Regeneration liquid and regeneration method for synthesizing diphenylamine catalyst from aniline

Abstract

The invention discloses a regeneration liquid of a diphenylamine catalyst synthesized from aniline. The regeneration liquid is prepared from the following components in parts by mole: 15 to 65 parts of N, N-dimethylformamide, 10 to 30 parts of tetrahydrofuran, 10 to 40 parts of N-methyl pyrrolidone and 10 to 60 parts of n-decane. The regeneration liquid provided by the invention can effectively soften and dissolve carbon deposits generated at the initial stage in the process of synthesizing diphenylamine from aniline, especially polyaniline-like carbon deposits, and coke carried outside the polyaniline carbon deposits and further generated falls off together, so that the catalyst can be thoroughly decarbonized to obtain a better regeneration effect.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a regeneration solution and regeneration method for a catalyst used in the synthesis of diphenylamine from aniline. Background Technology

[0002] Diphenylamine is a widely used chemical product with important applications in rubber additives, dyes, explosive stabilizers, fruit preservatives, and pharmaceuticals. Currently, there are approximately 20 methods for synthesizing diphenylamine, using raw materials such as aniline, phenol, cyclohexanone, N-cyclohexylaniline, and dicyclohexyl, and catalysts such as aluminum trichloride, boron trifluoride, activated alumina, and zeolite molecular sieves. Among these methods, the method using aniline as a single raw material to produce diphenylamine has the best atom economy and the strongest feasibility for large-scale production, and has already been industrialized. The production processes for synthesizing diphenylamine from aniline are divided into batch processes, gas-phase continuous processes, and liquid-phase continuous processes, with the liquid-phase continuous process currently being the most advanced.

[0003] Continuous gas-phase synthesis of diphenylamine from aniline γ Al₂O₃ is used as a catalyst and can be regenerated and reused. US44534348 and US3118944 report processes for the continuous gas-phase preparation of diphenylamine from aniline. In these processes, alumina is used as a catalyst, and the reaction temperature is above 450℃. Although the aniline conversion rate can reach over 30%, the excessively high reaction temperature easily causes pyrolysis and polymerization of the reactants, shortening the catalyst life, requiring frequent catalyst regeneration, and the regeneration temperature is as high as 500℃ or higher, making the regeneration conditions extremely harsh.

[0004] CN101172262A reports a method for regenerating a catalyst in the continuous liquid-phase synthesis of diphenylamine from aniline. This method employs in-system oxygen-containing chlorine coking regeneration, including steps such as purging the entire system with nitrogen to remove the reaction mixture, stepwise combustion regeneration with oxygen-containing ammonia, system cooling, and nitrogen replacement of the oxygen-containing gas. The regenerated catalyst properties are essentially the same as the fresh catalyst. However, this method still uses high-temperature calcination for catalyst regeneration, which not only consumes a large amount of energy but also emits significant amounts of greenhouse gases and NO. x Pollutants pose a very serious environmental problem. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a regeneration solution and method for a catalyst used in the preparation of diphenylamine from aniline. This method uses an organic regeneration solution to regenerate the catalyst, resulting in a simple regeneration operation, low regeneration temperature, and good regeneration effect.

[0006] The catalyst for the continuous preparation of diphenylamine from aniline described in this invention refers to a catalyst with Hβ zeolite and alumina as the main components. The catalyst can be synthesized according to conventional methods in the art (such as those disclosed in CN200510047489.9). Under certain process conditions, when the aniline conversion rate is ≤15 mol%, the catalyst is considered deactivated and requires regeneration. The deactivated catalyst comprises: 45 wt%–85 wt% Hβ zeolite, 0–4.0 wt% alkali metal or alkaline earth metal, 5 wt%–15 wt% carbon deposits, and 5 wt%–45 wt% alumina.

[0007] According to a first objective of the present invention, the present invention provides a regeneration solution for a catalyst used in the continuous preparation of diphenylamine from aniline.

[0008] Specifically, the regenerated liquid comprises, in molar amounts: 15-65 molar parts of N,N-dimethylformamide, preferably 35-50 molar parts; 10-30 molar parts of tetrahydrofuran, preferably 15-20 molar parts; 10-40 molar parts of N-methylpyrrolidone, preferably 25-30 molar parts; 10–60 moles of n-decane, preferably 30–40 moles.

[0009] Furthermore, the regenerated solution for the continuous preparation of diphenylamine catalyst from aniline can be prepared using conventional methods in the art. A typical preparation method for the regenerated solution is as follows: N,N-dimethylformamide and tetrahydrofuran are mixed in a certain proportion, N-methylpyrrolidone is added in a certain proportion after the mixture is homogeneous, and finally n-decane is added in a certain proportion. After mixing evenly, the mixture is allowed to stand for a period of time to obtain the regenerated solution.

[0010] According to a second objective of the present invention, the present invention also provides an in-plant regeneration method for a catalyst for the synthesis of diphenylamine from aniline, wherein the regeneration solution described above is used.

[0011] Specifically, the in-device regeneration method includes the following: (1) First, reduce the temperature of the reactor bed to 20℃~90℃, cut off the reactor outlet, inject regenerant into the reactor, and seal the reactor after the regenerant has filled the reactor. (2) Raise the temperature of the catalyst bed in the reactor to 80℃~150℃, maintain it for 1~6 hours, then cool it down and discharge the regenerated liquid from the reactor; (3) After washing the catalyst bed with aniline, purge it with nitrogen. Once the bed is dry, it can be used.

[0012] Furthermore, the catalyst bed temperature in step (2) is preferably 100℃~120℃.

[0013] Furthermore, the system pressure in step (2) is maintained at 0.1MPa to 0.8MPa, preferably 0.3MPa to 0.5MPa.

[0014] Furthermore, the regeneration time in step (2) is 1 to 6 hours, preferably 2 to 4 hours.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The regeneration liquid provided by the present invention can effectively soften and dissolve the carbon deposits generated in the initial stage of the aniline to diphenylamine synthesis process, especially polyaniline-like carbon deposits, and cause them to fall off from the catalyst surface. The coke further generated on the outside of the polyaniline-like carbon deposits also falls off together, thereby thoroughly decarbonizing the catalyst and obtaining a better regeneration effect.

[0016] 2. The regeneration method for the catalyst in the continuous preparation of diphenylamine from aniline provided by this invention first involves soaking and cleaning the catalyst bed with an organic regeneration solution, followed by purging to complete catalyst regeneration. Compared with current regeneration methods for deactivated diphenylamine catalysts, the method provided by this invention is simple to operate, has a low regeneration temperature, and achieves good regeneration results, effectively mitigating environmental pollution during catalyst regeneration. Furthermore, the organic regeneration solution can be reused after simple treatment. Detailed Implementation

[0017] The method of the present invention will be described in more detail below with reference to specific embodiments.

[0018] The catalyst for the continuous preparation of diphenylamine from aniline refers to a catalyst with Hβ zeolite and alumina as the main components. In the examples, two catalysts, catalyst A and catalyst B, were synthesized according to the method reported in CN200510047489.9. When used under certain process conditions, the catalyst needs to be regenerated when the aniline conversion rate is ≤15 mol%. The deactivated catalyst at this time consists of: 45 wt%–80 wt% Hβ zeolite, 0–4.0 wt% alkali metal or alkaline earth metal, 5 wt%–15 wt% carbon deposits, and the remainder being alumina. Example 1

[0019] In the evaluation of the fixed-bed reactor, the process conditions in CN1289763A were used (reaction temperature 340℃, reaction pressure 4.0MPa, aniline liquid hourly space velocity 0.2h⁻¹). -1Catalyst A was aged. The resulting deactivated catalyst consisted of 50.4 wt% Hβ zeolite, 3.2 wt% alkali metal sodium, 12.8 wt% carbon deposits, and the remainder being alumina. After aging, the reactor temperature was lowered to 60°C, and an organic regeneration liquid (composition shown in Table 1) was injected into the reactor. Once the reactor was full, it was sealed, the reaction temperature was raised to 100°C, and the system pressure was maintained at 0.3 MPa. After 4 hours, the temperature was lowered, the organic regeneration liquid was released, the catalyst bed was washed with aniline, and then purged with nitrogen. After the bed was dried, it was evaluated according to the previous process conditions. The evaluation results are shown in Table 2. Example 2

[0020] In the evaluation of the fixed-bed reactor, the process conditions in CN1289763A were used (reaction temperature 340℃, reaction pressure 4.0MPa, aniline liquid hourly space velocity 0.2h⁻¹). -1 Catalyst A was aged. The resulting deactivated catalyst consisted of 50.8 wt% Hβ zeolite, 3.6 wt% alkali metal sodium, 13.5 wt% carbon deposits, and the remainder being alumina. An organic regeneration solution (composition shown in Table 1) was injected into the reactor, the regeneration temperature was raised to 120℃, and the system pressure was maintained at 0.5 MPa. After 2 hours, the temperature was lowered and the organic regeneration solution was released. The catalyst bed was washed with aniline and then purged with nitrogen. After the bed was dried, it was evaluated according to the previous process conditions. The evaluation results are shown in Table 2. Example 3

[0021] In the evaluation of the fixed-bed reactor, the process conditions in CN1289763A were used (reaction temperature 340℃, reaction pressure 4.0MPa, aniline liquid hourly space velocity 0.2h⁻¹). -1 Catalyst B was aged. The resulting deactivated catalyst consisted of 70.5 wt% Hβ zeolite, 1.6 wt% alkali metal potassium, 8.4 wt% carbon deposits, and the remainder being alumina. An organic regeneration solution (composition shown in Table 1) was injected into the reactor, the regeneration temperature was raised to 140℃, and the system pressure was maintained at 0.5 MPa. After 1 hour, the temperature was lowered and the organic regeneration solution was released. The catalyst bed was then washed with aniline and purged with nitrogen. After the bed was dried, it was evaluated according to the previous process conditions. The evaluation results are shown in Table 2. Example 4

[0022] In the evaluation of the fixed-bed reactor, the process conditions in CN1289763A were used (reaction temperature 340℃, reaction pressure 4.0MPa, aniline liquid hourly space velocity 0.2h⁻¹). -1Catalyst B was aged. The resulting deactivated catalyst consisted of 70.9 wt% Hβ zeolite, 1.2 wt% alkali metal potassium, 7.9 wt% carbon deposits, and the remainder being alumina. An organic regeneration solution (composition shown in Table 1) was injected into the reactor, the regeneration temperature was raised to 80°C, and the system pressure was maintained at 0.1 MPa. After 5 hours, the temperature was lowered, the organic regeneration solution was released, the catalyst bed was washed with aniline, and then purged with nitrogen. After the bed was dried, it was evaluated according to the previous process conditions. The evaluation results are shown in Table 2.

[0023] Comparative Example 1 The deactivated catalyst with the same composition as in Example 1 was regenerated according to the regeneration method in CN101172262A. The specific operating steps were as follows: using a nitrogen-oxygen mixture as the regeneration gas, the reactor inlet temperature was first raised to 220°C, and the oxygen content in the regeneration gas was gradually increased from 0.01% to 0.5%, and held at this temperature for 24 hours; then, the reactor inlet temperature was raised to 310°C, and the oxygen content in the regeneration gas was gradually increased to 1.0%, and held at this temperature for 24 hours; next, the reactor inlet temperature was raised to 450°C, and the oxygen content in the regeneration gas was gradually decreased by 0.1%, and held at this temperature for 24 hours; finally, at 450°C, the oxygen content in the regeneration gas was gradually increased to 2.0%, and held at this temperature for 24 hours. After the temperature was held at this point, the regeneration gas was stopped, and nitrogen was introduced to cool the reactor. When the reactor inlet temperature dropped to 100°C, the catalyst regeneration was complete. The process conditions in CN1289763A were also followed (reaction temperature 340°C, reaction pressure 4.0 MPa, aniline liquid hourly space velocity 0.2 h⁻¹). -1 The performance of the regenerated catalyst was evaluated. The evaluation results are shown in Table 2.

[0024] Table 1. Composition of regenerated solution (unit: molar parts) Example number Example 1 Example 2 Example 3 Example 4 DMF 50 35 25 20 THF 10 15 10 15 NMP 25 30 40 30 n-Dec 15 20 15 30 Table 2 Evaluation Results (Unit: mol%) Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Catalyst A Catalyst B Aniline conversion rate 22.8 23.2 22.6 22.3 22.1 23.5 23.6 Diphenylamine selectivity 97.5 96.4 97.3 97.4 97.2 97.6 97.8

Claims

1. A regeneration solution for a catalyst used in the continuous preparation of diphenylamine from aniline, characterized in that, The regenerated solution comprises, in molar parts: 15-65 molar parts of N,N-dimethylformamide; 10-30 molar parts of tetrahydrofuran; 10-40 molar parts of N-methylpyrrolidone; 10-60 moles of n-decane.

2. The regenerated liquid according to claim 1, characterized in that, The regenerated solution comprises, in molar parts: 35-50 molar parts of N,N-dimethylformamide; Tetrahydrofuran, 10-30 molar parts, 15-20 molar parts; 25-30 molar parts of N-methylpyrrolidone; 30-40 moles of n-decane.

3. The method for preparing the regenerated liquid according to claim 1 or 2, characterized in that, The process includes the following steps: N,N-dimethylformamide and tetrahydrofuran are mixed in a certain proportion. After mixing thoroughly, N-methylpyrrolidone is added in a certain proportion, and finally n-decane is added in a certain proportion. After mixing thoroughly, the mixture is allowed to stand for a period of time to obtain the regenerated solution.

4. An in-process regeneration method for a catalyst used in the synthesis of diphenylamine from aniline, characterized in that, The regenerated liquid according to claim 1 or 2 was used.

5. The in-device regeneration method according to claim 4, characterized in that, The in-device regeneration method includes the following: (1) First, lower the reactor temperature to 20℃~90℃, cut off the reactor outlet, inject regenerant into the reactor, and seal the reactor after the regenerant has filled the reactor. (2) Raise the temperature of the catalyst bed in the reactor to 80℃~150℃, maintain it for 1~6 hours, then cool it down and discharge the regenerated liquid from the reactor; (3) After washing the catalyst bed with aniline, purge it with nitrogen. Once the bed is dry, it can be used.

6. The in-device regeneration method according to claim 5, characterized in that, In step (2), the catalyst bed temperature is 100℃~120℃.

7. The in-device regeneration method according to claim 5, characterized in that, The system pressure in step (2) is 0.1MPa to 0.8MPa.

8. The in-device regeneration method according to claim 7, characterized in that, The system pressure in step (2) is 0.3MPa to 0.5MPa.

9. The in-device regeneration method according to claim 5, characterized in that, The regeneration time in step (2) is 2 to 4 hours.

10. The in-device regeneration method according to claim 4 or 5, characterized in that, The catalyst for the synthesis of diphenylamine from aniline comprises: 45 wt% to 85 wt% H. β Zeolite, 0–4.0 wt% alkali metal or alkaline earth metal, 5 wt%–15 wt% carbon deposits, and 5 wt%–45 wt% alumina.