4-Hydroxybenzoic Acid CAS 99-96-7

There are great deals of manufacturing techniques for p-hydroxybenzoic acid. Potassium phenate carboxylation strategy is much better for industrial manufacturing. Regulations. Add concerning 40% potassium hydroxide choice as well as phenol right into the reaction pot and likewise mix, stir at 100 ° C for 0.5 h, till the free base of the potassium phenate remedy is 0.3-1.2%. Home home heating, dehydration at normal pressure, in addition to transforming to dehydration under decreased pressure when the inner temperature degree gets to 140 ° C, along with distilling water at a pressure of 10.6 kPa for concerning 0.5-1h up until the internal temperature level reaches over 170 ° C. Include the solvent phenol for azeotropic dehydration, as well as additionally finish the dehydration at 200 ° C(2.67 kPa) to get a compound salt of potassium phenate as well as phenol. Continue to warm up the prepared compound salt to 220-230 ° C, pass in cleansed anhydrous carbon dioxide, preserve the pressure at 0.5 MPa, react for 2.5 hours, cool to 200 ° C along with include phenol, maintain mixing for thirty minutes, as well as afterwards recover phenol under decreased pressure to do. Then co2 is introduced for the 2nd carboxylation, which takes about 2 hrs. After carboxylation, recuperate phenol, cool down to listed below 180 ° C, include water to dissolve, along with get carboxylation remedy (dipotassium p-hydroxybenzoate). Consist of sulfuric acid gradually to the carboxylation solution, reduce the effects of listed below 70 ° C to pH 6.7. Stylish and filter to eliminate potassium sulfate, recrystallize the gotten raw filter cake with water, as well as decolorize with triggered carbon to obtain p-hydroxybenzoic acid with a web content of more than 99%. Dipotassium p-hydroxybenzoate can additionally be gotten by transposition of dipotassium salicylate. As a result, p-hydroxybenzoic acid can in addition be obtained industrially from salicylic acid via salification, translocation, and additionally neutralization, nevertheless the price is rather high. In addition to that, p-toluenesulfonyl chloride, a spin-off in the manufacturing of saccharin, can also be gotten with ammoniation, oxidation, acid rainfall, alkali combination, as well as acid rainfall. The yield of this method is reduced, the expenditure is high, as well as additionally the by-product of saccharin generally includes toxic contamination o-sulfonamidotoluene.