The Catalytic Oxidation of p-Xylene to Terephthalic Acid in ScCO{sub}2

摘要

The feasibility of synthesizing terephthalic acid (TA) has been demonstrated via the oxidation of p-xylene (PX) in supercritical carbon dioxide (scCO{sub}2) at 150°C in our paper. Reactions were carried out in a 150 ml vessel. Oxygen served as the oxidant and CoBr{sub}2 or Co(OAc)2·4H{sub}2O as the catalysts. The effects of reaction time, metal ion and different catalysts on the conversion of PX and the selectivity of TA and the product distribution were investigated. Results showed that when the iron ion, especially Fe{sup}(2+), reduced the oxidation ability by reacting with Co{sup}(3+). The conversions of PX with CoBr{sub}2 as the catalysts at 1 hour and 6 hour were 74.45% and 84.80% respectively, and the corresponding molar selectivities of PT, TA and 4-CBA were 0.57, 0.21, 0.17 and 0.49, 0.31 0.16 separately. However, longer reaction time resulted in the degradation of target products. The experimental results provided some insight into the reaction mechanism.