Patent ID: 7060853

Claim:
A process for increasing the production capacity of a conventional back-mixed oxidation reactor for catalytic liquid phase, air oxidation of paraxylene to terephthalic acid, said method comprising: (a) positioning a first reaction zone upstream of a second zone comprising said conventional back-mixed oxidation reactor; (b) feeding acetic acid, oxidation catalyst, paraxylene, and a supply of oxygen to said first reaction zone to form a reaction medium in which the acetic acid:paraxylene mass ratio is in the range of from 13–16:1 and the operating pressure is at least about 2,500 kPa; (c) limiting the uptake of oxygen within the reaction medium in said first reaction zone to a value which is less than that required for full conversion of the paraxylene present to terephthalic acid, wherein said terephthalic acid produced in the reacton medium in the first reaction zone remains in solution; and then (d) feeding the reaction medium to said conventional back-mixed oxidation reactor in said second reaction zone while simultaneously reducing the pressure of the reaction medium to a value in the range of from about 500 kPa to less than 2,500 kPa; (e) vaporizing a portion of the acetic acid present in said conventional back end reactor in said second zone; (f) removing the vapor from the reactor overhead; (g) condensing the vapor; and (h) recycling some or all of the condensate to the first reaction zone.