Crystalline boehmite materials as precursors for large crystal gamma alumina and low surface area alpha alumina
A process for preparing crystalline boehmite includes combining a stoichiometric amount of flash calcined gibbsite (AI 2 O 3 ) and gibbsite (Al(OH) 3 ) in a pressurizable reaction vessel; heating the flash calcined gibbsite and gibbsite in the reaction vessel to a temperature of about 200° C. to about 280° C. and for a time sufficient to form crystalline boehmite. A crystalline boehmite exhibiting a crystallite from about 600 Å to about 850 Å when measured in the 120 direction of the crystallographic space group Cmcm.
1 . A process for preparing crystalline boehmite, the process comprising:
combining a stoichiometric amount of flash calcined gibbsite (Al 2 O 3 ) and gibbsite (Al(OH) 3 ) in a pressurizable reaction vessel;
heating the flash calcined gibbsite and gibbsite in the reaction vessel to a temperature of about 200° C. to about 280° C. and for a time sufficient to form crystalline boehmite wherein the combining of the stoichiometric amount of flash calcined gibbsite and gibbsite is at a 1:1 molar ratio of flash calcined gibbsite Al 2 O 3 to gibbsite Al(OH) 3 .
2 . The process of claim 1 , wherein the temperature is from about 200° C. to about 260° C.
3 . The process of claim 1 , wherein the heating occurs for a time sufficient to form at least about 5 mol % of crystalline boehmite based on the total amount of solids.
4 . The process of claim 1 , wherein the time sufficient to form crystalline boehmite is at least about 30 minutes.
5 . The process of claim 1 , wherein the time sufficient to form crystalline boehmite is about 30 minutes to about 1 week.
6 . The process of claim 1 , wherein the pressurized vessel is configured to prevent or minimize the release of steam from the vessel.
7 . The process of claim 1 , wherein the crystalline boehmite exhibits a crystallite size of about 600 Å to about 850 Å.
8 . The process of claim 1 , wherein about 10 mol % to about 100 mol % of crystalline boehmite is formed based on the total amount of solids.
9 . The process of claim 1 , further comprising doping the crystalline boehmite with a rare earth element, bismuth, an alkaline earth metal, or a mixture of any two or more thereof.
10 . The process of claim 1 , wherein the flash calcined gibbsite contains up to about 15 wt % water.
11 . A process for preparing a transitional alumina, the process comprising:
preparing crystalline boehmite via a process comprising:
combining a stoichiometric amount of flash calcined gibbsite (Al 2 O 3 ) and gibbsite (Al(OH) 3 ) in a pressurizable reaction vessel;
heating the flash calcined gibbsite and gibbsite in the reaction vessel to a temperature of about 200° C. to about 280° C. and for a time sufficient to form crystalline boehmite; and
calcining the crystalline boehmite to form the transitional alumina wherein the combining of the stoichiometric amount of flash calcined gibbsite and gibbsite is at a 1:1 molar ratio of flash calcined gibbsite Al 2 O 3 to gibbsite Al(OH) 3 .
12 . The process of claim 11 , wherein the calcining is conducted at a temperature of about 400° F. to about 1200° F.
13 . The process of claim 11 , wherein the transitional alumina comprises γ-alumina.