Method for synthesizing o-methylaniline by hydrodechlorination of chlorine-containing o-methylaniline mixture

Abstract

The invention provides a method for synthesizing o-methylaniline by hydrodechlorination of a chlorine-containing o-methylaniline mixture. The method comprises the following steps: modifying a palladium catalyst in a first solvent and a modifier to obtain a catalyst; under the hydrogen atmosphere, the chlorine-containing o-methylaniline mixture is subjected to hydrogenation catalytic dechlorination in the presence of a catalyst, an additive and a second solvent to synthesize o-methylaniline, and a mixture is prepared; and carrying out gas-liquid separation on the obtained mixture to obtain gas and a solution, separating and purifying the solution to obtain o-methylaniline, recovering, drying and compressing the gas, and recycling hydrogen and the solvent. On one hand, a chlorine-containing o-methylaniline mixture is subjected to hydrodechlorination to prepare pure o-methylaniline by adopting a modified catalyst, byproducts generated in the preparation process of 6-chloro-2-nitrotoluene are solved, and reasonable recycling of resources is realized; on the other hand, the application field of the catalyst is expanded by recycling the specific catalyst; through cooperation of the specific catalyst and the hydrodechlorination reaction, the conversion rate and selectivity of the obtained product are high, and the catalyst is high in recycling performance, economical and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic hydrogenation, and in particular to a method for synthesizing o-methylaniline by hydrogenating and dechlorinating a chlorine-containing o-methylaniline mixture. Background Art

[0002] 6-Chloro-2-nitrotoluene is an important intermediate for pharmaceuticals, pesticides, and dyes, and is a high-value-added fine chemical product. Existing preparation processes primarily use o-nitrotoluene as a raw material. Chlorine is added to a metal catalyst reaction system for a chlorination reaction to produce a mixed product. The yield of 6-chloro-2-nitrotoluene in the mixed product is generally around 55% to 65%, with the remainder being chlorinated o-nitrotoluene byproducts. Patent CN101985425A discloses a method for preparing 6-chloro-2-nitrotoluene, with a 65% 6-chloro-2-nitrotoluene content. With current chlorination technology, after separating 6-chloro-2-nitrotoluene by distillation, the byproduct mixture typically contains 6-chloro-2-nitrotoluene, 4-chloro-2-nitrotoluene, dichloronitrotoluenes, and polychloronitrotoluenes (in a ratio of approximately 10:80:5:5 for 6-chloro-2-nitrotoluene:4-chloro-2-nitrotoluene:dichloronitrotoluenes:polychloronitrotoluenes). The purposes of by-product chlorinated o-nitrotoluene mixture after rectification is not large, and market demand is small, and separation difficulty is large. In order to recycle the by-product mixture after rectification, existing industrial method mainly adopts by-product chlorinated o-nitrotoluene mixture to be reduced to chlorinated o-methylaniline mixture, and then o-methylaniline is prepared by dechlorination of chlorinated o-methylaniline mixture to recycle. Chlorinated o-nitrotoluene mixture is reduced to chlorinated o-methylaniline mixture catalytic hydrogenation step process is simple, for example, patent CN102234236A discloses a kind of synthetic method of 3-chloro-2-methylaniline, product purity 99.80%, yield 98.80%. Chlorinated o-nitrotoluene mixture reduction obtains chlorinated o-methylaniline mixture and carries out separation and purification difficulty is large, still causes waste of resources, and direct discharge causes environmental pollution.

[0003] Based on this, it is necessary to develop a method for effectively recycling the chlorinated o-methylaniline mixture. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for synthesizing o-methylaniline by hydrodechlorination of a chlorinated o-methylaniline mixture. On the one hand, a specific catalyst is used to hydrodechlorinate the chlorinated o-methylaniline mixture to produce pure o-methylaniline, thereby eliminating the by-products generated during the preparation of 6-chloro-2-nitrotoluene and achieving rational recycling and reuse of resources. On the other hand, the specific catalyst is recycled to expand the application field of the catalyst. The synergistic combination of the specific catalyst and the hydrodechlorination reaction results in high conversion rate and selectivity of the obtained product, and the catalyst has strong recycling performance, which is economical and efficient.

[0005] To achieve the above object, the technical solution of the present invention is as follows: In one aspect, the present invention provides a method for synthesizing o-methylaniline by hydrodechlorination of a chlorine-containing o-methylaniline mixture, comprising: S1: modifying a palladium catalyst in a first solvent and a modifier to prepare a catalyst; S2: Under a hydrogen atmosphere, the chlorinated o-methylaniline mixture represented by formula (I) is subjected to hydrogenation catalytic dechlorination in the presence of a catalyst, an additive, and a second solvent to synthesize o-methylaniline, thereby obtaining a mixture; S3: The obtained mixture is subjected to gas-liquid separation to obtain gas and solution, the solution is separated and purified to obtain o-methylaniline represented by formula (II), the gas is recovered, dried and compressed, and the hydrogen and solvent are recycled; The reaction process is shown below:

[0006] Here, n is an integer of 1 to 4, preferably 1, 2, 3, or 4.

[0007] Furthermore, the chlorine-containing o-methylaniline mixture is selected from at least one of 6-chloro-2-aminotoluene, 4-chloro-2-methylaniline, dichloroaminotoluene, and polychlorinated aminotoluene. Preferably, the chlorine-containing o-methylaniline mixture is a mixture of 6-chloro-2-aminotoluene, 4-chloro-2-methylaniline, dichloroaminotoluene, and polychlorinated aminotoluene, and the mass ratio is approximately (1-100):(1-100):(1-100):(1-100):(1-100), preferably (1-15):(1-10):(70-80):(1-10):(1-10), and preferably 10:80:5:5.

[0008] Furthermore, the catalyst modification process is: dispersing the palladium catalyst in the modifier and the first solvent, and filtering to obtain the catalyst.

[0009] Furthermore, the modifier is selected from at least one of polyvinyl alcohol, acrylic resin, sodium triphenylphosphine monosulfonate, polyvinyl pyrrolidone or sodium dodecylbenzene sulfonate, preferably polyvinyl pyrrolidone or sodium dodecylbenzene sulfonate.

[0010] Furthermore, the mass ratio of the palladium catalyst to the modifier is (1-100):1, preferably (2-20):1.

[0011] Furthermore, the metal loading in the catalyst is 1% to 10%, preferably 3% to 5%.

[0012] Further preferably, the palladium catalyst is a palladium-carbon catalyst modified by a modifier.

[0013] Further preferably, the modifier is located on the surface of the supported palladium-carbon material.

[0014] Further preferably, the palladium carbon material is 3% to 5% Pd / C, preferably 3% Pd / C or 5% Pd / C.

[0015] Further preferably, the palladium catalyst is a recyclable Pd catalyst.

[0016] Furthermore, the mass ratio of the chlorinated o-methylaniline mixture to the catalyst is 1:(0.0005-0.05), preferably 1:(0.001-0.01).

[0017] Furthermore, the first solvent and the second solvent are selected from at least one of water, methanol, ethanol, and toluene.

[0018] Furthermore, the mass ratio of the chlorinated o-methylaniline mixture to the second solvent is 1:(1-15), preferably 1:(3.33-6.67).

[0019] Furthermore, the method is carried out in a reduction high-pressure reactor.

[0020] Furthermore, the additive is at least one of sodium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium thiosulfate, sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia, ammonia in methanol, and ammonium bicarbonate. The additive not only promotes the reaction but also dechlorinates and absorbs the generated hydrogen chloride, thereby achieving rational resource utilization.

[0021] Furthermore, the mass ratio of the chlorinated o-methylaniline mixture to the additive is (3-15):1, preferably (3-6):1.

[0022] Furthermore, the reaction temperature of the method is 80-150°C, preferably 90-130°C.

[0023] Furthermore, the reaction pressure of the method is 0.5~3.0MPa, preferably 0.8~1.2MPa.

[0024] In a second aspect, the present invention provides an application of a palladium catalyst in a hydrodechlorination reaction.

[0025] Further preferably, the palladium catalyst is a palladium-carbon catalyst modified by a modifier.

[0026] Further preferably, the modifier is located on the surface of the supported palladium-carbon material.

[0027] Further preferably, the palladium catalyst is a recyclable Pd catalyst.

[0028] Further preferably, the palladium carbon material is 3% to 5% Pd / C, preferably 3% Pd / C or 5% Pd / C.

[0029] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for synthesizing o-methylaniline by hydrodechlorination of a chlorinated o-methylaniline mixture. On the one hand, a specific catalyst is used to hydrodechlorinate the chlorinated o-methylaniline mixture to prepare pure o-methylaniline, thereby eliminating by-products generated in the preparation process of 6-chloro-2-nitrotoluene and achieving reasonable recycling and reuse of resources. On the other hand, the specific catalyst is cyclically applied to expand the application field of the catalyst. The specific catalyst and the hydrodechlorination reaction cooperate with each other, resulting in high conversion rate and selectivity of the obtained product, strong catalyst cyclic application performance, and high efficiency and economy.

[0030] The present invention achieves a chlorine-containing o-methylaniline mixture catalytic hydrodechlorination process by optimizing process conditions, with a conversion rate of 100%, and the products are o-methylaniline and hydrogen chloride, thereby achieving waste recycling and achieving efficient and green production. The catalyst used in the present invention can be stably applied in multiple batches for the reaction, significantly improving production efficiency and product quality, and reducing production costs. The method of the present invention makes the product selectivity and activity after the catalytic hydrogenation reaction higher, the conversion rate and selectivity are also high, the product quality is high, and the preparation process is simple, can be used for large-scale production, and has important industrial application value. DETAILED DESCRIPTION

[0031] The following content provides different embodiments or examples so that those skilled in the art can implement accordingly with reference to the description text. Of course, these are merely examples and are not intended to limit the present invention. The endpoints and any value of the scope disclosed in the present invention are not limited to this accurate scope or value, and these scopes or values ​​should be interpreted as comprising values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between the separate point value, can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article.

[0032] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. Throughout this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0033] Catalyst modification example 1 0.67 g of 3% Pd / C catalyst was weighed and placed in 10 g of 3% sodium dodecylbenzenesulfonate aqueous solution for modification, and the recycled Pd catalyst was obtained after filtration.

[0034] Example 1 Under nitrogen, 90g of a chlorinated o-methylaniline mixture (a mixture of 6-chloro-2-methylaniline, 4-chloro-2-methylaniline, dichloromethylaniline, and polychloromethylaniline in a mass ratio of 10:80:5:5), 200g of water, 30g of sodium hydroxide, and 0.67g of a recyclable Pd catalyst were placed in a reactor with stirring. The nitrogen atmosphere was replaced with hydrogen, and the temperature was raised to 110°C. Hydrogen was continuously introduced to maintain a pressure of 1.0 MPa. The reaction lasted for 1 hour and 40 minutes. The product and hydrogen mixture were cooled and separated into liquid and gas to obtain o-methylaniline. Sampling and analysis showed a 100% raw material conversion and 97.89% selectivity for the target product, o-methylaniline.

[0035] Example 2 The difference from Example 1 is that this example is a catalyst replication, the amount of catalyst added to the first kettle is 0.30 g, and 0.10 g of catalyst is added each time. After the reaction is completed, the reaction liquid is filtered out and the catalyst is returned to the kettle for replication. The catalyst is replicated 30 times. The replication data are shown in Table 1 below:

[0036] As can be seen from Table 1, the catalyst used in the present invention can be recycled for more than 30 times, and has high conversion rate and selectivity for catalyzing the chlorinated o-methylaniline mixture.

[0037] Example 3 The difference from Example 1 is that the second solvent and amount of the reaction were screened, and the other reaction conditions remained unchanged. The conversion rate and selectivity results are shown in Table 2 below.

[0038] Table 2 Reaction results of different solvents and catalytic dosages

[0039] It can be seen from the results of Table 2 and Example 1 that water has the best effect, while the selectivity of other solvents is slightly worse; when the proportion of solvent is too high, the reaction solution is diluted, and within the same reaction time, the product conversion rate and selectivity are reduced.

[0040] Example 4 The difference from Example 1 is that the type and amount of catalyst were screened, and the other reaction conditions remained unchanged. The conversion rate and selectivity results are shown in Table 3 below.

[0041] Table 3 Reaction results of different catalysts and dosages

[0042] As shown in Table 3 and the results of Example 1, the conversion and selectivity achieved were minimal when the mass ratio of the chlorinated o-methylaniline mixture to the catalyst was within the range of 1:(0.0005-0.05), while the optimal performance was achieved when the mass ratio was within the range of 1:(0.001-0.01). Furthermore, the recyclable Pd catalyst of the present invention achieved the best results compared to other catalysts.

[0043] Example 5 The difference from Example 1 is that the additives and their amounts were screened, and the other reaction conditions remained unchanged. The conversion rate and selectivity results are shown in Table 4 below.

[0044] Table 4 Reaction results of different additives and dosages

[0045] From the results in Table 4, it can be seen that the use of different additives has a certain impact on the product conversion rate; the use of different amounts of additives has little effect on the reaction selectivity, but the conversion rate changes.

[0046] Example 6 The difference from Example 1 is that the reaction temperature and pressure are screened, and the other reaction conditions remain unchanged. The conversion rate and selectivity results are shown in Table 5 below.

[0047] Table 5 Reaction results catalyzed under different reaction conditions

[0048] It can be seen from the results of Table 5 and Example 1 that using different reaction temperatures has little effect on the conversion rate; using different hydrogen pressures has a certain effect on the reaction conversion rate.

[0049] Example 7 The difference from Example 1 is that the type of chlorinated o-methylaniline mixture is different, and the other reaction conditions remain unchanged. The conversion rate and selectivity results are shown in Table 6 below.

[0050] Table 6 Reaction results catalyzed by different chlorinated o-methylaniline mixtures

[0051] Note: The dichloromethylaniline mixture refers to a mixture of compounds represented by structural formulas A to F:

[0052] A mixture of polychloromethylanilines refers to a mixture of compounds represented by structural formulas G to K:

[0053] It can be seen from the results in Table 6 that the preparation method provided by the present invention is applicable to different types of chlorinated o-methylaniline mixtures, and has relatively good conversion rate and selectivity.

[0054] Although the above embodiments have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the above descriptions are merely embodiments of the present invention and do not limit the scope of patent protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present invention.

Claims

1. A method for synthesizing o-methylaniline by hydrodechlorination of a chlorinated o-methylaniline mixture, characterized in that: include: S1: modifying a palladium catalyst in a first solvent and a modifier to prepare a catalyst; S2: Under a hydrogen atmosphere, the chlorinated o-methylaniline mixture is subjected to hydrogenation catalytic dechlorination in the presence of a catalyst, an additive, and a second solvent to synthesize o-methylaniline, thereby obtaining a mixture; S3: The obtained mixture is subjected to gas-liquid separation to obtain gas and solution, the solution is separated and purified to obtain o-methylaniline, the gas is recovered, dried and compressed, and the hydrogen and solvent are recycled.

2. The method according to claim 1, characterized in that The chlorine-containing o-methylaniline mixture is selected from at least one of 6-chloro-2-methylaniline, 4-chloro-2-methylaniline, dichloromethylaniline and polychloromethylaniline.

3. The method according to claim 2, characterized in that The chlorinated o-methylaniline mixture is a mixture of 6-chloro-2-methylaniline, 4-chloro-2-methylaniline, dichloromethylaniline and polychloromethylaniline, with a mass ratio of about (1-15):(1-10):(70-80):(1-10):(1-10), preferably 10:80:5:

5.

4. The method according to claim 1, characterized in that The catalyst modification process is as follows: dispersing the palladium catalyst in the modifier and the first solvent, and filtering to obtain the catalyst; Further preferably, the modifier is selected from at least one of polyvinyl alcohol, acrylic resin, sodium triphenylphosphine monosulfonate, polyvinyl pyrrolidone or sodium dodecylbenzene sulfonate, preferably polyvinyl pyrrolidone or sodium dodecylbenzene sulfonate; Further preferably, the mass ratio of the palladium catalyst to the modifier is (1-100):1, preferably (2-20):1; Further preferably, the palladium catalyst is a palladium-carbon catalyst modified by a modifier; preferably, the modifier is located on the surface of the supported palladium-carbon material, and the palladium-carbon material is 3% Pd / C or 5% Pd / C; Further preferably, the metal loading in the catalyst is 1% to 10%, preferably 3% to 5%.

5. The method according to claim 1, characterized in that: The mass ratio of the chlorinated o-methylaniline mixture to the catalyst is 1:(0.0005-0.05), preferably 1:(0.001-0.01).

6. The method according to claim 1, characterized in that The first solvent and the second solvent are selected from at least one of water, methanol, ethanol, and toluene; Further preferably, the mass ratio of the chlorinated o-methylaniline mixture to the second solvent is 1:(1-15), preferably 1:(3.33-6.67).

7. The method according to claim 1, characterized in that: The method is carried out in a reduction autoclave.

8. The method according to claim 1, characterized in that: The additive is at least one of sodium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium thiosulfate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia water, ammonia methanol solution, and ammonium bicarbonate; Alternatively, the mass ratio of the chlorinated o-methylaniline mixture to the additive is (3-15):1, preferably (3-6):

1.

9. The method according to claim 1, characterized in that: The reaction temperature of the method is 80-150°C, preferably 90-130°C; Alternatively, the reaction pressure of the method is 0.5-3.0 MPa, preferably 0.8-1.2 MPa.

10. Use of a palladium catalyst in a hydrodechlorination reaction, characterized in that: The palladium catalyst is a palladium-carbon catalyst modified by a modifier; preferably, the modifier is located on the surface of the supported palladium-carbon material, and the palladium-carbon material is 3% Pd / C or 5% Pd / C.

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