Process Optimization and Thermal Hazard Study for the Preparation of TBPB by a Two–Step Reaction

In this study, sodium dodecylbenzene sulfonate was used as a stabilizer, and NaOH, TBHP, and benzoyl chloride were used as reactants in the preparation of tert–butyl peroxybenzoate (TBPB) using a two–step process. The process conditions were optimized by a three–factor, three–level Box–Behnken design approach. The results showed that the yield of TBPB achieved 88.93% under the optimum conditions of temperature of 31.50 °C, feeding time of 22.00 min, and NaOH concentration of 15%. The exothermic properties of the synthesis of TBPB were investigated using reaction calorimetry. The thermal decomposition characteristics of reactants and products were analyzed by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC), and the changes in substance types, characteristic peaks, and exothermic quantities during the reaction were analyzed before and after the reaction by FTIR. The reaction mechanism was proposed by combining EasyMax 102, RC1e, gas chromatography (GC), and Fourier transform infrared spectrometry (FTIR). A comprehensive study of the reaction mechanism and reaction exotherm was carried out using density functional theory (DFT) to predict the reaction energy change and the direction of the reaction and to determine whether the reaction was reversible or not. The risk level for the synthesis of TBPB in semi–batch mode was evaluated using a risk matrix and the Stoessel criticality diagram. The optimal conditions for the TBPB synthesis process in a plate microreactor were explored. Both microreactors and semi–batch modes were comparatively analyzed using the m–ITHI quantitative assessment method. The results indicated a hazard class 2 in semi–batch mode and a hazard class 1 in the microreactor. The results of the study may provide a reference for the further improvement of the intrinsically safe design of the synthetic TBPB process.