Method and system for preparing p-phenylenediamine anti-aging agent

Abstract

The invention relates to the technical field of organic synthesis, and discloses a method and a system for preparing a p-phenylenediamine anti-aging agent. The method comprises the following steps: (1) in the presence of a molecular sieve, carrying out dehydration condensation reaction on acetone and RT base to obtain a first mixed solution containing Schiff base; (2) in the presence of a hydrogenation catalyst, carrying out hydrogenation reaction on the first mixed solution containing the Schiff base to obtain a second mixed solution; and (3) carrying out separation and crystallization on the second mixed solution to obtain the anti-aging agent 4010NA and the anti-aging agent 6PPD. By adopting the method and the system provided by the invention, the anti-aging agents 4010NA and 6PPD can be co-produced, and compared with a one-step condensation hydrogenation process, the proportion of 4010NA and 6PPD in the product can be flexibly controlled within a certain range, the proportion of 6PPD in the product is increased, and the prepared anti-aging agent product is high in purity.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method and system for preparing a p-phenylenediamine antioxidant. Background Art

[0002] Antioxidant 6PPD, also known as antioxidant 4020, belongs to the p-phenylenediamine antioxidant and is one of the general antioxidant varieties with excellent performance among amine antioxidants. It has balanced anti-aging properties, is used in the largest amount among antioxidant varieties, and occupies a dominant position in the market. Antioxidant 4010NA, as another important p-phenylenediamine antioxidant, has good effects on preventing ozone aging, metal aging, and resisting flexion, fatigue, cracking, etc. It is suitable for industrial rubber products working under static, dynamic or intermittent conditions.

[0003] The mainstream process for preparing antioxidants 4010NA and 6PPD is the reduction alkylation method using ketone and RT base as raw materials. The synthesis mechanism of the two antioxidants is as follows:

[0004] Acetone and RT base are condensed and hydrogenated to produce antioxidant 4010NA in one step:

[0005]

[0006] In the above process, acetone undergoes self-condensation and hydrogenation to form methyl isobutyl ketone (MIBK):

[0007]

[0008] MIBK and RT base are condensed and hydrogenated to produce antioxidant 6PPD:

[0009]

[0010] The raw ketone for preparing 4010NA is acetone, and the raw ketone for preparing 6PPD is MIBK. MIBK is mainly obtained by condensation and hydrogenation of acetone. Therefore, in the actual industrial production of 4010NA, 6PPD by-products often appear. Since there is no special process optimization and the 6PPD content is low, about 95% of the 4010NA finished products are generally produced by mixing and compounding. This method not only affects the quality of 4010NA, but also wastes high value-added products MIBK and 6PPD. In the existing preparation process, due to the lack of treatment or restriction of acetone before the hydrogenation reaction, there is currently no effective method to control the composition of the product ingredients.

[0011] As the requirements for the quality and diversity of antioxidant products continue to increase, there is an urgent need to provide an optimized and improved production process that can achieve flexible production according to actual product type requirements and can obtain high-purity antioxidants 4010NA and 6PPD. Summary of the invention

[0012] Aiming at the problem that the existing preparation process of p-phenylenediamine antioxidant is difficult to realize the co-production of 4010NA and 6PPD, and the problem that the purity of the prepared 4010NA and 6PPD products needs to be further improved, the present invention provides a method and system for preparing p-phenylenediamine antioxidant.

[0013] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a p-phenylenediamine antioxidant, comprising:

[0014] (1) in the presence of molecular sieves, subjecting acetone to a dehydration condensation reaction with RT base to obtain a first mixed solution containing a Schiff base;

[0015] (2) subjecting the first mixed solution containing the Schiff base to a hydrogenation reaction in the presence of a hydrogenation catalyst to obtain a second mixed solution;

[0016] (3) The second mixed solution is separated and crystallized to obtain antioxidant 4010NA and antioxidant 6PPD.

[0017] The second aspect of the present invention provides a system for preparing a p-phenylenediamine antioxidant, the system comprising a dehydration condensation unit A, a hydrogenation unit B and a separation crystallization unit C connected in sequence;

[0018] The dehydration condensation unit A is used to carry out a dehydration condensation reaction on acetone and RT base to obtain a first mixed solution containing Schiff base;

[0019] The hydrogenation unit B is used to hydrogenate the first mixed liquid containing Schiff base to obtain a second mixed liquid;

[0020] The separation and crystallization unit C is used to separate and crystallize the second mixed solution to obtain antioxidant 4010NA and antioxidant 6PPD.

[0021] Through the above technical scheme, the present invention adopts a multi-step reaction method, first promotes the condensation reaction of raw material acetone and RT base with a water-absorbing molecular sieve, synthesizes a Schiff base with a controllable concentration, and then hydrogenates under the action of a noble metal catalyst to obtain an antioxidant 4010NA and an antioxidant 6PPD mixture, and then undergoes separation and crystallization treatment to obtain two high-purity antioxidant products. Compared with the one-step process of the prior art, the method for preparing a p-phenylenediamine antioxidant provided by the present invention can co-produce 4010NA and 6PPD, and the proportion of 6PPD in the product is increased, and the flexible production of products 4010NA and 6PPD within a certain ratio range can be achieved, and the purity of the product can be improved. The product purity of the obtained antioxidant 4010NA is greater than 95% by weight, and can be greater than 99% by weight at most, and the product purity of the antioxidant 6PPD is greater than 98% by weight, and can be greater than 99% by weight at most. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 The schematic diagram of the system for preparing p-phenylenediamine antioxidant of the present invention is shown in FIG.

[0024] Description of Reference Numerals

[0025] A-dehydration condensation unit B-hydrogenation unit C-separation crystallization unit

[0026] 1-Dehydration condensation reactor 2-Storage tank 3-Hydrogenation reactor

[0027] 4-First separation tower 5-Second separation tower 6-First crystallizer

[0028] 7- Second crystallizer DETAILED DESCRIPTION

[0029] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] In a first aspect, the present invention provides a method for preparing a p-phenylenediamine antioxidant, comprising:

[0032] (1) in the presence of molecular sieves, subjecting acetone to a dehydration condensation reaction with RT base to obtain a first mixed solution containing a Schiff base;

[0033] (2) subjecting the first mixed solution containing the Schiff base to a hydrogenation reaction in the presence of a hydrogenation catalyst to obtain a second mixed solution;

[0034] (3) The second mixed solution is separated and crystallized to obtain antioxidant 4010NA and antioxidant 6PPD.

[0035] In the existing one-step condensation hydrogenation process for synthesizing antioxidant 4010NA and by-product 6PPD, water is generated during the condensation reaction of raw materials acetone and RT base, which reduces the generation rate of Schiff base and affects the catalytic activity of the precious metal catalyst. In addition, the one-step synthesis process has poor process controllability, and it is difficult to control the condensation of acetone and RT base and the self-condensation of acetone, resulting in low controllability of the component composition of the antioxidant 4010NA product. The inventors of the present invention recognize the above-mentioned defects and adopt an optimized and improved multi-step synthesis process. First, a dehydration condensation reaction of the raw materials acetone and RT base is carried out. By adjusting the conditions of the condensation reaction, the ratio of the product Schiff base and 4-methyl-3-pentene-2-one (acetone self-condensation product) can be controlled. The use of water-absorbing molecular sieves can promote the above-mentioned condensation reaction and reduce the water content of the product. The product of the condensation reaction is then hydrogenated, and finally the hydrogenated product is separated and crystallized. Through the above-mentioned multi-step synthesis process, 4010NA and 6PPD can be co-produced. Compared with the one-step process, the ratio of 4010NA to 6PPD in the product can be flexibly controlled within a certain range, and the ratio of 6PPD in the product is increased, and the purity of the product is higher.

[0036] According to the present invention, in step (1), the molecular sieve can adsorb part of the water generated in the dehydration condensation reaction, which is conducive to the more controllable generation of Schiff base. Preferably, the average pore size of the molecular sieve is

[0037] According to the present invention, preferably, the molecular sieve is 3A molecular sieve and / or 4A molecular sieve, and more preferably is 4A molecular sieve.

[0038] In the present invention, the definition of the 4A molecular sieve is relatively broad, as long as it can achieve the adsorption of molecules with a diameter of less than 400 pm, and it can be obtained by self-production using conventional methods or by using commercially available products.

[0039] According to the present invention, in step (1), for the implementation process of the dehydration condensation reaction, the raw material acetone and RT base (p-aminodiphenylamine) can be mixed, and the dehydration condensation reaction can be carried out in the presence of the molecular sieve to obtain a first mixed solution containing Schiff base. The conditions of the dehydration condensation reaction include: the pressure is normal pressure, the temperature is 60-80°C, and the total volume space velocity of acetone and RT base is 0.1-0.5h -1 .

[0040] According to the present invention, preferably, the dehydration condensation reaction is carried out under a protective atmosphere, such as a nitrogen atmosphere, a neon atmosphere, an argon atmosphere, etc., preferably a nitrogen atmosphere.

[0041] According to the present invention, in step (1), preferably, the molar ratio of acetone:RT base is (3-5):1.

[0042] According to the present invention, in step (1), the Schiff base refers to N-isopropylidene-N'-phenyl-p-phenylenediamine obtained by dehydration condensation of acetone and RT base.

[0043] According to the present invention, in step (1), the first mixed solution containing Schiff base is a liquid phase mixed system, which contains, in addition to the Schiff base, remaining unreacted raw materials acetone, RT base, and 4-methyl-3-penten-2-one.

[0044] According to the present invention, in step (1), the water content in the first mixed solution containing the Schiff base is less than 1% by weight. The excellent water absorption of the molecular sieve is utilized to effectively control the water content in the reaction system, which is beneficial to the forward progress of the dehydration condensation reaction and can reduce the influence of water on the activity of the noble metal catalyst in the subsequent hydrogenation reaction.

[0045] According to the present invention, in step (2), the Schiff base in the first mixed solution containing the Schiff base is converted into (i.e. antioxidant 4010NA), at the same time, in step (2), 4-methyl-3-pentene-2-one in the first mixed solution containing Schiff base is converted into methyl isobutyl ketone by hydrogenation reaction, and then methyl isobutyl ketone is dehydrated and condensed with RT base to obtain 6PPD precursor, and then the 6PPD precursor is hydrogenated to obtain (i.e. antioxidant 6PPD) to obtain the second mixed solution.

[0046] According to the present invention, in step (2), for the implementation process of the hydrogenation reaction, the first mixed liquid containing Schiff base can be mixed with hydrogen, and the hydrogenation reaction is carried out under the action of the hydrogenation catalyst. Preferably, the conditions of the hydrogenation reaction include: pressure of 0.4-1.5MPa, preferably 0.8-1.2MPa; temperature of 80-150°C, preferably 90-120°C; volume hydrogen-oil ratio of (100-700):1, preferably (100-300):1; volume space velocity of the first mixed liquid containing Schiff base is 0.1-0.5h -1 , preferably 0.2-0.35h -1 .

[0047] According to the present invention, in step (2), the hydrogenation catalyst is limited to a wide range, and the conventional hydrogenation catalyst required for preparing p-phenylenediamine antioxidants in the art can be used. Preferably, the hydrogenation catalyst is a supported catalyst, including a carrier and an active component; wherein the carrier can be selected from at least one of coconut shell activated carbon, alumina and silicon dioxide, preferably coconut shell activated carbon; further preferably, the specific surface area of ​​the coconut shell activated carbon carrier is 800-1200m 2 / g, pore volume of 0.3-2.5g / ml, pore size of 0.5-2.5nm, ash content less than 5%, water absorption rate greater than 60%; the active component can be selected from at least one of Pt, Pd and Ni, preferably Pt; the weight ratio of the active component: carrier is (0.1-5): 100. In the present invention, it is further preferred that the hydrogenation catalyst can be selected from at least one of the catalyst with the brand GX (manufacturer is Hunan Minstrom Zhuang Technology Co., Ltd.) and the catalyst with the brand P111328 (manufacturer is Shanghai Aladdin Biochemical Technology Co., Ltd.).

[0048] According to the present invention, in step (3), the separation crystallization further comprises the following steps:

[0049] (3-1) separating the second mixed liquid to obtain acetone, methyl isobutyl ketone and a separated liquid; wherein the acetone and methyl isobutyl ketone are returned to step (1) to participate in the dehydration condensation reaction;

[0050] (3-2) The separated liquid is subjected to crystallization treatment to obtain antioxidant 4010NA and antioxidant 6PPD.

[0051] According to the present invention, in step (3-1), the separation treatment includes a first distillation and a second distillation performed sequentially. The first distillation is used to separate the acetone in the second mixed solution, and then the second distillation is used to separate the methyl isobutyl ketone in the second mixed solution. The separated acetone and methyl isobutyl ketone are respectively returned to step (1) to continue to participate in the reaction and be reused.

[0052] According to the present invention, the first distillation is preferably carried out in a distillation tower. Preferably, the conditions of the first distillation include: tower pressure of 0.1-0.3 MPa; tower top temperature of 50-60°C, tower bottom temperature of 90-100°C; and reflux ratio of 4-5.

[0053] According to the present invention, the second distillation is preferably carried out in a distillation tower. Preferably, the conditions of the second distillation include: tower pressure of 0.1-0.3 MPa; tower top temperature of 110-120°C, tower bottom temperature of 140-150°C; and reflux ratio of 4-5.

[0054] According to the present invention, after the separation treatment, the main components of the separated liquid are antioxidant 4010NA and antioxidant 6PPD. Preferably, the sum of the contents of acetone and methyl isobutyl ketone in the separated liquid is less than 15% by weight.

[0055] According to the present invention, in step (3-2), the crystallization treatment includes a first crystallization and a second crystallization performed sequentially, wherein the antioxidant product 4010NA is separated out by the first crystallization, and then the antioxidant product 6PPD is separated out by the second crystallization.

[0056] According to the present invention, in order to obtain a better crystallization separation effect, preferably, the temperature of the first crystallization is 50-60°C; and the temperature of the second crystallization is 30-40°C.

[0057] The method for preparing a p-phenylenediamine antioxidant provided by the present invention has strong continuous operability, can realize flexible production of 4010NA and 6PPD within a certain ratio range according to product type requirements, and compared with the existing one-step condensation hydrogenation synthesis process, the conversion rate of the raw material RT base is higher, the problem of by-product water can be solved, the reaction conditions are milder, and the product quality is better, and the product purity of the antioxidant 4010NA can be greater than 95% by weight, and the product purity of the antioxidant 6PPD can be greater than 98% by weight.

[0058] The second aspect of the present invention provides a system for preparing a p-phenylenediamine antioxidant, such as Figure 1 As shown, the system includes a dehydration condensation unit A, a hydrogenation unit B and a separation crystallization unit C connected in sequence;

[0059] The dehydration condensation unit A is used to carry out a dehydration condensation reaction on acetone and RT base to obtain a first mixed solution containing Schiff base;

[0060] The hydrogenation unit B is used to hydrogenate the first mixed liquid containing Schiff base to obtain a second mixed liquid;

[0061] The separation and crystallization unit C is used to separate and crystallize the second mixed solution to obtain antioxidant 4010NA and antioxidant 6PPD.

[0062] According to the present invention, in the system for preparing a paraphenylenediamine antioxidant, the dehydration condensation unit A comprises a dehydration condensation reactor 1 and a storage tank 2 connected in sequence. The dehydration condensation reactor 1 can be any reactor capable of carrying out a dehydration condensation reaction of acetone and RT base, and the present invention has no particular limitation thereto. The storage tank 2 is used to store the first mixed solution containing the Schiff base.

[0063] According to the present invention, in the system for preparing p-phenylenediamine antioxidant, the hydrogenation unit B includes a hydrogenation reactor 3, and the hydrogenation reactor 3 is connected to the storage tank 2. The hydrogenation reactor 3 can be any reactor that can realize the hydrogenation reaction of liquid raw materials with hydrogen, and the present invention has no special limitation on it.

[0064] According to the present invention, in the system for preparing paraphenylenediamine antioxidant, the separation crystallization unit C includes a first separation tower 4, a second separation tower 5, a first crystallizer 6 and a second crystallizer 7 connected in sequence; wherein the first separation tower 4 is connected to the hydrogenation reactor 3.

[0065] In the present invention, the first separation tower 4 and the second separation tower 5 are preferably distillation towers, which are used to sequentially distill and separate acetone and methyl isobutyl ketone from the second mixed liquid obtained after hydrogenation to obtain separated liquid after separation.

[0066] In the present invention, the first crystallizer 6 and the second crystallizer 7 are preferably external circulation cooling crystallizers, which are used to crystallize and separate the antioxidant 4010NA and the antioxidant 6PPD in the separation liquid in turn to obtain a high-purity antioxidant product.

[0067] According to the present invention, preferably, the first separation tower 4 and the second separation tower 5 are respectively connected to the dehydration condensation reactor 1. Specifically, the top discharge ports of the first separation tower 4 and the second separation tower 5 are respectively connected to the feed port of the dehydration condensation reactor 1, so as to return the acetone and methyl isobutyl ketone separated by rectification to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction and realize reuse.

[0068] The system for preparing p-phenylenediamine antioxidant provided by the present invention can realize flexible production of 4010NA and 6PPD within a certain ratio range according to product type requirements through a dehydration condensation unit A and a hydrogenation unit B that are separately arranged, and can achieve more thorough separation of different products through crystallization in a separation crystallization unit C according to differences in solubility and melting point of the products, thereby obtaining a high-purity product.

[0069] The following combination Figure 1 The invention describes a method for preparing a p-phenylenediamine antioxidant by using the system provided by the invention.

[0070] Acetone and RT base were mixed in a molar ratio of (3-5):1 and entered the dehydration condensation unit A, first entering the molecular sieve (average pore size ) in a dehydration condensation reactor 1, and a dehydration condensation reaction is carried out under a nitrogen atmosphere (the reaction temperature is 60-80° C., and the total volume space velocity of acetone and RT base is 0.1-0.5h -1), to obtain a first mixed solution containing Schiff base (wherein the water content is less than 1 wt%), and to feed it into a storage tank 2; the first mixed solution containing Schiff base enters the hydrogenation unit B from the storage tank 2, is mixed with hydrogen in the hydrogenation reactor 3, and undergoes a hydrogenation reaction under the action of a hydrogenation catalyst (pressure of 0.4-1.5 MPa; temperature of 80-150° C.; hydrogen-to-oil ratio of 100-700; volume space velocity of the first mixed solution containing Schiff base of 0.1-0.5 h -1 ) to obtain a second mixed solution; the second mixed solution enters the separation crystallization unit C, first enters the first separation tower 4 (tower pressure is 0.1-0.3MPa; tower top temperature is 50-60°C, tower bottom temperature is 90-100°C; reflux ratio is 4-5) for the first distillation to separate acetone, and then enters the second separation tower 5 (tower pressure is 0.1-0.3MPa; tower top temperature is 110-120°C, tower bottom temperature is 90-100°C; reflux ratio is 4-5) for the second distillation to separate methyl isobutyl ketone, and the separated acetone and methyl isobutyl ketone The acetone is returned from the top of the first separation tower 4 and the top of the second separation tower 5 to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction, and a separation liquid (wherein the sum of the contents of acetone and methyl isobutyl ketone is less than 15 weight %) is obtained at the bottom of the second separation tower 5; the separation liquid enters the first crystallizer 6 (crystallization temperature is 50-60°C) for the first crystallization to separate and obtain a high-purity antioxidant product 4010NA, and the remaining liquid phase enters the second crystallizer 7 (crystallization temperature is 30-40°C) for the second crystallization to obtain a high-purity antioxidant product 6PPD.

[0071] The present invention will be described in detail below by way of examples. In the following examples and comparative examples,

[0072] 3A molecular sieve: brand XFF23-102485, purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with an average pore size of

[0073] 4A molecular sieve: brand XFF20-102487, purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with an average pore size of

[0074] Hydrogenation catalyst: brand P111328, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0075] Example 1

[0076] (1) Figure 1 As shown, acetone and RT base were mixed in a molar ratio of 3:1 and entered the dehydration condensation unit A, first entering the dehydration condensation reactor 1 filled with 4A molecular sieve, and dehydration condensation reaction was carried out under nitrogen atmosphere (reaction temperature was 80°C, total volume space velocity of acetone and RT base was 0.3h-1 ), to obtain a first mixed solution containing Schiff base (wherein the water content is less than 1 wt %), and to feed it into a storage tank 2;

[0077] The composition of the obtained first mixed solution containing Schiff base and the related results of the dehydration condensation reaction are shown in Table 1;

[0078] (2) The first mixed liquid containing Schiff base enters the hydrogenation unit B from the storage tank 2, is mixed with hydrogen in the hydrogenation reactor 3, and undergoes a hydrogenation reaction under the action of a hydrogenation catalyst (pressure is 1.0 MPa, temperature is 90° C., hydrogen-to-oil ratio is 400:1, and volumetric space velocity of the first mixed liquid containing Schiff base is 0.25 h / min). -1 ), to obtain a second mixed solution;

[0079] The composition of the obtained second mixed solution is shown in Table 2;

[0080] (3-1) The second mixed liquid enters the separation crystallization unit C, first enters the first distillation tower 4 (tower pressure of 0.1 MPa; tower top temperature of 56° C., tower bottom temperature of 90° C.; reflux ratio of 4) for first distillation, and then enters the second distillation tower 5 (tower pressure of 0.1 MPa; tower top temperature of 112° C., tower bottom temperature of 140° C.; reflux ratio of 4.5) for second distillation, and the separated acetone and methyl isobutyl ketone are returned from the top of the first distillation tower 4 and the top of the second distillation tower 5 to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction, and a separated liquid (wherein the sum of the contents of acetone and methyl isobutyl ketone is 12.9 wt %) is obtained at the bottom of the second separation tower 5;

[0081] (3-2) The separated liquid is introduced into the first crystallizer 6 (crystallization temperature is 60° C.) for first crystallization to obtain antioxidant product 4010NA, and the remaining liquid phase is introduced into the second crystallizer 7 (crystallization temperature is 40° C.) for second crystallization to obtain antioxidant product 6PPD;

[0082] The purity of the obtained antioxidant products 4010NA and 6PPD is shown in Table 3.

[0083] Example 2

[0084] (1) Figure 1 As shown, acetone and RT base were mixed in a molar ratio of 5:1 and entered the dehydration condensation unit A, first entering the dehydration condensation reactor 1 filled with 4A molecular sieve, and dehydration condensation reaction was carried out under nitrogen atmosphere (reaction temperature was 80°C, and the total volume space velocity of acetone and RT base was 0.3h -1 ), to obtain a first mixed solution containing Schiff base (wherein the water content is less than 1 wt %), and to feed it into a storage tank 2;

[0085] The composition of the obtained first mixed solution containing Schiff base and the related results of the dehydration condensation reaction are shown in Table 1;

[0086] (2) The first mixed liquid containing Schiff base is introduced into hydrogenation unit B from storage tank 2, mixed with hydrogen in hydrogenation reactor 3, and hydrogenated under the action of hydrogenation catalyst (pressure is 1 MPa, temperature is 90°C, hydrogen-to-oil ratio is 350:1, volume space velocity of the first mixed liquid containing Schiff base is 0.30 h / min). -1 ), to obtain a second mixed solution;

[0087] The composition of the obtained second mixed solution is shown in Table 2;

[0088] (3-1) The second product enters the separation crystallization unit C, first enters the first distillation tower 4 (tower pressure of 0.1 MPa; tower top temperature of 56° C., tower bottom temperature of 90° C.; reflux ratio of 4) for first distillation, and then enters the second distillation tower 5 (tower pressure of 0.1 MPa; tower top temperature of 112° C., tower bottom temperature of 140° C.; reflux ratio of 4.5) for second distillation, and the separated acetone and methyl isobutyl ketone are respectively returned from the top of the first distillation tower 4 and the top of the second distillation tower 5 to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction, and a separated liquid (wherein the sum of the contents of acetone and methyl isobutyl ketone is 14 wt %) is obtained at the bottom of the second separation tower 5;

[0089] (3-2) The separated liquid is introduced into the first crystallizer 6 (crystallization temperature is 60° C.) for first crystallization to obtain antioxidant product 4010NA, and the remaining liquid phase is introduced into the second crystallizer 7 (crystallization temperature is 40° C.) for second crystallization to obtain antioxidant product 6PPD;

[0090] The purity of the obtained antioxidant products 4010NA and 6PPD is shown in Table 3.

[0091] Example 3

[0092] (1) Figure 1 As shown, acetone and RT base were mixed in a molar ratio of 3:1 and entered the dehydration condensation unit A, first entering the dehydration condensation reactor 1 filled with 4A molecular sieve, and dehydration condensation reaction was carried out under nitrogen atmosphere (reaction temperature was 60°C, and the total volume space velocity of acetone and RT base was 0.3h -1 ), to obtain a first mixed solution containing Schiff base (wherein the water content is less than 1 wt %), and to feed it into a storage tank 2;

[0093] The composition of the obtained first mixed solution containing Schiff base and the related results of the dehydration condensation reaction are shown in Table 1;

[0094] (2) The first mixed liquid containing Schiff base is introduced into hydrogenation unit B from storage tank 2, mixed with hydrogen in hydrogenation reactor 3, and hydrogenated under the action of hydrogenation catalyst (pressure is 1.2 MPa, temperature is 100°C, hydrogen-to-oil ratio is 400:1, volume space velocity of the first mixed liquid containing Schiff base is 0.25 h / min). -1 ), to obtain a second mixed solution;

[0095] The composition of the obtained second mixed solution is shown in Table 2;

[0096] (3-1) The second product enters the separation crystallization unit C, first enters the first distillation tower 4 (tower pressure of 0.1 MPa; tower top temperature of 56° C., tower bottom temperature of 90° C.; reflux ratio of 4) for first distillation, and then enters the second distillation tower 5 (tower pressure of 0.1 MPa; tower top temperature of 112° C., tower bottom temperature of 140° C.; reflux ratio of 4.5) for second distillation, and the separated acetone and methyl isobutyl ketone are returned from the top of the first distillation tower 4 and the top of the second distillation tower 5 to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction, and a separated liquid is obtained at the bottom of the second separation tower 5 (wherein the sum of the contents of acetone and methyl isobutyl ketone is 7 wt %);

[0097] (3-2) The separated liquid is introduced into the first crystallizer 6 (crystallization temperature is 60° C.) for first crystallization to obtain antioxidant product 4010NA, and the remaining liquid phase is introduced into the second crystallizer 7 (crystallization temperature is 40° C.) for second crystallization to obtain antioxidant product 6PPD;

[0098] The purity of the obtained antioxidant products 4010NA and 6PPD is shown in Table 3.

[0099] Example 4

[0100] (1) Figure 1 As shown, acetone and RT base are mixed in a molar ratio of 3:1 and enter the dehydration condensation unit A, first entering the dehydration condensation reactor 1 filled with 3A molecular sieve catalyst, and the dehydration condensation reaction is carried out under nitrogen atmosphere (the reaction temperature is 80°C, and the total volume space velocity of acetone and RT base is 0.3h -1 ), to a first mixed solution containing Schiff base (wherein the water content is less than 2 wt %), and sent to a storage tank 2;

[0101] The composition of the obtained first mixed solution containing Schiff base and the related results of the dehydration condensation reaction are shown in Table 1;

[0102] (2) The first mixed liquid containing Schiff base is introduced into hydrogenation unit B from storage tank 2, mixed with hydrogen in hydrogenation reactor 3, and hydrogenated under the action of hydrogenation catalyst (pressure is 1.0 MPa, temperature is 80°C, hydrogen-to-oil ratio is 400:1, volume space velocity of the first mixed liquid containing Schiff base is 0.25 h / min). -1 ), to obtain a second mixed solution;

[0103] The composition of the obtained second mixed solution is shown in Table 2;

[0104] (3-1) The second mixed liquid enters the separation crystallization unit C, first enters the first distillation tower 4 (tower pressure 0.1 MPa; tower top temperature 56° C., tower bottom temperature 90° C.; reflux ratio 4) for first distillation, and then enters the second distillation tower 5 (tower pressure 0.1 MPa; tower top temperature 112° C., tower bottom temperature 140° C.; reflux ratio 4.5) for second distillation, and the separated acetone and methyl isobutyl ketone are returned from the top of the first distillation tower 4 and the top of the second distillation tower 5 to the dehydration condensation reactor 1 to continue to participate in the dehydration condensation reaction, and a separated liquid (wherein the sum of the contents of acetone and methyl isobutyl ketone is 5 wt%) is obtained at the bottom of the second separation tower 5;

[0105] (3-2) The separated liquid is introduced into the first crystallizer 6 (crystallization temperature is 60° C.) for first crystallization to obtain antioxidant product 4010NA, and the remaining liquid phase is introduced into the second crystallizer 7 (crystallization temperature is 40° C.) for second crystallization to obtain antioxidant product 6PPD;

[0106] The purity of the obtained antioxidant products 4010NA and 6PPD is shown in Table 3.

[0107] Comparative Example 1

[0108] The method of Example 1 is followed, except that in step (3-2), the separated liquid is introduced into a distillation tower, and atmospheric distillation separation is performed using the boiling point difference between 4010NA and 6PPD (tower pressure 0.1 MPa; tower top temperature 180°C, tower bottom temperature 200°C; reflux ratio 4). The other steps and conditions are the same as those of Example 1, and antioxidant products 4010NA and 6PPD are obtained.

[0109] Among them, the product composition and reaction results of each step are shown in Table 1-3.

[0110] Comparative Example 2

[0111] Acetone and RT base are mixed in a molar ratio of 3:1, a Pt / C catalyst (the weight of Pt accounts for 0.25% of the total weight of the catalyst) is loaded into a fixed bed reaction device, and the mixed solution of acetone and RT base is added to carry out condensation hydrogenation reaction (reaction temperature is 100° C., pressure is 1.0 MPa, hydrogen-to-oil ratio is 400:1) to obtain a reaction solution;

[0112] After gas-liquid separation, the reaction liquid is respectively recovered by a recovery tower to recover acetone and methyl isobutyl ketone, and finally enters a distillation tower for distillation separation (tower pressure 0.1MPa; tower top temperature 180°C, tower bottom temperature 200°C; reflux ratio 4) to obtain an antioxidant product. In the obtained antioxidant product, the weight ratio of 4010NA to 6PPD is 4:1; wherein the purity of the antioxidant product 4010NA is 90.2% by weight, and the purity of the antioxidant product 6PPD is 97.1% by weight.

[0113] Table 1

[0114]

[0115] Note: The content percentage of each component in Table 1 is weight percentage

[0116] Table 2

[0117]

[0118] Note: The high boiling products in Table 2 are the products obtained by condensation and hydrogenation of the self-condensation product of methyl isobutyl ketone and RT base.

[0119] Table 3

[0120]

[0121] It can be seen from the results of the above Examples 1-4 and Comparative Examples 1-2 that by adopting the method for preparing p-phenylenediamine antioxidants of the present invention, by adjusting the ratio of acetone and RT base, after two-step reactions of condensation and hydrogenation, two high-purity antioxidant products can be obtained, and the products 4010NA and 6PPD can be controllably obtained within a certain ratio range (for example, the weight ratio of 4010NA to 6PPD in Examples 1-4 is in the range of (1.6-3): 1). Compared with the one-step process (for example, Comparative Example 2), a higher proportion of 6PPD in the product can be achieved.

[0122] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a p-phenylenediamine antioxidant, characterized in that: include: (1) in the presence of molecular sieves, subjecting acetone to a dehydration condensation reaction with RT base to obtain a first mixed solution containing a Schiff base; (2) subjecting the first mixed solution containing the Schiff base to a hydrogenation reaction in the presence of a hydrogenation catalyst to obtain a second mixed solution; (3) The second mixed solution is separated and crystallized to obtain antioxidant 4010NA and antioxidant 6PPD.

2. The method according to claim 1, wherein: In step (1), the average pore size of the molecular sieve is Preferably, the molecular sieve is 3A molecular sieve and / or 4A molecular sieve, and more preferably is 4A molecular sieve.

3. The method according to claim 1 or 2, wherein: In step (1), the conditions of the dehydration condensation reaction include: a temperature of 60-80°C, a total volume space velocity of acetone and RT base of 0.1-0.5h -1 ; Preferably, the molar ratio of acetone:RT base is (3-5):1; Preferably, the water content in the first mixed solution containing the Schiff base is less than 2 wt %.

4. The method according to any one of claims 1 to 3, wherein: In step (2), the conditions of the hydrogenation reaction include: a pressure of 0.4-1.5 MPa, preferably 0.8-1.2 MPa; a temperature of 80-150°C, preferably 90-120°C; a hydrogen-to-oil ratio of (100-700):1, preferably (100-300):1; a volume space velocity of the first mixed solution containing the Schiff base of 0.1-0.5 h -1 , preferably 0.2-0.35h -1 .

5. The method according to any one of claims 1 to 4, wherein: In step (3), the separation crystallization comprises: (3-1) separating the second mixed liquid to obtain acetone, methyl isobutyl ketone and a separated liquid; wherein the acetone and methyl isobutyl ketone are returned to step (1) to participate in the dehydration condensation reaction; (3-2) The separated liquid is subjected to crystallization treatment to obtain antioxidant 4010NA and antioxidant 6PPD.

6. The method according to claim 5, wherein: The separation process includes a first distillation and a second distillation performed sequentially; Preferably, the conditions of the first distillation include: tower pressure of 0.1-0.3 MPa; tower top temperature of 50-60°C, tower bottom temperature of 90-100°C; reflux ratio of 4-5; Preferably, the conditions of the second distillation include: tower pressure of 0.1-0.3 MPa; tower top temperature of 110-120°C, tower bottom temperature of 140-150°C; reflux ratio of 4-5; Preferably, the sum of the contents of acetone and methyl isobutyl ketone in the separated liquid is less than 15 wt %.

7. The method according to claim 5 or 6, wherein: The crystallization process includes a first crystallization and a second crystallization performed sequentially; Preferably, the temperature of the first crystallization is 50-60°C; Preferably, the temperature of the second crystallization is 30-40°C.

8. A system for preparing a p-phenylenediamine antioxidant, characterized in that: The system comprises a dehydration condensation unit (A), a hydrogenation unit (B) and a separation crystallization unit (C) which are connected in sequence; The dehydration condensation unit (A) is used to carry out a dehydration condensation reaction of acetone and RT base to obtain a first mixed solution containing Schiff base; The hydrogenation unit (B) is used to hydrogenate the first mixed solution containing the Schiff base to obtain a second mixed solution; The separation and crystallization unit (C) is used to separate and crystallize the second mixed solution to obtain antioxidant 4010NA and antioxidant 6PPD.

9. The system according to claim 8, wherein: The dehydration condensation unit (A) comprises a dehydration condensation reactor (1) and a storage tank (2) which are connected in sequence; The hydrogenation unit (B) comprises a hydrogenation reactor (3), and the hydrogenation reactor (3) is connected to the storage tank (2); The separation crystallization unit (C) comprises a first separation tower (4), a second separation tower (5), a first crystallizer (6) and a second crystallizer (7) which are connected in sequence; wherein the first separation tower (4) is connected to the hydrogenation reactor (3).

10. The system according to claim 9, wherein: The first separation tower (4) and the second separation tower (5) are respectively connected to the dehydration condensation reactor (1).

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