Treatment of alumina-base catalysts

Claim 2

A process for the treatment of spent particulate alumina-base catalysts, comprising: (a) treating the particles of catalyst with gaseous sulfur trioxide at a temperature of from 350° to 550° C. to cause a first reaction converting at least a substantial portion of the alumina present inthe catalyst to aluminum sulfate; and (b) treating the particles produced in step (a) with an aqueous solution of the hydroxide of a cation having a soluble sulfate salt at a pH of 9 to 12 to cause a second reaction converting at least a substantial proportion of the aluminum sulfate to an aluminum hydroxide.

Claim 3

The process of claim 1 wherein the sulfur trioxide gas is prepared by the reaction of sulfur dioxide and oxygen gases in the presence of the catalyst particles in step (a).

Claim 4

The process of claim 2 wherein the reaction temperature in step (a) is between 350° and 550° C.

Claim 5

The process of claim 1 wherein the catalyst particles have been air-roasted prior to their treatment in step (a).

Claim 6

The process of claim 4 wherein the air-roasted catalyst particles have been leached of at least a portion of their catalytic metals prior to their treatment in step (a).

Claim 7

The process of claim 1 wherein the catalyst particles have not been air-roasted prior to their treatment in step (a).

Claim 8

The process of claim 1 wherein the pH of the solution is step (b) is between 10 and 11.

Claim 9

The process of claim 1 wherein the hydroxide is selected from the group consisting of sodium and ammonium hydroxides.

Claim 10

A process for the treatment of spent particulate alumina-base catalyst comprising (a) treating the particles of catalyst with aqueous sulfur trioxide at a temperature of from 350° to 550° C. to cause a first reaction converting at least a substantial portion of the alumina present in the catalyst to aluminum sulfate; and (b) treating the particles produced in step (a) with an aqueous solution of the hydroxide of a cation having a soluble sulfate salt, which aqueous solution also contains carbonate and bicarbonate ions, at a pH of 9 to 12, to cause a second reaction converting at least a substantial proportion of the aluminum sulfate to an aluminum hydroxide carbonate.

Claim 11

A process for the treatment of spent particulate alumina-base catalyst comprising (a) treating the particles of catalyst with aqueous sulfur trioxide at a temperature of from 350° to 550° C. to cause a first reaction converting at least a substantial portion of the alumina present in the catalyst to aluminum sulfate; and (b) treating the particles produced in step (a) with an aqueous solution of the hydroxide of a cation having a soluble sulfate salt, which aqueous solution also contains carbonate and bicarbonate ions, at a pH of 9 to 12, to cause a second reaction converting at least a substantial proportion of the aluminum sulfate to an aluminum hydroxide carbonate.

Claim 12

The process of claim 9 wherein the solution in step (b) contains ammonium hydroxide and ammonium carbonate, and the reaction product is NH 4 Al(OH) 2 CO 3 .H 2 O.

Claim 13

The process of claim 10 wherein the NH 4 Al(OH) 2 CO 3 .H 2 O is heated to between 150° and 300° C. to cause its decomposition to an aluminum hydroxide.

Claim 14

The process of claim 11 wherein the heating temperature is about 200° C.