Process for preparing low soda pseudoboehmite gel
AssigneeAluminum Company of America
InventorsKenneth P. Goodboy, James J. Koenig
Life of this patent
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Abstract
A low soda pseudoboehmite gel is provided by reacting a NaAlO.sub.2 solution with a NaHCO.sub.3 solution having a concentration of less than 75 grams/liter and preferably less than 50 grams/liter. The soda content of the resulting AlO(OH) gel can be further lowered by repeated washing and/or redispersing (repulping) in water and/or further neutralization with a carboxylic acid having 1 to 6 carbon atoms.
Claims6
A process for making a pseudoboehmite gel having a BET surface area of at least 325 m.sup.2 /g and a Na.sub.2 O content less than 3% by weight which consists of:
- (a) reacting NaAlO.sub.2 solution with a sufficient amount of a NaHCO.sub.3 solution having a concentration of less than 75 grams/liter to neutralize approximately 95% of the Na.sup.+ in said NaAlO.sub.2 to form a low Na.sub.2 O content pseudoboehmite gel while inhibiting the formation of dawsonite;
- (b) filtering the gel slurry to recover a gel filter cake;
- and
- (c) repulping and washing the resultant AlO(OH) product to further lower the Na.sub.2 O content.
A process for making a pseudoboehmite gel having a BET surface area of at least 325 m.sup.2 /g and a Na.sub.2 O content of less than 3% of the Al.sub.2 O.sub.3 weight which consists of:
- (a) reacting a solution containing 100-400 g/l caustic as Na.sub.2 CO.sub.3 and 0.6-0.8 grams Al.sub.2 O.sub.3 per gram of caustic as Na.sub.2 CO.sub.3 with a sufficient amount of solution containing less than 75 g/l NaHCO.sub.3 to neutralize approximately 95% but less than 100% of the Na.sup.+ in the solution as NaOH and NaAlO.sub.2 to form a AlO(OH) gel while inhibiting the formation of dawsonite;
- and
- (b) washing and/or redispersing (repulping) the AlO(OH) product with water in an amount equal to 5-70 l/kg of Al.sub.2 O.sub.3 one or more times.
A process for making a pseudoboehmite gel having a BET surface area of at least 325 m.sup.2 /g and Na.sub.2 O content less than 3% by weight which comprises:
- (a) reacting a NaAlO.sub.2 solution with a sufficient amount of a NaHCO.sub.3 solution having a concentration of less than 75 grams/liter to neutralize approximately 95% of the Na.sup.+ in said NaAlO.sub.2 to form a low Na.sub.2 O content pseudoboehmite gel while inhibiting the formation of dawsonite;
- (b) filtering the gel slurry to recover a gel filter cake;
- (c) pulping and washing the resultant AlO(OH) product to further lower the Na.sub.2 O content;
- and
- (d) repulping the washed AlO(OH) in water at a pH of 5-8 and neutralizing with a carboxylic acid containing 1-6 carbon atoms to further lower the Na.sub.2 O content to less than 3% and/or to increase the surface area.
Dependencies are inferred from the claim text.