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US3980753A
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Industrial process of preparing magnesia of high purity
Assignee: Veitscher Magnesitwerke AG
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Filing: 1974-11-29
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Granted: 1976-09-14
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Expires: 1994-11-29
Abstract
Abstract Magnesia of very high purity is produced industrially from a magnesite waste material wherein impurities are present in such amounts that the weight ratio of the precipitable hydroxide ions, calculated as the sum of Fe 2 O 3 + Al 2 O 3 + Cr 2 O 3 + Mn 3 O 4 to the sum of SiO 2 + TiO 2 + B 2 O 3 , is at least 1 : 3. The starting material is dissolved in hydrochloric acid of 15-32% concentration, the impurities are precipitated by adjusting the pH of the acidic solution to 4 - 9, and the purified magnesium chloride solution is thermally decomposed into magnesia and hydrochloric acid gas, the latter being recycled to form the hydrochloric acid of the stated concentration for dissolving the starting material.
Inventors
- 👤 Michael Grill
- 👤 Georg Bouvier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:02
CPC Classifications
C; C01; C01F; C01F5/00; C01F5/26; C01F5/30; C01F5/02; C01F5/06; C01F5/10; C01P; C01P2006/00; C01P2006/80
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
338 words
An industrial process of preparing magnesia containing more than 98% MgO and less than 0.1% each of the oxides of Fe, Al, Cr, Mn, Si, Ti, Na, K, and B, all percentage values being by weight, which comprises: 1. dissolving a starting material at a first temperature of more than 70° in an amount of aqueous hydrochloric acid sufficient to produce an acidic solution, a. said starting material essentially consisting of magnesium carbonate, magnesium oxide, magnesium hydroxide, or mixtures thereof, and containing, as impurities, at least one compound of members of a first group consisting of iron, aluminum, chromium, and manganese, and at least one compound of members of a second group consisting of silicon, titanium, and boron, b. the starting material being treated until the ratio in said solution of the combined weight of the compounds of said first group, calculated as Fe 2 O 3+ Al 2 O 3+ Cr 2 O 3+ Mn 3 O+ 4 to the combined weight of the compounds of said second group, calculated as SiO 2+ TiO 2+ B 2 O 3 , is changed to at least 1 : 3, and c. the concentration of said hydrochloric acid being 15% to 32% by weight, 2. adding to said acidic solution a magnesium or calcium compound sufficiently alkaline to raise the pH of said solution to the range of 4 to 9 and to substantially completely precipitate the compounds of members of said first group as hydroxides, the compounds of members of said second group being coprecipitated therewith; 3. separating the precipitate from the residual purified magnesium chloride solution; 4. heating said solution to a second temperature between about 400°C and 900°C, whereby the magnesium chloride therein is decomposed in the presence of water to magnesia and gaseous hydrochloric acid; 5. recovering said magnesia; 6. converting said gaseous hydrochloric acid to aqueous hydrochloric acid having said concentration of 15% to 32% by weight, and 7. dissolving an additional amount of said starting material in said last mentioned aqueous hydrochloric acid.
Claim 2
Dependent Claim
338 words
An industrial process of preparing magnesia containing more than 98% MgO and less than 0.1% each of the oxides of Fe, Al, Cr, Mn, Si, Ti, Na, K, and B, all percentage values being by weight, which comprises: 1. dissolving a starting material at a first temperature of more than 70° in an amount of aqueous hydrochloric acid sufficient to produce an acidic solution, a. said starting material essentially consisting of magnesium carbonate, magnesium oxide, magnesium hydroxide, or mixtures thereof, and containing, as impurities, at least one compound of members of a first group consisting of iron, aluminum, chromium, and manganese, and at least one compound of members of a second group consisting of silicon, titanium, and boron, b. the starting material being treated until the ratio in said solution of the combined weight of the compounds of said first group, calculated as Fe 2 O 3+ Al 2 O 3+ Cr 2 O 3+ Mn 3 O+ 4 to the combined weight of the compounds of said second group, calculated as SiO 2+ TiO 2+ B 2 O 3 , is changed to at least 1 : 3, and c. the concentration of said hydrochloric acid being 15% to 32% by weight, 2. adding to said acidic solution a magnesium or calcium compound sufficiently alkaline to raise the pH of said solution to the range of 4 to 9 and to substantially completely precipitate the compounds of members of said first group as hydroxides, the compounds of members of said second group being coprecipitated therewith; 3. separating the precipitate from the residual purified magnesium chloride solution; 4. heating said solution to a second temperature between about 400°C and 900°C, whereby the magnesium chloride therein is decomposed in the presence of water to magnesia and gaseous hydrochloric acid; 5. recovering said magnesia; 6. converting said gaseous hydrochloric acid to aqueous hydrochloric acid having said concentration of 15% to 32% by weight, and 7. dissolving an additional amount of said starting material in said last mentioned aqueous hydrochloric acid.
Claim 3
Dependent Claim
49 words
The industrial process of claim 1, wherein the starting material is treated until weight ratio of said Fe 2 O 3+ Al 2 O 3+ Cr 2 O 3+ Mn 3 O 4 to said SiO 2+ TiO 2+ B 2 O 3 is greater than 1 : 1.
Claim 4
Dependent Claim
15 words
The industrial process of claim 1, wherein said concentration is 18 to 22%, by weight.
Claim 5
Dependent Claim
14 words
The industrial process of claim 1, wherein said raised pH is 6 to 8.
Claim 6
Dependent Claim
15 words
The industrial process of claim 3, wherein said second temperature is about 550°C to 750°C.
Claim 7
Dependent Claim
20 words
The industrial process of claim 3, wherein the starting material is particulate and has a grain size below 3 mm.
Claim 8
Dependent Claim
15 words
The industrial process of claim 3, wherein the alkaline compound is an oxide or hydroxide.
Claim 9
Dependent Claim
47 words
The industrial process of claim 1, wherein said acidic solution contains divalent manganese as an impurity, and an oxidizing agent is added to said solution no later than during the adding of said alkaline compound in an amount sufficient to convert said divalent manganese to tetravalent manganese.
Claim 10
Dependent Claim
13 words
The industrial process of claim 8, wherein the oxidizing agent is elemental chlorine.
Claim 11
Dependent Claim
15 words
The industrial process of claim 1, wherein the starting material is a magnesite waste material.
Claim 12
Dependent Claim
57 words
The industrial process of claim 1, wherein said purified magnesium chloride solution contains calcium ions, and solid, pure magnesium sulfate is added to said magnesium chloride solution at a temperature between about 20° and 70°C and at a pH of 1 to 4 in an amount sufficient to substantially completely precipitate said calcium ions as calcium sulfate.
Claim 13
Dependent Claim
35 words
The industrial process of claim 1, wherein said purified magnesium chloride solution contains calcium ions whereby the recovered magnesium oxide contains calcium chloride, and leaching said calcium chloride from said recovered magnesium oxide with water.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-09-14 | 1980-03-15 | 1980-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-14 | 1984-03-15 | 1984-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-14 | 1988-03-15 | 1988-09-14 | $7700.00 | Window Closed / Lapsed |