Breaking the Equilibrium at the Interface: Microwave-Assisted Reactive Distillation (MARD)

Microwave irradiation has shown the intensification effect on reactive distillation. Herein, we report a systematic study of microwave-assisted reactive distillation (MARD) relative to its counterpart by the conventional heating, aiming at understanding the intensification mechanism of MARD. Catalytic homogeneous esterification of phthalic anhydride with 2-ethylhexanol for producing dioctyl phthalate (DOP) was studied as the model system, showing the improved performance by MARD. However, the comparative study on the effect of the reaction temperature and microwave power density showed that the reaction system was mainly affected by the system temperature, suggesting the dominant thermal effect in MARD. Phase equilibrium of the model system by different heating methods was investigated, showing an improved water content in the vapour phase promoted by the microwave heating than the conventional heating. Therefore, the rapid selective heating of water content at the liquid-vapour interface in MARD caused the change of the relative volatility of system, facilitating the intensified evaporation of water molecules at the liquid-vapour interface, and hence the improved performance.