PROCESS FOR PREPARING AROMATIC CARBOXYLIC ACIDS

摘要

The present invention relates to a process for making terephthalic acid by reacting a starting material and oxygen in the presence of a heterogeneous catalyst and p-xylene as solvent to produce a solution of terephthalic acid (TPA). The starting material is p-xylene, p-toluic acid, 4 carboxybenzaldehyde, or a mixture of any two or more thereof. No solid TPA is formed during the reaction in contrast to previous manufacturing methods that utilize acidic solvents and precipitate TPA as it forms. By avoiding the direct precipitation of TPA during formation, the present methods avoid many shortcomings of the conventional manufacturing methods used to produce TPA. In particular, the present methods do not require additional purification steps to remove reaction byproducts; film grade TPA can be obtained directly from starting material in a one-step process.