CN113072087B - Preparation method of high-purity alumina - Google Patents
Preparation method of high-purity alumina Download PDFInfo
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- CN113072087B CN113072087B CN202110423856.XA CN202110423856A CN113072087B CN 113072087 B CN113072087 B CN 113072087B CN 202110423856 A CN202110423856 A CN 202110423856A CN 113072087 B CN113072087 B CN 113072087B
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 238000002360 preparation method Methods 0.000 title claims abstract description 32
- 230000001590 oxidative effect Effects 0.000 claims abstract description 59
- 238000001354 calcination Methods 0.000 claims abstract description 50
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 claims abstract description 48
- 239000007789 gas Substances 0.000 claims description 62
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 33
- 239000001301 oxygen Substances 0.000 claims description 33
- 229910052760 oxygen Inorganic materials 0.000 claims description 33
- 238000000034 method Methods 0.000 claims description 26
- 238000006460 hydrolysis reaction Methods 0.000 claims description 21
- 229910052782 aluminium Inorganic materials 0.000 claims description 18
- -1 aluminum alkoxide Chemical class 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 238000005086 pumping Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 24
- 125000003545 alkoxy group Chemical group 0.000 abstract description 4
- 239000008204 material by function Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 31
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 18
- 229910052799 carbon Inorganic materials 0.000 description 17
- 238000010438 heat treatment Methods 0.000 description 17
- 238000004321 preservation Methods 0.000 description 14
- 229910052593 corundum Inorganic materials 0.000 description 13
- 239000010431 corundum Substances 0.000 description 13
- 238000011049 filling Methods 0.000 description 13
- 238000003756 stirring Methods 0.000 description 12
- 239000002002 slurry Substances 0.000 description 11
- 238000001035 drying Methods 0.000 description 10
- 229910052757 nitrogen Inorganic materials 0.000 description 10
- 239000007788 liquid Substances 0.000 description 9
- 238000001694 spray drying Methods 0.000 description 9
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 8
- 238000000926 separation method Methods 0.000 description 8
- 239000012265 solid product Substances 0.000 description 8
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- 230000003647 oxidation Effects 0.000 description 7
- 238000007254 oxidation reaction Methods 0.000 description 7
- 235000011837 pasties Nutrition 0.000 description 7
- 239000000843 powder Substances 0.000 description 7
- 239000011734 sodium Substances 0.000 description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 150000004703 alkoxides Chemical class 0.000 description 6
- 230000007062 hydrolysis Effects 0.000 description 6
- 239000012498 ultrapure water Substances 0.000 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 description 5
- OFEPSGLLYPYMDB-UHFFFAOYSA-K aluminum;hexanoate Chemical compound [Al+3].CCCCCC([O-])=O.CCCCCC([O-])=O.CCCCCC([O-])=O OFEPSGLLYPYMDB-UHFFFAOYSA-K 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000010992 reflux Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000004155 Chlorine dioxide Substances 0.000 description 4
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- 238000007605 air drying Methods 0.000 description 4
- 235000019398 chlorine dioxide Nutrition 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000001291 vacuum drying Methods 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 239000003082 abrasive agent Substances 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- HSEYYGFJBLWFGD-UHFFFAOYSA-N 4-methylsulfanyl-2-[(2-methylsulfanylpyridine-3-carbonyl)amino]butanoic acid Chemical compound CSCCC(C(O)=O)NC(=O)C1=CC=CN=C1SC HSEYYGFJBLWFGD-UHFFFAOYSA-N 0.000 description 1
- 238000004131 Bayer process Methods 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000003837 high-temperature calcination Methods 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 239000000413 hydrolysate Substances 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- YQCIWBXEVYWRCW-UHFFFAOYSA-N methane;sulfane Chemical compound C.S YQCIWBXEVYWRCW-UHFFFAOYSA-N 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- 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
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
-
- 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
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention belongs to the technical field of inorganic functional materials, and particularly relates to a preparation method of high-purity alumina. The preparation method of the high-purity alumina provided by the invention comprises the following steps of calcining pseudo-boehmite in a circulating oxidizing gas atmosphere; the circulating oxidizing gas atmosphere is obtained by the circulation of introducing oxidizing gas for pressure maintaining after vacuumizing; the cycle is repeated a number of times > 1. The preparation method provided by the invention can enable the pseudo-boehmite to be fully contacted with oxidizing gas, and fully oxidize the alkoxy groups remained in the pseudo-boehmite, and the results of the embodiment show that the carbon residue of the high-purity alumina prepared by the preparation method provided by the invention is less than 0.001 wt%, the purity is more than 99.99 wt%, and the whiteness is more than 95%.
Description
Technical Field
The invention belongs to the technical field of inorganic functional materials, and particularly relates to a preparation method of high-purity alumina.
Background
High-purity alumina is a very important fine chemical and is applied to the fields of sapphire single crystals, fine ceramics, high-pressure sodium lamp light-transmitting tubes, high-end abrasives and the like.
The production methods of the high-purity alumina include alkoxide hydrolysis, metal aluminum hydration, aluminum ammonium sulfate pyrolysis and modified Bayer process, among the methods, the aluminum alkoxide hydrolysis has the advantages of stable product property, environment-friendly process and the like, and is considered to be the most efficient method for preparing the high-purity alumina.
The alkoxide hydrolysis method mainly adopts aluminum alkoxide as a raw material, and the aluminum alkoxide and water are mixed to obtain a hydrolysate which is then dried to obtain pseudo-boehmite, and the pseudo-boehmite is calcined to obtain alumina. However, since the alkoxide remains after the aluminum alkoxide is hydrolyzed and dried, although the residual alkoxide is oxidized and gasified by the oxidizing atmosphere through the high-temperature calcination process, some of the alkoxide wrapped in the pseudo-boehmite particles are carbonized due to insufficient contact with oxygen, and thus carbon is generated and remains in the alumina. The carbon residue in the alumina prepared by the alkoxide hydrolysis method is 0.005-0.03 wt%, and the alumina has no adverse effect on the application of fine ceramics, high-end abrasives and the like; however, when alumina polycrystal or single crystal is produced as a raw material by a cold crucible electromagnetic induction melting method, the obtained alumina polycrystal or single crystal may appear yellowish or even brown.
Disclosure of Invention
In view of the above, the present invention provides a method for preparing high purity alumina, the high purity alumina prepared by the method provided by the present invention has a residual carbon content of less than 0.001 wt%, a purity of more than 99.99 wt%, and a whiteness value of more than 95%, and the alumina polycrystal or single crystal prepared from the high purity alumina provided by the present invention is colorless by visual observation.
The invention provides a preparation method of high-purity alumina, which comprises the following steps:
calcining pseudo-boehmite in a circulating oxidizing gas atmosphere;
the circulating oxidizing gas atmosphere is obtained by the circulation of introducing oxidizing gas for pressure maintaining after vacuumizing;
the number of cycle repetitions is > 1.
Preferably, the calcining temperature is 500-1000 ℃, and the calcining heat preservation time is 3-6 h.
Preferably, the calcining temperature is obtained by heating, and the heating rate is 3-8 ℃/min.
Preferably, the evacuation is to an absolute pressure <0.01Mpa per cycle; carrying out primary vacuum pumping during the temperature rise;
and in each cycle, introducing oxidizing gas to the absolute pressure of 0.08-0.12 MPa.
Preferably, the dwell time of the oxidizing gas is 5 to 15min per cycle.
Preferably, the oxidizing gas contains oxygen, and the volume content of the oxygen in the oxidizing gas is more than or equal to 20%.
Preferably, the oxidizing gas is one or more of oxygen, ozone, nitrogen, carbon dioxide, chlorine dioxide, sulfur dioxide, nitric oxide and an inert gas.
Preferably, the preparation method of the pseudoboehmite comprises the following steps: mixing aluminum alkoxide and water for hydrolysis reaction to obtain pseudo-boehmite;
the temperature of the hydrolysis reaction is 60-100 ℃, and the time of the hydrolysis reaction is 2.5-8 h.
Preferably, the aluminum alkoxide has the formula Al (C) n H 2n+1 O) 3 N is more than or equal to 3 and less than or equal to 8;
preferably, the mass ratio of the aluminum alkoxide to the water is 4: (1-6).
The invention provides a preparation method of high-purity alumina, which comprises the following steps: calcining pseudo-boehmite in a circulating oxidizing gas atmosphere; the circulating oxidizing gas atmosphere is obtained by the circulation of introducing oxidizing gas for pressure maintaining after vacuumizing; the number of cycle repetitions is > 1. When the pseudo-boehmite is calcined by the preparation method provided by the invention, along with the circulation of vacuumizing, introducing oxidizing gas and maintaining pressure of the oxidizing gas, the atmosphere environment during calcination (vacuumizing and introducing oxidizing gas for maintaining pressure) is continuously changed, so that the pseudo-boehmite and the oxidizing gas can be more fully contacted, and alkoxy groups remained in the pseudo-boehmite are fully oxidized, thereby preparing the high-purity alumina.
Detailed Description
The invention provides a preparation method of high-purity alumina, which comprises the following steps:
calcining pseudo-boehmite in a circulating oxidizing gas atmosphere;
the circulating oxidizing gas atmosphere is obtained by vacuumizing and then introducing oxidizing gas for pressure maintaining;
the number of cycle repetitions is > 1.
In the present invention, the starting materials are all commercially available products well known to those skilled in the art, unless otherwise specified.
In the present invention, the preparation method of the pseudoboehmite preferably comprises:
mixing aluminum alkoxide and water for hydrolysis reaction to obtain pseudo-boehmite;
the temperature of the hydrolysis reaction is 60-100 ℃, and the time of the hydrolysis reaction is 2.5-8 h.
In the invention, aluminum alkoxide and water are mixed for hydrolysis reaction, and the chemical formula of the aluminum alkoxide is preferably Al (C) n H 2n+ 1 O) 3 N is more than or equal to 3 and less than or equal to 8; in a particular embodiment of the invention, the aluminum alkoxide is preferably aluminum isopropoxide or aluminum hexanoate. In the present invention, the purity of the aluminum alkoxide is preferably not less than 99%, and the aluminum alkoxide contains Na element, Fe element, Si element, K element, Ca element, and Cu elementThe total content of the elements Ti and Zn is less than or equal to 0.001 wt%.
In the present invention, the water is preferably high purity water.
In the present invention, the mass ratio of the aluminum alkoxide to water is preferably 4: (1-8), more preferably 4: (1.1-6).
In the invention, the temperature of the hydrolysis reaction is 60-100 ℃, preferably 65-85 ℃; the hydrolysis reaction time is 2.5-8 h, preferably 3-4 h; in the present invention, the hydrolysis reaction is preferably carried out under stirring, and the present invention has no special requirement for the specific implementation process of the stirring. In the present invention, the hydrolysis reaction is preferably carried out in a reaction vessel equipped with a reflux apparatus and a stirring apparatus.
The hydrolysis reaction is carried out to obtain the pseudo-boehmite slurry, and the pseudo-boehmite is preferably obtained by carrying out post-treatment on the pseudo-boehmite slurry. In the present invention, the post-treatment preferably includes: sequentially carrying out solid-liquid separation, drying and crushing on the pseudo-boehmite slurry; in the invention, the solid-liquid separation is preferably centrifugal separation, the rotating speed of the centrifugal separation is preferably 4500-5500 r/min, the invention has no special requirement on the specific implementation process of the centrifugal separation, and in the specific implementation of the invention, the centrifugal separation is preferably carried out in a centrifuge.
The solid-liquid separation is carried out to obtain a pasty solid product, the pasty solid product is preferably dried, and in the invention, the drying is preferably vacuum drying, flash drying, forced air drying or spray drying; in the invention, the temperature of the vacuum drying is preferably 80-95 ℃, the time of the vacuum drying is preferably 5-7 h, and the invention has no special requirement on the vacuum degree of the vacuum drying; in the invention, the flash drying is preferably carried out in a closed-cycle flash dryer, the feeding temperature of the closed-cycle flash dryer is preferably 200-250 ℃, the discharging temperature is preferably 80-90 ℃, and the protective atmosphere of the flash drying is preferably nitrogen or inert gas, more preferably nitrogen; in the invention, the temperature of the forced air drying is preferably 100-110 ℃, and the time of the forced air drying is 7-9 h; in the invention, the spray drying is preferably carried out by mixing the pasty solid product with water to obtain a mixture and then carrying out spray drying in a spray drying agent, the dosage of the water is not particularly required in the invention, so that the obtained mixture can be subjected to spray drying, the feeding temperature of the spray drying is preferably 300-400 ℃, more preferably 350 ℃, and the discharging temperature of the spray drying is preferably 95-105 ℃, more preferably 100 ℃.
The present invention preferably pulverizes the dried product, and the present invention does not specifically require the specific implementation of the pulverization, and in the present invention, the particle size of the pseudoboehmite is preferably <150 μm, and in the present invention, when the pasty solid product is dried by spray drying, the pulverization is preferably omitted.
The invention calcines pseudo-boehmite in a circulating oxidizing gas atmosphere; in the invention, the cyclic oxidizing gas atmosphere is obtained by the cycle of introducing oxidizing gas for pressure maintaining after vacuumizing; the number of cycle repetitions is > 1.
In the invention, in each cycle, the vacuumizing is preferably carried out until the absolute pressure is less than 0.01MPa, and more preferably until the absolute pressure is 0.005-0.008 MPa; the temperature is preferably raised during the first evacuation, and the evacuation is more preferably performed at the start of the temperature rise; the invention has no special requirement on the specific time of the vacuum pumping, and is determined according to the specific working efficiency of the vacuum pumping device used in the actual production process.
The oxidizing gas is directly introduced after the vacuum pumping, the vacuum pumping time of the invention is less than the temperature rise time, and the temperature rise process is not finished when the first vacuum pumping is finished.
In the invention, the oxidizing gas is preferably introduced to an absolute pressure of 0.08 to 0.12MPa, more preferably to an absolute pressure of 0.09 to 0.1 MPa; the invention has no special requirement on the specific time of introducing the oxidizing gas and is determined according to the specific working efficiency of the device for introducing the oxidizing gas used in the actual production process.
In the present invention, the oxidizing gas contains oxygen, and the volume content of the oxygen in the oxidizing gas is preferably not less than 20%, and more preferably not less than 21%; in the present invention, the oxidizing gas is preferably one or more of oxygen, ozone, nitrogen, carbon dioxide, chlorine dioxide, sulfur dioxide, nitric oxide, and an inert gas, and the inert gas is preferably helium and/or argon, and in a specific embodiment of the present invention, the oxidizing gas is preferably a mixed gas of oxygen and nitrogen, a mixed gas of oxygen and ozone, a mixed gas of oxygen and chlorine dioxide, a mixed gas of oxygen and carbon monoxide, or a mixed gas of oxygen and chlorine.
In the present invention, the dwell time of the oxidizing gas is preferably 5 to 15min, and more preferably 6 to 12min per cycle.
And after the pressure maintaining is finished, performing the next cycle of vacuumizing and introducing oxidizing gas for pressure maintaining.
In the invention, the calcining temperature is preferably 500-1000 ℃, and more preferably 600-850 ℃; the heat preservation time of the calcination is preferably 3-6 h, and more preferably 3.5-5 h.
In the invention, the calcining temperature is preferably obtained by heating, and the heating rate is preferably 3-8 ℃/min, and more preferably 3.5-4.5 ℃/min.
In the present invention, the calcination is preferably performed in a vacuum furnace, in a specific embodiment of the present invention, the pseudoboehmite is preferably placed in a crucible of the vacuum furnace, the filling height of the pseudoboehmite in the crucible is preferably 145-155 mm, and more preferably 150mm, and in the present invention, the crucible is preferably made of corundum.
According to the invention, the filling height of the pseudo-boehmite in the crucible is controlled, so that the calcination efficiency of the pseudo-boehmite in the calcination process is improved, and the unit energy consumption in the preparation process is reduced to the maximum extent.
In the present invention, after the calcination, the obtained calcination system is preferably subjected to a post-treatment to obtain the high purity alumina, and in the present invention, the post-treatment preferably includes: and sequentially carrying out vacuum pumping, oxygen introduction and cooling. In the present invention, the specific implementation processes of the vacuum-pumping and the oxygen-introducing are the same as the specific implementation processes of the vacuum-pumping and the oxygen-introducing in the calcination process described above, and are not described herein again. In the present invention, the temperature after the cooling is preferably room temperature.
When the preparation method provided by the invention is used for calcining the pseudo-boehmite, the pseudo-boehmite can be fully contacted with oxidizing gas by circularly performing vacuumizing, introducing oxidizing gas and maintaining pressure, and residual alkoxy in the pseudo-boehmite is fully oxidized, so that the high-purity alumina with low residual carbon content is prepared.
In order to further illustrate the present invention, the following embodiments are described in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
Introducing 2kg of liquid aluminum isopropoxide (the purity is 99.5%, and the total content of Na element, Fe element, Si element, K element, Ca element, Cu element, Ti element and Zn element is 0.0008 wt.%) into a 4L reaction kettle with reflux and stirring equipment, adding 550g of high-purity water into the reaction kettle under the condition of stirring at 80 ℃, and continuing stirring for 4 hours after water is added, so that the aluminum isopropoxide is hydrolyzed into pseudo-boehmite-isopropanol-water slurry; centrifuging the slurry by using a centrifuge (the rotating speed is 5000r/min), and drying the obtained pasty solid product in vacuum at the drying temperature of 90 ℃ for 6 h; the obtained dry product is crushed into powder with the particle size of less than 150 mu m to obtain pseudo-boehmite;
then placing the pseudo-boehmite into a corundum crucible with the filling height of 150mm, calcining in a vacuum furnace, wherein the calcining procedure is to heat up the pseudo-boehmite to 600 ℃ from room temperature at the heating rate of 5 ℃/min, and preserving the heat for 4h at 600 ℃. During the heating calcination and the heat preservation calcination, firstly, starting a vacuum system to extract air, stopping vacuumizing until the absolute pressure in the vacuum furnace is 0.005MPa, and introducing oxygen and nitrogen (the volume ratio is 21: 79) into the vacuum furnace; introducing oxidizing gas until the absolute pressure in the vacuum furnace is 0.1MPa, stopping introducing gas, and maintaining pressure for oxidation for 10 min. And then continuously and circularly carrying out operations of vacuumizing, introducing oxygen and nitrogen (the volume ratio is 21: 79) and pressure maintaining oxidation until the heat preservation calcination is finished, vacuumizing the vacuum furnace after the heat preservation is finished, introducing oxygen (the absolute pressure in the furnace is kept at 0.1MPa), cooling the vacuum furnace, and taking out the high-purity aluminum oxide product.
The carbon content, purity and whiteness of the high-purity alumina product prepared in example 1 were measured using a carbon-sulfur analyzer, an inductively coupled plasma spectrometer and a whiteness meter, wherein the purity of the alumina product was measured as follows: measuring the total amount of impurities of Na element, Fe element, Si element, K element, Ca element, Cu element, Ti element and Zn element in the alumina, and deducting the total amount of the impurities to obtain the purity of the alumina product; the product of example 1 had a whiteness of 96.5%, a carbon residue of 0.0008 wt.% and a purity of 99.995%.
Comparative example 1
The preparation method is basically the same as that of example 1, except that: placing pseudo-boehmite into a corundum crucible, filling the corundum crucible with the filling height of 150mm, calcining in a muffle furnace in an air atmosphere, heating at the rate of 5 ℃/min, and preserving heat for 4 hours at the temperature of 600 ℃.
The alumina product prepared in comparative example 1 had a residual carbon content of 0.015 wt.%, a whiteness of 75.2%, a purity of 99.994%, and a gray color as seen with the naked eye, measured in the same manner as in example 1.
Example 2
Introducing 2000kg of liquid aluminum isopropoxide (the purity is 99%, and the total content of Na element, Fe element, Si element, K element, Ca element, Cu element, Ti element and Zn element is 0.0009 wt.%) into a 4000L reaction kettle with a reflux device, adding 550kg of high-purity water into the reaction kettle under the condition of stirring at 80 ℃, and continuing stirring for 4 hours after water is added, so that the aluminum isopropoxide is hydrolyzed into pseudo-boehmite-isopropanol-water slurry; centrifuging the slurry by using a centrifuge (the rotating speed is 5000r/min), drying the obtained pasty solid product in a closed-loop circulating flash evaporation dryer, wherein the protective gas is nitrogen, the feeding temperature is 250 ℃, and the discharging temperature is 90 ℃; the obtained dry product is crushed into powder with the particle size of more than 150 mu m to obtain pseudo-boehmite;
then placing the pseudo-boehmite into a corundum crucible with the filling height of 150mm, calcining in a vacuum furnace, wherein the calcining procedure is to heat up to 800 ℃ from room temperature at the heating rate of 5 ℃/min, and preserving heat for 4h at 800 ℃. During the period from heating calcination to heat preservation calcination beam, firstly, starting a vacuum system to extract air, stopping vacuum extraction until the absolute pressure in the vacuum furnace is 0.005MPa, and then introducing oxygen and nitrogen (the volume ratio is 21: 79) into the vacuum furnace; introducing oxidizing gas until the absolute pressure in the vacuum furnace is 0.1MPa, stopping introducing gas, and maintaining pressure for oxidation for 10 min. And then, continuously and circularly carrying out operations of vacuumizing, introducing oxygen and nitrogen (the volume ratio is 21: 79) and maintaining pressure for oxidizing for 10min until the heat preservation and calcination are finished, vacuumizing the vacuum furnace after the heat preservation and calcination are finished, introducing oxygen (the absolute pressure in the furnace is kept at 0.1MPa), and cooling the vacuum furnace to take out the high-purity aluminum oxide product.
When the product prepared in example 2 is tested in the same manner as in example 1, the whiteness of the high purity alumina prepared in example 2 is more than 96.0%, the carbon residue is less than 0.0008 wt%, and the purity is more than 99.995%.
Comparative example 2
The preparation method is basically the same as that of example 2, except that: placing pseudo-boehmite into a corundum crucible, filling the corundum crucible with the filling height of 150mm, calcining the corundum crucible in a kiln in air atmosphere, and keeping the temperature at 800 ℃ for 4h at the heating rate of 5 ℃/min.
The alumina product prepared in comparative example 2 had a residual carbon content of 0.02 wt.%, a whiteness of 73.2% and a purity of 99.993, measured in the same manner as in example 1.
Example 3
The preparation method is basically the same as that of example 1, except that: the oxidizing gas is oxygen;
the alumina product prepared in example 3 had a residual carbon content of 0.0009% wt, a whiteness of 96% and a purity of 99.994% as measured in the same manner as in example 1.
Example 4
The preparation method is basically the same as that of example 1, except that: the oxidizing gas is oxygen and argon (the volume ratio is 80: 20);
the alumina product prepared in example 4 had a residual carbon content of 0.0009 wt%, a whiteness of 95.7% and a purity of 99.995, measured in the same manner as in example 1.
Example 5
The preparation method is basically the same as that of example 1, except that: the oxidizing gas is oxygen and carbon dioxide (volume ratio is 50: 50);
the alumina product obtained in example 5 had a residual carbon content of 0.0008 wt%, a whiteness of 95.5% and a purity of 99.996% as measured in the same manner as in example 1.
Example 6
Introducing 1kg of liquid aluminum hexanoate (the purity is 99.5%, and the total content of Na element, Fe element, Si element, K element, Ca element, Cu element, Ti element and Zn element is 0.0003 wt.%) into a 4L reaction kettle with a reflux device, adding 1.5kg of high-purity water into a hydrolysis kettle under the condition of stirring at 100 ℃, and continuing stirring for 8 hours after the water is added, so that the aluminum hexanoate is hydrolyzed into pseudo-boehmite-n-hexanol-water slurry; centrifuging the slurry by using a centrifuge (the rotating speed is 5000 r/min); drying the obtained pasty solid product in a forced air drying oven at 105 ℃ for 8 h; the dried product is crushed into powder with the particle size of less than 150 mu m to obtain pseudo-boehmite;
then placing the pseudo-boehmite into a corundum crucible with the filling height of 150mm, calcining in a vacuum furnace, wherein the calcining procedure is to heat up to 600 ℃ from room temperature at the heating rate of 5 ℃/min, and preserving heat for 4h at 600 ℃. During the heating calcination and the heat preservation calcination, firstly, starting a vacuum system to pump air, stopping vacuumizing until the absolute pressure in a vacuum furnace is 0.005MPa, and introducing oxygen and ozone (the volume ratio is 50:50) into the vacuum furnace; introducing oxidizing gas until the absolute pressure in the vacuum furnace is 0.1MPa, stopping introducing gas, and maintaining pressure for oxidation for 5 min. And then, continuously repeating the operations of vacuumizing, introducing oxygen and ozone (the volume ratio is 50:50) and maintaining pressure for oxidation until the heat preservation and calcination are finished, vacuumizing the vacuum furnace after the heat preservation is finished, introducing oxygen (the absolute pressure in the furnace is kept at 0.1MPa), and cooling the vacuum furnace and taking out the high-purity aluminum oxide product.
The high purity alumina product prepared in example 6 had a whiteness of 96.5%, a residual carbon of 0.0007 wt.% and a purity of 99.995%, as determined in the same manner as in example 1.
Comparative example 3
The preparation method is basically the same as that of example 6, except that: placing pseudo-boehmite into a corundum crucible, filling the corundum crucible with the filling height of 150mm, calcining in a muffle furnace in an air atmosphere, heating at the rate of 5 ℃/min, and preserving heat for 4 hours at the temperature of 600 ℃.
The alumina product prepared in comparative example 3 had a residual carbon content of 0.025 wt.%, a whiteness of 70.4%, an alumina purity of 99.993%, and a gray-black color of the product at the bottom of the crucible after calcination, as measured in the same manner as in example 1.
Example 7
Introducing 1000kg of liquid aluminum hexanoate (the purity is 99%, and the total content of Na element, Fe element, Si element, K element, Ca element, Cu element, Ti element and Zn element is 0.0003 wt.%) into a 4000L reaction kettle with reflux equipment, adding 1500kg of high-purity water into a hydrolysis kettle under the condition of stirring at 100 ℃, and continuing stirring for 8 hours after water is added to hydrolyze the aluminum hexanoate into pseudo-boehmite-n-hexanol-water slurry; centrifuging the slurry with a horizontal screw centrifuge (4800 r/min); uniformly mixing the paste solid product obtained by separation with 200kg of high-purity water; spray drying the obtained mixture, wherein the feeding temperature is 350 ℃, and the discharging temperature is 100 ℃; drying to obtain pseudo-boehmite;
then placing the pseudo-boehmite into a corundum crucible with the filling height of 150mm, calcining in a vacuum furnace, wherein the calcining procedure is to heat up to 800 ℃ from room temperature at the heating rate of 5 ℃/min, and preserving heat for 4h at 800 ℃. During the period from heating calcination to heat preservation calcination beam, firstly, starting a vacuum system to pump air, stopping vacuumizing until the absolute pressure in the vacuum furnace is 0.005MPa, and then introducing oxygen and ozone (the volume ratio is 50:50) into the vacuum furnace; introducing oxidizing gas until the absolute pressure in the vacuum furnace is 0.1MPa, stopping introducing gas, and maintaining pressure for oxidation for 5 min. And then, continuously and repeatedly carrying out operations of vacuumizing, introducing oxygen and ozone (the volume ratio is 50:50) and maintaining pressure and oxidizing for 5min until the heat preservation and calcination are finished, vacuumizing the vacuum furnace after the heat preservation and calcination are finished, introducing oxygen (the absolute pressure in the furnace is kept at 0.1MPa), cooling the vacuum furnace, and taking out the high-purity aluminum oxide product.
The product of example 7 was tested in the same manner as in example 1 and the high purity alumina of example 7 had a whiteness of 96.6%, a carbon residue of 0.0006 wt.% and a purity of 99.995%.
Comparative example 4
The preparation process was substantially the same as that of example 7 except that: the pseudo-boehmite is put into a corundum crucible, the filling height is 150mm, the pseudo-boehmite is calcined in a kiln in air atmosphere, the heating rate is 5 ℃/min, and the temperature is kept for 4h at 800 ℃.
The alumina product prepared in comparative example 4 had a residual carbon content of 0.018 wt%, a whiteness of 74% and a purity of 99.994%, measured in the same manner as in example 1.
Example 8
The preparation method is basically the same as that of example 6, except that: the oxidizing gas is oxygen and chlorine dioxide (volume ratio is 50: 50);
the alumina product obtained in example 8 had a residual carbon content of 0.00051% wt, a whiteness of 96.8% and a purity of 99.993%, measured in the same manner as in example 1.
Example 9
The preparation method is basically the same as that of example 6, except that: the oxidizing gas is oxygen and nitric oxide (the volume ratio is 70: 20);
the alumina product prepared in example 9 had a carbon residue of less than 0.0006 wt%, a whiteness of 96.3%, and a purity of 99.996%, as determined by the same method as in example 1.
Example 10
The preparation method is basically the same as that of example 6, except that: the oxidizing gas is oxygen and nitric oxide (the volume ratio is 70: 20);
the alumina product obtained in example 10 had a residual carbon content of 0.0005% by weight, a whiteness of 96.8% and a purity of 99.994% as measured in the same manner as in example 1.
Application example 1
Adding the high-purity alumina powder (the thickness is 15cm) and the high-purity graphite flake (the thickness is 0.5cm) prepared in the example 2 into a cold crucible, starting a water cooling system of the crucible and a high-frequency coil outside the crucible to generate a magnetic field, and heating the mixture through the magnetic field until all the alumina powder in the crucible forms molten liquid; and starting a crucible power system to move the crucible, adding high-purity alumina powder into the crucible in the moving process until the crucible moves to the top point position, simultaneously enabling the high-purity alumina powder in the crucible to completely form molten liquid, and cooling to room temperature to obtain the alumina polycrystal. The alumina polycrystal was visually observed to be colorless.
Comparative example 5
The preparation method is basically the same as that of application example 1, except that: the alumina prepared in the comparative example 2 is used as a raw material, and the product alumina polycrystal is visually observed to have faint yellow, yellow or brown and other mixed colors.
Application example 2
The preparation method is basically the same as that of application example 1, except that: the high purity alumina prepared in example 7 was used as a starting material, and the alumina polycrystal was visually observed to be colorless.
Comparative example 6
The preparation method is basically the same as that of application example 1, except that: the alumina prepared in comparative example 4 was used as a raw material, and the product alumina polycrystal was visually observed to appear a pale yellow, yellow or brown color or other discolor.
The properties of the alumina products prepared in examples 1 to 10 and comparative examples 1 to 4 are shown in table 1, and it can be seen from table 1 that, compared with calcination in an air atmosphere, the preparation method provided by the present invention is adopted: in the calcining process, the steps of vacuumizing, introducing oxidizing gas and maintaining pressure for oxidation are circularly carried out, the pseudo-boehmite can be fully contacted with the oxidizing gas, and the alkoxy groups remained in the pseudo-boehmite are fully oxidized, so that the high-purity alumina with low residual carbon content is prepared, wherein the residual carbon content is less than 0.001 wt%, the purity is more than 99.99 wt%, and the whiteness value is more than 95%.
TABLE 1 Performance test results for the aluminas prepared in examples 1-10 and comparative examples 1-4
| Serial number | Content of residual carbon/wt. -%) | Purity/%) | Whiteness value/%) |
| Example 1 | 0.0008 | 99.995 | 96.5 |
| Example 2 | 0.0008 | 99.995 | 96.0 |
| Example 3 | 0.0009 | 99.994 | 96.0 |
| Example 4 | 0.0009 | 99.995 | 95.7 |
| Example 5 | 0.0008 | 99.996 | 95.5 |
| Example 6 | 0.0007 | 99.996 | 96.5 |
| Example 7 | 0.0006 | 99.995 | 96.6 |
| Example 8 | 0.0005 | 99.993 | 96.8 |
| Example 9 | 0.0006 | 99.996 | 96.3 |
| Example 10 | 0.0005 | 99.994 | 96.8 |
| Comparative example 1 | 0.015 | 99.994 | 75.2 |
| Comparative example 2 | 0.020 | 99.993 | 73.2 |
| Comparative example 3 | 0.025 | 99.993 | 70.4 |
| Comparative example 4 | 0.018 | 99.994 | 74.3 |
Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.
Claims (8)
1. A preparation method of high-purity alumina comprises the following steps:
calcining pseudo-boehmite in a circulating oxidizing gas atmosphere;
the circulating oxidizing gas atmosphere is obtained by the circulation of introducing oxidizing gas for pressure maintaining after vacuumizing; the oxidizing gas contains oxygen, and the volume content of the oxygen in the oxidizing gas is more than or equal to 20%;
the number of cycle repetitions is > 1.
2. The preparation method of claim 1, wherein the calcination temperature is 500-1000 ℃, and the calcination holding time is 3-6 h.
3. The preparation method according to claim 2, wherein the calcination temperature is obtained by raising the temperature, and the rate of raising the temperature is 3-8 ℃/min.
4. The method of claim 3, wherein the evacuation is to an absolute pressure <0.01Mpa per cycle; carrying out primary vacuum pumping during the temperature rise;
in each cycle, oxidizing gas is introduced to an absolute pressure of 0.08 to 0.12 MPa.
5. The production method according to claim 1 or 4, wherein the dwell time of the oxidizing gas in each cycle is 5 to 15 min.
6. The method of claim 1, wherein the pseudoboehmite is prepared by a method comprising: mixing aluminum alkoxide and water for hydrolysis reaction to obtain pseudo-boehmite;
the temperature of the hydrolysis reaction is 60-100 ℃, and the time of the hydrolysis reaction is 2.5-8 h.
7. The production method according to claim 6, wherein the aluminum alkoxide has a chemical formula of Al (C) n H 2n+1 O) 3 ，3≤n≤8。
8. The production method according to claim 6, wherein the mass ratio of the aluminum alkoxide to the water is 4: (1-6).
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