Published May 1974
Maruzen Oil Company developed a process for manufacturing terephthalic acid by oxidizing p-xylene. The process has the following characteristics:
- The process is a one-stage oxidation of p-xylene
- The purification step is simple
- The product can be used to make continuous filament yarn as well as staple
- The product, together with a small amount of ethylene glycol, forms a slurry with high fluidity
- The process is in commercial use in Japan
There appear to be two main features to the process, namely, the operating conditions in the oxidation step and the purification precedure. The preferred conditions in the oxidation step seem to be: solvent, acetic acid; catalyst system, cobalt, manganese, and bromine compounds (one of the best systems is the combination cobalt bromide and manganese acetate) oxidizing medium, air. The outstanding feature of the process is the surprisingly high purity of the crude product from the oxidation step; an example in refererence, the 4-carboxyybenzaldehyde (4-CBA) content of the crude terephthalic acid was only 90 ppm. The yield was also very high, 96 mol%.
We have not attempted to estimate the costs associated with the process but, because of the relatively simple purification method and mild conditions, it appears the process hould have relatively favorable capital and production costs.