Mononitrification continuous production system for aromatic hydrocarbon

Abstract

The invention relates to the technical field of aromatic hydrocarbon nitration, in particular to a single nitration continuous production system for aromatic hydrocarbon. The invention discloses a mononitration continuous production system for aromatic hydrocarbon. The mononitration continuous production system comprises a feeding unit, a reaction unit, a separation unit, a recovery unit and a collection unit, the feeding unit comprises an aromatic hydrocarbon feeding mechanism and a mixed acid feeding mechanism, and the reaction unit comprises a continuous flow reactor; a discharge port of the reaction unit is communicated with a feed port of the separation unit, and a discharge port of the separation unit is communicated with the recovery unit; a discharge hole of the first recycling unit is communicated with the aromatic hydrocarbon feeding mechanism and the collecting unit respectively, and the second recycling unit is communicated with the mixed acid feeding mechanism. According to the invention, the continuous flow reactor is used as a reactor of aromatic hydrocarbon and nitric-sulfuric acid mixture, so that excellent heat and mass transfer efficiency is realized, and the safety risk is greatly reduced; meanwhile, solvents and waste acid in the reacted materials are not recycled, so that on one hand, the raw material cost is reduced, and on the other hand, wastes are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of aromatic hydrocarbon nitration, in particular to a single nitration continuous production system for aromatic hydrocarbons. Background Art

[0002] The mononitration products of aromatic hydrocarbons can be used to manufacture a variety of fine chemical products such as medicines, pesticides, dyes, polymer additives, etc. Therefore, the mononitration of aromatic hydrocarbons has always received extensive attention and development. The industrial nitration reaction of aromatic hydrocarbons generally uses a mixed acid of nitric acid and sulfuric acid, which is carried out in a kettle reactor. Aromatic hydrocarbons and the mixed acid enter the reactor at the same time to react. However, the kettle reactor is prone to local overheating, which not only causes an increase in by-products, but also easily causes explosions and other hazards if not properly controlled. The main reasons for the poor safety of the mononitration reaction of aromatic hydrocarbons are: (1) Thermal instability of the material system: Nitration products generally have dangerous characteristics such as low flash point, low boiling point, and a wide range of explosion limits; nitrating agents are highly oxidizing and corrosive, and are easily decomposed to cause material impact or even explosion; (2) Thermal hazards of the reaction process: Nitration is a rapid and highly exothermic process; and aromatic hydrocarbons are prone to oxidation and polynitration and other side reactions under high temperature conditions, resulting in increased heat release in the system and soaring temperatures, leading to combustion and explosion accidents.

[0003] In order to improve the safety of the aromatics mononitration process, the existing technologies mostly start from the following aspects: changing the structure of the traditional autoclave reactor, increasing the heat transfer and mass transfer in the autoclave reactor; replacing the nitrating agent and catalyst, such as replacing the traditional nitric acid and sulfuric acid mixed acid with nitrate ester nitrating agent, rare earth metal salt catalyst, etc. However, the above improvements have not fundamentally changed the safety hazards in the aromatics nitration process, and the changes in the nitrating agent and catalyst have greatly increased the production cost, which is not suitable for industrial large-scale production.

[0004] Therefore, how to provide a production system that can ensure the safety of the mononitration production of aromatics, the conversion rate of raw materials, the mononitration selectivity, etc. is of great significance to the development of aromatic mononitration products.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a continuous production system for mononitration of aromatic hydrocarbons to solve the technical problems of poor safety and high cost in the prior art.

[0007] In order to achieve the above-mentioned object of the present invention, the present invention provides a continuous production system for mononitration of aromatic hydrocarbons, comprising: a feeding unit, a reaction unit, a separation unit, a recovery unit and a collection unit;

[0008] The feed unit includes an aromatic feed mechanism and a mixed acid feed mechanism, and the reaction unit includes a continuous flow reactor; the aromatic feed mechanism is connected to the feed port of the reaction unit to transport aromatic raw materials to the reaction unit; the mixed acid feed mechanism is connected to the feed port of the reaction unit to transport mixed acid to the reaction unit;

[0009] The discharge port of the reaction unit is connected to the feed port of the separation unit, and the discharge port of the separation unit is connected to the recovery unit;

[0010] The recovery unit comprises a first recovery unit and a second recovery unit, the discharge port of the first recovery unit is respectively connected to the aromatic hydrocarbon feed mechanism and the collection unit, and the second recovery unit is connected to the mixed acid feed mechanism.

[0011] In a specific embodiment of the present invention, the aromatic hydrocarbon feeding mechanism includes a solvent storage tank, an aromatic hydrocarbon storage tank and a solution storage tank; the outlets of the solvent storage tank and the aromatic hydrocarbon storage tank are respectively connected to the inlet of the solution storage tank, and the outlet of the solution storage tank is connected to the feed port of the reaction unit.

[0012] In a specific embodiment of the present invention, the mixed acid feeding mechanism includes a nitric acid storage tank, a sulfuric acid storage tank and a mixed acid storage tank; the outlets of the nitric acid storage tank and the sulfuric acid storage tank are respectively connected to the inlet of the mixed acid storage tank, and the outlet of the mixed acid storage tank is connected to the feed port of the reaction unit.

[0013] In a specific embodiment of the present invention, the aromatic hydrocarbon feeding mechanism further includes a first feeding pump, and the mixed acid feeding mechanism further includes a second feeding pump; the first feeding pump is arranged between the outlet of the solution storage tank and the feeding port of the reaction unit, and the second feeding pump is arranged between the outlet of the mixed acid storage tank and the feeding port of the reaction unit. The ratio of the aromatic hydrocarbon and the mixed acid entering the reaction unit is controlled by the first feeding pump and the second feeding pump.

[0014] In a specific embodiment of the present invention, the separation unit comprises a membrane separation mechanism. Further, the membrane separation mechanism comprises a Zaiput liquid-liquid separator.

[0015] In a specific embodiment of the present invention, the membrane separation mechanism includes an organic phase outlet and an aqueous phase outlet; the organic phase outlet is connected to the feed inlet of the first recovery unit, and the aqueous phase outlet is connected to the feed inlet of the second recovery unit.

[0016] In a specific embodiment of the present invention, the first recovery unit includes an organic phase storage tank, a concentration mechanism and a recovery solvent storage tank, the feed inlet of the organic phase storage tank is connected to the organic phase outlet; the concentration mechanism includes a product outlet and a recovery solvent outlet; the product outlet is connected to the collection unit, and the recovery solvent outlet is connected to the recovery solvent storage tank; the outlet of the recovery solvent storage tank is connected to the inlet of the solvent storage tank.

[0017] In a specific embodiment of the present invention, the second recovery unit includes a water phase storage tank, a waste acid storage tank and an online detection mechanism, the feed port of the water phase storage tank is connected to the water phase outlet; the discharge port of the water phase storage tank is connected to the feed port of the waste acid storage tank, and the online detection mechanism is used to detect the composition of the waste acid flowing out of the discharge port of the waste acid storage tank; the outlet of the waste acid storage tank is connected to the inlet of the mixed acid storage tank. Further, the waste acid enters the mixed acid storage tank, mixes with fresh nitric acid and sulfuric acid, and continuously produces mixed acid for reaction.

[0018] In a specific embodiment of the present invention, the online detection mechanism includes an online ultraviolet detector.

[0019] In a specific embodiment of the present invention, a first valve is provided between the outlet of the solvent storage tank and the inlet of the solution storage tank, a second valve is provided between the outlet of the aromatic hydrocarbon storage tank and the inlet of the solution storage tank; a third valve is provided between the outlet of the nitric acid storage tank and the inlet of the mixed acid storage tank, and a fourth valve is provided between the outlet of the sulfuric acid storage tank and the inlet of the mixed acid storage tank. The feed flow rate is controlled by adjusting the opening of each valve.

[0020] In a specific embodiment of the present invention, a fifth valve is provided between the outlet of the recovery solvent storage tank and the inlet of the solvent storage tank; and a sixth valve is provided between the outlet of the waste acid storage tank and the inlet of the mixed acid storage tank.

[0021] In a specific embodiment of the present invention, the system also includes a controller; the controller is electrically connected to the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the first feed pump, the second feed pump and the online detection mechanism respectively.

[0022] In a specific embodiment of the present invention, in the mixed acid, the mass fraction of the sulfuric acid is 65% to 75%, and the molar ratio of the sulfuric acid to the nitric acid is (1.5 to 1.7):1.

[0023] In a specific embodiment of the present invention, the molar ratio of the nitric acid to the aromatic hydrocarbon feedstock entering the reaction unit is (3-5):1.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention adopts a continuous flow reactor as a reactor for aromatic hydrocarbons and nitric and sulfuric acid mixed acid, achieves excellent heat and mass transfer efficiency, and greatly reduces safety risks; at the same time, the nitrating agent and the catalyst are not changed, and the nitric acid and sulfuric acid system is still used. The solvent and waste acid in the materials after the reaction are further recovered, which reduces the raw material cost on the one hand and reduces waste on the other. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure of a system for continuous production of mononitration of aromatic hydrocarbons provided in an embodiment of the present invention.

[0028] Reference numerals:

[0029] 11-Solvent storage tank; 12-Aromatic hydrocarbon storage tank; 13-Solution storage tank;

[0030] 14-first feed pump; 21-nitric acid storage tank; 22-sulphuric acid storage tank;

[0031] 23-mixed acid storage tank; 24-second feed pump; 3-reaction unit;

[0032] 4-separation unit; 51-organic phase storage tank; 52-concentration mechanism;

[0033] 53-recovery solvent storage tank; 61-water phase storage tank; 64-waste acid storage tank;

[0034] 65-online detection mechanism; 71-first valve; 72-second valve;

[0035] 73-the third valve; 74-the fourth valve; 75-the fifth valve;

[0036] 76-sixth valve; 8-collection unit. DETAILED DESCRIPTION

[0037] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] Figure 1 A schematic diagram of the structure of a continuous production system for mononitration of aromatic hydrocarbons provided in an embodiment of the present invention. The continuous production system for mononitration of aromatic hydrocarbons provided in this embodiment includes: a feeding unit, a reaction unit, a separation unit, a recovery unit and a collection unit;

[0041] The feed unit includes an aromatic feed mechanism and a mixed acid feed mechanism, and the reaction unit includes a continuous flow reactor; the aromatic feed mechanism is connected to the feed port of the reaction unit to transport the aromatic raw material to the reaction unit; the mixed acid feed mechanism is connected to the feed port of the reaction unit to transport the mixed acid to the reaction unit;

[0042] The discharge port of the reaction unit is connected to the feed port of the separation unit, and the discharge port of the separation unit is connected to the recovery unit;

[0043] The recovery unit comprises a first recovery unit and a second recovery unit. The discharge port of the first recovery unit is respectively connected to the aromatic hydrocarbon feeding mechanism and the collecting unit, and the second recovery unit is connected to the mixed acid feeding mechanism.

[0044] The mononitration continuous production system for aromatic hydrocarbons of the present invention has the following advantages:

[0045] By adopting a continuous flow reactor as the reactor for aromatic hydrocarbons and nitric acid and sulfuric acid mixture, excellent heat and mass transfer efficiency is achieved, greatly reducing safety risks; at the same time, the nitrating agent and catalyst are not changed, and the nitric acid and sulfuric acid system is still used. The solvent and waste acid in the post-reaction materials are further recovered, which reduces the raw material cost on the one hand and reduces waste on the other.

[0046] It is understandable that the continuous flow reactor in the present invention may adopt an existing conventional continuous flow reactor, such as a Corning G1 continuous flow reactor, but is not limited thereto.

[0047] Furthermore, the aromatics feeding mechanism includes a solvent storage tank 11, an aromatics storage tank 12 and a solution storage tank 13; the outlets of the solvent storage tank 11 and the aromatics storage tank 12 are respectively connected to the inlet of the solution storage tank 13, and the outlet of the solution storage tank 13 is connected to the feed port of the reaction unit 3.

[0048] The solvent and the aromatic hydrocarbons are transported to the solution storage tank 13 through the solvent storage tank 11 and the aromatic hydrocarbon storage tank 12 respectively, and are evenly mixed in the solution storage tank 13 to obtain an aromatic hydrocarbon solution, which is then transported to the reaction unit 3 for subsequent reaction.

[0049] It is understandable that the solvent storage tank 11 is adjusted according to actual conditions. For example, in the nitration reaction of aromatic hydrocarbons, no additional solvent needs to be added, but the aromatic hydrocarbon raw material is directly reacted with the mixed acid, so there is no need to set up the solvent storage tank 11.

[0050] In a specific embodiment of the present invention, the mixed acid feeding mechanism includes a nitric acid storage tank 21, a sulfuric acid storage tank 22 and a mixed acid storage tank 23; the outlets of the nitric acid storage tank 21 and the sulfuric acid storage tank 22 are respectively connected to the inlet of the mixed acid storage tank 23, and the outlet of the mixed acid storage tank 23 is connected to the feed port of the reaction unit 3.

[0051] By setting up the nitric acid storage tank 21 and the sulfuric acid storage tank 22, according to the component requirements of the mixed acid, the nitric acid and the sulfuric acid are respectively transported to the mixed acid storage tank 23, mixed evenly in the mixed acid storage tank 23 to obtain the mixed acid, and then transported to the reaction unit 3 for subsequent reaction.

[0052] It is understandable that when additional water needs to be added during the preparation of the mixed acid, the mixed acid feeding mechanism may also include a water storage tank, the outlet of the water storage tank is connected to the inlet of the mixed acid storage tank, and the content of water added is selected according to the actual requirements of the mixed acid composition.

[0053] In actual operation, the lining material of the nitric acid storage tank 21, the sulfuric acid storage tank 22 and the mixed acid storage tank 23 can be polytetrafluoroethylene, enamel, glass, etc., but is not limited thereto, to avoid corrosion to the storage tanks.

[0054] In a specific embodiment of the present invention, the aromatic hydrocarbon feeding mechanism also includes a first feed pump 14, and the mixed acid feeding mechanism also includes a second feed pump 24; the first feed pump 14 is arranged between the outlet of the solution storage tank 13 and the feed port of the reaction unit 3, and the second feed pump 24 is arranged between the outlet of the mixed acid storage tank 23 and the feed port of the reaction unit 3.

[0055] The ratio of aromatic hydrocarbons and mixed acid entering the reaction unit 3 is regulated by the first feed pump 14 and the second feed pump 24. For example, in the present invention, the molar ratio of nitric acid to aromatic hydrocarbon raw material in the mixed acid entering the reaction unit 3 is (3-5) : 1 by regulating the first feed pump 14 and the second feed pump 24, so as to ensure the smooth progress of the nitration reaction and the mononitration selectivity.

[0056] It can be understood that the types of the first feed pump 14 and the second feed pump 24 can be selected according to actual conditions, and can realize the delivery of aromatic hydrocarbons and mixed acid to the reaction unit 3, and can adjust the flow rate of aromatic hydrocarbons and mixed acid according to actual setting requirements, such as a plunger pump, but not limited to this.

[0057] In a specific embodiment of the present invention, the separation unit 4 comprises a membrane separation mechanism. Further, the membrane separation mechanism comprises a Zaiput liquid-liquid separator.

[0058] In a specific embodiment of the present invention, the membrane separation mechanism includes an organic phase outlet and an aqueous phase outlet; the organic phase outlet is connected to the feed inlet of the first recovery unit, and the aqueous phase outlet is connected to the feed inlet of the second recovery unit.

[0059] The material after the reaction in the reaction unit 3 flows out from the discharge port of the reaction unit 3 and enters the membrane separation mechanism, and the membrane separation mechanism completes the separation of the organic phase and the aqueous phase. The separated organic phase is sent to the first recovery unit from the organic phase outlet, and the separated aqueous phase is sent to the second recovery unit from the aqueous phase outlet.

[0060] In a specific embodiment of the present invention, the first recovery unit includes an organic phase storage tank 51, a concentration mechanism 52 and a recovery solvent storage tank 53, the feed port of the organic phase storage tank 51 is connected to the organic phase outlet of the membrane separation mechanism; the concentration mechanism 52 includes a product outlet and a recovery solvent outlet; the product outlet is connected to the collection unit 8, and the recovery solvent outlet is connected to the recovery solvent storage tank 53; the outlet of the recovery solvent storage tank 53 is connected to the inlet of the solvent storage tank 11.

[0061] The organic phase separated by the membrane separation mechanism is sent to the organic phase storage tank 51 of the first recovery unit, and then enters the concentration mechanism 52 for concentration to separate the solvent and the product. The solvent is sent to the recovery solvent storage tank 53 from the recovery solvent outlet, and the product is sent to the collection unit 8 from the product outlet for collecting the mononitrated aromatic hydrocarbon product obtained by the reaction.

[0062] In a specific embodiment of the present invention, the second recovery unit includes a water phase storage tank 61, a waste acid storage tank 64 and an online detection mechanism 65, the feed port of the water phase storage tank 61 is connected to the water phase outlet of the membrane separation mechanism; the discharge port of the water phase storage tank 61 is connected to the waste acid storage tank 64, and the online detection mechanism 65 is used to detect the composition of the waste acid flowing out of the discharge port of the waste acid storage tank 64; the outlet of the waste acid storage tank 64 is connected to the inlet of the mixed acid storage tank 23. Further, the waste acid enters the mixed acid storage tank 23, is mixed with fresh nitric acid and sulfuric acid, and continuously produces mixed acid for reaction.

[0063] In actual operation, according to the waste acid composition detected by the online detection mechanism 65, fresh nitric acid and sulfuric acid are added as needed from the nitric acid storage tank 21 and the sulfuric acid storage tank 22, so that the mixed acid obtained by mixing in the mixed acid storage tank 23 satisfies: the mass fraction of sulfuric acid is 65% to 75%, and the molar ratio of sulfuric acid to nitric acid is (1.5 to 1.7):1.

[0064] In a specific embodiment of the present invention, the online detection mechanism 65 includes an online ultraviolet detector.

[0065] In a specific embodiment of the present invention, a first valve 71 is provided between the outlet of the solvent storage tank 11 and the inlet of the solution storage tank 13, a second valve 72 is provided between the outlet of the aromatics storage tank 12 and the inlet of the solution storage tank 13; a third valve 73 is provided between the outlet of the nitric acid storage tank 21 and the inlet of the mixed acid storage tank 23, and a fourth valve 74 is provided between the outlet of the sulfuric acid storage tank 22 and the inlet of the mixed acid storage tank 23. The feed flow rate is controlled by adjusting the opening of each valve.

[0066] In a specific embodiment of the present invention, a fifth valve 75 is provided between the outlet of the recovery solvent storage tank 53 and the inlet of the solvent storage tank 11 ; a sixth valve 76 is provided between the outlet of the waste acid storage tank 64 and the inlet of the mixed acid storage tank 23 .

[0067] For example, by adjusting the opening of the first valve 71 and the second valve 72, the amount of aromatic hydrocarbons and solvents fed into the solution storage tank 13 is further adjusted, so that the aromatic hydrocarbon solution meets the corresponding requirements. By adjusting the opening of the third valve 73 and the fourth valve 74, the sixth valve 76 is further adjusted, so that the prepared mixed acid meets the requirements that the mass fraction of sulfuric acid is 65% to 75%, and the molar ratio of sulfuric acid to nitric acid is (1.5 to 1.7):1.

[0068] In a specific embodiment of the present invention, the system also includes a controller; the controller is electrically connected to the first valve 71, the second valve 72, the third valve 73, the fourth valve 74, the fifth valve 75, the sixth valve 76, the first feed pump 14, the second feed pump 24 and the online detection mechanism 65 respectively.

[0069] According to the preset requirements, the openings of the first valve 71, the second valve 72 and the fifth valve 75 are regulated so that the aromatic solution mixed in the solution storage tank 13 has a corresponding concentration; the openings of the third valve 73, the fourth valve 74 and the sixth valve 76 are regulated so that the mixed acid mixed in the mixed acid storage tank 23 has a corresponding composition; and the feed rates of the first feed pump 14 and the second feed pump 24 are controlled to regulate the ratio of aromatics and mixed acid entering the reaction unit 3, and the flow rate is controlled so that it has a certain residence time in the reaction unit 3.

[0070] In a specific embodiment of the present invention, the openings of the first valve 71, the second valve 72 and the fifth valve 75 are adjusted so that the concentration of the aromatic solution mixed in the solution storage tank 13 is 0.1-1 g / mL.

[0071] In a specific embodiment of the present invention, the openings of the third valve 73, the fourth valve 74 and the sixth valve 76 are regulated so that the mass fraction of sulfuric acid in the mixed acid obtained in the mixed acid storage tank 23 is 65% to 75%, and the molar ratio of sulfuric acid to nitric acid is (1.5 to 1.7):1.

[0072] In a specific embodiment of the present invention, the first feed pump 14 and the second feed pump 24 are regulated so that the molar ratio of nitric acid to aromatic hydrocarbon raw material in the mixed acid and aromatic hydrocarbon solution entering the reaction unit 3 is (3-5):1; the total flow rate of the mixed acid and aromatic hydrocarbon solution is 20-240 mL / min, so that the mixing residence time in the reaction zone of the continuous flow reactor is 10-123 s.

[0073] In a specific embodiment of the present invention, the aromatic hydrocarbons include but are not limited to at least one of o-xylene, p-xylene, chlorobenzene and toluene.

[0074] The present invention adopts a continuous flow reactor as a reactor for aromatic hydrocarbons and nitric and sulfuric acid mixed acid, achieves excellent heat and mass transfer efficiency, and greatly reduces safety risks; at the same time, the nitrating agent and catalyst are not changed, and the nitric acid and sulfuric acid system is still used. The solvent and waste acid in the materials after the reaction are further recovered, which reduces the cost of raw materials on the one hand and reduces waste on the other hand. In addition, by regulating the composition of the mixed acid and the ratio of nitric acid to aromatic hydrocarbons in the mixed acid, the mononitration selectivity, conversion rate and product yield in the mononitration reaction of aromatic hydrocarbons are further improved.

[0075] Taking o-xylene as an example, a method for mononitration of o-xylene using the mononitration continuous production system for aromatic hydrocarbons of the present invention is specifically provided, comprising the following steps:

[0076] (1) The solvent storage tank 11 and the aromatic hydrocarbon storage tank 12 respectively transport CH2Cl2 solvent and o-xylene to the solution storage tank 13, and the two solvents are evenly mixed in the solution storage tank 13 to obtain a solution with an o-xylene concentration of 0.5 g / mL.

[0077] (2) The nitric acid storage tank 21 and the sulfuric acid storage tank 22 respectively transport nitric acid and sulfuric acid to the mixed acid storage tank 23 (an appropriate amount of water can be added to the water storage tank), and the mixed acid is evenly mixed in the mixed acid storage tank 23 to obtain a mixed acid with a molar ratio of sulfuric acid to nitric acid of 1.6:1 and a mass fraction of sulfuric acid of 70%.

[0078] (3) The first feed pump 14 and the second feed pump 24 are simultaneously turned on to deliver the o-xylene solution and the mixed acid to the continuous flow reactor. The total flow rate of the two streams of materials is 56 mL / min. At the same time, the o-xylene solution and the mixed acid are controlled to meet the following conditions: the molar ratio of o-xylene to nitric acid is 1:4.4, and the reaction temperature is set to 80° C. The reacted materials flow out of the discharge port of the continuous flow reactor and enter the membrane separation mechanism to separate the organic phase and the inorganic phase.

[0079] (4) The organic phase separated in step (3) is sent to the organic phase storage tank 51 of the first recovery unit, and then sent to the concentration mechanism for reduced pressure concentration to separate the solvent and the product; the product is sent to the collection unit 8 from the product outlet, and the recovered solvent is sent to the recovered solvent storage tank 53 from the recovered solvent outlet.

[0080] The aqueous phase separated in step (3) is sent to the aqueous phase storage tank 61 of the second recovery unit, and then sent to the waste acid storage tank 64, and the composition of the waste acid is detected by the online detection mechanism 65.

[0081] (5) The solvent recovered in the recovery solvent storage tank 53 is added to the solvent storage tank 11, and the waste acid recovered in the waste acid storage tank 64 is sent to the mixed acid storage tank 23. At the same time, according to the composition of the detected waste acid, the amount of nitric acid and sulfuric acid sent to the mixed acid storage tank 23 by the nitric acid storage tank 21 and the sulfuric acid storage tank 22 is adjusted again (an appropriate amount of water can be added to the water storage tank) to make the molar ratio of sulfuric acid to nitric acid in the mixed acid storage tank 23 be 1.6:1 and the mass fraction of sulfuric acid be 70%. The reaction is carried out in a continuous cycle.

[0082] By using the method of this embodiment, the conversion rate of raw material o-xylene is 99.9%, and the total yield of mononitrate is 96.5%.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A continuous production system for mononitration of aromatic hydrocarbons, characterized in that: include: Feed unit, reaction unit, separation unit, recovery unit and collection unit; The feed unit includes an aromatic feed mechanism and a mixed acid feed mechanism, and the reaction unit includes a continuous flow reactor; the aromatic feed mechanism is connected to the feed port of the reaction unit to transport aromatic raw materials to the reaction unit; the mixed acid feed mechanism is connected to the feed port of the reaction unit to transport mixed acid to the reaction unit; The discharge port of the reaction unit is connected to the feed port of the separation unit, and the discharge port of the separation unit is connected to the recovery unit; The recovery unit comprises a first recovery unit and a second recovery unit, the discharge port of the first recovery unit is respectively connected to the aromatic hydrocarbon feed mechanism and the collection unit, and the second recovery unit is connected to the mixed acid feed mechanism.

2. The continuous production system for mononitration of aromatic hydrocarbons according to claim 1, characterized in that: The aromatic hydrocarbon feeding mechanism comprises a solvent storage tank, an aromatic hydrocarbon storage tank and a solution storage tank; the outlets of the solvent storage tank and the aromatic hydrocarbon storage tank are respectively connected to the inlet of the solution storage tank, and the outlet of the solution storage tank is connected to the feed port of the reaction unit; The mixed acid feeding mechanism comprises a nitric acid storage tank, a sulfuric acid storage tank and a mixed acid storage tank; the outlets of the nitric acid storage tank and the sulfuric acid storage tank are respectively connected to the inlet of the mixed acid storage tank, and the outlet of the mixed acid storage tank is connected to the feed port of the reaction unit.

3. The continuous production system for mononitration of aromatic hydrocarbons according to claim 2, characterized in that: The aromatic hydrocarbon feeding mechanism also includes a first feed pump, and the mixed acid feeding mechanism also includes a second feed pump; the first feed pump is arranged between the outlet of the solution storage tank and the feed inlet of the reaction unit, and the second feed pump is arranged between the outlet of the mixed acid storage tank and the feed inlet of the reaction unit.

4. The continuous production system for mononitration of aromatic hydrocarbons according to claim 1, characterized in that: The separation unit comprises a membrane separation mechanism; Preferably, the membrane separation mechanism comprises a Zaiput liquid-liquid separator.

5. The continuous production system for mononitration of aromatic hydrocarbons according to claim 4, characterized in that: The membrane separation mechanism comprises an organic phase outlet and a water phase outlet; the organic phase outlet is connected to the feed inlet of the first recovery unit, and the water phase outlet is connected to the feed inlet of the second recovery unit.

6. The continuous production system for mononitration of aromatic hydrocarbons according to claim 2, characterized in that: The first recovery unit comprises an organic phase storage tank, a concentration mechanism and a recovery solvent storage tank, wherein the feed port of the organic phase storage tank is connected to the organic phase outlet; the concentration mechanism comprises a product outlet and a recovery solvent outlet; the product outlet is connected to the collection unit, and the recovery solvent outlet is connected to the recovery solvent storage tank; the outlet of the recovery solvent storage tank is connected to the inlet of the solvent storage tank; Preferably, a fifth valve is provided between the outlet of the recovery solvent storage tank and the inlet of the solvent storage tank.

7. The continuous production system for mononitration of aromatic hydrocarbons according to claim 6, characterized in that: The second recovery unit comprises a water phase storage tank, a waste acid storage tank and an online detection mechanism, wherein the feed port of the water phase storage tank is connected to the water phase outlet; the discharge port of the water phase storage tank is connected to the feed port of the waste acid storage tank, and the online detection mechanism is used to detect the composition of the waste acid flowing out of the discharge port of the waste acid storage tank; the outlet of the waste acid storage tank is connected to the inlet of the mixed acid storage tank; Preferably, the online detection mechanism includes an online ultraviolet detector.

8. The continuous production system for mononitration of aromatic hydrocarbons according to claim 7, characterized in that: A first valve is arranged between the outlet of the solvent storage tank and the inlet of the solution storage tank, a second valve is arranged between the outlet of the aromatic hydrocarbon storage tank and the inlet of the solution storage tank; a third valve is arranged between the outlet of the nitric acid storage tank and the inlet of the mixed acid storage tank, a fourth valve is arranged between the outlet of the sulfuric acid storage tank and the inlet of the mixed acid storage tank.

9. The system for continuous production of mononitration of aromatic hydrocarbons according to claim 8, characterized in that: A sixth valve is provided between the outlet of the waste acid storage tank and the inlet of the mixed acid storage tank.

10. The system for continuous production of mononitration of aromatic hydrocarbons according to claim 9, characterized in that: The system also includes a controller; the controller is electrically connected to the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the first feed pump, the second feed pump and the online detection mechanism respectively.

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