A basic copper carbonate-based composite catalyst for the N-methylation synthesis of N-methylaniline from aniline and its preparation method

Abstract

This invention relates to the field of catalysts for the synthesis of N-methylaniline, specifically to a basic copper carbonate-based composite catalyst for the N-methylation synthesis of N-methylaniline from aniline and its preparation method. Conventional copper-based catalysts struggle to achieve selectivity of over 90% for N-methylaniline during the N-methylation reaction. To address this problem, this invention provides a basic copper carbonate-based composite catalyst for the N-methylation synthesis of N-methylaniline from aniline, with the structural formula CuM(OH)x(CO3)y. In this general formula, M includes one or more of the metal elements zinc, aluminum, chromium, lanthanum, and manganese. By optimizing the composition of the metal elements in the catalyst and the pH during the co-precipitation process, a basic copper carbonate-based composite catalyst with relatively good catalytic performance was obtained. While maintaining a high yield of N-methylaniline, it can operate stably and continuously for 1000 hours without significant deactivation.

Description

Technical Field

[0001] This invention relates to the field of catalysts for the synthesis of N-methylaniline, specifically to a basic copper carbonate-based composite catalyst for the N-methylation synthesis of N-methylaniline from aniline and its preparation method. Background Technology

[0002] N-methylaniline, the N-methylated product of aniline, is a very important organic intermediate widely used in the production of chemical products such as pesticides, pharmaceuticals, dyes, and other fine chemicals. It is primarily used as an important intermediate in dyes, pesticides, and surfactants, and as a next-generation gasoline antiknock agent.

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

[0004] A problem with existing technologies is that conventional copper-based catalysts struggle to achieve a selectivity of over 90% for N-methylaniline during the N-methylation of aniline. To address this issue, this invention provides a basic copper carbonate-based composite catalyst for the synthesis of N-methylaniline from aniline via N-methylation. Its structural formula can be represented as CuM(OH)x(CO3)y. By controlling the amount of basic copper carbonate in the catalyst precursor, the low conversion rate and selectivity of existing aniline-to-N-methylaniline catalytic conversion methods are overcome, ultimately achieving a 99% conversion rate for aniline and a 99% selectivity for N-methylaniline. The specific preparation method includes the following steps:

[0005] (1) Dissolve a water-soluble copper metal 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 an aqueous solution of the metal salt.

[0006] (2) Heat the metal salt aqueous solution to the coprecipitation temperature and stir at a constant temperature. While stirring, continuously add the coprecipitant to the metal salt aqueous solution. When the pH of the solution is 5-10, stop adding the coprecipitant and stop stirring to obtain the precipitate mother liquor. The precipitate mother liquor is aged at a constant temperature of 70°C, cooled, filtered, washed with water, dried, and then calcined at a low temperature to obtain the basic carbonate precursor.

[0007] (3) The obtained basic carbonate precursor is granulated by compression to obtain the above-mentioned basic copper carbonate-based composite catalyst with the required particle size.

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

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

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

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

[0012] Preferably, the low-temperature calcination temperature is 200-800℃, and the calcination time is 2-24h.

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

[0014] A method for preparing N-methylaniline, wherein the above-obtained basic copper carbonate-based composite catalyst is used as a catalyst for the reaction of aniline with methanol to produce N-methylaniline.

[0015] Preferably, the reaction temperature of aniline and methanol is 100-400℃, the reaction pressure is 0.1-4MPa, 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 occurred. It has a long service life and the conversion rate of aniline is easy to obtain more than 90%.

[0018] (2) In the N-methylation reaction of aniline and methanol, the basic copper carbonate-based composite catalyst obtained in this invention has good selectivity for N-methylaniline, which can easily reach more than 99%, and has good market prospects. Attached Figure Description

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

[0020] Figure 2 : These are XRD diffraction comparison diagrams of Example 1 and Comparative Examples 1-2. Detailed Implementation

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

[0022] Example 1

[0023] (1) Weigh 19.78g Cu(NO3)2·3H2O, 11.03g Zn(NO3)2·6H2O and 2.27g Al(NO3)3·9H2O and add them to 200mL of deionized water. After stirring and mixing evenly, a metal salt aqueous solution is obtained.

[0024] (2) Heat the metal salt aqueous solution to 70°C and stir at a constant temperature. While stirring, continuously add a coprecipitant (dropping rate of about 1-2 drops / s) to the metal salt aqueous solution. When the pH of the solution is 6, stop adding the coprecipitant and stop stirring to obtain the precipitate mother liquor. The precipitate mother liquor is aged at 70°C for 12 hours and then cooled to room temperature. The obtained precipitate is vacuum filtered and washed with water until the pH of the filtrate is 7. Then it is placed in an oven at 80°C for 12 hours to dry. Then the obtained solid product is calcined at low temperature (calcination temperature is 200°C, calcination in air for 3 hours) to obtain the 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 depressurization, it 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] In Example 1, the co-precipitant was prepared by completely dissolving 15.59 g of Na2CO3 in 200 mL of deionized water.

[0027] Example 2 is the same as Example 1, except that in Example 2, step (1) involves weighing 15.78g Cu(NO3)2·3H2O, 15.29g Zn(NO3)2·6H2O, and 2.27g Al(NO3)3·9H2O and adding them to 200mL of deionized water. After stirring and mixing evenly, an aqueous solution of metal salt is obtained.

[0028] Example 3 is the same as Example 1, except that in Example 3, step (1) involves weighing 11.78g Cu(NO3)2·3H2O, 18.29g Zn(NO3)2·6H2O, and 2.27g Al(NO3)3·9H2O and adding them to 200mL of deionized water. After stirring and mixing evenly, an aqueous solution of metal salt is obtained.

[0029] Example 4 is the same as Example 1, except that step (1) in Example 4 involves weighing 19.78g Cu(NO3)2·3H2O and 11.03g Zn(NO3). 3· 5H2O and 2.27g Cr(NO3)3·9H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0030] Example 5 is the same as Example 1, except that step (1) in Example 5 involves weighing 15.78g Cu(NO3)2·3H2O and 15.29g Zn(NO3). 3· 5H2O and 2.27g Cr(NO3)3·9H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0031] Example 6 is the same as Example 1, except that step (1) in Example 6 involves weighing 11.78g Cu(NO3)2·3H2O and 18.29g Zn(NO3). 3· 5H2O and 2.27g Cr(NO3)3·9H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0032] Example 7 is the same as Example 1, except that in Example 7, step (1) involves weighing 19.78g Cu(NO3)2·3H2O, 11.03g Cr(NO3)3·9H2O, and 2.27g Al(NO3)3·9H2O and adding them to 200mL of deionized water. After stirring and mixing evenly, an aqueous solution of the metal salt is obtained.

[0033] Example 8 is the same as Example 1, except that in Example 8, step (1) involves weighing 15.78g Cu(NO3)2·3H2O, 15.29g Cr(NO3)3·9H2O, and 2.27g Al(NO3)3·9H2O and adding them to 200mL of deionized water. After stirring and mixing evenly, an aqueous solution of the metal salt is obtained.

[0034] Example 9 is the same as Example 1, except that in Example 9, step (1) is to weigh 11.78g Cu(NO3)2·3H2O, 18.29g Cr(NO3)3·9H2O and 2.27g Al(NO3)3·9H2O and add them to 200mL of deionized water. After stirring and mixing evenly, a metal salt aqueous solution is obtained.

[0035] Example 10 is the same as Example 1, except that step (1) of Example 10 involves weighing 19.78g of Cu(NO3)2·3H2O and 10.29g of Zn(NO3). 3· 5H2O, 1.27gCr(NO3)3·9H2O, and 2.32gMn(NO3)2·H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0036] Example 11 is the same as Example 1, except that step (1) of Example 11 involves weighing 11.78g Cu(NO3)2·3H2O and 17.29g Zn(NO3). 3· 5H2O, 1.27g Cr(NO3)3·9H2O, and 2.32g Mn(NO3)2·H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0037] Example 12 is the same as Example 1, except that step (1) of Example 12 involves weighing 19.78g Cu(NO3)2·3H2O and 10.29g Zn(NO3). 3· 5H2O, 1.27g Cr(NO3)3·9H2O, and 2.32g La(NO3)3·6H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

[0038] Example 13 is the same as Example 1, except that step (1) of Example 13 involves weighing 11.78g Cu(NO3)2·3H2O and 17.29g Zn(NO3). 3· 5H2O, 1.27g Cr(NO3)3·9H2O, and 2.32g La(NO3)3·6H2O were added to 200mL of deionized water and stirred until homogeneous to obtain an aqueous solution of the metal salt.

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

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

[0042] Catalytic activity evaluation method: 0.5g of basic copper carbonate-based composite catalyst powder was weighed and placed in 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 was 1.15g / mL. The quartz tube reactor was heated by an electrically heated reactor at atmospheric pressure to 210℃. A solution obtained by mixing aniline and methanol at a molar ratio of 1:1.05 was preheated and vaporized, then continuously introduced from the top of the quartz reaction tube (gas hourly space velocity of 50mL / min) with the gas flow direction vertically downward, exiting from the bottom of the quartz reaction tube, and condensed and liquefied by a condenser before entering a gas-liquid separator. The liquid was collected for chromatographic analysis. Samples were taken and analyzed every 8 hours, and the average conversion rate and selectivity were calculated (specific test results are shown in Table 1 and Table 1 continued). The catalytic stability curve of the basic copper carbonate-based composite catalyst obtained in Example 1 is shown in the attached instruction manual. Figure 1 As shown.

[0043] The XRD diffraction patterns of the catalysts obtained in Example 1 and Comparative Examples 1-2 are shown in the appendix to the specification. Figure 2 As 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] Continued from Table 1

[0047] Example Conversion rate (aniline) / % Selectivity (N-methylaniline) / % Example 10 98.5 99.9 Example 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] Table 1 shows that the metal element composition of the basic copper carbonate composite catalyst and the pH of the co-precipitation process both affect the catalytic activity of the obtained basic copper carbonate composite catalyst. Experimental results indicate that the optimal co-precipitation pH is 6.

[0049] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a basic copper carbonate-based composite catalyst for the N-methylation synthesis of N-methylaniline from aniline, characterized in that, Includes the following steps: (1) Dissolve the water-soluble copper metal salt and the water-soluble M salt simultaneously in deionized water to obtain an aqueous solution of the metal salt; (2) Heat the metal salt aqueous solution to the coprecipitation temperature and stir at a constant temperature. While stirring, continuously add the coprecipitant to the metal salt aqueous solution. When the pH of the solution is 6, stop adding the coprecipitant and stop stirring to obtain the precipitate mother liquor. The precipitate mother liquor is aged at a constant temperature of 70°C, cooled, filtered, washed with water, dried, and then calcined at a low temperature to obtain the basic carbonate precursor. (3) The obtained basic carbonate precursor is granulated by compression to obtain a basic copper carbonate-based composite catalyst with the required particle size. The low-temperature calcination temperature is 200℃, and the calcination time is 3 hours; The water-soluble M salt is two or more of the following: water-soluble zinc, aluminum, chromium, lanthanum, and manganese salts.

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

3. The method for preparing a basic copper carbonate-based composite catalyst for the N-methylaniline synthesis of aniline according to claim 1, characterized in that, The coprecipitant includes one or more of ammonia, 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 the N-methylaniline synthesis of aniline according to claim 1, characterized in that, The coprecipitation temperature is 20-90℃.

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

6. A method for preparing N-methylaniline, characterized in that, The basic copper carbonate-based composite catalyst obtained according to any one of claims 1-5 is used as a catalyst for the reaction of aniline and methanol to produce N-methylaniline.

7. The method for preparing N-methylaniline according to claim 6, characterized in that, The reaction temperature of aniline with methanol is 100-400℃, the reaction pressure is 0.1-4MPa, and the molar ratio of aniline to methanol is 1:0.5-2.

Images