| 摘要 |
PURPOSE:To reduce the combustion loss of acetic acid solvent in the preparation of high purity terephthalic acid by the combination of oxidation, low-temperature post-oxidation, and high-temperature post-oxidation of p-xylene, by using a specific process. CONSTITUTION:High purity terephthalic acid is prepared continuously by reacting p-xylene with oxygen in acetic acid solvent in the presence of a catalyst containing a heavy metal and bromine. The process is carried out by (1) charging p-xylene and O2 in the first tank reactor maintained at 180-230 deg.C, (2) oxidizing at least 95wt% of p-xylene to terephthalic acid, (3) transferring the oxidation product to the second tank reactor 2 maintained at a temperature lower than the first reactor by 0-50 deg.C to effect the first post-oxidation with O2, (4) raising the pressure of the resultant mixture, (5) heating the mixture at >=235 deg.C with the tubular heater 4 to effect the second post-oxidation, (6) keeping the resultant mixture in a tank 5 maintained at >=235 deg.C at least for 5min, and finally (7) crystallizing with the crystallizer 6 and filtering the product to recover the terephthalic acid. |
