Method for preparing tert-butylamine through amination reaction of isobutene

Abstract

The invention discloses a method for preparing tert-butylamine through an amination reaction of isobutene, which is characterized in that by controlling the content of methanol in an isobutene raw material to be 10-400ppm and the content of dimethyl ether to be 10-300ppm, not only can the occurrence of side reactions such as methoxylation be reduced, but also the selectivity and the conversion rate of a catalyst can be improved, and the reaction is more beneficial in thermodynamics. Meanwhile, the content of oxidizing substances such as methyl formate and acetone is controlled to be smaller than or equal to 50 ppm, so that the oxidation phenomenon possibly occurring in the high-temperature reaction process can be greatly reduced, the yellowing tendency of the rectified product is reduced, the quality guarantee period of the product is prolonged, and the quality of the product is improved.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and particularly relates to a method for preparing tert-butylamine through amination reaction of isobutylene. Background Art

[0002] As an important chemical intermediate, tert-butylamine plays a pivotal role in the field of rubber accelerators. Accelerators are the most basic and important type of rubber additives, and are the largest type of rubber additives in my country. The sulfonamide accelerators NS (N-tert-butyl-2-benzothiazole sulfonamide) and TBSI (N-tert-butylbis-2-benzothiazole sulfonamide) synthesized from tert-butylamine have the greatest feature of not producing carcinogenic nitrosamines during the vulcanization process. At the same time, they have the advantages of general sulfonamide accelerators, are very safe at operating temperatures, have good scorch resistance, can increase the proportion of synthetic rubber, and increase the amount of filler carbon black. Its performance is very close to the accelerator NOBS (N-oxydiethylene-2-benzothiazole sulfonamide) currently used in China. It has slight discoloration and pollution, and excellent performance, so it is called "standard accelerator". It is the most ideal substitute product for the carcinogenic accelerator NOBS.

[0003] There are many methods for preparing tert-butylamine, such as tert-butyl urea hydrolysis method, tert-butyl amide hydrolysis method, isobutylene-HCN method, halogenated hydrocarbon amination method, etc. The production process involves the use and treatment of strong acid / strong base, and the equipment has serious corrosion and pollution problems, which does not meet the requirements of green chemical industry.

[0004] The direct amination of isobutylene to prepare tert-butylamine has a clean process and 100% atomic utilization, which meets the requirements of green chemical industry and sustainable development and is the future development direction of tert-butylamine research and development and industrial production.

[0005] US4375002A discloses direct amination of isobutylene using amorphous aluminum silicate or silicon aluminum molecular sieve as a catalyst. However, since the acid centers of aluminum silicate materials and silicon aluminum molecular sieves are too strong, they are prone to promote olefin polymerization reactions at high temperatures, resulting in carbon accumulation on the catalyst surface and rapid deactivation of the catalyst, and thus industrial scale-up applications have not been achieved.

[0006] In her master's thesis "Research on the Process of Clean Synthesis of Tert-Butylamine" in 2006, Shi Aie showed that the conversion rate of isobutylene amination reaction using the screened and optimized catalyst HS-FAZ could only reach 95-97%, and white suspended matter appeared in the reaction mother liquor. The selected raw material isobutylene was of low purity and the key impurities were not treated, so the purity was only 98%.

[0007] US4929759A discloses a borosilicate molecular sieve. It is found that after reacting for 30 minutes at 350°C, 30MPa, and a molecular ratio of isobutylene to ammonia of 1:1.5, the isobutylene conversion rate is 14.1% and the selectivity is 95.7%. It has a large number of by-products, poor reaction selectivity, and the reaction temperature reaches 300°C, which is not conducive to the thermodynamic direction of the reaction.

[0008] Therefore, according to the prior art, the current industrial preparation of tert-butylamine usually adopts the method of isobutylene amination. This process route meets the requirements of green chemical industry and sustainable development, but because the reaction is a balanced reaction, the reaction conversion rate is low, and because the reaction is an exothermic reaction, low temperature is conducive to the reaction, and the reaction also requires a higher temperature to promote reaction activation and product desorption, so the reaction has dual thermodynamic and kinetic limitations. At the same time, in the preparation of tert-butylamine by direct amination of isobutylene, there are usually more impurities in the raw material isobutylene, including tert-butyl alcohol, methyl tert-butyl ether, methanol, water and other impurities, which affect the reaction selectivity and product yield, and the post-processing process of impurities is also more complicated.

[0009] Therefore, it is necessary to develop a method for controlling the impurity content of raw materials to control the impurity content from the source, so as to solve the problem of improving the selectivity and conversion rate of the amination reaction and reducing the energy consumption of post-processing. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides a method for preparing tert-butylamine by amination of isobutylene. By controlling the impurity content of the raw material isobutylene, the side reactions of the amination reaction can be reduced, the conversion rate and selectivity of the amination reaction can be improved, the reaction and separation energy consumption can be reduced, and the quality of the product tert-butylamine can be improved.

[0011] As mentioned above, the direct amination of isobutylene to prepare tert-butylamine usually contains a lot of impurities in the raw material isobutylene, including tert-butyl alcohol, methyl tert-butyl ether, dimethyl ether, methanol, water, methyl formate and acetone. Usually, methanol will trigger side reactions to generate addition byproducts such as N-methyl tert-butylamine and methyl tert-butyl ether, and water will react with the isobutylene raw material to produce tert-butyl alcohol at the acidic site of the catalyst, making it difficult to achieve a high level of reaction selectivity, affecting the product yield, and the excess tert-butyl alcohol is very close to tert-butylamine in molecular structure, making it difficult to separate it in the subsequent processing process, increasing energy consumption.

[0012] However, the applicant has found that when a certain amount of methanol and dimethyl ether are present in the amination reaction system, due to the presence of carbon-oxygen bonds in substances such as methanol and dimethyl ether, they can interact with the products on the active sites of the amination reaction catalyst, bringing tert-butylamine out of the catalyst surface, shortening its residence time on the catalyst surface, greatly inhibiting the reverse reaction process, achieving the reaction distillation effect at the molecular level, greatly improving the selectivity and conversion rate of the catalyst, and making the reaction more thermodynamically favorable. If the content of methanol and dimethyl ether is further reduced, not only will the energy consumption of separation be increased, but it will also be unfavorable for subsequent product desorption. Therefore, the present invention requires that the content of methanol and dimethyl ether in the isobutylene raw material be controlled within a specific range, which can not only reduce the occurrence of side reactions, but also improve the conversion rate and selectivity of the amination catalyst from the perspective of reaction thermodynamics.

[0013] Based on the above research findings, in order to achieve the above objectives, the present invention adopts the following technical solutions:

[0014] A method for preparing tert-butylamine by isobutylene amination reaction comprises: directly aminating isobutylene and liquid ammonia under the action of a catalyst to prepare tert-butylamine, wherein the methanol content in the isobutylene raw material is 10-400 ppm, and the dimethyl ether content is 10-300 ppm.

[0015] Preferably, the molar ratio of liquid ammonia to isobutylene is 1-20:1; preferably 1-10:1, more preferably 1-4:1, the catalyst is a commonly used molecular sieve catalyst, and the further molecular sieve catalyst is selected from at least one of MCM molecular sieve, H-BETA molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve and mordenite.

[0016] Preferably, the reaction temperature of the amination reaction is 100-350° C., and the reaction pressure is 5-15 MPa(A).

[0017] Preferably, the amination reaction is a batch reaction or a continuous reaction.

[0018] The intermittent reaction is carried out in a closed reactor, and isobutylene, liquid ammonia and the catalyst are contacted. There is no particular restriction on the order of adding the materials, and they can be introduced into the reaction system separately or after mixing.

[0019] The continuous reaction is to load the catalyst into the reactor, and the isobutylene and liquid ammonia are continuously passed through the reactor to achieve continuous reaction to prepare tert-butylamine. There is no particular order restriction for adding the materials, and they can be introduced into the reaction system separately or mixed.

[0020] Preferably, the present invention adopts a continuous reaction, and the feed mass space velocity of isobutylene is 3-10h -1 .

[0021] The present invention has no special requirements for the method of controlling the content of methanol and dimethyl ether. Specifically, operations such as distillation, extraction, adsorption, etc. can be used for isobutylene as long as it can be controlled within the above range.

[0022] As a specific preferred embodiment, the present invention provides a method for pretreating an isobutylene raw material, comprising the following steps:

[0023] (1) extracting the crude isobutylene through an extraction tower to obtain primary refined isobutylene;

[0024] (2) The primary refined isobutylene is treated in a water separator to obtain refined isobutylene.

[0025] Preferably, in step (1) of the present invention, the extractant used in the extraction tower is water, and the mass ratio of the extractant to the crude isobutylene is 1-20:1, preferably 1-10:1, more preferably 3-6:1;

[0026] Preferably, the extraction temperature is 10-80°C, preferably 30-60°C; the extraction pressure is 0.1-2MPa(G), preferably 0.3-1.5MPa(G); the extraction residence time is 2-8h, preferably 2-4h;

[0027] Preferably, in the extraction tower, the crude isobutylene and the extractant are continuously extracted in a countercurrent manner to obtain primary refined isobutylene after the extraction.

[0028] Preferably, the extraction tower is equipped with a filler to ensure that the extractant and the crude isobutylene phases can be fully contacted; more preferably, the extraction tower filler is one or more of a metal grid filler, a triangular bolt filler or a Raschig ring filler; the contact time between the extractant and the crude isobutylene phases can be controlled by controlling the filler of the filler.

[0029] Preferably, in step (2) of the present invention, the temperature during water separation is controlled to be 10-60°C, preferably 15-25°C; the pressure is 0.1-2MPa(G), preferably 0.1-0.4MPa(G); the residence time in the water separator is 10-400min, preferably 20-60min;

[0030] Preferably, the water separator is built with a coalescer, so that the particle size of free water in the primary refined isobutylene is increased, which is beneficial to the water separation operation;

[0031] Preferably, the coalescer contains a separation membrane, which is one or more of a polypropylene fiber membrane, a polyethylene fiber membrane, and a polytetrafluoroethylene fiber membrane.

[0032] In one embodiment, the primary refined isobutylene is passed through a water separator at a certain temperature and pressure to gradually polymerize and precipitate free water in the isobutylene to obtain refined isobutylene, wherein the methanol content is 10-400ppm, the dimethyl ether content is 10-300ppm, and the water content is 10-1000ppm.

[0033] In a specific embodiment, crude isobutylene is first added to a raw material buffer tank, pressurized to a specified extraction pressure, and heated to a specified extraction temperature through a preheater. Another stream of extractant water is pressurized and temperature-controlled in the same manner and added to an extraction tower. The two streams of material are continuously extracted in a countercurrent manner, and the flow rates of the two streams of material are adjusted. The extraction tower is washed with extraction water in a certain ratio. After extraction, primary refined isobutylene is obtained at the top of the tower, and then water is separated by a water separator to obtain refined isobutylene, which can be used as a raw material for subsequent amination reactions. Extraction wastewater is obtained at the bottom of the tower and treated as waste liquid.

[0034] In addition, the applicant has found that part of methyl formate and acetone will be dissolved in the organic matter such as methanol and dimethyl ether removed by extraction with the extractant water in the present invention, which can to a certain extent prevent the oxidation of the tert-butylamine product in the subsequent amination reaction and avoid the generation of a series of hydroxylamine and nitroso compounds, which makes the product prone to yellowing and has problems with the storage stability of the product.

[0035] Furthermore, the present application controls the content of oxidizing substances such as methyl formate and acetone in the raw material isobutylene to be less than or equal to 50 ppm.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The method for preparing tert-butylamine by isobutylene amination reaction of the present invention can control the content of key impurities in the isobutylene raw material, and control oxygen-containing impurities (such as methanol and dimethyl ether) within a reasonable range, which can not only reduce the occurrence of side reactions such as methoxylation, but also utilize the interaction between substances such as methanol and dimethyl ether and the tert-butylamine product to enable it to be smoothly desorbed, thereby greatly improving the conversion rate of the amination reaction; at the same time, the water causing the side reaction to produce tert-butyl alcohol and the key impurity tert-butyl alcohol that is difficult to separate are strictly controlled within a specified range, preventing excessive water from entering the reactor to cause water vapor passivation of the catalyst, improving the reaction yield, extending the service life of the catalyst, and avoiding the generation of excessive tert-butyl alcohol impurities, reducing the reaction separation energy consumption, and improving the product quality; further, the present invention also controls the content of substances with strong oxidizing properties such as methyl formate and acetone in the raw material, which can reduce the side reactions occurring in the high-temperature reaction process, reduce the yellowing tendency of the tert-butylamine product after distillation, extend the product shelf life, and improve the product quality. DETAILED DESCRIPTION

[0038] In order to better understand the present invention, the present invention is further explained below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

[0039] The sources of the main raw materials used in the examples and comparative examples of the present invention are as follows. Unless otherwise specified, other reagents and raw materials are all common commercially available products:

[0040] Liquid ammonia: purity 99.8%, water content 1000ppm, Shandong Lianmeng Chemical Co., Ltd.;

[0041] H-BETA: silicon-aluminum ratio is 25, Shandong Dengzhuo;

[0042] The crude isobutylene described in the present invention comes from Wanhua isobutylene device, wherein the isobutylene is 99.19wt%, tert-butyl alcohol is 0.02wt%, methyl tert-butyl ether is 0.01wt%, water is 0.2wt%, dimethyl ether is 0.05wt%, methyl formate is 0.04wt%, methanol is 0.4wt%, acetone is 0.05wt%, and the content of other impurities is about 0.04wt%.

[0043] The impurity detection method refers to standards SH / T 1482-2004 and SH / T 1483-2004.

[0044] Tert-butylamine product color number testing standard: GB / T 6324.6-2014.

[0045] Example 1

[0046] The crude isobutylene is first added to the isobutylene raw material buffer tank, pressurized to an extraction pressure of 2MPa(G) by a plunger pump, heated to an extraction temperature of 30°C by a preheater, and enters from the bottom of the extraction tower. Another stream of extractant water is pressurized in the same way and controlled at the same temperature as the crude isobutylene, and added from the top of the extraction tower to ensure that the water and oil phases enter in a countercurrent manner. The flow rates of the two streams of materials are adjusted, and the extraction is carried out through the extraction tower according to the mass ratio of the extractant to the crude isobutylene of 4:1, and the residence time is 2h. After extraction, the primary refined isobutylene is obtained at the top of the tower, and the extraction wastewater is obtained at the bottom of the tower, which is treated as waste liquid; the primary refined isobutylene at the top of the tower is then separated by a water separator, the separation temperature is 40°C, the pressure is 0.4MPa(G), and the residence time of the water separator is 20min to obtain refined isobutylene raw material. The extraction tower is equipped with Raschig ring filler to ensure full contact between the water and oil phases, and the water separator is equipped with a coalescer, using a polyethylene fiber membrane.

[0047] Example 2

[0048] The crude isobutylene is first added to the isobutylene raw material buffer tank, pressurized to an extraction pressure of 1MPa(G) by a plunger pump, heated to an extraction temperature of 50°C by a preheater, and enters from the bottom of the extraction tower. Another stream of extractant water is pressurized in the same way and controlled at the same temperature as the crude isobutylene, and added from the top of the extraction tower to ensure that the water and oil phases enter in a countercurrent manner. The flow rates of the two streams of materials are adjusted, and the extraction is carried out through the extraction tower according to the mass ratio of the extractant to the crude isobutylene of 2:1, and the residence time is 3h. After extraction, the primary refined isobutylene is obtained at the top of the tower, and the extraction wastewater is obtained at the bottom of the tower, which is treated as waste liquid. The primary refined isobutylene at the top of the tower is then separated by a water separator, the separation temperature is 10°C, the extraction pressure is 0.1MPa(G), and the residence time of the water separator is 4h to obtain a refined isobutylene raw material, wherein the extraction tower is equipped with a triangular spiral filler to ensure full contact between the water and oil phases, and the water separator is equipped with a coalescer, using a polyethylene fiber membrane.

[0049] Example 3

[0050] The crude isobutylene is first added to the isobutylene raw material buffer tank, pressurized to an extraction pressure of 1.4MPa(G) by a plunger pump, heated to an extraction temperature of 60°C by a preheater, and enters from the bottom of the extraction tower. Another stream of extractant water is pressurized in the same way and controlled at the same temperature as the crude isobutylene, and added from the top of the extraction tower to ensure that the water and oil phases enter in a countercurrent manner. The flow rates of the two streams of materials are adjusted, and the extraction is carried out through the extraction tower according to the mass ratio of the extractant to the crude isobutylene of 4:1, and the residence time is 2h. After extraction, the primary refined isobutylene is obtained at the top of the tower, and the extraction wastewater is obtained at the bottom of the tower, which is treated as waste liquid. The primary refined isobutylene at the top of the tower is then separated by a water separator, the separation temperature is 20°C, the extraction pressure is 0.1MPa(G), and the residence time of the water separator is 60min to obtain a refined isobutylene raw material, wherein the extraction tower is equipped with a metal grid filler to ensure full contact between the water and oil phases, and the water separator is equipped with a coalescer, using a polypropylene fiber membrane.

[0051] Example 4

[0052] The crude isobutylene is first added to the isobutylene raw material buffer tank, pressurized to an extraction pressure of 1.4MPa(G) by a plunger pump, heated to an extraction temperature of 30°C by a preheater, and enters from the bottom of the extraction tower. Another stream of extractant water is pressurized in the same way and controlled at the same temperature as the crude isobutylene, and added from the top of the extraction tower to ensure that the water and oil phases enter in a countercurrent manner. The flow rates of the two streams of materials are adjusted, and the extraction is carried out through the extraction tower according to the mass ratio of the extractant to the crude isobutylene of 5:1, and the residence time is 3h. After extraction, the primary refined isobutylene raw material is obtained at the top of the tower, and the extraction wastewater is obtained at the bottom of the tower, which is treated as waste liquid. The primary refined isobutylene at the top of the tower is then separated by a water separator, the separation temperature is 30°C, the extraction pressure is 0.2MPa(G), and the residence time of the water separator is 40min to obtain a refined isobutylene raw material, wherein the extraction tower is equipped with a metal grid filler to ensure full contact between the water and oil phases, and the water separator is equipped with a coalescer, using a polytetrafluoroethylene fiber membrane.

[0053] The following table shows the content of impurities in the isobutylene raw materials of Examples 1-4 and Comparative Examples 1-3.

[0054]

[0055]

[0056] Examples 5-8 and Comparative Examples 4-6

[0057] The isobutylene raw materials of Examples 1-4 and Comparative Examples 1-3 were preheated to the reaction temperature in a preheater in the presence of a nitrogen gas flow and then entered into a reactor for reaction. The reaction temperature was 250°C and the reaction pressure was 10 MPa (A). Liquid ammonia and isobutylene were mixed at a molar ratio of 2:1 and the mass space velocity of isobutylene was 3 h -1 The reaction is carried out under the following conditions, the reactor is loaded with H-BETA molecular sieve catalyst, and the product at the reactor outlet is de-lightened to obtain tert-butylamine product.

[0058] The conversion rates and selectivities measured in Examples 5-8 and Comparative Examples 4-6 are shown in the following table. The obtained tert-butylamine product was stored at room temperature for 3 months and then the product color number was tested. The results are as follows.

[0059] Isobutylene conversion tert-Butylamine selectivity Storage 3 months Product color Comparative Example 4 11.4 94.68 34 Comparative Example 5 12.3 96.89 15 Comparative Example 6 12.1 97.32 28 Example 5 12.9 99.35 6 Example 6 12.7 99.42 3 Example 7 13.4 99.21 5 Example 8 12.1 99.56 7

Claims

1. A method for preparing tert-butylamine by amination of isobutylene, characterized in that: The method comprises the following steps: preparing tert-butylamine by amination reaction of isobutylene and liquid ammonia under the action of a catalyst, wherein the methanol content in the isobutylene is 10-400 ppm, and the dimethyl ether content is 10-300 ppm.

2. The method according to claim 1, characterized in that The molar ratio of liquid ammonia to isobutylene is 1-20:1; preferably 1-10:1, more preferably 1-4:

1.

3. The method according to claim 1, characterized in that The catalyst is a molecular sieve catalyst, preferably at least one selected from the group consisting of MCM molecular sieve, H-BETA molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve and mordenite.

4. The method according to any one of claims 1 to 3, characterized in that: The reaction temperature of the amination reaction is 100-350°C, and the reaction pressure is 5-15MPaA.

5. The method according to any one of claims 1 to 4, characterized in that: The amination reaction adopts a continuous reaction, and the mass space velocity of the isobutylene feed is 3-10h -1 .

6. The method according to claim 1, characterized in that The water content in isobutylene is 10-1000ppm.

7. The method according to claim 1, characterized in that The contents of methyl formate and acetone in isobutylene are both less than or equal to 50 ppm.

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