Method for improving aniline conversion rate in diphenylamine synthesis process

Abstract

The invention discloses a method for improving aniline conversion rate in a diphenylamine synthesis process. The method comprises the following steps: reacting aniline and propylene which are used as raw materials in a fixed bed reactor containing an H beta zeolite catalyst under certain reaction conditions. The propylene gas is introduced into the reaction system, so that the conversion rate of aniline in the diphenylamine synthesis process is effectively improved, isopropylamine is generated in the product, and the economical efficiency of the product is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemical industry, and particularly relates to a method for improving the conversion rate of aniline in the process of synthesizing diphenylamine from aniline. Background Art

[0002] Diphenylamine is a chemical product with a very wide range of uses and has important applications in the fields of rubber auxiliaries, dyes, explosive stabilizers, fruit preservatives, medicines, etc. Up to now, there are about more than 20 methods for synthesizing diphenylamine, and the production raw materials include aniline, phenol, cyclohexanone, N-cyclohexylaniline, dicyclohexyl, etc. The catalysts mainly include aluminum trichloride, boron trifluoride, activated alumina, zeolite molecular sieve, etc. Among these methods, the method of using single aniline as the raw material to produce diphenylamine has the best atom economy and the strongest feasibility for large-scale production, and has been industrialized. The production process of synthesizing diphenylamine from aniline is divided into batch method, gas-phase continuous method and liquid-phase continuous method, among which the liquid-phase continuous method is the most advanced production process at present. However, the conversion rate of aniline in the above production process is relatively low, which seriously restricts the production efficiency of the process of synthesizing diphenylamine from aniline, and this is also the main problem faced in the current industrial production of diphenylamine.

[0003] CN1186802A reports a process for the continuous synthesis of diphenylamine from aniline in the presence of hydrogen. This process uses the raw material refining gas (about 75% hydrogen and 25% nitrogen) of the ammonia synthesis unit as the hydrogen source in the presence of hydrogen, and forms a gas-phase circulation system between the diphenylamine unit and the ammonia synthesis compression section. The advantage of this process is that on the basis of making full use of hydrogen resources, it effectively improves the conversion rate of aniline in the diphenylamine production process and prolongs the service life of the catalyst. Although this effect in the presence of hydrogen is relatively obvious, the conversion rate of aniline still cannot exceed 30%.

[0004] CN103044270A also reports a process for the continuous synthesis of diphenylamine from aniline in the presence of hydrogen, aiming to improve the conversion rate of aniline by developing a hydrogen dissolution process. This process focuses on the contact between the aniline raw material and hydrogen before entering the reactor, so that hydrogen dissolves into the aniline raw material. The aniline raw material dissolved with hydrogen enters the reactor for the continuous synthesis of diphenylamine from aniline to carry out the reaction of synthesizing diphenylamine from aniline. The advantage of this method is to improve the efficiency of synthesizing diphenylamine from aniline by dissolving hydrogen. However, the conversion rate of aniline cannot be effectively improved by dissolving hydrogen.

[0005] The research results of the above two methods show that although introducing hydrogen into the system can improve the conversion rate of aniline in the process of the liquid-phase continuous synthesis of diphenylamine from aniline to a certain extent, the improvement effect is limited, and new processes still need to be developed to effectively improve the conversion rate of aniline. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for improving the conversion rate of aniline in the diphenylamine synthesis process. By introducing propylene gas into the reaction system, the present invention effectively improves the conversion rate of aniline in the diphenylamine synthesis process, and isopropylamine is generated in the product, further improving the economy of the product.

[0007] A method for improving the conversion rate of aniline in the diphenylamine synthesis process according to the present invention includes the following: Raw material aniline and propylene together, at a reaction temperature of 130°C to 220°C, and a liquid hourly space velocity of aniline of 0.01 h -1 ~1.0 h -1 Under the conditions, pass through a fixed-bed reactor containing an Hβ zeolite catalyst.

[0008] Furthermore, the reaction conditions for synthesizing diphenylamine from aniline in the present invention are different from those of the conventional liquid-phase method for synthesizing diphenylamine from aniline, mainly reflected in the lower reaction temperature. Among them, the reaction conditions also include: the reaction pressure is 1.0 MPa to 10.0 MPa, and the gas-liquid molar ratio of propylene to aniline is 1:(1 to 5).

[0009] Furthermore, the catalyst for synthesizing diphenylamine from aniline uses a solid catalyst with Hβ zeolite as the active component. The catalyst containing Hβ zeolite can be either a commercially available product in the art or prepared according to the prior art methods, such as the method disclosed in CN200510047489.9.

[0010] Furthermore, a typical Hβ zeolite catalyst includes 50 w% to 90 w% of Hβ zeolite, 0.1 w% to 40 w% of alkali metal, and 0.5 w% to 49.9 w% of γ-Al 2 O 3 Among them, the SiO 2 / Al 2 O 3 molecular ratio of the Hβ zeolite is 20 to 100, and the alkali metal is one or more of lithium, sodium, and potassium metals.

[0011] Furthermore, a typical preparation method of the catalyst containing Hβ zeolite includes: soaking Hβ zeolite in an aqueous solution of alkali metal with a concentration of 0.05 mol / L to 4 mol / L, filtering, washing, drying, mixing with aluminum hydroxide, and adding nitric acid and deionized water for kneading, forming, drying, and calcining to obtain the catalyst used in the present invention.

[0012] Furthermore, the reaction temperature is preferably 150°C to 200°C.

[0013] Furthermore, the reaction pressure is preferably 3.0 MPa to 5.0 MPa.

[0014] Further, the volumetric space velocity of the aniline solution is preferably 0.05 h -1 ~0.5 h -1 .

[0015] Further, the gas-liquid molar ratio of propylene to aniline is preferably 1:(1.5 - 3).

[0016] Further, propylene and aniline can flow downward in parallel through a fixed-bed reactor containing an Hβ zeolite catalyst; or, propylene and aniline can flow upward in parallel through a fixed-bed reactor containing an Hβ zeolite catalyst; or, aniline flows downward and propylene flows upward in a gas-liquid countercurrent manner through a fixed-bed reactor containing an Hβ zeolite catalyst.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The method of the present invention provides a method for improving the conversion rate of aniline in the diphenylamine synthesis process. Compared with the existing hydrogenation process, by introducing propylene gas into the reaction system in the present invention, the conversion rate of the raw material aniline can reach more than 35%, and the selectivity of diphenylamine is ≮96%.

[0018] 2. While effectively improving the conversion rate of aniline, the method of the present invention can also highly utilize the by-product ammonia to obtain high-value isopropylamine, thereby further improving the overall economy of the diphenylamine device. Embodiment

[0019] The method of the present invention will be described in more detail below in conjunction with specific embodiments.

[0020] The catalysts used in the examples and comparative examples are fixed-bed catalysts containing Hβ zeolite (FD-20 catalyst developed by Sinopec (Dalian) Research Institute of Petroleum and Chemical Industry); the diameter of the catalyst is φ 2 mm strip, and the length is 2 - 3 mm.

[0021] The reactor used in the examples is a stainless steel reactor with an inner diameter of 25 mm and a length of 1200 mm. The purity of the reaction raw material propylene > 99%. The reaction products can be analyzed with reference to the standard HG / T5534-2019. The specific reaction conditions and results are listed in Table 1.

[0022] Among them, the calculation formulas for the conversion rate of aniline, the selectivity of diphenylamine, and the selectivity of isopropylamine are as follows: Molar conversion rate of aniline:

[0023] ω : Molar conversion rate of aniline, mol%; n 1 : Molar number of each product component in the reaction solution, mol; n 2 : Moles of aniline in the reaction solution, mol.

[0024] Mole selectivity of diphenylamine:

[0025] ε 1 : Mole selectivity of diphenylamine, mol%; n 1 : Moles of each product component in the reaction solution, mol; n 3 : Moles of diphenylamine in the reaction solution, mol.

[0026] Mole selectivity of isopropylamine:

[0027] ε 2 : Mole selectivity of isopropylamine, mol%; n 1 : Moles of each product component in the reaction solution, mol; n 4 : Moles of isopropylamine in the reaction solution, mol. Example 1

[0028] In a stainless steel fixed-bed reactor with an inner diameter of 25 mm and a length of 1200 mm, 100 mL of FD-20 molecular sieve catalyst was loaded. Under certain process conditions, the reaction raw materials aniline and propylene (purity > 99%) were fed into the reactor in a downward feeding manner. After the reaction products came out from the top of the reactor, they were cooled and then entered the separator. The composition of the reaction products was analyzed by gas chromatography. The specific reaction conditions and results are listed in Table 1. Example 2

[0029] The specific operation process was the same as that of Example 1, where the reaction temperature, pressure, volume space velocity, and gas-liquid molar ratio were different from those of Example 1. The composition of the reaction products was analyzed by gas chromatography. The specific reaction conditions and results are listed in Table 1. Example 3

[0030] The specific operation process was the same as that of Example 1, where the reaction temperature, pressure, volume space velocity, and gas-liquid molar ratio were different from those of Example 1. The composition of the products was analyzed by gas chromatography. The specific reaction conditions and results are listed in Table 1. Example 4

[0031] The specific operation process is the same as that of Example 1, where the reaction temperature, pressure, volume space velocity, and gas-liquid molar ratio are different from those of Example 1. The composition of the product is analyzed by gas chromatography, and the specific reaction conditions and results are listed in Table 1.

[0032] Comparative Example 1 The specific operation process is the same as that of Example 1, where the reaction raw materials are aniline and hydrogen (purity > 99%). The composition of the product is analyzed by gas chromatography, and the specific reaction conditions and results are listed in Table 1.

[0033] Comparative Example 2 The specific operation process is the same as that of Example 1. The composition of the product is analyzed by gas chromatography, and the specific reaction conditions and results are listed in Table 1.

[0034] Comparative Example 3 The specific operation process is the same as that of Example 1. The composition of the product is analyzed by gas chromatography, and the specific reaction conditions and results are listed in Table 1.

[0035] Comparative Example 4 The specific operation process is the same as that of Example 1. The composition of the product is analyzed by gas chromatography, and the specific reaction conditions and results are listed in Table 1.

[0036] Table 1 Project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Reaction temperature, °C 150 150 200 200 150 120 240 200 Reaction pressure, MPa 3.0 3.5 4.5 5.0 3.0 3.0 4.5 4.5 <![CDATA[Volumetric hourly space velocity of aniline solution, h -1 > 0.05 0.1 0.4 0.5 0.05 0.05 0.4 1.2 Gas-liquid molar ratio 1:3 1:2.5 1:1.5 1:2 1:3 1:3 1:1.5 1:1.5 Aniline conversion rate (mol%) 36.5 37.1 40.2 38.4 18.3 16.1 42.4 39.4 Diphenylamine selectivity (mol%) 96.8 97.2 96.9 97.3 78.5 68.9 82.6 88.3 Isopropylamine selectivity (mol%) 1.7 1.3 1.2 1.1 — — 0.8 0.3

Claims

1. A method for improving the conversion rate of aniline in the diphenylamine synthesis process, characterized in that, it includes the following contents: The raw material aniline and propylene, at a reaction temperature of 130°C to 220°C and a liquid hourly space velocity of aniline of 0.01 h -1 to 1.0 h -1 , pass through a fixed-bed reactor containing an Hβ zeolite catalyst.

2. The method according to claim 1, characterized in that, the reaction pressure is 1.0 MPa to 10.0 MPa, and the gas-liquid molar ratio of propylene to aniline is 1:(1 - 5).

3. The method according to claim 1, characterized in that, The described Hβ zeolite catalyst comprises, by weight: 50 w% to 90 w% of Hβ zeolite, 0.1 w% to 40 w% of alkali metal, and 0.5 w% to 49.9 w% of γ-Al 2 O 3 , wherein the SiO 2 / Al 2 O 3 molar ratio of the Hβ zeolite is 20 to 100, and the alkali metal is one or more of lithium, sodium, and potassium metals.

4. The method according to claim 1, characterized in that, the reaction temperature is 150 °C to 200 °C.

5. The method according to claim 1 or 2, characterized in that, the reaction pressure is 3.0 MPa to 5.0 MPa.

6. The method according to claim 1, characterized in that, The hourly space velocity of the aniline solution is 0.05 h -1 -1 to 0.5 h -1 .

7. The method according to claim 1 or 2, characterized in that, the gas-liquid molar ratio of propylene to aniline is 1:(1.5 - 3).

8. The method according to claim 1, characterized in that, propylene and aniline flow downward in parallel through a fixed-bed reactor containing an Hβ zeolite catalyst.

9. The method according to claim 1, characterized in that, propylene and aniline flow upward in parallel through a fixed-bed reactor containing an Hβ zeolite catalyst.

10. The method according to claim 1, characterized in that, aniline flows downward and propylene flows upward in a gas-liquid countercurrent manner through a fixed-bed reactor containing an Hβ zeolite catalyst.

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