Hydroquinone Carboxylation to 2,5-dihydroxyterephthalic Acid by Solvent Method and the Activity of PdCl2/C Catalyst

摘要

1.Introduction 2,5-Dihydroxyterephthalic acid (2,5-DHTA) is an important intermediate in organic synthesis, which is widely used for the manufacture of organic optoelectronic materials, colorants, and fluorescent materials. 2,5-DHTA can react with glycols for the manufacture of linear polyester and copolyesters possessing fiber-or film-forming properties[1-3]. The synthesis of 2,5-DHTA can be carried out by a Kolbe-Schmitt reaction. The Kolbe-Schmitt reaction involves three steps, which are shown in Scheme 1.Potassium salt of hydroquinone is first prepared by reaction of hydroquinone with potassium hydroxide or potassium carbonate. The second step is the carboxylation of dipotassium salt of hydroquinone with CO2 under high pressure. Then 2,5-DHTA can be obtained by acidification with hydrochloric acid.