Studies On Supercritical Fluid Chemistry Reaction To Synthesis P-hydroxybenzoic Acid

Ester p-Hydroxybenzoate is a kind of preservatives, which has a wide of use and is efficacious and safe. The production of Ester p- Llydroxybenzoate is very small in our country, only because of the backward technology processes of its intermediate, p-Hydroxybenzoic acid. The present technology processes in the world of synthesis p- Hydroxybenzoic acid are gas-solid phase reaction and suspension reaction. Both of them waste time, energy and bring pollution, as well as there is a yield below 45%. The thesis focus on synthesis of p-Hydroxybenzoic acid in supercritical state, which supercritical fluid CO2 (SFC) acts both as reaction media and as reactant. Because the SEC has a great diffusibility and good solution power, the gas-solid phase reaction is carried out in a similar homogenizing situation. So we get a yield of p- Hydroxybenzoic acid above 80%. The proper reaction conditions such as pressure, temperature, reaction time and speed of the stir are also studied, We need shorter reaction time, less energy and do not pollute the environments. The reaction conditions are as follows: the CO2 pressure is 8.5 Mpa, the temperature is 240t, the reaction time is 60 minutes and the stir speed is 400rpm. We also found a method, which make the. products purer, less loss and make potassium salt to be recovered easier. Additionally, the synthetic route of Ethyl p-Hydroxybenzoate and its antibacterial effect are discussed in this paper. The experiment 2 shows that Ethyl p-Hydroxybenzoate and p-Hydroxybenzoic acid has an excellent antibacterial effect.