Method and system for producing diphenylamine and phenothiazine from aniline

Abstract

The present invention relates to the technical field of organic synthesis, and discloses a method and system for producing diphenylamine and phenothiazine from aniline. The method includes the steps of reacting aniline raw material, separating the resulting diphenylamine-containing reaction mixture into gas and liquid to obtain a first liquid product and a first gas product, separating and processing the first liquid product to obtain aniline recovery material and diphenylamine product, reacting a part of the resulting diphenylamine product, separating the resulting phenothiazine-containing reaction mixture into gas and liquid to obtain a second liquid product and a second gas product, and separating the phenothiazine product from the second liquid product. In the present invention, by combining the diphenylamine synthesis process and the phenothiazine synthesis process, the thermal coupling of the two processes can be achieved, the energy consumption of the coupling process can be greatly reduced, the yield of the two products can be rationally controlled according to the market situation, and the purity of the diphenylamine product can be flexibly adjusted to optimize the product configuration.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of Chinese Patent Application No. 202210000026.0, filed on January 1, 2022, the contents of which are incorporated herein by reference. [Technical field]

[0002] The present invention relates to the technical field of organic synthesis, and in particular to a method and system for producing diphenylamine and phenothiazine from aniline. [Background technology]

[0003] Diphenylamine is an important organic chemical raw material with a wide range of applications, including industrial applications as an antioxidant for synthetic rubber, a stabilizer for explosives, a fuel and pharmaceutical intermediate, an azo dye, and a fruit preservative, as well as an analytical reagent and redox indicator for DNA identification and the colorimetric determination of nitrate, nitrite, chlorate, and magnesium.

[0004] Phenothiazine, also known as thiodiphenylamine, is an excellent polymerization inhibitor and a synthetic intermediate for fine chemicals such as pharmaceuticals and dyes. It is also used as a synthetic material auxiliary (polymerization inhibitor for vinylon production), a fruit tree insecticide, and a veterinary anthelmintic.

[0005] Chinese patent application CN105272860A discloses a method for continuously producing diphenylamine from aniline, in which aniline is used as a raw material and a fixed-bed catalytic reactor is used as a reaction vessel to synthesize diphenylamine through the action of a catalyst, and the reaction is carried out at a temperature of 200-380°C and a pressure of 2.5-4.0 MPa.

[0006] Chinese application CN105524016A discloses a method for synthesizing phenothiazine and / or its derivatives, which is characterized by comprising the steps of mixing diphenylamine and / or diphenylamine derivatives, sulfur and a solid acid catalyst, placing them under a protective atmosphere to allow them to react sufficiently, and then carrying out post-treatment to obtain phenothiazine and / or phenothiazine derivatives.

[0007] However, diphenylamine and phenothiazine production are currently carried out in two separate industrial plants. Diphenylamine has a wide range of uses, and the required product specifications and diphenylamine purity vary depending on the downstream product. However, the current industry standard for diphenylamine is a purity of 99.6% or higher. However, the diphenylamine required for the production of phenothiazine, a polymerization inhibitor, does not require a purity of 99.6% or higher. Purchasing diphenylamine with a purity of 99.6% or higher for the long term to synthesize phenothiazine not only increases raw material costs for phenothiazine production plants, but also requires all diphenylamine production plants to meet the 99.6% or higher standard. This results in high energy consumption and solid waste during product refining, resulting in unnecessary energy and material losses, which contradicts the country's strategic plan for carbon peaking and carbon neutrality. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a method and system for producing diphenylamine and phenothiazine from aniline. By combining a diphenylamine synthesis process with a phenothiazine synthesis process, the present invention not only allows for flexible adjustment of diphenylamine purity, reducing energy consumption during diphenylamine purification and solid waste generation, but also allows unreacted diphenylamine after vacuum distillation during phenothiazine production to be sent to the intermediate fraction column during diphenylamine production for impurity removal, eliminating the separation step in phenothiazine production and reducing energy consumption. Lower purity diphenylamine (98.0% or higher) can be used for phenothiazine production, allowing for rational control of the yields of the two products according to the price and demand of diphenylamine and phenothiazine products. Flexible adjustment of the purity of the diphenylamine product allows for optimization of product mix, significantly improving chemical companies' ability to withstand fluctuations in product prices. [Means for solving the problem]

[0009] The present invention provides (1) reacting an aniline raw material to obtain a reaction mixture containing diphenylamine; (2) subjecting the reaction mixture obtained in step (1) to gas-liquid separation to obtain a first liquid product and a first gas product; (3) separating and treating the first liquid product to obtain an aniline recovery material and a diphenylamine product; step (4) reacting a portion of the diphenylamine product obtained in step (3) to obtain a reaction mixture containing phenothiazine; and (5) subjecting the reaction mixture obtained in step (4) to gas-liquid separation to obtain a second liquid product and a second gas product, and separating the phenothiazine product from the second liquid product.

[0010] Preferably, in step (3), the separation treatment is a multi-stage rectification, and more preferably, the multi-stage rectification is a light fraction removal column for transporting the first liquid product to a light fraction removal column for rectification and discharging a light fraction from the top of the column; aniline recovery, wherein the bottom product of the light fraction removal column is transported to an aniline recovery column for rectification, and an aniline recovery material is collected from the top of the column, and a diphenylamine-containing stream is obtained at the bottom of the column; conveying said diphenylamine-containing stream to a middle fraction column for rectification, discharging a middle fraction from the top of the column and obtaining a diphenylamine-rich stream at the bottom of the column; and removing a middle fraction. diphenylamine product fractionation, in which the diphenylamine-rich stream is transported to a diphenylamine product column for fractionation, and diphenylamine products of different purity are obtained from the top and side lines, respectively, and a heavy fraction is discharged from the bottom of the column.

[0011] Preferably, a diphenylamine-qualified product is obtained from the top of the diphenylamine product column, and a high-grade diphenylamine product is obtained from the side line of the diphenylamine product column, and the purity of the diphenylamine-qualified product is 98 wt% or more, and the purity of the high-grade diphenylamine product is 99.6 wt% or more, and more preferably, the diphenylamine-qualified product is used as the reaction raw material for step (4).

[0012] Preferably, the aniline recovery material obtained in step (3) is reused as the aniline raw material.

[0013] Preferably, in step (5), the process of separating the phenothiazine product from the second liquid product comprises sequentially subjecting the second liquid product to adsorption removal of impurities and vacuum distillation.

[0014] More preferably, the diphenylamine-rich light fraction obtained in the vacuum distillation process is transported to the intermediate fraction column for rectification.

[0015] Preferably, the first gas product obtained in step (2) and the second gas product obtained in step (5) are mixed and purified.

[0016] The present invention also provides a first reactor in which the aniline raw material undergoes a reaction; a first gas-liquid separator for separating the reaction mixture obtained in the first reactor into gas and liquid to obtain a first liquid product and a first gas product; a first product separation device for separating and treating the first liquid product separated in the first gas-liquid separation device to obtain an aniline recovery material and a diphenylamine product; a second reactor for reacting a portion of the diphenylamine product from the first product separation device in a second reactor; a second gas-liquid separator for separating the reaction mixture obtained in the second reactor into gas and liquid to obtain a second liquid product and a second gas product; a second product separation device for separating the phenothiazine product from the second liquid product separated in the second gas-liquid separation device.

[0017] Preferably, the first product separation device is a multi-stage rectification device. More preferably, the multi-stage rectification device is a light fraction removal column for rectifying the first liquid product separated in the first gas-liquid separation device and discharging a light fraction from a column top; an aniline recovery column for rectifying the product from the bottom of the light fraction removal column, collecting aniline recovery material from the top of the column, and obtaining a diphenylamine-containing stream at the bottom of the column; an intermediate fraction column for rectifying the diphenylamine-containing stream from the aniline recovery column to discharge an intermediate fraction from the top of the column and obtain a diphenylamine-rich stream at the bottom of the column; a diphenylamine product column for rectifying the diphenylamine-rich stream from the intermediate fraction column to obtain diphenylamine products of different purity from the top and side line, respectively, and discharging a heavy fraction from the bottom of the column. [Effects of the Invention]

[0018] Compared with the prior art, the method and system for producing diphenylamine and phenothiazine from aniline of the present invention have the following advantages:

[0019] 1. Existing phenothiazine production equipment all employs kettle-type intermittent operation, and no continuous production equipment exists for the following two reasons: (1) Market demand is stable, and intermittent operation can meet market requirements; (2) Continuous operation inevitably leads to a decrease in conversion rate, necessitating the addition of related equipment such as a rectification column to recover diphenylamine, which is uneconomical. In this invention, the phenothiazine production process is integrated into the diphenylamine synthesis process, enabling large-scale continuous phenothiazine production and optimizing the phenothiazine production route while appropriately relaxing the product fractionation accuracy requirements in the diphenylamine synthesis process. High-quality diphenylamine (purity 99.6 wt% or higher) can be sent externally as a product, while qualified diphenylamine (purity 98 wt% or higher) can be directly transported to phenothiazine production for further reaction. This reduces the energy consumption of the rectification column for diphenylamine product and also meets the raw material requirements for diphenylamine in the phenothiazine production process. In addition, the heat carried by the diphenylamine product also provides a heat source for the reaction of producing phenothiazine from diphenylamine, thereby reducing the energy consumption of the phenothiazine production process. Therefore, the combined process of the present invention can realize the thermal coupling of the two processes and can significantly reduce the energy consumption of the combined process.

[0020] 2. In the diphenylamine synthesis process, high conversion and selectivity are achieved in the early stages of the reaction, resulting in low intermediate fraction production. By the end of the reaction, conversion and selectivity drop significantly, and the intermediate fraction content increases significantly. Considering the product separation effect from the middle stage of the reaction onward, the feed position of the aniline tower bottom material to the intermediate fraction tower cannot be set too high. As a result, the feed to the intermediate fraction tower fluctuates significantly in the early stages of the reaction, making operation difficult. Furthermore, because solid acid catalysts are typically used in the phenothiazine production process, the high catalytic activity and high conversion rate result in suboptimal selectivity in the early stages of continuous production, resulting in the production of a large number of intermediate fractions. From the middle stage of the reaction onward, catalytic activity stabilizes, selectivity gradually increases, and the intermediate fraction content tends to decrease. Considering the product separation effect in the early stages of the reaction, the feed position of the aniline tower bottom material to the intermediate fraction tower must not be set too low. As a result, operation of the intermediate fraction tower is difficult from the middle stage of the reaction onward. When the phenothiazine production process is integrated into the diphenylamine synthesis process, the bottom material of the aniline tower is mixed with the material of the intermediate fraction tower and mixed with the diphenylamine-rich material sent from the top of the vacuum distillation tower during the production of phenothiazine, so that the material entering the intermediate fraction tower has a relatively stable composition (i.e., the diphenylamine content is relatively stable) throughout the entire operating cycle, which reduces operational fluctuations of the intermediate fraction tower and allows it to operate stably, making it easier to operate.

[0021] 3. The process of the present invention can rationally control the yields of diphenylamine product and phenothiazine product according to the market price and market demand of these two products, and flexibly adjust the purity of diphenylamine product, thereby optimizing the product composition of the combined process, which greatly improves the ability of chemical companies to withstand product price fluctuations.

[0022] 4. Ammonia gas generated during the production of diphenylamine is an alkaline gas, and hydrogen sulfide gas generated during the production of phenothiazine is an acidic gas. Therefore, washing these two exhaust gases with water simultaneously neutralizes each other. This reduces the amount of acid and alkali purchased for acid absorption and alkali absorption, and also reduces wastewater discharge. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram of a process flow for producing diphenylamine and phenothiazine from aniline according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the specific embodiments described herein are merely for the purpose of explaining and interpreting the present invention, and are not intended to limit the present invention.

[0025] The method of producing diphenylamine and phenothiazine from aniline of the present invention comprises the steps of: (1) reacting an aniline raw material to obtain a reaction mixture containing diphenylamine; (2) subjecting the reaction mixture obtained in step (1) to gas-liquid separation to obtain a first liquid product and a first gas product; (3) separating and treating the first liquid product to obtain an aniline recovery material and a diphenylamine product; step (4) reacting a portion of the diphenylamine product obtained in step (3) to obtain a reaction mixture containing phenothiazine; and (5) subjecting the reaction mixture obtained in step (4) to gas-liquid separation to obtain a second liquid product and a second gas product, and separating the phenothiazine product from the second liquid product.

[0026] In step (1), the reaction converts aniline into diphenylamine. The specific reaction formula is shown in formula (1). The main product is diphenylamine, and the by-products are mainly ammonia gas, 2-methylpyridine, 2-ethylaniline, quinoline, indole, acridine, etc.

[0027] [ka]

[0028] The reaction conditions for producing diphenylamine from aniline are: reaction temperature 250-380°C, pressure 1-8 MPa, liquid hourly space velocity 0.05-1 h -1 In this specification, pressure refers to absolute pressure.

[0029] The parameter index of the aniline raw material for producing diphenylamine from aniline may be as shown in Table 1, and the parameter index of the recyclable aniline raw material may be as shown in Table 2.

[0030] [Table 1]

[0031] [Table 2]

[0032] In the reaction of step (1), the catalyst used may be at least one of a β molecular sieve catalyst, a Y molecular sieve catalyst, an X molecular sieve catalyst, mordenite, and ZSM-5. Preferably, the catalyst used is a β molecular sieve catalyst. The β molecular sieve catalyst may be one commonly used in the art. In a preferred embodiment, based on the total weight of the β molecular sieve catalyst, the β molecular sieve catalyst contains 50-95 wt% of β molecular sieve and 5-50 wt% of γ-Al2O3. More preferably, the β molecular sieve catalyst contains 60-90 wt% of β molecular sieve and 10-40 wt% of γ-Al2O3. In the β molecular sieve catalyst, the SiO2 / Al2O3 molar ratio of the β molecular sieve may be 20-100, preferably 28-68.

[0033] In the process of the present invention, the reaction in step (1) may be a continuous or batch operation, but is preferably a continuous operation.

[0034] When the reaction for producing diphenylamine from aniline is a continuous operation, the reaction conditions for the continuous operation are a reaction pressure of 1 to 8 MPa, preferably 2 to 6 MPa, a reaction temperature of 250 to 380°C, preferably 280 to 360°C, and a liquid hourly space velocity of 0.05 to 1 h -1 , preferably 0.1 to 0.5 hours -1 may include:

[0035] In the method of the present invention, the reaction in step (1) is preferably carried out in the presence of a protective gas, which is preferably nitrogen gas and / or hydrogen gas.

[0036] When a protective gas is introduced during the reaction in step (1), the volume ratio of the protective gas to the aniline raw material may be 10-1000:1, but is preferably 50-500:1.

[0037] When a protective gas is introduced during the reaction in step (1), the method of the present invention may further include a step of purifying (e.g., pickling) the first gas product obtained by gas-liquid separation in step (2), and then reusing the purified gas as a source of protective gas.

[0038] In the method of the present invention, the gas-liquid separation in step (2) may be carried out in a gas-liquid separation device (e.g., a gas-liquid separation column) commonly used in the art, and the first liquid product is extracted from the bottom of the column and the first gas product is extracted from the top of the column. The first liquid product contains unreacted aniline, diphenylamine, and other by-products. The first gas product mainly contains ammonia gas and protective gas.

[0039] In the method of the present invention, preferably, in step (3), the separation treatment is a multi-stage rectification. More preferably, the multi-stage rectification is a light fraction removal column for transporting the first liquid product to a light fraction removal column for rectification and discharging a light fraction from the top of the column; aniline recovery, wherein the bottom product of the light fraction removal column is transported to an aniline recovery column for rectification, and an aniline recovery material is collected from the top of the column, and a diphenylamine-containing stream is obtained at the bottom of the column; conveying said diphenylamine-containing stream to a middle fraction column for rectification, discharging a middle fraction from the top of the column and obtaining a diphenylamine-rich stream at the bottom of the column; and removing a middle fraction. diphenylamine product fractionation, in which the diphenylamine-rich stream is transported to a diphenylamine product column for fractionation, and diphenylamine products of different purity are obtained from the top and side lines, respectively, and a heavy fraction is discharged from the bottom of the column.

[0040] In the rectification of the diphenylamine product, a diphenylamine-qualified product is obtained from the top of the diphenylamine product column, and a diphenylamine-enhanced product is obtained from the side line of the diphenylamine product column, and the purity of the diphenylamine-qualified product is 98 wt% or more, and the purity of the diphenylamine-enhanced product is 99.6 wt% or more.

[0041] In a specific embodiment, the diphenylamine grade is used as the reactant in step (4). If necessary, the diphenylamine grade may be used as the reactant in at least part of step (4).

[0042] In a preferred embodiment of the present invention, the method may further include a step of reusing the aniline recovery material obtained in step (3) as the aniline raw material. The specific operation is as follows: The aniline recovery material collected at the top of the aniline recovery column is transported to an aniline raw material tank for supplying aniline raw material, and used as reaction raw materials for the reaction in step (1) together with fresh aniline raw material.

[0043] In step (4), the reaction converts diphenylamine into phenothiazine, and the reaction is carried out in the presence of a sulfur-containing substance, which may be at least one selected from sulfur, sodium sulfide, carbon disulfide, and sulfur dioxide. Preferably, the sulfur-containing substance is sulfur.

[0044] When the sulfur-containing substance used in the reaction in step (4) is sulfur, the specific reaction scheme is shown in Scheme (2), the main product is phenothiazine, and the by-products are large molecular weight thiols and thioethers whose substituents are diphenylamine or phenothiazine.

[0045] [ka]

[0046] The reaction conditions for producing phenothiazine from diphenylamine may include a reaction temperature of 130 to 250° C. and a pressure of 5 to 101 kPa in the presence of a catalyst (for example, iodine tablets).

[0047] The parameter index of the diphenylamine feedstock for producing phenothiazine from diphenylamine may be as shown in Table 3.

[0048] [Table 3]

[0049] In the reaction of step (4), the catalyst used is a catalyst commonly used in the art for synthesizing phenothiazine from diphenylamine. In a preferred embodiment, the catalyst is at least one selected from iodine tablets, anhydrous aluminum trichloride, and a solid acid catalyst, more preferably a solid acid catalyst.

[0050] In the method of the present invention, the reaction in step (4) may be a continuous operation or a batch operation. The reaction conditions for a continuous operation are a reaction pressure of 5 to 101 kPa, preferably 50 to 101 kPa, a reaction temperature of 130 to 250°C, preferably 160 to 220°C, and a liquid hourly space velocity of 0.1 to 2 h -1 , preferably 0.1 to 0.5 hours -1The reaction conditions for the intermittent operation may include a reaction pressure of 5 to 101 kPa, preferably 50 to 101 kPa, a reaction temperature of 130 to 250°C, preferably 160 to 220°C, and a reaction time of 2 to 10 hours, preferably 4 to 8 hours.

[0051] In the method of the present invention, the reaction in step (4) is preferably carried out in the presence of a protective gas, which is preferably nitrogen gas and / or hydrogen gas.

[0052] When a protective gas is introduced during the reaction in step (4), the volume ratio of the protective gas to the diphenylamine raw material may be 5-500:1, but is preferably 10-100:1.

[0053] If a protective gas is introduced during the reaction in step (4), the method of the present invention may further include a step of purifying the second gas product obtained by gas-liquid separation in step (5) (e.g., alkaline washing), and then reusing the purified gas as a source of protective gas.

[0054] In the method of the present invention, ammonia gas generated during the production of diphenylamine is an alkaline gas, and hydrogen sulfide generated during the production of phenothiazine is an acidic gas. Therefore, these two exhaust gases can be neutralized by simultaneously washing them with water. This reduces the amount of acid or alkali purchased for acid absorption or alkali absorption, and also reduces the amount of wastewater discharged. Therefore, in a preferred embodiment, the first gas product obtained in step (2) and the second gas product obtained in step (5) are mixed and purified (e.g., washed with water).

[0055] When a protective gas is introduced into the reaction system in step (1) and / or step (4), it is more preferable to mix and purify the first gas product obtained in step (2) and the second gas product obtained in step (5), and then reuse the purified gas as a protective gas source, and if necessary, increase the pressure of the purified gas to an appropriate level using a gas compressor and reuse it.

[0056] In the method of the present invention, the gas-liquid separation in step (5) can be carried out in a gas-liquid separation device (e.g., a gas-liquid separation column) commonly used in the art, and the second liquid product is withdrawn from the bottom of the column and the second gas product is withdrawn from the top of the column. The second liquid product contains unreacted diphenylamine, phenothiazine, and other by-products. The second gas product mainly contains hydrogen sulfide and protective gas.

[0057] In the method of the present invention, preferably, in step (5), the process of separating the phenothiazine product from the second liquid product comprises sequentially subjecting the second liquid product to adsorption impurity removal and vacuum distillation. More preferably, the method of producing diphenylamine and phenothiazine from aniline of the present invention may comprise a step of transporting the diphenylamine-rich light fraction obtained in the vacuum distillation process to the intermediate fraction column for rectification, thereby realizing the recovery and reuse of unreacted diphenylamine.

[0058] In the present invention, the purpose of the adsorption and decontamination is to perform adsorption and decontamination, particularly adsorption and decolorization, on the second liquid product obtained in the gas-liquid separation process. The adsorbent packed in the adsorption and decontamination device is a conventional adsorbent or adsorption filler used in the art, preferably activated carbon. In intermittent operation, the adsorption and decontamination device is an adsorption vessel, while in continuous operation, the adsorption and decontamination device may include an adsorption and decontamination tank or an adsorption and decontamination tower. The adsorption and decontamination device is typically operated by switching between A / B boilers or A / B towers, i.e., impurities are removed from one tower while the adsorbent is regenerated in the other tower.

[0059] In the present invention, the vacuum distillation can be carried out according to a conventional method in the art. In a specific embodiment, the vacuum distillation can be carried out in a still.

[0060] As shown in FIG. 1, the system for producing diphenylamine and phenothiazine from aniline of the present invention includes: a first reactor 100 in which a reaction of an aniline raw material is carried out to produce diphenylamine from aniline; a first gas-liquid separator (200) for separating the reaction mixture obtained in the first reactor (100) into gas and liquid to obtain a first liquid product and a first gas product; a first product separation device (300) for separating and treating the first liquid product separated in the first gas-liquid separation device (200) to obtain an aniline recovery material and a diphenylamine product; a second reactor 400 in which a reaction is carried out in which a portion of the diphenylamine product from the first product separation device 300 and sulfur are reacted to produce phenothiazine from diphenylamine; a second gas-liquid separator (500) for separating the reaction mixture obtained in the second reactor (400) into gas and liquid to obtain a second liquid product and a second gas product; and a second product separation device 600 for separating a phenothiazine product from the second liquid product separated in the second gas-liquid separation device 500.

[0061] In the system of the present invention, the first product separation unit 300 is preferably a multi-stage rectification unit. In a preferred embodiment, the multi-stage rectification unit comprises: a light fraction removal column 310 for rectifying the first liquid product separated in the first gas-liquid separation device 200 and discharging a light fraction from the top of the column; an aniline recovery column 320 for rectifying the product from the bottom of the light fraction removal column 310, collecting aniline recovery material from the top, and obtaining a diphenylamine-containing stream at the bottom; an intermediate fraction column 330 for rectifying the diphenylamine-containing stream from the aniline recovery column 320 to obtain an intermediate fraction at the top and a diphenylamine-rich stream at the bottom; and a diphenylamine product column 340 for rectifying the diphenylamine-rich stream from the intermediate fraction column 330 to obtain diphenylamine products of different purity from the top and side line, respectively, and discharging a heavy fraction from the bottom.

[0062] More preferably, the diphenylamine product column 340 is provided at the top with a diphenylamine-qualified product transport pipeline 341 for delivering diphenylamine-qualified products, and at the side of the column is provided a diphenylamine-qualified product transport pipeline 342 for collecting diphenylamine-qualified products, and the diphenylamine-qualified product transport pipeline 341 is connected to the diphenylamine raw material supply port of the second reactor 400.

[0063] More preferably, the second product separation device 600 comprises: an adsorption / de-impurity device 610 for adsorbing and de-impurifying the second liquid product separated in the second gas-liquid separation device 500; and a vacuum distillation unit 620 for vacuum distilling the liquid product treated in the adsorption impurity removal unit 610 to obtain a diphenylamine-rich light fraction and a phenothiazine product.

[0064] More preferably, a diphenylamine-rich material transport pipeline 621 is provided at the top of the vacuum distillation apparatus 620 for delivering a diphenylamine-rich light fraction, and the diphenylamine-rich material transport pipeline 621 is connected to the diphenylamine-containing stream supply port of the intermediate fraction column 330.

[0065] More preferably, the system further includes an exhaust purification device 800, and a first gas product transport pipeline 201 provided at the top of the first gas-liquid separation device 200 and a second gas product transport pipeline 501 provided at the top of the second gas-liquid separation device 500 are connected to the exhaust purification device 800.

[0066] More preferably, a purified gas delivery pipeline 801 is provided at the gas delivery end of the exhaust purification device 800, and the purified gas delivery pipeline 801 is connected to the gas inlet of the second reactor 400, and delivers the purified gas (mainly protective gas, for example, nitrogen gas and / or hydrogen gas) into the second reactor 400 as a protective gas source; alternatively, the purified gas delivery pipeline 801 may be connected to the compression target gas input pipeline 701 of the gas compressor 700, and the purified gas is pressurized to the reaction pressure and delivered to the first reactor 100 via the compressed gas delivery pipeline 702.

[0067] More preferably, an aniline recovery material transport pipeline 321 is provided at the top of the aniline recovery tower 320, and the aniline recovery material transport pipeline 321 is connected to an aniline raw material tank 900, so that the aniline recovery material collected in the aniline recovery tower 320 is transported to the aniline raw material tank 900 for reuse. The aniline raw material tank 900 is further provided with a new aniline pipeline 901 for supplying new aniline raw material to the aniline raw material tank 900. A raw material discharge pipeline 902 of the aniline raw material tank 900 is connected to the supply pipeline 101 of the first reactor 100.

[0068] In a specific embodiment, as shown in FIG. 1 , the system for producing diphenylamine and phenothiazine from aniline includes a first reactor 100, a first gas-liquid separation device 200, a multi-stage rectification device, a second reactor 400, a second gas-liquid separation device 500, an adsorption impurity removal device 610, and a vacuum distillation device 620, wherein the multi-stage rectification device includes a light fraction removal column 310, an aniline recovery column 320, an intermediate fraction column 330, and a diphenylamine product column 340. The aniline raw material is charged into the first reactor 100 through a first supply pipeline 101, the reaction mixture is transported through a first discharge pipeline 102 to a first gas-liquid separator 200 for gas-liquid separation, the first gas product obtained by the gas-liquid separation is transported through a first gas product transport pipeline 201 to an exhaust purification device 800 for purification, the resulting first liquid product is transported through a first liquid product transport pipeline 202 to a light fraction removal column 310 for rectification, the resulting light fraction is discharged through a light fraction transport pipeline 311 at the top of the column, the bottom product is transported through a bottom product transport pipeline 312 to an aniline recovery column 320 for rectification, and the aniline recovery material collected at the top of the column is transported to an aniline raw material tank 900 through an aniline recovery material transport pipeline 321. The diphenylamine-containing bottom stream is transported via diphenylamine-containing stream transport pipeline 322 to intermediate fraction column 330 for rectification, and the resulting intermediate fraction is discharged via intermediate fraction transport pipeline 331 at the top of the column; the diphenylamine-rich bottom stream is transported via diphenylamine-rich stream transport pipeline 332 to diphenylamine product column 340 for rectification, and the heavy bottom fraction is discharged via first heavy fraction discharge pipeline 343.The diphenylamine high-grade products collected through the side line are transported through the diphenylamine high-grade product collecting pipeline 342, the overhead diphenylamine high-grade products are transported through the diphenylamine high-grade product transport pipeline 341 to the second feed pipeline 401 of the second reactor 400 and enter the second reactor 400, and the reactant sulfur is transported through the sulfur supply pipeline 403 to the second reactor 400 for reaction. The resulting reaction mixture is transported through the second delivery pipeline 402 to the second gas-liquid separation device 500 for gas-liquid separation. The second gas product obtained by gas-liquid separation is transported through the second gas product transport pipeline 501 to the exhaust purification device 800 for purification. The resulting second liquid product is transported through the second liquid product transport pipeline 502 to the adsorption impurity removal device 610 for adsorption to remove impurities. The material from which the impurities have been removed by adsorption is transported through the third delivery pipeline 611 to the vacuum distillation device 620 for vacuum distillation. The diphenylamine-rich light fraction collected at the top of the column is transported to the intermediate fraction column 330 via a diphenylamine-rich material transport pipeline 621 for reuse, the phenothiazine product collected via a side line is sent out via a phenothiazine product collection pipeline 622, and the heavy fraction at the bottom of the column is discharged via a second heavy fraction sending pipeline 623.

[0069] In the system of the present invention, each pipeline may be preferably provided with a valve such as a back pressure valve, a shutoff valve, or a one-way valve as necessary. The arrangement of the back pressure valve, the shutoff valve, and the one-way valve is well known to those skilled in the art, so they will not be described in detail here.

[0070] The method and system for producing diphenylamine and phenothiazine from aniline of the present invention will be further described below with reference to examples. The examples are carried out based on the technical solution of the present invention, and provide detailed embodiments and specific operating procedures, but the scope of protection of the present invention is not limited to the following examples.

[0071] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods in the art. Unless otherwise specified, all experimental materials used in the following examples can be purchased from biochemical reagent stores.

[0072] The specifications of the aniline raw materials used in the following examples and comparative examples are shown in Table 1 and conform to GB / T 2961-2014 standard.

[0073] The purity of the nitrogen gas used exceeds 99.9v%.

[0074] The beta molecular sieve catalyst used for the continuous synthesis of diphenylamine from aniline is grade DA-30, with a beta molecular sieve content of 73.3 wt% (silica / alumina ratio of 30) and a gamma-Al2O3 content of 26.7 wt%. Its physical properties are shown in Table 4.

[0075] [Table 4]

[0076] The catalyst used to synthesize phenothiazine from diphenylamine is a conventional solid phosphoric acid catalyst.

[0077] The sulfur used to synthesize phenothiazine from diphenylamine is of industrial grade. Comparative Example 1

[0078] In Comparative Example 1, the apparatus for producing diphenylamine from aniline and the apparatus for producing phenothiazine from diphenylamine are two separate apparatuses that are not combined.

[0079] To produce diphenylamine from aniline, aniline and nitrogen gas enter the reactor from the bottom and pass through a fixed-bed reactor. The reactor is packed with a β molecular sieve catalyst. The process conditions and reaction results are shown in Table 5.

[0080] When producing phenothiazine from diphenylamine, diphenylamine and nitrogen gas enter a fixed-bed reactor and react with a solid acid catalyst. The process conditions and reaction results are shown in Table 5.

[0081] [Table 5] Examples 1 to 4

[0082] The operation procedure of the embodiment is as follows:

[0083] (1) Continuous production of diphenylamine from aniline As shown in Figure 1, in the presence of a β molecular sieve catalyst, nitrogen gas is passed through a nitrogen gas compressor and introduced into the first reactor 100 together with the reaction raw material aniline via respective pipelines. After reaction, the mixture is removed from the first reactor 100, cooled, and then introduced into the first gas-liquid separator for gas-liquid separation. The separated ammonia-containing nitrogen gas is purified and returned to the nitrogen gas compressor. The separated liquid product is introduced into the light fraction removal column 310, where light fractions such as 2-methylpyridine are evaporated from the top of the column. The bottom liquid is sent to the aniline recovery column 320. In the aniline recovery column 320, excess aniline is evaporated from the top and recycled to the reaction system, and the bottom liquid is sent to the intermediate fraction column 330. In the intermediate fraction column 330, intermediate fractions such as ethylaniline are evaporated from the top of the column, and the bottom liquid is fed to the diphenylamine product column 340, where diphenylamine-grade products (purity of 98 wt. % or more) are withdrawn from the top of the column, high-grade diphenylamine products (purity of 99.6 wt. % or more) are withdrawn from the side line, and the heavy fraction is retained in the bottom liquid.

[0084] (2) Production of phenothiazine from diphenylamine As shown in Figure 1, diphenylamine-eligible products and nitrogen gas are introduced into the second reactor 400 (fixed-bed reactor) via their respective pipelines in the presence of a solid phosphoric acid catalyst and reacted therein. The reaction mixture is removed, cooled, and then introduced into the second gas-liquid separator for gas-liquid separation. The separated hydrogen sulfide-containing nitrogen gas is purified and reused as an exhaust, and the separated liquid product is sent to an adsorption / impurity removal tower. The adsorption / impurity removal tower undergoes a decolorization treatment and then enters a vacuum distillation tower. In the vacuum distillation tower, unreacted diphenylamine and the resulting intermediate fraction are evaporated from the top of the tower. The product phenothiazine is withdrawn from the sideline, and the heavy fraction is retained in the bottom liquid.

[0085] In Example 1, unreacted diphenylamine evaporated from the vacuum distillation column in the process of producing phenothiazine from diphenylamine is treated and then returned to the second reactor 400. The process conditions and reaction results are shown in Table 6.

[0086] In Example 2, unreacted diphenylamine evaporated from a vacuum distillation column in the process of producing phenothiazine from diphenylamine is sent to an intermediate fraction column 330 in the process of synthesizing diphenylamine from aniline, where diphenylamine is purified and recovered. The process conditions and reaction results are shown in Table 6.

[0087] In Examples 3 and 4, unreacted diphenylamine evaporated from the vacuum distillation column in the process of producing phenothiazine from diphenylamine is sent to the intermediate fraction column 330 in the process of synthesizing diphenylamine from aniline, where diphenylamine is purified and recovered. The process conditions and reaction results are shown in Table 7.

[0088] [Table 6]

[0089] [Table 7]

[0090] The results of Examples 1 to 4 showed that when the diphenylamine-qualified product (purity 98.0 wt.% or higher) produced during the synthesis of diphenylamine is used as a diphenylamine raw material during the production of phenothiazine, it does not affect the reaction. Furthermore, by transporting unreacted diphenylamine during the production of phenothiazine to the intermediate fraction column in the diphenylamine production and recovering the diphenylamine, continuous production is achieved, operation is simplified, and reaction efficiency is significantly improved. Furthermore, based on the data on the total amount of diphenylamine in the intermediate fraction column, the proportion of the total amount of diphenylamine treated in the intermediate fraction column in Example 1 was 95.58 wt.% after 30 days of operation, 95.30 wt.% after 80 days of operation, and 95.05 wt.% after 120 days of operation. The percentage of the total amount of diphenylamine treated in the intermediate fraction column in Example 2 was 95.74 wt% after 30 days of operation, 95.69 wt% after 80 days of operation, and 95.53 wt% after 120 days of operation. Although the change is only small in one decimal place, in the case of industrial equipment, the throughput is huge, so even a change of one decimal place can significantly affect the absolute amount of material. This indicates that unreacted diphenylamine in phenothiazine production is transported to the intermediate fraction column in diphenylamine production, and that the intermediate fraction column during diphenylamine production operates stably throughout the entire cycle. Furthermore, because the purity of the diphenylamine raw material used in phenothiazine production is relaxed, the product column in diphenylamine synthesis is also relatively stable, and the diphenylamine product does not have to be discharged outside due to unsuitable conditions after a certain period of operation. This reduces the energy consumption of the equipment and improves its economic efficiency.

[0091] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining each technical feature in other appropriate ways, and these simple modifications and combinations should also be considered as the contents disclosed in the present invention, and all fall within the protection scope of the present invention. [Explanation of symbols]

[0092] 100 First reactor 101 First Supply Pipeline 102 First Outlet Pipeline 200 1st gas-liquid separation device 201 First Gas Product Transport Pipeline 202 No. 1 Liquid Product Transport Pipeline 300 1st product separation device 310 Light fraction removal tower 311 Light Fraction Transportation Pipeline 312 Column bottom product transport pipeline 320 Aniline Recovery Tower 321 Aniline recovered material transport pipeline 322 Diphenylamine-containing fluid transport pipeline 330 Intermediate Fraction Column 331 Intermediate fraction transportation pipelines 332 Diphenylamine-rich flow transport pipeline 340 Diphenylamine product tower 341 Diphenylamine Eligible Goods Transportation Pipeline 342 Diphenylamine Luxury Goods Collection Pipeline 343 First Heavy Fraction Delivery Pipeline 400 Second Reactor 401 Second Supply Pipeline 402 Second Outlet Pipeline 403 Sulfur Supply Pipeline 500 Second gas-liquid separation device 501 Second Gas Product Transmission Pipeline 502 Second Liquid Product Transport Pipeline 600 Second product separation device 610 Adsorption and de-impurity equipment 611 Third Outlet Pipeline 620 Vacuum distillation apparatus 621 Diphenylamine-rich material transport pipeline 622 Phenothiazine Product Collection Pipeline 623 Second Heavy Fraction Delivery Pipeline 700 Gas Compressor 701 Compressed gas input pipeline 702 Compressed gas transmission pipelines 800 Exhaust purification device 801 Purified gas delivery pipeline 900 Aniline raw material tank 901 New Aniline Pipeline 902 Raw material delivery pipeline

Claims

1. A process for producing diphenylamine and phenothiazine from aniline, comprising the steps of: (1) reacting an aniline raw material to obtain a reaction mixture containing diphenylamine; (2) subjecting the reaction mixture obtained in step (1) to gas-liquid separation to obtain a first liquid product and a first gas product; (3) separating and treating the first liquid product to obtain an aniline recovery material and a diphenylamine product; step (4) reacting a portion of the diphenylamine product obtained in step (3) to obtain a reaction mixture containing phenothiazine; and (5) subjecting the reaction mixture obtained in step (4) to gas-liquid separation to obtain a second liquid product and a second gas product, and separating the phenothiazine product from the second liquid product; In step (3), the separation treatment is a multi-stage rectification; The multi-stage rectification a light fraction removal column for transporting the first liquid product to a light fraction removal column for rectification and discharging a light fraction from the top of the column; aniline recovery, wherein the bottom product of the light fraction removal column is transported to an aniline recovery column for rectification, and an aniline recovery material is collected from the top of the column, and a diphenylamine-containing stream is obtained at the bottom of the column; conveying said diphenylamine-containing stream to a middle fraction column for rectification, discharging a middle fraction from the top of the column and obtaining a diphenylamine-rich stream at the bottom of the column; and removing a middle fraction. diphenylamine product fractionation, in which the diphenylamine-rich stream is transported to a diphenylamine product column for fractionation, to obtain diphenylamine products of different purity from the top and side of the column, respectively, and to discharge a heavy fraction from the bottom of the column; In step (5), the process of separating the phenothiazine product from the second liquid product comprises sequentially subjecting the second liquid product to adsorption / de-impurity treatment and vacuum distillation; The diphenylamine-rich light fraction obtained in the vacuum distillation step is transported to the intermediate fraction column for rectification.

2. 2. The method of claim 1, wherein the catalyst used in the reaction of step (1) is at least one of a β molecular sieve catalyst, a Y molecular sieve catalyst, an X molecular sieve catalyst, mordenite, and ZSM-5.

3. 3. The method of claim 2, wherein the catalyst used in the reaction of step (1) is a beta molecular sieve catalyst.

4. The method according to claim 3, characterized in that the β molecular sieve catalyst contains 50 to 95 wt% of β molecular sieve and 5 to 50 wt% of γ-Al 2 O 3 based on the total weight of the β molecular sieve catalyst, and the SiO 2 / Al 2 O 3 molar ratio of the β molecular sieve is 20 to 100.

5. The method according to any one of claims 1 to 3, wherein the reaction in step (1) is a continuous operation or an intermittent operation.

6. The method according to claim 5, wherein in step (1), the reaction conditions for continuous operation include a reaction pressure of 1-8 MPa, a reaction temperature of 250-380°C, and a liquid hourly space velocity of 0.05-1 h-1.

7. 4. The method according to claim 1, wherein the reaction in step (1) is carried out in the presence of a protective gas, and the volume ratio of the protective gas to the aniline raw material is 10-1000:

1.

8. 2. The method of claim 1, wherein a diphenylamine grade is obtained from the top of the diphenylamine product column and a diphenylamine premium is obtained from a side line of the diphenylamine product column, the purity of the diphenylamine grade is 98 wt% or greater, and the purity of the diphenylamine premium is 99.6 wt% or greater.

9. The method described in claim 8, characterized in that the diphenylamine-qualified product is used as the reaction raw material in step (4).

10. 10. The method according to claim 1 or 8, wherein the aniline recovery material obtained in step (3) is reused as the aniline raw material.

11. 2. The method of claim 1, wherein in step (4), the reaction is carried out in the presence of a sulfur-containing substance, and the sulfur-containing substance is at least one selected from sulfur, sodium sulfide, carbon disulfide, and sulfur dioxide.

12. 12. The method according to claim 1 or 11, wherein in the reaction of step (4), the catalyst used is at least one selected from iodine tablets, anhydrous aluminum trichloride, and solid acid catalysts.

13. 12. The method according to claim 1 or 11, wherein in step (4), the reaction conditions for continuous operation include a reaction pressure of 5 to 101 kPa, a reaction temperature of 130 to 250°C, and a liquid hourly space velocity of 0.1 to 2 h-1.

14. 12. The method according to claim 1 or 11, wherein in step (4), the reaction conditions for the intermittent operation include a reaction pressure of 5 to 101 kPa, a reaction temperature of 130 to 250°C, and a reaction time of 2 to 10 h.

15. 12. The method of claim 1 or 11, wherein the reaction of step (4) is carried out in the presence of a protective gas.

16. The method according to claim 15, wherein the volume ratio of the protective gas to the diphenylamine raw material is 5-500:

1.

17. 12. The method of claim 1, 2, 3, 8, or 11, further comprising mixing and purifying the first gas product obtained in step (2) and the second gas product obtained in step (5).

18. 1. A system for producing diphenylamine and phenothiazine from aniline, comprising: a first reactor (100) in which the aniline feedstock undergoes reaction; a first gas-liquid separation device (200) for separating the reaction mixture obtained in the first reactor (100) into gas and liquid to obtain a first liquid product and a first gas product; a first product separation device (300) for separating and treating the first liquid product separated in the first gas-liquid separation device (200) to obtain an aniline recovery material and a diphenylamine product; a second reactor (400) for reacting a portion of the diphenylamine product from the first product separation device (300) in the second reactor (400); a second gas-liquid separation device (500) for separating the reaction mixture obtained in the second reactor (400) into gas and liquid to obtain a second liquid product and a second gas product; a second product separation device (600) for separating a phenothiazine product from the second liquid product separated in the second gas-liquid separation device (500); The first product separation device (300) is a multi-stage rectification device; The multi-stage rectification apparatus is a light fraction removal column (310) for rectifying the first liquid product separated in the first gas-liquid separation device (200) and discharging a light fraction from the top of the column; an aniline recovery column (320) for rectifying the product from the bottom of the light fraction removal column (310), collecting aniline recovery material from the top, and obtaining a diphenylamine-containing stream at the bottom; an intermediate fraction column (330) for rectifying the diphenylamine-containing stream from the aniline recovery column (320) to discharge an intermediate fraction from the top of the column and obtain a diphenylamine-rich stream at the bottom of the column; a diphenylamine product column (340) for rectifying the diphenylamine-rich stream from the intermediate fraction column (330) to obtain diphenylamine products of different purity from the top and side lines, respectively, and discharging a heavy fraction from the bottom of the column; The second product separation device (600) comprises: an adsorption / de-impurity device (610) for adsorbing and de-impurifying the second liquid product separated in the second gas-liquid separation device (500); a vacuum distillation unit (620) for vacuum distilling the liquid product treated in the adsorption impurity removal unit (610) to obtain a diphenylamine-rich light fraction and a phenothiazine product; a diphenylamine-rich material transport pipeline (621) for delivering a diphenylamine-rich light fraction to the top of the vacuum distillation apparatus (620), the diphenylamine-rich material transport pipeline (621) being connected to a diphenylamine-containing stream feed port of the intermediate fraction column (330).

19. 19. The system of claim 18, wherein the diphenylamine product column (340) is provided at the top with a diphenylamine quality product transport pipeline (341) for delivering diphenylamine quality products, and at the side of the column is provided a diphenylamine quality product transport pipeline (342) for collecting diphenylamine quality products, and the diphenylamine quality product transport pipeline (341) is connected to the diphenylamine raw material supply port of the second reactor (400).

20. 20. The system according to claim 18 or 19, further comprising an exhaust purification device (800), wherein a first gas product transport pipeline (201) provided at the top of the first gas-liquid separation device (200) and a second gas product transport pipeline (501) provided at the top of the second gas-liquid separation device (500) are in communication with the exhaust purification device (800).

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