Study On The Preparation Of 2, 6-Dihydroxybenzoic Acid In Solvent Under Atmospheric Pressure

The synthesis of 2,6-Dihydroxybenzoic acid(2,6-DHBA) has been investigated. 2,6-DHBA is an important organic synthetic intermediate,which is widely used in the production of pharmaceutical, colorants and pesticide and so on. For instance , it can be used to synthesize bispyribac-sodium acid Bispyribac-sodium and highly efficient herbicide KIH-2023. Beginning from the raw material-resorcinol, carboxylation reaction with carbon dioxide gas in the presence of potassium carbonate was proceeded at 170℃and atmospheric pressure, then the main product was 2,6-DHBA. The experiments have proved that the products controlled by dynamics are obtained under ordinary conditions. The synthesis conditions of 2,6-DHBA were optimized on the base of experiments. The effect of reaction temperature and organic solvent and ratio of raw material and quality of the product was discussed in detail. In order to increase the yield, a new solvent diglycol is used in this experiment, because of its existence, carboxylation reaction may proceed under temperate condition, most importantly it causes the pressure to become the atmospheric pressure. By orthogonal test, the best conditions for preparation of 2,6-DHBA were as follows: reaction time is 6h; reaction temperature 170℃.the molar ratio of resorcinol to Potassium carbonate 1:0.5.The yield of 2,6-DHBA is more than 35%. Then its typical structure characteristics are taken with IR,melting point and XRD.