Hydrothermally stable alumina

Abstract

The hydrothermal stability of transition aluminas used as adsorbents and catalyst carriers is improved through their treatment with a soluble silicon inorganic compound such as sodium silicate wherein the silicon compound is mixed with the alumina powder at the production stage of forming particulates by liquid addition. The silicon containing particulates are activated by heating at a temperature lower than 500° C. and treated, before or after the thermal activation, by a colloidal silica solution to produce a hydrothermally stable, low dust alumina. The total silica content of the final product is typically less than 5 mass-%.

1 . A process of making a hydrothermally stable alumina adsorbent comprising mixing together a solution containing a silica compound with a quantity of alumina powder to produce alumina particulates, curing said alumina particulates and then activating said cured alumina particulates to produce said hydrothermally stable alumina adsorbent. 
   
   
       2 . The process of  claim 1  further comprising spraying said alumina particulates with water or a colloidal silica solution. 
   
   
       3 . The process of  claim 1  further comprising spraying said cured alumina particulates with water or a colloidal silica solution. 
   
   
       4 . The process of  claim 1  wherein said silica compound is at least one compound selected from the group consisting of alkali and alkaline earth metal silicates. 
   
   
       5 . The process of  claim 4  wherein said silica compound is a sodium silicate. 
   
   
       6 . The process of  claim 1  wherein said hydrothermally stable alumina adsorbent comprises between 0.1 and 8 percent by weight silica. 
   
   
       7 . The process of  claim 6  wherein said hydrothermally stable alumina adsorbent comprises between 2 to 4 percent by weight silica. 
   
   
       8 . The process of  claim 6  wherein said silica is added by spraying of a colloidal silica solution. 
   
   
       9 . The process of  claim 1  wherein said hydrothermally stable alumina adsorbent comprises about 2 percent by weight silica within said adsorbent and about 2 percent by weight silica coating said adsorbent. 
   
   
       10 . The process of  claim 1  wherein said hydrothermally stable alumina adsorbent comprises silica containing alumina particles comprising a core, a shell and an outer surface, said core containing between about 0.4 to 4 wt-% silica wherein said silica is homogeneously distributed throughout said core and said shell extending up to 50 micrometers from said outer surface towards said core and wherein said shell contains on average at least two times more silica than said core.