Preparation method of N-methylaniline

Abstract

The invention provides a preparation method of N-methylaniline, and relates to the technical field of synthesis of N-methylaniline. The fixed bed reactor is adopted, under the condition that the specific catalyst exists, aniline, carbon dioxide, carbon monoxide and hydrogen are mixed and react to prepare N-methylaniline, the final conversion rate of aniline can reach 98% or above, and the N-methylaniline product yield is high.

Description

Technical Field

[0001] The invention relates to the technical field of N-methylaniline synthesis, and in particular to a method for preparing N-methylaniline. Background Art

[0002] N-methylaniline is a widely used fine chemical product, mainly used as an important intermediate for dyes, pesticides and surfactants and a new generation of gasoline antiknock agent. The methylating agents used in the N-methylation process of traditional aniline are generally carbene precursors and electrophilic reagents, such as iodomethane, methyl trifluorate, diazomethane, dimethyl sulfate and other high-risk toxic carcinogenic compounds. Therefore, the preparation method using the above reagents will not only produce many by-products, but also have a great impact on human health and environmental protection. In addition, other preparation methods for catalytic N-methylation reactions have also been reported, such as the Eschweiler-Clarke reduction amination commonly used in laboratories, the N-methylation reaction of dimethyl carbonate, carbon dioxide, formic acid, dimethyl sulfoxide, etc. as carbon sources, and the hydrogenation reduction of carbamates. However, the above methods still have many shortcomings, for example, toxic formaldehyde, polyformaldehyde, or reducing agents such as silane and hydrogen or a large amount of zeolite should be added.

[0003] Therefore, finding a sustainable, atom-economical, and environmentally friendly carbon source to achieve N-methylation reaction is particularly important for the efficient preparation of N-methylaniline. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing N-methylaniline, which utilizes a specific catalyst to achieve efficient preparation of N-methylaniline.

[0005] The preparation method of N-methylaniline of the present invention is as follows:

[0006] Aniline is mixed with carbon dioxide, carbon monoxide and hydrogen, and reacted under the condition of catalyst to prepare N-methylaniline.

[0007] Furthermore, the reaction is carried out in a pressurized fixed-bed continuous flow reactor.

[0008] Furthermore, the particle size of the catalyst is 20 to 80 meshes.

[0009] Furthermore, the reaction pressure is 1-10 MPa, and the reaction temperature is 100°C-400°C.

[0010] Furthermore, the molar ratio of the mixed gas is n(H2):n(CO2):n(CO)=(2-20):1:(1-10), the gas hourly velocity (GHSV) is 3000-40000 mL / (g·h), and the aniline hourly velocity (LHSV) is 0.1-20 h-1 .

[0011] Furthermore, the catalyst is CuOxZnOyX, wherein the Cu content is 0 to 90 wt%.

[0012] Furthermore, X is one or more of Al2O3, SiO2, ZrO2, MnO2, TiO2, La2O3, and Cr2O3.

[0013] The present invention also provides a method for preparing the catalyst, which specifically comprises the following steps:

[0014] S1, dissolving the Cu salt, Zn salt and the salt of the X metal salt precursor in water to obtain a metal salt aqueous solution;

[0015] S2, adding a precipitant aqueous solution to the metal salt aqueous solution for coprecipitation;

[0016] S3, washing, drying and then calcining the precipitate to obtain a catalyst for the synthesis of N-methylaniline.

[0017] Furthermore, the salt is one or more of nitrate, sulfate, acetate, and halide.

[0018] Furthermore, the concentration of the metal salt aqueous solution is 0.01-2 mol / L.

[0019] Furthermore, the precipitant is one or more of sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

[0020] Furthermore, the concentration of the precipitant aqueous solution is 0.1-3 mol / L.

[0021] Furthermore, the volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is 1:(1-500).

[0022] Furthermore, the coprecipitation temperature is 30° C. to 90° C., and the coprecipitation pH is 6 to 12. The present invention does not strictly limit the coprecipitation time, and generally speaking, precipitation can be completed in 4 to 8 hours.

[0023] Furthermore, the pH of the filtrate after washing is 7-8.

[0024] Furthermore, the drying temperature is 60° C. to 300° C., and the drying time is 4 to 24 hours.

[0025] Furthermore, the calcination temperature is 200° C. to 800° C., and the calcination time is 2 to 24 hours.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are:

[0027] The present invention uses a mixed gas of carbon dioxide, carbon monoxide and hydrogen to react with aniline, which changes the previous method of preparing N-alkylated products using raw materials such as alcohols and alkyl halides, improves the problems of high temperature and high pressure, more side reactions, equipment corrosion and environmental pollution in the reaction process to a certain extent, and helps alleviate the greenhouse gas effect. At the same time, water is the only by-product in the reaction process, making the reaction process more environmentally friendly. DETAILED DESCRIPTION

[0028] The technical solution provided by the present invention is further described below in conjunction with embodiments.

[0029] Example 1

[0030] Weigh 6mmol copper nitrate trihydrate, 3mmol zinc nitrate hexahydrate and 1mmol aluminum nitrate nonahydrate solids respectively and place them in a 500mL eggplant-shaped bottle, add 200mL distilled water to dissolve the drugs, then weigh 11.6mmol sodium carbonate and place them in a 500mL eggplant-shaped bottle, add 150mL distilled water to dissolve the drugs, transfer the sodium carbonate solution to a 250mL dropping funnel after complete dissolution, and slowly add sodium carbonate aqueous solution to the nitrate solution, stirring for 3 to 4 hours, then place it in an oil bath pot at 70°C for aging for 12 hours, filter and wash until the pH value of the filtrate is 7, and place the filter cake in an oven at 80°C for 12 hours. After drying, heat it to 400°C in a muffle furnace at a heating rate of 5°C / min and calcine for 4 hours. The catalyst is pressed into tablets and granulated to screen out solid small particles of 20 to 40 meshes, and the obtained CuZnAlO x (6:3:1) catalyst.

[0031] Powdered catalyst is tableted and granulated: the catalyst is transferred to a tablet press, and a disposable mold (polytetrafluoroethylene ring) is used to maintain the pressure at 25 MPa for 15 minutes. After the pressure is released, the catalyst is taken out and ground in a mortar to obtain catalyst particles of 40 to 80 mesh.

[0032] The catalyst activity was evaluated using a fixed bed evaluation device. 0.5 g of the granulated catalyst was weighed and loaded into a quartz reaction tube with an inner diameter of 15 mm. The catalyst was reduced in situ at 300 °C in pure H2 at normal pressure for 3 h. The system pressure of the device was then adjusted to 4 MPa, the temperature to 210 °C, and the raw gas n(H2):n(CO2):n(CO)=2:1:1 was introduced, the gas space velocity was 6000 mL / (h·g), and the LHSV(AN)=0.3 h -1 .

[0033] Example 2

[0034] The metal salt used in the catalyst preparation is 6 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of manganese nitrate solution. Other preparation and evaluation steps are the same as those in Example 1.

[0035] Example 3

[0036] The metal salts used in the catalyst preparation are 6 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of lanthanum nitrate hexahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0037] Example 4

[0038] The metal salt used in the catalyst preparation is 6 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of titanyl sulfate. The other preparation and evaluation steps are the same as those in Example 1.

[0039] Example 5

[0040] The metal salt used in the catalyst preparation is 3 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 4 mmol of titanyl sulfate. The other preparation and evaluation steps are the same as those in Example 1.

[0041] Example 6

[0042] The metal salts used in the catalyst preparation are 3 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of chromium nitrate nonahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0043] Example 7

[0044] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol aluminum nitrate nonahydrate and 0.5 mmol manganese nitrate solution. Other preparation and evaluation steps are the same as those in Example 1.

[0045] Example 8

[0046] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol aluminum nitrate nonahydrate and 0.5 mmol lanthanum nitrate hexahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0047] Example 9

[0048] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol aluminum nitrate nonahydrate and 0.5 mmol chromium nitrate nonahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0049] Example 10

[0050] The metal salt used in the catalyst preparation is 6.5 mmol of copper nitrate trihydrate, 2 mmol of zinc nitrate hexahydrate, 2 mmol of aluminum nitrate nonahydrate and 0.5 mmol of titanyl sulfate. The other preparation and evaluation steps are the same as those in Example 1.

[0051] Embodiment 11

[0052] The metal salts used in the catalyst preparation are 5mmol of copper nitrate trihydrate and 10mmol of zinc nitrate hexahydrate. The catalyst was prepared by impregnation method. Specifically, 5g of SiO2 was weighed into a 500mL two-necked flask, and then 100mL of deionized water was added and stirred and dispersed evenly, and then the above metal salts were added. The temperature was maintained at 60°C and the stirring speed was 600r / min for 6h, and the solvent was removed by rotary evaporation. The obtained solid was dried at 60°C and calcined in air at 500°C for 3h to obtain a composite oxide catalyst. The other preparation and evaluation steps were the same as those in Example 1.

[0053] Example 12

[0054] The metal salts used in the catalyst preparation were 5 mmol of copper nitrate trihydrate and 5 mmol of zinc nitrate hexahydrate. The other preparation and evaluation steps were the same as those in Example 11.

[0055] Embodiment 13

[0056] The metal salts used in the catalyst preparation were 6 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of lanthanum nitrate hexahydrate. The other preparation and evaluation steps were the same as those in Example 11.

[0057] Embodiment 14

[0058] The metal salt used in the catalyst preparation is 6 mmol of copper nitrate trihydrate, 3 mmol of zinc nitrate hexahydrate and 1 mmol of zirconium nitrate pentahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0059] Embodiment 15

[0060] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol zirconium nitrate pentahydrate and 0.5 mmol manganese nitrate solution. Other preparation and evaluation steps are the same as those in Example 1.

[0061] Example 16

[0062] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol zirconium nitrate pentahydrate and 0.5 mmol lanthanum nitrate hexahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0063] Embodiment 17

[0064] The metal salts used in the catalyst preparation are 6.5 mmol copper nitrate trihydrate, 2 mmol zinc nitrate hexahydrate, 2 mmol zirconium nitrate pentahydrate and 0.5 mmol chromium nitrate nonahydrate. Other preparation and evaluation steps are the same as those in Example 1.

[0065] Embodiment 18

[0066] The metal salt used in the catalyst preparation is 6.5 mmol of copper nitrate trihydrate, 2 mmol of zinc nitrate hexahydrate, 2 mmol of zirconium nitrate pentahydrate and 0.5 mmol of titanyl sulfate. The other preparation and evaluation steps are the same as those in Example 1.

[0067] Comparative Example 1

[0068] The metal salt used in the catalyst preparation was 5 mmol of copper nitrate trihydrate, and the precipitant was 11 mmol of sodium carbonate. Other preparation and evaluation steps were the same as those in Example 1.

[0069] Comparative Example 2

[0070] The metal salt used in the catalyst preparation is 5 mmol of copper nitrate trihydrate and 5 mmol of zinc nitrate hexahydrate, and the precipitant is 11 mmol of sodium carbonate. Other preparation and evaluation steps are the same as those in Example 1.

[0071] Comparative Example 3

[0072] The metal salt used in the catalyst preparation was 5 mmol of copper nitrate trihydrate and 5 mmol of aluminum nitrate nonahydrate solid, and the precipitant was 11 mmol of sodium carbonate. The other preparation and evaluation steps were the same as those in Example 1.

[0073] Comparative Example 4

[0074] The metal salt used in the catalyst preparation is 5 mmol of copper nitrate trihydrate and 5 mmol of zinc nitrate hexahydrate, and the precipitant is 11 mmol of sodium carbonate. The other preparation steps are the same as those in Example 1, except that the ratio of the raw gas in the catalyst evaluation process is different.

[0075] The catalyst activity was evaluated using a fixed bed evaluation device. 0.5 g of the granulated catalyst was weighed and loaded into a quartz reaction tube with an inner diameter of 15 mm. The catalyst was reduced in situ at 300 °C in pure H2 at normal pressure for 3 h. The system pressure of the device was then adjusted to 4 MPa, the temperature to 210 °C, and the raw gas n(H2):n(CO2):n(CO)=1:1:1 was introduced, the gas space velocity was 6000 mL / (h·g), and the LHSV(AN)=0.3 h -1 .

[0076] The catalytic effects of the catalysts of the examples and comparative examples were tested using the conversion of aniline (AN) and the selectivity of N-methylaniline as indicators. The results are as follows:

[0077] Example catalyst Aniline conversion rate / % N-methylaniline selectivity / % Example 1 CuZnAlOx(6:3:1) 97.4 96.8 Example 2 CuZnMnOx(6:3:1) 95.2 95.5 Example 3 CuZnLaOx(6:3:1) 93.7 96.2 Example 4 CuZnTiOx(6:3:1) 94.2 94.7 Example 5 CuZnTiOx(3:3:4) 97.2 95.5 Example 6 CuZnCrOx(6:3:1) 83.6 91.3 Example 7 CuZnAlMnOx(6.5:2:1:0.5) 98.6 88.9 Example 8 CuZnAlLaOx(6.5:2:1:0.5) 97.8 92.1 Example 9 CuZnAlCrOx(6.5:2:1:0.5) 96.3 98.1 Example 10 CuZnAlTiOx(6.5:2:1:0.5) 95.1 97.8 Embodiment 11 <![CDATA[CuZnOx(1:2) / SiO2]]> 95.9 97.6 Example 12 <![CDATA[CuZnOx(1:1) / SiO2]]> 91.3 95.2 Embodiment 13 <![CDATA[CuZnLaOx(6:3:1) / SiO2]]> 96.8 95.7 Embodiment 14 CuZnZrOx(6:3:1) 95.7 92.8 Embodiment 15 CuZnZrMnOx(6.5:2:1:0.5) 92.1 93.1 Example 16 CuZnZrLaOx(6.5:2:1:0.5) 98.2 93.7 Embodiment 17 CuZnZrCrOx(6.5:2:1:0.5) 96.7 95.1 Embodiment 18 CuZnZrTiOx(6.5:2:1:0.5) 94.2 97.2 Comparative Example 1 CuO 3.2 9.4 Comparative Example 2 CuZnOx(1:1) 61.2 52.1 Comparative Example 3 CuAlOx(1:1) 41.2 48.3 Comparative Example 4 CuZnOx(1:1) 12.2 20.1

[0078] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing N-methylaniline, characterized in that: Here are the steps: Aniline is mixed with carbon dioxide, carbon monoxide and hydrogen, and reacted under the condition of catalyst to prepare N-methylaniline; The catalyst is CuOxZnOyX, wherein the Cu content is 0-90wt%; The X is one or more of Al2O3, SiO2, ZrO2, MnO2, TiO2, La2O3, and Cr2O3.

2. The preparation method according to claim 1, characterized in that: The particle size of the catalyst is 20 to 80 meshes.

3. The preparation method according to claim 1, characterized in that: The reaction pressure is 1-10Mpa, and the reaction temperature is 100°C-400°C.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the mixed gas is n(H2):n(CO2):n(CO)=(2-20):1:(1-10), the gas hourly velocity (GHSV) is 3000-40000 mL / (g·h), and the aniline hourly velocity (LHSV) is 0.1-20 h -1 .

5. The method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, dissolving the Cu salt, Zn salt and the salt of the X metal salt precursor in water to obtain a metal salt aqueous solution; S2, adding a precipitant aqueous solution to the metal salt aqueous solution for coprecipitation; S3, washing, drying and then calcining the precipitate to obtain a catalyst for the synthesis of N-methylaniline.

6. The preparation method according to claim 5, characterized in that: The concentration of the metal salt aqueous solution is 0.01-2 mol / L.

7. The preparation method according to claim 5, characterized in that: The volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is 1:(1-500).

8. The preparation method according to claim 5, characterized in that: The coprecipitation temperature is 30° C. to 90° C., and the coprecipitation pH is 6 to 12.

9. The preparation method according to claim 5, characterized in that: The drying temperature is 60° C. to 300° C., and the drying time is 4 to 24 hours.

10. The preparation method according to claim 5, characterized in that: The calcination temperature is 200° C. to 800° C., and the calcination time is 2 to 24 hours.