CN114904523B - Method for preparing N-dimethyl aromatic amine by catalyzing nitroaromatic hydrocarbon and methanol - Google Patents

Method for preparing N-dimethyl aromatic amine by catalyzing nitroaromatic hydrocarbon and methanol Download PDF

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CN114904523B
CN114904523B CN202210498503.0A CN202210498503A CN114904523B CN 114904523 B CN114904523 B CN 114904523B CN 202210498503 A CN202210498503 A CN 202210498503A CN 114904523 B CN114904523 B CN 114904523B
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CN114904523A (en
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陆强
李克明
黄耀兵
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North China Electric Power University
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Abstract

The invention provides a method for preparing N-dimethyl aromatic amine by catalyzing nitroarene and methanol, which comprises the steps of preparing nitroarene or nitroheteroaromatic compound, methanol and bimetallic CuCo/gamma-Al 2 O 3 The catalyst is mixed and placed in a stainless steel high-pressure reaction kettle, and the N-dimethyl aromatic amine compound is prepared under certain catalytic conditions. The bimetal CuCo/gamma-Al 2 O 3 The catalyst is prepared by an impregnation method, wherein Cu and Co are used as core metal elements, and oxide (gamma-Al) obtained by calcining pseudo-boehmite is prepared 2 O 3 ) Is a carrier. The catalyst involved in the method has simple and convenient synthesis method and low cost of non-noble metal; the substrate has wide applicability in the reaction, the selectivity of the double substitution reaction is high, and the structural stability of the catalyst is good; meanwhile, the catalyst can avoid the use of strong alkali additives, has low equipment requirement, is convenient to treat after the reaction, can be recycled and is environment-friendly.

Description

Method for preparing N-dimethyl aromatic amine by catalyzing nitroaromatic hydrocarbon and methanol
Technical Field
The invention relates to the technical field of N-double methylation reaction, in particular to a CuCo/gamma-Al-based catalyst 2 O 3 A method for preparing N-dimethyl aromatic amine by catalyzing nitroaromatic hydrocarbon and methanol through a bimetallic catalyst.
Background
The N-double methylation reaction is an important reaction for producing nitrogen-containing fine chemicals, can be used for structural modification of amine compounds, and changes the reaction characteristics and biological activity of the original compounds. The method is commonly used for synthesizing dyes, high molecular polymers, surfactants, pesticides, medicines and the like. The traditional N-double methylation reaction is finished by means of methyl reagents such as methyl halide, dimethyl sulfate or diazomethane, the reagent toxicity is high, strong alkali is often required to be added as an activating agent for the reaction, alkali sensitive groups are difficult to be compatible, and the post-treatment of the reaction is difficult. In recent years, more and more methylation reagents with environmental protection, such as carbon dioxide, formic acid, methanol and the like, gradually replace the traditional toxic reagents to be applied to N-methylation reaction, and the effect is obvious.
Methanol is taken as a renewable bio-based alcohol compound, and byproducts in the methylation reaction are only water, so that the methanol is green and pollution-free. Currently, by using methanol and an aromatic amine for the reaction, a high yield of N-dimethyl aromatic amine product can be obtained. However, most of the aromatic amines in industry are obtained from the hydrogenation reduction of nitroaromatics. Compared with nitroaromatic hydrocarbon, the synthesis and purification process of aromatic amine greatly increases the cost of reaction raw materials. Therefore, the development of a method for directly synthesizing N-dimethyl aromatic amine from nitroaromatic hydrocarbon has more economic benefit and environmental effect.
At present, the N-bi-methylation reaction of nitroarene and methanol can be realized by utilizing transition metal homogeneous catalysts such as Ru, ir and the like, but the homogeneous catalysts have the limitations of high price, difficult recycling and the like. Meanwhile, the addition of the strong base auxiliary agent in the reaction also greatly limits the compatibility of the substrate functional groups, and brings a plurality of disadvantages to the application in industrialization. For heterogeneous catalysts, cu has been reported 7.5 Cr 5 /Al 2 O 3 (petrol. Chem.,2014,54 (6), 438-444) for catalyzing nitrobenzene and methanol to synthesize N-dimethyl aniline in one pot at 250 deg.C, but the reaction condition of the system is harshThe energy consumption is high and the yield is relatively low. In recent years, scientific researchers at home and abroad have developed heterogeneous noble metal catalysts such as Pt/C (J.Catal., 2019,371,47-56), pd/C (J.Org.chem., 2019,84,15389-15398) and Ir@YSMCNs (Asian J.Org.chem.,2019,8,487-491), so as to synthesize N-dimethyl aromatic amine compounds under mild conditions (130-170 ℃). It is not difficult to find that for the heterogeneous catalytic system, the noble metal catalyst has high cost and the reaction system can be promoted by adding a strong base auxiliary agent. These limitations have prompted researchers to continually develop new heterogeneous inexpensive metal catalysts in the hope of achieving N-bis-methylation of nitroarenes with methanol in the presence of mild, alkali-free additives.
In view of this, the present invention has been made.
Disclosure of Invention
One of the purposes of the present invention is to provide a supported bimetallic CuCo/gamma-Al 2 O 3 The catalyst is used for catalyzing the condensation reaction of methanol and nitroaromatic hydrocarbon or nitroheteroaromatic compound to obtain N-dimethyl aromatic amine with high yield.
The second object of the present invention is to provide the supported bimetallic CuCo/gamma-Al 2 O 3 A method for preparing the catalyst.
The invention also aims to provide a method for preparing the N-dialkyl aromatic amine compound by catalyzing nitroaromatic hydrocarbon or nitroheteroaromatic hydrocarbon and alcohol, which adopts the catalyst to catalyze the condensation reaction of the alcohol and the nitroaromatic hydrocarbon or nitroheteroaromatic hydrocarbon compound.
In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:
in a first aspect, the present invention provides a supported bimetallic CuCo/gamma-Al 2 O 3 Catalyst, cu and Co are used as core metals, and gamma-Al which is the calcined product of pseudo-boehmite is used 2 O 3 Is a carrier;
based on supported bimetallic CuCo/gamma-Al 2 O 3 The total weight of the catalyst, cu loading was 3-12wt% (e.g., 3, 4,5, 6, 7, 8, 9, 10, 11, 12 wt%), and the total metal content of Co and Cu remained constant at 15 wt%.
The active metal element of the catalyst is Cu and Co bimetallic, and the carrier is the calcined product gamma-Al of pseudo-boehmite 2 O 3 。
The load capacity calculating method comprises the following steps: metal mass in metal precursor/(metal mass in metal precursor + support mass) ×100%.
Preferably, the supported bimetallic CuCo/gamma-Al 2 O 3 The catalyst is prepared by adopting an impregnation method.
Preferably, the supported bimetallic CuCo/gamma-Al 2 O 3 The preparation method of the catalyst comprises the following steps:
weighing pseudo-boehmite, placing the pseudo-boehmite into a muffle furnace, calcining at high temperature, cooling to room temperature, and taking out to obtain gamma-Al 2 O 3 The method comprises the steps of carrying out a first treatment on the surface of the Weighing gamma-Al 2 O 3 Mixing copper source and cobalt source, adding water, stirring, removing water by rotary evaporator, drying, grinding, calcining, cooling to room temperature, taking out, reducing in tubular furnace, naturally cooling to room temperature, and taking out to obtain supported bimetallic CuCo/gamma-Al 2 O 3 A catalyst;
the source of pseudo-boehmite is not limited and is mainly commercially available.
The copper source may be a precursor known in the art for making a catalytically active metallic copper element, including, but not limited to, copper nitrate trihydrate, copper acetate, anhydrous copper sulfate, and copper chloride.
The cobalt source may be a precursor known in the art for making a catalytically active metallic cobalt element, including, but not limited to, cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, cobalt sulfate heptahydrate, and cobalt chloride hexahydrate.
Preferably, the calcination temperature is 300-500 ℃ and the calcination time is 2-6h.
Preferably, the reduction conditions are 400-600 ℃, H 2 /N 2 The volume ratio is 5-20%, and the reduction time is 1-5h.
As a preferred embodiment, the supported bimetallic 10Cu-5 Co/gamma-Al 2 O 3 The preparation method of the catalyst comprises the following steps:
firstly, placing pseudoboehmite into a muffle furnace to be calcined at 700 ℃ for 6 hours (the heating rate is that the initial temperature is 25 ℃, and the temperature is increased to 700 ℃ at the speed of 6 ℃/min), and naturally cooling to room temperature to obtain the gamma-Al 2 O 3 。
Subsequently, 1.7g of gamma-Al was weighed out 2 O 3 Mixing 0.755g of copper nitrate trihydrate and 0.494g of cobalt nitrate hexahydrate, placing the mixture in a 50mL round bottom flask, adding 15mL of deionized water, stirring for 12h at room temperature for 750r/min, then removing water by using a rotary evaporator at 40 ℃, drying the obtained solid in a 110 ℃ oven for 12h, immediately grinding the obtained solid by using a mortar while hot, calcining the obtained powder in a muffle furnace at 400 ℃ for 4h (heating rate: initial temperature 25 ℃,7 ℃/min rising to 400 ℃), taking out the powder after cooling to room temperature, and finally placing the powder in a tubular furnace at 500 ℃ and 10% H 2 /N 2 Reducing for 3h (heating rate: initial temperature 25 ℃,5.5 ℃/min rising to 500 ℃), naturally cooling to room temperature, and taking out to obtain 10wt% Cu-5wt% Co/gamma-Al 2 O 3 Catalyst (designated as 10Cu-5 Co/gamma-Al) 2 O 3 )。
In a second aspect, the present invention provides a supported bimetallic CuCo/gamma-Al as described above 2 O 3 The preparation method of the catalyst adopts an impregnation method to prepare the catalyst.
Preferably, the method comprises the steps of:
weighing gamma-Al 2 O 3 Mixing copper source and cobalt source, adding water, stirring, removing water by rotary evaporator, drying, grinding, calcining, cooling to room temperature, taking out, reducing in tubular furnace, naturally cooling to room temperature, and taking out to obtain supported bimetallic CuCo/gamma-Al 2 O 3 A catalyst.
The relevant matters related to the catalyst preparation method are consistent with the corresponding matters in the first aspect, and are not repeated here.
In a third aspect, the present invention provides a method of catalyzing nitroaromatic hydrocarbons with methanol to produce an N-dimethyl aromatic amine compound, the method comprising the steps of:
nitroarene or nitroheteroarene compound as raw material, methanol and upper materialThe supported bimetal CuCo/gamma-Al 2 O 3 The catalyst or the supported bimetallic CuCo catalyst with different carriers or metal proportions prepared by the preparation method is added into a high-pressure reactor, and hydrogen is introduced to perform catalytic reaction to prepare the N-dimethyl aromatic amine product.
The invention provides a high-efficiency supported bimetallic catalyst CuCo/gamma-Al 2 O 3 Is used for catalyzing the condensation reaction of methanol and nitroarene or nitroheteroarene compounds to obtain N-dimethyl aromatic amine with high yield.
The reaction route is as follows:
Figure BDA0003633836530000041
wherein R is a substituent group on an aromatic ring and can be selected from one or more of alkyl, alkoxy, ester group, halogen and aromatic ring (benzene ring); the aromatic ring may also be an N-containing aromatic heterocycle.
The method for preparing the N-dimethyl aromatic amine compound by catalyzing methanol comprises the following steps:
nitroarene or nitroheteroarene compound as raw material, methanol and supported bimetallic CuCo/gamma-Al 2 O 3 The catalyst is added into a stainless steel high-pressure reaction kettle after being uniformly mixed, and the N-dimethyl aromatic amine is prepared by catalytic methylation reaction under certain reaction conditions.
The raw material nitroaromatic hydrocarbon compound is nitrobenzene compound or nitronaphthalene compound containing different substituents.
The substituent on the aromatic ring of the nitrobenzene compound can be independently selected from one or more of alkyl, alkoxy, ester, halogen and aromatic ring (benzene ring).
The nitroheteroaromatics are nitro compounds containing N heteroaromatics.
Nitroaromatics include, but are not limited to, nitrobenzene, o-nitrotoluene, p-nitroanisole, methyl 4-nitrobenzoate, p-fluoronitrobenzene, p-chloronitrobenzene, 3-chloronitrobenzene, 1-nitronaphthalene, or 4-nitrobiphenyl.
Nitroheteroaromatics include, but are not limited to, 3-nitropyridines.
Preferably, the concentration of methanol (and the mass concentration ratio of water) is >95%.
Preferably, the reaction temperature is 180-240 ℃, e.g. 190, 200 ℃, and the reaction time is 2-16h, e.g. 4, 6, 8, 10, 12, 14, 16h.
Preferably, the hydrogen pressure is 5-20bar, e.g. 5, 6, 8, 10, 12, 15, 16, 18, 20bar.
Preferably, per 1mmol of nitroarene or nitroheteroarene, the supported bimetallic CuCo/gamma-Al 2 O 3 The dosage of the catalyst is 130-170mg.
Preferably, the molar ratio of nitroarene or nitroheteroarene to methanol is 1 (9-300), for example 1: 10. 1: 20. 1: 50. 1: 60. 1: 80. 1:100, 1: 120. 1: 150. 1: 180. 1: 200. 1: 250. 1: 280. 1:300.
the invention provides a novel catalyst system for catalyzing N-bi-methylation reaction of nitroaromatic hydrocarbon or nitroheteroaromatic hydrocarbon and methanol. The system utilizes the supported bimetallic CuCo/gamma-Al 2 O 3 The catalyst realizes the direct N-double methylation reaction of nitroarene or nitroheteroarene and methanol by means of hydrogen atmosphere, and high reaction efficiency and yield are obtained. The supported bimetallic catalyst in the reaction system has simple synthesis steps, good stability and high substrate compatibility, and can still play a good catalytic effect without adding strong alkali. The development of the method provides a new scheme for constructing green sustainable N-bis-methylated amine synthesis.
The invention has the advantages that: the bimetallic copper-cobalt catalyst prepared by wet impregnation can catalyze nitroaromatic compounds to react with methanol under mild conditions, and tertiary amine derivatives with high yield are obtained, and the byproduct is only water. Compared with the existing N-bis-methylated amine synthesis system, the catalyst system adopts nitroarene as a raw material, does not need a strong base additive, has mild reaction conditions and wide substrate application range. The invention is good supplement and beneficial improvement to the existing N-dimethyl amine compound synthesis system.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a nuclear magnetic H spectrum of the product obtained in example 2 of the present invention.
FIG. 2 is a nuclear magnetic C-spectrum of the product obtained in example 2 of the present invention.
FIG. 3 is a graph of 10wt% Cu-5wt% Co/gamma-Al synthesized according to the present invention 2 O 3 Transmission Electron Microscope (TEM) image of the catalyst.
FIG. 4 is a graph of 10wt% Cu-5wt% Co/gamma-Al synthesized according to the present invention 2 O 3 NH of catalyst 3 -TPD map.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in connection with the embodiments, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is further illustrated by the following examples. The materials in the examples were prepared according to the existing methods or were directly commercially available unless otherwise specified.
Example 1
CuCo/γ-Al 2 O 3 The bimetallic catalyst is prepared by adopting an impregnation method, and comprises the following steps:
firstly, placing pseudoboehmite into a muffle furnace to be calcined at 700 ℃ for 6 hours (the heating rate is that the initial temperature is 25 ℃, and the temperature is increased to 700 ℃ at the speed of 6 ℃/min), and naturally cooling to room temperature to obtain the gamma-Al 2 O 3 。
Subsequently, 1.7g of gamma-Al was weighed out 2 O 3 Mixing 0.755g of copper nitrate trihydrate and 0.494g of cobalt nitrate hexahydrate, placing the mixture in a 50mL round bottom flask, adding 15mL of deionized water, stirring for 12h at room temperature for 750r/min, then removing water by using a rotary evaporator at 40 ℃, drying the obtained solid in a 110 ℃ oven for 12h, immediately grinding the obtained solid by using a mortar while hot, calcining the obtained powder in a muffle furnace at 400 ℃ for 4h (heating rate: initial temperature 25 ℃,7 ℃/min rising to 400 ℃), taking out the powder after cooling to room temperature, and finally placing the powder in a tubular furnace at 500 ℃ and 10% H 2 /N 2 Reducing for 3h (heating rate: initial temperature 25 ℃,5.5 ℃/min rising to 500 ℃), naturally cooling to room temperature, and taking out to obtain 10wt% Cu-5wt% Co/gamma-Al 2 O 3 Catalyst (abbreviated as 10Cu-5 Co/gamma-Al 2 O 3 ). The TEM image is shown in fig. 3, and uniformly dispersed metal nano particles are observed, so that successful loading of metal Cu and Co and uniform distribution on the surface of the carrier are demonstrated; NH (NH) 3 The TPD pattern is shown in fig. 4, and broad peaks at 150-225 ℃, 300-450 ℃ and 500-725 ℃ are detected, demonstrating the presence of a large number of weak, medium and strong acid sites in the catalyst.
Example 2
150mg of 10wt% Cu-5wt% Co/gamma-Al 2 O 3 Example 1 12mL of methanol, 1mmol of nitrobenzene were charged into a 35mL stainless steel autoclave and 10bar H was vented 2 The reaction was carried out at 190℃for 4 hours with stirring at 700rpm, and the reaction product was confirmed by nuclear magnetic analysis (FIG. 1, FIG. 2) to be N, N-dimethylaniline as the main product. By taking naphthalene as an internal standard and quantitatively analyzing by gas chromatography, the yield of the N, N-dimethylaniline is 99%, and the yield is calculated as follows: target product yield (%) = amount of target product actually obtained +..
Comparative example 1
Substantially the same as in example 2, except that: ceO is adopted 2 10wt% Cu-5wt% Co/gamma-Al as a support 2 O 3 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of detection, N-two are obtained in this exampleThe yield of methylaniline was 25%.
The 10wt% Cu-5wt% Co/CeO 2 The procedure of example 1 was followed except that the commercial CeO was used 2 Substitution of gamma-Al 2 O 3 。
Comparative example 2
Substantially the same as in example 2, except that: tiO is adopted 2 10wt% Cu-5wt% Co/TiO as a support 2 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 2%.
The 10wt% Cu-5wt% Co/TiO 2 The procedure of example 1 was followed except that the catalyst was prepared as commercially available TiO 2 Substitution of gamma-Al 2 O 3 。
Comparative example 3
Substantially the same as in example 2, except that: siO is adopted 2 10wt% Cu-5wt% Co/SiO as a support 2 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, the yield of N, N-dimethylaniline obtained in the examples of the present invention was 5%.
The 10wt% Cu-5wt% Co/SiO 2 The procedure of example 1 was followed except that the preparation was carried out as commercially available SiO 2 Substitution of gamma-Al 2 O 3 。
Comparative example 4
Substantially the same as in example 2, except that: 10wt% Cu-5wt% Co/HZSM-5 was used as a carrier for 10wt% Cu-5wt% Co/gamma-Al in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 0.
The preparation of 10wt% Cu-5wt% Co/HZSM-5 was identical to the procedure of example 1 except that commercially available HZSM-5 was used in place of gamma-Al 2 O 3 。
Comparative example 5
Substantially the same as in example 2, except that: 15wt% Cu/gamma-Al is used 2 O 3 Instead of example 210wt% Cu-5wt% Co/gamma-Al of (C) 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 65%.
Comparative example 6
Substantially the same as in example 2, except that: 12wt% Cu-3wt% Co/gamma-Al is used 2 O 3 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 87%.
Comparative example 7
Substantially the same as in example 2, except that: 5wt% Cu-10wt% Co/gamma-Al is used 2 O 3 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 81%.
Comparative example 8
Substantially the same as in example 2, except that: 3wt% Cu-12wt% Co/gamma-Al is used 2 O 3 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 72%.
Comparative example 9
Substantially the same as in example 2, except that: 15wt% Co/gamma-Al is used 2 O 3 Instead of 10wt% Cu-5wt% Co/gamma-Al as in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 10%.
By the comparison, the catalyst with the best catalytic effect is 10wt percent Cu-5wt percent Co/gamma-Al 2 O 3 A catalyst. Different catalyst dosages:
example 3
Substantially the same as in example 2, except that: 130mg of 10wt% Cu-5wt% Co/gamma-Al are used 2 O 3 The catalyst replaces 150mg of 10wt% Cu-5wt% Co/gamma-Al in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 86%.
Example 4
Substantially the same as in example 2, except that: 170mg of 10wt% Cu-5wt% Co/gamma-Al are used 2 O 3 The catalyst replaces 150mg of 10wt% Cu-5wt% Co/gamma-Al in example 2 2 O 3 As a result of the detection, N-dimethylaniline was obtained in the present example in a yield of 99%.
The above examples show that the catalyst system can obtain excellent catalytic effect when the catalyst dosage is 130-170mg.
Different reaction temperatures:
example 5
Substantially the same as in example 2, except that: the result of the detection using 180℃instead of 190℃in example 2 was that N, N-dimethylaniline was obtained in the yield of 80%.
Example 6
Substantially the same as in example 2, except that: the result of the detection using 200℃instead of 190℃in example 2 was that N, N-dimethylaniline was obtained in the present example in a yield of 98%.
The above examples show that the catalytic system can obtain excellent catalytic effect at the reaction temperature of 180-200 ℃.
Different reaction times:
example 7
Substantially the same as in example 2, except that: the detection result was that the yield of N, N-dimethylaniline obtained in the examples of the present invention was 99% by using 6 hours instead of 4 hours in the example 2.
Example 8
Substantially the same as in example 2, except that: the detection result was that the yield of N, N-dimethylaniline obtained in the examples of the present invention was 89% by using 3 hours instead of 4 hours in the example 2.
Example 9
Substantially the same as in example 2, except that: the detection result was that the yield of N, N-methylaniline obtained in the example of the present invention was 78% by using 2h instead of 4h in example 2.
By the above examples, it is shown that the present catalytic systemExcellent catalytic effect can be obtained when the reaction time is 2-6 hours. Different H 2 Pressure:
example 10
Substantially the same as in example 2, except that: by 5bar H 2 Instead of 10bar H in example 2 2 As a result of the detection, the yield of N, N-dimethylaniline obtained in the examples of the present invention was 79%.
Example 11
Substantially the same as in example 2, except that: by 20bar H 2 Instead of 10bar H in example 2 2 As a result of the detection, the yield of N, N-dimethylaniline obtained in the examples of the present invention was 90%.
By the above examples, it is shown that the present catalytic system is in H 2 Excellent catalytic effect can be obtained at a pressure of 5-20 bar.
Different methanol concentrations:
example 12
Substantially the same as in example 2, except that: the methanol with a concentration of 95% was used instead of 99% of the methanol in example 2, and as a result, the yield of N, N-dimethylaniline was 90% in the examples of the present invention.
The above examples show that the catalytic system can obtain excellent catalytic effect at the concentration of 95-99% of methanol.
Different methanol amounts:
example 13
Substantially the same as in example 2, except that: 8mL of methanol and 4mL of toluene were used in place of 12mL of methanol in example 2, and as a result of detection, this example gave N, N-dimethylaniline in 77% yield.
Example 14
Substantially the same as in example 2, except that: 9mL of methanol and 3mL of toluene were used in place of 12mL of methanol in example 2, and as a result of detection, this example gave N, N-dimethylaniline in 83% yield.
Example 15
Substantially the same as in example 2, except that: 11mL of methanol and 1mL of toluene were used in place of 12mL of methanol in example 2, and as a result of detection, N-dimethylaniline was obtained in the present example in a yield of 90%.
The above examples show that the catalytic system can obtain excellent catalytic effect when the methanol dosage is 8-12 mL.
Nitroarene substrate expansion:
example 16
Substantially the same as in example 2, except that: the nitrobenzene of example 2 was replaced with para-nitrotoluene, and the yield of N, N-dimethyl-para-toluidine obtained in the examples of the present invention was 98%.
Example 17
Substantially the same as in example 2, except that: the detection result of using o-nitrotoluene instead of nitrobenzene in example 2 shows that the yield of N, N-dimethyl-o-toluidine obtained in the example of the present invention is 97%.
Example 18
Substantially the same as in example 2, except that: the detection result shows that the yield of the N, N-dimethyl-p-methoxyaniline obtained by the embodiment of the invention is 90% by adopting the p-nitroanisole to replace the nitrobenzene in the embodiment 2.
Example 19
Substantially the same as in example 2, except that: the methyl 4-nitrobenzoate was used in place of the nitrobenzene and 4h in example 2, with a yield of 98% for this example.
Example 20
Substantially the same as in example 2, except that: the detection results of the invention, which were obtained in the examples of the invention, showed that the yield of N, N-dimethyl-p-fluoroaniline was 95% by using p-fluoronitrobenzene for 6h instead of nitrobenzene for 4h in the example 2.
Example 21
Substantially the same as in example 2, except that: the nitrobenzene and the nitrobenzene in the example 2 are replaced by p-chloronitrobenzene and 6h, and the detection result shows that the yield of the N, N-dimethyl-p-chloroaniline obtained in the example of the invention is 93%.
Example 22
Substantially the same as in example 2, except that: 3-chloronitrobenzene and 12h are adopted to replace nitrobenzene and 4h in the example 2, and the detection result shows that the yield of N, N-dimethyl m-chloroaniline obtained in the example of the invention is 89%.
Example 23
Substantially the same as in example 2, except that: 1-nitronaphthalene and 8h are used to replace nitrobenzene and 4h in example 2, and the detection result shows that the yield of N, N-dimethyl-1-naphthylamine obtained in the example of the invention is 92%.
Example 24
Substantially the same as in example 2, except that: the detection result shows that the yield of the N, N-dimethyl-4-benzidine obtained in the embodiment of the invention is 96% by adopting 4-nitrobiphenyl and 12h to replace nitrobenzene and 4h in the embodiment 2.
Expansion of nitroheteroarene substrates:
example 25
Substantially the same as in example 2, except that: the 3-nitropyridine was used at 240℃for 12 hours instead of nitrobenzene in example 2 at 190℃for 4 hours, and the yield of 3-dimethylaminopyridine obtained in the examples of the present invention was 80%.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (8)

1. A method for preparing N-dimethyl aromatic amine or N-dimethyl heteroaromatic amine by catalyzing nitroaromatic compounds or nitroheteroaromatic compounds and methanol, which is characterized by comprising the following steps:
the raw material nitroarene compound or nitroheteroarene compound, methanol and supported bimetallic CuCo/gamma-Al 2 O 3 Adding a catalyst into a high-pressure reactor, and introducing hydrogen to perform catalytic reaction to obtain an N-dimethyl aromatic amine or N-dimethyl heteroaromatic amine product;
the supported bimetal CuCo/gamma-Al 2 O 3 The catalyst takes Cu and Co as core metals and takes gamma-Al as calcined product of pseudo-boehmite 2 O 3 Is a carrier; based on supported bimetallic CuCo/gamma-Al 2 O 3 The total weight of the catalyst, wherein the loading of Cu is 3-12wt%, and the total metal content of Co and Cu is kept constant at 15 wt%;
the supported bimetal CuCo/gamma-Al 2 O 3 The catalyst is prepared by the following method:
weighing pseudo-boehmite, placing the pseudo-boehmite into a muffle furnace, calcining at high temperature, cooling to room temperature, and taking out to obtain gamma-Al 2 O 3 The method comprises the steps of carrying out a first treatment on the surface of the Weighing a certain amount of gamma-Al 2 O 3 Mixing copper source and cobalt source, adding water, stirring, removing water by rotary evaporator, drying, grinding, calcining, cooling to room temperature, taking out, reducing in tubular furnace, naturally cooling to room temperature, and taking out to obtain supported bimetallic CuCo/gamma-Al 2 O 3 A catalyst;
the calcination temperature is 300-500 ℃ and the calcination time is 2-6 h;
reducing at 400-600 deg.C under H 2 /N 2 The volume ratio is 5-20%, and the reduction time is 1-5h.
2. The method of claim 1, wherein the copper source comprises one or more of copper nitrate trihydrate, copper acetate, anhydrous copper sulfate, and copper chloride.
3. The method of claim 1, wherein the cobalt source comprises one or more of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, cobalt nitrate heptahydrate, and cobalt chloride hexahydrate.
4. The method according to claim 1, wherein the catalytic reaction temperature is 180-240 ℃ and the catalytic reaction time is 2-16 h.
5. The method according to claim 1, wherein the hydrogen pressure is 5-20 bar.
6. The method according to claim 1, wherein the supported bimetallic CuCo/gamma-Al is 1mmol per 1mmol of nitroaromatic or nitroheteroaromatic 2 O 3 The addition amount of the catalyst is 130-170 and mg.
7. The method according to claim 1, wherein the molar ratio of nitroaromatic or nitroheteroaromatic to methanol is 1 (9-300).
8. The method according to any one of claims 1 to 7, wherein the nitroaromatic compound comprises nitrobenzene, nitrobenzene with substituents on the aromatic ring, the substituents on the aromatic ring being one or more of alkyl, alkoxy, ester, halogen, aryl; the nitroheteroaromatics are N-containing aromatic heterocyclic nitro compounds.
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