Preparation method of cyclicly applied pt catalyst and application thereof in synthesis of key intermediate of carfentrazone-ethyl

Abstract

This invention belongs to the field of pesticide technology and provides a method for preparing a reusable Pt catalyst, comprising: a) dispersing a powdered support in a solvent to obtain a powdered support dispersion; b) uniformly dispersing a metal mixture of Pt and an auxiliary metal into the powdered support dispersion obtained in step a) to obtain a metal / support impregnation solution; c) reducing the metal / support impregnation solution to obtain a reusable Pt catalyst. The catalyst prepared by this method requires a small amount of catalyst in catalytic hydrogenation and can be reused multiple times, greatly reducing catalyst costs; simultaneously, the impurities generated in the reaction are significantly reduced, greatly improving product yield.

Description

Technical Field

[0001] This invention relates to the field of pesticide technology, specifically to a recycle-type Pt catalyst, its preparation method, and its application in the synthesis of key intermediates of benzoxazine. Background Technology

[0002] Benzoflubenzuron is a benzyl ester pyrazolone herbicide, belonging to a new type of highly selective herbicide. It is a p-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicide. It has five prominent characteristics: ① high safety ② excellent selectivity ③ broad-spectrum weed control ④ long-lasting effect ⑤ strong compatibility. Its safety profile is higher than that of nicosulfuron and mesosulfuron, making it the safest post-emergence selective herbicide for corn fields. The choice of its preparation process conditions affects the product cost. The preparation of the key intermediate 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole involves the reduction of nitro groups, generally using the palladium-on-carbon hydrogenation reduction method. Palladium-on-carbon can achieve a certain reduction effect, but it is prone to generating impurities during use and cannot be directly recycled after a single use. Platinum-on-carbon is a supported catalyst in which platinum is loaded onto activated carbon. It belongs to the category of precious metal catalysts and can be used in pharmaceuticals, electronics, and other fields. The metal loading content is generally between 0.5% and 20%. Due to its high price, the cost can be greatly reduced in industrial applications if it can be recycled. Summary of the Invention

[0003] This invention provides a method for preparing a reusable Pt catalyst. The catalyst prepared by this method requires a small amount of catalyst in catalytic hydrogenation and can be reused multiple times, which greatly reduces the catalyst cost. At the same time, the impurities generated in the reaction are significantly reduced, greatly improving the product yield.

[0004] Specifically, this invention provides a method for preparing a reusable Pt catalyst, comprising the following steps:

[0005] a) Disperse the powder carrier in a solvent to obtain a powder carrier dispersion;

[0006] b) The mixed solution of Pt and auxiliary metal salts is uniformly dispersed into the powder carrier dispersion obtained in step a) to obtain a metal / carrier impregnation solution;

[0007] c) Reduce the metal / support impregnation solution to obtain a reusable Pt catalyst.

[0008] In some embodiments, the powder carrier is selected from activated carbon, alumina, silicon dioxide, or zirconium dioxide; the solvent is selected from one or more of water, methanol, ethanol, benzene, and toluene.

[0009] In some embodiments, the metal salt of Pt is a water-soluble salt, preferably one or more of chloroplatinic acid, sodium chloroplatinate, and potassium chloroplatinate; the metal salt of the auxiliary metal is a water-soluble salt, preferably a water-soluble salt of at least one of Pd, Ru, Rh, Fe, Mn, In, and Sn. Preferably, the water-soluble salt of the auxiliary metal is ferric chloride or manganese nitrate.

[0010] In some embodiments, the Pt content in the metal mixture solution of Pt and auxiliary metal is 0.5 to 10 wt%, and the auxiliary metal content is 0.01% to 5%.

[0011] The present invention can be achieved when the Pt content in the catalyst is 0.5%. Increasing the Pt content further enhances the realization of the present invention. From a green and environmentally friendly perspective, the Pt content can be selected as 0.5-10 wt%, 0.5-5 wt%, 1-5 wt%, or 1-3 wt%.

[0012] The metal content of the additive is 0.01%-5%, and can also be selected as 0.1%-2%, 0.1%-1%, or 0.1%-0.5%.

[0013] In some embodiments, the reduction is achieved by adding a reducing agent or by reducing with hydrogen.

[0014] The reducing agent is selected from one or more of NaBH4, KBH4, hydrazine hydrate, formic acid, citric acid, formaldehyde, ethylene glycol, or polyethylene glycol.

[0015] The reduction by adding a reducing agent refers to adding the reducing agent to the metal / carrier impregnation solution;

[0016] Preferably, the hydrogen reduction refers to filtering the metal / carrier impregnation solution and then reducing the filter residue with hydrogen.

[0017] In some embodiments, dispersion in step b) is carried out by stirring for 4-72 hours; preferably 12-24 hours.

[0018] The purpose of stirring in step b) is to achieve uniform dispersion. Factors affecting the stirring time include, but are not limited to, solvent properties, material state, temperature, stirring speed, and stirring tools.

[0019] In some embodiments, the metal / carrier impregnation solution is stabilized at a temperature ranging from 20°C to 150°C before reduction by adding a reducing agent; preferably, it is between 40°C and 80°C.

[0020] In some embodiments, the hydrogen reduction is carried out at a temperature of 20°C-200°C, preferably 90°C-180°C, and a hydrogen reduction pressure of 0.05MPa-2.0MPa, preferably 0.1MPa-1.0MPa.

[0021] The present invention also provides a method for preparing 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole, a key intermediate of benzoxazole, using 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole hydrogenation as a raw material, and using the preparation method described in any one of claims 1-7 to obtain a reusable Pt catalyst as a catalyst.

[0022] In some embodiments, 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole is reacted with a catalyst and hydrogen in an organic solvent to obtain 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole.

[0023] In some embodiments, the organic solvent is selected from at least one of methanol, ethanol, and ethyl acetate;

[0024] The reaction temperature is 20℃-100℃; preferably 20℃-60℃.

[0025] The hydrogen pressure is 0.1 MPa-2.0 MPa; preferably 0.4 MPa-1.0 MPa.

[0026] Beneficial effects

[0027] The catalyst prepared by the method described in this invention, when used as a raw material in the preparation of the key intermediate 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole from 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, requires a small amount of catalyst and can be reused multiple times. Even after five reuses, impurities can still be controlled at a low level, and it exhibits excellent selectivity, greatly reducing catalyst costs. At the same time, the amount of impurities generated in the reaction is significantly reduced; compared with the use of Pd carbon catalyst, the amount of impurities generated is 1 / 3 or even 1 / 5, thus improving the product yield.

[0028] Terminology Explanation

[0029] Certain embodiments of the present invention will now be described in detail. The present invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials described herein can be used to practice the present invention. The present invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0030] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0031] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0032] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above 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 one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] In the following content, all figures disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each figure may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%, etc. Whenever a figure with a value of N is disclosed, any figure with a value of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Attached Figure Description

[0034] Figure 1 The image shows the XRD pattern of the catalyst prepared in Example 1.

[0035] Figure 2 The image shows a TEM image of the catalyst prepared in Example 1.

[0036] Figure 3 High-performance liquid chromatography (HPLC) diagram of the reduction catalysis of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole using the catalyst prepared in Example 1. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0038] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0039] Example 1

[0040] Preparation of catalyst 1:

[0041] a) Disperse 40g of activated carbon carrier in 200ml of water;

[0042] b) The prepared mixed solution of sodium chloroplatinate and ferric chloride was added to the activated carbon carrier dispersion using a feed pump. The feed rate was controlled at 0.5 ml per minute. After the feed was completed, the mixture was stirred and dispersed for 12 hours to achieve uniform mixing, thus obtaining an impregnation solution composed of the mixed metal solution and the activated carbon carrier.

[0043] c) Catalyst reduction step: First, stabilize the impregnation solution at 25℃, then add 0.35g NaBH4 for reduction, stirring for 30min, then wash and dry. The XRD pattern of the catalyst is shown below. Figure 1 The XRD diffraction peaks are very weak, indicating that the active metal is well dispersed. TEM image as follows. Figure 2 The active metal has a size of 2-2.5 nm and is uniformly dispersed.

[0044] Catalytic applications:

[0045] Using a 500 mL reactor, 100 mL of methanol solvent, 20.6 g of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, and 0.2 g of catalyst were added sequentially. The mixture was heated to 60 °C and the reaction was initiated while maintaining a hydrogen pressure of 1.0 MPa. The catalyst was a carbon-supported Pt active metal component and an Fe auxiliary metal component, with Pt comprising 3% and Fe 0.5% by mass (100% catalyst mass). The reaction ended after 2 hours and 40 minutes. Samples were taken from the reactor and analyzed by high-performance liquid chromatography (HPLC). The feed conversion rate was 100%, and the product chromatographic purity was 95.60%, with an excess hydrogenation impurity content of 0.46%. The HPLC chromatogram is shown below. Figure 3 .

[0046] Example 2

[0047] Preparation of catalyst 2:

[0048] a) Disperse 40g of alumina carrier in 200ml of water;

[0049] b) The prepared mixed solution of potassium chloroplatinate and ferric chloride was added to the alumina carrier dispersion using a feed pump. The feed rate was controlled at 0.2 ml per minute. After the feed was completed, the mixture was stirred and dispersed for 12 hours to obtain an impregnation solution composed of the mixed metal solution and the activated carbon carrier.

[0050] c) Catalyst reduction step: Stabilize the impregnation solution at 50°C, add 0.15g formic acid for reduction, keep stirring for 4 hours, and then wash and dry.

[0051] Catalytic applications:

[0052] Using a 500 mL reactor, 100 mL of methanol solvent, 20.6 g of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, and 0.6 g of catalyst were added sequentially. The mixture was heated to 60 °C, and the reaction was initiated while maintaining a hydrogen pressure of 1.0 MPa. The catalyst was a metal composite catalyst consisting of a Pt active metal component supported on an alumina support and an Fe auxiliary metal component. Based on the mass of the catalyst (100%), the mass percentage of Pt was 1% and the mass percentage of Fe was 0.2%. The reaction ended after 1 hour and 10 minutes. Samples were taken from the reactor and analyzed by liquid chromatography. The feed conversion rate was 100%, and the product chromatographic purity was 97.00%, with an excess hydrogenation impurity content of 0.57%.

[0053] Example 3

[0054] Preparation of catalyst 3:

[0055] a) Disperse 20g of activated carbon carrier in 150ml of water;

[0056] b) The prepared mixed solution of chloroplatinic acid and manganese nitrate metal salts was added to the carbon carrier dispersion using a feed pump. The feed rate was controlled at 0.5 ml per minute. After the feed was completed, the mixture was stirred and dispersed for 8 hours to obtain an impregnation solution composed of the metal mixed solution and the activated carbon carrier.

[0057] c) The catalyst reduction step involves filtering the loaded activated carbon, washing and drying it, reducing it with hydrogen at 100°C and 0.5 MPa, and then washing and drying it again.

[0058] Catalytic applications:

[0059] Using a 500 mL reactor, 100 mL of ethanol solvent, 20.6 g of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, and 0.2 g of catalyst were added sequentially. The mixture was heated to 60 °C and the hydrogen pressure was maintained at 1.0 MPa to initiate the reaction. The catalyst was a metal composite catalyst consisting of a carbon-supported Pt active metal component and a Mn auxiliary metal component. Based on the mass of the catalyst (100%), the mass percentage of Pt was 3% and the mass percentage of Mn was 0.5%. The reaction ended after 2 hours and 30 minutes. Samples were taken from the reactor and analyzed by liquid chromatography. The feed conversion rate was 100%, and the product chromatographic purity was 97.20%, with an excess hydrogenation impurity content of 0.52%.

[0060] Example 4

[0061] Preparation of catalyst 4:

[0062] a) Disperse 20g of silica carrier in 150ml of water;

[0063] b) The prepared mixed solution of sodium chloroplatinate and manganese nitrate metal salts was added to the silica carrier dispersion by gravity dropwise addition, with the feed rate controlled at 0.2 ml per minute. After the feed was completed, the mixture was stirred and dispersed for 12 h to obtain the impregnation solution composed of the metal mixed solution and the activated carbon carrier.

[0064] c) The catalyst reduction step: First, stabilize the impregnation solution at 80°C, then add 0.76g of ethylene glycol for reduction, keep stirring for 4 hours, and then wash and dry.

[0065] Catalytic applications:

[0066] Using a 500 mL reactor, 100 mL of ethanol solvent, 20.6 g of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, and 0.4 g of catalyst were added sequentially. The mixture was heated to 60 °C and the reaction was initiated while maintaining a hydrogen pressure of 1.0 MPa. The catalyst was a metal composite catalyst consisting of a Pt active metal component supported on a silica support and a Mn auxiliary metal component. Based on the mass of the catalyst (100%), the mass percentage of Pt was 2% and the mass percentage of Mn was 0.5%. The reaction ended after 2 hours. Samples were taken from the reactor and analyzed by liquid chromatography. The raw material conversion rate was 100%, and the product chromatographic purity was 97.00%, with an excess hydrogenation impurity content of 0.48%.

[0067] Comparative Example 1

[0068] Based on the catalytic reaction conditions of Example 1, and keeping other process conditions unchanged, 3% and 5% Pd carbon (commercially available catalysts, with Zhengzhou Alpha Chemical Co., Ltd. as optional suppliers) were selected as control experiments, as shown in Table 1.

[0069] Table 1. Comparison experiment between Pt carbon and Pd carbon

[0070]

[0071] The catalyst described in this invention produces fewer impurities and exhibits higher selectivity in the catalytic reduction reaction of 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole compared to 3% and 5% Pd carbon.

[0072] Applying the experiment

[0073] Based on the reaction conditions of Example 1, and keeping other process conditions unchanged, catalyst reuse experiments were conducted using the supported 3% Pt carbon described in this invention, commercially available 3% Pt carbon, and commercially available 3% Pd carbon. Specifically, the reaction was considered complete when the hydrogen consumption per minute no longer changed. Samples were taken from the reactor, analyzed, and the catalyst was separated from the reaction liquid. The separated catalyst was then reintroduced into the reactor, and 10% of the catalyst dosage was added to continue the next reactor reaction, which was considered one reuse. This process was repeated. The reuse results of the supported 3% Pt carbon described in this invention are shown in Table 2, and the reuse results of commercially available 3% Pt carbon are shown in Table 3.

[0074] Table 2 shows the experimental results of the supported 3% Pt carbon catalyst described in the invention.

[0075] Experiment 1 0 3h 96.90％ 0％ 0.29％ 100％ 96.90％ Experiment 2 1 4h 94.29％ 0％ 1.13％ 100％ 94.29％ Experiment 3 2 4h30min 95.48％ 0％ 1.12％ 100％ 95.48％ Experiment 4 3 4h 95.39％ 0％ 1.30％ 100％ 95.39％ Experiment 5 4 3h30min 95.62％ 0％ 1.07％ 100％ 95.62％ Experiment 6 5 4h 95.28％ 0％ 1.30％ 100％ 95.28％

[0076] Table 3 Experimental results using commercial 3% Pt carbon catalyst.

[0077] Experiment 1 0 4h 95.90％ 0％ 0.46％ 100％ 95.90％ Experiment 2 1 9h 94.60％ 0％ 1.36％ 100％ 94.60％ Experiment 3 2 17h 91.90％ 0％ 2.80％ 100％ 91.90％

[0078] When 3% Pd carbon is used as a catalyst, its reprocessing effect is poor due to its high impurity content, thus failing to achieve effective reprocessing. The catalyst described in this invention, however, can still control impurities at a low level after five reprocessing cycles and exhibits excellent selectivity.

[0079] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A process for the hydrogenation of a key intermediate of carfentrazone-ethyl, 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole, to 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole, characterized in that, Using 3-(2-methyl-6-nitrophenyl)-4,5-dihydroisoxazole as a raw material, 3-(2-methyl-6-aminophenyl)-4,5-dihydroisoxazole is prepared by reacting it with a recycled Pt catalyst and hydrogen in an organic solvent. The method for preparing the recycled Pt catalyst includes the following steps. a) Disperse the powder carrier in a solvent to obtain a powder carrier dispersion; the carrier is selected from any one of activated carbon, alumina, and silica. b) The mixed solution of Pt and auxiliary metal Fe or Mn metal salt is uniformly dispersed into the powder carrier dispersion obtained in step a) to obtain a metal / carrier impregnation solution; c) The metal / support impregnation solution is reduced to obtain a reusable Pt catalyst, wherein the Pt content in the catalyst is 1.0 to 3.0 wt% and the metal content of the auxiliary agent is 0.1 wt% to 0.5 wt%.

2. The method of claim 1, wherein, The solvent mentioned in step a) is selected from one or more of water, methanol, ethanol, benzene, and toluene; In step c), the reduction is carried out by adding a reducing agent or by reducing with hydrogen gas; the reducing agent is selected from one or more of NaBH4, KBH4, hydrazine hydrate, formic acid, citric acid, formaldehyde, and ethylene glycol.

3. The method according to claim 1, characterized in that, The organic solvent is selected from at least one of methanol, ethanol, and ethyl acetate; The reaction temperature is 20℃-100℃; The hydrogen pressure is 0.1 MPa-2.0 MPa.

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