Patent ID: 8153840

Claim:
A process for making a polycarboxylic acid composition, said process comprising: (a) subjecting a multi-phase reaction medium to oxidation in a primary oxidation reactor to thereby produce a first slurry; (b) subjecting at least a portion of said first slurry to further oxidation in a secondary oxidation reactor, wherein said secondary oxidation reactor is a bubble column reactor, wherein said primary oxidation reactor defines therein a primary reaction zone, wherein said secondary oxidation reactor defines therein a secondary reaction zone, wherein the ratio of the volume of said primary reaction zone to the volume of said secondary reaction zone is in the range of from about 4:1 to about 50:1; wherein at least 80 weight percent of said aromatic compound introduced into said primary oxidation reactor is oxidized in said primary oxidation reactor; and whereby overhead gasses are transferred from the top of the secondary oxidation reactor to the primary oxidation reactor.