Process for dicarboxylating dihydric phenols

A process is disclosed for dicarboxylating dihydric phenols, notably those where the hydroxyl groups are in the para or the ortho position vis-+E,gra a+EE -vis one another. More particularly, the invention pertains to a process for preparing 2,5-dihydroxyterephthalic acid (2,5 DHTA). The invention comprises contacting a dihydric phenol with carbon dioxide in the presence of an alkali metal carbonate, the reaction being carried out in the presence of an alkali metal formate, at a temperature above the formate's melting point. The invention has several advantages over the well-known Kolbe-Schmitt reaction and other known carboxylation reactions, such as a lower operating pressure, higher yields, and/or shorter reaction times.