Systems and methods for preparing mononitrobenzene trifluoride (NBTF)

Abstract

The invention discloses a system for continuously manufacturing mononitro benzene trifluoride (NBTF). The system is provided with a mononitro benzene trifluoride first reactor which enables the conversion rate of reactants in the reaction to be 90-98%; designing a mononitro benzene trifluoride second reactor for completing 2%-10% of the reaction conversion rate of the residual reactants; and the third reactor can be used for separating an organic layer containing nitrobenzene trifluoride from a water layer containing mixed sulfuric acid. The system further comprises a washing device which is used for washing the organic layer and separating 4-nitrobenzene trifluoride (4-NBTF), 2-nitrobenzene trifluoride (2-NBTF) and 3-nitrobenzene trifluoride (3-NBTF) according to a specific proportion. The system enables high yield, non-corrosive, fast, compact, cheaper and economically viable NBTF production by mononitration and implements reusable recovery of waste acid during the process to achieve environmental and cost benefits.

Description

[0001] Cross-references to related applications and priorities

[0002] This application claims priority to Indian Patent Application No. 202221028001 filed on May 16, 2022, which is incorporated herein by reference. Technical Field

[0003] The subject matter described herein generally relates to systems and methods for producing mononitrobenzene trifluoride (NBTF). Specifically, the present invention relates to improved continuous methods and systems for producing 3-nitrobenzene trifluoride, 2-nitrobenzene trifluoride, and 4-nitrobenzene trifluoride. Background Art

[0004] The nitration process of benzene trifluoride is conventional and well known and has been practiced commercially for many years to produce mononitro compounds or generally to produce nitro species. The nitro species produced are in turn used to produce the corresponding amino compounds. Typically, the manufacture of the nitro species involves adding nitric acid in batches, stepwise or continuously to a mixture of sulfuric acid and benzene trifluoride, or adding the nitration mixture to benzene trifluoride.

[0005] Because the acid phase and the organic phase are miscible, the reaction rate and reaction efficiency between the phases are largely limited by mass transfer; that is, by exposing the large interfacial area of ​​each phase to each other. As the interfacial area increases, the reaction rate between the phases increases. In traditional large-scale production facilities of nitro substances, these interfacial regions are usually generated by applying high shear forces to the liquid in one or more stirred vessels to react the two phases. In the 6th edition of Chemical Engineering Handbook (Perry), several methods for achieving close mixing or contact between liquids are proposed, including, for example, online static mixers, mechanical stirring, gas stirring, jet mixers, ejectors, orifice mixers, and nozzle mixers.

[0006] Another problem that generally occurs in the mononitration of benzene trifluoride is the formation of high levels of hydrofluoric acid (HF) or liquid hydrogen fluoride. As is known in the art, the high corrosiveness of HF reduces the service life of the reaction units involved.

[0007] In case of batch processes, the problem of large amount of HF formation is usually observed. In addition, the batch reaction for the production of NBTF leads to a large and prolonged time to increase the yield and achieve the maximum conversion of the raw materials. In addition, in order to carry out the batch reaction, it is necessary to utilize a reactor with a large space area.

[0008] None of the above methods for achieving large contact interfacial areas between immiscible solution phases is completely satisfactory, and no method other than mechanical stirring has been used commercially to any extent for the manufacture of mononitro compounds. These methods either require high capital costs due to long duration, high maintenance costs, high power requirements (as in the case of stirred vessels), or are difficult to control for optimal reaction efficiency (as in the case of impinging flow or jets).

[0009] Therefore, there has long been a need to design a production system and process that can produce NBTF by mononitration in a high yield, non-corrosive, rapid, compact, cheaper and economically viable manner. In addition, there has long been a need to implement reusable waste acid recovery in the process to achieve environmental and cost benefits. Summary of the invention

[0010] Purpose of the Invention

[0011] The object of the present invention is to provide a compact system for large-scale production of mononitrobenzene trifluoride in a flash mode achieving higher productivity in a smaller plant.

[0012] It is an object of the present invention to provide a process for the reliable and high-yield production of mononitrobenzene trifluoride which eliminates or mitigates the known disadvantages of the prior art processes.

[0013] The object of the present invention is to provide a method for producing mononitrobenzene trifluoride in a safe and environmentally friendly manner.

[0014] The object of the present invention is to provide a continuous process for producing mononitrobenzene trifluoride.

[0015] Technical Solution

[0016] This technical solution is intended to introduce concepts related to the system and preparation method of mononitrobenzene trifluoride (NBTF). This technical solution is neither intended to identify the essential features of the subject matter claimed by the present invention, nor is it intended to be used to determine or limit the scope of the subject matter disclosed by the present invention.

[0017] In one embodiment, the present invention discloses a system for the continuous production of mononitrobenzene trifluoride (NBTF). The system may include a first reactor for mononitration of benzene trifluoride with a reaction conversion rate of 90% to 98% of the reactants comprising BTF, H2SO4 and nitric acid. The system may also include a second reactor for mononitration of benzene trifluoride to complete the remaining 2% to 10% reaction conversion rate of the reactants. The system may also include a third reactor capable of separating the spent acid and the organic layer comprising nitrobenzene trifluoride by adding water to maintain the desired strength of the spent acid. In one embodiment, the reaction produces a spent acid of 84% to 85% strength in the nitro species, which is diluted to 72% when the layer separates the spent acid for recycling and reuse of other members of the same family of benzene trifluoride.

[0018] The system may further include a washing unit for washing the organic layer and separating 4-nitrobenzenetrifluoride (4-NBTF), 2-nitrobenzenetrifluoride (2-NBTF), and 3-nitrobenzenetrifluoride (3-NBTF) at a specific percentage.

[0019] In certain embodiments, the first reactor may include a modified agitator, a plurality of turbine blades, a vortex breakup device configured for proper and uniform mixing of the reactants, one or more internal baffles, internal cooling brine coils, a cooling jacket, and an overflow outlet including a cleat capable of transferring the reactants from the first reactor to the second reactor.

[0020] In another embodiment, the present invention discloses a method for continuously synthesizing mononitrobenzene trifluoride (NBTF). The method may include the step of adding a predetermined molar ratio of benzene trifluoride (BTF) and 98% sulfuric acid (H2SO4) in a first reactor. The method may also include the step (403) of adding a predetermined molar ratio of a nitrating agent such as strong nitric acid (HNO3) after cooling the first reactor (105) to a temperature range of 5-10°C. The method may also include the step of determining that the level of the reaction mixture in the first reactor reaches an overflow level, so that 98% sulfuric acid (H2SO4), strong nitric acid (HNO3) and benzene trifluoride (BTF) can be added simultaneously in the first reactor. The method may also include the step of maintaining the above reaction at a predetermined flow rate for about 45 minutes to 90 minutes to obtain a nitro substance of a mixture containing mononitrobenzene trifluoride (NBTF). The inlet and outlet flow rates of the second reactor are optimized, and the residence time is 45 minutes to 2 hours. The method may also include the step of transferring the nitro substance obtained in the second reactor to a third reactor for layer separation into an aqueous layer and an organic layer. Furthermore, the method may include the step of transferring the organic layer separated in the third reactor to a washing and distillation unit to obtain a specific ratio of 3-nitrobenzenetrifluoride (3-NBTF), 2-nitrobenzenetrifluoride (2-NBTF) and 4-nitrobenzenetrifluoride (4-NBTF).

[0021] List of abbreviations

[0022] BTF-Benzene trifluoride

[0023] NBTF-Mononitrobenzene trifluoride

[0024] 4-NBTF-4-Nitrobenzene trifluoride

[0025] 2-NBTF-2-Nitrobenzene trifluoride

[0026] 3-NBTF-3-Nitrobenzene trifluoride

[0027] Mixed acid - a mixture of nitric acid and sulfuric acid used for nitration BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specification of the present invention is described in detail with reference to the accompanying drawings. In the accompanying drawings, the leftmost digit of a reference number identifies the drawing in which the reference number first appears. The same numerals are used throughout the drawings to represent the same features and components.

[0029] Figure 1 A system (100) for the continuous production of mononitrobenzene trifluoride (NBTF) according to an embodiment of the present inventive subject matter is described.

[0030] Figure 2A first reactor (105) capable of performing the mononitration of trifluorinated benzene at 90% to 98% reaction conversion of the reactants according to an embodiment of the present subject matter is described.

[0031] Figure 3 A second reactor (106) configured for the mononitration of benzene trifluoride to complete the remaining 2% to 10% reaction conversion of the reactants is described.

[0032] Figure 4 A method (400) for the continuous synthesis of mononitrobenzene trifluoride (NBTF) according to an embodiment of the present invention is described. DETAILED DESCRIPTION

[0033] The description of "various embodiments", "some embodiments", "one embodiment" or "an embodiment" throughout the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment. Therefore, the phrases "in various embodiments", "in some embodiments", and "in one embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics can be combined in any suitable manner in one or more embodiments.

[0034] The words "comprising," "having," "containing," and "including" and other forms thereof are intended to be equivalent in meaning and to be open-ended, in that one or more items following any of these words is not intended to be an exhaustive list of such one or more items, or to be limited to only the listed one or more items.

[0035] It must also be noted that the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Although any methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, exemplary methods are described. The disclosed embodiments are merely examples of the present disclosure, which can be embodied in various forms.

[0036] Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles herein may be applied to other embodiments. However, it will be readily appreciated by those skilled in the art that the present disclosure is not intended to be limited to the embodiments shown, but should be given the widest scope consistent with the principles and features described herein. The present invention will be described in detail below with reference to the accompanying drawings.

[0037] In one embodiment of the present invention, reference Figure 1 and 4, discloses a system (100) and a method (400) for preparing mononitrobenzene trifluoride (NBTF). In one embodiment, the system (100) includes a plurality of continuous stirred tank reactors. The continuous stirred tank reactors of the system (100) can be connected in series, cascade or pressure reduction, but are not limited to.

[0038] In one embodiment, reference Figure 1 and 2 , a system (100) for continuously producing mononitrobenzene trifluoride (NBTF) is disclosed herein. The system may include a first reactor (105) for mononitrifying benzene trifluoride with a reaction conversion rate of 90-98% of the reactants. The system (100) may also include a second reactor (106) for mononitrifying benzene trifluoride to complete the remaining 2% to 10% reaction conversion rate of the reactants.

[0039] In another embodiment, the system (100) may further include a third reactor (107) capable of water treating the nitro substance to separate an aqueous layer containing waste acid and an organic layer containing nitrobenzene trifluoride. The system may further include a device for washing the organic layer and separating 4-nitrobenzene trifluoride (4-NBTF), 2-nitrobenzene trifluoride (2-NBTF), and 3-nitrobenzene trifluoride (3-NBTF) at a specific percentage. In a related embodiment, the washing device (108) may also transfer 4-nitrobenzene trifluoride (4-NBTF), 2-nitrobenzene trifluoride (2-NBTF), and 3-nitrobenzene trifluoride (3-NBTF) to a distillation device (not shown in the figure).

[0040] The effluent obtained from the washing unit (108) may be further treated for acidic / alkaline effluent aqueous layer separation. The effluent is then transferred to an effluent treatment plant (not shown).

[0041] In one embodiment, the system (100) can be used to feed benzene trifluoride (BTF) from a BTF feed tank (101). In one embodiment, the benzene trifluoride used can be obtained from any convenient source. In one embodiment, benzene trifluoride can be obtained by reacting benzene with other chlorine components and fluorine components.

[0042] In one embodiment, the system (100) can be used to feed the nitrating agent from the nitrating agent feed tank (104). In a certain embodiment, the nitrating agent feed tank (104) is capable of feeding strong nitric acid (72%) and 98% sulfuric acid to the first reactor (105).

[0043] In one embodiment, the nitric acid used in the method of the present invention is selected from 72% nitric acid and 98% nitric acid, which are strong acids. The 72% / 98% nitric acid is 1.0 to 1.10 times, preferably 1.05 to 1.15 times, the theoretical amount of nitric acid required to nitrate all the trifluorinated benzenes present to mononitro trifluorinated benzenes. It has been found that when the amount of nitric acid used in the continuous process is greater than 1.15 times the theoretical value, the content of by-product waste acid containing more nitric acid increases sharply; and when the amount of nitric acid used is less than 1.00 times the theoretical value, the amount of unreacted trifluorinated benzene increases.

[0044] In one embodiment, the system (100) can be used to feed sulfuric acid (H2SO4) from a H2SO4 feed tank (102). The H2SO4 feed tank (102) is capable of feeding 98% H2SO4 to the first reactor (105).

[0045] In one embodiment, the concentrations of sulfuric acid and nitric acid can be selected so that the reaction can be carried out at a relatively low temperature and without superatmospheric pressure. The content of sulfuric acid and spent acid added to the reaction in the first reactor (105) is 22-24.0% nitric acid (72%) and 74-77% sulfuric acid (98%).

[0046] In an alternative embodiment, spent acid having 22.0-24.0% nitric acid (72%) and 74-77% sulfuric acid (98%) may also be introduced into the first reactor (105).

[0047] In addition, the ratio of nitric acid and sulfuric acid can be selected so that the nitric acid is preferably at a low concentration and substantially completely dissociated into nitroxyl cations, and benzene trifluoride is mixed with the nitroxyl cation solution to provide a fine emulsion, whereby the reaction can be carried out at low temperature and atmospheric pressure to reduce the residence time within the first reactor (105), thereby providing a NBTF product with no or low levels of impurities.

[0048]

[0049] Reference Figure 2 In one embodiment, the first reactor (105) may include an improved agitator (204) having one or more turbine blades (205), and a vortex breaking device (208) configured to properly and uniformly mix the reactants. Since the NBTF preparation of the present disclosure is achieved by controlling the mass transfer of the reaction, a well-designed agitator blade (205) is introduced into the first reactor (105) for high shear stirring. Figure 2a , Figure 2a is a top view of the first reactor (105) depicting the position of one or more baffles (206) relative to the agitator (204).

[0050] Moreover, in order to avoid eddy currents, one or more baffles (206) are provided in the first reactor (105). The width and thickness of the baffles are adjusted so as to break the eddy currents generated by stirring to ensure adequate mixing. In one embodiment, the residence time is maintained between 60 minutes and 90 minutes to achieve a conversion rate of 90% to 98%. In one embodiment, the first reactor (105) may further include an overflow outlet (209) having a fixture (210), which is capable of controlling the transfer of the reaction material without siphoning the reaction material from the first reactor (105) to the second reactor (106).

[0051] In one embodiment, the second reactor (106) can be configured to receive and collect overflow of the reaction mass from the first reactor (106). The remaining 2% to 10% of the reaction can be carried out in the second reactor (106) with a residence time of 45 minutes to 60 minutes. In one embodiment, the second reactor (106) can be configured to maintain stirring of the reaction mass under high shear to achieve a conversion of up to 100% of the reaction mass within a predetermined time, thereby reducing the reaction time.

[0052] In one embodiment, the second reactor (106) may include an inlet (301) to receive and collect overflow of the reaction material from the first reactor (105). The second reactor (106) may also include a simple agitator unit (302) having one or more blades (303), the blades being selected from any one of a propeller blade, a turbine blade or a paddle blade. The second reactor (106) may also include a controlled cooling mechanism having a jacket brine cooling (304) and a single internal cooling coil (305). The second reactor (106) may also include a plurality of baffles (306) at the inner edge of the reactor. In a certain embodiment, the outlet (307) at the bottom of the second reactor (106) is configured to transfer the nitro substance to the third reactor (separator) (107).

[0053] In one embodiment, the outlet (307) at the bottom of the second reactor (106) is configured to transfer the nitro species to the third reactor (separator) (107).

[0054] In one embodiment, the first reactor (105) and the second reactor (106) may include a scrubber exhaust port (not shown) to scrub the acid mist from the reactor.

[0055] In one embodiment, the reactor involved in the preparation of NBTF may be a continuous stirred tank reactor. In another embodiment, various raw materials are fed with desired flow rates by metering pumps. Since the reaction is highly exothermic, it is controlled by allowing a lower temperature brine of water and methanol to circulate in the cooling brine jacket (207), (304) and internal cooling coils (211) and (305).

[0056] In one embodiment, the first reactor (105) may include dual internal cooling coils (211) and a cooling brine jacket (207), and the second reactor (106) may include a single internal cooling coil (305) and a cooling brine jacket (207).

[0057] It should be noted here that: in conventional methods, the reaction temperature is not optimized, and often causes the reaction mass in the first reactor to freeze, because the temperature supply used is too low (-10°C), which further causes the overflow line to be blocked. Therefore, in order to overcome this problem, in the present invention, the temperature of the first reactor and the second reactor is maintained between 1°C and 12°C, preferably between 4-9°C, by adjusting the combination of the jacket and the internal circulation cooling brine under predetermined temperature and pressure conditions.

[0058] In one embodiment, if Figure 1 As shown, the system (100) may include a BTF and H2SO4 mixing chamber (103). The mixing chamber (103) is configured to add a premix of BTF and H2SO4 to the first reactor (105). In one embodiment, BTF and H2SO4 from the BTF feed tank (101) and the H2SO4 feed tank (102), respectively, are added to the first reactor (105) before adding nitric acid from the feed tank (104).

[0059] In one embodiment, if Figure 2 As shown, the first reactor (105) may include one or more reactant inlets, for example, 72% (or 98%) nitric acid inlet (201), nitrobenzene trifluoride inlet (202) and 98% sulfuric acid inlet (203). All reactants are fed into the first reactor using respective reactant inlets (201), (202) and (203). In one embodiment, the flow rate of the raw materials of each component of trifluorinated benzene, nitric acid and sulfuric acid is controlled by adjusting the operating rate of the metering pump, so that the reactants are transported to the reaction chamber of the first reactor (105) in a stoichiometric ratio of trifluorinated benzene, and the reaction temperature is kept below 5°C to 7°C. 90-98% conversion of the main reactants is carried out in the first reactor (105).

[0060] In another embodiment, a process (400) for the continuous synthesis of mononitrobenzene trifluoride (NBTF) is disclosed. It will be appreciated that the present invention involves introducing a mixed reactant stream of sulfuric acid and benzene trifluoride containing about 25-28% sulfuric acid and 13-16% nitric acid.

[0061] The method (400) may include a plurality of steps. The method (400) may include the step of adding (401) a predetermined molar ratio of benzene trifluoride (BTF) and 98% sulfuric acid (H2SO4) in the first reactor (105). The method (400) may include the step of adding (402) a predetermined molar ratio of a nitrating agent such as strong nitric acid (HNO3) after cooling the first reactor (105) to a temperature range of 5 to 10°C. The temperature of 5-10°C is maintained by combining jacket cooling and internal circulating brine cooling. The concentration of nitric acid in the strong nitric acid (HNO3) is between 72% and 98%.

[0062] The method (400) may include the step of determining (403) that the level of the reaction mixture in the first reactor (105) reaches an overflow level of about 85% of the first reactor, thereby enabling simultaneous addition of 98% sulfuric acid, 72% nitric acid (HNO3) / 72% nitric acid, and benzene trifluoride (BTF) in the first reactor. In one embodiment, in step (403), benzene trifluoride, 98% sulfuric acid, and 72% nitric acid / 98% nitric acid are continuously fed into the first reactor (105) through the corresponding feed tanks (101, 102, 103, 104).

[0063] In one embodiment, in step (403), benzene trifluoride, 98% sulfuric acid and 98% nitric acid are continuously fed into the first reactor (105) through corresponding feed tanks (101, 102, 103, 104), wherein the molar ratio of BTF:98% H2SO4:98% HNO3 is 1:1.01:1.02 to 1:1.1:1.05.

[0064] In one embodiment, in step (403), benzene trifluoride, 98% sulfuric acid and 72% nitric acid are continuously fed into the first reactor (105) through corresponding feed tanks (101, 102, 103, 104), wherein the molar ratio of BTF:98% H2SO4:72% HNO3 is 1:2.08:1.02 to 1:2.08:1.05.

[0065] In one embodiment, a complete emulsification state of the entire mixture is produced in the first reactor (105) by the stirring system disclosed herein. In one embodiment, the step of determining (403) that the level of the reaction mixture in the first reactor (105) reaches the overflow level enables a short residence time (60 to 80 minutes) of the reaction mixture to obtain the nitro species of the mixture containing mononitrobenzene trifluoride (NBTF). A conversion rate of 90% to 98% of the main reactant is achieved in the first reactor (105).

[0066] In one embodiment, the method (400) may include the further step of maintaining (404) the reaction at a predetermined flow rate for about 45 to 90 minutes and continuously discharging the reaction mixture into a second reactor in which the remaining 2% to 10% of the reaction is near completion. In one embodiment, the method (400) optimizes (405) the inlet and outlet flow rates of the second reactor (106) to achieve a residence time of 45 minutes to 2 hours.

[0067] In an alternative embodiment, the process of the invention may be reversed, ie, the trifluorinated benzene may be delivered to a mixed acid stream or body. It will also be appreciated that the process will be applicable to other nitrations or other chemical reactions where mass transfer is limited.

[0068] The method (400) may include the step of passing the nitro species obtained in the second reactor (106) through a third reactor (107) (hereinafter alternatively referred to as a "separation reactor") to separate the spent acid and the organic layer. In this step, the organic layer containing the nitro species and the spent acid are transferred to the separation reactor (107), which is configured to dilute the mixture of organic products 3-nitrobenzene trifluoride, 2-nitrobenzene trifluoride and 4-nitrobenzene trifluoride, and separate it from the spent acid by adding water to a degree that the spent acid concentration is maintained at 84-85% to about 72%-75%, and the spent acid is circulated and reused in the nitration reaction to produce other members of the trifluorinated benzene family.

[0069] The mixture of organic products containing nitro substances is then separated from the waste acid layer. The collected nitro substances are further subjected to reaction treatment and finally sent to a fractionation tower to receive pure compound 1 and compounds 2 and 3, namely 3-nitrobenzene trifluoride, 2-nitrobenzene trifluoride, and 4-nitrobenzene trifluoride.

[0070] In step (406), the waste mixed acid separated from the organic layer of the mixture of organic products containing nitro substances can be recycled and reused. In this improved method, the reaction is carried out at normal pressure, and the waste acid contains 1.0-1.5% nitric acid and 72.0-75.0% sulfuric acid.

[0071] The method (400) may include passing the organic layer (407) separated in the third reactor through a washing and distillation unit to obtain a specific percentage of pure 3-nitrobenzenetrifluoride (3-NBTF), 2-nitrobenzenetrifluoride (2-NBTF) and 4-nitrobenzenetrifluoride (4-NBTF).

[0072] In fact, the mononitrobenzene trifluoride compound can be separated by performing a distillation process. The separation of isomers such as 3-nitrobenzene trifluoride, 2-nitrobenzene trifluoride, and 4-nitrobenzene trifluoride into various fractions is performed in a distillation column by adding some additives to reduce the risk of distillation. In one embodiment, the maximum total yield of the desired 3-nitroBTF product is as high as 89-91%, the 2-nitroBTF product is as high as 7-8%, and the 4-nitroBTF product is as high as 2-2.5%.

[0073] Example

[0074] The present invention is further described by the following examples:

[0075] Experiment details:

[0076] Example 1: Production of mononitrobenzene trifluoride (NBTF) in single reactor batch mode

[0077] In this example, a predetermined amount of benzene trifluoride from a BTF feed tank was added to the reactor, and a predetermined amount of 98% H2SO4 was charged into the reactor. 72% nitric acid / 98% nitric acid was then added continuously, maintaining the reaction temperature at 4-7°C. The agitator RPM speed was maintained between 350 and 450. The residence time in the first reactor was maintained at 45 to 75 minutes to achieve maximum conversion of the BTF reactant. The observed results of the batch reaction are shown in Table 1 below.

[0078] Table 1

[0079]

[0080] As can be seen from Table 1, for a total residence time of 75 minutes, the yield of 3-nitroBTF was obtained in the range of 89 to 89.9%, and about 0.8% of nitric acid remained in the waste liquid. In addition, in the case of a single reactor, many reaction and safety related problems were observed, such as: freezing of the reaction mass, formation of a high level of HF content and inconsistent conversion rate. Therefore, the reaction mode was changed to a continuous mode, and its advantages and technical effects are explained in the following examples.

[0081] Example 2a: Production of mononitrobenzene trifluoride (NBTF) using 72% nitric acid in continuous mode

[0082] In this example, a predetermined amount of BTF from a BTF feed tank at a flow rate of 35-45 kg / hour is mixed with a predetermined amount of 98% H2SO4 at a flow rate of 72.8-94 kg / hour. The mixture is added to a 100-liter first continuously stirred tank reactor comprising at least two baffles, a vortex breaker at the bottom, and an agitator with 3 turbine blades and a modified overflow line including an open / close clamp component. The agitator RPM speed is maintained at 550-600. After a predetermined period of time, a predetermined amount of 72% nitric acid is fed to the first reactor at a flow rate of 22.3-30 kg / hour, wherein the molar ratio of BTF:98% H2SO4:72% HNO3 is 1:2.08:1.02 to 1:2.08:1.10. When the overflow limit set in the first reactor is reached, all three reactants are added simultaneously. The reaction mass is transferred to the second reactor to maintain the overflow limit, siphoning of the reaction mass, and maximum conversion of the reaction mass. After the second reactor reaches a certain level, the bottom valve and the circulation line valve of the second reactor are opened. The agitator RPM speed is maintained at 100-150. The residence time in the first reactor is maintained at 60-90 minutes, and the residence time in the 250L second reactor is maintained at 300-320 minutes. The temperature of the first reactor is maintained at 5-7°C by the internal circulation of the jacket and the chilled brine. After a predetermined time of 300-320 minutes, the transfer valve is opened to transfer the nitro material from the second reactor to the separation reactor for dilution and separation process. When transferred to the separator, the sample from the overflow line is analyzed: BTF ~ 0.1% to 0.8%, 3-NBTF ~ 88.5% to 89.5% in the nitro material, and HNO3 ~ 1.0% to 1.4% in the spent acid. A predetermined amount of water is added to the separator for dilution and stirring for 30 minutes. A water layer containing spent acid %H2SO4 ~ 72% to 73%, %HNO3 ~ 0.8% to 1.2% and an organic layer containing nitro species with NBTF 88.5% to 89.5% was observed. In the next stage, stirring was stopped and the settled material was separated after 30 minutes and the organic sample was analyzed to observe %BTF ~ 0.01% to 0.02%, 3-NBTF ~ 89.5% to 89.9% in nitro species. In this example, the total conversion of the reactants in the continuous reactor mode was achieved in the first reactor of about 92% and the remaining conversion up to 8% was achieved in the second reactor. The nitro species was further transferred for distillation.

[0083] The mass yields of nitro groups obtained from the first and second reactors are disclosed in Table 2a below:

[0084] Table 2a

[0085]

[0086] Referring to Table 2b, the total residence time in the second reactor was 60-90 minutes and 300-320 minutes, and the yield of 3-nitroBTF was 89-89.9%, and about 1.0-1.5% of nitric acid remained in the waste liquid. In addition, in the case of the dual reactor mode, the HF content was reduced to 5-10 ppm. In addition, safety-related problems such as flow fluctuations, freezing of the reaction mass and blockage of the overflow line, inconsistent flow, siphoning of the overflow line and sudden flow were eliminated. In addition, the maximum conversion of the reactants was observed.

[0087] Example 2b: Production of mononitrobenzene trifluoride (NBTF) using 98% nitric acid in continuous mode

[0088] In this example, a predetermined amount of BTF from a BTF feed tank at a flow rate of 60 kg / hour was mixed with a predetermined amount of 98% H2SO4 at a flow rate of 66 kg / hour. The mixture was added to a 100-liter first continuously stirred tank reactor comprising at least two baffles, a vortex breaker at the bottom, and an agitator with 3 turbine blades and a modified overflow line. After a predetermined period of time, a predetermined amount of 98% nitric acid was fed to the first reactor at a flow rate of 18.5 to 20 kg / hour, wherein the molar ratio of BTF:98% H2SO4:98% HNO3 was 1:1.10:1.02 to 1:1.10:1.05. The agitator RPM speed was maintained between 550 and 650. The residence time in the first reactor was maintained at 60 to 90 minutes, and the residence time in the 250L second reactor was maintained at 240 minutes. The temperature of the first reactor was maintained at 5°C to 7°C by internal circulation of the jacket and chilled brine. In this example, the total conversion of the reactants in the continuous reactor mode was about 98% in the first reactor, and the remaining conversion of up to 2% was carried out in the second reactor. The yields of nitro species obtained from the first and second reactors are disclosed in Table 2b below:

[0089] Table 2b

[0090]

[0091] Referring to Table 2b, the overall reduced residence time of 60 to 90 minutes and 240 minutes in the second reactor to achieve maximum conversion, the yield of 3-nitroBTF was obtained to be 89.06 to 90%, and about 0.8 to 2% nitric acid remained in the waste liquid. In addition, in the case of the dual reactor mode formation, the HF content was reduced to 5 to 10 ppm. In addition, safety-related problems such as flow fluctuations, freezing of reaction materials and overflow line blockage, inconsistent flow, overflow line siphoning and sudden flow, etc. were also eliminated. In addition, the maximum conversion of the reactants was observed.

[0092] According to an embodiment of the present disclosure, the above-mentioned system (100) and method (100) for continuously producing mononitrobenzene trifluoride (NBTF) have the following advantages, including but not limited to:

[0093] Significantly shorten reaction cycle time.

[0094] Utilize compact space to increase overall production scale.

[0095] Significantly reduce the generation of corrosive byproducts (HF), with a conversion rate of up to 99.6%.

[0096] The embodiments, examples and alternatives of the preceding paragraphs or the description and drawings, including any of their aspects or individual features, may be used independently or in any combination. Features described in one embodiment are applicable to all embodiments unless these features are incompatible.

[0097] The above description should be interpreted as illustrative rather than any limiting meaning. It will be appreciated by those skilled in the art that some modifications may fall within the scope of the present invention. In order to limit the scope of the present invention, it is necessary to submit a subsequent complete description to determine the true scope and content of the present disclosure.

Claims

1. A system (100) for continuously producing mononitrobenzene trifluoride (NBTF), comprising: a first reactor (105) for mononitration of benzene trifluoride (BTF) by reaction conversion of 90% to 98% of reactants comprising benzene trifluoride (BTF), H2SO4 and nitric acid; A second reactor (106) for mononitration of benzene trifluoride to complete the remaining 2% to 10% reaction conversion of the reactants; a third reactor (107) capable of separating the spent acid and the organic layer containing nitrobenzene trifluoride by adding water to maintain the desired strength of the spent acid; and A washing unit (108) for washing the organic layer and separating 4-nitrobenzenetrifluoride (4-NBTF), 2-nitrobenzenetrifluoride (2-NBTF) and 3-nitrobenzenetrifluoride (3-NBTF).

2. The system according to claim 1, wherein: The concentration of the nitric acid is 72% to 98% to adjust the reaction heat and water content in the reaction.

3. The system according to claim 1, wherein: The first reactor (105) comprises: An improved agitator (204) having multiple turbine blades (205) for high shear agitation.

4. The system according to claim 1, wherein: The first reactor (105) comprises: a vortex breaking device (208) for proper and uniform mixing of the reactants, one or more internal baffles (206), internal cooling coils (211) and a cooling brine jacket (207).

5. The system according to claim 1, wherein: The first reactor (105) includes an overflow outlet (209) including a fixture (210) capable of transferring the reaction material without siphoning the unreacted material of the first reactor (105) to the second reactor (106).

6. The system according to claim 1, wherein: The system (100) includes a BTF and H2SO4 mixing chamber (103) for adding a premix of BTF and H2SO4 into a first reactor (105).

7. The system according to claim 1, wherein: The system (100) is capable of feeding a nitrating agent from a nitrating agent feed tank (104), wherein the nitrating agent feed tank is capable of feeding at least one of 72% to 98% nitric acid to the first reactor (105).

8. The system according to claim 1, wherein: The first reactor (105) comprises a cooling brine jacket (207) and internal cooling coils (211) configured to maintain the temperature of the first reactor and the second reactor between 1°C and 12°C, preferably 4-9°C.

9. The system according to claim 1, wherein: The flow rate of each raw material of trifluorinated benzene, nitric acid and sulfuric acid components is controlled by adjusting the operating rate of the metering pump so that the reactants are delivered to the reaction chamber of the first reactor (105) in a stoichiometric ratio of trifluorinated benzene and the reaction temperature is maintained at less than 5°C to 7°C.

10. The system according to claim 1, wherein: The second reactor (106) is configured to maintain stirring the reaction mass under high shear to complete the remaining 2% to 10% conversion of the reaction mass within a predetermined time, thereby achieving 100% conversion.

11. The system according to claim 1, wherein: The system (100) is configured to achieve maximum yields of desired 3-nitroBTF product up to 89-91%, 2-nitroBTF product up to 7-8%, and 4-nitroBTF product up to 2-2.5%.

12. The system of claim 1, wherein: The residence time of the first reactor (105) is 60 to 80 minutes, and the residence time of the second reactor (106) is 2 to 2.5 hours.

13. A method (400) for continuously synthesizing mononitrobenzene trifluoride (NBTF), comprising: Adding (401) a predetermined molar ratio of benzene trifluoride (BTF) and 98% sulfuric acid (H2SO4) into the first reactor (105); After cooling the first reactor (105) to a temperature in the range of 5°C to 10°C, adding (402) a predetermined molar ratio of a nitrating agent such as strong nitric acid (HNO3); determining (403) that the level of the reaction mixture in the first reactor (105) reaches an overflow level and being able to simultaneously add (304) 98% sulfuric acid (H2SO4), nitric acid (HNO3) and benzene trifluoride (BTF) in the first reactor (105); maintaining (404) the predetermined flow rate to carry out the above reaction for about 45 to 75 minutes to obtain a nitro substance of a mixture containing mononitrobenzene trifluoride (NBTF); Optimizing (405) the inlet and outlet flow rates of the second reactor (106) so that the residence time is 1 to 2 hours; conveying (406) the nitro species obtained in the second reactor (106) to the third reactor (107) for layer separation into spent acid and organic layers; The organic layer separated in the third reactor (107) is washed (108) through (407) to obtain a specific percentage of pure 3-nitrobenzenetrifluoride (3-NBTF), 2-nitrobenzenetrifluoride (2-NBTF) and 4-nitrobenzenetrifluoride (4-NBTF).

14. The method according to claim 13, wherein: The concentrations of the nitric acid are 72% and 98%.

15. The method according to claim 13, wherein: The temperature was maintained at 5-10°C by a combination of the jacket and internally circulating cooling brine.

16. The method according to claim 13, wherein: The temperature of the first reactor (105) and the second reactor (106) is maintained in the range of 5 to 10°C by jacket circulation (207), (304) and cooling brine and internal cooling coils (211), (305).

17. The method according to claim 13, wherein: In step (404), benzene trifluoride, 98% sulfuric acid and 72% nitric acid are continuously fed into the first reactor (105) through corresponding feed tanks (101, 102, 103, 104), wherein the molar ratio of BTF:98% H2SO4:72% HNO3 is 1:2.08:1.02 to 1:2.08:1.

10.

18. The method according to claim 13, wherein: In step (404), benzene trifluoride, 98% sulfuric acid and 98% nitric acid are continuously fed into the first reactor (105) through corresponding feed tanks (101, 102, 103, 104), wherein the molar ratio of BTF: 98% H2SO4: 98% HNO3 is 1:1.01:1.02 to 1:1.1:1.

10.

19. The method according to claim 13, wherein: In step (407), the organic layer containing nitro species and the spent acid are transferred to a third reactor (107) configured to dilute the mixture of organic products 3-nitrobenzene trifluoride, 2-nitrobenzene trifluoride and 4-nitrobenzene trifluoride and separate them from the spent acid by adding water to a degree that the spent acid concentration is maintained at about 72% to 75%.

20. The method according to claim 14, wherein: The mixture of organic products is then separated from the spent acid layer, and the spent acid contains 1.0-1.5% nitric acid, 72.0-75.0% sulfuric acid.

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