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A process for producing a purified terephthalic acid which comprises reacting in a liquid phase a mixture of hydrogen and crude terephthalic acid, a palladium/rhodium catalyst on a porous carbonaceous support wherein the catalyst compound is prepared by adsorbing palladium on the support from a comp

A process for producing a purified terephthalic acid which comprises reacting in a liquid phase a mixture of hydrogen and crude terephthalic acid, a palladium/rhodium catalyst on a porous carbonaceous support wherein the catalyst compound is prepared by adsorbing palladium on the support from a complex salt formed in the presence of an amine and acetic acid, followed by deposition of rhodium from a solution of sodium hexanitritorhodate.

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A process for purifying crude terephthalic acid containing up to 10,000 ppm of 4-carboxybenzaldehyde wherein said 4-carboxybenzaldehyde content is decreased to less than 100 ppm and p-toluic acid content increase is minimized which comprises hydrogenating said crude acid at a temperature of from abo

A process for purifying crude terephthalic acid containing up to 10,000 ppm of 4-carboxybenzaldehyde wherein said 4-carboxybenzaldehyde content is decreased to less than 100 ppm and p-toluic acid content increase is minimized which comprises hydrogenating said crude acid at a temperature of from about 100°C. to about 300°C. and a pressure of from 200 to 1500 psi with hydrogen in the presence of a catalyst composition which comprises crystallites of palladium and rhodium adsorbed on a porous activated carbon support material, said support having a surface area of at least 600 m2/g, wherein said catalyst composition is prepared by contacting said support with (a) an aqueous solution of an amine and a palladium salt in the presence of an organic carboxylic acid wherein concentration of said amine is sufficient to solubilize said palladium salt and mole ratio of said acid to said amine is at least 0.75 and with (b) an aqueous solution of a rhodium compound and an alkali metal nitrite wherein penetration of said palladium and rhodium crystallites into said porous support is within the range of from about 70 to 150 micrometers of the surface of said support.