Method for deeply separating aromatic nitration product and method for supplying purified product to continuous flow high-order nitration ingredient

Abstract

The invention discloses a method for deeply separating an aromatic nitration product and a method for supplying a purified product to a continuous flow high-order nitration ingredient, and particularly relates to an emulsion nitride oil phase obtained by nitrating an aromatic compound through nitric acid and sulfuric acid and layering through oleic acid, the method for deeply separating and dispersing the acid phase comprises the following steps: injecting an emulsion nitride oil phase into a filtering device by adopting a microporous material of which the material surface energy is lower than 33 mJ / m as a filtering element, driving the emulsion nitride oil phase to be infiltrated in the tissue of the hydrophobic microporous material based on lower tension of the nitride, and combining the precision of micropores of the microporous material and a two-phase tension difference, so as to realize deep separation of the dispersed acid phase. Regulating and controlling the operation parameters of the filtering device to be matched with the attributes of the material and the medium, so that the oil phase and the microporous structure of the hydrophobic microporous material jointly form a complete tension liquid film, constructing sustainable differential pressure filtration, and retaining and enriching the dispersed acid phase all the time under the pressure difference of 5-80 kPa, so as to obtain a clear, transparent and highly homogeneous nitride oil phase; according to the method, the dosage of a neutralizing agent and water can be greatly reduced in a neutralizing and washing link of the aromatic nitration product; for a graded continuous nitration production process, continuous and accurate burdening of a later-stage reaction can be directly supplied; for an online continuous flow nitration reaction device with a small volume, the device is particularly beneficial to the continuous, stable and flexible starting and stopping of a graded tandem reaction device.

Description

Technical Field

[0001] The invention belongs to the technical field of nitration of aromatic compounds, and in particular relates to a method for deeply separating aromatic nitration products and a method for purifying products for continuous flow high-order nitration ingredients. Background Art

[0002] The mixed acid nitration reaction of aromatic compounds such as benzene, toluene, and chlorobenzene uses nitric acid as a nitrating agent and high-concentration sulfuric acid as a catalyst. The reaction product is a mixed liquid of an oil phase and an acid phase. The oil phase is the corresponding primary or multi-stage nitration product such as nitrobenzene or dinitrobenzene, nitrotoluene or dinitrotoluene, nitrochlorobenzene or dinitrochlorobenzene, etc. The acid phase is composed of a mixed solution of water, sulfuric acid, and residual nitric acid generated by the reaction. In industrial production, the difference in specific gravity is used to separate the mixed products of the oil and acid phases to obtain a crude nitration product. Since the surface energies of the two phases are relatively close at the working temperature, the layered nitration product is mixed with acid solutions of different concentrations but stably dispersed, making the nitration product an emulsified oil phase. Studies have found that the solubility of nitric acid in nitrates is much greater than that of sulfuric acid, and the dispersed content of acid solutions in nitration products is positively correlated with the residual amount of nitric acid after the reaction. In addition, the nitration product wrapped with a dispersed acid phase is not only heterogeneously emulsified, but also the proportion of liquid components in different parts is significantly uneven when close to static, showing a stable heterogeneous characteristic.

[0003] In the above-mentioned aromatic graded series connection and continuous nitration reaction occasions, the front-stage nitration product is the raw material for subsequent nitration. Due to the heterogeneous characteristics of the above-mentioned blended dispersion, if the front-stage product is used as the feed for the subsequent reaction after being buffered, the reaction ratio will be difficult to maintain stability. Similarly, in the case of graded series connection and continuous reaction, the front-stage nitration product, i.e., the raw material for the subsequent nitration, is often used to extract the tail acid of the subsequent nitration, i.e., the applied acid solution of the front-stage nitration, and then the acid solution is separated again by stratification to obtain the primary nitrate after extraction. Since polynitro substances are extracted therein, the heterogeneity between the dispersed acid and the nitrate in the material will be more serious. On the other hand, in recent years, the continuous flow nitration reaction device has been regarded as an intrinsically safe nitration technology because of its small online volume, but it is also because of its small online volume that it cannot adjust the acid phase ratio online like the traditional kettle continuous reaction, so the continuous flow nitration reaction device has more stringent requirements on the feed ratio, and measures must be taken to accurately adjust the reaction ratio every time it is restarted after stopping, otherwise the ideal reaction result cannot be guaranteed.

[0004] The deep separation of the dispersed acid phase in the nitration product is not only related to the amount of reagents and washing water used in the nitration purification process, but also to how to achieve stable and uniform feeding of the buffered nitration product, and whether the subsequent continuous flow nitration device can accurately mix and operate stably.

[0005] At present, the common methods for removing the dispersed acid phase from the oil phase of the nitration product in production are: directly neutralizing the nitration product with an alkaline solution and then washing with water; adding water to the nitration to dilute the acid concentration in it and then stratify it twice, and then neutralizing and washing the nitration product oil layer. Both of these will bring about large wastewater treatment or waste acid evaporation costs.

[0006] In addition, there have been studies focusing on how to directly remove the dispersed acid phase from the nitration product. The relatively close nitrobenzene washing and separation methods, as well as the phase separators used for nitrobenzene dehydration, all use the coalescence filtration method to purify the crude oil phase of the nitrate. The coalescence filtration media include fiber filter elements, woven wire mesh disks, plate-shaped fillers, etc. The large specific surface area of ​​the filter material is used to make the dispersed acid-water phase condense into large-sized droplets on the surface of the material, promoting its stratification in the nitrate, thereby achieving a certain degree of purification of the nitration product. However, since this field needs to withstand the effects of aromatic nitrates and high-concentration sulfur-nitric acid mixtures, not only does it require higher chemical stability for the separation functional materials, but more importantly, the above method cannot guarantee the acquisition of clear and transparent homogeneous oil-phase nitrates.

[0007] Therefore, in the current production field of aromatic mixed acid nitration, there is an urgent need to solve how to deeply separate the dispersed acid phase directly from the mono- or poly-crude nitration products to obtain highly homogeneous, clear and transparent nitration products, thereby simplifying the production process and reducing the production consumption of reagents, water and steam, or making the output meet the more stringent supply and batching requirements in continuous flow multi-stage series nitration production, to ensure the continuous and stable reaction results and the flexible start and stop of the device. Summary of the invention

[0008] Purpose of the invention: The core technical problem to be solved by the present invention is to provide a method for deeply separating the dispersed acid phase in the aromatic nitration product, which is then used to solve the problem that the ingredients of the subsequent continuous flow nitration need to be more stable and accurate. The core method is to use a microporous filter element made of hydrophobic material, based on the lower tension of the nitrate, drive it to infiltrate inside the tissue of the hydrophobic microporous material, combine the accuracy of the filter material and the tension difference between the two phases, adjust the equipment operating parameters to match the material and medium properties, so that the oil phase and the hydrophobic microporous tissue together constitute a complete tension liquid membrane, and sustainable differential pressure filtration, so that the dispersed acid phase is always retained and enriched, and a homogeneous, clear and transparent nitrate oil phase is obtained.

[0009] Technical solution: The method for deeply separating the dispersed acid phase in the aromatic nitration product of the present invention refers to the method for deeply separating the dispersed phase acid liquid in the nitration product after the reaction of aromatic compounds with nitric and sulfuric acid mixed acid, which is characterized by using a hydrophobic microporous material as a support to construct a nitration oil phase tension liquid membrane, and performing sustainable differential pressure filtration by the following operation mode: (1) A filtration device is constructed using microporous materials with a surface energy lower than 33 mJ / m² as filter elements, and the filter elements are installed vertically, and a discharge space for the enriched acid phase is provided vertically below the filter elements to prevent the enriched acid phase after separation from flooding the filter surface of the filter element; (2) first adding 0-2%wt of water to the emulsified nitrate oil phase and mixing; wherein the addition of 0%wt of water is based on the condition that the density difference between the acid and oil phases in the emulsified nitrate oil phase is greater than 0.02 g / mL and the surface energy difference is greater than 2.5 mJ / m²; (3) Inject the emulsified nitrate oil phase into the filter device by means of high static pressure or positive displacement pump output pressure head and then soak for 0 to 8 minutes to allow the nitrate and the filter material microporous tissue to spontaneously infiltrate and construct a continuous oil phase tension liquid film, and then continue to inject the emulsified nitrate oil phase; (4) A regulating valve is provided at the outlet of the filtrate side of the filtration device, and the opening of the valve is changed to adjust the pressure difference on both sides of the tension liquid membrane, so that the nitrate is continuously filtered out from the microporous material, while the dispersed acid phase is retained and enriched and discharged from the discharge space in a controlled manner, thereby achieving deep separation of the dispersed acid phase in the aromatic nitration product to obtain a homogeneous oil phase, i.e., a purified product.

[0010] The discharged oil phase treated by the method of the present invention is not only clear and transparent, but also highly homogeneous; and the concentration of the residual acid can be reduced to a level close to the theoretical solubility. The method can simplify the process of the nitrated product and reduce consumption, and can also meet the more stringent stable supply and batching requirements of the continuous flow multi-stage series nitration device, and can also create conditions for the flexible start and stop of the device in this occasion.

[0011] Furthermore, in step (1) of the deep separation method of the present invention, the microporous material comprises polypropylene, polytetrafluoroethylene or graphite, the pore size is selected to be 50-700 nm, and the thickness of the microporous layer is 0.5-1.2 mm.

[0012] Furthermore, in steps (2) and (3) of the deep separation method of the present invention, the optional range of water addition adjustment and the controllable driving pressure together constitute the feed adjustment part, such as Figure 1 As shown in AA.

[0013] Furthermore, in step (3) of the deep separation method of the present invention, since the nitrate is a continuous phase and has a lower tension than the acid, it is driven to infiltrate the interior of the hydrophobic microporous material, while the acid phase cannot enter the microporous structure of the element, so that the nitrate forms a complete and sustainable oil phase tension liquid membrane supported by the microporous structure of the filter material.

[0014] Furthermore, in step (3) of the deep separation method of the present invention, the direction in which the nitrate is continuously filtered out of the microporous material is an external pressure filtration from the outside of the filter element to the inside, such as Figure 1 BB; or internal pressure filtration from inside the filter element to the outside, such as Figure 1 As shown in CC.

[0015] Furthermore, in step (4) of the deep separation method of the present invention, aromatic nitrates continue to seep out from the microporous material, and a homogeneous oil phase is obtained through the filtrate side discharge port. The content of sulfuric acid component in the clear and transparent homogeneous oil phase is 0.15-1.2‰, and the solubility of nitric acid in the homogeneous oil phase is much greater than that of sulfuric acid, and the content is more than 3.5 times that of sulfuric acid. At this time, the acid content in the homogeneous oil phase is reduced to close to the theoretical solubility, and the deep removal of the acid phase is achieved.

[0016] Furthermore, in step (4) of the deep separation method of the present invention, the dispersed acid phase cannot infiltrate the filter material and is always blocked by the oil phase and cannot pass through the material micropores, so it is retained on the raw material side to obtain an enriched acid phase; as the oil phase continuously seeps out, the retained and enriched acid phase eventually settles to the discharge space vertically below the filter element due to the difference in specific gravity, and is discharged from the discharge space in a controlled manner, so that the enriched acid phase does not overflow to the filter surface of the element.

[0017] Furthermore, in steps (3) and (4) of the deep separation method of the present invention, continuous feeding and adjustment of the filtrate flow rate and the pressure difference on both sides of the liquid membrane are performed to construct sustainable differential pressure filtration based on the oil phase tension liquid membrane.

[0018] Furthermore, in step (4) of the deep separation method of the present invention, the enriched acid phase can be discharged in an intermittent flow manner through the discharge port of the discharge space, or discharged together with the emulsified oil phase on the raw material side in a continuous flow manner, and returned to the feed port of the front-end oleic acid stratification device to merge with the reaction discharge, so that the retained enriched acid phase is incorporated into the main acid stratification.

[0019] Furthermore, in step (4) of the deep separation method of the present invention, the pressure difference value is 5-80 kPa.

[0020] Furthermore, the emulsified nitrated oil phase of the deep separation method of the present invention also includes a post-extraction emulsified oil phase formed by the nitrated product in the post-nitrated tail acid after the primary nitrated oil phase extraction, and a homogeneous post-extraction oil phase is obtained after steps (1) to (4), i.e., a purified post-extraction product.

[0021] The method for providing the purified product obtained by the above-mentioned deep separation method as a continuous flow high-order nitration ingredient comprises the following steps: (1) Place the purified product into a buffer container with a buffer time of 0.25 to 4 h; (2) The purified product after buffering and the nitric-sulfuric acid mixed acid are combined according to the set ratio and enter the pre-mixing device with partition heat exchange. The mixed discharge is controlled to be 40-85 °C and then directly enters the continuous flow reaction device.

[0022] The method for providing the purified product obtained by the above-mentioned deep separation method as a continuous flow high-order nitration ingredient comprises the following steps: (1) Place the purified extracted product into a buffer container with a buffer time of 0.25 to 4 hours; (2) After buffering, the purified extracted product and the nitric and sulfuric acid mixed acid are combined in a specified ratio and enter a pre-mixing device with partition heat exchange. The mixed discharge is controlled at 40-85 °C and then directly enters a continuous flow reaction device.

[0023] Furthermore, whether the above-mentioned homogeneous oil phase or homogeneous extracted oil phase is left static or transported at a variable flow rate, the composition of the material remains highly uniform, so the volume of the online buffer can be selected according to production needs, which can still ensure more accurate batching and freer start and shutdown operations for the subsequent continuous flow nitrification device.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the method constructs an oil phase tension liquid membrane of the nitrate, and then intercepts the dispersed acid phase by differential pressure filtration, so as to achieve deep separation of the oil and acid phases. The obtained oil phase is clear and transparent, with a lower residual acid concentration and high homogeneity; through separation by this method, the amount of neutralizing agent and water used in the neutralization and washing process of the aromatic nitration product can be greatly reduced; and for the production process of graded continuous nitration, continuous and accurate ingredients can be directly supplied for the subsequent reaction; and for the continuous flow nitration reaction device with a small online volume, it can not only meet its more stringent supply and ingredient requirements, but is also particularly conducive to the continuous, stable and flexible start and stop of the graded cascade reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The flowchart of the method of the present invention for separating the dispersed acid phase in the aromatic nitration product is shown in FIG. 1 ; wherein AA represents the feed adjustment part, BB represents the external pressure filtration method, and CC represents the internal pressure filtration method; and B or C, either of the two can be selected; Figure 2 A flow chart of the ingredients for the secondary nitration reaction after filtering the emulsified nitrated oil phase of the primary nitration product by the method of the present invention; Figure 3 A flow chart of using the method of the present invention to extract the primary nitration product oil phase, filter the post-extraction emulsified oil phase of the secondary nitration tail acid, and then provide the ingredients for the dinitration continuous reaction; Figure 4 The comparison of the appearance of the nitrobenzene emulsified oil phase before and after filtration using Example 1 of the present invention; wherein a is the appearance before filtration; c is the appearance after filtration; In the above figures, PL represents the emulsified nitrate oil phase, HW represents hot water, UFN represents the homogeneous oil phase, NDF represents the acid phase intermittent / continuous return to the material before stratification, NSA represents nitric and sulfuric acid mixed acid, NF represents the nitration reaction feed, and SA represents the dinitration tail acid; 1 is a high-level tank, 2 is a volume pump, 3 is a pressure instrument, 4 is a separation device, 5 is a filter element, 6 is a discharge space, 7 is a buffer tank, 8 is an oil phase batching pump, 9 is a temperature control mixer, and 10 is a temperature instrument; 11 is an extraction device; 12 is an oil phase buffer after extraction. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] The method for deep separation of dispersed acid phase in aromatic nitration products of the present invention uses controllable pressure such as high static pressure or output pressure head of a positive displacement pump as a driving force and is implemented in the following specific manner: (1) Add 0-2% of the total weight of water to the emulsified nitrate oil phase and mix well. If no water is added, the acid and oil phases in the emulsified nitrate oil phase must simultaneously meet the requirements of a density difference greater than 0.02 g / mL and a surface energy difference greater than 2.5 mJ / m²; (2) injecting the emulsified nitrate oil phase into a filter device of a specific configuration, wherein the filter element is made of a microporous material of a hydrophobic material, the surface energy of the element material is lower than 33 mJ / m², and the material includes but is not limited to polypropylene, polytetrafluoroethylene or graphite; the selected micropore diameter is 50-700 nm, and the microporous layer thickness is 0.5-1.2 mm; (3) Control the feed pressure and exhaust the gas in the filter device so that the surface of the filter element is completely in contact with the emulsified nitrate oil phase, and then soak for 0 to 8 minutes, making it easier for the nitrate to infiltrate the surface of the filter material, so that the nitrate and the microporous tissue of the filter material spontaneously build a complete continuous oil phase tension liquid film, and then continue to inject the emulsified nitrate oil phase; (4) A regulating valve is set at the outlet of the filtrate side. The permeate flow rate is changed by adjusting the valve opening and the pressure difference between the filtrate and the raw material is adjusted. The pressure difference value is preferably 5~80 kPa.

[0028] Specifically, the aromatic nitration product described in the present invention refers to the emulsified nitrated oil phase of the mixed dispersed acid phase obtained by layering and acid separation after the aromatic raw materials such as benzene, chlorobenzene, toluene and naphthalene react with nitric and sulfuric acid, and the oil and acid phases remain in liquid state. The mono- or poly-nitrated product is the continuous phase and the acid liquid is the dispersed phase. In the process of aromatic graded serial connection and continuous nitration, the emulsified nitrated oil phase of the present invention also includes the extracted emulsified oil phase obtained by extracting and separating the nitrated product in the nitrated tail acid of the post-stage nitration oil phase. After filtering and removing the acid by the present invention, a homogeneous oil phase or a homogeneous oil phase after extraction can be obtained.

[0029] Specifically, during the differential pressure filtration process constructed in steps (1) to (4), the filtration device can be operated in three ways at any time, including: interrupting the feed, resuming the feed after interruption, and briefly applying reverse pressure on the filtrate side to return part of the filtrate to the feed side. In any of the operation modes, the acid phase that has been retained and enriched will not diffuse to the filtrate side by itself.

[0030] Example 1 In Example 1, the deacidification of the monobasic nitration product of benzene is taken as an example. Benzene is subjected to a nitric-sulfur mixed acid reaction, and the mass ratio of the oil phase product in the discharge to the inorganic acid solution is 4:6, the residual nitric acid is 1.1% of the total discharge, and the sulfuric acid dehydration value DVS in the acid solution is 2.36. The material temperature is controlled in the range of 38-52 ° C for stratification, and the total acid value of the obtained emulsified nitration oil phase is 2.6-2.7% calculated as sulfuric acid. The removal of the specific dispersed acid phase is achieved according to the following steps: (1) Add 1.5%wt of water to the emulsified nitrate oil phase to adjust the surface energy difference between the acid phase and the nitrate to greater than 7 mJ / m²; (2) The microporous material is a graphite powder sintered loose hollow tube, and the filter element is an external pressure blind end filter structure, such as Figure 1 As shown in the middle BB part, the pore size of the micropores is 200-300 nm, and the thickness of the microporous layer is 1.2 mm; (3) The emulsified nitrate oil phase is injected into the filter device and the gas on the raw material side is discharged, so that the surface of the filter element is completely in contact with the emulsified nitrate oil phase and soaked for 2 minutes, and then the feed is continuously fed; (4) The permeate flow rate is changed by adjusting the valve opening and the pressure difference on both sides is adjusted. The pressure difference is preferably in the range of 20~25 kPa.

[0031] The homogeneous oil phase obtained through the filtrate side discharge port has a sulfuric acid content of 290 mg / L and a nitric acid content of 3.5‰. The separation results are shown in the attached figure. Figure 4 As shown; the dispersed acid phase is retained on the raw material side to obtain an enriched acid phase, and the proportion of nitric acid in the enriched acid phase reaches 90~93%.

[0032] Example 2 This Example 2 takes the deacidification of the mononitrogenous nitration product of chlorobenzene as an example. Chlorobenzene is subjected to a nitric-sulfur mixed acid reaction. The mass ratio of the oil phase product (a mixture of para- and ortho-nitrochlorobenzene) in the discharge to the inorganic acid solution is 9:10, the residual amount of nitric acid is 1.4% of the total mass of the discharge, and the sulfuric acid dehydration value DVS in the acid solution is 2.55. The material temperature is controlled in the range of 60-55°C for stratification, and the total acid value of the obtained emulsified nitration oil phase is 1.8-2.2% calculated as sulfuric acid. The specific removal of the dispersed acid phase is achieved according to the following steps, and the process is as follows: Figure 2 As shown: (1) The emulsified nitrate oil phase does not need to be adjusted with water. The density difference between the acid phase and the oil phase is greater than 0.35 g / ml, and the surface energy difference between the two phases is greater than 12 mJ / m². (2) The microporous material is preferably a loose polypropylene hollow tube, the element is an internal pressure cross-flow filtration structure, the pore size of the micropores is 250-450 nm, and the thickness of the microporous layer is 1.2 mm; (3) Inject the emulsified nitrate oil phase into the device and exhaust the gas on the raw material side, so that the surface of the filter medium is completely in contact with the emulsified oil phase and soaked for 4 minutes, and then continue to feed; (4) The permeate flow rate is changed by adjusting the valve opening and the pressure difference on both sides is adjusted. The pressure difference is preferably in the range of 40~55 kPa.

[0033] In the homogeneous oil phase obtained through the filtrate side discharge port, the content of sulfuric acid component is 340 mg / L, and the content of nitric acid is 1.4‰; the dispersed acid phase is retained on the raw material side to obtain an enriched acid phase, and the nitric acid in the enriched acid phase accounts for 69~75%; the obtained homogeneous oil phase first enters a container with a buffer time of 0.25~4 h, and then realizes the controlled feeding of secondary nitration raw materials through a flow regulating facility; after the two streams of oil phase and nitric-sulfur mixed acid phase are combined according to the reaction ratio, they continuously pass through a pre-mixing device that can exchange heat between walls to control the temperature of the mixed material to 40~85 ℃, and then continuously and stably enter the subsequent reaction device.

[0034] Example 3 This Example 3 takes the deacidification of the monobasic nitration product in the two-stage series nitration process of benzene as an example. The primary nitration product comes from the secondary sulfuric acid dosage reaction. The mass ratio of the emulsified nitrate oil phase to the inorganic acid liquid in the discharge is 1:2, the residual nitric acid is 1.1% of the total discharge, and the sulfuric acid dehydration value DVS in the acid liquid is 4.55. The material temperature is controlled in the range of 45~52°C for stratification, and the total acid value of the obtained emulsified nitrate oil phase is 2.5~2.7% calculated as sulfuric acid. The crude nitrobenzene is used to extract the secondary nitration tail acid with DVS=6.57, and the discharge temperature of the extracted oil phase is controlled to 71~75°C to obtain an extracted emulsified oil phase with dinitrobenzene extracted, which contains 4.8~5.3% acid liquid. The specific removal of the dispersed acid phase is achieved according to the following steps, and the process is as follows Figure 3 As shown: (1) After extraction, the emulsified oil phase does not need to be adjusted by adding water. The density difference between the acid phase and the oil phase is greater than 0.4 g / ml, and the surface energy difference between the two phases is greater than 10 mJ / m²; (2) The microporous material is preferably a porous polytetrafluoroethylene hollow tube, the element is a structure of external pressure blind end filtration, the pore size of the micropore is 300~750nm, and the thickness of the microporous layer is 0.9mm; (3) After extraction, the emulsified oil phase is injected into the device and the gas on the raw material side is discharged, so that the surface of the filter medium is completely in contact with the emulsified oil phase and soaked for 8 minutes, and then the feed is continuously fed; (4) The permeate flow rate is changed by adjusting the valve opening and the pressure difference on both sides is adjusted. The pressure difference is preferably in the range of 20~30 kPa.

[0035] In the homogeneous extracted oil phase obtained through the filtrate side discharge port, the content of sulfuric acid component is 670 mg / L, and the content of nitric acid is 1.6‰; the dispersed acid phase is retained on the raw material side to obtain an enriched acid phase, and the nitric acid in the enriched acid phase accounts for 50-55%; the obtained homogeneous oil phase first enters a container with a buffer time of 0.25-4 h, and then realizes the controlled feeding of secondary nitration raw materials through a flow regulating facility; after the two streams of oil phase and nitric-sulfur mixed acid phase are combined according to the reaction ratio, they continuously pass through a pre-mixing device that can exchange heat between walls to control the temperature of the mixed material to 40-85 ℃, and then continuously and stably enter the subsequent reaction device; the reaction device of this stage after the pre-mixing device only adjusts the reaction discharge temperature online, and there is no need to set up online adjustment facilities for the nitric acid ratio.

Claims

1. A method for deep separation of aromatic nitration products, particularly a method for deep separation of the dispersed phase acid liquid of the nitration products obtained by the reaction of aromatic compounds with nitric and sulfuric acid mixed acid by isolating and layering the acid to obtain an emulsified nitration oil phase of mono- or poly-nitration products, wherein the nitration products are continuous phases, It is characterized in that The hydrophobic microporous material is used as a support to construct the nitrate oil phase tension liquid membrane, and sustainable differential pressure filtration is performed through the following operation methods: (1) A filtration device is constructed using microporous materials with a surface energy lower than 33 mJ / m² as filter elements, and the filter elements are installed vertically, and a discharge space for the enriched acid phase is provided vertically below the filter elements to prevent the enriched acid phase after separation from flooding the filter surface of the filter element; (2) first adding 0-2%wt of water to the emulsified nitrate oil phase and mixing; wherein the addition of 0%wt of water is based on the condition that the density difference between the acid and oil phases in the emulsified nitrate oil phase is greater than 0.02 g / mL and the surface energy difference is greater than 2.5 mJ / m²; (3) Inject the emulsified nitrate oil phase into the filter device by means of high static pressure or positive displacement pump output pressure head and then soak for 0 to 8 minutes to allow the nitrate and the filter material microporous tissue to spontaneously infiltrate and construct a continuous oil phase tension liquid film, and then continue to inject the emulsified nitrate oil phase; (4) A regulating valve is provided at the outlet of the filtrate side of the filtration device, and the opening of the valve is changed to adjust the pressure difference on both sides of the tension liquid membrane, so that the nitrate is continuously filtered out from the microporous material, while the dispersed acid phase is retained and enriched and discharged from the discharge space in a controlled manner, thereby achieving deep separation of the dispersed acid phase in the aromatic nitration product to obtain a homogeneous oil phase, i.e., a purified product.

2. The method for deep separation of aromatic nitration products according to claim 1, It is characterized in that In step (1), the microporous material includes polypropylene, polytetrafluoroethylene or graphite, the pore size is 50-700 nm, and the thickness of the microporous layer is 0.5-1.2 mm.

3. The method for deep separation of aromatic nitration products according to claim 1, It is characterized in that In step (3), the direction in which the nitrate is continuously filtered out of the microporous material is external pressure filtration from the outside of the filter element to the inside, or internal pressure filtration from the inside of the filter element to the outside.

4. The method for deep separation of aromatic nitration products according to claim 1, It is characterized in that In step (3), the enriched acid phase is discharged from the discharge space in a controlled manner, including being discharged in an intermittent flow manner or being discharged in a continuous flow manner.

5. The method for deep separation of aromatic nitration products according to claim 1, It is characterized in that In step (4), the pressure difference between the two sides of the tension liquid film is 5-80 kPa.

6. The method for deep separation of aromatic nitration products according to claim 1, It is characterized in that The emulsified nitrated oil phase also includes a post-extraction emulsified oil phase formed by nitrates in the post-stage nitrated tail acid after the primary nitrated oil phase extraction, and a homogeneous post-extraction oil phase is obtained after steps (1) to (4), i.e., a purified post-extraction product.

7. A method for purifying products for continuous flow high-order nitration ingredients, It is characterized in that The purified product is obtained by the deep separation method according to claim 1, comprising the following steps: (1) Place the purified product into a buffer container with a buffer time of 0.25 to 4 h; (2) The purified product after buffering and the nitric-sulfuric acid mixed acid are combined according to the set ratio and enter the pre-mixing device with partition heat exchange. The mixed discharge is controlled to be 40-85 °C and then directly enters the continuous flow reaction device.

8. A method for purifying products for continuous flow high-order nitration ingredients, It is characterized in that The purified product is a purified extracted product obtained by the deep separation method according to claim 6, comprising the following steps: (1) Place the purified extracted product into a buffer container with a buffer time of 0.25 to 4 hours; (2) After buffering, the purified extracted product and the nitric and sulfuric acid mixed acid are combined in a specified ratio and enter a pre-mixing device with partition heat exchange. The mixed discharge is controlled at 40-85 °C and then directly enters a continuous flow reaction device.

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