A system for co-producing N-methylaniline and N,N-dimethylaniline

Abstract

The invention provides a system for co-producing N-methylaniline and N,N-dimethylaniline, comprising a reactor; the reactor comprises a first reaction zone and a second reaction zone which are sequentially connected along the axial direction; the first reaction zone is filled with a first catalyst; the second reaction zone is filled with a second catalyst; after aniline and methanol enter the first reaction zone, they are catalytically converted into N,N-dimethylaniline; when the remaining unreacted aniline and methanol flow through the second reaction zone, they are catalytically converted into N-methylaniline; in the system provided by the invention, aniline and methanol react in different reaction zones of the same reactor, the first reaction zone has a higher pressure and temperature than the second reaction zone, which helps aniline and methanol to be converted into N,N-dimethylaniline in the first reaction zone and into N-methylaniline in the second reaction zone, the aniline is almost completely converted, the utilization rate of the raw materials is greatly increased, the proportions of N-methylaniline and N,N-dimethylaniline in the product are equal, and the product is diversified.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical preparation, in particular to a system for co-producing N-methylaniline and N,N-dimethylaniline. Background Art

[0002] N-methylaniline and N,N-dimethylaniline are two important organic compounds that are widely used in medicine, dyes, pesticides and other fields. At present, the methods for producing N-methylaniline mainly include high-pressure reactor catalytic method, separation and extraction method from tar, nitrobenzene and methanol one-pot method and aniline and methanol production method. Among them, the high-pressure reactor catalytic method mostly uses toluene (hazardous chemicals) as raw material, and the synthesis method is complicated, the yield is poor, and the industrialization prospect is not good; the method of producing N-methylaniline using aniline and methanol as raw materials is mostly prepared by gas phase method, specifically, aniline and methanol are chemically reacted under the catalytic action of a catalyst (C 6 H 5 -NH 2 +CH 3 OH→C 6 H 5 -NHCH 3 +H 2 O), among the products obtained, the catalyst has poor selectivity for N-methylaniline, resulting in a large amount of N,N-dimethylaniline (DMA) as a by-product. The catalyst for synthesizing N,N-dimethylaniline is different from the catalyst for synthesizing N-methylaniline. The existing catalysts for synthesizing N,N-dimethylaniline are mainly metal solid acids, such as SO 4 2- / ZrO 2 SnO 2 -γ-Al 2 O 3 / Hβ(m) and other metal solid acid catalysts. For the process of synthesizing N, N-dimethylaniline, the aniline methanol method can also be used as a common method for synthesizing N, N-dimethylaniline (C 6 H 5 -NHCH 3 +2CH 3 OH→C 6 H 5 -N(CH 3 ) 2 +2H 2 O), and the by-product is N-methylaniline.

[0003] However, there is no process for co-producing N-methylaniline and N,N-dimethylaniline, which is not conducive to actual production capacity adjustment. And because the boiling points of N,N-dimethylaniline and N-methylaniline are close, sophisticated separation equipment is required, which leads to high synthesis costs of N,N-dimethylaniline and N-methylaniline. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides a system for co-producing N-methylaniline and N,N-dimethylaniline, so as to simultaneously achieve high-level output of N,N-dimethylaniline and N-methylaniline. The specific content of the invention is as follows:

[0005] The present invention provides a system for co-producing N-methylaniline and N,N-dimethylaniline, comprising a reactor; the reactor comprises a first reaction zone and a second reaction zone which are sequentially connected along the axial direction; the first reaction zone is filled with a first catalyst; the second reaction zone is filled with a second catalyst;

[0006] Aniline and methanol in a molar ratio of 1:1 to 1:8 are used as the reaction raw materials. After entering the first reaction zone, they are catalytically converted into N,N-dimethylaniline under the conditions of 280-340°C and 1.5-2 MPa. When the first mixed flow including the product accumulated in the first reaction zone flows through the second reaction zone, the remaining unreacted aniline and methanol therein are catalytically converted into N-methylaniline under the conditions of 220-250°C and 0-0.5 MPa, thereby obtaining a second mixed flow containing 40-50% N,N-dimethylaniline and 50-60% N-methylaniline.

[0007] Optionally, the first reaction zone is in the shape of a straight cylinder with a constant radial dimension, and the second reaction zone is in the shape of a truncated cone with a radial dimension that gradually increases in a direction away from the first reaction zone.

[0008] Optionally, the first reaction zone and the second reaction zone are respectively provided with independent temperature control components and pressure control components.

[0009] Optionally, a throttling component is provided at the connection portion between the first reaction zone and the second reaction zone, and the throttling component is used to control the flow rate of the first mixed flow entering the second reaction zone.

[0010] Optionally, the first catalyst is formed by CuO and a promoter metal loaded on a carrier; wherein,

[0011] The carrier includes copper aluminum spinel, silicon dioxide, aluminum oxide or zeolite molecular sieve, accounting for 60-70% by mass;

[0012] The auxiliary metal is selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, with a mass ratio of 5-15%;

[0013] The mass proportion of the CuO is 10-30%.

[0014] Optionally, the second catalyst is formed by CuO and a promoter metal loaded on a carrier; wherein,

[0015] The carrier includes copper aluminum spinel, silicon dioxide, aluminum oxide or zeolite molecular sieve, with a mass ratio of 45-65%;

[0016] The auxiliary metal is selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, with a mass ratio of 10-20%;

[0017] The mass proportion of the CuO is 30-45%.

[0018] Optionally, the system further comprises a gas-liquid separation subsystem, a gas phase separation subsystem and a liquid phase separation subsystem; wherein,

[0019] The gas-liquid separation subsystem is in communication with the second reaction zone and is used for performing gas-liquid separation on the second mixed flow to obtain a first gas phase component and a first liquid phase component containing N-methylaniline and N,N-dimethylaniline;

[0020] The gas phase separation subsystem is in communication with the gas-liquid separation subsystem and is used to receive the first gas phase component and separate high-purity hydrogen therefrom;

[0021] The liquid phase separation subsystem is in communication with the gas-liquid separation subsystem and is used for receiving the first liquid phase component and separating N-methylaniline and N,N-dimethylaniline therefrom.

[0022] Optionally, the gas phase separation subsystem includes a compressor, a condenser, a gas-liquid separator and an absorption tower; the compressor is connected to the condenser, and the condenser is connected to the gas-liquid separator, and the first gas phase component is compressed by the compressor, enters the condenser for condensation treatment, and then enters the gas-liquid separator for gas-liquid separation to obtain a second gas phase component and a second liquid phase component;

[0023] The gas-liquid separator is connected to the absorption tower, and the second gas phase component continues to be introduced into the absorption tower containing alkaline water to absorb carbon dioxide, and the remainder is high-purity hydrogen.

[0024] Optionally, the liquid phase separation subsystem comprises a raw material recovery tower, a molecular sieve adsorption assembly, a liquid membrane molecular sieve assembly and a product separation tower, the raw material recovery tower is connected to the molecular sieve adsorption assembly, and the raw material recovery tower, the liquid membrane molecular sieve assembly and the product separation tower are connected in sequence;

[0025] The first liquid phase component enters the raw material recovery tower, and the methanol and water gathered at the top of the tower are filtered through the molecular sieve adsorption component to separate the methanol for reuse as raw material; the product-rich liquid gathered at the bottom of the tower is filtered through the liquid membrane molecular sieve component to separate N-methylaniline and N,N-dimethylaniline from the heavy components; the N-methylaniline and N,N-dimethylaniline are separated in the product separation tower, and N,N-dimethylaniline is extracted from the top of the tower and N-methylaniline is extracted from the bottom of the tower.

[0026] Optionally, a mixer is further provided between the liquid phase separation subsystem and the gas-liquid separation subsystem, and the mixer is used to receive the second liquid phase component and the first liquid phase component and send them into the liquid phase separation subsystem.

[0027] Optionally, a heat exchange subsystem is further provided between the gas-liquid separation subsystem and the reactor. After the reaction raw materials and the second mixed flow undergo heat exchange through the heat exchange subsystem, the reaction raw materials enter the reactor, and the second mixed flow enters the gas-liquid separation subsystem.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The present invention provides a system for co-producing N-methylaniline and N,N-dimethylaniline, comprising a reactor; the reactor comprises a first reaction zone and a second reaction zone which are sequentially connected along the axial direction; wherein a reaction raw material inlet is located in the first reaction zone, and a first catalyst is filled in the first reaction zone; a reaction product outlet is located in the second reaction zone, and a second catalyst is filled in the second reaction zone; aniline and methanol with a molar ratio of 1:1 to 1:8 are used as reaction raw materials, and after entering the first reaction zone, they are catalytically converted into N,N-dimethylaniline under the conditions of 280 to 340° C. and 1.5 to 2 MPa; when a first mixed flow including products gathered in the first reaction zone flows through the second reaction zone, the remaining unreacted aniline and methanol therein are catalytically converted into N-methylaniline under the conditions of 220 to 250° C. and 0 to 0.5 MPa, so as to obtain a second mixed flow containing 40 to 50% N,N-dimethylaniline and 50 to 60% N-methylaniline.

[0030] In the system for co-producing N-methylaniline and N,N-dimethylaniline provided by the present invention, aniline and methanol undergo different reactions in different reaction zones of the same reactor, and the first reaction zone has a higher pressure and temperature than the second reaction zone, which helps aniline and methanol to be more converted into N,N-dimethylaniline in the first reaction zone and more converted into N-methylaniline in the second reaction zone. The conversion rate of aniline is almost 100%, the utilization rate of raw materials is greatly increased, the proportions of N-methylaniline and N,N-dimethylaniline in the product are equal, the products are diversified, and the high value of the products can offset part of the separation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 The schematic diagram of the structure of the reactor provided by the embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram of a system for co-producing N-methylaniline and N,N-dimethylaniline provided in an embodiment of the present invention is shown;

[0034] Figure 3 A schematic diagram of another system for co-producing N-methylaniline and N,N-dimethylaniline provided in an embodiment of the present invention is shown;

[0035] Figure 4 The following is a process system diagram for the co-production of N-methylaniline and N,N-dimethylaniline provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0037] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0038] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0039] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0040] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] In the process of synthesizing N,N-dimethylaniline from aniline and methanol as raw materials, N-methylaniline is inevitably produced as a by-product; at the same time, in the process of synthesizing N-methylaniline from aniline and methanol as raw materials, N,N-dimethylaniline is inevitably produced as a by-product; and N,N-dimethylaniline and N-methylaniline have similar boiling points, so refined separation equipment is required, resulting in a high production cost of N,N-dimethylaniline or N-methylaniline.

[0042] Based on this, the present invention proposes that, in the synthesis process of N, N-dimethylaniline or N-methylaniline, when the by-product separation process is indispensable, N, N-dimethylaniline and N-methylaniline are co-produced to obtain N, N-dimethylaniline and N-methylaniline with equivalent contents, so as to increase the diversity of products and improve the conversion rate of raw materials; at the same time, in the product, the contents of N, N-dimethylaniline and N-methylaniline are equivalent, which avoids the problem of excessive difference in load between the top and bottom of the tower caused by uneven proportion of target products in the separation process, makes the separation operation process more stable, and reduces the potential risks that may be caused by load imbalance. This has huge economic value in actual production. The specific implementation content is as follows:

[0043] The present invention provides a system for co-producing N-methylaniline and N,N-dimethylaniline, comprising a reactor 1; Figure 1The schematic diagram of the structure of the reactor provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the reactor 1 comprises a first reaction zone 101 and a second reaction zone 102 which are sequentially connected along the axial direction; the first reaction zone 101 is filled with a first catalyst; the second reaction zone 102 is filled with a second catalyst;

[0044] See also Figure 1 The reactor 1 provides a reaction site and reaction environment for the co-production of N-methylaniline and N,N-dimethylaniline. The first reaction zone 101 and the second reaction zone 102 in the reactor 1 can realize independent temperature and pressure control. Before the reaction, the temperature and pressure of the first reaction zone 101 and the second reaction zone 102 are regulated to control the temperature of the first reaction zone 101 to 280-340 °C and the pressure to 1.5-2 MPa; the temperature of the second reaction zone 102 is controlled to 220-250 °C and the pressure to 0-0.5 MPa; the inlet of the reaction raw materials is located in the first reaction zone 101. Aniline and methanol, as reaction raw materials, enter the first reaction zone 101 and are heated at 280-340 °C and 1.5-2 MPa, with the help of the catalytic action of the first catalyst, it is converted into N,N-dimethylaniline; when the first mixed flow including the product (N,N-dimethylaniline) accumulated in the first reaction zone flows through the second reaction zone 102, the remaining unreacted aniline and methanol continue to be converted into N-methylaniline with the help of the catalytic action of the second catalyst under the conditions of 220~250℃ and 0~0.5MPa.

[0045] The molar ratio of aniline and methanol involved in the reaction is 1:1~1:8, preferably 1:3~1:5, and excess methanol can ensure the complete conversion of aniline. In addition, the unreacted methanol can be recovered through process design in the subsequent process. In the initial stage of the reaction, the concentration of methanol in the first reaction zone 101 is relatively high, that is, it is in a methanol-rich state. Under high temperature and high pressure conditions (280~340 ℃, 1.5~2MPa), the reaction preferentially generates N,N-dimethylaniline. In this process, a large amount of unreacted aniline and methanol will remain. These unreacted materials then enter the second reaction zone 102, which is conducive to the generation of N-methylaniline under a temperature and pressure lower than that of the first reaction zone 101 (220~250℃, 0~0.5MPa), and can make more full use of these remaining materials. If the order is changed, the reaction is carried out under normal pressure first, and then the pressure is increased, the utilization rate of methanol and aniline will decrease. That is to say, the present invention carries out the co-production of N,N-dimethylaniline and N-methylaniline according to the strategy of high pressure first and then normal pressure, which can ensure that the two raw materials of methanol and aniline are more efficiently utilized in the whole reaction process. In addition, the conversion from high pressure to low pressure is relatively easy to achieve, and the smooth conversion of this process can be assisted by air intake expansion and adding throttling elements. At the same time, the reaction temperature is easy to control, and the reaction temperature can be kept at a more suitable level. Such an arrangement not only optimizes the reaction conditions, but also improves the utilization rate of the raw materials.

[0046] It should be noted that the first mixed flow includes N,N-dimethylaniline generated in the first reaction zone after the catalytic conversion reaction, and the remaining aniline and methanol that have entered the first reaction zone and have not yet participated in the reaction; in the second reaction zone, the remaining unreacted aniline and methanol continue to be converted into N-methylaniline with the help of the catalytic action of the second catalyst, and the resulting mixed fluid containing two target products and a small amount of reaction raw materials, water, and carbon dioxide is hereinafter referred to as the second mixed flow.

[0047] The reaction system provided by the invention uses the double-chamber (first reaction zone 101 and second reaction zone 102) reaction environment provided by the reactor 1 to realize the conversion of the same reaction raw material into two products, respectively provide the conditions required for each, realize the simultaneous progress of the two reactions, and finally obtain two target products with equivalent contents. The content of the finally obtained N,N-dimethylaniline is 40-50%, and the content of N-methylaniline is 50-60%.

[0048] Continue to see Figure 1The interior of the reactor 1 provided in the embodiment of the present invention is a variable diameter structure, the first reaction zone 101 is a straight cylinder with a constant radial dimension, and the second reaction zone 102 is a truncated cone with a radial dimension that gradually increases in the direction away from the first reaction zone 101. A separation disk is provided at the connection between the first reaction zone 101 and the second reaction zone 102, which is divided into two independent but connected spaces, and a throttling component is also installed to control the flow rate of the first mixed flow entering the second reaction zone, so that the first reaction zone 101 maintains a relatively high pressure, which helps to improve the yield of N, N-dimethylaniline; through the throttling component and the expansion design of the second reaction zone 102, the pressure in the lower reaction zone is reduced, which is beneficial to the production of N-methylaniline.

[0049] It should be noted that, in the reactor 1 provided by the present invention, the first reaction zone 101 and the second reaction zone 102 may be provided with independent temperature control components and pressure control components respectively.

[0050] The design of the dual-chamber reactor 1 is simple in structure, compact, and has good sealing performance. It is easy to operate, can realize segmented temperature control, and has better synthesis continuity. The reaction temperature can be kept at a relatively suitable level. In the present invention, the temperature of the second reaction zone 102 is lower than that of the first reaction zone 101, which is conducive to the reaction in the direction of easily producing N-methylaniline. Similarly, the generated N-methylaniline can also continue to react with methanol to generate N, N-dimethylaniline, but the temperature required for this process is about 300°C. Therefore, when the temperature of the second reaction zone is maintained at 220~250°C, N-methylaniline is mainly generated, and N, N-dimethylaniline is basically not generated. Further, this process can consume aniline almost completely by using excess methanol, thereby reducing the demand for a separation tower.

[0051] It should be noted that the first catalyst loaded in the first reaction zone 101 in the embodiment of the present invention is a catalyst with high selectivity for N,N-dimethylaniline, specifically formed by CuO and auxiliary metal loaded on a carrier; wherein the carrier can be selected from copper aluminum spinel, silica, alumina or zeolite molecular sieve, with a mass proportion of 60~70%; the auxiliary metal can be selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, with a mass proportion of 5~10% (5-15%); the mass proportion of CuO is 10~30%.

[0052] As an example, the first catalyst of the present invention is formed by CuO and metal additives Mg and Ce loaded on a copper aluminum spinel carrier, wherein the mass proportion of CuO is 23%, the mass proportion of the metal additives Mg and Ce is 7%, and the mass proportion of the copper aluminum spinel carrier is 70%; as another example, the first catalyst of the present invention is formed by CuO and the metal additive Zr loaded on a silica carrier, wherein the mass proportion of CuO is 15%, the mass proportion of the metal additive Zr is 15%, and the mass proportion of the silica carrier is 70%.

[0053] It should be noted that the second catalyst loaded in the second reaction zone 102 of the embodiment of the present invention is a catalyst with high selectivity for N-methylaniline, specifically formed by CuO and auxiliary metal loaded on a carrier; wherein the carrier includes copper aluminum spinel, silica, alumina or zeolite molecular sieve, accounting for 45~65% by mass; the auxiliary metal is selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, accounting for 10~20% by mass; the mass proportion of CuO is 30~45%.

[0054] As an example, the second catalyst can be formed by CuO and metal additives Mg and La loaded on a copper aluminum spinel carrier, wherein the mass proportion of CuO is 40%, the mass proportion of the metal additives Mg and La is 10%, and the mass proportion of the copper aluminum spinel carrier is 50%; as another example, the Cu-based catalyst used in the second stage reaction of the present invention is formed by CuO and metal additives Y and Ce loaded on a copper aluminum spinel carrier, wherein the mass proportion of CuO is 30%, the mass proportion of the metal additives Y and Ce is 10%, and the mass proportion of the copper aluminum spinel carrier is 60%. As another example, the second catalyst can also be formed by CuO and metal additives Mg and Co loaded on a copper aluminum spinel carrier, wherein the mass proportion of CuO is 40%, the mass proportion of the metal additives Mg and Co is 15%, and the mass proportion of the copper aluminum spinel carrier is 45%; as another example, the second catalyst can also be formed by CuO and metal additives Zr and Co loaded on a silica carrier, wherein the mass proportion of CuO is 30%, the mass proportion of the metal additives Zr and Co is 20%, and the mass proportion of the silica carrier is 50%.

[0055] It should be noted that the catalyst needs to be reduced before use. 2 N 2 Reduction was carried out under H 2 / N 2 The volume content of hydrogen in the mixed gas is 1%~20%, and the space velocity is 100 h -1 ~1000 h -1, the reduction temperature is 200 ℃ ~ 300 ℃, and the reduction time is 1 h ~ 50 h; for example, when the catalyst needs to be reduced, hydrogen and nitrogen (5% H 2 -95%N 2 ) mixed gas, the temperature of the double-chamber reactor 1 is set to rise to 200 °C for 5 h, maintain for 1 h, continue to rise to 240 °C for 2 h, and maintain for 2 h to complete the catalyst reduction; for example, when the catalyst needs to be reduced, hydrogen and nitrogen (20% H 2 -80% N 2 ) mixed gas, the temperature of the double-chamber reactor 1 was set to rise to 200 °C in 5 h, maintained for 1 h, and then continued to rise to 300 °C in 5 h, maintained for 1 h, to complete the catalyst reduction.

[0056] The present invention adopts a dual-chamber reactor design and cooperates with the selection of the first catalyst and the second catalyst to make methanol and aniline react in stages in the first reaction zone and the second reaction zone, and produces two target products (N, N-dimethyl and N-methylaniline) with equal proportions at one time; the content of the N, N-dimethylaniline finally obtained is 40-50%, and the content of the N-methylaniline is 50-60%; the problem of excessive difference in load between the top and bottom of the tower due to uneven proportion of the target products in the traditional process is effectively solved. This makes the operation process more stable and reduces the potential risks that may be caused by load imbalance. The conversion rate and selectivity of the reaction are improved, the selectivity and purity of the product are improved, the subsequent separation steps become simpler and more efficient, and the energy consumption is also reduced.

[0057] For further information, see Figure 2 The system for co-producing N-methylaniline and N,N-dimethylaniline provided by the present invention further comprises a gas-liquid separation subsystem 2, a gas phase separation subsystem 3 and a liquid phase separation subsystem 4; Figure 2 As shown, the gas-liquid separation subsystem 2 includes at least one first gas-liquid separator, which is connected to the second reaction zone 102 of the reactor 1, and is used to perform gas-liquid separation on the second mixed flow to separate a first gas phase component and a first liquid phase component containing N-methylaniline and N,N-dimethylaniline; the gas phase separation subsystem 3 includes at least one second gas-liquid separator, which is connected to the gas-liquid separation subsystem 2, and is used to receive the first gas phase component and separate high-purity hydrogen therefrom; the liquid phase separation subsystem 4 is connected to the gas-liquid separation subsystem 2, and is used to receive the first liquid phase component and separate N-methylaniline and N,N-dimethylaniline therefrom.

[0058] The second mixed flow contains target products (N,N-dimethylaniline and N-methylaniline), methanol, water, carbon dioxide and hydrogen; in order to increase the yield of the product as much as possible and maximize the utilization of the materials involved in the reaction; the present invention is aimed at the recovery and utilization of hydrogen and methanol, and the separation and purification of the products. In the system provided, the gas-liquid separation subsystem 2 performs gas-liquid separation on the second mixed flow, and the separated first gas phase component contains hydrogen, methanol and carbon dioxide; in order to collect high-purity hydrogen from the first gas phase component, the gas phase separation subsystem 3 provided in the embodiment of the present invention is composed of a compressor, a condenser, a gas-liquid separator and an absorption tower; the compressor is connected to the condenser, the condenser is connected to the gas-liquid separator, the gas-liquid separator is connected to the absorption tower, and the first gas phase component is respectively subjected to the action of the compressor, the condenser, the gas-liquid separator and the absorption tower, and finally obtains high-purity hydrogen. Specifically: the first gas phase component is first introduced into the compressor, and after being compressed by the compressor, it enters the condenser along the connecting pipe between the compressor and the condenser for condensation treatment, so that the methanol and a small amount of water vapor therein are liquefied, and the materials obtained by condensation are further all input into the gas-liquid separator connected to the condenser for gas-liquid separation treatment, and methanol and water are separated as the second liquid phase component, and then discharged from the gas-liquid separator; the remaining gas in the gas-liquid separator is the second gas phase component (the main components are hydrogen and carbon dioxide); the second gas phase component is further sent to the absorption tower containing alkaline water connected to the gas-liquid separator, and the alkaline water absorbs the carbon dioxide in the second gas phase component, and the remainder is high-purity hydrogen.

[0059] Through the purification treatment of the gas phase separation subsystem 3, the purity of the obtained hydrogen is 99.9~99.99%, and by changing the process conditions, the absorption tower containing alkaline water can be adjusted within a certain range so that the pressure of the obtained hydrogen has a certain adjustable range. The hydrogen boost ratio in the available hydrogen scenario is greatly reduced, so that the investment in the back-end boosting equipment and the land occupation are highly competitive.

[0060] The gas-liquid separation subsystem 2 performs gas-liquid separation on the second mixed flow, and the separated first liquid phase component contains the target product (N,N-dimethylaniline and N-methylaniline), water, methanol and other heavy components; in order to separate the target product from the first liquid phase component, the liquid phase separation subsystem 4 provided in the embodiment of the present invention includes a raw material recovery tower, a molecular sieve adsorption component, a liquid membrane molecular sieve component and a product separation tower; wherein the raw material recovery tower is connected to the molecular sieve adsorption component, and after the first liquid phase component enters the liquid phase separation subsystem 4, it first enters the raw material recovery tower to separate and recover methanol, and methanol and water vapor are gathered at the top of the recovery tower, and the bottom of the tower is a product-rich liquid; the methanol and water gathered at the top of the recovery tower are further introduced into the molecular sieve adsorption component connected to the raw material recovery tower for filtration, and the saturated methanol gas passes through the molecular sieve. Due to the difference in size and molecular polarity, water molecules cannot pass through the molecular sieve, while methanol molecules can pass through, thereby achieving the purpose of separating methanol from water. Methanol is separated and reused as raw material;

[0061] Furthermore, the raw material recovery tower is connected with the liquid membrane molecular sieve assembly and the product separation tower in sequence, and the product-rich liquid gathered in the bottom of the raw material recovery tower is introduced into the liquid membrane molecular sieve assembly connected thereto for filtration, so that the target product (N-methylaniline and N,N-dimethylaniline) is separated from the heavy component; the N-methylaniline and N,N-dimethylaniline separated by the liquid membrane molecular sieve assembly are further introduced into the product separation tower for product separation, and N,N-dimethylaniline is produced from the top of the tower and N-methylaniline is produced from the bottom of the tower.

[0062] It should be noted that the liquid membrane molecular sieve assembly used in the embodiment of the present invention is a tubular membrane separation technology, which can separate the target product (N-methylaniline and N, N-dimethylaniline) from the recombinant, and the operation process can be roughly divided into: pretreatment, feeding, pressurization, separation, and cleaning. Before the product-rich liquid flows into the membrane system, it is usually necessary to perform pretreatment to remove large particulate matter, suspended matter or other impurities that may block the membrane pores by precipitation; the pretreated raw liquid is pumped into the tubular membrane assembly. The tubular membrane assembly consists of a plurality of parallel membrane tubes, each of which has a support structure inside to maintain the shape of the membrane and provide sufficient mechanical strength; in order to make the target product in the product-rich liquid pass through the membrane, a certain pressure needs to be applied. Under the action of pressure, the light component will pass through the membrane to form a permeate, while the heavy component will be retained on the raw material side to form a concentrate; as the operation proceeds, contaminants may accumulate on the membrane surface, resulting in a decrease in membrane flux. Therefore, it is necessary to regularly physically or chemically clean the membrane to restore the performance of the membrane.

[0063] See also Figure 3A mixer 5 may be provided between the liquid phase separation subsystem 4 and the gas-liquid separation subsystem 2. The mixer 5 is used to receive the second liquid phase component and the first liquid phase component and send them to the liquid phase separation subsystem. In this way, the second liquid phase component (methanol and water) separated by the gas-liquid separator can be combined with the first liquid phase component and used together for subsequent methanol recovery.

[0064] See also Figure 3 A heat exchange subsystem 6 can also be arranged between the gas-liquid separation subsystem 2 and the reactor 1. The function of the heat exchange subsystem 6 is to make full use of the heat of the second mixed flow flowing out of the reactor 1 to heat the reaction raw materials, thereby avoiding the additional use of heat for preheating the raw materials and maximizing the energy utilization of the overall production process; specifically, the heat exchange subsystem 6 can be composed of a first heat exchanger, and the first heat exchanger is connected to the second reaction zone 102 of the reactor 1. Before the reaction raw materials enter the first reaction zone 101 of the reactor, they are first passed into the first heat exchanger to exchange heat with the second mixed flow. After the reaction raw materials are heated up, they enter the reactor 1. After the second mixed flow is cooled down, they enter the gas-liquid separation subsystem 2, which greatly improves the utilization of thermal energy.

[0065] Furthermore, the heat exchange subsystem 6 can also be composed of a first heat exchanger and a second heat exchanger connected in series. The second heat exchanger is connected to the gas-liquid separation subsystem 2. After the second mixed flow passes through the first heat exchanger and exchanges heat with the reaction raw materials, the heat is still relatively high. It can also be further used as a heat source to perform a second heat exchange with residential water to further cool the second mixed flow. The second mixed flow after heat exchange is input into the gas-liquid separation subsystem 2 for gas-liquid separation. The temperature of the heated residential water can reach 40~80℃.

[0066] Compared with the traditional method, the system for co-producing N-methylaniline and N, N-dimethylaniline provided by the present invention can significantly reduce energy consumption and environmental burden while improving separation efficiency by utilizing membrane separation and adsorption technology, providing a more economical and sustainable solution for industrial production. At the same time, the system for co-producing N-methylaniline and N, N-dimethylaniline provided by the present invention can also achieve high-value recovery of hydrogen, and the recovered hydrogen has a certain pressure, which can meet a variety of back-end usage scenarios, and greatly reduces the application end compressor boost ratio compared with the traditional dehydrogenation process, effectively reducing the compressor equipment investment and land occupation.

[0067] In order to enable those skilled in the art to more clearly understand the present invention, the system for co-producing N-methylaniline and N,N-dimethylaniline according to the present invention is now described in detail through the following examples.

[0068] Example 1

[0069] Figure 4The process system for co-producing N-methylaniline and N,N-dimethylaniline provided in an embodiment of the present invention is shown, including: a mixer V101, a first booster pump P101, a first heat exchanger E101, a heater E102, a reactor R101, a second heat exchanger E103, a first gas-liquid separator V102, a compressor C101, a condenser E104, a second gas-liquid separator V103, an alkaline water absorption tower T101, a mixer V104, a second booster pump P102, a raw material recovery tower T102, a molecular sieve adsorption component B2, a liquid membrane molecular sieve component B3, and a product separation tower T103. The process logistics involved include streams 6 to 28, which correspond to S6 to S28 in the figure respectively. The internal structure of the reactor R101 can be found in the attached Figure 1 As shown. The first catalyst filled in the first reaction zone of the reactor R101 is formed by CuO and auxiliary metals Mg and Ce loaded on a copper-aluminum spinel carrier, wherein the mass proportion of CuO is 25%, the mass proportion of Mg and Ce is 5%, and the mass proportion of the copper-aluminum spinel carrier is 70%; the second catalyst filled in the second reaction zone of the reactor R101 is formed by CuO and auxiliary metals Mg and La loaded on a copper-aluminum spinel carrier, wherein the mass proportion of CuO is 40%, the mass proportion of metal auxiliary Mg and La is 10%, and the mass proportion of the copper-aluminum spinel carrier is 50%.

[0070] The specific process is as follows:

[0071] Aniline and methanol are fed into the mixer V101 at a molar ratio of 1:5, and after being pressurized by the first booster pump P101, they are sent to the first heat exchanger E101 for heat exchange with the reaction product, and then supplemented with heat in the heater E102 to 190°C. The raw materials are completely converted into superheated gas (stream 6), and then enter the reactor R101 for catalytic reaction to obtain reaction gas (stream 7). Among them, the temperature in the upper cavity (first reaction zone) of the reactor is 300°C and the pressure is 1.7 MPa, and the temperature in the lower reaction cavity (second reaction zone) is 250°C and the pressure is normal pressure.

[0072] Furthermore, the flow rate of stream 7 is 1400 t / h, and the composition is: 13.21 v% N-methylaniline, 12.14 v% N, N-dimethylaniline, 11.23 v% methanol, 29.32 v% hydrogen, 13.08 v% carbon dioxide, 12.96 v% water, and the rest are heavy impurities.

[0073] The reaction gas (stream 8) after heat exchange treatment still has low-grade heat, which is sent to the second heat exchanger E103 for heat exchange treatment with the cold water for residents (20 ℃) ​​in the cooler, heating the cold water for residents to 62 ℃ (adjustable according to the boost range) and cooling itself to 18 ℃.

[0074] The reaction gas (stream 9) after cooling enters the first gas-liquid separator V102 for treatment. The separated gas phase includes carbon dioxide, hydrogen and methanol, which is transported to the compressor C101 for compression and pressurization treatment (the compression ratio is set to 2-3), and then enters the cooler E104 to cool down to 25 °C, and then enters the second gas-liquid separator V103 for separation treatment. The separated gas phase includes carbon dioxide and hydrogen, which is transported to the alkaline water absorption tower T101, and the carbon dioxide in the gas phase is recovered by the absorbent (stream 16). The absorbent is recycled and regularly replaced and regenerated depending on the process conditions. Hydrogen-rich gas (stream 17, hydrogen with a purity of 99.9~99.99%) is obtained at the top of the alkaline water absorption tower T101.

[0075] Furthermore, by changing the process conditions, the pressure of the high-purity hydrogen obtained at the top of the alkaline water absorption tower T101 can be adjusted within a certain range, which is of great benefit in reducing the investment in boosting equipment and reducing the floor space, and provides strong support for the downstream utilization of hydrogen.

[0076] The liquid phase (stream 11) obtained from the first gas-liquid separator V102 and the liquid phase (stream 14) recovered from the second gas-liquid separator V103 are both transported to the mixer V104. The liquid phase mixture (stream 19) of the mixer V104 is transported to the raw material recovery tower T102 via the second booster pump P102. Methanol and water (stream 21) are produced from the top of the tower, and the product-rich liquid (stream 24) is produced from the bottom of the tower. Methanol and water (stream 21) enter the molecular sieve adsorption component B2 and are separated by molecular sieve adsorption. Methanol is recycled as a raw material (stream 23), and water is treated as wastewater (stream 22). The product-rich liquid (stream 24) is passed into the liquid membrane molecular sieve component B3 for filtration to obtain a crude product (a mixed liquid of N-methylaniline and N,N-dimethylaniline, stream 26) and a heavy component (stream s25). The heavy component (stream s25) is sent to the outside of the system for filtration; the crude product (stream 26) is transported to the product separation tower T103 for product separation, and N,N-dimethyltoluene product (stream 27) is taken out from the top of the tower, and N-methylaniline product (stream 28) is taken out from the bottom of the tower.

[0077] It should be noted that the top heat load of the raw material recovery tower T102 is -220 kW, the bottom heat load is 291.6KW, the number of plates is 30, and 15 plates in the tower are fed; the top heat load of the product separation tower T103 is -27.5 KW, the bottom heat load is 21.6 KW, the number of plates is 35, and 17 plates in the tower are fed. Further, in the above process flow, the composition of the crude product is (N-methylaniline 49.5 wt%, N, N-dimethylaniline 50.5 wt%, impurities less than 0.02 wt%), the purity of the N-methylaniline product produced by the separation tower T103 is not less than 99.97%, and the purity of the produced N, N-dimethylaniline is not less than 99%.

[0078] Example 2

[0079] The specific process flow used in Example 2 is the same as that in Example 1, except that, in Example 2, the first catalyst filled in the first reaction zone of reactor R101 is specifically formed by CuO and metal additive Zr loaded on a silica carrier, wherein the mass proportion of CuO is 15%, the mass proportion of the metal additive Zr is 15%, and the mass proportion of the silica carrier is 70%; the second catalyst filled in the second reaction zone of reactor R101 is specifically formed by CuO and metal additives Zr and Co loaded on a silica carrier, wherein the mass proportion of CuO is 30%, the mass proportion of the metal additives Zr and Co is 20%, and the mass proportion of the silica carrier is 50%.

[0080] The composition of the obtained crude product is (N-methylaniline 34.06 wt%, N,N-dimethylaniline 65.23 wt%, impurities less than 0.71 wt%), the purity of the N-methylaniline product produced by the separation tower T103 is not less than 99.98%, and the purity of the produced N,N-dimethylaniline is not less than 99.31%.

[0081] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0082] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0083] The above is a detailed introduction to a system for co-producing N-methylaniline and N,N-dimethylaniline provided by the present invention. Specific examples are used herein to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A system for co-producing N-methylaniline and N,N-dimethylaniline, characterized in that: It comprises a reactor; the reactor comprises a first reaction zone and a second reaction zone which are sequentially connected along the axial direction; the first reaction zone is filled with a first catalyst; the second reaction zone is filled with a second catalyst; Aniline and methanol in a molar ratio of 1:1 to 1:8 are used as reaction raw materials. After entering the first reaction zone, they are catalytically converted into N,N-dimethylaniline under the conditions of 280-340° C. and 1.5-2 MPa. When the first mixed flow including the product accumulated in the first reaction zone flows through the second reaction zone, the remaining unreacted aniline and methanol therein are catalytically converted into N-methylaniline under the conditions of 220-250° C. and 0-0.5 MPa, thereby obtaining a second mixed flow containing 40-50% N,N-dimethylaniline and 50-60% N-methylaniline. The first reaction zone is in the shape of a straight cylinder with a constant radial dimension, and the second reaction zone is in the shape of a truncated cone with a radial dimension that gradually increases in a direction away from the first reaction zone. The first catalyst is formed by CuO and a promoter metal loaded on a carrier; wherein, The carrier includes copper aluminum spinel, silicon dioxide, aluminum oxide or zeolite molecular sieve, accounting for 60-70% by mass; The auxiliary metal is selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, with a mass ratio of 5-15%; The mass proportion of CuO is 10-30%; The second catalyst is formed by CuO and a promoter metal loaded on a carrier; wherein, The carrier includes copper aluminum spinel, silicon dioxide, aluminum oxide or zeolite molecular sieve, with a mass ratio of 45-65%; The auxiliary metal is selected from at least one of Ce, La, Zr, Mo, Y, Co and Mg, with a mass ratio of 10-20%; The mass proportion of the CuO is 30-45%.

2. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 1, characterized in that: The first reaction zone and the second reaction zone are respectively provided with independent temperature control components and pressure control components.

3. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 1, characterized in that: A throttling component is provided at the connecting portion between the first reaction zone and the second reaction zone, and the throttling component is used to control the flow rate of the first mixed flow entering the second reaction zone.

4. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 1, characterized in that: The system also includes a gas-liquid separation subsystem, a gas phase separation subsystem and a liquid phase separation subsystem; wherein, The gas-liquid separation subsystem is in communication with the second reaction zone and is used for performing gas-liquid separation on the second mixed flow to obtain a first gas phase component and a first liquid phase component containing N-methylaniline and N,N-dimethylaniline; The gas phase separation subsystem is in communication with the gas-liquid separation subsystem and is used to receive the first gas phase component and separate high-purity hydrogen therefrom; The liquid phase separation subsystem is in communication with the gas-liquid separation subsystem and is used for receiving the first liquid phase component and separating N-methylaniline and N,N-dimethylaniline therefrom.

5. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 4, characterized in that: The gas phase separation subsystem includes a compressor, a condenser, a gas-liquid separator and an absorption tower; The compressor is connected to the condenser, and the condenser is connected to the gas-liquid separator. After being compressed by the compressor, the first gas phase component enters the condenser for condensation treatment, and then enters the gas-liquid separator for gas-liquid separation to obtain a second gas phase component and a second liquid phase component. The gas-liquid separator is connected to the absorption tower, and the second gas phase component continues to be introduced into the absorption tower containing alkaline water to absorb carbon dioxide, and the remainder is high-purity hydrogen.

6. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 4, characterized in that: The liquid phase separation subsystem includes a raw material recovery tower, a molecular sieve adsorption assembly, a liquid membrane molecular sieve assembly and a product separation tower, the raw material recovery tower is connected to the molecular sieve adsorption assembly, and the raw material recovery tower, the liquid membrane molecular sieve assembly and the product separation tower are connected in sequence; The first liquid phase component enters the raw material recovery tower, and the methanol and water gathered at the top of the tower are filtered through the molecular sieve adsorption component to separate the methanol for reuse as raw material; the product-rich liquid gathered at the bottom of the tower is filtered through the liquid membrane molecular sieve component to separate N-methylaniline and N,N-dimethylaniline from the heavy components; the N-methylaniline and N,N-dimethylaniline are separated in the product separation tower, and N,N-dimethylaniline is extracted from the top of the tower and N-methylaniline is extracted from the bottom of the tower.

7. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 5, characterized in that: A mixer is further provided between the liquid phase separation subsystem and the gas-liquid separation subsystem, and the mixer is used to receive the second liquid phase component and the first liquid phase component and send them into the liquid phase separation subsystem.

8. The system for co-producing N-methylaniline and N,N-dimethylaniline according to claim 4, characterized in that: A heat exchange subsystem is also provided between the gas-liquid separation subsystem and the reactor. After the reaction raw materials and the second mixed flow exchange heat through the heat exchange subsystem, the reaction raw materials enter the reactor and the second mixed flow enters the gas-liquid separation subsystem.

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