Process for the production of large boehmite particles
AssigneeVereinigte Aluminium-Werke Aktiengesellschaft
InventorNeil Brown
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Abstract
A process for the production of large boehmite crystal aggregates, useful for soft polishing applications is provided herein. A caustic aluminate liquor is contacted with an oxygen-containing gas at elevated temperatures and pressures in the presence of about 1-50 mg/L of copper ions. The liquor is oxidized until a molar ratio of Na.sub.2 O.sub.free to Al.sub.2 O.sub.3 of less than or equal to 1 is achieved, and the oxidized liquor is cooled under quiescent conditions of little or no agitation which causes the crystallization and precipitation or novel large boehmite particles.
Claims22
A process for the production of alpha-alumina monohydrate aggregates comprising the steps of:
- contacting a caustic aluminate-containing liquor held under a pressure of between about 20 bar and about 150 bar O.sub.2, at a temperature of between about 120.degree. C. and 300.degree. C. and in the presence of an amount of cooper ions from about 1 to about 50 mg/l with an oxygen-containing gas to adjust the molar ratio of Na.sub.2 O.sub.free to Al.sub.2 O.sub.3 of the oxidized liquor to <1;
- cooling said oxidized liquor without any agitation to induce nucleation of alpha-alumina monohydrate particles having a particle size between about 20 and about 200 microns and containing between about 0.001% and 0.1% copper;
- and
- recovering said alpha-alumina monohydrate particles in aggregate particle form.
An alpha-alumina monohydrate crystalline aggregate comprising non-oriented crystal platelets of alpha-alumina monohydrate and form about 0.001 to about 0.1% of copper, said crystal platelets forming an open structure of low bulk density of less than 200 kg per m.sup.3 wherein said alpha-alumina monohydrate crystalline aggregate collapses under applied pressure to individual crystal platelets during use of said alpha-alumina monohydrate-crystalline aggregate in a polishing application.
An alpha-alumina monohydrate aggregate comprising alpha-alumina monohydrate crystals platelets containing 0.001-0.1% copper, the longest dimension of said crystals platelets being between about 5 and about 25 microns.
An alpha-alumina monohydrate aggregate comprising a crystal lattice of alpha-alumina monohydrate, said crystal lattice containing aluminum hydroxide layers and copper ranging between about 0.001 to about 0.1%, said copper located between the aluminum hydroxide layers in the crystal lattice.
An alpha-alumina monohydrate alpha-alumina monohydrate aggregate of between 100 and 200 microns in diameter, said aggregate comprising an interlocking network of approximately 100 crystal platelets containing alpha-alumina monohydrate, and 0.001 to 0.1% of copper, each of said crystals platelets having a diameter of between about 5 microns and about 25 microns.
A process for the production of alpha-alumina monohydrate aggregates useful in soft polishing applications which comprises the steps of:
- adjusting a caustic aluminate liquor containing from about 1 to 50 mg/l of copper ions to a molar ratio of Na.sub.2 O.sub.free to Al.sub.2 O.sub.3 of .ltoreq.to 1;
- subjecting said caustic aluminate liquor to a temperature of at least about 150.degree. C. and a pressure of between about 20 bar and about 150 bar;
- cooling said liquor under quiescent conditions to precipitate said alpha-alumina monohydrate aggregates, and recovering said alpha-alumina monohydrate aggregates, wherein said alpha-alumina aggregates contain between about 0.001 to 0.1% copper and comprise crystal platelets having a diameter of between about 5 and about 25 microns.
Alpha-alumina monohydrate crystal aggregate particles comprising a crystal lattice of alpha-alumina monohydrate, said crystal lattice containing aluminum hydroxide layers and between about 0.001 to about 0.1% of cooper, based on said alpha-alumina monohydrate and said alpha-alumina monohydrate having an average size within the range of about 20 to about 200 microns.
Alpha-alumina monohydrate crystal aggregate particles comprising non-oriented crystal platelets of alpha-alumina monohydrate, said crystals platelets ranging between about 5 and about 25 microns in diameter and forming an open structure having a bulk density below about 200 kg/m.sup.3, said alpha-alumina monohydrate crystal aggregrate particles collapsing upon application of such pressure to individual as is normally applied during soft polishing applications.
Dependencies are inferred from the claim text.