Production, purification and polymerization of aromatic dicarboxylic acids

摘要

This invention provides a process for purifying the crude aromatic dicarboxylic acids produced by oxidation of dialkyl aromatic hydrocarbons and for using the purified acids in the preparation of polyethylene terephthalate, polyethylene naphthalate and other polyesters. The invention simplifies the manufacturing process by converting the crude aromatic acids into bis-glycol esters in an esterification reactor 4, from which the esterified partial oxidation impurities present in the oxidation product are removed by distillation in distillation tower 5. After removal of the volatile impurities, the dicarboxylic acid esters can separated by distillation in distillation tower 6 or by crystallization and converted to polyesters by polycondensation. The volatile impurities reoved as overhead from tower 5 can be recycled as stream 16 to the oxidation reactor where they act as oxidation promoters thereby optionally allowing for a bromine-free oxidation process for dialkyl aromatic hydrocarbons.