Process for producing alumina

Claim 2

In a process for the preparation of pure alumina wherein metallic aluminum is activated, the activated metallic aluminum is reacted in a aqueous solution to obtain an intermediate and then the intermediate is heat treated to obtain an alumina end product, the improvement in producing said intermediate which comprises employing aluminum having a purity of at least 99.5% and a specific surface of at least eight cm 2 /g, activating only the surface of the aluminum by contacting it with an aqueous acidic solution of (1) NaCl, KCl, NH 4 Cl, NH 4 HCO 3 or ICl or (2) water containing dissolved CO 2 , SO 2 , Cl 2 or F 2 , then washing said aluminum having only its surface activated with an aqueous medium having a neutral pH; then reacting the washed only surface activated aluminum in an aqueous solution and adjusting the pH of such solution to a basic pH to produce a fine-grained alumina.

Claim 3

In a process for the preparation of pure alumina wherein metallic aluminum is activated, the activated metallic aluminum is reacted in a aqueous solution to obtain an intermediate and then the intermediate is heat treated to obtain an alumina end product, the improvement in producing said intermediate which comprises employing aluminum having a purity of at least 99.5% and a specific surface of at least eight cm 2 /g, activating only the surface of the aluminum by contacting it with an aqueous acidic solution of (1) NaCl, KCl, NH 4 Cl, NH 4 HCO 3 or ICl or (2) water containing dissolved CO 2 , SO 2 , Cl 2 or F 2 , then washing said aluminum having only its surface activated with an aqueous medium having a neutral pH; then reacting the washed only surface activated aluminum in a aqueous solution and adjusting the pH of such solution to an acidic pH to produce an alumina gel.

Claim 4

In a process for the preparation of pure alumina wherein metallic aluminum is activated, the activated metallic aluminum is reacted in a aqueous solution to obtain an intermediate and then the intermediate is heat treated to obtain an alumina end product, the improvement in producing said intermediate which comprises employing aluminum having a purity of at least 99.5% and a specific surface of at least eight cm 2 /g, activating only the surface of the aluminum by contacting it with an aqueous acidic solution of (1) NaCl, KCl, NH 4 Cl, NH 4 HCO 3 or ICl or (2) water containing dissolved CO 2 , SO 2 , Cl 2 or F 2 , then washing said aluminum having only its surface activated with an aqueous medium having a neutral pH; then reacting the washed only surface activated aluminum in a aqueous solution and adjusting the pH of such solution to an acidic pH to produce an alumina gel.

Claim 5

In a process for the preparation of pure alumina wherein metallic aluminum is activated, the activated metallic aluminum is reacted in a aqueous solution to obtain an intermediate and then the intermediate is heat treated to obtain an alumina end product, the improvement in producing said intermediate which comprises employing aluminum having a purity of at least 99.5% and a specific surface of at least eight cm 2 /g, activating only the surface of the aluminum by contacting it with an aqueous acidic solution of (1) NaCl, KCl, NH 4 Cl, NH 4 HCO 3 or ICl or (2) water containing dissolved CO 2 , SO 2 , Cl 2 or F 2 , then washing said aluminum having only its surface activated with an aqueous medium having a neutral pH; then reacting the washed only surface activated aluminum in a aqueous solution and adjusting the pH of such solution to a neutral pH to produce alumina in a plate-like crystalline form.

Claim 6

In a process for the preparation of pure alumina wherein metallic aluminum is activated, the activated metallic aluminum is reacted in a aqueous solution to obtain an intermediate and then the intermediate is heat treated to obtain an alumina end product, the improvement in producing said intermediate which comprises employing aluminum having a purity of at least 99.5% and a specific surface of at least eight cm 2 /g, activating only the surface of the aluminum by contacting it with an aqueous acidic solution of (1) NaCl, KCl, NH 4 Cl, NH 4 HCO 3 or ICl or (2) water containing dissolved CO 2 , SO 2 , Cl 2 or F 2 , then washing said aluminum having only its surface activated with an aqueous medium having a neutral pH; then reacting the washed only surface activated aluminum in a aqueous solution and adjusting the pH of such solution to a neutral pH to produce alumina in a plate-like crystalline form.