Co-production process of N-methylaniline, N-N-dimethylaniline and hydrogen

Abstract

The invention discloses a co-production technology of N-N-dimethylaniline and hydrogen. The whole reaction technology comprises raw material conveying. The technology comprises a storage tank, a heat exchanger, a methylation reactor, a gas-liquid separator, a booster pump, a rectifying tower, a pump and an intermediate tank. And a plurality of unit operations are organically combined to form a whole set of complete process technology. By using aniline and methanol as raw materials, co-production of N-methylaniline, N, N-dimethylaniline and hydrogen can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical industry, and specifically relates to a process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen. Background Art

[0002] NN-dimethylaniline (DMA) is mainly used to produce methane dyes, and can also be used as a raw material for the production of solvents, explosives, and medicines. The main consumption areas of DMA are dyes and spices. Due to the good sales of varieties such as basic yellow and basic purple in recent years, DMA consumption has increased. In the spice industry, DMA is mainly used to produce vanillin. As a broad-spectrum spice, vanillin is one of the most widely used spices, and the application of DMA in the spice industry is on the rise. In the pharmaceutical industry, DMA is mainly used as an intermediate for products such as SSM.

[0003] The traditional liquid phase process for the production of N,N-dimethylaniline is carried out in a reactor using sulfuric acid as a catalyst. Although the technology is mature and the product yield is high, the corrosion to the equipment is serious and does not conform to the current concept of green chemical industry. The improvement of the traditional process mainly includes catalyst research and raw material selection. Foreign researchers have tried Raney nickel, Pd / C, liquid homogeneous catalysts, etc., but none of them achieved a high yield. Replacing the N-methylation reagent with alcohols and more active aldehydes and ketones did not solve the problem of low product yield.

[0004] The new gas phase method was first developed by the Indian National Laboratory using a modified alumina catalyst, which achieved continuous low-pressure gas phase production. However, the catalyst stability of this process was poor, and liquid additives needed to be continuously provided to reduce the catalyst. There were also many impurities in the product, and subsequent research processes were improved. BASF modified the alumina catalyst by phosphoric acid impregnation. The modified catalyst had a good effect in the preparation of N,N-dimethylaniline, but the yield was found to be low in the production research of N-methylaniline. Some foreign researchers used co-precipitated self-made molecular sieve catalysts to achieve good yields in the research of N,N-dimethylaniline, but they were limited to laboratory research data and were not enlarged, and the stability of the catalyst needed to be studied. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention is proposed, namely a process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen.

[0006] The content of this part is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. In this part and the specification summary and the invention title of this application, some simplifications or omissions may be made to avoid blurring the purpose of this part, the specification summary and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] The invention provides a process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen, which uses aniline and methanol as raw materials, co-produces NN-dimethylaniline and hydrogen in the presence of a catalyst, and mainly includes preheating, methylation reaction, gas-liquid separation, distillation, and hydrogen circulation units, wherein the distillation unit is a two-stage distillation. The organic combination of multiple unit operations forms a complete set of process technologies.

[0008] The entire reaction process of the present invention includes raw material conveying and storage tanks, heat exchangers, methylation reactors, gas-liquid separators, buffer tanks, compressors, distillation towers, pumps, intermediate tanks and other equipment.

[0009] Generally, the invention discloses a process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen, comprising: mixing aniline and methanol raw materials with a carrier gas and preheating the mixture; performing a methylation reaction under the action of a copper-zinc-aluminum catalyst; cooling the reaction product and performing gas-liquid separation; performing secondary distillation on the separated NN-dimethylaniline to remove light components and heavy components to obtain the NN-dimethylaniline product; recycling a part of the separated hydrogen, and recompressing the other part in a buffer tank and utilizing the hydrogen.

[0010] The copper-zinc-aluminum catalyst used in the present invention has a mass composition of 20-35% copper oxide, 40-60% zinc oxide, 20-35% aluminum oxide, and 0-1% additive. The specific surface area of ​​the copper-zinc-aluminum catalyst is 40-80 m 2 / g.

[0011] Generally, the additive added to the catalyst of the present invention is one or more of cerium, magnesium and manganese.

[0012] The methylation reaction conditions of the present invention are as follows: at a temperature of 220 to 270°C and a liquid space velocity of 0.2 to 0.5 h -1 , pressure 1.0~2.0MPa, aniline methanol molar ratio 1:5~1:7, hydrogen volume space velocity 1000~5000 -1 .

[0013] The preparation method of the copper-zinc-aluminum catalyst of the present invention comprises the following steps: (1) Prepare an aqueous solution A of a precipitant of sodium bicarbonate or sodium carbonate with a mass fraction of 10% to 15%, and heat to 55 to 65°C with stirring; (2) preparing a mixed aqueous solution B containing 10% to 15% copper nitrate and zinc nitrate by mass; (3) Add pseudo-boehmite to the stirred solution A, stir for 30-40 minutes, control the temperature at 60-70°C during stirring, and obtain a mixed suspension C; (4) Add solution B dropwise to suspension C over a period of 15 to 30 minutes, control the temperature at 60 to 70°C, and control the endpoint pH at 7.0 to 9.0 when the reaction is complete; (5) washing and filtering to obtain a filter cake, and drying; (6) Granulation; (7) Spray the additive solution onto the particles, dry them, and then calcine them at 320-380°C for 3-4 hours; (8) The catalyst is obtained by tableting.

[0014] The catalyst of the present invention needs to be activated before use.

[0015] The methylation reaction of the N,N-dimethylaniline and hydrogen co-production process of the present invention is carried out in a tubular fixed bed reactor, the carrier gas is nitrogen or hydrogen, preferably hydrogen, and heating is performed by heat transfer oil or water vapor.

[0016] Advantages of the present invention: The present invention can realize the co-production of N,N-dimethylaniline and hydrogen, and crack part of methanol into hydrogen, which is particularly suitable for industrial parks with insufficient hydrogen resources. While meeting the needs of the industrial parks themselves, hydrogen can also be provided to the outside, thus realizing the diversification of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0018] Figure 1 The figure is a schematic diagram of the process flow of the co-production of N-methylaniline, NN-dimethylaniline and hydrogen according to an embodiment of the present invention. Implementation

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with embodiments and drawings.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Example 1

[0021] like Figure 1As shown, this embodiment provides a device for co-producing N-methylaniline, NN-dimethylaniline and hydrogen, and the main equipment includes: storage tanks (1, 3, 12, 17, 18), heat exchangers (5, 7, 15), reactors (6), gas-liquid separators (8), buffer tanks (9), compressors (19), distillation towers (11, 14), pumps (2, 4, 13), and intermediate tanks (16, 21).

[0022] The reactor (6) adopts a tube-type fixed bed reaction process and is heated by steam or thermal oil. The reactor (6) has an inlet at the top and an outlet at the bottom. The upper and lower end caps of the reactor (6) are opened, and the copper-based hydrogenation catalyst is loaded into the reactor tubes, wherein a section of inert porcelain balls is loaded at each end of the reactor tubes. Finally, the upper and lower end caps are covered to complete the catalyst loading of the reactor (6). It should be noted that after the entire system is installed and the catalyst is loaded, nitrogen is passed through the nitrogen inlet to the entire system for replacement, and the nitrogen is filled to maintain a pressure of 2.5MPa for an airtight test. The airtight test is qualified when the pressure drop is less than 0.2MPa for 24 hours, and subsequent experiments are carried out.

[0023] The raw material storage tanks (1, 3), the hydrogen inlet and the nitrogen inlet are connected to the upper inlet of the reactor (6) via the heat exchanger (5); when the system is in operation, nitrogen is first introduced into the reactor (6) through the nitrogen inlet, then the temperature of the reactor (6) is gradually increased, and hydrogen is introduced into the reactor (6) through the hydrogen inlet to start catalyst activation.

[0024] After the catalyst activation is completed, hydrogen is slowly introduced into the reaction system. When the system pressure rises to the reaction pressure of 1.0-2.0 MPa, the hydrogen circulation compressor (19) is turned on to maintain the flow rate and reaction pressure of the system hydrogen.

[0025] In the reaction stage, the fluid pump (2, 4) is turned on to allow the raw materials in the raw material storage tanks (1, 3) to be preheated through the heat exchanger (5) and then enter the reactor from the inlet at the top of the reactor (6), where they are mixed with hydrogen and reacted together under the following conditions; the product flows out from the outlet at the bottom of the reactor (6), is cooled in the heat exchanger (7), and then enters the gas-liquid separation tank (8) for gas-liquid separation.

[0026] The gas-liquid separation tank (8) has a separation inlet, an outlet at the top, and a liquid outlet at the bottom; the product flowing out from the outlet at the bottom of the reactor enters the gas-liquid separation tank (8) from the inlet of the gas-liquid separation tank (8) for gas-liquid separation; the hydrogen mixed gas separated at the top of the gas-liquid separation tank (8) enters the gas buffer tank (9), and the hydrogen in the buffer tank (9) is discharged from the system through the back pressure valve (10) for utilization. The other part should be recycled by the hydrogen circulation compressor (19) at the reactor inlet.

[0027] The liquid material separated at the bottom of the gas-liquid separation tank (8) enters the distillation tower (11) from the feed inlet in the middle of the distillation tower (11) for distillation. The distillate enters the condenser (20) from the distillate outlet at the top of the distillation tower (11) for condensation and then enters the intermediate tank (21). A part of the distillate in the intermediate tank (21) returns to the distillation tower for reflux, and the other part of the distillate enters the storage tank (12).

[0028] The liquid material discharged from the bottom of the distillation tower (11) enters the distillation tower (14) from the feed inlet in the middle of the distillation tower (14) through the feed pump (13) for distillation. The distillate is discharged from the distillate outlet at the top of the distillation tower (14). A part of the distillate returns to the distillation tower for reflux, and another part of the distillate enters the product storage tank (16). The heavy component at the bottom of the distillation tower (14) enters the storage tank (18). Example 2

[0029] In order to further illustrate the present invention, the catalyst was prepared in the laboratory according to the following implementation method. The specific operation steps are as follows: (1) Prepare an aqueous solution A of a precipitant of sodium bicarbonate or sodium carbonate with a mass fraction of 10% to 15%, and heat to 55 to 65°C with stirring; (2) preparing a mixed aqueous solution B containing 10% to 15% copper nitrate and zinc nitrate by mass; (3) Add pseudo-boehmite to the stirred solution A, stir for 30-40 minutes, control the temperature at 60-70°C during stirring, and obtain a mixed suspension C; (4) Add solution B dropwise to suspension C over a period of 15 to 30 minutes, control the temperature at 60 to 70°C, and control the endpoint pH at 7.0 to 9.0 when the reaction is complete; (5) washing and filtering to obtain a filter cake, and drying; (6) Granulation; (7) Spray a certain amount of additives into a solution and spray it onto the particles. After drying, calcine at 320-380°C for 3-4 hours. (8) The catalyst is pressed into tablets to obtain a size of Φ5*4~5mm.

[0030] The specific catalyst preparation is shown in Table 1, and the chemical composition and BET results of the prepared catalyst are shown in Table 2.

[0031] Table 1 Catalyst preparation

[0032] Table 2 Physical and chemical properties of catalysts Example 3

[0033] In order to further illustrate the present invention, the reaction and distillation operations are carried out in the laboratory according to the above implementation method. The specific operation steps are as follows: Reaction system operation Catalyst activation: For the system that has passed the nitrogen replacement airtightness test, nitrogen is introduced into the reactor (6) through the nitrogen inlet at a gas volume space velocity of 8000 h -1 Hydrogen was introduced into the reactor (6) through the hydrogen inlet to make the hydrogen volume content 5%, and then the reactor (6) was gradually heated to a constant temperature of 230°C. The catalyst activation conditions were controlled as shown in Table 3.

[0034] Table 3 Catalyst temperature reduction program

[0035] Pressure-boosting cycle: After the catalyst activation is completed, hydrogen or nitrogen is slowly introduced into the reaction system. When the system pressure rises to the reaction pressure of 1-2 MPa, the circulation compressor is turned on to circulate the gas in the entire reaction system to maintain the system gas flow and reaction pressure.

[0036] Reaction: methanol fluid pump (2) is turned on to take methanol from methanol storage tank (1); aniline fluid pump (4) is turned on to take aniline from aniline storage tank (3); methanol and aniline are preheated by heat exchanger (5) and then enter reactor (6) from the inlet at the top of reactor, and are mixed with hydrogen to react under the following conditions: temperature 220-270°C, liquid space velocity 0.2-0.5h -1 , pressure 1.0~2.0MPa, aniline methanol molar ratio 1:5~1:7, hydrogen volume space velocity 1000~5000 -1 The reaction product flows out from the outlet at the bottom of the reactor (6), is cooled to 10-20°C in the heat exchanger (7), and enters the gas-liquid separation tank (8) for gas-liquid separation.

[0037] The hydrogen separated from the top of the gas-liquid separation tank enters the buffer tank (9), a part of which is circulated into the reactor (6) through the circulation compressor (19), and the other part is discharged into the hydrogen utilization process through the back pressure valve (10) to maintain a constant system pressure.

[0038] Distillation system operation: The liquid material separated from the bottom of the gas-liquid separation tank (8) is controlled at an appropriate temperature and enters the distillation tower (11) for distillation; the distillate is discharged from the distillate outlet at the top of the distillation tower, cooled in the heat exchanger (20), and then a part of the distillate is returned to the distillation tower (11) through the intermediate tank (21) for reflux, and the other part of the distillate is entered into the methanol raw material storage tank (12) through the pipeline. At the same time, the methanol in the storage tank (12) can be returned to the storage tank (1) for recycling.

[0039] The liquid material discharged from the bottom of the distillation tower (11) is controlled at an appropriate temperature and enters the distillation tower (14) for distillation; the distillate is discharged from the distillate outlet at the top of the distillation tower, cooled in the heat exchanger (15), and then a portion of the distillate is returned to the distillation tower (14) for reflux through the intermediate tank (16), and the other portion of the distillate is entered into the product storage tank (17) through the pipeline. The liquid material discharged from the bottom of the distillation tower (14) enters the storage tank (18).

[0040] This example tests the effects of different catalysts and reaction process conditions on N-methylaniline, N,N-dimethylaniline and hydrogen production. The specific implementation conditions and product analysis data are shown in Table 4: Table 4 Reaction process conditions

[0041] The process conditions of the specific embodiment are shown in Table 5.

[0042] Table 5 Example process conditions and results

[0043] According to the operations of the methylation reaction of aniline in the above-mentioned steps 1 to 16, it can be seen from the above-mentioned experimental results that the process of the present invention can achieve an aniline conversion rate of more than 99.7%, and an N,N-dimethylaniline selectivity of 98.1%, which has a high N,N-dimethylaniline selectivity. At the same time, the production of 1 mole of N,N-dimethylaniline can produce 1 mole of hydrogen as a by-product.

[0044] The continuous reaction method of the present invention comprises an organic combination of the entire reaction process including raw material transportation and preheating, reaction, gas-liquid separation, distillation, and hydrogen circulation unit operations, forming a complete set of reaction process technology, and can realize diversified production of the device according to different raw material compositions and different process parameters.

[0045] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A process for the co-production of N-methylaniline, NN-dimethylaniline and hydrogen, characterized in that: The process uses aniline and methanol as raw materials and co-produces NN-dimethylaniline and hydrogen in the presence of a catalyst, including preheating, methylation reaction, gas-liquid separation, distillation, and hydrogen circulation units, wherein the distillation unit is a two-stage distillation.

2. The process for co-production of N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 1, comprising preheating the mixture of aniline and methanol raw materials with a carrier gas; carrying out a methylation reaction under the action of a copper-zinc-aluminum catalyst, cooling the reaction product and performing gas-liquid separation, performing secondary distillation on the separated NN-dimethylaniline, removing light components and heavy components to obtain the NN-dimethylaniline product; recycling a part of the separated hydrogen, and recompressing the other part in a buffer tank for utilization.

3. The process for co-production of N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 2, characterized in that: The mass composition of the copper-zinc-aluminum catalyst is 20-35% copper oxide, 40-60% zinc oxide, 20-35% aluminum oxide, and 0-1% additive. The specific surface area of ​​the copper-zinc-aluminum catalyst is 40-80 m 2 / g.

4. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 3, characterized in that: The auxiliary agent of the copper-zinc-aluminum catalyst is one or more of cerium, magnesium and manganese.

5. The process for co-production of N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 1 or 2, characterized in that: The methylation reaction conditions are: temperature 220-270°C, liquid space velocity 0.2-0.5h -1 , pressure 1.0~2.0MPa, aniline methanol molar ratio 1:5~1:7, hydrogen volume space velocity 1000~5000 -1 .

6. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 2, 3 or 3, characterized in that The copper-zinc-aluminum catalyst preparation method comprises the following steps: (1) Prepare aqueous solution A with a mass fraction of 10% to 15% of precipitant, stir and heat to 55-65°C; (2) preparing a mixed aqueous solution B containing 10% to 15% copper nitrate and zinc nitrate by mass; (3) Add pseudo-boehmite to the stirred solution A, stir for 30 to 40 minutes, control the temperature at 60 to 70°C during the stirring process, and obtain a mixed suspension C; (4) Add solution B dropwise to suspension C over a period of 15 to 30 minutes, control the temperature at 60 to 70°C, and control the endpoint pH at 7.0 to 9.0 when the reaction is complete; (5) washing and filtering to obtain a filter cake, and drying; (6) Granulation; (7) Spray the additive solution onto the particles, dry them, and then calcine them at 320-380°C for 3-4 hours; (8) The catalyst is obtained by tableting.

7. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 6, characterized in that: The precipitant is any one of sodium bicarbonate or sodium carbonate.

8. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 2 or 6, characterized in that: Copper-zinc-aluminum catalysts need to be activated before use.

9. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 1 or 2, characterized in that The methylation reaction was carried out in a fixed bed reactor.

10. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 9, characterized in that: The fixed bed reactor is a tube-in-tube fixed bed reactor, which is heated by heat transfer oil or steam.

11. The process for co-production of N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 2, characterized in that: The carrier gas is hydrogen or nitrogen.

12. The process for co-producing N-methylaniline, NN-dimethylaniline and hydrogen as claimed in claim 11, characterized in that: The carrier gas is hydrogen.

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