A catalyst for synthesizing 2,6-dimethylaniline and a preparation method and application thereof

Abstract

The application discloses a catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier, active metal Pd supported on the carrier and auxiliary metal; the auxiliary metal comprises auxiliary metal A and auxiliary metal B, the auxiliary metal A is one of K and Na, and the auxiliary metal B is at least two of Ba, Zn, Mg, Zr and La; the carrier is alumina; according to 100% of the total weight of the catalyst, the percentage of each component is as follows: 0.2-2% of the active metal Pd, 0.1-3% of the auxiliary metal A, 0.1-10% of the auxiliary metal B, and the balance is the carrier. Meanwhile, the application also discloses a preparation method of the catalyst and application of the catalyst in preparation of 2,6-dimethylaniline. The catalyst provided by the application is applied to continuous catalytic synthesis of 2,6-dimethylaniline from 2,6-dimethylphenol, the yield of the target product is higher, and the service life of the catalyst is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of 2,6-dimethylaniline preparation, and particularly relates to a catalyst for synthesizing 2,6-dimethylaniline and a preparation method and application thereof. BACKGROUND

[0002] 2,6-dimethylaniline is an important intermediate and can be used for producing pesticides, medicines or veterinary drugs, and is also widely used in the fields of dyes, inks and the like. 2,6-dimethylaniline can be prepared by nitration reduction of m-xylene, and a large amount of waste is generated in the production process. In the early 1980s, BASF Company developed a phenol gas-phase ammoniation method, which was prepared by using a new type of hydrogenation-dehydrogenation catalyst on the basis of the high-pressure high-temperature amination method test of Ethyl Company.

[0003] Pd metal catalyst is commonly used in the synthesis reaction of 2,6-dimethylaniline. Patent CN 102603537A discloses a production method of 2,6-dimethylaniline, and the catalyst used in the reaction is a composite catalyst composed of zirconium oxychloride, barium sulfate or barium hydroxide, aluminum oxide or aluminum nitrate and metal palladium. The catalyst process is applied to a batch reactor, and the continuous operation performance is poor, and the content of the auxiliary metal is high, which increases the production cost of the catalyst. Patent CN 1207329A discloses a preparation and application method of a 2,6-dimethylaniline catalyst. The catalyst is prepared by using aluminum oxide as a carrier, impregnating magnesium nitrate and aluminum nitrate to prepare magnesium aluminum spinel, and then impregnating palladium chloride. The yield of the obtained catalyst is generally low, and the selectivity is poor.

[0004] Meanwhile, with the development of domestic agriculture and fine chemical industry, the demand for 2,6-dimethylaniline is also increasing. Most of the domestic devices use traditional production processes, which have poor operation safety, many device leaks and serious environmental pollution, thereby leading to shutdown. At present, 2,6-dimethylaniline is commonly prepared by pressure ammoniation of 2,6-dimethylphenol in industry, and the process is continuous production, which generates little waste. However, the existing catalysts for amination reaction research still have the disadvantages of low selectivity and short service life, and therefore, it is necessary to develop a high-performance catalyst and production process for continuous catalytic preparation of 2,6-dimethylaniline. SUMMARY

[0005] In view of the defects of the prior art, the application provides a catalyst for synthesizing 2,6-dimethylaniline and a preparation method and application thereof. The acid-base property of the carrier is adjusted by using an alkaline metal, and the carrier is modified by using an auxiliary metal compound, so that the catalyst has higher activity, selectivity and stability.

[0006] A catalyst for synthesizing 2,6-dimethylaniline is composed of a carrier, an active metal Pd supported on the carrier and an auxiliary metal.

[0007] The auxiliary metal comprises auxiliary metal A and auxiliary metal B, the auxiliary metal A is one of K, Na, the auxiliary metal B is at least two of Ba, Zn, Mg, Zr, La; the carrier is alumina;

[0008] The percentage of each component is as follows: active metal Pd 0.2-2%, auxiliary metal A 0.1-3%, auxiliary metal B 0.1-10%, and the balance is the carrier, based on the total weight of the catalyst being 100%.

[0009] Preferably, the auxiliary metal B is at least one of Ba, Mg, Zr, La and Zn.

[0010] Preferably, the percentage of each component is as follows: active metal Pd 0.3-1%, auxiliary metal A 0.1-1%, auxiliary metal B 0.1-5%, and the balance is the carrier.

[0011] The preparation method of the catalyst for synthesizing 2,6-dimethylaniline comprises the following steps:

[0012] (1) the carrier is immersed in an alkaline impregnation solution containing auxiliary metal A, stirring during the immersion process, drying, and calcination; then the obtained carrier is immersed in a nitrate impregnation solution containing auxiliary metal B, stirring during the immersion process, drying, and calcination;

[0013] (2) adjust the pH of the active group palladium chloride solution to 1-4 to obtain an impregnation solution containing Pd, then add the carrier obtained in step (1) to the impregnation solution for immersion, stirring during the immersion process, then drying and calcination to obtain a catalyst precursor;

[0014] (3) reduce the catalyst precursor to obtain the catalyst.

[0015] Preferably, in step (2), the pH of the active group palladium chloride solution is adjusted with a sodium carbonate solution.

[0016] Preferably, the mass of the impregnation solution is 0.5-1 times that of the carrier, and the immersion time is 3-10h.

[0017] Preferably, the drying temperature is 80-120℃, and the calcination conditions are calcination at 400-600℃ for 2-8h.

[0018] Preferably, the reduction conditions are reduction in a hydrogen atmosphere at 200-300℃ for 5-40h, and the hydrogen flow rate is 50-500mL / min.

[0019] The method for preparing 2,6-dimethylaniline by using the catalyst provided by the application is as follows: the catalyst is loaded in a quartz tube of a fixed bed reactor, 2,6-dimethylphenol is used as raw material, hydrogen and ammonia are introduced, and the reaction is carried out at 180-230 DEG C under normal pressure, and the feeding line is heated and kept at 220 DEG C.

[0020] Preferably, the molar ratio of hydrogen to 2,6-dimethylphenol is 10-50, the molar ratio of ammonia to 2,6-dimethylphenol is 5-30, the mass space velocity of 2,6-dimethylphenol is 0.05-1 h -1 .

[0021] Advantages of the application:

[0022] (1) The basic metal is used to adjust the acid-base property of the carrier, which is beneficial to the timely desorption of reactants on the catalyst, and avoids the retention of the catalyst active sites, thereby avoiding deactivation. The carrier is modified by the auxiliary metal, lattice defects are formed, which is beneficial to the loading of the active metal, and the existence of the auxiliary metal can improve the electronic state of the catalyst, so that the catalyst has higher activity, selectivity and service life.

[0023] (2) The catalyst provided by the application can be applied to the continuous catalytic synthesis of 2,6-dimethylaniline from 2,6-dimethylphenol, the process is continuous and has high automation degree, the reaction process has less waste, and has good economic and social benefits.

[0024] (3) The catalyst provided by the application is applied to the continuous catalytic synthesis of 2,6-dimethylaniline from 2,6-dimethylphenol, the yield of the target product 2,6-dimethylaniline is higher, and the catalyst has good service life, which provides guidance for later industrial production. DETAILED DESCRIPTION

[0025] Example 1

[0026] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of an alumina carrier, an active metal Pd loaded on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is K, and the auxiliary metal B is Ba, Zr, or La; according to the total weight of the catalyst being 100%, the percentage of each component is as follows: Pd 0.5%, K 0.5%, Ba 2%, Zr 4%, La 0.2%, and the balance is the carrier.

[0027] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0028] (1) Take 50 g of alumina carrier, put it in 30 g of potassium hydroxide solution, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 5 h to obtain a K-doped carrier; then put the K-doped carrier into a mixed solution of 30 g of barium nitrate, lanthanum nitrate and zirconium nitrate, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 5 h to obtain an additive-treated carrier;

[0029] (2) Take 30 g of palladium chloride solution, adjust the pH of the active group Pd solution to 2 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 6 h, stir during the immersion process, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 3 h.

[0030] (3) Reduce the catalyst precursor obtained in step (2) under H2 atmosphere at 230°C for 20 h, with a hydrogen flow rate of 50 mL / min, to obtain the catalyst.

[0031] Example 2

[0032] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an additive metal A and an additive metal B; the additive metal A is K, and the additive metal B is Ba, Mg, and La; the percentage of each component is as follows, based on the total weight of the catalyst being 100%: Pd 0.5%, K 1%, Ba 2%, Mg 1%, La 0.5%, and the balance being the carrier.

[0033] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0034] (1) Take 50 g of alumina carrier, put it in 30 g of potassium hydroxide solution, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 5 h to obtain a K-doped carrier; then put the K-doped carrier into a mixed solution of 30 g of barium nitrate, lanthanum nitrate and zirconium nitrate, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 5 h to obtain an additive-treated carrier;

[0035] (2) Take 30 g of palladium chloride solution, adjust the pH of the active group Pd solution to 1.5 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 6 h, stir during the immersion process, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 450°C for 5 h;

[0036] (3) The catalyst precursor obtained in step (2) is reduced under H2 atmosphere at 280°C for 10 h, with a hydrogen flow rate of 500 mL / min, to obtain the catalyst.

[0037] Example 3

[0038] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is K, and the auxiliary metal B is Ba, Mg, and Zr; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 0.7%, K 0.3%, Ba 1%, Mg 0.5%, Zr 3%, and the balance being the carrier.

[0039] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0040] (1) 50 g of an alumina carrier is weighed, stirred in 30 g of a potassium hydroxide solution, impregnated and adsorbed for 5 h, then dried in an oven at 100°C, and the dried carrier is placed in a muffle furnace and calcined at 600°C for 3 h to obtain a K-doped carrier; then the K-doped carrier is stirred in a mixed solution of 30 g of barium nitrate, zirconium nitrate, and magnesium nitrate, impregnated and adsorbed for 5 h, then dried in an oven at 100°C, and the dried carrier is placed in a muffle furnace and calcined at 600°C for 3 h to obtain an auxiliary-treated carrier;

[0041] (2) 30 g of a palladium chloride solution is weighed, a 10% sodium carbonate solution is used to adjust the pH of the active Pd solution to 2.5, then the carrier treated in step (1) is added, impregnated for 4 h while stirring, then dried in an oven at 100°C, and the dried carrier is placed in a muffle furnace and calcined at 450°C for 5 h;

[0042] (3) The catalyst precursor obtained in step (2) is reduced under H2 atmosphere at 300°C for 5 h, with a hydrogen flow rate of 300 mL / min, to obtain the catalyst.

[0043] Example 4

[0044] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is K, and the auxiliary metal B is Ba and Zr; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 1%, K 0.1%, Ba 1%, Zr 5%, and the balance being the carrier.

[0045] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0046] (1) Take 50 g of alumina carrier, put it in 30 g of potassium hydroxide solution, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 5 h to obtain a K-doped carrier; then put the K-doped carrier into a mixed solution of 30 g of barium nitrate and zirconium nitrate, stir, immerse and adsorb for 5 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 4 h to obtain a carrier treated with additives;

[0047] (2) Take 30 g of palladium chloride solution, adjust the pH of the active group Pd solution to 3 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 4 h, stir during the immersion process, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 450°C for 5 h;

[0048] (3) Reduce the catalyst precursor obtained in step (2) under H2 atmosphere at 300°C for 5 h, with a hydrogen flow rate of 300 mL / min, to obtain the catalyst.

[0049] Example 5

[0050] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an additive metal A and an additive metal B; the additive metal A is K, and the additive metal B is Ba and La; the percentage of each component is as follows, based on the total weight of the catalyst being 100%: Pd 0.4%, K 0.1%, Ba 3%, La 0.5%, and the balance being the carrier.

[0051] 2. A method for preparing the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0052] (1) Take 50 g of alumina carrier, put it in 40 g of potassium hydroxide solution, stir, immerse and adsorb for 3 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 500°C for 4 h to obtain a K-doped carrier; then put the K-doped carrier into a mixed solution of 50 g of barium nitrate and lanthanum nitrate, stir, immerse and adsorb for 6 h, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 600°C for 5 h to obtain a carrier treated with additives;

[0053] (2) Take 40 g of palladium chloride solution, adjust the pH of the active group Pd solution to 4 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 3 h, stir during the immersion process, then put it in a 100°C oven to dry, and then put the dried carrier into a muffle furnace at 400°C for 6 h;

[0054] (3) The catalyst precursor obtained in step (2) is reduced under H2 atmosphere at 200°C for 40h, with a hydrogen flow rate of 50mL / min, to obtain the catalyst.

[0055] Example 6

[0056] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is Na, and the auxiliary metal B is Zr and La; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 0.5%, Na 0.5%, Zr 2%, La 0.3%, and the balance being the carrier.

[0057] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0058] (1) 50g of an alumina carrier is weighed, stirred in 30g of a sodium hydroxide solution, impregnated and adsorbed for 4h, then dried in an oven at 120°C, and the dried carrier is placed in a muffle furnace and calcined at 500°C for 5h to obtain a Na-doped carrier; then the Na-doped carrier is stirred in a mixed solution of 30g of zirconium nitrate and lanthanum nitrate, impregnated and adsorbed for 6h, then dried in an oven at 120°C, and the dried carrier is placed in a muffle furnace and calcined at 500°C for 4h to obtain an auxiliary-treated carrier;

[0059] (2) 40g of a palladium chloride solution is weighed, a 10% sodium carbonate solution is used to adjust the pH of the active Pd solution to 1.5, then the carrier treated in step (1) is added, impregnated for 6h with stirring, then dried in an oven at 100°C, and the dried carrier is placed in a muffle furnace and calcined at 500°C for 4h;

[0060] (3) The catalyst precursor obtained in step (2) is reduced under H2 atmosphere at 300°C for 5h, with a hydrogen flow rate of 50mL / min, to obtain the catalyst.

[0061] Example 7

[0062] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is K, and the auxiliary metal B is Zn, Ba, and Mg; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 2%, K 1%, Zn 0.1%, Ba 5%, Mg 4.9%, and the balance being the carrier.

[0063] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0064] (1) Take 50 g of alumina carrier, put it in 25 g of potassium hydroxide solution, stir, immerse and adsorb for 10 h, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 400°C for 8 h to obtain a K-doped carrier; then put the K-doped carrier into 25 g of a mixed solution of zinc nitrate, barium nitrate and magnesium nitrate, stir, immerse and adsorb for 10 h, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 400°C for 8 h to obtain a carrier treated with additives;

[0065] (2) Take 25 g of palladium chloride solution, adjust the pH of the active group Pd solution to 1 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 10 h, stir during the immersion process, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 400°C for 8 h.

[0066] (3) Reduce the catalyst precursor obtained in step (2) under H2 atmosphere at 230°C for 20 h, with a hydrogen flow rate of 200 mL / min, to obtain the catalyst.

[0067] Example 8

[0068] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an additive metal A and an additive metal B; the additive metal A is K, and the additive metal B is Zn and Zr; the percentage of each component is as follows, based on the total weight of the catalyst being 100%: Pd 0.5%, K 1%, Zn 1%, Zr 6%, and the balance being the carrier.

[0069] 2. A method for preparing the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0070] (1) Take 50 g of alumina carrier, put it in 50 g of potassium hydroxide solution, stir, immerse and adsorb for 10 h, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 600°C for 2 h to obtain a K-doped carrier; then put the K-doped carrier into 50 g of a mixed solution of zinc nitrate and zirconium nitrate, stir, immerse and adsorb for 10 h, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 600°C for 2 h to obtain a carrier treated with additives;

[0071] (2) Take 50 g of palladium chloride solution, adjust the pH of the active group Pd solution to 1 with 10% sodium carbonate solution, then add the carrier treated in step (1) to it, immerse for 10 h, stir during the immersion process, then put it in an oven at 80°C to dry, and then put the dried carrier into a muffle furnace at 600°C for 2 h.

[0072] (3) The catalyst precursor obtained in step (2) is reduced under H2atmosphere at 230°C for 20h, and the flow rate of hydrogen is 200mL / min, to obtain the catalyst.

[0073] Example 9

[0074] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is K, and the auxiliary metal B is Zn and Mg; the percentages of the components are as follows: Pd 0.5%, K 0.5%, Zn 1%, Mg 4%, and the balance is the carrier, based on the total weight of the catalyst being 100%.

[0075] The preparation method of the catalyst, in step (1), a mixed solution of zinc nitrate and magnesium nitrate is used, and the others are the same as in Example 2.

[0076] Example 10

[0077] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is Na, and the auxiliary metal B is Zn and La; the percentages of the components are as follows: Pd 0.3%, Na 1%, Zn 2%, La 0.5%, and the balance is the carrier, based on the total weight of the catalyst being 100%.

[0078] The preparation method of the catalyst, in step (1), a sodium hydroxide solution, a mixed solution of zinc nitrate and lanthanum nitrate is used, and the others are the same as in Example 8.

[0079] Example 11

[0080] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an auxiliary metal A and an auxiliary metal B; the auxiliary metal A is Na, and the auxiliary metal B is Zn and Ba; the percentages of the components are as follows: Pd 1%, Na 0.1%, Zn 0.05%, Ba 0.05%, and the balance is the carrier, based on the total weight of the catalyst being 100%.

[0081] The preparation method of the catalyst, in step (1), a sodium hydroxide solution, a mixed solution of zinc nitrate and barium nitrate is used, and the others are the same as in Example 8.

[0082] Comparative Example 1

[0083] Compared with Example 2, no auxiliary is contained, and the details are as follows:

[0084] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of an alumina carrier, and an active metal Pd supported on the carrier; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 0.5%, and the balance being the carrier.

[0085] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0086] (1) 50 g of an alumina carrier is weighed and placed in a muffle furnace for calcination at 500°C for 7 h to obtain a calcined carrier;

[0087] (2) 30 g of a palladium chloride solution is weighed, a 10% sodium carbonate solution is used to adjust the pH of the active Pd solution to 1.5, then the carrier obtained by the treatment in step (1) is added, impregnated for 6 h with stirring, and then placed in an oven for drying at 100°C, and the dried carrier is placed in a muffle furnace for calcination at 450°C for 5 h;

[0088] (3) the catalyst precursor obtained in step (2) is reduced in a H2 atmosphere at 280°C for 10 h, and the flow rate of hydrogen is 500 mL / min, to obtain the catalyst.

[0089] Comparative Example 2

[0090] Compared with Example 2, the adjuvant only contains magnesium metal, and the details are as follows:

[0091] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of an alumina carrier, an active metal Pd supported on the carrier, and an adjuvant metal Mg; the percentages of the components are as follows, based on the total weight of the catalyst being 100%: Pd 0.5%, Mg 1%, and the balance being the carrier.

[0092] 2. A preparation method of the catalyst for synthesizing 2,6-dimethylaniline, comprising the following steps:

[0093] (1) 50 g of an alumina carrier is weighed and placed in a 30 g magnesium nitrate solution for stirring and impregnation adsorption for 5 h, then placed in an oven for drying at 100°C, and the dried carrier is placed in a muffle furnace for calcination at 500°C for 7 h to obtain an adjuvant-treated carrier;

[0094] (2) 30 g of a palladium chloride solution is weighed, a 10% sodium carbonate solution is used to adjust the pH of the active Pd solution to 1.5, then the carrier obtained by the treatment in step (1) is added, impregnated for 6 h with stirring, and then placed in an oven for drying at 100°C, and the dried carrier is placed in a muffle furnace for calcination at 450°C for 5 h;

[0095] (3) The catalyst precursor obtained in step (2) is reduced under H2 atmosphere at 280℃ for 10h, with the hydrogen flow rate being 500mL / min, to obtain the catalyst.

[0096] Comparative Example 3

[0097] Compared with Example 9, the adjuvant only contains metal Zn, and the details are as follows:

[0098] 1. A catalyst for synthesizing 2,6-dimethylaniline, which is composed of a carrier alumina, an active metal Pd supported on the carrier, and an adjuvant metal A and an adjuvant metal B; the adjuvant metal A is K, and the adjuvant metal B is Zn; the percentages of the components are as follows: Pd 0.5%, K 0.5%, Zn 0.1%, and the balance is the carrier, based on the total weight of the catalyst being 100%.

[0099] The preparation method of the catalyst, in step (1), a zinc nitrate solution is used, and the others are the same as those in Comparative Example 2.

[0100] I. Catalyst performance evaluation

[0101] The method for preparing 2,6-dimethylaniline by using the catalyst described in the application is as follows: the catalyst is loaded in a quartz tube of a fixed bed reactor, 2,6-dimethylphenol is used as a raw material, hydrogen and ammonia are introduced, and the reaction is carried out at 180-230℃ under normal pressure, the feeding line of the reaction is heated and kept at 220℃; wherein the molar ratio of the hydrogen to the 2,6-dimethylphenol is 10-50, the molar ratio of the ammonia to the 2,6-dimethylphenol is 5-30, the mass space velocity of the 2,6-dimethylphenol is 0.05-1h -1 .

[0102] The specific reaction conditions and results are shown in Table 1.

[0103] Table 1 Specific reaction conditions and results

[0104] Catalyst Temperature °C Hydrophenol molar ratio Aminophenol molar ratio Air speed h -1 ]] Yield % Stability period d Example 1 210 30 15 0.05 >82 >90 Example 1 180 20 30 1 >65 >90 Example 2 230 50 15 0.08 >83 >90 Example 2 210 30 15 0.05 >80 >90 Example 3 210 30 15 0.2 >85 >90 Example 4 190 10 5 0.15 >82 >90 Example 5 220 30 15 0.05 >82 >60 Example 6 220 50 20 0.05 >84 >50 Example 7 210 30 15 0.25 >90 >90 Example 8 210 30 15 0.15 >88 >90 Example 9 210 30 15 0.05 >92 >90 Example 10 230 30 15 0.05 >90 >100 Example 11 210 30 10 0.10 >91 >80 Comparative Example 1 210 30 15 0.05 >65 <5 Comparative Example 2 210 30 15 0.05 >50 <5 Comparative Example 3 210 30 15 0.05 >60 <30

Claims

1. A catalyst for synthesizing 2,6-dimethylaniline, characterized in that: It consists of a carrier, an active metal Pd loaded on the carrier, and auxiliary metals; The auxiliary metal includes auxiliary metal A and auxiliary metal B, wherein auxiliary metal A is one of K and Na, and auxiliary metal B is at least one of Ba, Mg, Zr, La and Zn; the support is alumina. Based on the total weight of the catalyst being 100%, the percentages of each component are as follows: active metal Pd 0.2-2%, auxiliary metal A 0.1-3%, auxiliary metal B 0.1-10%, and the balance being the support; The catalyst was prepared by the following method: (1) The carrier is immersed in an alkaline impregnation solution containing auxiliary metal A, and the impregnation process is stirred, dried and calcined; then the obtained carrier is immersed in a nitrate impregnation solution containing auxiliary metal B, and the impregnation process is stirred, dried and calcined. (2) Adjust the pH of the active palladium chloride solution to 1-4 to obtain an impregnation solution containing Pd, and then add the support obtained in step (1) into it for impregnation. Stir during the impregnation process, then dry and calcine to obtain the catalyst precursor. (3) The catalyst precursor is reduced to obtain the catalyst.

2. The catalyst for synthesizing 2,6-dimethylaniline according to claim 1, characterized in that: The percentages of each component are as follows: active metal Pd 0.3-1%, auxiliary metal A 0.1-1%, auxiliary metal B 0.1-5%, and the balance is carrier.

3. The catalyst for synthesizing 2,6-dimethylaniline according to claim 1, characterized in that: In step (2), the pH value of the active palladium chloride solution is adjusted with sodium carbonate solution.

4. The catalyst for synthesizing 2,6-dimethylaniline according to claim 3, characterized in that: The mass of the impregnation solution is 0.5-1 times that of the carrier, and the impregnation time is 3-10 hours.

5. The catalyst for synthesizing 2,6-dimethylaniline according to claim 4, characterized in that: The drying temperature is 80-120℃, and the calcination conditions are calcination at 400-600℃ for 2-8 hours.

6. The catalyst for synthesizing 2,6-dimethylaniline according to claim 5, characterized in that: The reduction conditions are as follows: reduction at 200-300℃ in a hydrogen atmosphere for 5-40 hours, with a hydrogen flow rate of 50-500 mL / min.

7. A method for preparing 2,6-dimethylaniline, characterized in that: The catalyst is packed into a quartz tube in a fixed-bed reactor. 2,6-Dimethylphenol is used as the raw material, and hydrogen and ammonia are introduced. The reaction is carried out at 180-230°C and atmospheric pressure. The reaction feed line is heated and kept at 220°C. The catalyst is the catalyst described in any one of claims 1-3.

8. The method for preparing 2,6-dimethylaniline according to claim 7, characterized in that: The molar ratio of hydrogen to 2,6-dimethylphenol is 10-50, the molar ratio of ammonia to 2,6-dimethylphenol is 5-30, and the mass hourly space velocity (WHSV) of 2,6-dimethylphenol is 0.05-1 h⁻¹. -1 .