A process for co-producing p-phenylenediamine and isopropanol

Abstract

The present invention relates to a process for the co-production of p-phenylenediamine and isopropanol, wherein p-nitroaniline and acetone are used as raw materials, water is used as a supplementary solvent, a tubular reactor is used, a Ni-based catalyst is used for reduction reaction, and the products are separated by azeotropic distillation and recrystallization to obtain p-nitroaniline and isopropanol that meet the purity standard. The technical scheme adopts a tubular process for the co-production of p-nitroaniline and isopropanol by hydrogen reduction of p-nitroaniline and acetone under the action of a catalyst, and the process can reduce the amount of solvent used, while improving the utilization rate of the device and the economic value of the product; the process can achieve a p-nitroaniline conversion rate of ≥95.0%, a p-phenylenediamine selectivity of ≥98.0%, an acetone conversion rate of ≥95.0%, and an isopropanol selectivity of ≥99.9%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis technology, and specifically relates to a process for co-producing p-phenylenediamine and isopropanol, and more specifically to a process for co-producing p-phenylenediamine and isopropanol by reducing p-nitroaniline and acetone with hydrogen under the action of a catalyst. Background Art

[0002] Paraphenylenediamine is one of the simplest aromatic diamines and an important chemical intermediate. It is mainly used in dyes, antioxidants for natural rubber and diene synthetic rubber, inhibitors, coupling agents in color photography and hair dyes. It can also be used as a raw material for aramid fibers.

[0003] There are many methods for synthesizing p-phenylenediamine, among which the most common method is to synthesize p-phenylenediamine by hydrogen catalytic reduction using p-nitroaniline as raw material. There are four processes reported for this method, namely, continuous process, batch process, fixed bed process and tubular process. Since both the raw material p-nitroaniline and the product p-phenylenediamine are solid at room temperature, the process of synthesizing p-phenylenediamine by hydrogenation of p-nitroaniline requires the use of solvents. Since the solubility of the same solvent in p-nitroaniline and p-phenylenediamine is quite different, a large amount of solvent is used in the process, resulting in low production efficiency of the device and high product separation cost. Summary of the invention

[0004] The object of the present invention is to provide a process for co-producing p-phenylenediamine and isopropanol, so as to solve the problems that in the existing process, both the raw material p-nitroaniline and the product p-phenylenediamine are solid at room temperature, and the process of synthesizing p-phenylenediamine by hydrogenation of p-nitroaniline requires the use of a solvent. Since the solubility of the same solvent to p-nitroaniline and p-phenylenediamine is quite different, the amount of solvent used in the process is large, resulting in low production efficiency of the device and high product separation cost.

[0005] To achieve the above objectives, this application is implemented through the following technical solutions:

[0006] A process for co-producing p-phenylenediamine and isopropanol comprises the following steps:

[0007] S1. Mixing raw materials of a set mass ratio: p-nitroaniline, acetone and water, and mixing with hydrogen of a set pressure to obtain a raw material mixture, and heating the raw material mixture to a set temperature;

[0008] S2, the raw material mixture heated to the set temperature enters from the feed port of the tubular reactor and undergoes a reduction reaction under the action of the catalyst;

[0009] S3, after the reaction product is discharged from the discharge port of the tubular reactor, gas-liquid separation is performed, the separated hydrogen is reused as circulating hydrogen, and the liquid part after gas-liquid separation enters the acetone distillation tower;

[0010] S4, the acetone separated from the top of the acetone distillation tower is returned to the raw material mixing place of step S1; the bottom discharge of the acetone distillation tower enters the azeotropic distillation tower;

[0011] S5. The top product of the azeotropic distillation tower enters the isopropanol-water separation unit to separate water and isopropanol products; the bottom product of the azeotropic distillation tower enters the recrystallization unit to separate water, p-nitroaniline and p-phenylenediamine.

[0012] Furthermore, in step S1, the mass ratio of p-nitroaniline to acetone is 1:1-1:10, and the mass ratio of water to acetone is 1:10-1:2.

[0013] Furthermore, the mass ratio of p-nitroaniline to acetone is 1:1-1:5, and the mass ratio of water to acetone is 1:5-1:2.

[0014] Furthermore, the volume ratio of hydrogen to liquid raw material in step S1 is 300:1-1000:1.

[0015] Furthermore, the volume ratio of hydrogen to liquid raw material in step S1 is 400:1-600:1.

[0016] Furthermore, the operating conditions of the shell-and-tube reactor in step S2 are: reaction temperature 60-180°C, pressure 0.5-3.0 MPa, volume space velocity 0.5 h -1 -2.0h -1 .

[0017] Furthermore, the operating conditions of the shell-and-tube reactor in step S2 are: reaction temperature 60-100°C, pressure 1.0-1.8 MPa, volume space velocity 1.0 h -1 -2.0h -1 .

[0018] Furthermore, the catalyst in step S2 is a Ni-based catalyst, the weight percentage of Ni in the catalyst is 15%-40%, and the rest is Al2O3.

[0019] Furthermore, the weight percentage of Ni in the catalyst is 25%-40%, and the rest is Al2O3.

[0020] Furthermore, more than 95% of the Ni content in the catalyst is reduced Ni.

[0021] The beneficial effects of the present invention are:

[0022] 1. Through the above technical scheme, the co-production of p-phenylenediamine and isopropanol can be achieved. The process can achieve a p-nitroaniline conversion rate ≥ 95.0%, a p-phenylenediamine selectivity ≥ 98.0%, an acetone conversion rate ≥ 95.0%, and an isopropanol selectivity ≥ 99.9%.

[0023] 2. A shell-and-tube process is adopted in which p-nitroaniline and acetone are reduced with hydrogen in the presence of a catalyst to produce p-phenylenediamine and isopropanol. This process can reduce the amount of solvent used and improve the utilization rate of the device and the economic value of the product. Experimental verification shows that acetone has a high solubility in p-nitroaniline, but acetone and isopropanol have a low solubility in p-phenylenediamine. The main functions of using water as a solvent are: first, to promote the dissolution of p-phenylenediamine and ensure the operation of the shell-and-tube reactor; second, to reduce the heat of reaction; and third, to inhibit the production of acetone hydrogenation by-products. At the same time, in the product separation process, water and isopropanol co-azeotropy reduce the separation temperature of isopropanol and p-phenylenediamine. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of the process for co-producing p-phenylenediamine and isopropanol. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solution of the present invention, but cannot be construed as limiting the technical solution of the present invention.

[0026] like Figure 1 As shown, the technical solution of the present application is to use p-nitroaniline and acetone as raw materials, water as solvent, hydrogen as reducing agent, adopt a shell-and-tube reactor, and a Ni-based catalyst to carry out a reduction reaction, and the products are separated by distillation, azeotropic distillation, and recrystallization to obtain p-nitroaniline and isopropanol that meet the purity standards.

[0027] In the above process, the specific conditions are as follows:

[0028] (1) The mass ratio of the raw material p-nitroaniline to acetone is 1:1-1:10, more preferably 1:1-1:5.

[0029] (2) Water is used as a solvent, and the mass ratio of water to acetone is 1:10-1:2, preferably 1:5-1:2.

[0030] (3) The Ni content of the Ni-based catalyst used is 15%-40%, more preferably 25%-40%; the rest is Al2O3; the catalyst is prepared by coprecipitation tableting, kneading or impregnation; the catalyst is granular or cylindrical, with a particle size of 6-12 mesh, an average strength of ≥50N / particle, and a specific surface area of ​​≥80m 2 / g; more than 95% of the Ni content in the catalyst exists in the reduced state.

[0031] (4) The reaction temperature of the hydrogenation part is 60-180°C, the pressure is 0.5-3.0MPa, and the volume space velocity is 0.5h -1 -2.0h -1The volume ratio of hydrogen to liquid feed is 300:1-1000:1; the more preferred reaction temperature is 60-100°C, the pressure is 1.0-1.8MPa, and the volume space velocity is 1.0h -1 -2.0h -1 , the volume ratio of hydrogen to liquid feed is 400:1-600:1.

[0032] (5) After heat exchange, the reaction distillate enters the acetone distillation tower, acetone is distilled from the top of the tower, and returns to the reaction system after heat exchange, and the bottom distillate enters the azeotropic distillation tower; the azeotrope of water and isopropanol is distilled from the top of the azeotropic distillation tower, and after passing through the cold zone, water and isopropanol are separated by the common industrial method. The separated isopropanol is sent to the tank area as a product, and water is reused as a diluent; the bottom component of the azeotropic distillation tower is separated into p-phenylenediamine and p-nitroaniline by the common industrial recrystallization method, p-nitroaniline is dissolved in acetone and returned to the reaction system as a raw material, and p-phenylenediamine is packaged as a product and sent to the warehouse.

[0033] Examples 1-5

[0034] The p-nitroaniline is dissolved in acetone, the mass ratio of p-nitroaniline to acetone is 1:1, water is used as solvent, the mass ratio of water to acetone is 1:10, hydrogen is used as reducing agent, and a tubular reactor is used. The Ni-based catalyst prepared by impregnation method with Ni content of 15% is used. The reaction distillates are p-phenylenediamine, isopropanol, water, and incompletely reacted p-phenylenediamine and acetone. The reaction products are separated by distillation, azeotropic distillation, and recrystallization to obtain p-nitroaniline and isopropanol that meet the purity standard. The p-nitroaniline conversion rate, p-phenylenediamine selectivity, acetone conversion rate, and isopropanol selectivity under different reaction conditions are shown in Table 1.

[0035] Table 1 Example 1-5 p-nitroaniline conversion, p-phenylenediamine selectivity, acetone conversion, isopropanol selectivity

[0036] Example Example 1 Example 2 Example 3 Example 4 Example 5 Reaction temperature, °C 100 100 140 180 180 Reaction pressure, MPa 2.0 3.0 1.0 0.5 1.5 <![CDATA[Feed volume space velocity, h -1 > 1.0 0.5 1.5 1.5 2.0 Hydrogen to feed volume ratio 400:1 600:1 800:1 800:1 1000:1 p-Nitroaniline conversion rate, % 95.3 96.6 97.4 97.6 98.4 Selectivity to p-phenylenediamine, % 99.6 99.2 99.3 98.6 98.1 Acetone conversion, % 95.2 97.7 99.4 99.7 100.0 Isopropanol selectivity, % 100.0 100.0 100.0 99.9 99.9

[0037] Examples 6-10

[0038] The p-nitroaniline is dissolved in acetone, the mass ratio of p-nitroaniline to acetone is 1:5, water is used as solvent, the mass ratio of water to acetone is 1:5, hydrogen is used as reducing agent, and a tubular reactor is used. The Ni-based catalyst is prepared by a kneading method with a Ni content of 25%. The reaction distillates are p-phenylenediamine, isopropanol, water, and incompletely reacted p-phenylenediamine and acetone. The reaction products are separated by distillation, azeotropic distillation, and recrystallization to obtain p-nitroaniline and isopropanol that meet the purity standards. The p-nitroaniline conversion rate, p-phenylenediamine selectivity, acetone conversion rate, and isopropanol selectivity under different reaction conditions are shown in Table 4.

[0039] Table 2 p-nitroaniline conversion, p-phenylenediamine selectivity, acetone conversion, isopropanol selectivity of Examples 6-10

[0040] Example Example 6 Example 7 Example 8 Example 9 Example 10 Reaction temperature, °C 80 100 120 140 180 Reaction pressure, MPa 2.5 2.0 1.8 1.5 1.5 <![CDATA[Feed volume space velocity, h -1 > 1.0 1.0 0.5 1.5 2.0 Hydrogen to feed volume ratio 600:1 400:1 600:1 800:1 1000:1 p-Nitroaniline conversion rate, % 96.4 98.5 99.3 99.7 99.9 Selectivity to p-phenylenediamine, % 99.3 99.6 99.5 98.6 98.1 Acetone conversion, % 98.3 98.7 99.9 99.8 99.7 Isopropanol selectivity, % 99.9 100.0 99.9 100.0 99.9

[0041] Examples 11-15

[0042] The p-nitroaniline was dissolved in acetone, the mass ratio of p-nitroaniline to acetone was 1:2, water was used as solvent, the mass ratio of water to acetone was 1:3, hydrogen was used as reducing agent, and a tubular reactor was used. The Ni-based catalyst was prepared by kneading method with Ni content of 30%. The reaction distillates were p-phenylenediamine, isopropanol, water, and incompletely reacted p-phenylenediamine and acetone. The reaction products were separated by distillation, azeotropic distillation, and recrystallization to obtain p-nitroaniline and isopropanol that met the purity standard. The p-nitroaniline conversion rate, p-phenylenediamine selectivity, acetone conversion rate, and isopropanol selectivity under different reaction conditions are shown in Table 3.

[0043] Table 3 Conversion rate of p-nitroaniline, selectivity of p-phenylenediamine, conversion rate of acetone, selectivity of isopropanol in Examples 11-15

[0044]

[0045]

[0046] Examples 16-20

[0047] The p-nitroaniline was dissolved in acetone, the mass ratio of p-nitroaniline to acetone was 1:10, water was used as solvent, the mass ratio of water to acetone was 1:2, hydrogen was used as reducing agent, and a tubular reactor was used. The Ni-based catalyst was prepared by coprecipitation tableting method with Ni content of 40%. The reaction distillate was p-phenylenediamine, isopropanol, water, and incompletely reacted p-phenylenediamine and acetone. The reaction products were separated by distillation, azeotropic distillation, and recrystallization to obtain p-nitroaniline and isopropanol that met the purity standard. The p-nitroaniline conversion rate, p-phenylenediamine selectivity, acetone conversion rate, and isopropanol selectivity under different reaction conditions are shown in Table 4.

[0048] Table 4 p-nitroaniline conversion, p-phenylenediamine selectivity, acetone conversion, isopropanol selectivity of Examples 6-10

[0049]

[0050] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A process for the co-production of p-phenylenediamine and isopropanol, characterized in that: The following steps are involved: S1. Mixing raw materials of a set mass ratio: p-nitroaniline, acetone and water, and mixing with hydrogen of a set pressure to obtain a raw material mixture, and heating the raw material mixture to a set temperature; S2, the raw material mixture heated to the set temperature enters from the feed port of the tubular reactor and undergoes a reduction reaction under the action of the catalyst; S3, after the reaction product is discharged from the discharge port of the tubular reactor, gas-liquid separation is performed, the separated hydrogen is reused as circulating hydrogen, and the liquid part after gas-liquid separation enters the acetone distillation tower; S4, the acetone separated from the top of the acetone distillation tower is returned to the raw material mixing place of step S1; the bottom discharge of the acetone distillation tower enters the azeotropic distillation tower; S5, the top product of the azeotropic distillation tower enters the isopropanol-water separation unit to separate water and isopropanol products; the bottom product of the azeotropic distillation tower enters the recrystallization unit to separate water, p-nitroaniline and p-phenylenediamine; In step S1, the mass ratio of p-nitroaniline to acetone is 1:1-1:10, and the mass ratio of water to acetone is 1:10-1:2; The catalyst in step S2 is a Ni-based catalyst, the weight percentage of Ni in the catalyst is 15%-40%, and the rest is Al2O3.

2. The process for co-production of p-phenylenediamine and isopropanol according to claim 1, characterized in that: In step S1, the mass ratio of p-nitroaniline to acetone is 1:1-1:5, and the mass ratio of water to acetone is 1:5-1:

2.

3. The process for co-production of p-phenylenediamine and isopropanol according to claim 1, characterized in that: The volume ratio of hydrogen to liquid raw material in step S1 is 300:1-1000:

1.

4. The process for co-production of p-phenylenediamine and isopropanol according to claim 3, characterized in that: The volume ratio of hydrogen to liquid raw material in step S1 is 400:1-600:

1.

5. The process for co-production of p-phenylenediamine and isopropanol according to claim 1, characterized in that: The operating conditions of the tubular reactor in step S2 are: reaction temperature 60-180°C, pressure 0.5-3.0 MPa, volume space velocity 0.5 h -1 -2.0h -1 .

6. The process for co-production of p-phenylenediamine and isopropanol according to claim 5, characterized in that: The operating conditions of the tubular reactor in step S2 are: reaction temperature 60-100°C, pressure 1.0-1.8 MPa, volume space velocity 1.0 h -1 -2.0h -1 .

7. The process for co-production of p-phenylenediamine and isopropanol according to claim 1, characterized in that: The weight percentage of Ni in the catalyst is 25%-40%, and the rest is Al2O3.

8. The process for co-production of p-phenylenediamine and isopropanol according to claim 1, characterized in that: More than 95% of the Ni content in the catalyst is reduced Ni.

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