A method and system for treating tail gas containing trifluoromethanesulfonic acid

Abstract

The present invention discloses a method and system for treating tail gas containing trifluoromethanesulfonic acid. The system includes a first fixed-bed adsorption tower, a second fixed-bed adsorption tower, an absorption tower, a first feed pump, a membrane assembly, a second feed pump, a heat exchanger, a vacuum evaporation crystallizer, a sedimentation tank, and a circulation pump. A first compressor is provided on the top of the first fixed-bed adsorption tower, and a second compressor is provided on the top of the second fixed-bed adsorption tower. The outlets of the first compressor and the second compressor are respectively connected to the absorption tower. A spray device and a packing layer are provided in the absorption tower. The first feed pump is connected to the spray device. A waste gas discharge port is provided on the top of the absorption tower, and a drain pipe is provided at the bottom to be connected to the membrane assembly. The permeate port is connected to the sedimentation tank, and the residual port is connected to the second feed pump. The waste gas is then passed through the heat exchanger and then merged into the vacuum evaporation crystallizer together with the feed liquid from the circulation pump. The entire process system greatly improves the atomic utilization rate, and while the tail gas is treated in a green manner, solid-supported trifluoromethanesulfonic acid is produced as a by-product, meeting the requirements of sustainable development.

Description

Technical Field

[0001] The present invention belongs to the field of green chemical tail gas treatment, and in particular relates to a method and system for treating tail gas containing trifluoromethanesulfonic acid. Background Art

[0002] Immobilizing trifluoromethanesulfonic acid requires removing the physically adsorbed trifluoromethanesulfonic acid by passing dry nitrogen through the exhaust. This process then contains a small amount of trifluoromethanesulfonic acid and unremoved solvent vapor. Existing technology involves directly dissolving the solution in a large amount of alkali solution, resulting in a waste of solvent and trifluoromethanesulfonic acid. This also requires a large processing volume, significantly reducing atomic utilization and increasing waste gas treatment costs. This is environmentally unfriendly and does not meet the current requirements of green chemistry and sustainable development. Therefore, process improvements are necessary to increase atomic utilization. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention aims to provide a method and system for treating tail gas containing trifluoromethanesulfonic acid, so that the tail gas can be treated in a green and environmentally friendly manner, the amount of alkali solution used can be greatly reduced, and a high-value-added immobilized trifluoromethanesulfonic acid product can be produced as a by-product and potassium trifluoromethanesulfonate can be recovered, thereby reducing costs and improving additional economic benefits.

[0004] A method for treating tail gas containing trifluoromethanesulfonic acid comprises sequentially using a fixed-bed adsorption tower, an absorption tower, a membrane assembly, a settling tank, and a reduced-pressure evaporation crystallizer to remove trifluoromethanesulfonic acid and solvent from the tail gas containing immobilized trifluoromethanesulfonic acid by adsorption, thereby achieving green and environmentally friendly treatment of the tail gas and producing an immobilized trifluoromethanesulfonic acid product as a by-product.

[0005] The method for treating tail gas containing trifluoromethanesulfonic acid comprises the following steps: transporting tail gas containing trifluoromethanesulfonic acid and a solvent to a fixed-bed adsorption tower double-tower system, wherein one tower performs chemical adsorption at normal pressure, and the other tower performs physical desorption at reduced pressure; a compressor is provided at the top of each tower to pressurize the decompressed gas; the tower filler is a silica material, which chemically adsorbs trifluoromethanesulfonic acid at 150° C., thereby grafting trifluoromethanesulfonic acid groups onto the surface of the silica material; when adsorption reaches saturation, switching valves for the tail gas and fresh nitrogen, performing a decompression operation, desorbing the physically adsorbed trifluoromethanesulfonic acid and solvent, and outputting a stable immobilized trifluoromethanesulfonic acid product from the tower filler; The tail gas from the double-tower system is sent to the absorption tower, where the potassium acetate in the absorption liquid reacts with the remaining trifluoromethanesulfonic acid to produce potassium trifluoromethanesulfonate and acetic acid. The solvent in the tail gas is also enriched, and the absorbed gas is discharged from the top of the absorption tower in compliance with the discharge standards. The enriched liquid is discharged from the top of the absorption tower and sent to the membrane assembly for reverse osmosis. The permeate is water and solvent, which is sent to the sedimentation tank. The organic solvent and water are separated into water and oil. The upper organic solvent is dried and recycled. The retentate after reverse osmosis is a concentrated potassium trifluoromethanesulfonate and acetic acid solution, which is sent by a feed pump to a reduced pressure evaporation crystallizer. The potassium trifluoromethanesulfonate crystallizes and is discharged from the bottom outlet of the tower, and the acetic acid is discharged from the top of the tower by a steam compressor.

[0006] A trifluoromethanesulfonic acid-containing tail gas treatment system comprises a first fixed-bed adsorption tower, a second fixed-bed adsorption tower, an absorption tower, a first feed pump, a membrane assembly, a second feed pump, a heat exchanger, a reduced-pressure evaporation crystallizer, a settling tank, and a circulation pump;

[0007] The first fixed bed adsorption tower is provided with a first compressor on the top, and the second fixed bed adsorption tower is provided with a second compressor on the top.

[0008] The outlets of the first compressor and the second compressor are respectively connected to the absorption tower, which is equipped with a spray device and a packing layer. The first feed pump is connected to the spray device. The top of the absorption tower is provided with an exhaust gas discharge port, and the bottom is provided with a drain pipe connected to the membrane assembly. The permeate port is connected to the sedimentation tank, and the residual port is connected to the second feed pump. After passing through the heat exchanger, the feed liquid from the circulating pump is combined with the reduced pressure evaporation crystallizer.

[0009] The operating temperature of the first fixed bed adsorption tower and the second fixed bed adsorption tower is 150°C.

[0010] The fillers of the first fixed bed adsorption tower and the second fixed bed adsorption tower are silicon dioxide materials.

[0011] The absorption tower uses potassium acetate solution as the absorption liquid, and the first feed pump is a feed pump for potassium acetate solution.

[0012] The reduced pressure evaporation crystallizer comprises an evaporation chamber and a crystallization chamber. The top of the evaporation chamber is provided with a steam discharge port and a steam compressor, the bottom of the evaporation chamber is provided with a central downcomer, and the bottom of the crystallization chamber is provided with a potassium trifluoromethanesulfonate discharge port.

[0013] The beneficial effects of the present invention are:

[0014] 1) A fixed-bed reactive adsorption double-tower system is used, and the internal filler is silica material, so that most of the trifluoromethanesulfonic acid in the tail gas undergoes chemical adsorption, and the trifluoromethanesulfonic acid groups are immobilized on the surface of the silica material, producing immobilized trifluoromethanesulfonic acid as a by-product, greatly improving the atomic utilization rate. The physically adsorbed trifluoromethanesulfonic acid and solvent are desorbed under reduced pressure, improving product quality.

[0015] 2) A potassium acetate aqueous solution is used as the absorption liquid in the absorption tower to completely absorb the trifluoromethanesulfonic acid and most of the solvent, so that the waste gas meets the emission standards and generates a by-product potassium trifluoromethanesulfonate liquid;

[0016] 3) The installation of membrane modules further concentrates the feed liquid and separates water and solvent. At this time, the concentration of potassium trifluoromethanesulfonate solution is greatly increased. The installation of sedimentation tanks allows the solvent to be recycled and reused, solving the wastewater pollution problem.

[0017] 4) The setting of the reduced pressure evaporation crystallizer reduces energy consumption, removes acetic acid impurities through reduced pressure evaporation, improves the quality of potassium trifluoromethanesulfonate, and increases additional economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural diagram of a trifluoromethanesulfonic acid tail gas treatment process system.

[0019] In the figure: first compressor 1, first fixed bed adsorption tower 2, second compressor 3, second fixed bed adsorption tower 4, absorption tower 5, spray device 6, packing layer 7, first feed pump 8, membrane assembly 9, second feed pump 10, gas-liquid heat exchanger 11, steam compressor 12, reduced pressure evaporation crystallizer 13, evaporation chamber 14, crystallization chamber 15, sedimentation tank 16, organic layer 17, water layer 18, circulation pump 19, central downcomer 20.

[0020] Figure 2 This is the infrared characterization of the adsorbent silica and the by-product immobilized trifluoromethanesulfonic acid. DETAILED DESCRIPTION

[0021] There are a variety of support materials available for the immobilization of trifluoromethanesulfonic acid. However, silica has a large specific surface area and is rich in silanol groups. Trifluoromethanesulfonic acid reacts with the silanol groups on the silica surface at 150°C, grafting the trifluoromethanesulfonic acid groups onto the silica surface to produce an immobilized trifluoromethanesulfonic acid product. Therefore, a considerable amount of trifluoromethanesulfonic acid contained in exhaust gas can be chemically adsorbed on silica, resulting in the simultaneous production of an immobilized trifluoromethanesulfonic acid product as a byproduct of exhaust gas treatment.

[0022] Fixed-bed adsorption towers are the most widely used adsorption equipment, featuring a simple structure, easy processing, flexible operation, and easily recyclable internal fillers. The adsorption and regeneration processes in fixed beds are typically performed alternately within two adsorption towers. During adsorbent regeneration, dry nitrogen is introduced to reduce pressure, removing physically adsorbed solvent and trifluoromethanesulfonic acid.

[0023] Potassium trifluoromethanesulfonate can be used to study the mixed base effect and short-range interaction in polyethylene oxide electrolytes and the electrochemical behavior of glassy carbon in superacidic media. It has good commercial value. The existing technology is to prepare it by neutralizing warm trifluoromethanesulfonic acid aqueous solution with potassium carbonate.

[0024] Membrane separation is an efficient separation process with simple process, low energy consumption, easy operation and wide application range. It is often used in the preparation of pure water. The permeate is solvent and water, and the retentate is solute, so as to achieve the purpose of concentrating the solution.

[0025] Reduced pressure evaporation crystallization integrates reduced pressure, evaporation and crystallization operations into one, which simplifies the process, reduces energy consumption and improves grain quality.

[0026] The present invention integrates the above equipment to provide a trifluoromethanesulfonic acid-containing tail gas treatment process system, which realizes green and environmentally friendly treatment of tail gas and produces solid-supported trifluoromethanesulfonic acid product and potassium trifluoromethanesulfonate as by-products, meeting the current requirements of green chemistry and sustainable development.

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, a process system for treating tail gas containing trifluoromethanesulfonic acid comprises a first compressor 1, a first fixed-bed adsorption tower 2, a second compressor 3, a second fixed-bed adsorption tower 4, an absorption tower 5, a spray device 6, a packing layer 7, a first feed pump 8, a membrane assembly 9, a second feed pump 10, a gas-liquid heat exchanger 11, a first steam compressor 12, a reduced-pressure evaporation crystallizer 13, a settling tank 16, a circulation pump 19, and a central downcomer 20.

[0029] The tail gas containing trifluoromethanesulfonic acid is transported to a fixed-bed adsorption reaction double-tower system. By switching the corresponding valves, one tower performs chemical adsorption at normal pressure, while the other tower performs physical desorption at reduced pressure. A compressor is provided at the top of each tower. Unreacted trifluoromethanesulfonic acid and solvent gas are enriched and transported to an absorption tower 5. A spray device 6 and a packing layer 7 are provided in the absorption tower 5. A first feed pump 8 is connected to the spray device 6. A waste gas discharge port is provided at the top of the absorption tower 5, and a drain pipe is provided at the bottom to be connected to a membrane assembly 9. The permeate port of the membrane assembly is connected to a settling tank 16. The residual port of the membrane assembly is connected to a second feed pump 10. After being heated by a heat exchanger 11, the residual port of the membrane assembly and the feed liquid from the circulating pump 19 are merged into a reduced pressure evaporation crystallizer 13. A steam discharge port and a steam compressor 12 are provided at the top of the reduced pressure evaporation crystallizer 13. A central downcomer 20 is provided in the reduced pressure evaporation crystallizer 13, and a potassium trifluoromethanesulfonate discharge port is provided at the bottom. Example

[0030] The system primarily operates by transferring tail gas containing trifluoromethanesulfonic acid and solvent to a fixed-bed reactive adsorption dual-tower system (first fixed-bed adsorption tower 2 and second fixed-bed adsorption tower 4). One tower operates at atmospheric pressure, while the other operates at reduced pressure. By switching valves, the atmospheric pressure tower switches to reduced pressure desorption, and the reduced pressure tower switches to atmospheric pressure adsorption. The towers are filled with silica, which chemically adsorbs trifluoromethanesulfonic acid at 150°C. The mechanism is shown below:

[0031]

[0032] The trifluoromethanesulfonic acid group is immobilized on the surface of the silica material. When the adsorption reaches saturation, the valves for the exhaust gas and fresh dry nitrogen are switched, and the pressure is reduced to desorb a very small amount of physically adsorbed trifluoromethanesulfonic acid and solvent. The filler in the tower produces a stable immobilized trifluoromethanesulfonic acid product. The infrared characterization of the adsorbent silica and the by-product immobilized trifluoromethanesulfonic acid is as follows: Figure 2 shown.

[0033] The tops of the two towers are equipped with a first compressor 1 and a second compressor 3, respectively. They pressurize the tail gas from the vacuum tower to atmospheric pressure, mix it with the tail gas from the atmospheric tower, and transport it to the absorption tower 5. Potassium acetate absorption liquid is pumped into the absorption tower 5 via a first feed pump 8. Inside the absorption tower 5, a spray device 6 and a packing layer 7 are installed. Potassium acetate reacts with the remaining trifluoromethanesulfonic acid to produce potassium trifluoromethanesulfonate and acetic acid, enriching the solvent in the tail gas. The absorbed gas is discharged from the top of the tower to meet the discharge standards. The enriched liquid is discharged from the top of the tower and sent to the membrane module 9 for reverse osmosis. The permeate, consisting of water and solvent, is sent to a settling tank 16, where the organic solvent and water undergo water-oil separation, forming an organic solvent layer 17 and an aqueous layer 18. The upper organic solvent layer is dried and recycled. The retentate after reverse osmosis is a concentrated solution of potassium triflate and acetic acid, which is fed by a second feed pump 10 to a heat exchanger 11. After being heated with steam, it is fed to a vacuum evaporation crystallizer 13. Within an evaporation chamber 14, water is partially vaporized to produce supersaturation. The supersaturated solution then flows through a central downcomer 20 to the bottom of a crystallization chamber 15. Within the crystallization chamber, potassium triflate crystallizes and is discharged from the bottom product outlet. A steam first compressor 12 is installed at the top of the crystallizer to perform a vacuum evaporation operation and extract the acetic acid vapor.

[0034] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A trifluoromethanesulfonic acid-containing tail gas treatment system, characterized in that: It comprises a first fixed bed adsorption tower (2), a second fixed bed adsorption tower (4), an absorption tower (5), a first feed pump (8), a membrane assembly (9), a second feed pump (10), a heat exchanger (11), a reduced pressure evaporation crystallizer (13), a settling tank (16), and a circulation pump (19); A first compressor (1) is provided on the top of the first fixed bed adsorption tower (2), and a second compressor (3) is provided on the top of the second fixed bed adsorption tower (4). The outlets of the first compressor (1) and the second compressor (3) are respectively connected to an absorption tower (5), a spray device (6) and a packing layer (7) are provided in the absorption tower (5), a first feed pump (8) is connected to the spray device (6), a waste gas discharge port is provided at the top of the absorption tower (5), a liquid discharge pipe is provided at the bottom thereof and is connected to a membrane assembly (9), a permeate port is connected to a settling tank (16), and a residual port is connected to a second feed pump (10), and the liquid and the feed from the circulation pump (19) are passed through a heat exchanger (11) and then flow into a reduced pressure evaporation crystallizer (13); The fillers of the first fixed bed adsorption tower (2) and the second fixed bed adsorption tower (4) are silicon dioxide materials; The reduced pressure evaporation crystallizer (13) comprises an evaporation chamber (14) and a crystallization chamber (15). The top of the evaporation chamber (14) is provided with a steam discharge port and a steam compressor (12). The bottom of the evaporation chamber (14) is provided with a central downcomer (20). The bottom of the crystallization chamber (15) is provided with a potassium trifluoromethanesulfonate discharge port.

2. The system according to claim 1, wherein: The operating temperature of the first fixed bed adsorption tower (2) and the second fixed bed adsorption tower 4 is 150°C.

3. The system according to claim 1, wherein: The absorption tower (5) uses potassium acetate solution as the absorption liquid, and the first feed pump (8) is a feed pump for the potassium acetate solution.

4. A method for treating tail gas containing trifluoromethanesulfonic acid, characterized in that: The system according to claim 1 is used to sequentially adopt a fixed bed adsorption tower, an absorption tower, a membrane module, a sedimentation tank, and a reduced pressure evaporation crystallizer for treatment to adsorb and remove trifluoromethanesulfonic acid and solvent from the tail gas of the immobilized trifluoromethanesulfonic acid, thereby achieving green and environmentally friendly treatment of the tail gas and producing the immobilized trifluoromethanesulfonic acid product as a by-product.

5. A method for treating tail gas containing trifluoromethanesulfonic acid according to claim 4, characterized in that: The steps are as follows: the tail gas containing trifluoromethanesulfonic acid and solvent is transported to a fixed-bed adsorption tower double-tower system, one tower performs chemical adsorption at normal pressure, and the other tower performs physical desorption at reduced pressure. A compressor is installed at the top of each tower to pressurize the decompressed gas. The tower filler is a silica material, which undergoes chemical adsorption with trifluoromethanesulfonic acid at 150°C, and the trifluoromethanesulfonic acid group is grafted onto the surface of the silica material. When the adsorption reaches saturation, the on-off valves of the tail gas and fresh nitrogen are switched, and the pressure is reduced to desorb the physically adsorbed trifluoromethanesulfonic acid and solvent, and the tower filler produces a stable immobilized trifluoromethanesulfonic acid product; the tail gas from the double-tower system, The product is sent to the absorption tower, where the potassium acetate in the absorption liquid reacts with the remaining trifluoromethanesulfonic acid to generate potassium trifluoromethanesulfonate and acetic acid. The solvent in the tail gas is also enriched, and the absorbed gas is discharged from the top of the absorption tower in compliance with the discharge standards. The enriched liquid is discharged from the top of the absorption tower and sent to the membrane assembly for reverse osmosis. The permeate is water and solvent, which is sent to the sedimentation tank. The organic solvent and water are separated into water and oil, and the upper organic solvent is dried and recycled. The retentate after reverse osmosis is a concentrated potassium trifluoromethanesulfonate and acetic acid solution, which is sent to the reduced pressure evaporation crystallizer by the feed pump. The potassium trifluoromethanesulfonate crystallizes and is discharged from the bottom outlet of the tower, and the acetic acid is discharged from the top of the tower by the steam compressor.

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