CN114797449B - Based on theta-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 Method for recycling HF byproducts - Google Patents
Based on theta-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 Method for recycling HF byproducts Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 52
- 239000003054 catalyst Substances 0.000 title claims abstract description 45
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 36
- 229910018072 Al 2 O 3 Inorganic materials 0.000 title claims abstract description 29
- 238000003421 catalytic decomposition reaction Methods 0.000 title claims abstract description 26
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 23
- 239000003546 flue gas Substances 0.000 title claims abstract description 23
- 238000004064 recycling Methods 0.000 title claims abstract description 22
- 239000006227 byproduct Substances 0.000 title claims abstract description 19
- 239000007789 gas Substances 0.000 claims abstract description 37
- 239000002135 nanosheet Substances 0.000 claims abstract description 31
- 239000007788 liquid Substances 0.000 claims abstract description 22
- 229910004261 CaF 2 Inorganic materials 0.000 claims abstract description 17
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 17
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 12
- 239000011737 fluorine Substances 0.000 claims abstract description 12
- 239000002699 waste material Substances 0.000 claims abstract description 12
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000009388 chemical precipitation Methods 0.000 claims abstract description 10
- 230000035484 reaction time Effects 0.000 claims abstract description 7
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 6
- 238000002360 preparation method Methods 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 44
- 238000006243 chemical reaction Methods 0.000 claims description 32
- 239000000243 solution Substances 0.000 claims description 32
- 239000008367 deionised water Substances 0.000 claims description 25
- 229910021641 deionized water Inorganic materials 0.000 claims description 25
- 238000003756 stirring Methods 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 17
- 239000011734 sodium Substances 0.000 claims description 17
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 11
- 239000002244 precipitate Substances 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 10
- 239000002243 precursor Substances 0.000 claims description 9
- 230000000630 rising effect Effects 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 8
- 238000009834 vaporization Methods 0.000 claims description 8
- 230000008016 vaporization Effects 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 7
- 239000002064 nanoplatelet Substances 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 claims description 6
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 6
- 238000003837 high-temperature calcination Methods 0.000 claims description 6
- 239000013049 sediment Substances 0.000 claims description 6
- 239000000741 silica gel Substances 0.000 claims description 6
- 229910002027 silica gel Inorganic materials 0.000 claims description 6
- -1 fluoride ions Chemical class 0.000 claims description 5
- 150000002500 ions Chemical class 0.000 claims description 5
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 4
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 4
- 238000005119 centrifugation Methods 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 4
- 235000011152 sodium sulphate Nutrition 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 3
- 239000012295 chemical reaction liquid Substances 0.000 claims description 3
- 239000002274 desiccant Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 229910001415 sodium ion Inorganic materials 0.000 claims description 2
- 238000010998 test method Methods 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract description 8
- 238000011084 recovery Methods 0.000 abstract description 7
- 239000002994 raw material Substances 0.000 abstract description 5
- 238000006555 catalytic reaction Methods 0.000 abstract description 2
- 230000007062 hydrolysis Effects 0.000 description 6
- 238000006460 hydrolysis reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000010792 warming Methods 0.000 description 2
- 239000002841 Lewis acid Substances 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
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- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- 238000013461 design Methods 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8659—Removing halogens or halogen compounds
- B01D53/8662—Organic halogen compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
- B01J21/04—Alumina
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/20—Halides
- C01F11/22—Fluorides
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- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/48—Halides, with or without other cations besides aluminium
- C01F7/50—Fluorides
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- B01D2258/0283—Flue gases
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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Abstract
The invention belongs to the field of resources and environment, and in particular relates to a method based on theta-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF by-products. Firstly preparing theta-Al by a hydrothermal method 2 O 3 Nanosheets for realizing theta-Al on a fixed bed 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 Collecting the obtained HF waste liquid, and obtaining Na by a chemical precipitation method 3 AlF 6 And CaF 2 . The invention is based on high-efficiency catalysis CF 4 theta-Al of (2) 2 O 3 The catalyst has excellent catalytic performance and stability. In the preparation process, the reaction time is short, the method is simple and easy to implement, and the Na obtained by recycling the HF waste liquid is recycled 3 AlF 6 And CaF 2 The method is a raw material in the electrolytic aluminum industry, and realizes the fluorine circulation of fluorine-containing gas in the electrolytic aluminum flue gas. Catalytic decomposition of CF 4 The efficiency of the catalyst can reach 100 percent, the single service life can reach 350 hours, and the Na 3 AlF 6 The recovery rate can reach 92.2%, caF 2 The recovery rate can reach 7.6 percent, and the whole F ‑ The recovery rate can reach 99.9 percent.
Description
Technical Field
The invention belongs to the field of resources and environment, and in particular relates to a method based on theta-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF by-products.
Background
The yield of electrolytic aluminum in China is steadily increased year by year, the yield of electrolytic aluminum in 2021 year is up to 3850 ten thousand tons, and 2Kg CF is generated about every ton of electrolytic aluminum due to anode effect in the electrolytic aluminum production process 4 Based on 2021, the yield of electrolytic aluminum in China is calculated, and 3850 ten thousand tons of aluminum at least produce 7.6 ten thousand tons of CF 4 Its global warming potential (Global Warming Potential, GWP) is carbon dioxide (CO 2 ) Is 7390 times the emission equivalent of 4.9 hundred million tons of CO 2 Whereas in the electrolytic aluminium industry CO 2 Is only 0.38 hundred million tons and CF 4 Is very stable and requires 50,000 years for natural decomposition in the atmosphere. Thus, for CF treatment of electrolytic aluminum industry emissions 4 Gases are particularly important.
On the other hand, the C-F bond is strong and its bond energy is 543kJ mol -1 Destruction of CF 4 The structure of the molecule requires more severe conditions. The method has the advantages of simple operation, large treatment flux, lower treatment temperature, no generation of harmful end products, and the catalytic hydrolysis method is the most effective and proper means for treating the CF at present 4 Molecules, theta-Al 2 O 3 The nano-sheet catalyst has larger specific surface area and rich Lewis acid sites, and is used for catalyzing and hydrolyzing CF 4 Is a catalyst of the ideal type. The end product obtained by decomposing CF4 by a catalytic hydrolysis method is CO 2 And HF, wherein the HF is absorbed by a water bottle, and the collected HF waste liquid can obtain Na by a chemical precipitation method 3 AlF 6 And CaF 2 Can be used as a raw material in the electrolytic aluminum industry. At present, the method based on theta-Al is not available 2 O 3 High-efficiency catalytic decomposition of catalyst in electrolytic aluminum flue gasCF 4 And related patent reports of HF byproduct recycling thereof.
Disclosure of Invention
The invention aims to provide a composition based on theta-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, which is based on high-efficiency catalysis of CF 4 theta-Al of (2) 2 O 3 The catalyst has excellent catalytic performance and stability. In the preparation process, the reaction time is short, the method is simple and easy to implement, and the Na obtained by recycling the HF waste liquid is recycled 3 AlF 6 And CaF 2 The method is a raw material in the electrolytic aluminum industry, and realizes the fluorine circulation of fluorine-containing gas in the electrolytic aluminum flue gas.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And HF byproduct recycling method, firstly preparing theta-Al by a hydrothermal method 2 O 3 Nanosheets for realizing theta-Al on a fixed bed 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 Collecting the obtained HF waste liquid, and obtaining Na by a chemical precipitation method 3 AlF 6 And CaF 2 。
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts to prepare theta-Al 2 O 3 The specific steps of the nano sheet are as follows:
(1) Adding aluminum isopropoxide into an isopropanol solution, and fully stirring to obtain a mixed reaction solution;
(2) Adding deionized water into the obtained mixed reaction liquid, fully stirring, transferring to a reaction kettle, reacting for 0.5-2 h at 100-120 ℃, cooling, washing, centrifuging and drying to obtain white precursor powder;
(3) Transferring the obtained white precursor powder into a crucible, calcining at high temperature, and cooling to obtain theta-Al 2 O 3 Nanoplatelets, i.e. the efficient catalytic decomposition of CF 4 theta-Al of (2) 2 O 3 A nanosheet catalyst material.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, wherein in the step (1), the adding amount of aluminum isopropoxide is 10.000g, the adding amount of isopropanol is 100ml, the stirring speed is 500 revolutions per minute, and the stirring time is 12 hours; in the step (2), the adding amount of deionized water is 10ml, the stirring time is 10min, the capacity of the reaction kettle is 150ml, the reaction temperature is 110 ℃, and the reaction time is 1h.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, wherein in the step (3), the high-temperature calcination temperature is 850-950 ℃, the reaction time is 3-5 h, and the temperature is raised in the process of: the temperature rising rate from room temperature to 600 ℃ is 4-6 ℃/min, and the temperature rising rate from 600 ℃ to 850-950 ℃ is 0.5-2 ℃/min.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, and theta-Al on a fixed bed 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 The specific process is as follows:
(1) Will be theta-Al 2 O 3 The nano-sheet catalyst is filled into a reaction bin of a fixed bed, and CF is pre-introduced by an air supply system 4 Mixing with Ar gas;
(2) Heating a reaction bin of the fixed bed to a test temperature, heating the vaporization chamber, and introducing water vapor into the reaction bin;
(3) The tail gas obtained in the process passes through a deionized water bottle, is dried by a drying pipe, and enters a gas chromatograph to detect the components and the content of the gas.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, wherein in the step (1), the fixed bed consists of a gas supply system, a vaporization chamber, a reaction bin, a deionized water bottle, a drying pipe and a gas chromatograph.
The basis is thatθ-Al 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF by-product, in the step (1), theta-Al 2 O 3 The filling amount of the nano-sheet catalyst is 1.000g, and the inner diameter of the reaction bin is 19mm; CF in volume percent 4 The mixed gas with Ar gas comprises the following components: 0.5% CF 4 99.5% Ar gas, the flow rate of the mixed gas is 33.3ml/min; in the step (2), the temperature of the reaction bin is 650-750 ℃, and the temperature rising rate is 10 ℃/min; the heating temperature of the vaporization chamber is 200 ℃, and the water inlet rate is 0.007ml/min; in the step (3), the capacity of the deionized water bottle is 500ml, and the added deionized water amount is 300ml; the drying tube is barrel-shaped, the added drying agent is allochroic silica gel, and the adding amount of allochroic silica gel is 500g.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And HF byproduct recycling method, CF 4 The volume ratio of the water vapor to the water vapor is 1:50.
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, and obtaining Na by a chemical precipitation method 3 AlF 6 And CaF 2 The specific process is as follows:
(1) To absorb CF 4 Adding ammonia water into the HF deionized water solution generated after decomposition, regulating the pH value of the solution to pH=8, adding sodium sulfate and aluminum sulfate, fully stirring, preserving the temperature of the mixed solution in a water bath kettle, centrifugally separating precipitate and clear liquid, and drying the precipitate to obtain Na 3 AlF 6 ；
(2) Adding CaCl into the clear liquid 2 The pH value of the solution is adjusted to pH=10, after the solution is fully stirred, the sediment and the clear solution are separated by centrifugation, and the sediment is dried to obtain CaF 2 。
Said theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, wherein in the step (1), the fluorine content of the HF deionized water solution is 23g/L, the mass concentration of ammonia water is 25-28%, and Na ions/Al ions are removedThe molar ratio of the sub ions to the F ions is 4:1:6, and the heat preservation temperature of the water bath kettle is 80 ℃; in the step (2), caCl 2 The addition amount is 2.4 times of the molar amount of the fluoride ions in the clear liquid.
The design idea of the invention is as follows: based on the catalytic hydrolysis method, the theta-Al is realized on a fixed bed 2 O 3 High-efficiency decomposition of CF in electrolytic aluminum flue gas on catalyst 4 ，CF 4 Decomposition into CO 2 And HF gas, the HF gas is absorbed by a water bottle to obtain HF waste liquid, fluoride ions in the HF waste liquid are precipitated by a simple chemical precipitation method, and the obtained Na is recovered 3 AlF 6 And CaF 2 Is a raw material in the electrolytic aluminum industry to realize the fluorine circulation of fluorine-containing gas in the electrolytic aluminum flue gas.
The invention has the remarkable advantages and beneficial effects that:
the invention adopts hydrothermal and high-temperature calcination treatment to obtain theta-Al 2 O 3 The nano-sheet catalyst has the advantages of cheap and easily obtained raw materials, short reaction time, low cost, simplicity, practicability, good reproducibility and excellent performance. theta-Al 2 O 3 Catalytic decomposition of CF by nanosheet catalyst 4 The efficiency of the catalyst can reach 100 percent, the single service life can reach 350 hours, and the Na 3 AlF 6 The recovery rate can reach 92.2%, caF 2 The recovery rate can reach 7.6 percent, and the overall fluoride ion (F) - ) The recovery rate can reach 99.9 percent.
Drawings
FIG. 1 is θ -Al 2 O 3 X-ray diffraction pattern of nanoplatelets. In the figure, the abscissa 2θ represents the diffraction angle (degree), and the ordinate Intensity represents the Intensity (a.u.).
FIG. 2 is θ -Al 2 O 3 Scanning electron microscope image of the nanoplatelets.
FIG. 3 is θ -Al 2 O 3 Catalytic hydrolysis of nanoplatelets CF 4 Is a performance graph of (a). Wherein the abscissa Time represents Time (hours), and the ordinate CF 4 convertion represents CF 4 Decomposition rate (%).
FIG. 4 is a view showing Na obtained by recycling HF waste liquid 3 AlF 6 (a) And CaF 2 (b) Is an X-ray diffraction pattern of (2). In the figure, the abscissa 2θ represents the diffraction angle (diffraction),the ordinate Intensity represents Intensity (a.u.).
Detailed Description
In the specific implementation process, the invention prepares the theta-Al by a hydrothermal method 2 O 3 Nanosheets for realizing theta-Al on a fixed bed 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 Collecting the obtained HF waste liquid, and obtaining Na by a chemical precipitation method 3 AlF 6 And CaF 2 . The main functions and effects of the hydrothermal reaction are as follows: under the conditions of high temperature and high pressure, the reaction is carried out under the condition of approaching to homogeneous phase, and the nano sheet material with good dispersivity, high purity and controllable morphology is obtained. The main functions and effects of the high-temperature calcination treatment are as follows: and further oxidizing the precursor obtained by the hydrothermal reaction to obtain the oxide nano sheet material. The chemical precipitation method has the main functions and effects that: fluoride ion (F) in HF-absorbing deionized water - ) Sedimentation to Na 3 AlF 6 And CaF 2 Realizing the fluorine circulation of fluorine-containing gas in the electrolytic aluminum flue gas.
The present invention is further illustrated by the following examples, but the scope of the present invention is not limited to the following examples.
EXAMPLE 1 efficient catalytic decomposition of CF 4 θ-Al 2 O 3 Preparation of nanosheet catalyst
(1) Adding aluminum isopropoxide into an isopropanol solution, and fully stirring to obtain a mixed reaction solution;
(2) Adding deionized water into the obtained mixed reaction liquid, fully stirring, transferring to a reaction kettle for reaction, cooling, washing, centrifuging and drying to obtain white precursor powder;
(3) Transferring the obtained white precursor powder into a crucible, calcining at high temperature, and cooling to obtain theta-Al 2 O 3 Nanoplatelets, i.e. the efficient catalytic decomposition of CF 4 theta-Al of (2) 2 O 3 A nanosheet catalyst material.
In this example, 10.000g of aluminum isopropoxide was added to 100ml of the isopropanol solution, and the stirring speed was 500 rpm, and the mixture was sufficiently stirred for 12 hours to obtain a mixed reaction solution; adding to the mixed reaction solutionAdding 10ml of deionized water, fully stirring for 10min, transferring to a reaction kettle with 150ml of specification, reacting for 1h at 110 ℃, cooling, washing, centrifuging, and drying to obtain white precursor powder; transferring the obtained white precursor powder into a crucible, and reacting for 4 hours at 900 ℃ through high-temperature calcination to obtain theta-Al 2 O 3 Nanoplatelets, i.e. the efficient catalytic decomposition of CF 4 theta-Al of (2) 2 O 3 A nanosheet catalyst material.
During the temperature rising process of high-temperature calcination: the temperature rising rate from room temperature to 600 ℃ is 5 ℃/min, the temperature rising rate from 600 ℃ to 900 ℃ is 1 ℃/min, and the effect is that: control of Al 2 O 3 The crystal phase transformation rate to obtain pure theta phase Al 2 O 3 。
As can be seen from FIGS. 1 and 2, the material prepared in this example is identified as θ -Al 2 O 3 The specification and the dimensions of the nano-sheet are as follows: theta-Al 2 O 3 The diameter of the nano-sheet is 50nm, and the thickness is 20nm.
EXAMPLE 2CF 4 Catalytic hydrolysis Performance test
(1) Will be theta-Al 2 O 3 1.000g of nano-sheet catalyst is filled into a reaction bin of a fixed bed, the inner diameter of the reaction bin is 19mm, and CF is pre-introduced by a gas supply system 4 Mixing with Ar gas;
(2) Heating a reaction bin of the fixed bed to a test temperature, heating the vaporization chamber, and introducing water vapor into the reaction bin;
(3) The tail gas obtained in the process passes through a deionized water bottle, is dried by a drying pipe, and enters a gas chromatograph to detect the components and the content of the gas. The capacity of the deionized water bottle is 500ml, and the added deionized water amount is 300ml; the drying tube is barrel-shaped, the added drying agent is allochroic silica gel, and the adding amount of allochroic silica gel is 500g.
In this example, the θ -Al obtained in example 1 was used 2 O 3 Nanosheets CF 4 And (3) testing catalytic hydrolysis performance, wherein the testing conditions are as follows: the reaction temperature is 750 ℃, and the heating rate is 10 ℃/min; CF (compact flash) 4 In the mixed gas with Ar gas, CF 4 Is 0.5% by volume, whichAr gas is the rest, and the flow rate of the mixed gas is 33.3ml/min; the heating temperature of the vaporization chamber is 200 ℃, the water inlet rate is 0.007ml/min, and the water vapor inlet amount is CF 4 /H 2 The volume ratio of O (gas) is 1:50. The test results are shown in FIG. 3, front 100h, CF 4 The decomposition efficiency was maintained at 100%, and the decomposition efficiency was slowly decreased to about 50% when the test time exceeded 100 hours, and reached 350 hours.
EXAMPLE 3 recovery of fluoride ions (F) from HF waste liquid by chemical precipitation - )
(1) To absorb CF 4 Adding ammonia water into the HF deionized water solution generated after decomposition, regulating the pH value of the solution to pH=8, adding sodium sulfate and aluminum sulfate, fully stirring, preserving the temperature of the mixed solution in a water bath kettle, centrifugally separating precipitate and clear liquid, and drying the precipitate to obtain Na 3 AlF 6 ；
(2) Adding CaCl into the clear liquid 2 The pH value of the solution is adjusted to pH=10, after the solution is fully stirred, the sediment and the clear solution are separated by centrifugation, and the sediment is dried to obtain CaF 2 。
In this example, CF was absorbed into example 2 4 Adding ammonia water with the mass concentration of 26% into HF deionized water solution (fluorine content of HF deionized water solution is 23 g/L) generated after decomposition, adjusting the pH value of the solution to pH=8, and adding sodium sulfate and aluminum sulfate to enable Na in the solution to be reduced + /Al 3+ /F - The molar ratio of (2) is 4:1:6, after fully stirring, the mixed solution is kept in a water bath kettle at 80 ℃, the precipitate and the clear liquid are separated by centrifugation, and Na is obtained by drying the precipitate 3 AlF 6 The method comprises the steps of carrying out a first treatment on the surface of the Adding CaCl into the clear liquid 2 ，CaCl 2 Adding 2.4 times of the molar amount of fluorine ions in the clear solution, adjusting the pH value of the solution to pH=10, fully stirring, centrifuging to separate precipitate and clear solution, and drying the precipitate to obtain CaF 2 。
As can be seen from FIGS. 4 (a) and (b), F in the HF waste liquid - By Na 3 AlF 6 And CaF 2 Is recycled.
The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (3)
1. theta-Al-based 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF byproducts, which is characterized in that theta-Al is prepared by a hydrothermal method 2 O 3 Nanosheets for realizing theta-Al on a fixed bed 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 Collecting the obtained HF waste liquid, and obtaining Na by a chemical precipitation method 3 AlF 6 And CaF 2 ；
Preparation of theta-Al 2 O 3 The specific steps of the nano sheet are as follows:
(1) Adding aluminum isopropoxide into an isopropanol solution, and fully stirring to obtain a mixed reaction solution; in the step (1), the adding amount of aluminum isopropoxide is 10.000g, the adding amount of isopropanol is 100ml, the stirring speed is 500 revolutions per minute, and the stirring time is 12 hours;
(2) Adding deionized water into the obtained mixed reaction liquid, fully stirring, transferring to a reaction kettle, reacting for 0.5-2 h at 100-120 ℃, cooling, washing, centrifuging and drying to obtain white precursor powder; in the step (2), the adding amount of deionized water is 10ml, the stirring time is 10min, the capacity of the reaction kettle is 150ml, the reaction temperature is 110 ℃, and the reaction time is 1h;
(3) Transferring the obtained white precursor powder into a crucible, calcining at high temperature, and cooling to obtain theta-Al 2 O 3 Nanoplatelets, i.e. the efficient catalytic decomposition of CF 4 theta-Al of (2) 2 O 3 A nanosheet catalyst material; in the step (3), the high-temperature calcination temperature is 850-950 ℃, the reaction time is 3-5 h, and in the heating process: the temperature rising rate from room temperature to 600 ℃ is 4-6 ℃/min, and the temperature rising rate from 600 ℃ to 850-950 ℃ is 0.5-2 ℃/min;
fixed bed theta-Al 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 The specific process is as follows:
(1) Will be theta-Al 2 O 3 Reaction of nanosheet catalyst packed into fixed bedIn the bin, CF is pre-introduced by an air supply system 4 Mixing with Ar gas; in step (1), θ -Al 2 O 3 The filling amount of the nano-sheet catalyst is 1.000g, and the inner diameter of the reaction bin is 19mm; CF in volume percent 4 The mixed gas with Ar gas comprises the following components: 0.5% CF 4 99.5% Ar gas, the flow rate of the mixed gas is 33.3ml/min;
(2) Heating a reaction bin of the fixed bed to a test temperature, heating the vaporization chamber, and introducing water vapor into the reaction bin; in the step (2), the temperature of the reaction bin is 650-750 ℃, and the temperature rising rate is 10 ℃/min; the heating temperature of the vaporization chamber is 200 ℃, and the water inlet rate is 0.007ml/min;
(3) The tail gas obtained in the process passes through a deionized water bottle, is dried by a drying pipe, and enters a gas chromatograph to detect the components and the content of the gas; in the step (3), the capacity of the deionized water bottle is 500ml, and the added deionized water amount is 300ml; the drying tube is in a barrel shape, the added drying agent is allochroic silica gel, and the adding amount of the allochroic silica gel is 500g;
chemical precipitation method to obtain Na 3 AlF 6 And CaF 2 The specific process is as follows:
(1) To absorb CF 4 Adding ammonia water into the HF deionized water solution generated after decomposition, regulating the pH value of the solution to pH=8, adding sodium sulfate and aluminum sulfate, fully stirring, preserving the temperature of the mixed solution in a water bath kettle, centrifugally separating precipitate and clear liquid, and drying the precipitate to obtain Na 3 AlF 6 The method comprises the steps of carrying out a first treatment on the surface of the In the step (1), the fluorine content of the HF deionized water solution is 23g/L, the mass concentration of ammonia water is 25% -28%, the molar ratio of Na ions to Al ions to F ions is 4:1:6, and the heat preservation temperature of the water bath kettle is 80 ℃;
(2) Adding CaCl into the clear liquid 2 The pH value of the solution is adjusted to pH=10, after the solution is fully stirred, the sediment and the clear solution are separated by centrifugation, and the sediment is dried to obtain CaF 2 The method comprises the steps of carrying out a first treatment on the surface of the In the step (2), caCl 2 The addition amount is 2.4 times of the molar amount of the fluoride ions in the clear liquid.
2.θ -Al-based according to claim 1 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF by-products, characterized in that the method comprises the following steps of 2 O 3 Efficient decomposition of CF by nanosheet catalyst 4 In the step (1) of the test method, the fixed bed consists of a gas supply system, a vaporization chamber, a reaction bin, a deionized water bottle, a drying pipe and a gas chromatograph.
3.θ -Al-based according to claim 1 2 O 3 High-efficiency catalytic decomposition of CF in electrolytic aluminum flue gas by catalyst 4 And a method for recycling HF by-product, characterized in that CF 4 The volume ratio of the water vapor to the water vapor is 1:50.
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