Process and apparatus for producing aromatic dicarboxylic acids

In a process for producing an aromatic dicarboxylic acid by the liquid-phase oxidation of a benzene derivative with molecular oxygen in a lower aliphatic carboxylic acid solvent in the presence of an oxidation catalyst by means of a vertically oriented generally cylindrical reactor capable of retaining a liquid therein, in which said reactor has (a) means for feeding liquid starting material to the liquid phase in said reactor, said means for feeding liquid starting material comprising a tubular member being oriented vertically in the liquid phase in said reactor;

• (b) means in said reactor for stirring the liquid phase in said reactor;
• (c) means for passing molecular oxygen or molecular oxygen containing gas into the liquid phase in said reactor;
• (d) means for feeding an oxidation catalyst into said reactor;
• (e) means for removing the product from the bottom of said reactor;
• and (f) means for recovering the vapor from the upper portion of said reactor;
• introducing the vapor into the condenser, and refluxing the resulting condensate into said reactor, characterized in that the liquid phase portion of said tubular member for feeding liquid starting material to the liquid phase in said reactor at least partially comprises a porous material, the porous material is oriented vertically in the liquid phase, the liquid starting material is fed into the liquid phase of said reactor through the porous material of said tubular member, the pressure of said liquid starting material drops by more than 1 kg/m.sup.2 during passage through said porous material and the liquid starting material is fed into the liquid-phase reaction system in a dispersed state.