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1. WO2020156891 - PROCÉDÉ DE PRÉPARATION D'ALUMINE ALPHA DE GRANDE SURFACE ET SON UTILISATION

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

Claims

1. Process for converting g-AI00H·cH20 with x in the range of 0 to 0.7, more preferably in the range of 0.1 to 0.33, into nanoparticulate alpha alumina having particle sizes in the range of 1 to 50 nm and a high specific BET surface area of at least 90 m2/g, characterized by subjecting said g-AI00H·cH20 to a milling process in a ball mill with a milling jar and balls in a weight ratio of balls to said g-AI00H·cH20 of 1 to 200, preferably 5 to 100, in a temperature range below the conversion temperature of nanocrystalline g-AI00H·cH20 to g-AI203, preferably in a temperature range of 10 to 200°C and for a period of time of 1 to 10, preferably up to 20 hours.

2. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to claim 1 , wherein a vibration mill or a planetary mill is used as ball mill or other milling principle capable of bringing this phase change.

3. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to claim 1 or 2 wherein the balls are made of WC or hardened steel.

4. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to claim 1 , 2 or 3, wherein the milling period is 1 to 20 hours.

5. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of the preceding claims wherein a lower limit of the water content of g- AI00H XH20 is given with x ³ 0, or preferred with x ³ 0.1 , and an upper limit is given with x £ 0.67, preferably x £ 0.5, and more preferably x £ 0.33.

6. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of the preceding claims wherein an additional water content (xH20) in the g- AIOOH is below 20 wt.-% with 0 £ x < 0.67, preferably below 15 wt.-% with 0.1 £ x < 0.5), and more preferably below 10 with wt.-% 0.1 £ x < 0.33.

7. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of the preceding claims wherein the milling product is additionally comprising alpha AIOOH, optionally in a weight ratio of up to 30 wt.-% of the total amount of nanoparticulate alpha alumina and alpha AIOOH.

8. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of the preceding claims wherein the obtained milling product is subjected to a heat treatment at temperature in a range between 500-600°C.

9. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of the preceding claims wherein milling is performed upon addition of a metal and/or metal compound wherein the metal is selected from transition metals, main group metals or mixtures thereof.

10. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to claim 9 wherein the metal or metal compound is used in particulate form.

11. Process for converting g-AI00H·cH20 into nanoparticulate alpha alumina according to any of preceding claim 9 or 10 wherein the metal compound is selected from halides, pseudohalides, acid salts, nitrates, oxides.

12. High-surface area nanoparticulate alpha alumina, having a BET surface area of at least 90 m2/g, preferably at least 100 m2/g, more preferably at least 120 m2/g, and even more preferably at least 130 m2/g, and having a particle size in the range of 1 to 50 nm, preferably in the range of 1 to 30 nm, measured by TEM, obtainable by a process according to any of claims 1 to 10.

13. High-surface area nanoparticulate alpha alumina, obtainable by a process according to any of claim 9 to 11 , having a metal content of up to 20% by weight calculated on the total amount of the loaded alumina.

14. Use of the high surface area nanoparticulate alpha alumina as claimed in any of claims 12 or 13 as catalyst or catalyst support for metal catalysts or in ceramics applications.