To prevent thermal runaway incidents in semibatch reactors (SBRs), designing thermally safe operating conditions should be considered first. Regretfully, determination of the reaction kinetics for organic reactions is a time-consuming and money-consuming process, especially in the fine chemical and pharmaceutical industries. Therefore, it is desirable to develop kinetic-parameter-free methods that can design the right operating conditions. Along this line, a new facile approach to design thermally safe operating conditions for isoperibolic homogeneous SBRs has been developed in this article. This approach is developed on the basis of deep insights into the phenomenon that the MTSR vs reaction temperature profiles for isothermal exothermic reactions present an “S” shape. The approach has been experimentally validated using the hydrolysis reaction of acetic anhydride. However, more work should be carried out to extend this method to more complex reaction systems, like consecutive reactions.
Qiang Chen,Yuqing Ni,Jun Liang,Lei Ni,Juncheng Jiang,Yong Pan,Qingsheng Wang
Esterification reactions between anhydrides and alcohols catalyzed by sulfuric acid have broad applications in the food, cosmetic, and pharmaceutical industries. However, the exothermic behavior cannot be well explained, especially in semibatch reactors with different feeding procedures. In this study, a series of esterification processes in semibatch systems were conducted with a wide range of feeding rates with two different substrates. The structures of initial catalytic substrates were characterized using in situ Fourier Transform Infrared (FTIR) spectroscopy. A total of 11 reaction pathways, including those for the initial activation of substrates and the subsequent reactions of the feeding process, were calculated by the density functional theory (DFT) method. Three possible catalytic cycles of the esterification with specific acid catalysis, protonated intermediate, and protonated intermediate and H 2 O, were established for the semibatch esterification reaction based on calculated results and experimental evidence. Thermal safety parameters such as reaction enthalpy ( Δ H r ), adiabatic temperature rise ( Δ T r , a d ), and maximum temperature of the synthetic reaction (MTSR) were determined based on Wilson equation used to calibrate mixing heat. The results reveal that mixing heat was 2.5 kJ/mol with same mole ratio of n -butanol ( n B) and propionic anhydride (PA). The reactions started by PA are dominant, no matter whether the substrate is n B or PA. The initial reaction rate is restricted by the low concentration of catalyst and active reactant when n B is used as substrate, which lead to significant reactant accumulation with high MTSR of approximately 160 °C. Furthermore, feeding n B into PA allows a controllable increase in the Δ T r , a d realized by changing the feeding rate and limiting the accumulation of reactant.
危险品化学品经营许可证（带存储）