CA2002254A1 - Process for the production of fine tabular alumina monohydrate - Google Patents
Process for the production of fine tabular alumina monohydrateInfo
- Publication number
- CA2002254A1 CA2002254A1 CA002002254A CA2002254A CA2002254A1 CA 2002254 A1 CA2002254 A1 CA 2002254A1 CA 002002254 A CA002002254 A CA 002002254A CA 2002254 A CA2002254 A CA 2002254A CA 2002254 A1 CA2002254 A1 CA 2002254A1
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- Prior art keywords
- liquor
- molar ratio
- process according
- less
- organic carbon
- Prior art date
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- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/40—Compounds of aluminium
- C09C1/407—Aluminium oxides or hydroxides
-
- 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
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
- C01F7/144—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by precipitation due to cooling, e.g. as part of the Bayer process
-
- 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
- C01F7/46—Purification of aluminium oxide, aluminium hydroxide or aluminates
- C01F7/47—Purification of aluminium oxide, aluminium hydroxide or aluminates of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors
- C01F7/473—Removal of organic compounds, e.g. sodium oxalate
- C01F7/476—Removal of organic compounds, e.g. sodium oxalate by oxidation
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/675—Oxides, hydroxides or carbonates
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H19/00—Coated paper; Coating material
- D21H19/36—Coatings with pigments
- D21H19/38—Coatings with pigments characterised by the pigments
- D21H19/385—Oxides, hydroxides or carbonates
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
- D21H21/50—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by form
- D21H21/52—Additives of definite length or shape
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/01—Crystal-structural characteristics depicted by a TEM-image
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/20—Particle morphology extending in two dimensions, e.g. plate-like
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
ABSTRACT
A process for the production of fine, tabular alpha-alumina monohydrate crystals characterized by the following steps:
- adjustment of a caustic aluminate liquor at temperatures above C8 until the molar ratio of the liquor Na2Ofree/Al2O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic conditions of intensive agitation in order to induce nuclea-tion of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
A process for the production of fine, tabular alpha-alumina monohydrate crystals characterized by the following steps:
- adjustment of a caustic aluminate liquor at temperatures above C8 until the molar ratio of the liquor Na2Ofree/Al2O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic conditions of intensive agitation in order to induce nuclea-tion of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
Description
ZC!~32ZS4 PROCE5S FOR ~HE PRODUCTION OF
FINE, TABULAR ALUMINA MO~OHYDRATE
ELD OF THE INVENTION
This invention relates to a process for the pro-duction of fine, tabular alpha-alumina monohydrate (boehmite) crystals suitable for use as a pigment/filler.
The present invention provides a process for the production of boehmite crystals of a size and a shape suitable for use as a pigment/filler in paper, paint and ink applica-tions.
It is known that boehmite is thethermodynamically stable phase of alumina monohydrate at temperatures greater than 100C in liquors of the well-known Bayer process for the production of alumina from bauxite. Accordingly, boehmite can be precipitated at temperatures above 100C from these caustic aluminate liquors. Although the initial rate of boeh-mite precipitation increases with increasing temperature, the yield may decrease since the degree of supersaturation with respect to alu~ina decreases.
The greatest degree of boehmite precipitation occurs in sodium aluminate liquors under hydrothermal conditions (i.e., conditions of elevated temperature and pressure) of about 140C when employing a caustic aluminate liquor having a molar ratio of 1.3, a retention time in the autoclave of 4-12 hours and a large seed charge, 260-340 g/l of boehmite , . , . .. ; ~. . .
, :. . . ~ - . : .
.
"
.. . . ~
:
FINE, TABULAR ALUMINA MO~OHYDRATE
ELD OF THE INVENTION
This invention relates to a process for the pro-duction of fine, tabular alpha-alumina monohydrate (boehmite) crystals suitable for use as a pigment/filler.
The present invention provides a process for the production of boehmite crystals of a size and a shape suitable for use as a pigment/filler in paper, paint and ink applica-tions.
It is known that boehmite is thethermodynamically stable phase of alumina monohydrate at temperatures greater than 100C in liquors of the well-known Bayer process for the production of alumina from bauxite. Accordingly, boehmite can be precipitated at temperatures above 100C from these caustic aluminate liquors. Although the initial rate of boeh-mite precipitation increases with increasing temperature, the yield may decrease since the degree of supersaturation with respect to alu~ina decreases.
The greatest degree of boehmite precipitation occurs in sodium aluminate liquors under hydrothermal conditions (i.e., conditions of elevated temperature and pressure) of about 140C when employing a caustic aluminate liquor having a molar ratio of 1.3, a retention time in the autoclave of 4-12 hours and a large seed charge, 260-340 g/l of boehmite , . , . .. ; ~. . .
, :. . . ~ - . : .
.
"
.. . . ~
:
- 2"n2~s4 crystals, (see, for examplel S.I. Kuznetson et al "Precipita-tion from supersaturated aluminate solutions at temperatures of 100 - 160C. Zhurn. Prikl. Khim., 1973, No. 7, pp.
1574-1575).
The term molar ratio can be defined as follows:
(Moles Caustic in Solution)/(Moles Alumina in Solution) =
(1.645)x[g/1 Na2Ofree]/[g/1 A12O3]
In the above equation, Na2Ofree is defined as the amount of caustic present as NaOH and combined with alumina as sodium aluminate.
For example, a Bayer liquor which contains 140 g/l of free caustic (expressed as Na2Ofree) and 177 g/l alumina has a molar ratio of 1.3 using the above equation.
Alternatively, it is known that, depending upon the liquor composition, under atmospheric pressure conditions, and at temperatures of up to about 140C, crystalline boehmite can be precipitated from Bayer liquors. This is accomplished using 100 g/l of a very fine gel-type boehmite seed (such as CATAPAL*, made by CONOCO INC.), a 1.4 to 1.5 molar ratio and a retention time of 6 hours in the autoclave, as described for example in the West German Patent application of C. Misra et al., DE 3528534Al (August 8, 1985).
However, neither of the above-mentioned methods are suited to the production of fine boehmite crystals for use in pigment/filler applications because the products are too coarse. Moreover, despite the fact that both methods are * Tr~de-mark . . .
., . .
. ~ , .. . . .. .
: . .
- ZO~ 54 see!ded processes, they provide relatively low yields of boe!hmite in relation to the amount of seed used, and also in relation to the high alumina content of the starting liquor.
Consequently, the liquors must be treated further, so that after separation of boehmite, the remaining alumina concentra-tions can be lowered to economical levels.
As described in copending U.S. Patent Application Serial No. 847,634, a Bayer spent liquor, i.e., a liquor g 2Ofree/A12O3 molar ratio and a low alumina content, when subjected to organics oxidation (i.e., a pro-cess for removing from the Bayer liquors organic contamin-ants present in the original bauxite used) in the presence of copper catalyst ions, can be induced to precipitate about 50~ of its alumina content as copper-containing boehmite.
This process is conducted under hydrothermal conditions (in-creased pressure and temperature) and the copper-containing boehmite is recycled as a catalyst/catalyst carrier system.
In addition, no seeding of the liquor is necessary for boehmite crystallization. Moreover, the retention time requirement (the amount of time that the liquor to be oxidized must remain with-in the autoclave) for the combined organics oxidation - boeh-mite crystallization is of the order of one hour or less.
~owever, the boehmite particles precipitated by this process are not suitable for paint, ink and filler applications because of their coarse size (5-15 microns).
As mentioned above, none of the prior art methods , Z(~ 54 for precipitating alumina can be used to produce fine boeh-mite crystals for use in a pigment/filler application. There-fore, what is needed is a novel process for the production of such boehmite crystals. The present inventor has unexpectedly found that if the carbonation of a Bayer caustic aluminate liquor or other similar Na2O- and A12O3- containing liquor is carried out in the relative absence of cationic impurities such as calcium and copper ions and if the hydrothermal boehmite crystallization is carried out under conditions of vigorous agitation, then the resulting boehmite crystals have a particle size and form that renders them well-suited for use as pigments and/or fillers in paints, papers, inks and the like. Ad-vantageously, using the method of the present invention, the boehmite is crystallized out from an organics-oxidized (i.e.
decontaminated by breakdown of organic carbon contaminants) Bayer liquor which is low in organic carbon content and hence, relatively colorless.
Therefore the present invention seeks to provide a process for the production of a novel, fine, tabular, crystal-line boehmite.
The present invention also seeks to provide novel boehmite crystals of a fine, tabular form.
The present invention further seeks to provide boehmite crystals having a particle size of between about 0.2 and 0.8 microns and essentially tabular (i.e., flat) shape.
As used herein, "tabular" is defined as flat cry-~ .. . .. . . . . .
:.. : , . . . :
' .--'-- ~ ':' ' . .
2~ ~ n ~
.
1574-1575).
The term molar ratio can be defined as follows:
(Moles Caustic in Solution)/(Moles Alumina in Solution) =
(1.645)x[g/1 Na2Ofree]/[g/1 A12O3]
In the above equation, Na2Ofree is defined as the amount of caustic present as NaOH and combined with alumina as sodium aluminate.
For example, a Bayer liquor which contains 140 g/l of free caustic (expressed as Na2Ofree) and 177 g/l alumina has a molar ratio of 1.3 using the above equation.
Alternatively, it is known that, depending upon the liquor composition, under atmospheric pressure conditions, and at temperatures of up to about 140C, crystalline boehmite can be precipitated from Bayer liquors. This is accomplished using 100 g/l of a very fine gel-type boehmite seed (such as CATAPAL*, made by CONOCO INC.), a 1.4 to 1.5 molar ratio and a retention time of 6 hours in the autoclave, as described for example in the West German Patent application of C. Misra et al., DE 3528534Al (August 8, 1985).
However, neither of the above-mentioned methods are suited to the production of fine boehmite crystals for use in pigment/filler applications because the products are too coarse. Moreover, despite the fact that both methods are * Tr~de-mark . . .
., . .
. ~ , .. . . .. .
: . .
- ZO~ 54 see!ded processes, they provide relatively low yields of boe!hmite in relation to the amount of seed used, and also in relation to the high alumina content of the starting liquor.
Consequently, the liquors must be treated further, so that after separation of boehmite, the remaining alumina concentra-tions can be lowered to economical levels.
As described in copending U.S. Patent Application Serial No. 847,634, a Bayer spent liquor, i.e., a liquor g 2Ofree/A12O3 molar ratio and a low alumina content, when subjected to organics oxidation (i.e., a pro-cess for removing from the Bayer liquors organic contamin-ants present in the original bauxite used) in the presence of copper catalyst ions, can be induced to precipitate about 50~ of its alumina content as copper-containing boehmite.
This process is conducted under hydrothermal conditions (in-creased pressure and temperature) and the copper-containing boehmite is recycled as a catalyst/catalyst carrier system.
In addition, no seeding of the liquor is necessary for boehmite crystallization. Moreover, the retention time requirement (the amount of time that the liquor to be oxidized must remain with-in the autoclave) for the combined organics oxidation - boeh-mite crystallization is of the order of one hour or less.
~owever, the boehmite particles precipitated by this process are not suitable for paint, ink and filler applications because of their coarse size (5-15 microns).
As mentioned above, none of the prior art methods , Z(~ 54 for precipitating alumina can be used to produce fine boeh-mite crystals for use in a pigment/filler application. There-fore, what is needed is a novel process for the production of such boehmite crystals. The present inventor has unexpectedly found that if the carbonation of a Bayer caustic aluminate liquor or other similar Na2O- and A12O3- containing liquor is carried out in the relative absence of cationic impurities such as calcium and copper ions and if the hydrothermal boehmite crystallization is carried out under conditions of vigorous agitation, then the resulting boehmite crystals have a particle size and form that renders them well-suited for use as pigments and/or fillers in paints, papers, inks and the like. Ad-vantageously, using the method of the present invention, the boehmite is crystallized out from an organics-oxidized (i.e.
decontaminated by breakdown of organic carbon contaminants) Bayer liquor which is low in organic carbon content and hence, relatively colorless.
Therefore the present invention seeks to provide a process for the production of a novel, fine, tabular, crystal-line boehmite.
The present invention also seeks to provide novel boehmite crystals of a fine, tabular form.
The present invention further seeks to provide boehmite crystals having a particle size of between about 0.2 and 0.8 microns and essentially tabular (i.e., flat) shape.
As used herein, "tabular" is defined as flat cry-~ .. . .. . . . . .
:.. : , . . . :
' .--'-- ~ ':' ' . .
2~ ~ n ~
.
stals, i.e., crystals having one dimension substantially smaller than the other two dimensions. Substantially smaller is defined as having one of their average height, width and length dimensions to be less than about 50~ of the other two dimensions. It should be noted that the tabular crystals can be square, diamond and hexagonal-shaped.
These and other objects of the present invention will be apparent to those of ordinary skill in the art in the light of the present description, accompanying claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-Figure 1 is a diagrammatic flow sheet of a pre-ferred embodiment of the process of the present invention.
Figure 2 is a scanning electron micrograph of boehmite product obtained in accordance with the process of the present invention at (a) 1 ~ 000 X and ~b) 40,000 X magnifi-cation.
Figure 3 is a Quantitative Image Analysis of the crystal size distribution of the boehmite product obtained in accordance with the process of the present invention.
Figure 4 is an X-ray diffractogram of the boehmite product obtained in accordance with the process of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a process for the 2~ Z54 production of fine, tabular alpha-alumina monohydrate crystals characterized by the following steps:
- adjustment of a caustic aluminate liquor at temperatures above 100C until the molar ratio of the liquor Na2Ofree/A12O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic conditions of intensive agitation in order to induce nuclea-tion of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
The molar ratio of the liquor can be adjusted by adding aluminium hydroxide or other soluble aluminium compounds to the liquor.
The present invention also provides a process for producing fine, tabular boehmite crystals. The process is carried out by contacting a Bayer process (or other similar Na2O- and A12O3- containing) liquor with an oxygen-containing gas at elevated temperature and pressure until a molar ratio of less than or equal to 1 is achieved. The oxidized liquor is then cooled, under hydrodynamic conditions of vigorous agitation, inducing nucleation and crystallization of boehmite.
The boehmite recovered is of a tabular form, preferably and of a fine size, substantially in the range of 0.2-0.8 microns).
In another aspect, the present invention provides a process for the production of fine, tabular alpha-alumina monohydrate crystals. The process comprises providing a ,: . ........ ~ , , :
.~: .. .. - : . .
~.:: , ... ' : ' ',,-:
:-: ~ . : . . . .
These and other objects of the present invention will be apparent to those of ordinary skill in the art in the light of the present description, accompanying claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-Figure 1 is a diagrammatic flow sheet of a pre-ferred embodiment of the process of the present invention.
Figure 2 is a scanning electron micrograph of boehmite product obtained in accordance with the process of the present invention at (a) 1 ~ 000 X and ~b) 40,000 X magnifi-cation.
Figure 3 is a Quantitative Image Analysis of the crystal size distribution of the boehmite product obtained in accordance with the process of the present invention.
Figure 4 is an X-ray diffractogram of the boehmite product obtained in accordance with the process of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a process for the 2~ Z54 production of fine, tabular alpha-alumina monohydrate crystals characterized by the following steps:
- adjustment of a caustic aluminate liquor at temperatures above 100C until the molar ratio of the liquor Na2Ofree/A12O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic conditions of intensive agitation in order to induce nuclea-tion of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
The molar ratio of the liquor can be adjusted by adding aluminium hydroxide or other soluble aluminium compounds to the liquor.
The present invention also provides a process for producing fine, tabular boehmite crystals. The process is carried out by contacting a Bayer process (or other similar Na2O- and A12O3- containing) liquor with an oxygen-containing gas at elevated temperature and pressure until a molar ratio of less than or equal to 1 is achieved. The oxidized liquor is then cooled, under hydrodynamic conditions of vigorous agitation, inducing nucleation and crystallization of boehmite.
The boehmite recovered is of a tabular form, preferably and of a fine size, substantially in the range of 0.2-0.8 microns).
In another aspect, the present invention provides a process for the production of fine, tabular alpha-alumina monohydrate crystals. The process comprises providing a ,: . ........ ~ , , :
.~: .. .. - : . .
~.:: , ... ' : ' ',,-:
:-: ~ . : . . . .
caustic aluminate-containing liquor having a molar ratio of Na2Ofree to A12O3 of less than or equal to one; the liquor is essentially free of cationic impurities such as calcium and copper ions (i.e. C 1 mg/l)) and is at an elevated temperature and an elevated pressure. The liquor is then cooled under conditions of vigorous agitation so that alpha-alumina mono-hydrate nucleation and crystallization occurs. The thus pre-cipitated alpha-alumina monohydrate crystals are then recovered.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, organics oxidation of a spent Bayer liquor or other Na2O/A12O3 con-taining liquor is carried out in the absence of copper ions and boehmite crystallization is carried out under hydro-dynamic conditions, e.g. in an autoclave equipped with a mechanical means for agitation. Hydrodynamic conditions are defined as vigorous agitation causing rapid movement of the liquor during the reaction. The particle size and form of the resulting product is a fine, tabular boehmite. The maximum amount of copper present in the crystals of the present in-vention is equivalent to less than 1 mg/L of copper in the oxidized solution, where the method of boehmite crystalliza-tion is homogeneous nucleation. If the tabular crystals of the present invention are used as seeds for the crystalliza-tion, then higher amounts of copper ions could be tolerated.
Copending U.S. Patent Application Serial No.
847,634 teaches that, in order to ensure the precipitation - : ~ .
:~ -.:' :: .
'~002Z5~
., of boehmite in the autoclave as the system is cooled back to conditions of atmospheric temperature and pressure, the molar ral:io of Na2Ofree/Al2O3 (i.e. K) must be lowered to at least l as a result of liquor carbonation.
A K of less than or equal to l is also preferred in the process of the present invention.
A Bayer process caustic aluminate liquor or a synthetic caustic aluminate liquor of an appropriate compo-sition is employed as the starting material for the practice of the present invention. As used herein, an appropriate liquor composition is defined as that obtained from the Bayer process following the precipitation of aluminum trihydroxide, and generally ranges between about 120 g/lt and about 150 g/lt caustic and between about 70 g/lt and about 90 g/lt alumina.
Such liquor typically contains organic carbon compounds and 20-30 g/lt Na2CO3. If the starting liquor has a high concentra-tion of Na2Ofree in relation to the A12O3 (i.e., a K of more than about one), then the concentration of Na2Ofree must be lowered in order to alter the molar ratio. In a particularly preferred embodiment of the present invention, CO2 gas is first injected into a high-K Bayer liquor. As a result of liquor carbonation, the Na2Ofree concentration is reduced (by partial neutralization of the free caustics present in this liquor), and the molar ratio, K, decreases to less than or equal to one.
The amount of CO2 gas injected is calculated on the . : ~. ::., : : . ~ :
::~ ~ ,. . . :.
- ZO(32254 basis of how much Na2Ofree must be converted to sodium car-bonate by reacting with CO2 to lower the value of K to less th~n or equal to 1. As C02 gas is introduced, small samples (e.g. 2 ml) are removed from the liquor and the pH is deter-mined. As the pH is lowered by the conversion of the free caustic to sodium carbonate, the amount of Na2Ofree can be calculated. When Na2Ofree reaches the desired concentration, C2 gas bubbling is stopped. This step is carried out at a temperature broadly ranging between about 50C and about 70C
and preferably at about 60C, in an autoclave equipped with means for mechanical agitation. The organic carbon content of the liquor is then oxidized to CO2 to provide the final car-bonation necessary to lower the K value to less than or equal to 1. The liquor is oxidized under standard oxidation con-ditions, e.g. 300C, 40 bar 2 and held at this temperature and pressure for between about 60 and 120 minutes, and preferably 90 minutes. As the autoclave is cooled down so that boehmite will precipitate out of solution, the autocalve contents are mechanically agitated preferably using a means for agitation capable of operating at between about 1,000 to 2,000 RPM.
This causes the boehmite to precipitate in the form of cry-stals of the desired size and shape in accordance with the present invention. The boehmite-containing slurry is filtered, typically under vacuum, and the solids washed with hot (i.e., 80-95C) water. The liquor remaining after solids separation can be diluted as necessary and returned to the main Bayer : .
:' : : .
:, . , ZC)0~2S4 process via a causticisation step using, for example, lime to recover caustic.
In an alternative embodiment, another oXygen-con-taining gas, such as an air/oxygen mixture, can be used as an oxidizing agent instead of oxygen gas. Assuming the same total amount of oxygen used, the oxidizing reaction should be preferably performed at higher pressures and may also re-quire longer retention times.
A flow diagram, showing typical operating conditions for the practice of a preferred embodiment of the present invention, is presented in Figure 1.
In another alternative embodiment of the present invention, aluminum hydroxide or other aluminum compounds may be added to the liquor prior to organics oxidation in order to adjust the molar ratio. If the liquor has an exceptionally high organic carbon content (relative to the excess of moles of Na2Ofree over moles of A12O3), neither injection of CO2 gas nor addition of aluminum compounds is necessary, and the liquor can be used directly. This is because sufficient CO2 will be produced upon oxidation of the organics to effect the desired neutralization degree~for the caustic. In the latter case, "exceptionally high" is defined as having at least about 20g of carbon per liter of liquor. The liquor obtained after organics oxidation will have the appropriate molar ratio (i.e., less than or equal to 1) for producing the boehmite oE the present invention. [The liquor obtained is preferably essen-.. . .
. : ~
zoo2z54 tially free of organic carbon. Essentially free is defined as having no more than about 15% of the original organic carbon during the crystallization step.] Appropriate opera-ting conditions for this embodiment are as follows: oxygen pressure, 20-40 bar, reaction temperature, 260-300C retention time, 60-120 minutes, boehmite crystallization temperature 140-150C, 1000-2000 RPM agitation and 30-60 minutes retention time for the crystallization step. The 1000 RPM agitation level is preferred. A lower agitation level limit in terms of energy input depends upon the mixing equipment used. The objective is to prevent agglomeration of the resultant boehmite crystals.
In yet another alternative embodiment, organic carbon compounds, such as those normally present in Bayer liquors, are added to reduce the Na2Ofree levels of the caustic aluminate liquor by organic carbonation. The amounts of such compounds are selected according to the composition of the liquor to be oxidized, i.e., according to the amount of Na2Ofree that has to be carbonated (1 mole of organic carbon will, when oxidized, carbonate 1 mole of Na2Ofree.) The introduction of CO2 gas to the Bayer liquor prior to organics oxidation serves two purposes. It ensures that the molar ratio, (K value), attained during organics oxidation will, in practice, be less than or equal to 1 (without having to measure the organic carbon content of the liquor), and the reaction time can be reduced.
:: . : `: I . : , .: ,., . :
-` ` '' . : :` ' . ~ . : ` -:' . ',:: : ` .- ` .
znn2254 Figure 2 is a scanning electron micrograph illus-trating a specimen of a fine crystal boehmite product obtained using the method of the present invention. The micrograph clearly shows the fineness of the boehmite product and the distinctly tabular aspect of the crystals. The crystals have several essentially flat surfaces or faces with two opposing faces having a substantially greater area than the remaining faces. By "substantially greater area" we mean at least twice the area. The crystal size distribution was measured by ~-Quantitative Image Analysis.
Quantitative Image Analysis is performed as follows:
enlarged SEM micrographs of the tabular boehmite are used to determine crystal size distribution. By using a video camera, a micrograph image is transferred to a television-type screen which is activated by a light pen, as the outline of each crystal is traced. The computer-controlled image analyzer produces a best fit for each crystal and displays an average diameter distribution for the boehmite crystals. Individual crystals within agglomerates were separated visually, while polycrystalline aggregates were treated in a similar way with individual crystals separated only where there was no obvious symmetry relationship involved. The Quantitative Image Analysis is shown in Figure 3.
The average particle size is 0.5 microns, within a size range of about 0.2 to about 0.8 microns.
Other physical and chemical properties determined ~ ~ .
- . . .
.:
: ' ' . : . . .
. , .
Z00~254 for the boehmite product are as Eollows:
Specific Surface Area 5.0 m2/g (As determined by gas adsorption) Loss-on-Ignition 15.0 Total Na2O 0.20 %
The high crystallinity of the boehmite product and the complete absence of any other forms of aluminum hydroxide was confirmed by X-ray diffraction. The diffractogram is shown in Figure 4 and the only peak observed in the region of alumina monohydrate corresponded to 100% boehmite, i.e., all of the alumina monohydrate precipitated by the present process is boehmite.
In addition, the present inventor has found that a significant amount (up to 40%) of the crystals formed have a new and unexpected hexagonal shape, which is unusual for boehmite crystals.
The present invention is further described below in specific examples which are intended to illustrate the practice of the invention without limiting its scope.
EXAMPLE
One liter of Bayer spent liquor having the following composition:
Na2Ofree 139 g/l A123 82 g/1 Organic Carbon 16.7 g/l Sodium Oxalate 2.1 s/l ,, ~ . ~ . . .
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, organics oxidation of a spent Bayer liquor or other Na2O/A12O3 con-taining liquor is carried out in the absence of copper ions and boehmite crystallization is carried out under hydro-dynamic conditions, e.g. in an autoclave equipped with a mechanical means for agitation. Hydrodynamic conditions are defined as vigorous agitation causing rapid movement of the liquor during the reaction. The particle size and form of the resulting product is a fine, tabular boehmite. The maximum amount of copper present in the crystals of the present in-vention is equivalent to less than 1 mg/L of copper in the oxidized solution, where the method of boehmite crystalliza-tion is homogeneous nucleation. If the tabular crystals of the present invention are used as seeds for the crystalliza-tion, then higher amounts of copper ions could be tolerated.
Copending U.S. Patent Application Serial No.
847,634 teaches that, in order to ensure the precipitation - : ~ .
:~ -.:' :: .
'~002Z5~
., of boehmite in the autoclave as the system is cooled back to conditions of atmospheric temperature and pressure, the molar ral:io of Na2Ofree/Al2O3 (i.e. K) must be lowered to at least l as a result of liquor carbonation.
A K of less than or equal to l is also preferred in the process of the present invention.
A Bayer process caustic aluminate liquor or a synthetic caustic aluminate liquor of an appropriate compo-sition is employed as the starting material for the practice of the present invention. As used herein, an appropriate liquor composition is defined as that obtained from the Bayer process following the precipitation of aluminum trihydroxide, and generally ranges between about 120 g/lt and about 150 g/lt caustic and between about 70 g/lt and about 90 g/lt alumina.
Such liquor typically contains organic carbon compounds and 20-30 g/lt Na2CO3. If the starting liquor has a high concentra-tion of Na2Ofree in relation to the A12O3 (i.e., a K of more than about one), then the concentration of Na2Ofree must be lowered in order to alter the molar ratio. In a particularly preferred embodiment of the present invention, CO2 gas is first injected into a high-K Bayer liquor. As a result of liquor carbonation, the Na2Ofree concentration is reduced (by partial neutralization of the free caustics present in this liquor), and the molar ratio, K, decreases to less than or equal to one.
The amount of CO2 gas injected is calculated on the . : ~. ::., : : . ~ :
::~ ~ ,. . . :.
- ZO(32254 basis of how much Na2Ofree must be converted to sodium car-bonate by reacting with CO2 to lower the value of K to less th~n or equal to 1. As C02 gas is introduced, small samples (e.g. 2 ml) are removed from the liquor and the pH is deter-mined. As the pH is lowered by the conversion of the free caustic to sodium carbonate, the amount of Na2Ofree can be calculated. When Na2Ofree reaches the desired concentration, C2 gas bubbling is stopped. This step is carried out at a temperature broadly ranging between about 50C and about 70C
and preferably at about 60C, in an autoclave equipped with means for mechanical agitation. The organic carbon content of the liquor is then oxidized to CO2 to provide the final car-bonation necessary to lower the K value to less than or equal to 1. The liquor is oxidized under standard oxidation con-ditions, e.g. 300C, 40 bar 2 and held at this temperature and pressure for between about 60 and 120 minutes, and preferably 90 minutes. As the autoclave is cooled down so that boehmite will precipitate out of solution, the autocalve contents are mechanically agitated preferably using a means for agitation capable of operating at between about 1,000 to 2,000 RPM.
This causes the boehmite to precipitate in the form of cry-stals of the desired size and shape in accordance with the present invention. The boehmite-containing slurry is filtered, typically under vacuum, and the solids washed with hot (i.e., 80-95C) water. The liquor remaining after solids separation can be diluted as necessary and returned to the main Bayer : .
:' : : .
:, . , ZC)0~2S4 process via a causticisation step using, for example, lime to recover caustic.
In an alternative embodiment, another oXygen-con-taining gas, such as an air/oxygen mixture, can be used as an oxidizing agent instead of oxygen gas. Assuming the same total amount of oxygen used, the oxidizing reaction should be preferably performed at higher pressures and may also re-quire longer retention times.
A flow diagram, showing typical operating conditions for the practice of a preferred embodiment of the present invention, is presented in Figure 1.
In another alternative embodiment of the present invention, aluminum hydroxide or other aluminum compounds may be added to the liquor prior to organics oxidation in order to adjust the molar ratio. If the liquor has an exceptionally high organic carbon content (relative to the excess of moles of Na2Ofree over moles of A12O3), neither injection of CO2 gas nor addition of aluminum compounds is necessary, and the liquor can be used directly. This is because sufficient CO2 will be produced upon oxidation of the organics to effect the desired neutralization degree~for the caustic. In the latter case, "exceptionally high" is defined as having at least about 20g of carbon per liter of liquor. The liquor obtained after organics oxidation will have the appropriate molar ratio (i.e., less than or equal to 1) for producing the boehmite oE the present invention. [The liquor obtained is preferably essen-.. . .
. : ~
zoo2z54 tially free of organic carbon. Essentially free is defined as having no more than about 15% of the original organic carbon during the crystallization step.] Appropriate opera-ting conditions for this embodiment are as follows: oxygen pressure, 20-40 bar, reaction temperature, 260-300C retention time, 60-120 minutes, boehmite crystallization temperature 140-150C, 1000-2000 RPM agitation and 30-60 minutes retention time for the crystallization step. The 1000 RPM agitation level is preferred. A lower agitation level limit in terms of energy input depends upon the mixing equipment used. The objective is to prevent agglomeration of the resultant boehmite crystals.
In yet another alternative embodiment, organic carbon compounds, such as those normally present in Bayer liquors, are added to reduce the Na2Ofree levels of the caustic aluminate liquor by organic carbonation. The amounts of such compounds are selected according to the composition of the liquor to be oxidized, i.e., according to the amount of Na2Ofree that has to be carbonated (1 mole of organic carbon will, when oxidized, carbonate 1 mole of Na2Ofree.) The introduction of CO2 gas to the Bayer liquor prior to organics oxidation serves two purposes. It ensures that the molar ratio, (K value), attained during organics oxidation will, in practice, be less than or equal to 1 (without having to measure the organic carbon content of the liquor), and the reaction time can be reduced.
:: . : `: I . : , .: ,., . :
-` ` '' . : :` ' . ~ . : ` -:' . ',:: : ` .- ` .
znn2254 Figure 2 is a scanning electron micrograph illus-trating a specimen of a fine crystal boehmite product obtained using the method of the present invention. The micrograph clearly shows the fineness of the boehmite product and the distinctly tabular aspect of the crystals. The crystals have several essentially flat surfaces or faces with two opposing faces having a substantially greater area than the remaining faces. By "substantially greater area" we mean at least twice the area. The crystal size distribution was measured by ~-Quantitative Image Analysis.
Quantitative Image Analysis is performed as follows:
enlarged SEM micrographs of the tabular boehmite are used to determine crystal size distribution. By using a video camera, a micrograph image is transferred to a television-type screen which is activated by a light pen, as the outline of each crystal is traced. The computer-controlled image analyzer produces a best fit for each crystal and displays an average diameter distribution for the boehmite crystals. Individual crystals within agglomerates were separated visually, while polycrystalline aggregates were treated in a similar way with individual crystals separated only where there was no obvious symmetry relationship involved. The Quantitative Image Analysis is shown in Figure 3.
The average particle size is 0.5 microns, within a size range of about 0.2 to about 0.8 microns.
Other physical and chemical properties determined ~ ~ .
- . . .
.:
: ' ' . : . . .
. , .
Z00~254 for the boehmite product are as Eollows:
Specific Surface Area 5.0 m2/g (As determined by gas adsorption) Loss-on-Ignition 15.0 Total Na2O 0.20 %
The high crystallinity of the boehmite product and the complete absence of any other forms of aluminum hydroxide was confirmed by X-ray diffraction. The diffractogram is shown in Figure 4 and the only peak observed in the region of alumina monohydrate corresponded to 100% boehmite, i.e., all of the alumina monohydrate precipitated by the present process is boehmite.
In addition, the present inventor has found that a significant amount (up to 40%) of the crystals formed have a new and unexpected hexagonal shape, which is unusual for boehmite crystals.
The present invention is further described below in specific examples which are intended to illustrate the practice of the invention without limiting its scope.
EXAMPLE
One liter of Bayer spent liquor having the following composition:
Na2Ofree 139 g/l A123 82 g/1 Organic Carbon 16.7 g/l Sodium Oxalate 2.1 s/l ,, ~ . ~ . . .
Calcium ~ 1 mg/l Copper ~ 1 mg/l was injected with CO2 gas under conditions of atmospheric temperature and pressure in a 3 liter capacity nickel alloy (Inconel) autoclave equipped with a mechanical agitator capable of operating at up to 2000 RPM. As a result of liquor carbonation, the Na2O,~ee concentration was reduced from 139 to 112 g/l. Oxygen gas was then introduced into the auto-clave up to a pressure of 40 bar (as measured at 25C) and the temperature of the liquor in the autoclave was raised to 300C
and held at this temperature for 90 minutes. Thereafter, the composition of the oxidized liquor in the autoclave was:
Na2free 46 g/l A123 82 g/l Organic Carbon 3.4 g/l Sodium Oxalate 4.9 g/1 The organics oxidation efficiency (i.e., the % reduction in organic carbon content) was thus approximately 80~.
The numerical value of K for the oxidized liquor of the above example was 0.92 (i.e., (46/82) x 1.645). Upon cooling to about 90C, which took 30-60 minutes, boehmite precipitated out of the oxidized liquor during the cooling step of the process in an amount of 43 g/l (expressed as alumina). The boehmite-containing slurry was filtered and the solids were washed with hot water. The liquor obtained after solids separation was diluted with water and returned .. . .
Z~02:~54 - 15 - 23828-Sl to the main Bayer process after an alkaline treatment step using lime in order to recover caustic, as is well known in the art.
The present invention has been described above with reference to preferred embodiments. It would be obvious to those of ordinary skill in the art that many additions, de-letions, ox substitutions can be made without departing from the spirit and scope of the invention as claimed below.
. . , . :,: - " . . - .: ~
. . . ~, .
and held at this temperature for 90 minutes. Thereafter, the composition of the oxidized liquor in the autoclave was:
Na2free 46 g/l A123 82 g/l Organic Carbon 3.4 g/l Sodium Oxalate 4.9 g/1 The organics oxidation efficiency (i.e., the % reduction in organic carbon content) was thus approximately 80~.
The numerical value of K for the oxidized liquor of the above example was 0.92 (i.e., (46/82) x 1.645). Upon cooling to about 90C, which took 30-60 minutes, boehmite precipitated out of the oxidized liquor during the cooling step of the process in an amount of 43 g/l (expressed as alumina). The boehmite-containing slurry was filtered and the solids were washed with hot water. The liquor obtained after solids separation was diluted with water and returned .. . .
Z~02:~54 - 15 - 23828-Sl to the main Bayer process after an alkaline treatment step using lime in order to recover caustic, as is well known in the art.
The present invention has been described above with reference to preferred embodiments. It would be obvious to those of ordinary skill in the art that many additions, de-letions, ox substitutions can be made without departing from the spirit and scope of the invention as claimed below.
. . , . :,: - " . . - .: ~
. . . ~, .
Claims (15)
1. A process for the production of fine, tabular alpha-alumina monohydrate crystals characterized by the following steps:
- adjustment of a caustic aluminate liquor at temperatures above 100°C until the molar ratio of the liquor Na2Ofree/Al2O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic con-ditions of intensive agitation in order to induce nucleation of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
- adjustment of a caustic aluminate liquor at temperatures above 100°C until the molar ratio of the liquor Na2Ofree/Al2O3 is less than or equal to 1, - cooling of this liquor under the hydrodynamic con-ditions of intensive agitation in order to induce nucleation of the alpha-alumina monohydrate, and - separation of an alpha-alumina monohydrate product into a fine size and tabular form.
2. A process according to claim 1, wherein the molar ratio of the liquor is adjusted by adding aluminium hydroxide or other soluble aluminium compounds to the liquor.
3. A process according to one of the preceding claims, wherein the molar ratio of the liquor is achieved by means of gas treatment with oxygen and/or carbon dioxide.
4. A process according to one of the preceding claims, wherein the molar ratio of the liquor is achieved by adding organ-ic carbon compounds to the liquor prior to oxidation.
5. A process according to one of the preceding claims, wherein a Bayer process liquor is employed as the starting materi-al, the organic carbon content of this liquor being sufficient to achieve a molar ratio of less than or equal to 1.
6. A process according to one of the preceding claims, wherein the amount of organic carbon in the Bayer liquor is great-er than or equal to 20 g/l.
7. A process according to one of the preceding claims, wherein adjustment of the molar ratio is made possible by the for-mation of CO2 in the liquor.
8. A process according to one of the preceding claims, wherein the content of cationic impurities such a calcium or cop-per ions in the liquor is less than 1 mg/l.
9. A process according to one of the preceding claims, wherein the temperature at which the molar ratio is adjusted is in the range of about l50°C to about 300°C.
10. A process according to one of the preceding claims, wherein production of the liquor with a molar ratio of less than or equal to one is carried out in that the concentration of organ-ic carbon in this liquor with a molar ratio of more than 1 is in-creased and O2 or CO2 gas is subsequently introduced until oxidation of the organic carbon under CO2 formation takes place, this CO2 reducing the concentration of Na2Ofree and thereby producing a liquor with a molar ratio of less than or equal to 1 and essentially free of organic carbon.
11. A process according to one of the preceding claims, wherein a molar ratio of less than or equal to 1 is achieved, starting with a Bayer liquor with an organic carbon content at least in excess of the amount which reacts a corresponding amount of free alkali to carbonate following its oxidation and thereby reduces the molar ratio to less than or equal to 1.
12. A process according to one of the preceding claims, wherein oxidation of the organic carbon is carried out with oxygen-containing gas at an elevated temperature between about 260° to about 300°C and increased oxygen pressures between about 20 to about 150 bar during a retention time that is sufficient for oxidation of the organic carbon so that the liquor does not con-tain more than about 15% of the organic carbon during crystalliza-tion.
13. Fine, tabular alpha-alumina monohydrate crystals whose average crystal diameter is 0.4 µm with 40% of these crys-tals in hexagonal shape.
14. Crystals according to claim 8, wherein more than 90%
have a diameter between 0.2 and 0.8 µm.
have a diameter between 0.2 and 0.8 µm.
15. Crystals according to one of the claims 13 and 14, wherein one of the crystal dimensions of height, width and length is less than about 50% of the smaller of the other two dimensions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP88118343A EP0366825A1 (en) | 1988-11-04 | 1988-11-04 | Process for the preparation of fine platelike boehmite |
| EP88118343.8 | 1988-11-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2002254A1 true CA2002254A1 (en) | 1990-05-04 |
Family
ID=8199519
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002002254A Abandoned CA2002254A1 (en) | 1988-11-04 | 1989-11-06 | Process for the production of fine tabular alumina monohydrate |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0366825A1 (en) |
| JP (1) | JPH02243512A (en) |
| CA (1) | CA2002254A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6475601B1 (en) | 1995-04-10 | 2002-11-05 | Canon Kabushiki Kaisha | Printing paper, and ink-jet printing process using the same |
| US7569614B2 (en) | 2003-03-14 | 2009-08-04 | Nissan Chemical Industries, Ltd. | Process for producing acidic aqueous alumina sol |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5171631A (en) * | 1990-07-19 | 1992-12-15 | Aluminum Company Of America | Spacer/extender for titanium dioxide in pigment systems for coatings |
| GR1002926B (en) * | 1997-06-24 | 1998-06-16 | Universite Libre De Bruxelles Service D'exploitation Des Mines... | PROCESS FOR PRODUCTION OF MONOHYDRATE ALUMINA WITH PRESIPITATION FROM SUPERSATURATED ALUMINATE SOLUTIONS AT TEMPERATURES LOWER THAN 100 o C |
| ATE547380T1 (en) * | 2002-06-25 | 2012-03-15 | Univ Aalborg | METHOD FOR PRODUCING A PRODUCT HAVING A SUB-MICRON PRIMARY PARTICLE SIZE AND APPARATUS FOR APPLYING THE METHOD |
| CN113213515A (en) * | 2021-05-10 | 2021-08-06 | 中国铝业股份有限公司 | Method and equipment for reducing carbon alkali |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO135059C (en) * | 1975-04-16 | 1977-02-02 | Norsk Hydro As | |
| CA1207630A (en) * | 1983-12-22 | 1986-07-15 | Alan Pearson | Continuous process for neutralization of aluminate solution to form gels and apparatus therefor |
| DE3512404A1 (en) * | 1985-04-04 | 1986-10-09 | Vereinigte Aluminium-Werke AG, 1000 Berlin und 5300 Bonn | METHOD FOR REDUCING THE ORGANIC COMPONENTS IN ALUMINATE LIQUIDS |
| US4822593A (en) * | 1986-12-11 | 1989-04-18 | Aluminum Company Of America | Control of form of crystal precipitation of aluminum hydroxide using cosolvents and varying caustic concentration |
-
1988
- 1988-11-04 EP EP88118343A patent/EP0366825A1/en not_active Withdrawn
-
1989
- 1989-11-04 JP JP1286053A patent/JPH02243512A/en active Pending
- 1989-11-06 CA CA002002254A patent/CA2002254A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6475601B1 (en) | 1995-04-10 | 2002-11-05 | Canon Kabushiki Kaisha | Printing paper, and ink-jet printing process using the same |
| US7569614B2 (en) | 2003-03-14 | 2009-08-04 | Nissan Chemical Industries, Ltd. | Process for producing acidic aqueous alumina sol |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02243512A (en) | 1990-09-27 |
| EP0366825A1 (en) | 1990-05-09 |
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