Patent ID: 8686188

Claim:
A method for refining an organic composition comprising 4-aminodiphenylamine, aniline, azobenzene, and phenazine, comprising feeding the organic composition to a first rectification column; producing a first effluent composition at a top of the first rectification column and a second effluent composition at a bottom of the first rectification column, wherein the first effluent composition comprises aniline, azobenzene, phenazine, and a small amount of 4-aminodiphenylamine, and the second effluent composition comprises mostly 4-aminodiphenylamine; feeding the second effluent composition to a second rectification column; and producing a 4-aminodiphenylamine composition at a top of the second rectification column and a residual composition at a bottom of the second rectification column, wherein the first rectification column is operated at a vacuum degree ranging from about 0.08 MPa to about 0.1 MPa, a reflux ratio of about 0.2:1 to about 10:1, a column top temperature of from about 70Â° C. to about 170Â° C., and a still temperature of from about 230Â° C. to about 310Â° C.