Development of terephthalic acid production process; Terefutarusan seizo process no kaihatsu

The demand of high-purity terephthalic acid is rapidly increasing as raw material for polyester fiber and PET. Hitachi Ltd. began to develop a production process of terephthalic acid to meet its demand. Terephthalic acid is produced from paraxylene and air by liquid phase oxidation in acetic acid solution using catalyst, however, this method cannot produce high-purity terephthalic acid by itself because of various byproduced impurities. Hitachi Ltd. now developed a hydrogenation catalyst and crystallization method for purification to remove impurities byproduced in a terephthalic acid production process. This paper outlines a terephthalic acid production process, in particular, a purification process. In a purification process, raw terephthalic acid mixed with water is dissolved by heating, and purified by hydrogenation through contact of impurities and hydrogen on an activated carbon-carried Pd catalyst layer. Purified terephthalic acid (PTA) is thus obtained through crystallization, separation and drying processes. 6 refs., 4 figs.