Synthesis Of Phenolic Acid Under Supercritical Conditions

Salicylic acid and O-MSA is important raw material and mid-product in medical, food and fine chemical industry. In these years, the needs for them has become greater than before, because more and more uses are developed.The present technology in the world to synthesis salicylic acid and O-MSA is a kind of gas-solid phase Kolbe-Schmitt reaction and solvent process Kolbe-Schmitt reaction. The technology needs longer time, more thermal energy, multifarious steps and solvent, and the solvent could pollute environment. The yield of the product is quite low.This thesis focus on synthesizing salicylic acid and O-MSA in supercritical CO2 which acts both as reaction media and as reactant by Kolbe-Schmitt reaction. The proper condition such as temperature, pressure and reaction time is studied,and the reaction kinetics of synthesizing salicylic acid in supercritical CO2 is also investigated. The experimental results show that we get a high yield of more than 95% of salicylic acid in SFC and the condition of SFC is as follows: the pressure of CO2 is 8.0MPa, the temperature is 120℃and the time is 90 minutes. We get a high yield of more than 75% of O-MSA in SFC. The condition of SFC is as follows: the pressure of CO2 is 8.5MPa, the temperature is 150℃and the time is 3 hours. The reaction order of synthesizing salicylic acid in supercritical CO2 is 2.0, and activation energy of the reaction is 45.08kJ/mol. In supercritical state, the reaction can be carried out with high speed in much lower temperature compared to the traditional technology that is gas-solid phase Kolbe-Schmitt reaction and solvent process Kolbe-Schmitt reaction. That is b ecause of great diffusibility and good solution power of SFC, the reaction is carried out in a homogenizing situation. Too much energy is not only conserved, but the product quality and production efficiency is also enhanced.This new technique provided by the study has been notarized as Chinese patent.