Research On Synthesis Of Phenolic Acid By Supercritical Methods

5-Aminosalicylic acids is one of the preferred drugs in clinical; O-MSA is one important mid-product in dye and medical industry, so it has important significance to investigate the process of their preparation and so on.The present technology processes in the world to synthesis 5-Aminosalicylic acids and O-MSA are mainly suspension reaction,gas-solid phase reaction and solvent process.All of them need long time,more energy, complicated operation and easily bring pollution,as well as have a low yield.Moreover, they haven't been enhanced so far.The thesis focuses on synthesizing 5-Aminosalicylic acids acid and O-MSA in supercritical CO₂ which acts both as reaction media and reactant by Kolbe-Schmitt reaction. As the supercritical CO₂ has great diffusibility and good solution power, the reaction can be carried out in a homogenizing situation compared to the traditional technologies that are gas-solid phase reaction and solvent process. Therefore, we need shorter time and smaller stir speed, the product quality and production efficiency are also enhanced. The proper conditions such as reaction temperature, pressure ,time and the stir speed are studied,and the reaction kinetics of synthesizing 5-Aminosalicylic acids in supercritical CO₂ is also investigated. The experimental results show that more than 90.5% of the yield of 5-Aminosalicylic acids can be obtained under the optimal reaction parameters such as temperature (140℃), pressure (9.0MPa), reaction time (2.5h) and stir speed (300rpm). And more than 75% of O-MSA can be obtained under the following conditions: the pressure of CO₂ is 8.5MPa, the temperature is 150℃and the time is 3 hours. The reaction order of synthesizing 5-Aminosalicylic acids in supercritical CO₂ is 2.7, and activation energy of the reaction is 1.343kJ/mol.Compared to the traditional technology, the method of synthesizing 5-Aminosalicylic acids acid and O-MSA in supercritical CO₂ is a new"Green Technology".