二次氧化法纯化粗对苯二甲酸的影响因素

Influential Factors for Purification of Crude Terephthalic Acid by Secondary Oxidation

采用半连续实验装置对二次氧化法纯化粗对苯二甲酸(CTA)的过程进行了研究,考察了催化剂用量、纯化温度、CTA 粒径和固含率等因素对纯化过程的影响。实验结果表明,催化剂用量对纯化作用的影响是通过改变液相氧化反应速率来实现的,当液相氧化反应速率超过 CTA 的溶解速率时,增加催化剂用量不会加快纯化速率;升高温度,纯化速率和纯化程度都明显提高;粒径较小的 CTA 纯化速率更快。在208℃、催化剂质量分数3 5×10^(-4)、CTA 粒径89.9μm、纯化时间60 min 的条件下,CTA 中的对甲基苯甲酸的质量可减少70%～90%,对羧基苯甲醛的质量可减少70%～80%。

Purification of crude terephthalic acid （CTA） by secondary oxidation was studied. Influences of catalyst dosage, particle size of CTA, reaction temperature and solid holdup on purification of CTA were investigated in a semi-continuous experimental setup. Catalyst dosage affects the purification process by changing the liquid-phase oxidation rate. Under a set of specific reaction conditions, the addition of least catalyst dosage must be adjusted so that the oxidation rate of objects to be oxidized are at least faster than dissolving rate of CTA. Therefore further increasing of catalyst dosage cannot further accelerate the purification rate. The smaller particle size of CTA is advantageous to purification rate. The rising of reaction temperature obviously boost the rate and extent of purification. The mass of p-toluic acid and 4-carboxybenzaldehyde in CTA decrease by 70% -90% and 70% -80% respectively within 60 min at 208 ℃ when catalyst mass fraction is 3.5 ×10^-4 and particle size of CTA is 89.9 μm.