摘要 |
Continuous prodn. of terephthalic acid is effected by introducing into an oxidn. zone a liquid mixt. of dissolving acetic acid (comprising acetic acid and water) and p-xylene contg. a catalyst, the wt. ratio of aq. acetic acid in the reaction mixt. to p-xylene admitted into the oxidation zone being 4-7:1. A gas contg. oxygen is passed into the reaction mixt. and the reaction temp. is kept at 160-180 degrees C. The amt. of water in the acetic acid is 1-7 wt. %. The catalyst is a mixt. of a Co cpd., an Mn cpd. and bromine or a bromide, in which the amt. of Co cpd., determined as metal, is 800-1200 ppm (by wt.) of acetic acid, that of Mn cpd., determined as metal, is 1-30, pref. 1-20 wt. %, based on the Co cpd., as metal, and the amt. of bromine or bromide, determined as Br, is >=2.5, pref. =5 x the combined wt. of Co and Mn cpds., as metals. Residence time of the reaction mixt. in the oxidation zone is 30-120, pref. 40-100 mins. High quality terephthalic acid is produced without excessive consumption of acetic acid by combustion. The acid, after simple treatment, e.g. washing, can be directly esterified to produce PET. |