A method for purifying food-grade carbon dioxide

Abstract

The present invention provides a method for purifying food-grade carbon dioxide, and relates to the technical field of food processing. The purification method provided by the present invention comprises the following steps: pressurizing the raw gas and then desulfurizing it by physical adsorption to obtain desulfurized gas; passing the desulfurized gas through a dehydrogenation unit in a dehydrogenation purification tower to obtain purified gas; cooling and drying the purified gas, condensing and liquefying it, and then purifying it by distillation to obtain food-grade carbon dioxide; the preparation method of the dehydrogenation unit comprises: stirring and dissolving zirconium salt and organic ligand to obtain a ligand mixed liquid, and separating it after hydrothermal treatment to obtain a first carrier; calcining dopamine after polymerization to obtain carbide, and mixing the carbide with an alkaline metal salt to roast and cool to obtain a second carrier; dispersing the first carrier and the second carrier to obtain a modified carrier; immersing the modified carrier in a metal salt solution, separating and drying to obtain a dehydrogenation unit. The present invention can purify the carbon dioxide raw gas, remove hydrocarbon impurity gases, and thus improve the efficiency of purifying carbon dioxide.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for purifying food-grade carbon dioxide. Background Art

[0002] Carbon dioxide is a gaseous compound and a common greenhouse gas. It is a colorless, odorless, and non-flammable gas at room temperature. In the field of food processing, food-grade carbon dioxide is an important resource and plays an important role in food freezing, beverage carbonation, tobacco expansion, etc. However, since the carbon dioxide obtained from flue gas contains a large amount of dust, moisture, sulfur dioxide, nitrogen and other impurities, it cannot meet the quality standards of food-grade carbon dioxide. Therefore, the carbon dioxide must be purified during the preparation process.

[0003] The prior art provides a method for purifying food-grade carbon dioxide, in which the gas passing through the membrane unit is subjected to a dehydration and desulfurization tower treatment, and then subjected to a low-temperature distillation tower to obtain food-grade carbon dioxide. By separating the gas through the membrane unit, the separation of impurity gases such as nitrogen, oxygen, and water in the gas can be effectively reduced, thereby effectively improving the purification efficiency of carbon dioxide. However, when the gas passes through the membrane unit, the operating temperature usually reaches 100-500°C, and the operating pressure can reach 100-2000kPa, which can easily cause damage to the membrane unit, thereby affecting the purification efficiency of food-grade carbon dioxide. Therefore, it is urgent to provide a solution to improve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a method for purifying food-grade carbon dioxide, which can purify carbon dioxide raw gas and remove hydrocarbon impurity gases, thereby improving the efficiency of purifying carbon dioxide.

[0005] The invention provides a method for purifying food-grade carbon dioxide, comprising the following steps: pressurizing raw gas and then subjecting it to physical adsorption desulfurization to obtain desulfurized gas; subjecting the desulfurized gas to a dehydrogenation unit in a dehydrogenation purification tower to obtain purified gas; cooling and drying the purified gas, condensing and liquefying it, and subjecting it to rectification and purification to obtain food-grade carbon dioxide; wherein the preparation method of the dehydrogenation unit comprises: stirring and dissolving zirconium salt and organic ligand to obtain a ligand mixed solution, subjecting the ligand mixed solution to a hydrothermal reaction at 110-120°C for 20-25h, separating it, and drying it at 80-90°C to obtain a first carrier; polymerizing dopamine in an alkaline environment to obtain polydopamine, calcining it at 800-900°C to obtain carbide, mixing the carbide with an alkaline metal salt, roasting it, and cooling it to obtain a second carrier; dispersing the first carrier and the second carrier in ethanol, adding a binder, ultrasonically dispersing it, and evaporating the solvent to obtain a modified carrier; and immersing the modified carrier in a metal salt solution, separating and drying it to obtain the dehydrogenation unit.

[0006] The purification method provided by the present invention, when pressurizing the raw gas, increases the temperature of the raw gas during the compression process, and can adsorb sulfides in the raw gas after physical adsorption, and then passes the desulfurized gas through a dehydrogenation unit to remove hydrocarbon substances in it, thereby generating carbon dioxide, which is beneficial to improving the yield of carbon dioxide.

[0007] In addition, when preparing the dehydrocarbon unit, the zirconium salt and the organic ligand are hydrothermally reacted, which helps to improve the crystallinity and structural stability of the composite. The prepared first carrier has good surface properties and structural stability, and has good adsorption and separation properties. After the polydopamine formed by polymerization under alkaline conditions is carbonized, it can form a carbide with a high specific surface area. The introduction of metal elements into it can increase the number of active sites, improve the adsorption and separation capabilities, and can also catalyze the oxidation of hydrocarbon gases in the flue gas into carbon dioxide gas, which helps to purify the carbon dioxide.

[0008] In addition, after the first carrier and the second carrier are bonded together under the action of an adhesive, the bonding strength between the first carrier and the second carrier can be effectively improved, a stable carrier structure can be formed, and the comprehensive performance of the dehydrogenation unit can be improved. At the same time, after the metal salt is loaded on the modified carrier, the metal ions react with the surface of the modified carrier, which can not only further improve the bonding performance between the first carrier and the second carrier, but also increase the service life of the dehydrogenation unit. After modification with metal elements, the adsorption and separation capabilities of the dehydrogenation unit can be improved, and impurity gases in the flue gas can be efficiently removed.

[0009] Optionally, when pressurizing the raw gas, the raw gas is introduced into a compressor and pressurized to 23-27 ba in multiple stages.

[0010] Optionally, the raw gas is pressurized and then passed into a fine desulfurization tower, and desulfurized gas is obtained after physical adsorption desulfurization treatment by a desulfurizer; the desulfurizer includes at least one of activated carbon, zeolite molecular sieve, and activated alumina.

[0011] Optionally, the desulfurized gas is passed into a dehydrogenation unit at 450-500° C. in a dehydrogenation purification tower to produce purified gas.

[0012] Optionally, in the process of stirring and dissolving the zirconium salt and the organic ligand to obtain the ligand mixture: the mass ratio of the zirconium salt to the organic ligand is 1:(6-8).

[0013] Optionally, in the process of stirring and dissolving the zirconium salt and the organic ligand to obtain the ligand mixture: the zirconium salt includes at least one of zirconium tetrachloride, zirconium nitrate, zirconium oxychloride, zirconium carbonate and zirconium hydroxide.

[0014] Optionally, in the process of stirring and dissolving the zirconium salt and the organic ligand to obtain the ligand mixture: the organic ligand includes at least one of 2-methylimidazole, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 2,2'-bipyridine and terephthalic acid.

[0015] Optionally, in the process of stirring and dissolving the zirconium salt and the organic ligand to obtain a ligand mixture solution: the solvent in the ligand mixture solution includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, diformate, and ethylene glycol methyl ether.

[0016] Optionally, the process of preparing polydopamine by polymerizing dopamine in an alkaline environment includes: dissolving dopamine in deionized water to prepare a dopamine solution, adjusting the pH of the dopamine solution to 8-9 using an alkaline regulator, and then ultrasonically reacting at 50-60° C. for 10-14 hours to obtain the polydopamine solution.

[0017] Optionally, in the process of mixing the carbide with the alkaline metal salt and roasting them: the alkaline metal salt includes at least one of potassium carbonate, sodium bicarbonate, sodium phosphate, potassium hydroxide and sodium hydroxide.

[0018] Optionally, during the process of mixing and roasting the carbide and the alkaline metal salt, the mass ratio of the carbide to the alkaline metal salt is 1:(0.3-0.5).

[0019] Optionally, in the process of mixing the carbide and the alkaline metal salt and roasting them: the alkaline metal salt is dissolved to prepare an alkaline salt solution, the carbide is put into the alkaline salt solution and then boiled to evaporate the solvent to obtain a mixed load, and the mixed load is roasted at 700-800°C for 2-4h.

[0020] Optionally, when the first carrier and the second carrier are dispersed in ethanol, the mass ratio of the first carrier to the second carrier is 1:(0.8-1.2).

[0021] Optionally, the adhesive includes at least one of sodium silicate, zinc phosphate, and aluminum dihydrogen phosphate.

[0022] Optionally, the mass ratio of the first carrier, the second carrier and the adhesive is 1:(0.8-1.2):(0.1-0.3).

[0023] Optionally, when the modified carrier is immersed in a metal salt solution and separated and dried to obtain a dehydrogenation unit, the method includes: immersing the modified carrier in a metal salt solution with a solid-liquid ratio of 0.04-0.06 g / mL, separating after ultrasonic dispersion at 60-80°C for 20-25 hours, washing and drying, and then reducing under a hydrogen atmosphere at 300-350°C to obtain a dehydrogenation unit.

[0024] Optionally, the concentration of carbon dioxide in the food-grade carbon dioxide is ≥99.999%. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0026] The present invention provides a method for purifying food-grade carbon dioxide, comprising the following steps:

[0027] S1, pressurizing the raw gas and then desulfurizing it by physical adsorption to obtain desulfurized gas;

[0028] S2, passing the desulfurized gas through a dehydrogenation unit in a dehydrogenation purification tower to obtain purified gas;

[0029] S3. Cooling and drying the purified gas, condensing and liquefying it, and then purifying it through distillation to obtain food-grade carbon dioxide.

[0030] In fact, when executing step S1, the raw gas is passed into the compressor and pressurized to 23-27ba in multiple stages. In addition, the temperature of the raw gas increases during the compression process, and a small amount of carbonated condensed water is produced after the raw gas is cooled by the water cooler, which can be directly discharged to the sewage area.

[0031] In fact, the preparation method of the dehydrogenation unit used in step S1 comprises the following steps:

[0032] Y1. Stirring and dissolving the zirconium salt and the organic ligand to obtain a ligand mixture, subjecting the ligand mixture to a hydrothermal reaction at 110-120° C. for 20-25 hours, separating the mixture, and drying the mixture at 80-90° C. to obtain a first carrier;

[0033] Y2. Polydopamine is obtained by polymerizing dopamine in an alkaline environment, and carbide is obtained by calcining at 800-900° C. The carbide is mixed with an alkaline metal salt, calcined, and cooled to obtain a second carrier;

[0034] Y3, dispersing the first carrier and the second carrier in ethanol, adding a binder, performing ultrasonic dispersion, and evaporating the solvent to obtain a modified carrier;

[0035] Y4. Immerse the modified carrier in a metal salt solution, separate and dry it to obtain a dehydrogenation unit.

[0036] In some embodiments, when performing step Y1, the mass ratio of zirconium salt to organic ligand is 1:(6-8). In fact, the mass ratio of zirconium salt to organic ligand is precisely controlled so that the content of organic ligand is relatively sufficient and can be fully coordinated with zirconium salt. The formed metal frame material has a stable and uniform pore structure, which is conducive to the adsorption and storage of gas molecules, and can also optimize the cleanliness of the metal frame material and improve its structural stability.

[0037] In some embodiments, when performing step Y1, the zirconium salt includes at least one of zirconium tetrachloride, zirconium nitrate, zirconium oxychloride, zirconium carbonate and zirconium hydroxide, and the organic ligand includes at least one of 2-methylimidazole, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 2,2'-bipyridine and terephthalic acid. In fact, zirconium tetrachloride has high reactivity and can quickly react with organic ligands to shorten the reaction time. After zirconium tetrachloride reacts with 2-methylimidazole, the metal frame material formed has high crystallinity, regular structure, high porosity and specific surface area, and can selectively adsorb impurity gases in carbon dioxide.

[0038] In some embodiments, when performing step Y1, the solvent in the ligand mixture includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, diformate, and ethylene glycol methyl ether.

[0039] In some embodiments, when performing step Y2, dopamine is dissolved in deionized water to prepare a dopamine solution, and the pH of the dopamine solution is adjusted to 8-9 using an alkaline regulator, and then ultrasonically reacted at 50-60° C. for 10-14 hours to obtain a polydopamine solution.

[0040] In some embodiments, when executing step Y2, the alkaline metal salt includes at least one of potassium carbonate, sodium bicarbonate, sodium phosphate, potassium hydroxide, and sodium hydroxide, and the mass ratio of the carbide to the alkaline metal salt is 1: (0.3-0.5). After the alkaline metal salt is dissolved to form an alkaline salt solution, the carbide is put into the alkaline salt solution and boiled to evaporate the solvent to obtain a mixed load, and the mixed load is calcined at 700-800°C for 2-4h.

[0041] In some embodiments, when performing step Y3, when the first carrier and the second carrier are dispersed in ethanol, the mass ratio of the first carrier to the second carrier is 1:(0.8-1.2), the adhesive includes at least one of sodium silicate, zinc phosphate, and dihydrogen aluminum phosphate, and the mass ratio of the first carrier, the second carrier and the adhesive is 1:(0.8-1.2):(0.1-0.3).

[0042] In some embodiments, when performing step Y4, the modified carrier is immersed in a metal salt solution with a solid-liquid ratio of 0.04-0.06 g / mL, ultrasonically dispersed at 60-80°C for 20-25 hours, separated, washed and dried, and then reduced in a hydrogen atmosphere at 300-350°C to obtain a dehydrogenation unit.

[0043] In some embodiments, the flue gas used in step Y1 includes at least one of boiler combustion flue gas, coal-fired heating flue gas, and power plant coal-fired flue gas. In fact, the flue gas contains 20-40 vol. % CO2, 60-90 vol. % N2, a small amount of sulfur-containing gas, a small amount of water vapor and hydrocarbon substances.

[0044] In some embodiments, when executing step S1, the raw gas is pressurized and then passed into a fine desulfurization tower, and desulfurized gas is obtained after physical adsorption desulfurization treatment by a desulfurizer; the desulfurizer includes at least one of activated carbon, zeolite molecular sieve, and activated alumina. Specifically, the concentration of carbon dioxide in the obtained food-grade carbon dioxide is ≥99.999%.

[0045] In some embodiments, the desulfurized gas is passed into a dehydrogenation unit at 450-500° C. in a dehydrogenation purification tower to produce purified gas.

[0046] In some embodiments, when executing step S3, the purified gas is input into a dehumidifier (i.e., an ammonia precooler) for precooling and water separation, and a certain amount of carbonated condensed water is produced and discharged into the sewage pool of the device through an underground sewage pipe, and then enters a dryer (i.e., a molecular sieve) for drying. Two dryers are opened and one is reserved, and the operation is switched in turn. When one of the dryers is adsorbing, the other is regenerated, and the cycle is repeated. The dried purified gas enters the condenser, and the compressed gas is condensed into liquid carbon dioxide after heat exchange with liquid ammonia. After the carbon dioxide is condensed, it enters the purification tower for distillation and purification. The non-condensable gases after dehydrogenation in the raw gas, such as oxygen and nitrogen, evaporate upward through the purification tower and are vented through the pressure control valve at the top of the tower.

[0047] Preparation Example 1

[0048] This embodiment preparation example 1 provides a preparation method of a dehydrogenation unit, comprising the following steps:

[0049] Y1. Zirconium tetrachloride (CAS: 10026-11-6) and 1,3,5-benzenetricarboxylic acid (CAS: 554-95-0) were added into dimethyl sulfoxide at a mass ratio of 1:7, and the mixture was stirred and dissolved to obtain a ligand mixture. The ligand mixture was subjected to a hydrothermal reaction at 120° C. for 24 h, and then filtered and separated, and washed alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 90° C. to a constant weight to obtain a first carrier.

[0050] Y2. Dopamine was dissolved in deionized water, and the pH of the dopamine aqueous solution was adjusted to 8.5 with potassium hydroxide, and then the polymerization reaction was stirred at 55° C. for 12 hours to obtain a polydopamine solution, and the polydopamine solution was centrifuged at a speed of 500 rpm to separate the centrifugal precipitate, and then the carbide was calcined at 850° C. for 2 hours after rinsing with deionized water and anhydrous ethanol, and then the carbide was mixed with a potassium hydroxide aqueous solution (the mass ratio of carbide to potassium hydroxide was 1:4), and the solvent was evaporated and then the mixture was calcined at 700° C. for 2 hours, and then cooled to room temperature to obtain a second carrier;

[0051] Y3. The first carrier and the second carrier were mixed and dispersed in anhydrous ethanol in a mass ratio of 1:1, and a sodium silicate aqueous solution was added (the mass ratio of the first carrier, the second carrier and sodium silicate was 1:1:0.2), and then ultrasonically treated at 20 kHz for 30 minutes, and the solvent was evaporated and transferred to a vacuum drying oven at 80°C and dried to constant weight to obtain a modified carrier;

[0052] Y4. The modified carrier was immersed in a saturated aqueous solution of copper nitrate at a solid-liquid ratio of 0.05 g / mL, and ultrasonically dispersed at 70°C for 24 hours. The precipitate was centrifuged at 500 rpm. The precipitate was washed with deionized water and transferred to a hydrogen atmosphere furnace at 350°C for reduction for 2 hours to obtain a dehydrogenation unit.

[0053] Preparation Example 2

[0054] This embodiment preparation example 2 provides a preparation method for a dehydrogenation unit, which is different from the embodiment preparation example 1 in that in step Y1, zirconium tetrachloride (CAS: 10026-11-6) and 1,3,5-benzenetricarboxylic acid (CAS: 554-95-0) are in a mass ratio of 1:6.

[0055] Preparation Example 3

[0056] This embodiment preparation example 3 provides a preparation method for a dehydrogenation unit, which is different from the embodiment preparation example 1 in that in step Y1, zirconium tetrachloride (CAS: 10026-11-6) and 1,3,5-benzenetricarboxylic acid (CAS: 554-95-0) are in a mass ratio of 1:8.

[0057] Preparation Example 4

[0058] This embodiment preparation example 4 provides a preparation method for a dehydrogenation unit, which is different from the embodiment preparation example 1 in that in step Y4, the modified support is immersed in a saturated aqueous solution of cobalt nitrate at a solid-liquid ratio of 0.05 g / mL.

[0059] Preparation Example 5

[0060] This embodiment preparation example 5 provides a preparation method for a dehydrogenation unit, which is different from the embodiment preparation example 1 in that in step Y4, the modified support is immersed in a saturated aqueous solution of nickel nitrate at a solid-liquid ratio of 0.05 g / mL.

[0061] Comparative Preparation Example 1

[0062] This comparative preparation example 1 provides a preparation method for a dehydrogenation unit, which is different from the implementation preparation example 1 in that steps Y2 and Y3 are not performed, and the first carrier prepared in step Y1 is used as a modified carrier to directly perform step Y4.

[0063] Comparative Preparation Example 2

[0064] This comparative preparation example 2 provides a preparation method for a dehydrogenation unit, which is different from the implementation preparation example 1 in that steps Y1 and Y3 are not performed, and the second carrier prepared in step Y2 is used as a modified carrier to directly perform step Y4.

[0065] Comparative Preparation Example 3

[0066] This comparative preparation example 3 provides a preparation method for a dehydrogenation unit, which is different from the implementation preparation example 1 in that step Y4 is not performed, and the modified carrier prepared in step Y3 is the dehydrogenation unit.

[0067] Comparative Preparation Example 4

[0068] This comparative preparation example 4 provides a preparation method for a dehydrogenation unit, which is different from the implementation preparation example 1 in that no sodium silicate aqueous solution is added in step Y3.

[0069] Comparative Preparation Example 5

[0070] This comparative preparation example 5 provides a preparation method for a dehydrogenation unit, which is different from the implementation preparation example 1 in that step Y3 is not performed. In step Y4, the first carrier and the second carrier are respectively immersed in a saturated aqueous solution of copper nitrate at a solid-liquid ratio of 0.05 g / mL, and after ultrasonic dispersion at 70°C for 24 hours, the precipitate is centrifuged at a speed of 500 rpm. After washing the precipitate with deionized water, it is transferred to a 350°C hydrogen atmosphere furnace for reduction for 2 hours to obtain a first modified unit and a second modified unit, respectively. The first modified unit and the second modified unit are mixed to obtain a dehydrogenation unit.

[0071] Performance Testing

[0072] The dehydrocarbon units prepared in Preparation Examples 1 to 5 and Comparative Preparation Examples 1 to 5 were used to purify carbon dioxide in coal-fired flue gas according to the following steps:

[0073] S1. The raw gas is obtained by dust removal and filtration at 150°C, and the raw gas is passed into a carbon dioxide compressor to be pressurized to 25 bar, and then passed into a fine desulfurization tower for physical adsorption and desulfurization by activated carbon to obtain desulfurized gas;

[0074] S2, heating the desulfurized gas to 475°C, passing it into a dehydrogenation purification tower, and performing dehydrogenation treatment through a dehydrogenation unit, and then cooling it to 300°C to obtain purified gas;

[0075] S3. Cool the purified gas in a dehumidifier to separate the condensed water, dry the purified gas in a dryer, pass it into a condenser to cool it into liquid carbon dioxide, and then purify it through distillation in a purification tower to obtain food-grade carbon dioxide.

[0076] The volume content of carbon dioxide in the coal-fired flue gas and the volume content of carbon dioxide in the purified gas after passing through the dehydrogenation unit were detected, and the volume change of carbon dioxide after the gas was treated by the dehydrogenation unit was calculated, and the results are shown in Table 1 below; and the dehydrogenation units prepared in Preparation Examples 1 to 5 and Comparative Preparation Examples 1 to 5 were repeatedly purified, and the effective working time of the dehydrogenation unit was recorded (with the change in the volume of carbon dioxide after the dehydrogenation unit was treated less than 70% as the limit), and the results are shown in Table 2 below.

[0077] Table 1 Carbon dioxide volume before and after dehydrogenation unit treatment

[0078]

[0079] Table 2 Effective working time of dehydrogenation unit

[0080]

[0081]

[0082] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A method for purifying food-grade carbon dioxide, characterized in that: The following steps are involved: The raw gas is pressurized and then subjected to physical adsorption desulfurization to obtain desulfurized gas; the desulfurized gas is passed through a dehydrogenation unit in a dehydrogenation purification tower to obtain purified gas; The purified gas is cooled and dried, then condensed and liquefied, and then distilled and purified to obtain food-grade carbon dioxide; wherein the preparation method of the dehydrocarbon unit comprises: stirring and dissolving zirconium salt and organic ligand to obtain a ligand mixture, subjecting the ligand mixture to a hydrothermal reaction at 110-120°C for 20-25h, separating, and drying at 80-90°C to obtain a first carrier; polymerizing dopamine in an alkaline environment to obtain polydopamine, calcining at 800-900°C to obtain carbide, mixing the carbide with at least one of potassium carbonate, sodium bicarbonate, sodium phosphate, potassium hydroxide, and sodium hydroxide, roasting, and cooling to obtain a second carrier; dispersing the first carrier and the second carrier in ethanol, adding a binder, ultrasonically dispersing, and evaporating the solvent to obtain a modified carrier; immersing the modified carrier in a metal salt solution, separating and drying to obtain a dehydrocarbon unit.

2. The purification method according to claim 1, characterized in that When the raw gas is pressurized, the raw gas is passed into the compressor and pressurized to 23-27 bar in multiple stages.

3. The purification method according to claim 1, characterized in that The raw gas is pressurized and then passed into a fine desulfurization tower, and desulfurized gas is obtained after physical adsorption desulfurization treatment by a desulfurizer; the desulfurizer includes at least one of activated carbon, zeolite molecular sieve, and activated alumina.

4. The purification method according to claim 1, characterized in that The desulfurized gas is passed into the dehydrogenation unit at 450-500° C. in the dehydrogenation purification tower to obtain purified gas.

5. The purification method according to claim 1, characterized in that: In the process of stirring and dissolving the zirconium salt and the organic ligand to obtain a ligand mixture solution: the mass ratio of the zirconium salt to the organic ligand is 1:(6-8); and / or the zirconium salt includes at least one of zirconium tetrachloride, zirconium nitrate, zirconium oxychloride, zirconium carbonate and zirconium hydroxide; and / or the organic ligand includes at least one of 2-methylimidazole, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 2,2'-bipyridine and terephthalic acid; and / or the solvent in the ligand mixture solution includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, diformic acid ester, and ethylene glycol methyl ether.

6. The purification method according to claim 1, characterized in that: The process of preparing polydopamine by polymerizing dopamine in an alkaline environment includes: dissolving dopamine in deionized water to prepare a dopamine solution, adjusting the pH of the dopamine solution to 8-9 with an alkaline regulator, and then ultrasonically reacting at 50-60° C. for 10-14 hours to prepare the polydopamine solution.

7. The purification method according to claim 1, characterized in that: During the mixed roasting process, the mass ratio of carbide to at least one of potassium carbonate, sodium bicarbonate, sodium phosphate, potassium hydroxide and sodium hydroxide is 1:(0.3-0.5).

8. The purification method according to claim 1, characterized in that: When the first carrier and the second carrier are dispersed in ethanol, the mass ratio of the first carrier to the second carrier is 1:(0.8-1.2); and / or the adhesive includes at least one of sodium silicate, zinc phosphate, and aluminum dihydrogen phosphate; and / or the mass ratio of the first carrier, the second carrier and the adhesive is 1:(0.8-1.2):(0.1-0.3).

9. The purification method according to claim 1, characterized in that: When the modified carrier is immersed in a metal salt solution and separated and dried to obtain a dehydrogenation unit, the method comprises: immersing the modified carrier in a metal salt solution with a solid-liquid ratio of 0.04-0.06 g / mL, ultrasonically dispersing the modified carrier at 60-80° C. for 20-25 hours, separating the carrier, washing and drying the carrier, and reducing the carrier in a hydrogen atmosphere at 300-350° C. to obtain a dehydrogenation unit.

10. The purification method according to claim 1, characterized in that: The concentration of carbon dioxide in the food-grade carbon dioxide is ≥99.999%.

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