Study on Reaction Mechanism and Process Safety for Epoxidation.

The reaction mechanism and process safety for epoxidation were investigated in this study. 1-(2-Chlorophenyl)-2-(4-fluorophenyl)-3-(1,2,4-triazole) propene (triazolene), a typical representative of high steric olefinic compounds, was chosen as the raw material. In addition, hydrogen peroxide was chosen as the oxygen source in the reaction. Online Raman spectroscopy combined with high-performance liquid chromatography (HPLC) was used for the process monitoring analysis. The results of this study indicated that the epoxidation process is exothermic, and the apparent reaction heat was 1340.0 kJ·kg-1 (measured by the mass of triazolene). The heat conversion rate was 39.7% immediately after hydrogen peroxide dosing to a triazolene and maleic anhydride mixture solution in chloroform. This result indicated that a considerable amount of heat is accumulated during the epoxidation reaction, which leads to a potential high safety concern. The study of the reaction mechanism showed that maleic anhydride reacts with hydrogen peroxide quickly to form maleic acid peroxide, which is controlled by hydrogen peroxide feeding, and the formed maleic acid peroxide further reacts with triazolenes slowly, which is a kinetically controlled reaction. Decomposition kinetics studies revealed that the temperatures corresponding to the time of maximum reaction rate for 8 and 24 h are TD24 = 89.9 °C and TD8 = 104.1 °C, respectively.