Boehmitic aluminas and high-temperature stable, high-porosity, pure-phase aluminium oxides obtained therefrom

Abstract

This invention relates to crystalline boehmitic aluminas the crystallites of which exhibit unusual dimensional differences in the space directions 020 and 120. This invention further relates to a method for preparing such aluminas and the follow-up products obtained therefrom by calcination.

1 - 12 . (cancelled)  
     
     
         13 . A composition comprising a crystalline boehmitic alumina having a crystallite size that, determined on the 020 reflex in nm, is larger than the measured crystallite size determined on the 120 reflex reduced by 1.5 nm.  
     
     
         14 . The composition of  claim 13 , characterized in that the crystallite size determined on the 020 reflex in nm is larger than the measured crystallite size determined on the 120 reflex reduced by 0.5 nm.  
     
     
         15 . The composition of  claim 14 , characterized in that the crystallite size determined on the 020 reflex in nm is larger than the crystallite size determined on the 120 reflex in nm.  
     
     
         16 . The composition according to any one of claims  13 ,  14 , or  15 , characterized in that the crystallite size determined on the 020 reflex is from 10 to 50 nm.  
     
     
         17 . A method of preparing crystalline boehmitic alumina according to any one of claims  13 ,  14  or  15 , characterized in that aluminium-oxygen compounds are exposed to long-time hydrothermal aging in the presence of water at 60 to 240° C. for at least 10 hours.  
     
     
         18 . A composition comprising pure-phase aluminium oxide prepared from a crystalline boehmitic alumina according to any one of claims  13 ,  14  or  15  by thermal treatment.  
     
     
         19 . The composition of  claim 18 , characterized in that the aluminium oxide is present in the theta or delta phase.  
     
     
         20 . The composition according to any one of claims  18  or  19 , characterized in that after thermal treatment by calcination at 1,200° C. for 3 hours the aluminium oxide has a surface of greater than 60 m 2 /g.  
     
     
         21 . The composition according to any one of claims  18  or  19 , characterized in that the aluminium oxide has pore volumes of greater than 0.6 cm 3 /g determined by the mercury penetration method in the pore radius range of from 1.8 to 100 nm.  
     
     
         22 . The composition of  claim 18 , wherein said thermal treatment comprises calcination at a temperature of from 800 to 1500° C. for at least 0.5 hour.