Catalyst for aniline alkylation and preparation method thereof

Abstract

The invention discloses a catalyst for aniline alkylation and a preparation method, and belongs to the technical field of catalysts. The preparation method of the catalyst comprises the following steps: roasting a catalyst carrier precursor, and adding desalted water into a roasted product to prepare slurry; preparing a mixed solution of copper salt, zinc salt and chromium salt; additionally preparing an alkali solution; adding a metal salt mixed solution and an alkaline solution into the slurry, carrying out a co-precipitation reaction, and then aging; repeatedly filtering and pulping the aged slurry to obtain a catalyst precipitation filter cake; and drying, forming and calcining to obtain the catalyst. The invention also discloses the catalyst for aniline alkylation, which is prepared by the method. The catalyst provided by the invention can realize concerted catalysis of aniline alkylation and methanol steam cracking in a single reactor, methanol and aniline are taken as raw materials, N-methylaniline is synthesized with high selectivity, high-purity hydrogen is co-produced, and no wastewater is discharged in the reaction process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a catalyst for aniline alkylation and a preparation method. BACKGROUND

[0002] As an important chemical intermediate, N-methylaniline is widely used in the fields of explosives and the like. Since the 1950s of the last century, China has introduced the technology from the Soviet Union to realize the industrial production of N-methylaniline by using a Cu-Mn catalyst through a gas phase catalytic method. However, the early catalyst has the technical bottleneck of short service life and frequent regeneration: it needs to be regenerated every 200-300 hours, and the total service life is not more than 2000 hours, which seriously restricts the production continuity and economy.

[0003] In 1983, the CNW-1 type aniline N-alkylation catalyst developed by the applicant was put into industrial application in the Taiyuan Chemical Plant, which significantly improved the catalytic performance. The catalyst has high catalytic activity and excellent selectivity, the aniline conversion rate is generally 90%-96%, the selectivity is 95%-98%, and the catalyst has a long service life, which is verified by long-term industrial practice, marking an important breakthrough in the synthesis of N-methylaniline in China.

[0004] Although the CNW-1 type catalyst has excellent performance, there is still room for optimization in further process integration and product regulation. The main problem is that the traditional aniline alkylation and methanol cracking reaction are usually separate or not deeply synergistic, which limits the overall efficiency of the reaction system. Specifically, the existing catalytic system still has insufficient control over the reaction direction and by-products, which easily leads to the generation of excessive N,N-dimethylaniline, which not only consumes the target product N-methylaniline, but also increases the ton consumption of raw materials and the cost of separation and purification. In addition, the efficient synergy and energy integration of methanol cracking and alkylation reaction at the microscale cannot be achieved, which restricts the further improvement of process economy.

[0005] Therefore, it is a technical problem to be solved by those skilled in the art to develop a catalyst capable of driving aniline and methanol to perform efficient and high-selectivity alkylation reaction, so as to solve the technical problems of short service life and frequent regeneration caused by catalyst carbon deposition inactivation, and many by-products, high raw material unit consumption and the like caused by poor selectivity in the prior art. SUMMARY

[0006] The purpose of the present application is to provide a catalyst for aniline alkylation and a preparation method, which solves the problems of poor catalyst stability, low selectivity of target product and low utilization rate of raw materials in the prior art.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: The first aspect of the present application provides a preparation method of a catalyst for aniline alkylation, comprising the following steps: The catalyst carrier precursor is calcined, and the calcined product is added into desalted water to prepare a slurry; The copper salt, zinc salt and chromium salt are dissolved in the desalted water to prepare a mixed metal salt solution; and an alkali solution is prepared separately; The mixed metal salt solution and the alkali solution are added into the slurry to perform a co-precipitation reaction, and then aging is performed; The aged slurry is filtered, and then is beaten and filtered again, and the beating and filtering process is repeated until the total content of sodium ions and potassium ions in the filter cake is less than or equal to 200 ppm, to obtain a catalyst precipitation filter cake; The catalyst precipitation filter cake is dried to obtain a catalyst precursor; and the catalyst precursor is shaped and calcined to prepare the catalyst.

[0008] In some embodiments of the present application, the catalyst carrier precursor comprises at least one of boehmite, dry glue powder and special alumina powder.

[0009] In some embodiments of the present application, the molar ratio of copper, zinc, aluminum and chromium in the co-precipitation reaction is (0.5-2.5):(0.5-1.5):(0.05-1):(0.05-0.5).

[0010] In some embodiments of the present application, the copper salt, zinc salt and chromium salt each comprises at least one of nitrate, sulfate or hydrochloride.

[0011] In some embodiments of the present application, the alkali solution is an inorganic alkali solution, preferably a solution obtained by dissolving sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate in the desalted water; and more preferably an aqueous sodium carbonate solution.

[0012] In some embodiments of the present application, in the co-precipitation reaction, the pH value at the end of the reaction is controlled to be 7.8-8.3. Preferably, the temperature of the co-precipitation reaction is 70-85℃. Preferably, after the co-precipitation reaction, aging is continued for 60-120 min.

[0013] In some embodiments of the present application, a shaping aid and water are added into the catalyst precursor, and then the mixture is uniformly mixed and pressed to form a tablet. Preferably, the shaping aid comprises graphite, and the amount of the shaping aid is 1-4% of the mass of the catalyst precursor.

[0014] In some embodiments of the present application, the shaped catalyst precursor is calcined at 250-380℃ for 3-6 h.

[0015] The second aspect of the present application discloses a catalyst for aniline alkylation, which is prepared by the above method.

[0016] The third aspect of the present application also discloses a method for evaluating the activity of the catalyst by using a fixed bed reactor, and the reaction product is analyzed by gas chromatography, and the test conditions are as follows: the temperature is 180-280 DEG C, the liquid volume space velocity of the raw material is 0.25-3.5 h -1 .

[0017] Compared with the prior art, the present application has the following beneficial effects: The present application has the advantages that: the catalyst of the present application takes copper metal as the main active center, zinc and chromium as the auxiliary agent, and uses an aluminum source with a large specific surface area as the carrier skeleton, thereby effectively improving the conversion rate and selectivity of the alkylation reaction. By integrating the alkylation function and the methanol cracking function in the same catalytic system, the in-situ reaction of the methanol cracking products, carbon monoxide and water, on the active sites of the catalyst is realized, and carbon dioxide and hydrogen are rapidly converted, thereby promoting the reaction to proceed efficiently. During the reaction process, hydrogen molecules and alkylation products can quickly leave the active center, which not only promotes the forward movement of the reaction, but also pulls fresh raw materials to continuously enter the active sites, forming a virtuous cycle. The high activity and high selectivity of the catalyst ensure the formation of a series reaction path between N-methylaniline and N,N-dimethylaniline, effectively inhibiting the excessive generation of N,N-dimethylaniline, reducing the unnecessary consumption of N-methylaniline, and reducing the raw material consumption per ton.

[0018] The catalyst of the present application can realize the synergistic catalysis of aniline alkylation and methanol steam cracking in a single reactor, and can synthesize N-methylaniline with high selectivity while co-producing high-purity hydrogen gas using methanol and aniline as raw materials, and the reaction process does not discharge wastewater. The overall process has the comprehensive characteristics of high continuity, large capacity, environmental friendliness, and high resource utilization rate, which meets the strict requirements of modern chemical production on high efficiency, cleanliness, and resource comprehensive utilization. DETAILED DESCRIPTION

[0019] All features disclosed in this specification, and / or all steps of any methods or processes disclosed in this specification, can be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0020] Any of the features disclosed in this specification, unless explicitly stated otherwise, can be replaced by alternative features serving the same, or a similar, purpose.

[0021] A preparation method of a catalyst for aniline alkylation, comprising the following steps: The catalyst carrier precursor is calcined, and the calcined product is added into desalted water to prepare a slurry; in some embodiments of the present application, the catalyst carrier precursor comprises at least one of boehmite, dry glue powder and special alumina powder. The calcination temperature is 450-600 ℃, and the calcination time is 2-3 hours.

[0022] The copper salt, zinc salt and chromium salt are dissolved in desalted water to prepare a mixed metal salt solution; the copper salt, zinc salt and chromium salt each comprises at least one of nitrate, sulfate or hydrochloride.

[0023] An alkaline solution is prepared separately; the alkaline solution is an inorganic alkaline solution, preferably a solution of sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate dissolved in desalted water; more preferably an aqueous sodium carbonate solution.

[0024] The mixed metal salt solution and the alkaline solution are added into the slurry to perform a co-precipitation reaction, and then aging. In the co-precipitation reaction, the molar ratio of copper, zinc, aluminum and chromium is (0.5-2.5):(0.5-1.5):(0.05-1):(0.05-0.5). In the co-precipitation reaction, the reaction temperature is 70-85 ℃, and the pH value at the end of the reaction is controlled to be 7.8-8.3. After the co-precipitation reaction, aging is continued at the reaction temperature for 60-120 min.

[0025] The aged slurry is filtered, and then is beaten and filtered again. The beating and filtering process is repeated until the total content of sodium ions and potassium ions in the filter cake is ≤200 ppm, to obtain a catalyst precipitation filter cake. The catalyst precipitation filter cake is dried to obtain a catalyst precursor. The catalyst precursor is shaped and calcined to prepare a catalyst.

[0026] The shaping is performed by adding a shaping aid and water into the catalyst precursor, mixing uniformly and then tabletting and shaping. The shaping aid preferably comprises graphite, and the amount of the shaping aid is 1-4% of the mass of the catalyst precursor.

[0027] The shaped catalyst precursor is calcined at 250-380 ℃ for 3-6 h to prepare a catalyst.

[0028] A catalyst for the alkylation of aniline is prepared by the above method.

[0029] The activity of the catalyst is evaluated by using a fixed bed reactor, and the reaction product is analyzed by gas chromatography. The test conditions are as follows: temperature 180-280 ℃, liquid hourly space velocity (LHSV) of raw material 0.25-3.5 h -1 .

[0030] Example 1 This example discloses a method for preparing a catalyst of the present application, which is as follows: S1. Weigh 102 g of pseudo-boehmite, calcine at 500℃ for 3 hours, then pour the calcined product into a beaker containing 1500 mL of desalted water, stir well to prepare a mixed slurry stock solution.

[0031] S2. Weigh 210.34 g of hydrated copper nitrate, 141.52 g of hydrated zinc nitrate, and 96.43 g of hydrated chromium nitrate, and place them in a beaker containing 500 mL of desalted water and stir to dissolve, supplement with desalted water and dilute to 2000 mL to obtain a mixed metal salt solution containing copper, zinc and chromium.

[0032] S3. Weigh 152.22 g of sodium carbonate, place it in a beaker containing 500 mL of desalted water and stir until completely dissolved, supplement with desalted water and dilute to 2000 mL to obtain a basic solution.

[0033] S4. Preheat the above mixed slurry, mixed metal salt solution and basic solution to 78℃ respectively, and control the reaction water bath temperature to be 78℃ at the same time. After the raw materials and water bath temperature reach the set value, first add the mixed slurry as the stock solution to the reaction kettle and keep high-speed stirring; then add the mixed metal salt solution and the basic solution to the reaction kettle in parallel, control the reaction temperature to be 78℃, after the addition of the mixed metal salt solution is completed, continue to add the basic solution, control the reaction end point pH value to be 7.8; after the reaction is completed, the slurry is aged at the same temperature for 1.5 hours to obtain a reaction slurry.

[0034] S5. The aged reaction slurry is removed from the mother liquor by air pressure filter, then 6000 mL of desalted water is added to the filter cake for beating, and after beating is completed, pressure filtration is carried out again. Repeat the beating and pressure filtration operation 3 times until the sodium ion content in the filter cake is less than 200 ppm to obtain a qualified filter cake.

[0035] S6. Dry the qualified filter cake at 200℃ for 4 hours to obtain a catalyst precursor. After granulating the catalyst precursor, mix 1.5% graphite and 2.0% desalted water with the catalyst precursor, and then press and form to obtain a catalyst semi-product. Place the catalyst semi-product in a calcining furnace and calcine at 300℃ for 4 hours to finally obtain the catalyst of the present application, which is named as catalyst A, with a yield of 239 g.

[0036] Example 2 The present embodiment discloses a preparation method of the catalyst of the present application, which is as follows: S1. Weigh 52 g of pseudo-boehmite and 40 g of special alumina powder, mix them and then calcine at 450℃ for 3 hours, then pour the calcined product into a beaker containing 1500 mL of desalted water, stir well to prepare a mixed slurry stock solution.

[0037] S2. Weigh 208.34 g of hydrated copper nitrate, 144.24 g of hydrated zinc nitrate, and 94.68 g of hydrated chromium nitrate, and place them in a beaker containing 500 mL of desalted water to stir and dissolve. Supplement with desalted water and dilute to 2500 mL to obtain a mixed metal salt solution containing copper, zinc, and chromium.

[0038] S3. Weigh 156.28 g of sodium carbonate, dissolve it in a beaker containing 500 mL of desalted water, and stir until it is completely dissolved. Supplement with desalted water and dilute to 2000 mL to prepare a basic solution.

[0039] S4. Preheat the mixed slurry, mixed metal salt solution, and basic solution described above to 75℃, and control the reaction water bath temperature to be 75℃. After the raw materials and water bath temperature reach the set value, first add the mixed slurry as the bottom liquid to the reaction kettle while maintaining high-speed stirring. Then add the mixed metal salt solution and the basic solution to the reaction kettle in parallel flow, control the reaction temperature to be 75℃, and continue to add the basic solution after the mixed metal salt solution is completely added. Control the reaction endpoint pH value to be 7.9. After the reaction is completed, the slurry is aged at the same temperature for 1.5 hours to obtain a reaction slurry.

[0040] S5. Remove the mother liquor from the aged reaction slurry using an air pressure filter, then add 5500 mL of desalted water to the filter cake for beating, and then pressure filter again. Repeat the beating and pressure filtering operations 3 times until the sodium ion content in the filter cake is less than 200 ppm to obtain a qualified filter cake.

[0041] S6. Dry the qualified filter cake at 220℃ for 3.5 hours to obtain a catalyst precursor. After granulating the catalyst precursor, mix it with 1.7% graphite and 2.5% desalted water based on the mass of the catalyst precursor, and then press and form to obtain a catalyst semi-product. Place the catalyst semi-product in a calcination furnace and calcine it at 290℃ for 4.5 hours to finally obtain the catalyst of the present application, which is named as catalyst B, with a yield of 245 g.

[0042] Example 3 This example discloses a preparation method of the catalyst of the present application, which is as follows: S1. Weigh 32 g of pseudoboehmite and 60 g of special alumina powder, mix them, and then calcine the mixture at 550℃ for 2.5 hours. Then pour the calcined product into a beaker containing 1000 mL of desalted water, and stir thoroughly to prepare a mixed slurry bottom material.

[0043] S2. Weigh 210.14 g of hydrated copper nitrate, 142.24 g of hydrated zinc nitrate, and 91.48 g of hydrated chromium nitrate, and place them in a beaker containing 500 mL of desalted water to stir and dissolve. Supplement with desalted water and dilute to 2000 mL to obtain a mixed metal salt solution containing copper, zinc, and chromium.

[0044] S3. Weigh 176.28 g of potassium carbonate, place it in a beaker containing 500 mL of desalted water, stir until completely dissolved, supplement with desalted water and dilute to 2000 mL to obtain a basic solution.

[0045] S4. Preheat the above mixed slurry, metal mixed salt solution and basic solution to 80℃ respectively, and control the reaction water bath temperature to be 80℃ at the same time. After the raw materials and water bath temperature reach the set value, first add the mixed slurry as the bottom liquid to the reaction kettle and keep high-speed stirring; then add the metal mixed salt solution and the basic solution to the reaction kettle in parallel flow, control the reaction temperature to be 80℃, after the metal mixed salt solution is added dropwise, continue to add the basic solution, control the reaction end point pH value to be 8.0; after the reaction is completed, the slurry is aged at the same temperature for 1 hour to obtain a reaction slurry.

[0046] S5. The aged reaction slurry is removed from the mother liquor by air pressure filter, then 5500 mL of desalted water is added to the filter cake for beating, and after beating, it is pressure filtered again. Repeat the beating and pressure filtering operation 4 times until the sodium ion content in the filter cake is less than 200 ppm to obtain a qualified filter cake.

[0047] S6. Dry the qualified filter cake at 210℃ for 3.5 hours to obtain a catalyst precursor. After granulating the catalyst precursor, mix 2.0% of graphite and 2.0% of desalted water with the catalyst precursor, and then press and form to obtain a catalyst semi-product. Place the catalyst semi-product in a calcining furnace and calcine at 300℃ for 4 hours to finally prepare the catalyst of the application, which is named as catalyst C, and the yield is 242 g.

[0048] Example 4 The present embodiment discloses a preparation method of the catalyst of the application, which is specifically as follows: S1. Weigh 92 g of special alumina powder, calcine at 600℃ for 3 hours, then pour the calcined product into a beaker containing 1000 mL of desalted water, stir well to prepare a mixed slurry bottom material.

[0049] S2. Weigh 215.36 g of hydrated copper nitrate, 138.44 g of hydrated zinc nitrate and 93.48 g of hydrated chromium nitrate, place them in a beaker containing 500 mL of desalted water, stir and dissolve, supplement with desalted water and dilute to 2000 mL to obtain a metal mixed salt solution containing copper, zinc and chromium.

[0050] S3. Weigh 156.28 g of sodium carbonate, place it in a beaker containing 500 mL of desalted water, stir until completely dissolved, supplement with desalted water and dilute to 2000 mL to obtain a basic solution.

[0051] S4. Preheat the above-mentioned mixed slurry, mixed metal salt solution, and alkaline solution to 80°C, while simultaneously controlling the reaction water bath temperature at 80°C. After the raw materials and water bath temperatures reach the set values, first add the mixed slurry as the base liquid to the reactor and maintain high-speed stirring; then add the mixed metal salt solution and alkaline solution to the reactor in parallel, controlling the reaction temperature at 80°C. After the mixed metal salt solution is completely added, continue adding the alkaline solution, controlling the final pH value of the reaction to be 8.0; after the reaction is completed, age the slurry at the same temperature for 1 hour to obtain the reaction slurry.

[0052] S5. Remove the mother liquor from the aged reaction slurry using an air filter press. Then, add 5500 mL of demineralized water to the filter cake and purge. After slurrying, filter again. Repeat the slurrying and filtration process three times until the sodium ion content in the filter cake is below 200 ppm, thus obtaining a qualified filter cake.

[0053] S6. The qualified filter cake is dried at 230℃ for 3 hours to obtain the catalyst precursor. After granulation of the catalyst precursor, 2.5% graphite and 2.0% demineralized water by weight of the catalyst precursor are added and mixed, and then pressed into tablets to obtain the catalyst semi-finished product. The catalyst semi-finished product is placed in a calcination furnace and calcined at 280℃ for 4.5 hours to finally obtain the catalyst of the present invention, named catalyst D, with a yield of 238g.

[0054] Experimental Example 1 The catalysts prepared in Examples 1 to 4 were tested for activity under three different conditions and compared with the existing catalyst CNW-1. The specific conditions were: (1) 220℃, atmospheric pressure, and liquid hourly space velocity of 2 h⁻¹. -1 (2) 220℃, normal pressure, liquid hourly space velocity 1h -1 (3) 210℃, normal pressure, liquid hourly space velocity 2h -1 The products were analyzed using gas chromatography, and the results are shown in Table 1.

[0055] The specific surface area of ​​the catalysts prepared in Examples 1 to 4 was tested and compared with that of the existing catalyst CNW-1. The results are shown in Table 1.

[0056] Table 1. Catalyst activity test results

[0057] Table 2 Catalyst Specific Surface Area

[0058] As shown in Table 1, the catalyst prepared in this invention outperforms the traditional CNW 1 catalyst in both aniline conversion and N-methylaniline yield. The improved catalyst performance is mainly attributed to the novel preparation process and optimized component ratio, which significantly increases the specific surface area and reaction contact area of ​​the catalyst, thereby enhancing the copper... The active centers of the chromium bicomponent are more fully utilized. Table 2 further shows that the specific surface area of ​​the catalyst of this invention is increased by 20-30% compared to the traditional CNW-1, providing strong support for improved conversion and selectivity.

[0059] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for preparing a catalyst for the alkylation of aniline, characterized in that, Includes the following steps: The catalyst support precursor is calcined, and the calcination product is added to demineralized water to obtain a slurry. Copper salt, zinc salt, and chromium salt are dissolved in demineralized water to prepare a mixed solution of metal salts. Prepare an alkaline solution separately; A mixed solution of metal salts and an alkaline solution are added to the slurry to carry out a co-precipitation reaction, followed by aging. The aged slurry was filtered and pulped, and the filtration and pulping operations were repeated until the total content of sodium and potassium ions in the resulting filter cake was ≤200ppm, thus obtaining the catalyst precipitated filter cake. The catalyst precursor is obtained by drying the catalyst precipitate filter cake; the catalyst precursor is then shaped and calcined to obtain the catalyst.

2. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, The catalyst support precursor includes at least one of boehmite, dry adhesive powder, and special alumina powder.

3. A method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, The molar ratio of copper, zinc, aluminum, and chromium in the coprecipitation reaction is (0.5–2.5): (0.5–1.5): (0.05–1): (0.05–0.5).

4. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, The copper salt, zinc salt, and chromium salt each include at least one of nitrate, sulfate, or hydrochloride.

5. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, The alkaline solution is an inorganic alkaline solution, preferably a solution obtained by dissolving sodium hydroxide, potassium hydroxide, potassium carbonate, or sodium carbonate in demineralized water; more preferably, it is an aqueous solution of sodium carbonate.

6. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, In the coprecipitation reaction, the final pH value is controlled to be 7.8–8.3; Preferably, the coprecipitation reaction temperature is 70–85°C; Preferably, after the coprecipitation reaction, the product is aged for another 60-120 minutes.

7. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, Add molding aid and water to the catalyst precursor, mix well, and then compress into tablets; Preferably, the molding aid includes graphite; its amount is 1 to 4% of the mass of the catalyst precursor.

8. The method for preparing a catalyst for aniline alkylation according to claim 1, characterized in that, The shaped catalyst precursor was calcined at 250–380℃ for 3–6 hours.

9. A catalyst for the alkylation of aniline, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The method for evaluating the activity of a catalyst according to claim 9, characterized in that, A fixed-bed reactor was used, and the reaction products were analyzed by gas chromatography under the following conditions: temperature 180–280℃, and liquid hourly space velocity (LHSV) of the feedstock 0.25–3.5 h⁻¹. -1 .

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