Basic cupric carbonate-based composite catalyst for synthesizing N-methylaniline through N methylation of aniline and preparation method of basic cupric carbonate-based composite catalyst

Abstract

The invention relates to the technical field of catalysts for synthesizing N-methylaniline, in particular to a basic cupric carbonate based composite catalyst for synthesizing N-methylaniline through N methylation of aniline and a preparation method of the basic cupric carbonate based composite catalyst. The selectivity of a conventional copper-based catalyst to N-methylaniline in a reaction for preparing N-methylaniline through N methylation of aniline is difficult to reach 90% or above. Aiming at the technical problem, the invention provides the basic cupric carbonate-based composite catalyst for synthesizing N-methylaniline through N methylation of aniline, the structural formula of the basic cupric carbonate-based composite catalyst can be represented as CuM (OH) x (CO3) y, M in the structural general formula comprises one or more of metal elements of zinc, aluminum, chromium, lanthanum and manganese, and by optimizing the composition of the metal elements in the catalyst and the pH value in the coprecipitation process, the N-methylaniline can be synthesized. The basic cupric carbonate-based composite catalyst with a relatively good catalytic effect is obtained, and obvious inactivation is not found when the basic cupric carbonate-based composite catalyst can stably and continuously run for 1000 hours under the condition of keeping a relatively high N-methylaniline yield.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts for N-methylaniline synthesis, and in particular to a basic copper carbonate-based composite catalyst used for synthesizing N-methylaniline through N-methylation of aniline and a preparation method thereof. Background Art

[0002] N-methylaniline, the N-methylation product of aniline, is a very important organic intermediate, which is widely used in the production of chemical industrial products such as pesticides, medicines, dyes and other fine chemicals. It is mainly used as an important intermediate for dyes, pesticides and surfactants and a new generation of gasoline antiknock agent.

[0003] Although a series of copper-based catalysts have been developed for the N-methylation of aniline, and these catalysts have performed well in improving the conversion rate of aniline, they still need to be improved in improving the selectivity of N-methylaniline. Under the catalysis of conventional copper-based catalysts, the selectivity of N-methylaniline is difficult to reach more than 90%. Summary of the invention

[0004] The problem in the prior art is that it is difficult for conventional copper-based catalysts to achieve a selectivity of more than 90% for N-methylaniline in the N-methylation of aniline to N-methylaniline. In view of the above technical problems, the present invention provides a basic copper carbonate-based composite catalyst for the synthesis of N-methylaniline from aniline N-methylation, the structural formula of which can be expressed as CuM(OH)x(CO 3 )y, by regulating the amount of basic copper carbonate in the catalyst precursor, the problem of low conversion rate and selectivity of the existing catalytic conversion of aniline to N-methylaniline is overcome, and the final conversion rate of aniline and selectivity of N-methylaniline can reach 99%. The specific preparation method comprises the following steps:

[0005] (1) dissolving a water-soluble metal copper salt and a water-soluble M salt simultaneously in deionized water, wherein the metal M is one or more of zinc, aluminum, chromium, lanthanum, and manganese, to obtain a metal salt aqueous solution;

[0006] (2) heating the metal salt aqueous solution to a coprecipitation temperature and stirring at a constant temperature, continuously adding a coprecipitant dropwise into the metal salt aqueous solution while stirring, and stopping the addition of the coprecipitant and stirring when the pH of the solution is 5-10 to obtain a precipitation mother liquor, aging the precipitation mother liquor at a constant temperature of 70° C., cooling, filtering, washing with water, drying, and then low-temperature roasting to obtain a basic carbonate precursor;

[0007] (3) The obtained basic carbonate precursor is tableted and granulated to obtain the above-mentioned basic copper carbonate-based composite catalyst with a desired particle size.

[0008] Preferably, the water-soluble M salt includes one or more of M nitrate, carbonate, halide and acetate.

[0009] Preferably, the coprecipitant includes one or more of ammonia water, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

[0010] Preferably, the coprecipitation temperature is 20-90°C.

[0011] Preferably, the average particle size of the basic copper carbonate-based composite catalyst is 20-80 meshes.

[0012] Preferably, the low-temperature calcination temperature is 200-800° C., and the calcination time is 2-24 hours.

[0013] Preferably, the water-soluble M salt is one or more of water-soluble zinc, aluminum, chromium, lanthanum and manganese salts.

[0014] A method for preparing N-methylaniline adopts the basic copper carbonate-based composite catalyst obtained as a catalyst for preparing N-methylaniline by reacting aniline with methanol.

[0015] Preferably, the temperature for the reaction of aniline and methanol is 100-400° C., the reaction pressure is 0.1-4 MPa, and the molar ratio of aniline to methanol is 1:0.5-2.

[0016] The present invention has the following beneficial effects:

[0017] (1) The basic copper carbonate-based composite catalyst obtained by the present invention has good catalytic stability. After 1000 hours of catalytic reaction, no obvious deactivation phenomenon occurs, the service life is long, and the conversion rate of aniline can easily reach more than 90%;

[0018] (2) In the N-methylation reaction of aniline and methanol, the basic copper carbonate-based composite catalyst obtained by the present invention has good selectivity for N-methylaniline, easily reaching more than 99%, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : is a catalytic effect diagram of the basic copper carbonate-based composite catalyst obtained in Example 1.

[0020] Figure 2 : It is the XRD diffraction comparison diagram of Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the examples. However, it should be understood that the following examples are only illustrative of the embodiments of the present invention, and are not intended to limit the scope of the present invention.

[0022] Example 1

[0023] (1) Weigh 19.78 g Cu(NO 3 ) 2 ·3H 2 O, 11.03 g Zn(NO 3 ) 2 6H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O is added into 200 mL of deionized water, and stirred to mix evenly to obtain a metal salt aqueous solution;

[0024] (2) heating the metal salt aqueous solution to 70° C. and stirring at a constant temperature, and continuously dropping (dropping speed of about 1-2 drops / s) a coprecipitant into the metal salt aqueous solution while stirring, and when the pH of the solution is 6, stopping the dropping of the coprecipitant and stirring to obtain a precipitation mother liquor, and aging the precipitation mother liquor at a constant temperature of 70° C. for 12 h and cooling to room temperature, and then vacuum filtering the obtained precipitate liquid, washing with water until the pH of the filtrate is 7, and then placing it in an oven at 80° C. for 12 h for drying, and then low-temperature roasting the obtained solid product (roasting temperature is 200° C., roasting in air for 3 h) to obtain a basic carbonate precursor;

[0025] (3) The obtained basic carbonate precursor was transferred to a tablet press, and a disposable mold (polytetrafluoroethylene ring) was used to maintain the pressure at 25 MPa for 15 minutes. After the pressure was released, the precursor was taken out, ground in a mortar, and sieved to obtain a basic copper carbonate-based composite catalyst with a particle size of 40-80 mesh.

[0026] Example 1 The preparation method of the coprecipitant is to mix 15.59 g Na 2 CO 3 Completely dissolve in 200 mL of deionized water.

[0027] Example 2 is the same as Example 1, except that in step (1) of Example 2, 15.78 g Cu(NO 3 ) 2 ·3H 2 O, 15.29g Zn(NO 3 ) 2 6H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0028] Example 3 is the same as Example 1, except that in step (1) of Example 3, 11.78 g Cu(NO 3 ) 2 ·3H2 O, 18.29g Zn(NO 3 ) 2 6H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0029] Example 4 is the same as Example 1, except that in step (1) of Example 4, 19.78 g Cu(NO 3 ) 2 ·3H 2 O, 11.03 g Zn(NO 3 ) 3· 5H 2 O, 2.27 g Cr(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0030] Example 5 is the same as Example 1, except that in step (1) of Example 5, 15.78 g Cu(NO 3 ) 2 ·3H 2 O, 15.29g Zn(NO 3 ) 3· 5H 2 O, 2.27 g Cr(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0031] Example 6 is the same as Example 1, except that in step (1) of Example 6, 11.78 g Cu(NO 3 ) 2 ·3H 2 O, 18.29 g Zn(NO 3 ) 3· 5H 2 O, 2.27 g Cr(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0032] Example 7 is the same as Example 1, except that in step (1) of Example 7, 19.78 g Cu(NO 3) 2 ·3H 2 O, 11.03 g Cr(NO 3 ) 3 9H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0033] Example 8 is the same as Example 1, except that in step (1) of Example 8, 15.78 g Cu(NO 3 ) 2 ·3H 2 O, 15.29 g Cr(NO 3 ) 3 9H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0034] Example 9 is the same as Example 1, except that in step (1) of Example 9, 11.78 g Cu(NO 3 ) 2 ·3H 2 O, 18.29 g Cr(NO 3 ) 3 9H 2 O, 2.27 g Al(NO 3 ) 3 9H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0035] Example 10 is the same as Example 1, except that in step (1) of Example 10, 19.78 g Cu(NO 3 ) 2 ·3H 2 O, 10.29 g Zn(NO 3 ) 3· 5H 2 O, 1.27gCr(NO 3 ) 3 9H 2 O, 2.32 g Mn(NO 3 ) 2 ·H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0036] Example 11 is the same as Example 1, except that in step (1) of Example 11, 11.78 g Cu(NO 3 ) 2 ·3H 2 O, 17.29 g Zn(NO 3 ) 3· 5H 2 O, 1.27 g Cr(NO 3 ) 3 9H 2 O, 2.32 g Mn(NO 3 ) 2 ·H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0037] Example 12 is the same as Example 1, except that in step (1) of Example 12, 19.78 g Cu(NO 3 ) 2 ·3H 2 O, 10.29 g Zn(NO 3 ) 3· 5H 2 O, 1.27 g Cr(NO 3 ) 3 9H 2 O, 2.32 g La(NO 3 ) 3 6H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0038] Example 13 is the same as Example 1, except that in step (1) of Example 13, 11.78 g Cu(NO 3 ) 2 ·3H 2 O, 17.29 g Zn(NO 3 ) 3· 5H 2 O, 1.27 g Cr(NO 3 ) 3 9H 2 O, 2.32 g La(NO 3 ) 3 6H 2 O was added into 200 mL of deionized water and stirred to mix well to obtain a metal salt aqueous solution.

[0039] Comparative Example 1 is the same as Example 1, except that the pH value of the solution is 7 when the dropwise addition of the coprecipitant is stopped in step (2) of Comparative Example 1.

[0040] Comparative Example 2 is the same as Example 1, except that the pH value of the solution is 8 when the dropwise addition of the coprecipitant is stopped in step (2) of Comparative Example 2.

[0041] The catalytic activity evaluation results of the catalysts obtained in the above examples and comparative examples of the present invention are shown in Table 1.

[0042] Catalytic activity evaluation method: Weigh 0.5g of basic copper carbonate-based composite catalyst powder and put it into a vertically placed quartz reaction tube with an inner diameter of 14mm. The packing density of the basic copper carbonate-based composite catalyst in the quartz tube reactor is 1.15g / mL. The quartz tube reactor is heated by an electric heating reactor. Under normal pressure, the temperature of the quartz reaction tube is raised to 210°C. Aniline and methanol are mixed in a molar ratio of 1:1.05 to obtain a solution that is heated and vaporized by a preheater. Then, the solution is continuously introduced from the upper part of the quartz reaction tube (gas space velocity is 50mL / min). The gas flow direction is vertically downward, passing through the bottom of the quartz reaction tube, and then condensed and liquefied by a condenser into a gas-liquid separator. The liquid is collected for sampling and chromatographic analysis. Sampling and analysis are performed every 8 hours, and the average conversion rate and selectivity are calculated respectively (the specific test results are shown in Table 1 and Table 1). The curve of the catalytic stability of the basic copper carbonate-based composite catalyst obtained in Example 1 is shown in the attached manual. Figure 1 shown.

[0043] The XRD diffraction patterns of the catalysts obtained in Example 1 and Comparative Examples 1-2 are shown in the attached specification. Figure 2 shown.

[0044] Table 1

[0045] Example Conversion rate (aniline) / % Selectivity (N-methylaniline) / % Example 1 99.8 99.9 Example 2 94.2 99.4 Example 3 93.5 99.5 Example 4 98.1 99.9 Example 5 94.1 99.6 Example 6 91.5 99.5 Example 7 85.9 99.6 Example 8 81.2 99.2 Example 9 80.5 91.8

[0046] Table 1

[0047] Example Conversion rate (aniline) / % Selectivity (N-methylaniline) / % Example 10 98.5 99.9 Embodiment 11 98.1 99.7 Example 12 98.2 99.1 Example 13 94.6 99.5 Comparative Example 1 56.2 86.2 Comparative Example 2 62.8 78.8

[0048] It can be seen from Table 1 that the metal element composition of the basic copper carbonate composite catalyst and the pH of the coprecipitation during the preparation process will affect the catalytic activity of the basic copper carbonate composite catalyst obtained. The experimental results show that the optimal coprecipitation pH=6.

[0049] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline from aniline N-methylation, characterized in that: The following steps are involved: (1) dissolving a water-soluble metal copper salt and a water-soluble M salt in deionized water to obtain a metal salt aqueous solution; (2) heating the metal salt aqueous solution to a coprecipitation temperature and stirring at a constant temperature, continuously adding a coprecipitant dropwise into the metal salt aqueous solution while stirring, and stopping the addition of the coprecipitant and stirring when the pH of the solution is 5-10 to obtain a precipitation mother liquor, aging the precipitation mother liquor at a constant temperature of 70° C., cooling, filtering, washing with water, drying, and then low-temperature roasting to obtain a basic carbonate precursor; (3) The obtained basic carbonate precursor is tableted and granulated to obtain a basic copper carbonate-based composite catalyst with a desired particle size.

2. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The water-soluble M salt includes one or more of M nitrate, carbonate, halide and acetate.

3. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The coprecipitant includes one or more of ammonia water, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide.

4. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The coprecipitation temperature is 20-90°C.

5. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The average particle size of the basic copper carbonate-based composite catalyst is 20-80 meshes.

6. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The temperature of low-temperature roasting is 200-800°C, and the roasting time is 2-24h.

7. The method for preparing a basic copper carbonate-based composite catalyst for synthesizing N-methylaniline by N-methylation of aniline according to claim 1, characterized in that: The water-soluble M salt is one or more of water-soluble zinc, aluminum, chromium, lanthanum and manganese salts.

8. A method for preparing N-methylaniline, characterized in that: The basic copper carbonate-based composite catalyst obtained according to any one of claims 1 to 7 is used as a catalyst for the reaction of aniline and methanol to prepare N-methylaniline.

9. The method for preparing N-methylaniline according to claim 8, characterized in that: The reaction temperature of aniline and methanol is 100-400°C, the reaction pressure is 0.1-4MPa, and the molar ratio of aniline to methanol is 1:0.5-2.

Images