Method for efficiently separating isobutene amination reaction mother liquor

Abstract

The invention discloses a method for efficiently separating isobutene amination reaction mother liquor, which comprises the following steps: separating the isobutene amination reaction mother liquor through a liquid-liquid separator, separating the upper layer mainly comprising liquid ammonia and the lower layer mainly comprising primarily separated liquid ammonia-isobutene-tert-butylamine ternary components, and separating the lower layer material through a multi-effect cyclone, liquid ammonia and isobutene are obtained on the upper layer, tert-butylamine and part of isobutene are obtained on the lower layer, and the isobutene is extracted from the tower top, the tert-butylamine product is extracted from the side line of the tower and heavy components extracted from the tower kettle of the rectifying tower are treated as waste liquid by controlling process parameters. The method is used for researching the ternary physical properties of liquid ammonia-isobutene-tert-butylamine, so that the steps of vaporizing liquid ammonia and then condensing and recovering the liquid ammonia in the traditional methods of rectification, steam stripping and the like can be avoided, the rectification energy consumption is greatly reduced, and meanwhile, the two-tower operation for separating isobutene and tert-butylamine is integrated into one tower, so that the benefit of the device is greatly improved, and the investment of the device is reduced.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and particularly relates to a method for efficiently separating mother liquor from an isobutylene amination reaction. Background Art

[0002] As an important chemical intermediate, tert-butylamine is mainly used in the synthesis of rubber accelerators such as sulfenamide accelerators NS (N-tert-butyl-2-benzothiazolesulfenamide) and TBSI (N-tert-butylbis-2-benzothiazolesulfenamide). At the same time, tert-butylamine is also an important pharmaceutical and pesticide intermediate, and can also be used in the fields of surfactants, synthetic resins and organic synthesis.

[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. However, due to thermodynamic limitations, the reaction conversion rate of this method is very low, and a large amount of raw materials need to be recycled.

[0005] US4929759A discloses a borosilicate molecular sieve, and it is found that after reacting for 30 minutes at 350°C, 30 MPa, and a molecular ratio of isobutylene to ammonia of 1:1.5, the selectivity is 95.7%, wherein the isobutylene conversion rate is 14.1%, and about 86% of the raw materials, i.e., isobutylene and liquid ammonia, need to be recovered.

[0006] CN112094196A discloses the preparation of tert-butylamine using a fixed bed as a reactor, using a three-way catalyst containing lanthanum and cerium noble metals, feeding isobutylene and ammonia at a molar ratio of 6:1, and the isobutylene conversion rate reaches up to about 20%. The reaction material coming out of the top of the reactor flows into the first distillation tower through a pressure regulator to obtain liquid ammonia, the second distillation tower obtains isobutylene, and the third distillation tower obtains tert-butylamine. The ratio of isobutylene to liquid ammonia is greatly excessive, and more than 80% of the raw materials need to be recycled. The whole process involves multiple distillation towers, with high energy consumption, and does not utilize industrial production.

[0007] According to the prior art, the isobutylene amination method has become the mainstream route for the industrial production of tert-butylamine due to its high atomic utilization rate and the fact that it does not involve the use and treatment of strong acids / strong bases. However, due to thermodynamic limitations, the reaction conversion rate is low, and liquid ammonia is usually greatly excessive, so a large amount of raw materials need to be separated and recycled, resulting in high energy consumption of the device.

[0008] Therefore, if an efficient separation method for isobutylene amination reaction liquid can be developed to reduce the distillation energy consumption of liquid ammonia and isobutylene, the efficiency of the device can be greatly improved, the unit consumption of products and the operating cost of the device can be reduced, the carbon emissions of the device can be reduced, and it will be more green and environmentally friendly. Summary of the invention

[0009] In order to achieve the above purpose, the present invention adopts the following technical solution:

[0010] The present invention provides a method for efficiently separating mother liquor from an isobutylene amination reaction, comprising the following steps:

[0011] (1) The crude product of the mother liquor of the isobutylene amination reaction is separated by a liquid-liquid separator, and the upper layer is liquid ammonia, and the lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation;

[0012] (2) The lower layer material obtained in step (1) is separated by a multi-effect cyclone, and liquid ammonia and isobutylene are obtained in the upper layer, which are circulated to the raw material tank, and tert-butylamine and part of isobutylene are obtained in the lower layer;

[0013] (3) The lower layer material obtained in step (2) enters a distillation tower for separation, isobutylene and a small amount of liquid ammonia are extracted from the top of the tower, tert-butylamine product is extracted from the side line of the tower, and the heavy component is extracted from the bottom of the tower and treated as waste liquid.

[0014] Preferably, the pressure of the liquid-liquid separator in step (1) is 1.5-6 MpaG, preferably 2-4 MpaG, the temperature is 30-80° C., preferably 40-60° C., and the residence time is 1-8 h, preferably 3-6 h;

[0015] Preferably, the liquid-liquid separator in step (1) is a horizontal liquid-liquid separator, a coalescer is arranged in the liquid-liquid separator, and the filter element is preferably filled with one or more of metal wire mesh filler, polypropylene fiber membrane, and polyethylene fiber membrane.

[0016] Preferably, the pressure of the multi-effect cyclone in step (2) is 1.5-6MpaG, preferably 2-4MpaG, the temperature is 30-80°C, preferably 40-60°C, and the residence time is 1-5h, preferably 2-4h;

[0017] Preferably, the multi-effect cyclone is 2-6 effects connected in series, preferably 2-4 effects connected in series;

[0018] Preferably, the pressure of the distillation tower in step (3) is 0.1-5MpaG, preferably 0.6-1.2MpaG; the reflux ratio is 0.5-5, preferably 1-3;

[0019] Preferably, the effective number of plates of the distillation tower is 10-40, preferably 15-30; the feed plates are the 10th to 38th layers, preferably the 12th to 28th layers; the side-line extraction plates are the 15th to 38th layers, preferably the 18th to 28th layers;

[0020] Preferably, the top temperature of the distillation tower is 40-90°C, preferably 50-80°C; the bottom temperature is 100-250°C, preferably 100-160°C.

[0021] In the prior art, the crude mother liquor product after the isobutylene amination reaction is usually separated into liquid ammonia and isobutylene by distillation. Under the amination reaction conditions described in the prior art (usually high temperature>200°C, high pressure>10MPa), the obtained mother liquor is a supercritical phase, a mixed state, and no phase separation. The prior art separation means for the mother liquor obtained after the amination reaction include: for example, CN104418754B uses reduced pressure vaporization and separation at the top of the tower to obtain ammonia; or CN116082162A uses a light removal tower top to obtain isobutylene and liquid ammonia, which are directly reused as raw materials without separation, and the crude tert-butylamine at the bottom of the tower is passed through a refining tower to remove the by-product diisobutylene to obtain a refined tert-butylamine product.

[0022] The applicant unexpectedly discovered that in the process of reducing the pressure and lowering the temperature of the mother liquor, when the pressure drops to 6Mpa or less and the temperature is 80°C or less, after a period of standing, the components in the mother liquor will separate into phases. Therefore, the present invention proposes that a large amount of liquid ammonia can be separated by overflowing the upper liquid. This step is basically energy-free and can avoid the traditional distillation, stripping and other methods of first vaporizing the liquid ammonia and then condensing and recovering it, which can greatly reduce the distillation energy consumption;

[0023] Furthermore, in the presence of a small amount of liquid ammonia and isobutylene, if the separation is performed by phase separation operation, the phase separation time will be greatly increased. However, the present invention proposes that liquid ammonia and isobutylene can be efficiently separated by a multi-effect cyclone, the size of the phase separator can be reduced, and isobutylene and liquid ammonia can be further separated;

[0024] Furthermore, the third step adopts a distillation separation operation. Compared with the simultaneous distillation / stripping of three components in the prior art, the first two steps have pre-separated most of the isobutylene and liquid ammonia, which can greatly reduce the energy consumption of distillation and vaporization of liquid ammonia and isobutylene, and save the operating cost of the device.

[0025] The reaction conditions used in the isobutylene amination reaction of the present invention can be selected from conventional reaction conditions in the prior art, such as a reaction temperature of 100-300° C., a reaction pressure of 3-20 MPa(G), a feed molar ratio of isobutylene to liquid ammonia of 1:(0.2-6), and a mass space velocity of isobutylene of 0.1-5 h -1 .

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention is based on the study of the ternary physical properties of liquid ammonia-isobutylene-tert-butylamine. For the crude mother liquor product after the isobutylene amination reaction, the liquid ammonia in the mother liquor is separated from isobutylene and tert-butylamine by controlling the decompression and cooling conditions, and a large amount of liquid ammonia is separated by overflow of the upper liquid, and then enters the cyclone to further separate the liquid ammonia and isobutylene. This step is basically energy-free, and then the olefin-containing mother liquor enters a comprehensive distillation tower. By controlling the process parameters, the tower top is extracted from a small amount of residual liquid ammonia and isobutylene, the tower side line is extracted from the tert-butylamine product, and the distillation tower kettle is extracted from the heavy component as waste liquid for treatment. The method described in the present invention integrates the two tower operations of separating isobutylene and tert-butylamine into one tower, which can greatly reduce the distillation energy consumption of liquid ammonia and isobutylene, and can greatly improve the device efficiency, reduce the unit consumption of products and the operating cost of the device, reduce the carbon emission of the device, and is more green and environmentally friendly. DETAILED DESCRIPTION

[0028] 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.

[0029] Catalyst: BETA (Nanhua Catalyst Co., Ltd.)

[0030] Liquid ammonia: high-purity and high-quality ammonia, purity> 99.9%;

[0031] Isobutylene: purity 99.5%;

[0032] The performance test parameters and corresponding test methods used in the embodiments and comparative examples of the present invention are as follows:

[0033] The substance contents in the examples and comparative examples of the present invention were analyzed using an Agilent GC 7890A gas chromatograph, a TCD detector was selected for online analysis, the chromatographic column was CP-VOLAMINE, the column temperature was 250°C, and the detector temperature was 300°C.

[0034] Example 1

[0035] This process uses a fixed bed reactor with BETA catalyst inside. Liquid ammonia and isobutylene are fed in a molar ratio of 2:1. The reaction mass space velocity (calculated based on the mass of isobutylene) is 2h -1, 300℃, 20MPa(G) conditions. The reaction mother liquor is reduced to 3MpaG by a regulating valve, and the temperature is reduced to 80℃ by a heat exchanger. It is separated by a horizontal liquid-liquid separator with a coalescer (wire mesh filler) with a residence time of 3h. After separation, liquid ammonia is obtained on the upper layer, which is recycled to the raw material tank for reuse. The lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation. The lower layer material is separated by a multi-effect cyclone. The cyclone pressure is 2MpaG, the temperature is 60℃, the residence time is 2h, and the cyclone adopts 3 stages in series. After separation by the cyclone, liquid ammonia and isobutylene are obtained in the upper layer, and tert-butylamine and part of isobutylene are obtained in the lower layer. The upper layer material is circulated to the raw material tank, and the tert-butylamine product containing part of isobutylene and heavy components in the lower layer enters the distillation tower. The effective number of plates of the distillation tower is 30, the feed plate is the 26th layer, the pressure of the distillation tower is 1.2MpaG, the reflux ratio is 1, the top temperature is 80°C, the bottom temperature is 150°C, isobutylene is produced from the top of the tower, and qualified tert-butylamine products are produced from the 22nd layer of the tower side line. The heavy components are produced from the distillation tower kettle and treated as waste liquid.

[0036] Example 2

[0037] This process uses a fixed bed reactor with a commercial catalyst inside. Liquid ammonia and isobutylene are fed in a molar ratio of 2:1. The reaction mass space velocity (calculated based on the mass of isobutylene) is 2h -1 , 300℃, 20MPa(G) conditions. The mother liquor of the reaction is reduced to 2MpaG by the regulating valve, and the temperature is reduced to 40℃ by the heat exchanger. It is separated by the horizontal liquid-liquid separator with coalescer (polypropylene fiber membrane), and the residence time is 5h. The upper layer after separation is liquid ammonia, which is recycled to the raw material tank for reuse. The lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation. The lower layer material is separated by a multi-effect cyclone. The cyclone pressure is 2MpaG, the temperature is 40℃, the residence time is 2h, and the cyclone adopts 4 stages in series. After separation by the cyclone, liquid ammonia and isobutylene are obtained in the upper layer, and tert-butylamine and part of isobutylene are obtained in the lower layer. The upper layer material is circulated to the raw material tank, and the tert-butylamine product containing part of isobutylene and heavy components in the lower layer enters the distillation tower. The effective number of plates of the distillation tower is 16, the feed plate is the 13th layer, the pressure of the distillation tower is 0.6MpaG, the reflux ratio is 1, the top temperature is 50°C, the bottom temperature is 130°C, isobutylene is produced from the top of the tower, and qualified tert-butylamine products are produced from the 12th layer of the tower side line. The heavy components are produced from the distillation tower kettle and treated as waste liquid.

[0038] Example 3

[0039] This process uses a fixed bed reactor with a commercial catalyst inside. Liquid ammonia and isobutylene are fed in a molar ratio of 2:1. The reaction mass space velocity (calculated based on the mass of isobutylene) is 2h -1, 300℃, 20MPa(G) conditions. The reaction mother liquor reduces the system pressure to 4MpaG through a regulating valve, drops the temperature to 50℃ through a heat exchanger, and is separated through a horizontal liquid-liquid separator with a coalescer (wire mesh filler) with a residence time of 6h. After separation, the upper layer is liquid ammonia, which is recycled to the raw material tank for reuse. The lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation. The lower layer material is separated by a multi-effect cyclone. The cyclone pressure is 3MpaG, the temperature is 50℃, the residence time is 2h, and the cyclone adopts two stages in series. After separation by the cyclone, liquid ammonia and isobutylene are obtained in the upper layer, and tert-butylamine and part of isobutylene are obtained in the lower layer. The upper layer material is circulated to the raw material tank, and the tert-butylamine product containing part of isobutylene and heavy components in the lower layer enters the distillation tower. The effective number of plates of the distillation tower is 25, the feed plate is the 21st layer, the pressure of the distillation tower is 0.9MpaG, the reflux ratio is 3, the top temperature is 67°C, the bottom temperature is 100°C, isobutylene is produced from the top of the tower, and qualified tert-butylamine products are produced from the 19th layer through the side line of the tower. The heavy components are produced from the bottom of the distillation tower and treated as waste liquid.

[0040] Example 4

[0041] This process uses a fixed bed reactor with a commercial catalyst inside. Liquid ammonia and isobutylene are fed in a molar ratio of 2:1. The reaction mass space velocity (calculated based on the mass of isobutylene) is 2h -1 , 300℃, 20MPa(G) conditions. The mother liquor of the reaction is reduced to 3MpaG by the regulating valve, and the temperature is reduced to 60℃ by the heat exchanger. It is separated by the horizontal liquid-liquid separator with a coalescer (polyethylene fiber membrane) with a residence time of 4h. The upper layer after separation is liquid ammonia, which is recycled to the raw material tank for reuse. The lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation. The lower layer material is separated by a multi-effect cyclone. The cyclone pressure is 3MpaG, the temperature is 60℃, the residence time is 4h, and the cyclone adopts 2 stages in series. After separation by the cyclone, liquid ammonia and isobutylene are obtained in the upper layer, and tert-butylamine and part of isobutylene are obtained in the lower layer. The upper layer material is circulated to the raw material tank, and the tert-butylamine product containing part of isobutylene and heavy components in the lower layer enters the distillation tower. The effective number of plates of the distillation tower is 30, the feed plate is the 26th layer, the pressure of the distillation tower is 1.2MpaG, the reflux ratio is 2.5, the top temperature is 80°C, the bottom temperature is 160°C, isobutylene is produced from the top of the tower, and qualified tert-butylamine products are produced from the 23rd layer of the tower side line. The heavy components are produced from the distillation tower kettle and treated as waste liquid.

[0042] Example 5

[0043] This process uses a fixed bed reactor with a commercial catalyst inside. Liquid ammonia and isobutylene are fed in a molar ratio of 2:1. The reaction mass space velocity (calculated based on the mass of isobutylene) is 2h -1, 300℃, 20MPa(G) conditions. The reaction mother liquor reduces the system pressure to 4MpaG through a regulating valve, drops the temperature to 70℃ through a heat exchanger, and is separated by a horizontal liquid-liquid separator with a coalescer (polypropylene fiber membrane) with a residence time of 3h. After separation, the upper layer is liquid ammonia, which is recycled to the raw material tank for reuse. The lower layer is the ternary component of liquid ammonia-isobutylene-tert-butylamine after preliminary separation. The lower layer material is separated by a multi-effect cyclone. The cyclone pressure is 4MpaG, the temperature is 70℃, the residence time is 3h, and the cyclone adopts 3 stages in series. After separation by the cyclone, liquid ammonia and isobutylene are obtained in the upper layer, and tert-butylamine and part of isobutylene are obtained in the lower layer. The upper layer material is circulated to the raw material tank, and the tert-butylamine product containing part of isobutylene and heavy components in the lower layer enters the distillation tower. The effective number of plates of the distillation tower is 28, the feed plate is the 24th layer, the pressure of the distillation tower is 0.8MpaG, the reflux ratio is 2, the top temperature is 62°C, the bottom temperature is 100°C, isobutylene is produced from the top of the tower, and qualified tert-butylamine products are produced from the 22nd layer of the tower side line. The heavy components are produced from the distillation tower kettle and treated as waste liquid.

[0044] Comparative Example 1

[0045] The same as Example 1, except that the liquid-liquid separator separation operation is not performed, the mother liquor directly enters the cyclone, the upper layer is a mixture of liquid ammonia and isobutylene, and the lower layer is a crude tert-butylamine product and a small amount of a mixture of liquid ammonia and isobutylene.

[0046] Comparative Example 2

[0047] The same as Example 1, except that the cyclone separation operation is not performed, and the preliminary separated liquid ammonia-isobutylene-tert-butylamine material obtained in the lower layer of the liquid-liquid separator is directly fed into the distillation tower, and the conditions of the distillation tower are the same as those in Example 1.

[0048] Comparative Example 3

[0049] Compared with Example 1, the difference is that the cyclone is a single-effect cyclone, only one cyclone (stage 1) is used, and the rest of the operations are the same as Example 1.

[0050] The compositions of the various materials separated from the above examples and comparative examples are shown in the table below, where the units are weight percentages.

[0051]

[0052]

[0053] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for efficiently separating mother liquor from isobutylene amination reaction, characterized in that: The steps include: (1) the crude product of the mother liquor of the isobutylene amination reaction is separated by a liquid-liquid separator, and liquid ammonia is obtained in the upper layer; (2) The material in the lower layer of the liquid-liquid separator is separated by a multi-effect cyclone, and liquid ammonia and isobutylene are obtained in the upper layer; (3) The material in the lower layer of the multi-effect cyclone enters the distillation tower for separation, and the tert-butylamine product is taken out from the side line of the tower.

2. The method according to claim 1, characterized in that The pressure of the liquid-liquid separator in step (1) is 1.5-6MpaG, preferably 2-4MpaG, the temperature is 30-80°C, preferably 40-60°C, and the residence time is 1-8h, preferably 3-6h.

3. The method according to claim 1 or 2, characterized in that: The liquid-liquid separator in step (1) is a horizontal liquid-liquid separator, preferably equipped with a coalescer.

4. The method according to claim 3, characterized in that The coalescer filter element is filled with one or more of metal mesh fillers, polypropylene fiber membranes, and polyethylene fiber membranes.

5. The method according to claim 1, characterized in that The pressure of the multi-effect cyclone in step (2) is 1.5-6MpaG, preferably 2-4MpaG, the temperature is 30-80°C, preferably 40-60°C, and the residence time is 1-5h, preferably 2-4h.

6. The method according to claim 1 or 5, characterized in that: The multi-effect cyclones are 2-6 effects connected in series, preferably 2-4 effects connected in series.

7. The method according to claim 1, characterized in that The pressure of the distillation tower in step (3) is 0.1-5MpaG, preferably 0.6-1.2MpaG; the reflux ratio is 0.5-5, preferably 1-3.

8. The method according to claim 1 or 7, characterized in that: The effective number of plates of the distillation tower in step (3) is 10-40, preferably 15-30; the feed plates are the 10th to 38th layers, preferably the 12th to 28th layers; and the side-line extraction plates are the 15th to 38th layers, preferably the 18th to 28th layers.

9. The method according to claim 1, characterized in that: The top temperature of the distillation tower in step (3) is 40-90°C, preferably 50-80°C; the bottom temperature is 100-250°C, preferably 100-160°C.

10. The method according to any one of claims 1 to 9, characterized in that: The liquid ammonia obtained in the upper layer of the liquid-liquid separator in step (1), the liquid ammonia obtained in the upper layer of the multi-effect cyclone in step (2), and isobutylene are refluxed to the raw material tank for the isobutylene amination reaction.

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