Synthetic hydrotalcite

Abstract

Disclosed is a method for producing hydrotalcite in high yield including reacting activated magnesia with an aqueous solution containing aluminate, carbonate, and hydroxyl ions. The .[.method further includes a first step of.]. .Iadd.activated magnesia is produced by .Iaddend.heating magnesium carbonate or magnesium hydroxide to a temperature between about 500°-900° C. .[.to form activated magnesia or magnesium oxide..]. The method is suited to producing synthetic hydrotalcite from industrial Bayer liquor.

What is claimed is: 
     
       1. A method of producing hydrotalcite, comprising: (a) heating magnesium carbonate or magnesium hydroxide to a temperature between about 500°-900° C. to form activated magnesia; and   (b) reacting activated magnesia with an aqueous solution of aluminate, carbonate, and hydroxyl ions at a pH above about 13 to form hydrotalcite at a conversion yield greater than about 75%.   
     
     
       2. A method as set forth in claim 1 wherein said solution comprises a Bayer liquor. 
     
     
       3. A method as set forth in claim 1 wherein said reacting includes heating to a temperature of at least about 80° C. at ambient pressure. 
     
     
       4. A method as set forth in claim 1, said first step comprising heating magnesium carbonate or magnesium hydroxide to a temperature between about 550°-650° C. to form said activated magnesia. 
     
     
       5. A method as set forth in claim 4 wherein said magnesium carbonate or magnesium hydroxide is heated to a temperature between about 550°-650° C. for a period of about 30 to 120 minutes. 
     
     
       6. A method as set forth in claim 1 wherein said aqueous solution containing ions of aluminate, carbonate, and hydroxyl comprises about 120-250 grams/liter NaOH (expressed as Na 2  CO 3 ), about 20-100 grams/liter NaCO 3 , and about 50.150 grams/liter Al 2  O 3 . 
     
     
       7. A method as set forth in claim 6 wherein about 5-25 grams/liter activated magnesia is added to said aqueous solution. 
     
     
       8. A method of producing a material having a powder X-ray diffraction pattern of the mineral hydrotalcite comprising: (a) heating magnesium carbonate or magnesium hydroxide to a temperature between about 500°-900° C. to form activated magnesia; and   (b) reacting said activated magnesia with an aqueous solution of aluminate, carbonate, and hydroxyl ions at a pH above 13 to from hydrotalcite at a conversion yield greater than about 75%.   
     
     
       9. A method as set forth in claim 8 wherein said aqueous solution comprises an industrial Bayer liquor. 
     
     
       10. A method as set forth in claim 9 wherein said reacting comprises heating to a temperature of at least about 80° C. at atmospheric pressure. 
     
     
       11. A method as set forth in claim 10 said first step comprising heating magnesium carbonate or magnesium hydroxide to a temperature between about 550°-650°C. to form said activated magnesia. 
     
     
       12. A method as set forth in claim 11 further comprising recovering said hydrotalcite in dried form. .Iadd. 
     
     
       13.  A method of producing hydrotalcite comprising: reacting activated magnesia produced by heating magnesium carbonate or magnesium hydroxide to between about 500°-900° C. with an aqueous solution containing aluminate, carbonate and hydroxyl ions at a pH above about 13 to form hydrotalcite at a conversion yield greater than about 75%. .Iaddend. .Iadd.14. A method as set forth in claim 13 wherein said solution comprises a Bayer liquor. .Iaddend. .Iadd.15. A method as set forth in claim 13 wherein said reacting includes heating to a temperature of at least about 80° C. at ambient pressure. .Iaddend. .Iadd.16. A method as set forth in claim 13 wherein said magnesium carbonate or magnesium hydroxide is produced by heating to a temperature between about 550°-650° C. to form said activated magnesia. .Iaddend. .Iadd.17. A method as set forth in claim 16 wherein said magnesium carbonate or magnesium hydroxide is produced by heating to a temperature between about 550°-650° C. for a period of about   
     
     
        30 to 120 minutes. .Iaddend. .Iadd.18.  A method of producing a material having a powder X-ray diffraction pattern containing the mineral hydrotalcite comprising: reacting activated magnesia produced by heating magnesium carbonate or magnesium hydroxide to a temperature between about 500°-900°  C. with an aqueous solution of aluminate, carbonate, and hydroxyl ions at a pH above about 13 to form hydrotalcite at a conversion yield greater than about 75%. .Iaddend. .Iadd.19. A method as set forth in claim 18 wherein said aqueous solution comprises an industrial Bayer liquor. .Iaddend. .Iadd.20. A method as set forth in claim 19 wherein said reacting comprises heating to a temperature of at least about 80° C. at atmospheric pressure. .Iaddend. .Iadd.21. A method as set forth in claim 20 wherein said magnesium carbonate or magnesium hydroxide is produced by heating to a temperature between about 550°-650° C. to form said activated magnesia. .Iaddend. .Iadd.22. A method as set forth in claim 18 further comprising recovering said hydrotalcite in dried   
     
     
        form. .Iaddend. .Iadd.23.  A method of producing hydrotalcite comprising reacting activated magnesia produced by heating magnesium carbonate or magnesium hydroxide to between about 500° and 900° C. with an aqueous solution containing aluminate, carbonate and hydroxyl ions to form hydrotalcite at a conversion yield greater than about 75%. .Iaddend. .Iadd.24. A method as set forth in claim 23 wherein about 5.25 grams of activated magnesia is added per liter of aqueous solution to said aqueous solution. .Iaddend. .Iadd.25. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 120 to 250 grams per liter of NaOH (expressed as Na 2  CO 3 ). .Iaddend. .Iadd.26. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 20 to 100 grams per liter of Na 2  CO 3 . .Iaddend. .Iadd.27. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 50 to 150 grams per liter of Al 2  O 3 . .Iaddend. .Iadd.28. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 120 to 250 grams per liter of NaOH (expressed as Na 2  CO 3 ) and about 20 to 100 grams per liter of Na 2  CO 3 . 
     
     
        .Iaddend. .Iadd.29.  A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 20 to 100 grams per liter of Na 2  CO 3  about 50 to 150 grams per liter of Al 2  O 3 . .Iaddend. .Iadd.30. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 120 to 250 grams per liter of NaOH (expressed as Na 2  CO 3 ) and about 50 to 150 grams per liter of Al 2  O 3 . .Iaddend. .Iadd.31. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises about 120 to 250 grams per liter of NaOH (expressed as Na 2  CO 3 ), about 20 to 100 grams per liter of Na 2  CO 3  about 50 to 150 grams per liter of Al 2  O 3 . .Iaddend. .Iadd.32. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises up to about 100 grams per liter of Na 2  CO 3 . .Iaddend. .Iadd.33. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises up to about 150 grams per liter of Al 2  O 3 . .Iaddend. .Iadd.34. A method as set forth in claim 23 wherein said aqueous solution containing ions of aluminate, carbonate and hydroxyl ions comprises up to 
     
     
        about 250 grams per liter of NaOH. .Iaddend. .Iadd.35.  A method as set forth in claim 23 wherein at least 5 grams of activated magnesia is added per liter of said aqueous solution. .Iaddend.