Method for preparing mononitroarene using nitro-sulfur mixed acid

Abstract

The application relates to the technical field of chemical engineering, in particular to a method for preparing mononitro aromatic hydrocarbon by using nitric-sulfur mixed acid. The method can improve the selectivity and reaction efficiency of the mononitro aromatic hydrocarbon, reduce the difficulty of separation and purification, reduce the risk of combustion and explosion, and reduce the safety hidden danger. The method for preparing mononitro aromatic hydrocarbon by using nitric-sulfur mixed acid comprises the following steps: preparing mixed acid of nitric acid and sulfuric acid; gasifying aromatic hydrocarbon to prepare gaseous aromatic hydrocarbon; mixing the gaseous aromatic hydrocarbon and the mixed acid at a preset ratio, and making the mixed gaseous aromatic hydrocarbon and the mixed acid react at a first preset temperature to prepare mononitro aromatic hydrocarbon; wherein the preset ratio satisfies that the molar ratio of the nitric acid in the mixed acid to the gaseous aromatic hydrocarbon is 1:(1-2). The application is used for preparing mononitro aromatic hydrocarbon by using nitric-sulfur mixed acid and gaseous aromatic hydrocarbon.

Description

Technical Field

[0001] This application relates to the field of chemical engineering technology, and in particular to a method for preparing mononitro aromatic hydrocarbons using a mixture of nitric and sulfuric acids. Background Technology

[0002] The nitration of aromatics is a fundamental reaction in industrial production. Its product, nitroaromatics, is an important chemical raw material and intermediate, and is widely used in the production processes of pharmaceuticals, dyes, pesticides, and energetic materials.

[0003] In current research, the nitration of aromatics mainly involves a liquid-liquid heterogeneous reaction between nitrate-sulfur mixed acid and aromatics. This reaction is characterized by a fast intrinsic reaction rate and high exothermic intensity. The reaction process is severely limited by mass transfer, resulting in a long residence time. This can easily lead to over-nitration side reactions and the generation of polynitroaromatic byproducts. Consequently, the selectivity of mononitroaromatics is low, the efficiency is low, and there is a risk of combustion and explosion during the reaction and separation process, posing significant safety hazards during separation and purification. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for preparing mononitroaromatic hydrocarbons using a mixture of nitric and sulfuric acids, so as to improve the selectivity and reaction efficiency of mononitroaromatic hydrocarbons, reduce the difficulty of separation and purification, reduce the risk of combustion and explosion, and reduce safety hazards.

[0005] This application provides a method for preparing mononitroaromatic hydrocarbons using a nitric-sulfur mixed acid, comprising:

[0006] Preparation of a mixed acid of nitric acid and sulfuric acid;

[0007] Gasification of aromatics to prepare gaseous aromatics;

[0008] The gaseous aromatic hydrocarbon and the mixed acid are mixed in a preset ratio, and the mixed gaseous aromatic hydrocarbon and the mixed acid undergo a gas-liquid heterogeneous reaction at a first preset temperature to prepare the mononitro aromatic hydrocarbon;

[0009] The preset ratio satisfies the following condition: the molar ratio of nitric acid in the mixed acid to the gaseous aromatic hydrocarbon is 1:(1-2).

[0010] Optionally, the vaporization of aromatics to prepare gaseous aromatics includes:

[0011] The aromatic hydrocarbon is heated to a second preset temperature to vaporize it into gaseous aromatic hydrocarbon; wherein the second preset temperature is greater than or equal to the boiling point temperature of the aromatic hydrocarbon and less than or equal to the sum of the boiling point temperature of the aromatic hydrocarbon and 100°C.

[0012] The step of mixing the gaseous aromatic hydrocarbon and the mixed acid in a preset ratio, and causing the mixed gaseous aromatic hydrocarbon and the mixed acid to undergo a gas-liquid heterogeneous reaction at a first preset temperature, includes:

[0013] The mixed acid is heated to the second preset temperature;

[0014] The gaseous aromatic hydrocarbon and the mixed acid are mixed at a first flow rate and a second flow rate, respectively, and the mixed gaseous aromatic hydrocarbon and the mixed acid are brought into contact at a first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon; or, the gaseous aromatic hydrocarbon is bubbled into the mixed acid, and the gaseous aromatic hydrocarbon and the mixed acid are mixed under stirring, and after bubbling is completed, the mixed gaseous aromatic hydrocarbon and the mixed acid are kept at the first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon;

[0015] Wherein, the first flow rate and the second flow rate satisfy the following: the molar ratio of the gaseous aromatic hydrocarbon and the mixed acid mixed per unit time satisfies the preset ratio.

[0016] Optionally, the preset time is 0.1s to 20s.

[0017] Optionally, when the gaseous aromatic hydrocarbon and the mixed acid are mixed at a first flow rate and a second flow rate, and the mixed gaseous aromatic hydrocarbon and the mixed acid are contacted at a first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon, the mixing and reaction process of the gaseous aromatic hydrocarbon and the mixed acid is carried out in a continuous flow reactor.

[0018] Optionally, the continuous flow reactor is a static mixer, a microreactor, or a tubular reactor.

[0019] Optionally, in the case where the gaseous aromatic hydrocarbon is bubbled into the mixed acid and the gaseous aromatic hydrocarbon and the mixed acid are mixed under stirring, and after bubbling is completed, the mixed gaseous aromatic hydrocarbon and the mixed acid are kept at the first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon, the mixing and reaction process of the gaseous aromatic hydrocarbon and the mixed acid is carried out in a batch reactor.

[0020] Optionally, the method further includes:

[0021] The product after the gas-liquid heterogeneous reaction is subjected to phase separation treatment to prepare the mononitro aromatic hydrocarbon.

[0022] Optionally, the step of performing phase separation treatment on the product after the gas-liquid heterogeneous reaction to prepare the mononitroaromatic hydrocarbon includes:

[0023] After the gaseous aromatic hydrocarbon and the mixed acid have been contacted at a first preset temperature for a preset time, the products resulting from the gas-liquid heterogeneous reaction are subjected to gas-liquid phase separation treatment; and

[0024] The mixed solution obtained from gas-liquid phase separation is subjected to liquid-liquid phase separation, and the organic phase is collected.

[0025] Optionally, the preparation of the mixed acid of nitric acid and sulfuric acid includes:

[0026] Concentrated sulfuric acid is diluted to prepare a sulfuric acid solution with a mass percentage concentration of 50% to 90%.

[0027] The mixed acid is prepared by mixing fuming nitric acid and the sulfuric acid solution.

[0028] Optionally, the mass ratio of the fuming nitric acid to the sulfuric acid solution is 1:(100-1000).

[0029] Compared with related technologies, this application has the following technical advantages:

[0030] Compared to the liquid-liquid nitration reaction of aromatics with mixed nitrate and sulfuric acid, by mixing gaseous aromatics and mixed acid in a preset ratio and allowing the mixed gaseous aromatics and mixed acid to undergo a gas-liquid heterogeneous reaction at a first preset temperature, the aromatics can be mixed and contacted with the mixed acid in gaseous form. On the one hand, since gaseous aromatics are used to react with mixed acid in this application, the reaction temperature (i.e., the first preset temperature in this application) can be significantly higher than the temperature of the liquid-liquid nitration reaction. Therefore, the intrinsic reaction rate of the main reaction to generate mononitroaromatics is greatly increased, while the occurrence of overnitration side reactions is greatly reduced. This can improve the selectivity of mononitroaromatics, reduce the risks of combustion and explosion caused by by-products, and reduce safety hazards in subsequent separation and purification processes. On the other hand, mixing gaseous aromatics with mixed acids can leverage the high diffusion coefficient of the gaseous aromatics to significantly improve mass transfer during the reaction. This facilitates the full consumption of nitric acid in the main reaction, reduces the formation of polynitroaromatic byproducts due to slow mass transfer rates, and consequently improves the selectivity of mononitroaromatics while reducing reaction time. This also reduces the risks of combustion and explosion associated with byproducts, as well as safety hazards during subsequent separation and purification. This approach solves the problems in related technologies, such as poor liquid-liquid mass transfer uniformity during the reaction of aromatics and mixed acids, leading to increased byproducts, lower selectivity and efficiency of mononitroaromatics, and the risk of combustion and explosion during the reaction, resulting in significant safety hazards during separation and purification. Attached Figure Description

[0031] Figure 1This is a schematic flowchart of a method for preparing mononitroaromatic hydrocarbons using a nitrate-sulfur mixed acid, provided as an embodiment of this application. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "exemplary," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0034] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0035] In this document, unless otherwise stated, "one or more" means one or more.

[0036] In this document, terms such as "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the content covered by different technical solutions presented earlier and later. However, they should not be construed as limitations on the preceding technical solution or as restrictions on the scope of protection of this document. In this document, unless otherwise specified, A (like B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0037] In this article, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "options" in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "option" is independent.

[0038] In this article, descriptions such as "optionally contains" and "optionally includes" indicate whether or not the component X is present. "Optional component X" indicates whether component X is present or absent, or whether or not component X is present.

[0039] In this document, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features.

[0040] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0042] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0043] In this document, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise expressly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0044] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.

[0045] In this article, unless otherwise specified, percentage content refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0046] Unless otherwise specified, all percentage concentrations mentioned in this article refer to the final concentration. The final concentration refers to the proportion of the added ingredient in the system after the addition of that ingredient.

[0047] In this article, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0048] In this document, temperature parameters are used. Unless otherwise specified, both isothermal processing and processing within a certain temperature range are permitted. The isothermal processing allows temperature fluctuations within the precision range controlled by the instrument.

[0049] In this document, the terms "room temperature" or "normal temperature" generally refer to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0050] Based on the above technical problems, some embodiments of this application provide a method for preparing mononitro aromatic hydrocarbons using a nitrate-sulfur mixed acid, such as... Figure 1 As shown, the method includes the following steps S11) to S13):

[0051] S11), to prepare a mixed acid of nitric acid and sulfuric acid;

[0052] Among them, the use of mixed nitrate and sulfuric acid can efficiently generate the nitration active intermediate NO2. + This facilitates the efficient nitration of aromatics.

[0053] The specific preparation method of the above-mentioned mixed acid is not limited, as long as a nitrate-sulfur mixed acid can be obtained to achieve the nitration of aromatics. The specific concentration of the nitrate-sulfur mixed acid can be reasonably selected according to actual needs to reduce the formation of by-products such as sulfonation products and polynitroaromatics.

[0054] In some embodiments, S11) preparing a mixed acid of nitric acid and sulfuric acid includes the following steps S111) to S112):

[0055] S111) Dilute concentrated sulfuric acid to prepare a sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 50% to 90%;

[0056] The concentrated sulfuric acid can be 98% sulfuric acid by mass percentage (i.e., mass fraction). By diluting this concentrated sulfuric acid, a sulfuric acid solution with a mass percentage concentration of 50% to 90% can be prepared.

[0057] S112) The mixed acid is prepared by mixing fuming nitric acid and sulfuric acid solution.

[0058] Fuming sulfuric acid can be concentrated nitric acid with a mass percentage concentration of 98%.

[0059] The mixed acid is prepared by mixing fuming nitric acid and sulfuric acid solutions; this may include:

[0060] Add the fuming nitric acid to the sulfuric acid solution prepared in step S111) and mix thoroughly; or add the sulfuric acid solution prepared in step S111) to the fuming nitric acid and mix thoroughly.

[0061] The mass ratio of the fuming nitric acid and sulfuric acid solution can be reasonably selected according to actual needs, and no specific limit is made here.

[0062] Sulfuric acid is a strong acid that can provide protons for the dissociation of nitric acid, thus increasing the dissociation of nitric acid into NO2. + Furthermore, sulfuric acid has a stronger affinity for water than nitric acid, which can reduce or avoid the dilution of nitric acid by the water produced in the reaction, thus improving the utilization rate of nitric acid. As nitric acid is diluted by sulfuric acid solution, its oxidizing power and corrosion intensity decrease, making it less prone to oxidation side reactions and reducing corrosion of cast iron equipment.

[0063] Based on this, in some embodiments of this application, the mass ratio of fuming nitric acid and sulfuric acid solution is 1:(100-1000).

[0064] In these embodiments, a nitrate-sulfur mixture of appropriate concentrations can be provided to facilitate the nitration of aromatics into mononitroaromatics and reduce byproducts.

[0065] S12) Gasification of aromatics to prepare gaseous aromatics;

[0066] The aromatic hydrocarbon may, for example, include compounds containing a benzene ring in their molecules, such as benzene, toluene, chlorobenzene, xylene, ethylbenzene, naphthalene, tetrahydronaphthalene, etc.

[0067] The aromatic hydrocarbon can be vaporized in any way, as long as it can be converted into a gaseous aromatic hydrocarbon. The specific vaporization method is not limited here. The vaporization can be heating vaporization or spray vaporization, etc.

[0068] S13) Gaseous aromatic hydrocarbons and mixed acids are mixed in a preset ratio, and the mixed gaseous aromatic hydrocarbons and mixed acids undergo a gas-liquid heterogeneous reaction at a first preset temperature to prepare mononitro aromatic hydrocarbons.

[0069] In this method, gaseous aromatics and mixed acids are mixed in a preset ratio, and the mixed gaseous aromatics and mixed acids undergo a gas-liquid heterogeneous reaction at a first preset temperature. Compared with related technologies that use liquid-liquid mixing of aromatics and mixed acids and undergo a liquid-liquid heterogeneous reaction, this method can increase the dispersion effect of gaseous aromatics in mixed acids and increase the specific surface area when gaseous aromatics and mixed acids come into contact, thereby increasing the mass transfer effect and improving the mass transfer uniformity. This can solve the problems in related technologies, such as slow mass transfer rate and poor uniformity during the reaction of aromatics and mixed acids, resulting in long reaction time for mononitration, increased by-products, low selectivity of mononitroaromatics, low efficiency, and the risk of combustion and explosion during the reaction, which pose significant safety hazards during separation and purification.

[0070] In some embodiments, the above-mentioned preset ratio satisfies the following: the molar ratio of nitric acid to gaseous aromatic hydrocarbons in the mixed acid is 1:(1-2).

[0071] In these embodiments, by controlling the molar ratio of nitric acid to gaseous aromatics in the mixed acid to be 1:(1-2), the molar ratio of nitric acid to gaseous aromatics can be effectively controlled, thereby enabling nitric acid and gaseous aromatics to react to generate mononitro aromatics rather than polynitro aromatics.

[0072] Optionally, the molar ratio of nitric acid to gaseous aromatics in the mixed acid is 1:1.1 to 1:1.5. This results in a slight excess of gaseous aromatics, facilitating the rapid consumption of nitric acid in the mononitration reaction during the aforementioned gas-liquid heterogeneous reaction to generate mononitro aromatics. This improves the selectivity of mononitro aromatics, thereby reducing the generation of byproducts such as polynitro aromatics, minimizing safety hazards, increasing reaction efficiency, and reducing unnecessary exothermic reactions, thus reducing energy consumption.

[0073] In the method for preparing mononitroaromatic hydrocarbons using a nitrate-sulfur mixed acid provided in this application embodiment, by mixing gaseous aromatic hydrocarbons and mixed acid in a preset ratio, and causing the mixed gaseous aromatic hydrocarbons and mixed acid to undergo a gas-liquid heterogeneous reaction at a first preset temperature, the aromatic hydrocarbons can be mixed and contacted with the mixed acid in gaseous form. On the one hand, since gaseous aromatic hydrocarbons are used to react with the mixed acid in this application, the reaction temperature used (i.e., the first preset temperature in this application) can be significantly higher than the temperature of the liquid-liquid nitration reaction. Therefore, the intrinsic reaction rate of the main reaction for generating mononitroaromatic hydrocarbons is greatly increased, while the occurrence of overnitration side reactions is greatly reduced. This can improve the selectivity of mononitroaromatic hydrocarbons, reduce the risks of combustion and explosion caused by by-products, and reduce safety hazards in subsequent separation and purification processes. On the other hand, mixing gaseous aromatics with mixed acids can leverage the high diffusion coefficient of the gaseous aromatics to significantly improve mass transfer during the reaction. This facilitates the full consumption of nitric acid in the main reaction, reduces the formation of polynitroaromatic byproducts due to slow mass transfer rates, and consequently improves the selectivity of mononitroaromatics while reducing reaction time. This also reduces the risks of combustion and explosion associated with byproducts, as well as safety hazards during subsequent separation and purification. This approach solves the problems in related technologies, such as poor liquid-liquid mass transfer uniformity during the reaction of aromatics and mixed acids, leading to increased byproducts, lower selectivity and efficiency of mononitroaromatics, and the risk of combustion and explosion during the reaction, resulting in significant safety hazards during separation and purification.

[0074] The specific implementation methods of S12) gasifying aromatics to prepare gaseous aromatics and S13) mixing gaseous aromatics and mixed acids in a preset ratio and causing the mixed gaseous aromatics and mixed acids to undergo a gas-liquid heterogeneous reaction at a first preset temperature are not limited. All possible technical solutions for preparing mononitroaromatics are within the protection scope of this application, as long as they can gasify aromatics, mix gaseous aromatics and mixed acids in a preset ratio, and cause the mixed gaseous aromatics and mixed acids to undergo a gas-liquid heterogeneous reaction at a first preset temperature.

[0075] In some embodiments of this application, aromatic hydrocarbons are vaporized to prepare gaseous aromatic hydrocarbons; including:

[0076] The aromatic hydrocarbon is heated to a second preset temperature to vaporize it into gaseous aromatic hydrocarbon; wherein the second preset temperature is greater than or equal to the boiling point temperature of the aromatic hydrocarbon and less than or equal to the sum of the boiling point temperature of the aromatic hydrocarbon and 100°C.

[0077] The gaseous aromatic hydrocarbon and the mixed acid are mixed in a preset ratio, and the mixed gaseous aromatic hydrocarbon and the mixed acid undergo a gas-liquid heterogeneous reaction at a first preset temperature, including:

[0078] Heat the mixed acid to a second preset temperature;

[0079] Gaseous aromatic hydrocarbons and mixed acids are mixed at a first flow rate and a second flow rate, respectively, and the mixed gaseous aromatic hydrocarbons and mixed acids are brought into contact at a first preset temperature for a preset time to react and generate mononitro aromatic hydrocarbons; or, gaseous aromatic hydrocarbons are bubbled into mixed acids, and the gaseous aromatic hydrocarbons and mixed acids are mixed under stirring, and after bubbling is completed, the mixed gaseous aromatic hydrocarbons and mixed acids are kept at the first preset temperature for a preset time to react and generate mononitro aromatic hydrocarbons;

[0080] Wherein, the first flow rate and the second flow rate satisfy the following: the molar ratio of the gaseous aromatic hydrocarbon and the mixed acid mixed per unit time satisfies the preset ratio.

[0081] In these embodiments, gaseous aromatic hydrocarbons and mixed acids are mixed at a first flow rate and a second flow rate, respectively, and the mixed gaseous aromatic hydrocarbons and mixed acids are contacted at a first preset temperature for a preset time to react and generate mononitroaromatic hydrocarbons. Since the first flow rate and the second flow rate satisfy the above-mentioned preset ratio for the molar ratio of gaseous aromatic hydrocarbons and mixed acids mixed per unit time, the nitric acid in the gaseous aromatic hydrocarbons and mixed acids can continuously undergo a continuous flow reaction with a precise mixing ratio. On the one hand, this facilitates the mixing of gaseous aromatic hydrocarbons and mixed acids and their contact at the first preset temperature; on the other hand, the contact time after the gaseous aromatic hydrocarbons and mixed acids are mixed can be controlled, thereby facilitating the control of the reaction between gaseous aromatic hydrocarbons and mixed acids to generate mononitroaromatic hydrocarbons and further reducing the occurrence of side reactions.

[0082] By bubbling gaseous aromatics into the mixed acid and stirring them together, it is easier for the gaseous aromatics and the mixed acid to mix and come into contact at a first preset temperature. After bubbling, by maintaining the mixed gaseous aromatics and the mixed acid at the first preset temperature for a preset time, the gaseous aromatics and the mixed acid can come into sufficient contact over a longer reaction time, which facilitates the reaction of the gaseous aromatics and the mixed acid to generate mononitro aromatics and reduces the occurrence of side reactions.

[0083] Meanwhile, in these embodiments, aromatics are vaporized through heating. On the one hand, this facilitates the transport of aromatics in a gaseous state, improving mass transfer efficiency compared to the liquid mass transfer of aromatics and mixed acids in related technologies, where the liquid has high viscosity and high mass transfer resistance. On the other hand, heating the mixed acid reduces its viscosity compared to the lower temperature and higher viscosity of the mixed liquid in related technologies, facilitating its transport and mixing. This allows for faster mixing of gaseous aromatics and mixed acids, further improving mass transfer efficiency. Furthermore, the gaseous aromatics... Hydrocarbons can contact mixed acids with a high specific surface area, which can improve mass transfer. This allows for uniform mass and heat transfer between gaseous aromatics and mixed acids, facilitating the formation of mononitro aromatics and reducing local high temperatures. As the reaction proceeds, the volume of aromatic bubbles gradually decreases, further significantly reducing interphase mass transfer resistance and significantly reducing the limitation of mass transfer on the nitration reaction. In this process, compared with liquid-liquid heterogeneous reactions, it can improve mass transfer efficiency and mononitration rate, save reaction time, thereby improving the selectivity of mononitro aromatics and further reducing the formation of polynitro aromatics.

[0084] The preset time is not specifically limited. The reaction time can be controlled according to the amount of reaction, temperature and mixing rate, so as to minimize the limitation of mass transfer on the nitration reaction and increase the reaction rate.

[0085] In some embodiments, the preset time is 0.1s to 20s.

[0086] In these embodiments, by controlling the preset time to 0.1s to 20s, the generation of polynitroaromatic byproducts can be reduced to a certain extent, while the generation of mononitroaromatics can be increased, thereby improving the selectivity of mononitroaromatics and increasing efficiency.

[0087] The application does not specifically limit the type of reactor used to mix the gaseous aromatic hydrocarbon and the mixed acid at a first flow rate and a second flow rate, and to contact the mixed gaseous aromatic hydrocarbon and the mixed acid at a first preset temperature for a preset time. All reactors that can mix the gaseous aromatic hydrocarbon and the mixed acid at a first flow rate and a second flow rate, and to contact the mixed gaseous aromatic hydrocarbon and the mixed acid at a first preset temperature for a preset time, are within the scope of protection of this application.

[0088] In some embodiments, when gaseous aromatic hydrocarbons and mixed acids are mixed at a first flow rate and a second flow rate, and the mixed gaseous aromatic hydrocarbons and mixed acids are contacted at a first preset temperature for a preset time to react and generate mononitroaromatic hydrocarbons, the mixing and reaction process of gaseous aromatic hydrocarbons and mixed acids is carried out in a continuous flow reactor.

[0089] In some embodiments, the continuous flow reactor is a static mixer, a microreactor, or a tubular reactor.

[0090] In the case where the aforementioned continuous flow reactor is a microreactor, the microreactor may include a first pipe and a second pipe that intersect and are connected, and a third pipe that is connected to the intersection and connection of the first pipe and the second pipe. The first pipe can be used to transport gaseous aromatics, and the second pipe can be used to transport mixed acids. The gaseous aromatics and mixed acids are mixed at the intersection and connection of the first pipe and the second pipe and flow into the third pipe. The mixed gaseous aromatics and mixed acids flow at the same speed in the third pipe, so that the mixed gaseous aromatics and mixed acids can contact each other for a preset time and react.

[0091] The reactor type used for the reaction of the gaseous aromatic hydrocarbons into the mixed acid by bubbling and mixing with stirring, and for maintaining the mixed gaseous aromatic hydrocarbons and mixed acid at a first preset temperature for a preset time after bubbling, is not specifically limited.

[0092] In some embodiments, gaseous aromatic hydrocarbons are bubbled into a mixed acid, and the gaseous aromatic hydrocarbons and the mixed acid are mixed under stirring. After bubbling is completed, the mixed gaseous aromatic hydrocarbons and the mixed acid are kept at a first preset temperature for a preset time to react and generate mononitro aromatic hydrocarbons. The mixing and reaction process of gaseous aromatic hydrocarbons and mixed acid is carried out in a batch reactor.

[0093] The stirring speed can be set as needed, and no specific limit is set here.

[0094] It should also be noted that during the bubbling process described above, as the gaseous aromatics are bubbled into the mixed acid at a certain rate, the gaseous aromatics and the mixed acid react upon contact, and both the gaseous aromatics and nitric acid are consumed. Stirring allows the gaseous aromatics and nitric acid to mix and contact fully, reducing localized high temperatures and thus minimizing the formation of byproducts. Simultaneously, after bubbling is complete, maintaining the mixed gaseous aromatics and the mixed acid at the first preset temperature for a preset time ensures sufficient contact and reaction between them. Those skilled in the art will understand that when this mixing and reaction is carried out in a batch reactor, the reactor can be sealed during the bubbling process. The reactor is opened only after the mixed gaseous aromatics and the mixed acid have been maintained at the first preset temperature for a preset time, thereby ensuring sufficient contact between the gaseous aromatics and the mixed acid, reducing the loss of gaseous aromatics into the air, and maintaining the nitric acid and gaseous aromatics in the mixed acid at the aforementioned preset ratio for mixing and reaction.

[0095] In some embodiments, the above method may further include:

[0096] The products of the gas-liquid heterogeneous reaction are subjected to phase separation treatment to prepare mononitro aromatic hydrocarbons.

[0097] In some embodiments, the products following a gas-liquid heterogeneous reaction are subjected to phase separation treatment to prepare mononitroaromatic hydrocarbons, including:

[0098] After gaseous aromatics and mixed acids are contacted at a first preset temperature for a preset time, the products resulting from the gas-liquid heterogeneous reaction are subjected to gas-liquid phase separation treatment; and

[0099] The mixed solution obtained from gas-liquid phase separation is subjected to liquid-liquid phase separation, and the organic phase is collected.

[0100] In these embodiments, a gas-liquid phase separation process is first performed to separate the unreacted gaseous aromatics from the reaction products, while a liquid-liquid phase separation process is performed to remove the unreacted mixed acid, thereby obtaining the organic phase mononitro aromatics.

[0101] In some examples, after the gaseous aromatic hydrocarbons and the mixed acid have been in contact at a first preset temperature for a preset time, a gas-liquid phase separation process can be performed directly at a higher temperature to separate the unreacted gaseous aromatic hydrocarbons from the reaction products. Then, the organic phase can be washed with alkali and water until it is neutral to obtain the organic phase free of the mixed acid.

[0102] In order to objectively evaluate the technical effects of the embodiments of this application, the application will be described in detail through the following embodiments.

[0103] In the following examples, all raw materials were commercially available, and to maintain the reliability of the experiments, the raw materials used in the following examples all had the same physical and chemical parameters or were prepared by the same processing method.

[0104] Example 1

[0105] Example 1 describes a method for preparing mononitroaromatic hydrocarbons using a nitric-sulfur mixed acid:

[0106] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 80g of water to obtain 280g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 70%;

[0107] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 70% to obtain nitric acid mixed acid A;

[0108] (3) Heat the nitrate-sulfuric acid A and toluene to 150°C respectively, so that the toluene is completely vaporized into toluene vapor B;

[0109] (4) Nitrosulfuric acid A and toluene vapor B are fed into the microreactor at a flow rate of 1 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of toluene to nitric acid is 1.5. The residence time of the material in the microreactor is 5 s. After gas-liquid phase separation, a mixture of mononitrotoluene and sulfuric acid solution is obtained.

[0110] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrotoluene product.

[0111] Test results:

[0112] The mononitrotoluene prepared in Example 1 was detected by ultra-high performance liquid chromatography (UHPLC). The selectivity for mononitrotoluene was 99.95%, the selectivity for the dinitrotoluene byproduct was less than 0.05%, and the nitric acid conversion rate was higher than 99.9%. The UHPLC test conditions were as follows: mobile phase was water and methanol in a volume ratio of 0.65:0.35, flow rate was 0.2 mL / min, injection volume was 1 μL, and the column packing material was fluorophenyl (PFP) with a particle size of 1.8 μm, an inner diameter of 3 mm, and a length of 50 mm.

[0113] Example 2

[0114] Example 2 shows the method for preparing mononitroaromatic hydrocarbons using a mixture of nitric and sulfuric acids:

[0115] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 45g of water to obtain 245g of sulfuric acid solution with a percentage concentration (i.e., mass fraction) of 80%;

[0116] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 80% to obtain nitric acid mixed acid A;

[0117] (3) Heat the nitrate-sulfuric acid A and benzene to 100°C respectively, so that the benzene is completely vaporized into benzene vapor B;

[0118] (4) Nitro-sulfur mixed acid A and benzene vapor B are fed into a static mixer at a flow rate of 1.5 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of benzene to nitric acid is 1.5. The residence time of the material in the static reactor is 5 s. After gas-liquid phase separation, a mixture of product mononitrobenzene and sulfuric acid solution is obtained.

[0119] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrobenzene product.

[0120] Test results:

[0121] The mononitrobenzene prepared in Example 2 was detected by liquid chromatography, and the selectivity of mononitrobenzene was 99.98%, the selectivity of dinitrobenzene was less than 0.02%, and the conversion rate of nitric acid was greater than 99.9%. The test conditions for liquid chromatography were the same as those in Example 1.

[0122] Example 3

[0123] Example 3 describes a method for preparing mononitroaromatic hydrocarbons using a mixture of nitric and sulfuric acids:

[0124] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 17.78g of water to obtain 217.78g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 90%;

[0125] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 90% to obtain nitric acid mixed acid A;

[0126] (3) Heat the nitrate-sulfur mixed acid A and chlorobenzene to 160°C respectively, so that the chlorobenzene is completely vaporized into chlorobenzene vapor B;

[0127] (4) Chlorobenzene vapor B is bubbled into the reaction vessel containing nitrate-sulfur mixed acid at a flow rate of 1.5 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of chlorobenzene to nitric acid is 2. The reaction ends about 1 second after the chlorobenzene gas is completely bubbled. The remaining liquid phase in the reaction vessel is a mixture of product mononitrochlorobenzene and sulfuric acid solution.

[0128] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrochlorobenzene product.

[0129] Test results:

[0130] The mononitrochlorobenzene prepared in Example 3 was detected by liquid chromatography, and the selectivity of mononitrochlorobenzene was 99.96%, the selectivity of dinitrochlorobenzene was less than 0.04%, and the nitric acid conversion rate was higher than 99.9%. The test conditions for liquid chromatography were the same as those in Example 1.

[0131] Example 4

[0132] Example 4 describes a method for preparing mononitroaromatic hydrocarbons using a mixture of nitric and sulfuric acids:

[0133] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 45g of water to obtain 245g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 80%;

[0134] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 80% to obtain nitric acid mixed acid A;

[0135] (3) Heat the nitrate-sulfuric acid A and benzene to 120°C respectively, so that the benzene is completely vaporized into benzene vapor B;

[0136] (4) Nitrosulfuric acid A and benzene vapor B are fed into a tubular reactor at a flow rate of 2 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of benzene to nitric acid is 1.5. The residence time of the material in the tubular reactor is 10 s. After gas-liquid phase separation, a mixture of mononitrobenzene and sulfuric acid solution is obtained.

[0137] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrobenzene product.

[0138] Test results:

[0139] The mononitrobenzene prepared in Example 4 was detected by liquid chromatography, and the selectivity of mononitrobenzene was 99.98%, the selectivity of dinitrobenzene was less than 0.02%, and the conversion rate of nitric acid was greater than 99.9%. The test conditions for liquid chromatography were the same as those in Example 1.

[0140] Example 5

[0141] Example 5 describes a method for preparing mononitroaromatic hydrocarbons using a nitric-sulfur mixed acid:

[0142] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 45g of water to obtain 245g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 80%;

[0143] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 80% to obtain nitric acid mixed acid A;

[0144] (3) Heat the nitrate-sulfuric acid A and benzene to 120°C respectively, so that the benzene is completely vaporized into benzene vapor B;

[0145] (4) Nitrosulfuric acid A and benzene vapor B are fed into the microreactor at a flow rate of 2 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of benzene to nitric acid is 1.5. The residence time of the material in the microreactor is 20 s. After gas-liquid phase separation, a mixture of product mononitrobenzene and sulfuric acid solution is obtained.

[0146] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrobenzene product.

[0147] Test results:

[0148] The mononitrobenzene prepared in Example 5 was detected by liquid chromatography, and the selectivity of mononitrobenzene was 99.98%, the selectivity of dinitrobenzene was less than 0.02%, and the conversion rate of nitric acid was greater than 99.9%. The test conditions for liquid chromatography were the same as those in Example 1.

[0149] Example 6

[0150] Example 6 describes a method for preparing mononitroaromatic hydrocarbons using a nitric-sulfur mixed acid:

[0151] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 45g of water to obtain 245g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 80%;

[0152] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 80% to obtain nitric acid mixed acid A;

[0153] (3) Heat the nitrate-sulfuric acid A and benzene to 120°C respectively, so that the benzene is completely vaporized into benzene vapor B;

[0154] (4) Nitrosulfuric acid A and benzene vapor B are fed into the microreactor at a flow rate of 2 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of benzene to nitric acid is 1.5. The residence time of the material in the microreactor is 0.1 s. After gas-liquid phase separation, a mixture of mononitrobenzene and sulfuric acid solution is obtained.

[0155] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrobenzene product.

[0156] Test results:

[0157] The mononitrobenzene prepared in Example 6 was detected by liquid chromatography, and the selectivity of mononitrobenzene was 99.98%, the selectivity of dinitrobenzene was less than 0.02%, and the conversion rate of nitric acid was higher than 95%. The test conditions for liquid chromatography were the same as those in Example 1.

[0158] Example 7

[0159] Example 7 describes a method for preparing mononitroaromatic hydrocarbons using a nitric-sulfur mixed acid:

[0160] (1) Add 200g of concentrated sulfuric acid with a mass fraction of 98% to 45g of water to obtain 245g of sulfuric acid solution with a mass percentage concentration (i.e., mass fraction) of 80%;

[0161] (2) Add 1.48g of concentrated nitric acid with a mass fraction of 98% to a sulfuric acid solution with a mass percentage concentration of 80% to obtain nitric acid mixed acid A;

[0162] (3) Heat the nitrate-sulfuric acid A and benzene to 130°C respectively, so that the benzene is completely vaporized into benzene vapor B;

[0163] (4) Nitrosulfuric acid A and benzene vapor B are fed into the microreactor at a flow rate of 2 m / s. After the gas and liquid come into contact, a gas-liquid nitration reaction occurs. The molar ratio of benzene to nitric acid is 1.1. The residence time of the material in the microreactor is 20 s. After gas-liquid phase separation, a mixture of product mononitrobenzene and sulfuric acid solution is obtained.

[0164] (5) Cool the mixture solution to room temperature for 30 minutes, perform phase separation treatment, and wash the organic phase with alkali and water until the organic phase is neutral to obtain mononitrobenzene product.

[0165] Test results:

[0166] The mononitrobenzene prepared in Example 7 was detected by liquid chromatography, and the selectivity of mononitrobenzene was 99.95%, the selectivity of dinitrobenzene was less than 0.05%, and the conversion rate of nitric acid was higher than 95%. The test conditions for liquid chromatography were the same as those in Example 1.

[0167] In summary, the nitration method provided in this application can improve the selectivity of mononitroaromatics, which is far higher than that of liquid-liquid heterogeneous nitration reactions. It also reduces the formation of polynitroaromatics, and the nitric acid is almost completely consumed, facilitating the direct recycling of sulfuric acid after the reaction. Compared with liquid-liquid heterogeneous reactions in related technologies, this method improves mass transfer, shortens reaction time, and increases reaction efficiency. Furthermore, it yields high-purity mononitroaromatics immediately after separation, meeting Chinese national quality standards without the need for further purification.

[0168] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0169] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing mononitroaromatic hydrocarbons using a mixture of nitric and sulfuric acids, characterized in that, include: Preparation of a mixed acid of nitric acid and sulfuric acid; Gasification of aromatics to prepare gaseous aromatics; The gaseous aromatic hydrocarbon and the mixed acid are mixed in a preset ratio, and the mixed gaseous aromatic hydrocarbon and the mixed acid undergo a gas-liquid heterogeneous reaction at a first preset temperature to prepare the mononitro aromatic hydrocarbon; Wherein, the preset ratio satisfies the following: the molar ratio of nitric acid in the mixed acid to the gaseous aromatic hydrocarbon is 1:(1~2). The process of vaporizing aromatics to prepare gaseous aromatics includes: The aromatic hydrocarbon is heated to a second preset temperature to vaporize it into gaseous aromatic hydrocarbon; wherein the second preset temperature is greater than or equal to the boiling point temperature of the aromatic hydrocarbon and less than or equal to the sum of the boiling point temperature of the aromatic hydrocarbon and 100°C. The step of mixing the gaseous aromatic hydrocarbon and the mixed acid in a preset ratio, and causing the mixed gaseous aromatic hydrocarbon and the mixed acid to undergo a gas-liquid heterogeneous reaction at a first preset temperature, includes: The mixed acid is heated to the second preset temperature; The gaseous aromatic hydrocarbon and the mixed acid are mixed at a first flow rate and a second flow rate, respectively, and the mixed gaseous aromatic hydrocarbon and the mixed acid are brought into contact at a first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon; or, the gaseous aromatic hydrocarbon is bubbled into the mixed acid, and the gaseous aromatic hydrocarbon and the mixed acid are mixed under stirring, and after bubbling is completed, the mixed gaseous aromatic hydrocarbon and the mixed acid are kept at the first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon; Wherein, the first flow rate and the second flow rate satisfy the following: the molar ratio of the gaseous aromatic hydrocarbon and the mixed acid mixed per unit time satisfies the preset ratio.

2. The method according to claim 1, characterized in that, The preset time is 0.1s to 20s.

3. The method according to claim 1 or 2, characterized in that, In the case where the gaseous aromatic hydrocarbon and the mixed acid are mixed at a first flow rate and a second flow rate, respectively, and the mixed gaseous aromatic hydrocarbon and the mixed acid are contacted at a first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon, the mixing and reaction process of the gaseous aromatic hydrocarbon and the mixed acid is carried out in a continuous flow reactor.

4. The method according to claim 3, characterized in that, The continuous flow reactor is a static mixer, a microreactor, or a tubular reactor.

5. The method according to claim 1 or 2, characterized in that, In the case where the gaseous aromatic hydrocarbon is bubbled into the mixed acid and the gaseous aromatic hydrocarbon and the mixed acid are mixed under stirring, and after bubbling is completed, the mixed gaseous aromatic hydrocarbon and the mixed acid are kept at the first preset temperature for a preset time to react and generate the mononitro aromatic hydrocarbon, the mixing and reaction process of the gaseous aromatic hydrocarbon and the mixed acid is carried out in a batch reactor.

6. The method according to claim 1 or 2, characterized in that, The method further includes: The product after the gas-liquid heterogeneous reaction is subjected to phase separation treatment to prepare the mononitro aromatic hydrocarbon.

7. The method according to claim 6, characterized in that, The step of performing phase separation treatment on the products after the gas-liquid heterogeneous reaction to prepare the mononitroaromatic hydrocarbon includes: After the gaseous aromatic hydrocarbon and the mixed acid have been contacted at a first preset temperature for a preset time, the products resulting from the gas-liquid heterogeneous reaction are subjected to gas-liquid phase separation treatment; and The mixed solution obtained from gas-liquid phase separation is subjected to liquid-liquid phase separation, and the organic phase is collected.

8. The method according to claim 1 or 2, characterized in that, The preparation of the mixed acid of nitric acid and sulfuric acid includes: Concentrated sulfuric acid is diluted to prepare a sulfuric acid solution with a mass percentage concentration of 50% to 90%. The mixed acid is prepared by mixing fuming nitric acid and the sulfuric acid solution.

9. The method according to claim 8, characterized in that, The mass ratio of the fuming nitric acid to the sulfuric acid solution is 1:(100~1000).

10. The method according to claim 1 or 2, characterized in that, The aromatic hydrocarbon is benzene, toluene, chlorobenzene, xylene, ethylbenzene, naphthalene, or tetrahydronaphthalene.

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