A process for the preparation of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine

Abstract

This invention relates to the field of organic synthesis technology and discloses a method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. The method includes the following steps: a primary reaction is carried out in the presence of a first noble metal catalyst, involving methyl isopentyl ketone, p-phenylenediamine, and hydrogen; followed by a secondary reaction is carried out in the presence of a second noble metal catalyst, involving the mixture obtained after the primary reaction; wherein the temperature of the primary reaction is 20-70°C higher than that of the secondary reaction, and the temperature of the primary reaction is 100-150°C, while the temperature of the secondary reaction is 60-100°C. This method utilizes a noble metal catalyst in a fixed-bed staged catalytic synthesis of the antioxidant N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, which improves the conversion rate of raw materials and reduces side reactions in methyl isopentyl ketone and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, thereby improving product quality.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. Background Technology

[0002] Rubber products often undergo aging during use, including surface cracking, whitening, and a decline in physical and mechanical properties. These aging phenomena are partly due to the presence of unsaturated active groups in some rubbers, making them susceptible to reaction with oxygen, ozone, and other reactive substances, leading to the breakage and cross-linking of rubber chains. To manufacture more durable rubber products, substances are added to the rubber to inhibit these aging phenomena; these substances are called "antioxidants." Rubber antioxidants play a crucial role in the rubber industry, and common antioxidants include antioxidant 4020 (6PPD), antioxidant 4010NA (IPPD), and antioxidant 4030 (77PD).

[0003] Antioxidant 77PD is a slightly reddish to reddish-brown viscous liquid with a boiling point of 237℃, a flash point of 203℃, and a relative density of 0.90~0.91. Its chemical name is N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. Antioxidant 77PD is an effective ozone-resistant additive for natural rubber and various synthetic rubbers. Its static ozone aging resistance is excellent, significantly superior to antioxidants 4010NA and 6PPD, which also have excellent ozone aging resistance. It is particularly suitable for outdoor rubber products such as wires, cables, hoses, and tapes that are subjected to long-term static conditions, and can also be used in general industrial rubber products. Representative products include Santo flex 77PD from Flex Industries (USA), Vulkanox 77PD from Bayer (Germany), and Flexzone 4L from UniRoyal (USA). Antioxidant 77PD accelerates vulcanization and shortens scorch time in rubber compounds and can be used alone for certain rubber products with stringent requirements for resistance to static ozone aging. However, when used in natural rubber or styrene-butadiene rubber products, it exhibits poor flexural cracking resistance and is typically used in combination with antioxidants 4010NA and 6PPD to improve this resistance. Antioxidant 77PD is used as an ozone stabilizer in natural and general-purpose synthetic rubbers at a dosage of 1%–3%, and as a stabilizer in synthetic rubbers at a dosage of 0.5%–1%.

[0004] Currently, the synthesis process of antioxidant 77PD involves the reductive alkylation reaction of p-phenylenediamine and methyl isopentyl ketone in the presence of a catalyst. The reaction temperature is around 190-200℃, and the system pressure is maintained at 2.0-3.0 MPa. The entire reaction process and conditions are basically similar to those of antioxidants 6PPD and 4010NA, mainly consisting of hydrogen compression, feedstock feeding, reductive alkylation, and solvent recovery. There are reports of using p-nitroaniline as a raw material and employing a highly efficient noble metal catalyst to synthesize antioxidant 77PD in one step via reductive alkylation. However, because p-phenylenediamine has a lower melting point than RT-p-propanediol, and antioxidant 77PD also has a relatively low boiling point, it is necessary to control the reaction temperature to avoid excessively high temperatures and the volatilization of 77PD, which would affect the product yield. However, excessively low reaction temperatures can lead to incomplete reaction, also affecting the product yield. Therefore, reaction control is quite difficult. Noble metal catalysts exhibit high reaction selectivity, resulting in a smaller amount of the feedstock ketone being hydrogenated to an alcohol. At the same time, it can ensure that the reaction is carried out under relatively mild conditions, thus developing a highly efficient hydrogenation catalyst is beneficial to promoting the synthesis of antioxidant 77PD.

[0005] In the preparation of 77PD using a fixed-bed reactor with a noble metal supported catalyst, the high activity of the noble metal catalyst leads to an excess of methyl isopentyl ketone further reacting with the generated 77PD, producing a large number of impurities. When the reaction conditions are milder, the conversion rate of the feedstock p-phenylenediamine decreases, thus affecting the quality of 77PD. To address the above problems, this invention improves the selectivity of 77PD without reducing the conversion rate of p-phenylenediamine by segmented control of the fixed-bed reactor under the action of the noble metal supported catalyst. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem in the existing technology of preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine using noble metal catalysts, which makes it difficult to simultaneously achieve product purity and reactant conversion rate. This invention provides a method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. This method uses a noble metal catalyst in a fixed-bed staged catalytic synthesis of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, which improves the raw material conversion rate and reduces side reactions between methyl isopentyl ketone and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, thereby improving product quality.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, the method comprising the following steps: (1) Methyl isopentyl ketone, p-phenylenediamine and hydrogen are reacted in one step in the presence of a first noble metal catalyst; (2) In the presence of a second noble metal catalyst, the mixture obtained after the first reaction is subjected to a second reaction; The temperature of the primary reaction is 20-70°C higher than that of the secondary reaction, and the temperature of the primary reaction is 100-140°C, while the temperature of the secondary reaction is 60-100°C.

[0008] Preferably, the temperature of the primary reaction is 40-60°C higher than the temperature of the secondary reaction.

[0009] Preferably, the temperature of the primary reaction is 110-130℃, and the temperature of the secondary reaction is 70-90℃.

[0010] Preferably, the first noble metal catalyst and the second noble metal catalyst each contain a coconut shell carbon support and a Pt component, wherein the content of the Pt component is 0.1-1 wt%.

[0011] Preferably, the specific surface area of ​​the coconut shell charcoal carrier is ≥1000 m². 2 / g, pore volume is 0.3-2.5g / mL, pore size is 0.5-2.5nm, ash content is ≤5%, and water absorption rate is 40-60%.

[0012] Preferably, the ratio of the Pt component content in the first noble metal catalyst to the Pt component content in the second noble metal catalyst is 1:0.1-2.

[0013] Preferably, the ratio of the pore size of the coconut shell carbon support in the first precious metal catalyst to the pore size of the coconut shell carbon support in the second precious metal catalyst is 1:0.5-1.

[0014] Preferably, the primary reaction and the secondary reaction are carried out under the same pressure, and the reaction pressure of both is 0.8-1.5 MPa, preferably 1-1.2 MPa.

[0015] Preferably, the primary reaction and the secondary reaction are carried out in the same two-stage fixed-bed reactor. The mixture of methyl isopentyl ketone and p-phenylenediamine, along with hydrogen, enters through the bottom of the two-stage fixed-bed reactor, first undergoing the primary reaction with the catalyst bed formed by the first noble metal catalyst, and then undergoing the secondary reaction with the catalyst bed formed by the second noble metal catalyst.

[0016] Preferably, the volume hourly space velocity (VHSV) of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.1-0.8 h⁻¹. -1 Preferably 0.4-0.6h -1 .

[0017] Preferably, the volume ratio of the hydrogen gas to the mixture of methyl isopentyl ketone and p-phenylenediamine is 200-800:1, more preferably 400-600:1.

[0018] Preferably, the molar ratio of the methyl isopentyl ketone to the p-phenylenediamine is 2-5:1, more preferably 2.5-4:1.

[0019] The method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine according to this invention employs a noble metal catalyst in a fixed-bed staged catalytic synthesis of the antioxidant N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. This method not only improves the raw material conversion rate but also reduces side reactions between methyl isopentyl ketone and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, thereby improving product quality. The p-phenylenediamine conversion rate can reach over 92%, and the selectivity of the product N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine is over 96%. Furthermore, the method is continuous and simple to operate, avoiding catalyst loss caused by filtration when using powdered catalysts, thus improving product quality and reducing production costs. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine according to the present invention includes the following steps: (1) Methyl isopentyl ketone, p-phenylenediamine and hydrogen are reacted in one step in the presence of a first noble metal catalyst; (2) In the presence of a second noble metal catalyst, the mixture obtained after the first reaction is subjected to a second reaction; The temperature of the primary reaction is 20-70°C higher than that of the secondary reaction, and the temperature of the primary reaction is 100-140°C, while the temperature of the secondary reaction is 60-100°C.

[0023] In a preferred embodiment, the temperature of the primary reaction is 40-60°C higher than the temperature of the secondary reaction; the temperature of the primary reaction is 110-130°C, and the temperature of the secondary reaction is 70-90°C. In these preferred embodiments, when the temperatures of the primary and secondary reactions are within the above ranges, the method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine exhibits higher selectivity and yield.

[0024] In this invention, the first noble metal catalyst and the second noble metal catalyst can be selected from the same type of noble metal catalyst or from different types of noble metal catalyst, preferably from different types of catalyst.

[0025] In a preferred embodiment, both the first and second noble metal catalysts contain a coconut shell carbon support and a Pt component, wherein the Pt component content can be 0.1-1 wt%. In these preferred embodiments, when the first and second noble metal catalysts contain the above-mentioned components, the method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine exhibits higher selectivity and yield.

[0026] In this invention, the specific surface area of ​​the coconut shell charcoal carrier can be ≥1000m². 2 / g, preferably 1000-1250m 2 / g; pore volume can be 0.3-2.5g / mL, preferably 0.5-1.5g / mL; pore size can be 0.5-2.5nm, preferably 0.5-2.0nm; ash content can be ≤5%, preferably ≤4%; water absorption rate can be 40-60%, preferably 50-60%. In this invention, when the pore structure and water absorption rate of the coconut shell carbon support are within the above ranges (especially the preferred ranges), the first noble metal catalyst and the second noble metal catalyst have better catalytic activity and selectivity.

[0027] In this invention, the ratio of Pt content in the first noble metal catalyst to Pt content in the second noble metal catalyst can be 1:0.1-2, preferably 1:1-2. In this invention, when the ratio of Pt content in the first noble metal catalyst to Pt content in the second noble metal catalyst is within the above range (especially the preferred range), the method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine has higher selectivity and yield.

[0028] In this invention, the ratio of the pore size of the coconut shell carbon support in the first noble metal catalyst to that in the second noble metal catalyst can be 1:0.5-1, preferably 1:0.8-1. In this invention, when the ratio of the pore size of the coconut shell carbon support in the first noble metal catalyst to that in the second noble metal catalyst is within the above-mentioned range (especially the preferred range), the method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine has higher selectivity and yield.

[0029] In the method described in this invention, the primary reaction and the secondary reaction are carried out under the same pressure, and the reaction pressure can be 0.8-1.5 MPa, preferably 1-1.2 MPa. In the method described in this invention, when the pressures of the primary reaction and the secondary reaction are within the above range (especially the preferred range), the preparation method of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine has higher selectivity and yield.

[0030] In some embodiments, the primary reaction and the secondary reaction are carried out in the same two-stage fixed-bed reactor. A mixture of methyl isopentyl ketone and p-phenylenediamine, along with hydrogen, enters through the bottom of the two-stage fixed-bed reactor, first reacting with a catalyst bed formed by the first noble metal catalyst, and then reacting with a catalyst bed formed by the second noble metal catalyst.

[0031] In the method described in this invention, the volume hourly space velocity (VHSV) of the mixture of methyl isopentyl ketone and p-phenylenediamine can be 0.1-0.8 h⁻¹. -1 Preferably 0.4-0.6h -1 In the method described in this invention, when the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is within the range described above (especially the preferred range), the conversion rate of p-phenylenediamine and methyl isopentyl ketone is higher.

[0032] In the method described in this invention, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine can be 200-800:1, preferably 400-600:1. In the method described in this invention, when the volume hourly space velocity (VHSV) of the mixture of methyl isopentyl ketone and p-phenylenediamine is within the above-mentioned range (especially the preferred range), the conversion rate of p-phenylenediamine and methyl isopentyl ketone is higher.

[0033] In the method described in this invention, the molar ratio of methyl isopentyl ketone to p-phenylenediamine can be 2-5:1, preferably 2.5-4:1. In the method described in this invention, when the molar ratio of methyl isopentyl ketone to p-phenylenediamine is within the above range (especially the preferred range), the conversion rate of p-phenylenediamine and methyl isopentyl ketone is higher.

[0034] In some embodiments, the preparation method of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine may include: mixing methyl isopentyl ketone with p-phenylenediamine, then introducing the resulting mixture from the bottom of a two-stage fixed-bed reactor into a first reaction section, while simultaneously introducing hydrogen gas into the first reaction section to carry out a primary reaction. The first reaction section is supported on a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 2-5:1, the volume ratio of hydrogen gas to the mixture of methyl isopentyl ketone and p-phenylenediamine is 200-800:1, and the volume hourly space velocity (VHSV) of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.1-0.8 h⁻¹. -1 The primary reaction is carried out at a pressure of 0.8-1.5 MPa, a temperature of 100-140℃, and a time of 1-20 h. The first noble metal catalyst contains 0.1-1 wt% Pt and coconut shell charcoal, wherein the specific surface area of ​​the coconut shell charcoal is ≥1000 m². 2 / g, pore volume is 0.3-2.5g / mL, pore size is 0.5-2.5nm, ash content is ≤5%, and water absorption rate is 40-80%; The effluent from the first reaction section enters a second reaction section for a secondary reaction. The second reaction section is supported by a second noble metal catalyst. The pressure of the secondary reaction is 0.8-1.5 MPa, the reaction temperature is 60-100 °C, and the reaction time is 1-10 h. The ratio of Pt content in the first noble metal catalyst to Pt content in the second noble metal catalyst can be 1:0.1-2, and the ratio of pore size of the coconut shell carbon support in the first noble metal catalyst to pore size of the coconut shell carbon support in the second noble metal catalyst can be 1:0.5-1. When the preparation method is implemented according to this embodiment, the preparation method of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine has higher selectivity and yield.

[0035] The following examples further illustrate the preparation method of N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0036] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples and comparative examples are commercially available.

[0037] Example 1 (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 1.2 MPa, a temperature of 120°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The pressure of the secondary reaction is 1.2 MPa, the reaction temperature is 70°C, and the reaction time is 1.67 h. The second noble metal catalyst contains 0.25 wt% Pt and coconut shell charcoal, and the specific surface area of ​​the coconut shell charcoal is 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0038] Example 2 (1) Mix 375 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 5:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 800:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.8 h⁻¹. -1The primary reaction was carried out at a pressure of 1.5 MPa, a temperature of 140°C, and a time of 2.08 h. The first noble metal catalyst contained 0.3 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 40%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The secondary reaction is carried out at a pressure of 1.5 MPa, a temperature of 100°C, and a time of 1.04 h. The second noble metal catalyst contains 0.15 wt% Pt and coconut shell charcoal, with the coconut shell charcoal having a specific surface area of ​​1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 0.86nm, ash content is 3%, and water absorption rate is 40%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0039] Example 3 (1) Mix 150 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 2:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 200:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.2 h⁻¹. -1 The primary reaction was carried out at a pressure of 0.8 MPa, a temperature of 100°C, and a time of 8.33 h. The first noble metal catalyst contained 0.2 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 40%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The secondary reaction is carried out at a pressure of 0.8 MPa, a temperature of 60°C, and a time of 4.16 h. The second noble metal catalyst contains 0.1 wt% Pt and coconut shell charcoal, with the coconut shell charcoal having a specific surface area of ​​1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 40%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0040] Example 4 (1) Mix 600 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 8:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 100:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.1 h⁻¹. -1 The primary reaction was carried out at a pressure of 2.0 MPa, a temperature of 130°C, and a time of 16.67 h. The first noble metal catalyst contained 0.1 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 40%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The pressure of the secondary reaction is 2.0 MPa, the reaction temperature is 60°C, and the reaction time is 8.33 h. The second noble metal catalyst contains 0.01 wt% Pt and coconut shell charcoal, and the specific surface area of ​​the coconut shell charcoal is 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 40%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0041] Example 5 (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1The primary reaction was carried out at a pressure of 2.0 MPa, a temperature of 150°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The secondary reaction is carried out at a pressure of 2.0 MPa, a temperature of 90°C, and a time of 1.67 h. The second noble metal catalyst contains 0.1 wt% Pt and coconut shell charcoal, with the coconut shell charcoal having a specific surface area of ​​1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0042] Example 6 (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into a first fixed-bed reactor from the bottom. Simultaneously, introduce hydrogen gas into the first fixed-bed reactor to carry out a primary reaction. The first fixed-bed reactor is equipped with a first noble metal catalyst bed. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen gas to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 0.8 MPa, a temperature of 100°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The reaction effluent from the first fixed-bed reactor enters a second fixed-bed reactor via a pipeline for a secondary reaction. The second fixed-bed reactor is equipped with a second noble metal catalyst bed. The secondary reaction is carried out at a pressure of 0.8 MPa, a temperature of 60°C, and a time of 1.67 h. The first noble metal catalyst contains 1 wt% Pt and coconut shell charcoal, with the coconut shell charcoal having a specific surface area of ​​1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0043] Comparative Example 1 This comparative example was carried out according to the method described in Example 1, except that in step (1), the temperature of both the first and second reactions was 100°C. The specific steps included: (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 1.2 MPa, a temperature of 100°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The pressure of the secondary reaction is 1.2 MPa, the reaction temperature is 100 °C, and the reaction time is 1.67 h. The second noble metal catalyst contains 0.25 wt% Pt and coconut shell charcoal, and the specific surface area of ​​the coconut shell charcoal is 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0044] Comparative Example 2 This comparative example was carried out according to the method described in Example 1, except that in step (1), the temperature of the primary reaction was 150°C and the temperature of the secondary reaction was 110°C. The specific steps included: (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a first noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 1.2 MPa, a temperature of 150°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is supported on a second noble metal catalyst. The pressure of the secondary reaction is 1.2 MPa, the reaction temperature is 110 °C, and the reaction time is 1.67 h. The second noble metal catalyst contains 0.25 wt% Pt and coconut shell charcoal, and the specific surface area of ​​the coconut shell charcoal is 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0045] Comparative Example 3 This comparative example was carried out according to the method described in Example 1, except that in step (1), the first reaction section and the second reaction section were respectively loaded with copper-based catalysts. The specific steps included: (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into the first reaction section from the bottom of a two-stage fixed-bed reactor. Simultaneously, introduce hydrogen into the first reaction section to carry out a single reaction. The first reaction section is loaded with a copper-based catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 1.2 MPa, a temperature of 120°C, and a time of 3.33 h. The copper-based catalyst contained 0.5 wt% Cu and coconut shell charcoal, with the coconut shell charcoal having a specific surface area of ​​1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; The effluent from the first reaction section enters the second reaction section for a secondary reaction. The second reaction section is loaded with a copper-based catalyst. The pressure of the secondary reaction is 1.2 MPa, the reaction temperature is 70°C, and the reaction time is 1.67 h. The copper-based catalyst contains 0.25 wt% Cu and coconut shell charcoal, and the specific surface area of ​​the coconut shell charcoal is 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1.1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0046] Comparative Example 4 This comparative example is carried out according to the method described in Example 1, except that in step (1), only a fixed-bed reactor is used for a single reaction, without setting a second reaction section or performing a secondary reaction. The specific steps include: (1) Mix 225 mL of methyl isopentyl ketone with 73 g of p-phenylenediamine, and then introduce the resulting mixture into a fixed-bed reactor from the bottom while simultaneously introducing hydrogen gas into the fixed-bed reactor to carry out the reaction. The fixed-bed reactor is loaded with a noble metal catalyst. The molar ratio of methyl isopentyl ketone to p-phenylenediamine is 3:1, the volume ratio of hydrogen gas to the mixture of methyl isopentyl ketone and p-phenylenediamine is 500:1, and the volume hourly space velocity of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.5 h⁻¹. -1 The primary reaction was carried out at a pressure of 1.2 MPa, a temperature of 120°C, and a time of 3.33 h. The first noble metal catalyst contained 0.5 wt% Pt and coconut shell charcoal, the specific surface area of ​​which was 1200 m². 2 / g, pore volume is 1.5g / mL, pore size is 1nm, ash content is 3%, and water absorption rate is 50%; (2) The reaction product obtained in step (1) was distilled at 170°C for 1 h to separate N,N'-bis(1,4-dimethylpentyl)p-phenylenediamine.

[0047] Test case This test example is used to determine the conversion rate, selectivity, and ketone-to-alcohol ratio of p-phenylenediamine in the reactions described in Examples 1-6 and Comparative Examples 1-4. The reaction products obtained in step (1) of Examples 1-6 and Comparative Examples 1-4 were tested by gas chromatography. The specific steps and operating methods are in accordance with industry standard HG / T4897-2016.

[0048] The conversion rate of p-phenylenediamine was calculated using the following formula: ((amount of p-phenylenediamine - (p-phenylenediamine and methyl isopentyl ketone) × peak area of ​​p-phenylenediamine in the reaction product) / amount of p-phenylenediamine) × 100%. The results are shown in Table 1.

[0049] Table 1

[0050] As shown in Table 1, by adopting the technical solution described in this invention, the conversion rate of p-phenylenediamine in the preparation of N-isopropyl-N'-phenyl in Examples 1-6 can reach over 92%, and the selectivity can reach over 96%. In the preparation of N-isopropyl-N'-phenyl in the preferred Examples 1-3, the conversion rate, selectivity, ketol ratio, and 77PD content of p-phenylenediamine are further improved compared with the non-preferred Examples 4-6, with the conversion rate of p-phenylenediamine reaching over 98.59% and the selectivity reaching over 98.31%. However, the selectivity of Comparative Examples 1 and 2 is much worse than that of Examples 1-6 due to the excessively high reaction temperatures in the two stages and the excessively high secondary reaction temperature, respectively. The conversion rate and selectivity of p-phenylenediamine in Comparative Examples 3 and 4 are much worse than those of Examples 1-6 due to the poor catalytic activity of the catalyst used and the lack of a secondary reaction, respectively.

[0051] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, characterized in that, The method includes the following steps: (1) Methyl isopentyl ketone, p-phenylenediamine and hydrogen are reacted in one step in the presence of a first noble metal catalyst; (2) In the presence of a second noble metal catalyst, the mixture obtained after the first reaction is subjected to a second reaction; The temperature of the primary reaction is 20-70°C higher than that of the secondary reaction, and the temperature of the primary reaction is 100-150°C, while the temperature of the secondary reaction is 60-100°C.

2. The method according to claim 1, characterized in that, The temperature of the primary reaction is 40-60°C higher than the temperature of the secondary reaction.

3. The method according to claim 1 or 2, characterized in that, The temperature of the primary reaction is 110-130℃, and the temperature of the secondary reaction is 70-90℃.

4. The method according to any one of claims 1-3, characterized in that, Both the first and second noble metal catalysts contain coconut shell carbon support and Pt component, wherein the Pt component content is 0.1-1 wt%. Preferably, the specific surface area of ​​the coconut shell charcoal carrier is ≥1000 m². 2 / g, pore volume is 0.3-2.5g / mL, pore size is 0.5-2.5nm, ash content is ≤5%, and water absorption rate is 40-60%.

5. The method according to claim 4, characterized in that, The ratio of Pt content in the first noble metal catalyst to Pt content in the second noble metal catalyst is 1:0.1-2; and / or The ratio of the pore size of the coconut shell carbon support in the first precious metal catalyst to the pore size of the coconut shell carbon support in the second precious metal catalyst is 1:0.5-1.

6. The method according to any one of claims 1-5, characterized in that, The primary and secondary reactions are carried out under the same pressure, and the reaction pressure for both is 0.8-1.5 MPa, preferably 1-1.2 MPa.

7. The method according to any one of claims 1-6, characterized in that, The primary reaction and the secondary reaction are carried out in the same two-stage fixed-bed reactor. The mixture of methyl isopentyl ketone and p-phenylenediamine, along with hydrogen, enters through the bottom of the two-stage fixed-bed reactor. The primary reaction is carried out first with the catalyst bed formed by the first noble metal catalyst, and then the secondary reaction is carried out with the catalyst bed formed by the second noble metal catalyst.

8. The method according to claim 7, characterized in that, The volume hourly space velocity (VHSV) of the mixture of methyl isopentyl ketone and p-phenylenediamine is 0.1–0.8 h⁻¹. -1 Preferably 0.4-0.6h -1 .

9. The method according to claim 7, characterized in that, The volume ratio of the hydrogen gas to the mixture of methyl isopentyl ketone and p-phenylenediamine is 200-800:1, preferably 400-600:

1.

10. The method according to any one of claims 1-9, characterized in that, The molar ratio of the methyl isopentyl ketone to the p-phenylenediamine is 2-5:1, preferably 2.5-4:1.

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