall tower through a condenser and then circulating to participate in the reaction, obtaining by-products at the side of the dividing wall tower, and obtaining adiponitrile at the bottom of the dividing wall tower.

[0030] The pressure in the dividing wall tower is 1-2 MPa.

[0031] Preferably, the pressure in the dividing wall tower is 1-1.5 MPa.

[0032] Further preferably, the pressure in the dividing wall tower is 1.5 MPa.

[0033] The distillation specifically comprises: passing the crude product into a first distillation tower, condensing butadiene obtained at the top of the first distillation tower through a condenser and then circulating to participate in the reaction, obtaining adiponitrile and by-products at the bottom of the first distillation tower; passing the bottom product of the first distillation tower into a second distillation tower, and obtaining adiponitrile at the bottom of the second distillation tower.

[0034] The temperature of the second distillation tower is 260-290° C., and the pressure is 0.5-1.5 MPa.

[0035] Preferably, the temperature of the second distillation tower is 270-280°C and the pressure is 0.8-1.2 MPa.

[0036] Further preferably, the temperature of the second distillation tower is 275° C. and the pressure is 1 MPa.

[0037] Beneficial Effects

[0038] 1. By preheating the raw materials and the catalyst system and then mixing them separately, it is possible to avoid premature contact between the raw materials and the catalyst system, while increasing the mixing time of the raw materials in the microchannel reactor and improving the reaction rate.

[0039] 2. By limiting the molar ratio of butadiene to hydrocyanic acid to (1.5-4):1 and using a microchannel reactor, the conversion rate of adiponitrile can be increased to more than 80%.

[0040] 3. The catalytic system includes a nickel catalyst, a Lewis acid and a phosphorus ligand, wherein the molar ratio of the nickel catalyst, the Lewis acid and the phosphorus ligand is 1:(3-6):(6-12), which can increase the selectivity of adiponitrile to more than 70%.

[0041] 4. The purpose of simplifying the process, reducing costs and saving energy consumption is achieved by replacing multi-tower distillation products with a dividing wall tower, while making the purity of adiponitrile greater than 99%.

[0042] 5. The company's proprietary microchannel reactor is used to achieve rapid and efficient reaction after the raw materials are completely mixed within the millisecond range, with short reaction time, high conversion rate, safe reaction and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a diagram of the reaction apparatus of Examples 1-4.

[0044] Figure 2 This is a diagram of the reaction apparatus of Examples 5-8.

[0045] Among them, E-1, E-2, and E-3 are heaters; M-1 and M-2 are mixers; R-1 is a microchannel reactor; T-1 is a dividing wall tower; T-2 is the first distillation tower; T-3 is the second distillation tower; E-4 and E-5 are condensers; and P-1 is a pump. DETAILED DESCRIPTION

[0046] Example 1

[0047] A method for synthesizing adiponitrile from butadiene in one step, such as Figure 1 As shown, the following steps are:

[0048] Butadiene and hydrocyanic acid are introduced into heaters E-1 and E-2 at a molar ratio of 1.5:1, respectively, and heated to 60° C., and then preliminarily mixed in a mixer M-1 to obtain a first mixture, and the raw materials at the outlet of the mixer are sampled for detection. No methylglutaronitrile and 2-methyl-3-butenenitrile impurities are detected by gas chromatography (due to the absence of a catalyst, almost no impurities are generated by the reaction, or the content of the generated impurities is extremely low and cannot be detected);

[0049] The nickel catalyst: zinc chloride: triphenyl phosphite in a molar ratio of 0.5:2:5 is introduced into the heater E-3 and heated to 60° C. to obtain a second mixture;

[0050] The two mixtures were simultaneously introduced into a microchannel reactor for reaction at a temperature of 90°C, a reaction time of 10 min, and a pressure of 0.5 MPa. After the reaction, the reaction liquid was passed into the next-door tower at a pressure of 1.5 MPa. The butadiene at the top of the tower was condensed in a condenser and then recycled to participate in the reaction. Methylglutaronitrile was produced as a by-product on the side of the tower, and adiponitrile product was obtained at the bottom of the tower.

[0051] Example 2

[0052] The specific implementation is the same as Example 1; the difference is that in Example 2, the molar ratio of butadiene to hydrocyanic acid is 2:1; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:4:7.

[0053] Example 3

[0054] The specific implementation is the same as that of Example 1; the difference is that in Example 3, the molar ratio of butadiene to hydrocyanic acid is 3:1; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:8.

[0055] Example 4

[0056] The specific implementation is the same as Example 1; the difference is that in Example 4, the molar ratio of butadiene to hydrocyanic acid is 3:1; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:10.

[0057] Example 5

[0058] A method for synthesizing adiponitrile from butadiene in one step, such as Figure 2 As shown, the following steps are:

[0059] Butadiene and hydrocyanic acid are introduced into heaters E-1 and E-2 at a molar ratio of 1.5:1, respectively, and heated to 60° C., and then preliminarily mixed in a mixer M-1 to obtain a first mixture, and the raw materials at the outlet of the mixer are sampled for detection. No methylglutaronitrile and 2-methyl-3-butenenitrile impurities are detected by gas chromatography (due to the absence of a catalyst, almost no impurities are generated by the reaction, or the content of the generated impurities is extremely low and cannot be detected);

[0060] The nickel catalyst: zinc chloride: triphenyl phosphite in a molar ratio of 0.5:2:5 is introduced into the heater E-3 and heated to 60° C. to obtain a second mixture;

[0061] The two mixtures were simultaneously pumped into a microchannel reactor for reaction at a temperature of 90°C, a reaction time of 10 min, and a pressure of 0.5 MPa. After the reaction, the reaction liquid was passed into the first distillation tower at a pressure of 1.5 MPa. The butadiene at the top of the tower was condensed by a condenser and then recycled to participate in the reaction. The bottom of the tower contained adiponitrile and by-product methylglutaronitrile and was pumped into the product distillation tower through a pump. Adiponitrile distillation separation: the adiponitrile and methylglutaronitrile were pumped into the second distillation tower at a temperature of 275°C and a pressure of 1 MPa. The adiponitrile product was obtained at the bottom of the tower, and the by-product methylglutaronitrile and 2-methyl-3-butenenitrile were obtained through condensation at the top of the tower.

[0062] Example 6

[0063] The specific implementation is the same as that of Example 5; the difference is that in Example 6, the molar ratio of butadiene to hydrocyanic acid is 2:1; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:4:7.

[0064] Example 7

[0065] The specific implementation is the same as that of Example 5; the difference is that in Example 7, the molar ratio of butadiene to hydrocyanic acid is 3:1.5; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:8.

[0066] Example 8

[0067] The specific implementation is the same as that of Example 5; the difference is that in Example 8, the molar ratio of butadiene to hydrocyanic acid is 3:1; and the molar ratio of the nickel catalyst, Lewis acid and phosphorus ligand is 1:5:10.

[0068] Comparative Example 1

[0069] Butadiene and hydrocyanic acid were introduced into a heater at a molar ratio of 3:1, and nickel catalyst: zinc chloride: triphenyl phosphite were introduced at a molar ratio of 1:5:10 to heat to 60°C. Samples were taken before entering the microchannel reactor, and impurity detection was performed by gas chromatography, wherein the content of methylglutaronitrile was 0.78wt%, and the content of 2-methyl-3-butenenitrile was 0.41wt%. Then the mixture was introduced into the microchannel reactor for reaction at a temperature of 90°C, a reaction time of 25min, and a pressure of 1MPa. After the reaction, the reaction liquid was introduced into a bulkhead tower at a pressure of 1.5MPa. The butadiene at the top of the tower was condensed by a condenser and then recycled to participate in the reaction. Methylglutaronitrile was produced as a byproduct on the side of the tower, and adiponitrile product was obtained at the bottom of the tower.

[0070] Performance Testing Methods

[0071] The purity (HPLC), conversion rate and selectivity performance tests were carried out in the embodiments and comparative examples, and the test data are listed in Table 1.

[0072] Performance test data

[0073] Table 1

[0074]

[0075]

[0076] It can be verified through Comparative Example 1 that it is precisely because of the independent heating of the catalyst and the raw materials that the generation of impurities in non-reactors can be reduced, thereby greatly improving the purity and yield.

Claims

1. A method for synthesizing adiponitrile from butadiene in one step, characterized in that: The following steps are involved: Preheating butadiene, hydrocyanic acid and the catalyst system respectively; Preliminarily mixing the preheated butadiene and hydrocyanic acid to form a first mixture; The preheated catalyst system is mixed uniformly to form a second mixture. The first mixture and the second mixture are subjected to microchannel reaction to obtain a crude product, which is then separated by distillation to obtain the product.

2. The method for synthesizing adiponitrile from butadiene in one step according to claim 1, characterized in that: The molar ratio of butadiene to hydrocyanic acid is (1.5-4):

1.

3. The method for synthesizing adiponitrile from butadiene in one step according to claim 2, characterized in that: The catalytic system comprises a nickel catalyst, a Lewis acid and a phosphorus ligand, wherein the molar ratio of the nickel catalyst, the Lewis acid and the phosphorus ligand is 1:(3-6):(6-12).

4. The method for synthesizing adiponitrile from butadiene in one step according to claim 1 or 3, characterized in that: The preheating temperature is 50-70°C.

5. The method for synthesizing adiponitrile from butadiene in one step according to claim 4, characterized in that: The Lewis acid includes at least one of zinc chloride, aluminum chloride, ferric chloride and aluminum chloride.

6. The method for synthesizing adiponitrile from butadiene in one step according to claim 5, characterized in that: The phosphorus ligand includes at least one of triphenyl phosphite, tri-o-cresyl phosphite, tri-m-cresyl phosphite or tri-p-cresyl phosphite.

7. The method for synthesizing adiponitrile from butadiene in one step according to claim 1 or 6, characterized in that: The temperature of the microchannel reaction is 80-110° C., the pressure is 0.5-1.5 MPa, and the reaction time is 10-40 min.

8. The method for synthesizing adiponitrile from butadiene in one step according to claim 7, characterized in that: The distillation specifically comprises: passing the crude product into a dividing wall tower, condensing the butadiene product at the top of the dividing wall tower through a condenser and then circulating to participate in the reaction, obtaining by-products at the side of the dividing wall tower, and obtaining adiponitrile at the bottom of the dividing wall tower.

9. The method for synthesizing adiponitrile from butadiene in one step according to claim 8, characterized in that: The pressure in the dividing wall tower is 1-2 MPa.

10. The method for synthesizing adiponitrile from butadiene in one step according to claim 7, characterized in that: The distillation specifically comprises: passing the crude product into a first distillation tower, condensing butadiene obtained at the top of the first distillation tower through a condenser and then circulating to participate in the reaction, obtaining adiponitrile and by-products at the bottom of the first distillation tower; passing the bottom product of the first distillation tower into a second distillation tower, and obtaining adiponitrile at the bottom of the second distillation tower.

Images