NiAl catalyst, preparation method thereof and application of NiAl catalyst in preparation of N-ethylaniline
The high-active NiAl catalyst was prepared by co-precipitation method and applied to the one-pot nitrobenzene method to prepare N-ethylaniline, which solved the problem of poor conversion and selectivity in the prior art, and achieved the target product with high efficiency, simplified processes and high yields.
Patent Information
- Application Number
- CN202510117250.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-24
- Publication Date
- 2025-03-18
AI Technical Summary
The prior art has problems with poor conversion and selectivity in the preparation of N-ethylaniline, and the process is complicated.
NiAl catalyst was prepared by co-precipitation method, and NiAl catalyst with high activity and high stability was prepared by optimizing the NiAl ratio and preparation conditions, and N-ethylaniline was prepared by applying it to the one-pot nitrobenzene method.
High conversion and selectivity from nitrobenzene to aniline to N-ethylaniline are achieved, simplifying the synthesis process, improving the yield of the target product, and reducing the generation of contaminants.
Smart Images
Figure CN119633827A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a NiAl catalyst and a preparation method thereof and application thereof in the preparation of N-ethylaniline. Background Art
[0002] N-ethylaniline is an important organic compound, which appears as a yellow-brown transparent liquid with a special aniline smell. It has good solubility and is insoluble in water but can be quickly dissolved in most organic solvents such as ethanol and ether. It can participate in a variety of organic synthesis reactions, such as substitution and addition. N-ethylaniline is an important intermediate for the synthesis of azo dyes and triphenylmethane dyes. Azo dyes are a class of dyes widely used in textiles, leather, paper and other industries. Their bright colors and excellent fastness make them an indispensable part of the market. Triphenylmethane dyes also have a unique position in the dyeing industry due to their special chemical structure and color properties. The participation of N-ethylaniline makes the synthesis process of these dyes more efficient and stable.
[0003] The methods for preparing N-ethylaniline in industry mainly include the traditional high temperature and high pressure method, the gas phase method, and the phosphorus oxychloride catalytic method. The phosphorus oxychloride catalytic method is generally used in the industry, that is, under the catalytic action of phosphorus oxychloride (PoCl3), aniline and ethanol react to generate N-ethylaniline and N,N-diethylaniline. By optimizing the reaction conditions, such as temperature, pressure, catalyst dosage, alcohol amine molar ratio, etc., a higher conversion rate and selectivity can be obtained. However, this method still faces the problem that some aniline is difficult to completely convert into the target product.
[0004] Aniline is the raw material of N-ethylaniline. Common industrial preparation methods mainly include nitrobenzene iron powder reduction method, nitrobenzene catalytic hydrogenation method, and phenol ammonolysis method. Taking into account factors such as environmental impact, economic benefits, safety, and scalability, the mainstream production method currently used in industry is nitrobenzene catalytic hydrogenation. Nitrobenzene catalytic hydrogenation methods are divided into gas-phase catalytic hydrogenation and liquid-phase catalytic hydrogenation. Among them, fixed-bed gas-phase catalytic hydrogenation in gas-phase catalytic hydrogenation has low cost, no need to separate the catalyst separately, low reaction temperature, and good product quality, but the heat transfer effect is poor, which causes side reactions and catalyst deactivation; while fluidized bed gas-phase catalytic hydrogenation is complicated to operate, has high catalyst wear, and high maintenance costs.
[0005] In summary, in the preparation process of N-ethylaniline, aniline is first prepared by gas-phase catalytic hydrogenation of nitrobenzene, and then N-ethylaniline is prepared by phosphorus oxychloride catalysis using aniline as a raw material. The synthesis process is cumbersome, and both steps have problems of poor conversion rate and selectivity. Summary of the invention
[0006] The purpose of the present invention is to solve the above problems in the prior art and to provide a NiAl catalyst and a preparation method thereof and application of the NiAl catalyst in the preparation of N-ethylaniline. The present invention adopts a coprecipitation method and optimizes the NiAl ratio and preparation conditions to prepare a NiAl catalyst with high activity and high stability, and applies the NiAl catalyst to the one-pot preparation of N-ethylaniline from nitrobenzene, thereby achieving a high conversion rate and high selectivity from nitrobenzene to aniline and then to N-ethylaniline, so as to improve the yield of N-ethylaniline.
[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0008] A first aspect of the present invention is to provide a method for preparing a NiAl catalyst, comprising the following steps:
[0009] (1) After mixing the nickel salt solution and the aluminum salt solution, a precipitant is added to adjust the pH, and stirring and crystallization are continued to obtain a mixed solution;
[0010] (2) The obtained mixed solution is filtered, washed and dried to obtain a NiAl catalyst.
[0011] The present invention is further configured such that the molar ratio of Ni to Al in the NiAl catalyst is 3:1 to 5:1, preferably 4:1.
[0012] The present invention is further configured that, in step (1), the nickel salt is selected from one or more of nickel hydroxide, nickel nitrate, nickel oxide and nickel sulfate, preferably nickel nitrate hexahydrate;
[0013] The aluminum salt is selected from one or more of aluminum nitrate and aluminum sulfate, preferably aluminum nitrate nonahydrate. The present invention is further configured that, in step (1), the precipitant is selected from one or more of anhydrous sodium carbonate, ammonia water and sodium hydroxide; the precipitant is added to adjust the pH to 8-10, preferably pH 10.
[0014] The present invention is further configured such that, in step (1), the crystallization temperature is 50-70° C., and the crystallization time is 18-24 h. Preferably, the crystallization temperature is 70° C., and the crystallization time is 24 h.
[0015] The second aspect of the present invention is to provide a NiAl catalyst prepared by the above preparation method.
[0016] The third aspect of the present invention is to provide the use of the above-mentioned NiAl catalyst in the preparation of N-ethylaniline, comprising the following steps:
[0017] NiAl catalyst, dodecane, nitrobenzene and ethanol were added to the reaction kettle in sequence, and the kettle was sealed; argon gas was introduced for ventilation and stirring, and then hydrogen gas was introduced for ventilation, and then hydrogen gas was injected into the kettle, and the reaction was carried out at a constant temperature after heating to the reaction temperature.
[0018] The present invention is further configured as follows: the addition amount of dodecane is 0.5-1 mL, the addition amount of nitrobenzene is 1.5-2.5 mL, the addition amount of ethanol is 20-25 mL, the addition amount of NiAl catalyst is 0.2-0.3 g, and the pressure of injected hydrogen is 1.15-1.25 MPa.
[0019] The present invention is further configured such that the reaction temperature is 110-130° C. and the reaction time is 5-8 hours.
[0020] The present invention is further configured that the NiAl catalyst needs to be reduced before use, the reducing atmosphere is hydrogen, and the reducing temperature is 500°C.
[0021] The beneficial effects of the present invention are as follows:
[0022] (1) The NiAl catalyst developed by the present invention is used to catalyze the one-pot preparation of N-ethylaniline from nitrobenzene, which can overcome the problem that there are many by-products in the current industrial preparation of aniline and N-ethylaniline, and it is difficult to completely convert them into the target product. It can better control N-alkylation in the monoalkylation stage, which is significantly better than the traditional N-alkylation route. At the same time, in a reactor, the one-pot synthesis of N-alkylaniline under the same catalyst and the same reaction conditions simplifies the synthesis process, and the hydrogen and aromatic amines generated in the reaction process can be removed from the catalyst surface in time, thereby improving the selectivity of the target product N-ethylaniline. Compared with the traditional chemical reduction method, the conditions of this method are milder, the requirements on equipment are not harsh, and the three wastes are relatively easy to treat. At the same time, this method does not require an independent hydrogen production process, thereby reducing a large number of pollutants generated in the traditional method, being more environmentally friendly, and having a huge application prospect.
[0023] (2) The NiAl catalyst developed in the present invention has a simple process and exhibits good reductive amination activity and low cost advantages compared to existing catalysts. It also has high activity and high stability and can achieve high conversion rate and high selectivity at lower temperature and pressure. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a stability test chart of the catalysts prepared in Example 2, Example 7, Comparative Example 1 and Comparative Example 2.
[0025] Figure 2 This is a TEM image of the catalyst prepared in Example 2 before reduction.
[0026] Figure 3 This is a TEM image of the catalyst prepared in Example 2 after reduction. DETAILED DESCRIPTION
[0027] The technical solution of the present invention is described clearly and in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the following embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.
[0028] The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturers, and the materials and reagents used in the following examples are conventional commercial products. Unless otherwise specified, all percentages, ratios, proportions, or parts are by weight.
[0029] Example 1: Preparation of Ni3Al1 Catalyst
[0030] (1) Prepare sodium hydroxide solution and metal salt solution:
[0031] Weigh 15 g of sodium hydroxide into a beaker, add 250 mL of ultrapure water thereto, stir evenly until completely dissolved, and seal with plastic wrap; weigh 8.7237 g of nickel nitrate hexahydrate and 3.7513 g of aluminum nitrate nonahydrate into another beaker, add 100 mL of ultrapure water thereto, stir evenly until completely dissolved, and seal with plastic wrap.
[0032] (2) Preparation of catalyst by coprecipitation method:
[0033] Weigh 0.53g of anhydrous sodium carbonate into a three-necked flask, add 150mL of ultrapure water and stir evenly until completely dissolved. Slowly drip the metal salt solution and sodium hydroxide solution into the three-necked flask through the two feeding ports of the three-necked flask, and keep the pH value of the solution in the three-necked flask at 10. After the metal salt solution is added, transfer the three-necked flask to a constant temperature water bath at 70°C and continue stirring and crystallizing for 24 hours. Filter the resulting mixed solution, wash it with deionized water until it is neutral, then wash it once with anhydrous ethanol, and collect the precipitate. Place the resulting precipitate in an oven and dry it for 12 hours to obtain the Ni3Al1 catalyst.
[0034] Example 2: Preparation of Ni4Al1 Catalyst
[0035] This embodiment is substantially the same as embodiment 1, except that, when preparing the metal salt solution, 11.6316 g of nickel nitrate hexahydrate and 3.7513 g of aluminum nitrate nonahydrate are weighed respectively; finally, a Ni4Al1 catalyst is obtained, and the Ni loading amount is 5 wt%.
[0036] Example 3: Preparation of Ni5Al1 Catalyst
[0037] This embodiment is substantially the same as embodiment 1, except that, when preparing the metal salt solution, 14.5395 g of nickel nitrate hexahydrate and 3.7513 g of aluminum nitrate nonahydrate are weighed respectively; and finally, a Ni5Al1 catalyst is obtained.
[0038] Example 4: Preparation of Ni4Al1-8 Catalyst
[0039] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the coprecipitation method, the pH value of the solution in the three-necked flask is maintained at 8; and finally a Ni4Al1-8 catalyst (named after the pH value of the solution in the three-necked flask) is obtained.
[0040] Example 5: Preparation of Ni4Al1-9 Catalyst
[0041] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the coprecipitation method, the pH value of the solution in the three-necked flask is maintained at 9; and finally a Ni4Al1-9 catalyst (named after the pH value of the solution in the three-necked flask) is obtained.
[0042] Example 6: Preparation of Ni4Al1-50 catalyst
[0043] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the co-precipitation method, the three-necked flask is transferred to a constant temperature water bath at 50°C and stirred and crystallized for 24 hours; finally, the Ni4Al1-50 catalyst (named after the crystallization temperature) is obtained.
[0044] Example 7: Preparation of Ni4Al1-60 catalyst
[0045] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the co-precipitation method, the three-necked flask is transferred to a constant temperature water bath at 60°C and stirred and crystallized for 24 hours; finally, the Ni4Al1-60 catalyst (named after the crystallization temperature) is obtained.
[0046] Example 8: Preparation of Ni4Al1-12 Catalyst
[0047] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the co-precipitation method, the three-necked flask is transferred to a constant temperature water bath at 70°C and stirred and crystallized for 12 hours; finally, a Ni4Al1-12 catalyst (named after the crystallization time) is obtained.
[0048] Example 9: Preparation of Ni4Al1-18 Catalyst
[0049] This embodiment is basically the same as embodiment 2, except that when the catalyst is prepared by the co-precipitation method, the three-necked flask is transferred to a constant temperature water bath at 70°C and stirred and crystallized for 18 hours; finally, the Ni4Al1-18 catalyst (named after the crystallization time) is obtained.
[0050] Comparative Example 1: Preparation of Mo4Al1 Catalyst
[0051] This comparative example is substantially the same as Example 2, except that, when preparing the solution, 13.9832 g of ammonium molybdate tetrahydrate and 3.9752 g of aluminum nitrate nonahydrate were weighed respectively; and finally, a Mo4Al1 catalyst was obtained.
[0052] Comparative Example 2: Preparation of Fe4Al1 Catalyst
[0053] This comparative example is basically the same as Example 2, except that, when preparing the solution, 19.2892 g of ferric nitrate nonahydrate and 9.1391 g of aluminum nitrate nonahydrate were weighed respectively; and finally, Fe4Al1 catalyst was prepared.
[0054] Comparative Example 3: Preparation of Cu4Al1 Catalyst
[0055] This comparative example is basically the same as Example 2, except that, when preparing the solution, 15.2153 g of copper nitrate trihydrate and 13.9112 g of aluminum nitrate nonahydrate were weighed respectively; finally, a Cu4Al1 catalyst was prepared.
[0056] Comparative Example 4: Preparation of Ni-MgO Catalyst
[0057] The Ni-MgO catalyst was prepared using nickel as a precursor with a loading of 5 wt %, and the steps are as follows:
[0058] (1) Pre-treating the magnesium oxide carrier to ensure that its surface state is suitable for impregnation; specifically, crushing and screening to obtain a magnesium oxide carrier with a suitable particle size, and drying to remove surface moisture.
[0059] (2) Dissolve 0.652 g of nickel nitrate hexahydrate in 2 mL of deionized water to form an impregnation solution.
[0060] (3) Add the pretreated magnesium oxide support into the nickel nitrate solution according to the loading amount for impregnation, and ensure that the support is completely covered by the solution so that the nickel nitrate can be evenly adsorbed on the surface of the magnesium oxide.
[0061] (4) removing excess liquid and placing the carrier after the excess liquid is removed into an oven for drying for 12 hours.
[0062] Comparative Examples 5 to 16
[0063] Comparative Examples 5 to 16 are basically the same as Comparative Example 4, except that the carriers are CaO, ZnO, La2O3, αAl2O3, γAl2O3, θAl2O3, SiO2, SnO2, TiO2, ZrO2, CeO2 and Nb2O5, respectively, to prepare Ni-CaO catalyst, Ni-ZnO catalyst, Ni-La2O3 catalyst, Ni-αAl2O3 catalyst, Ni-γAl2O3 catalyst, Ni-θAl2O3 catalyst, Ni-SiO2 catalyst, Ni-SnO2 catalyst, Ni-TiO2 catalyst, Ni-ZrO2 catalyst, Ni-CeO2 catalyst and Ni-Nb2O5 catalyst, respectively.
[0064] Catalytic performance evaluation
[0065] The catalyst prepared by the above-mentioned embodiments 1 to 9 and comparative examples 1 to 16 was applied to the reaction of preparing N-ethylaniline from nitrobenzene in one pot, and the catalytic performance was evaluated. The reaction was carried out in a reactor, and the reducing atmosphere was H2. 0.2g of catalyst, 0.5mL of dodecane, 2mL of nitrobenzene and 20mL of ethanol were added to the reactor in sequence, and the reactor was sealed; 0.4MPa of argon was introduced, ventilated five times, and stirred for 15 minutes; hydrogen was introduced, ventilated three times, and 1.2MPa of hydrogen was injected into the reactor, heated to 120°C and reacted at a constant temperature for 8h, and the outlet product was analyzed by liquid chromatography. The NiAl catalyst was reduced in a hydrogen atmosphere before use, and the reduction temperature was 500°C.
[0066] The catalytic results of different catalysts in the one-pot preparation of N-ethylaniline from nitrobenzene are shown in Table 1.
[0067] The catalysts prepared in Example 2, Example 7, Comparative Example 2 and Comparative Example 1 were tested for stability. The test results are as follows: Figure 1 shown.
[0068] TEM images of the Ni4Al1 catalyst prepared in Example 2 before and after reduction are shown in Figure 2 and Figure 3 shown.
[0069] Table 1 Catalytic results of different catalysts in the one-pot preparation of N-ethylaniline from nitrobenzene
[0070]
[0071]
[0072] As can be seen from the catalytic results of Examples 1 to 9 in Table 1, the preparation method of the present invention is adopted, after the nickel salt solution and the aluminum salt solution are mixed in a ratio of 3:1 to 5:1 in a nickel-aluminum molar ratio, a precipitation agent is added to adjust the pH to 8 to 10, and after continuing to stir and crystallize at 50-70°C for 18-24h, after suction filtration, washing and drying, the NiAl catalyst obtained can efficiently catalyze nitrobenzene to prepare N-ethylaniline in a one-pot process, and the nitrobenzene conversion rate is more than 69.8%, and the selectivity of N-ethylaniline reaches more than 95.3%. Wherein, after the nickel salt solution and the aluminum salt solution are mixed in a ratio of 4:1 in a nickel-aluminum molar ratio, a precipitation agent is added to adjust the pH to 10, and after continuing to stir and crystallize at 70°C for 24h, after suction filtration, washing and drying, the catalytic performance of the NiAl catalyst obtained is optimal, the nitrobenzene conversion rate is 88.9%, and the selectivity of N-ethylaniline reaches 98.2%.
[0073] By comparing Example 2 and Comparative Examples 1 to 3 in Table 1, it can be seen that among the different loaded active metals, the performance of the catalyst Ni4Al1 is significantly better than that of the catalysts Cu4Al1, Mo4Al1 and Fe4Al1.
[0074] from Figure 1 It can be seen from the results that the NiAl catalyst prepared by the present invention not only has excellent catalytic performance, but also has stable performance and can maintain high catalytic performance within 40 hours.
[0075] The Ni4Al1 catalyst prepared in Example 2 was Figure 2 The classic petal-like structure of nanosheet stacking is shown, and no obvious metal particles are observed. Figure 3 As shown, Ni metal nanoparticles with an average particle size of about 5 nm were obtained. Ni species are active sites in the one-pot reaction of nitrobenzene to prepare N-ethylaniline, so that the reduced Ni4Al1 catalyst exhibits excellent activity in this reaction.
[0076] The above detailed description of the technical solution of the present application is made through specific embodiments, which cannot be used to limit the protection scope of the present application. All equivalent replacements, modifications and modifications made according to the technical concept and spirit of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing a NiAl catalyst, characterized in that: The following steps are involved: (1) After mixing the nickel salt solution and the aluminum salt solution, a precipitant is added to adjust the pH, and stirring and crystallization are continued to obtain a mixed solution; (2) The obtained mixed solution is filtered, washed and dried to obtain a NiAl catalyst.
2. The method for preparing a NiAl catalyst according to claim 1, wherein The molar ratio of Ni to Al in the NiAl catalyst is 3:1 to 5:1, preferably 4:
1.
3. The preparation method of NiAl catalyst according to claim 1, characterized in that In step (1), the nickel salt is selected from one or more of nickel hydroxide, nickel nitrate, nickel oxide and nickel sulfate, preferably nickel nitrate hexahydrate; The aluminum salt is selected from one or more of aluminum nitrate and aluminum sulfate, and is preferably aluminum nitrate nonahydrate.
4. The method for preparing a NiAl catalyst according to claim 1, wherein In step (1), the precipitant is selected from one or more of anhydrous sodium carbonate, aqueous ammonia and sodium hydroxide; the precipitant is added to adjust the pH to 8-10, preferably to 10.
5. The method for preparing the NiAl catalyst according to claim 1, characterized in that: In step (1), the crystallization temperature is 50-70° C., and the crystallization time is 12-24 h. Preferably, the crystallization temperature is 70° C., and the crystallization time is 24 h.
6. A NiAl catalyst, characterized in that The NiAl catalyst is prepared according to the preparation method of the NiAl catalyst according to any one of claims 1 to 5.
7. Use of a NiAl catalyst in the preparation of N-ethylaniline, characterized in that: The NiAl catalyst is prepared according to the preparation method of the NiAl catalyst according to any one of claims 1 to 5, and is used for preparing N-ethylaniline from nitrobenzene in one pot, comprising the following steps: NiAl catalyst, dodecane, nitrobenzene and ethanol were added to the reaction kettle in sequence, and the kettle was sealed; argon gas was introduced for ventilation and stirring, and then hydrogen gas was introduced for ventilation, and then hydrogen gas was injected into the kettle, and the reaction was carried out at a constant temperature after heating to the reaction temperature.
8. Use of the NiAl catalyst according to claim 7 in the preparation of N-ethylaniline, characterized in that: The amount of dodecane added is 0.5-1 mL, the amount of nitrobenzene added is 1.5-2.5 mL, the amount of ethanol added is 20-25 mL, the amount of NiAl catalyst added is 0.2-0.3 g, and the pressure of injected hydrogen is 1.15-1.25 MPa.
9. Use of the NiAl catalyst according to claim 7 in the preparation of N-ethylaniline, characterized in that: The reaction temperature is 110-130° C., and the reaction time is 5-8 hours.
10. Use of the NiAl catalyst according to claim 7 in the preparation of N-ethylaniline, characterized in that: The NiAl catalyst needs to be reduced before use, the reducing atmosphere is hydrogen, and the reducing temperature is 500°C.