Abstract There is disclosed a cobalt catalyst recovery process which can provide substantially 100 percent recovery of cobalt from metaor para-xylene oxidation reaction products, in a catalytically active form relatively free from side reaction, tramp metal and corrosion products. The reaction medium, after recovery of isophthalic or terephthalic acid products, is distilled or flashed, diluted with water to achieve a cobalt concentration and acetic acid concentration sufficient to yield a pH of the solution above 3.0 and to precipitate iron and chromium values. The reaction medium is separated from these precipitates and treated with aqueous sodium carbonate which serves to convert the side reaction organic acids to soluble sodium salts and the cobalt to insoluble cobalt carbonate. Nickel impurities may be converted to a soluble form. The cobalt carbonate is separated out by filtration or the like, and is reconverted to cobalt acetate by treating the carbonate with acetic acid and, if desired, a minor amount of water. The catalyst solution, preferably after water removal, is recycled to the oxidation process.
The method of claim 1 wherein the mixture in step (c) is treated to produce a cobalt concentration of from about 0.1 to 15 weight percent based on the weight of the reaction mixture and an acetic acid concentration of from about 1 to 15 weight percent based on the weight of the reaction mixture.
Claim 2
Dependent Claim
55 words
The method of claim 2 wherein the mixture in step (c) is treated to produce a cobalt concentration of from about 0.5 to 10 weight percent based on the weight of the reaction mixture and an acetic acid concentration of from about 2 to 10 weight percent based on the weight of the reaction mixture.
Claim 3
Dependent Claim
21 words
The method of claim 2 wherein the mixture in step (c) is treated to produce a pH of above about 3.1.
Claim 4
Dependent Claim
37 words
The method of claim 4 wherein the aqueous sodium carbonate is supplied in step (d) in at least a 10 weight percent excess of the stoichiometric amount necessary to react with the cobalt and any acids present.
Claim 5
Dependent Claim
27 words
The method of claim 5 wherein the mixture from step (c) is treated with dilute aqueous sodium carbonate at a temperature of at least about 75* F.
Claim 6
Dependent Claim
39 words
The process of claim 5 wherein said conversion of cobalt carbonate in step (f) is conducted in the presence of water in an amount up to about 15 weight percent water based on the weight of the reaction mixture.
Claim 7
Dependent Claim
39 words
The process of claim 1 wherein said conversion of cobalt carbonate in step (f) is conducted in the presence of water in an amount up to about 15 weight percent water based on the weight of the reaction mixture.
Claim 8
Dependent Claim
34 words
The process of claim 8 wherein the water and acetic acid are supplied in step (f) at least in part by acetic acid and by-product water removed from the reaction mixture in step (c).
Claim 9
Dependent Claim
22 words
The method of claim 7 wherein water is subsequently removed from the solution of cobalt acetate and acetic acid from step (f).
Claim 10
Dependent Claim
29 words
The method of claim 10 wherein the cobalt carbonate from step (e) is washed with water to remove salts of sodium before conversion to cobalt acetate in step (f).
Claim 11
Dependent Claim
22 words
The method of claim 9 wherein water is subsequently removed from the solution of cobalt acetate and acetic acid from step (f).