Kinetic Studies on Both Synthesis of Methacrolein Catalyzed by an Ionic Liquid and Catalyst Deactivation

Diethylamine acetate as an ionic liquid is used as a catalyst for the Mannich reaction of propanal and formaldehyde to produce methacrolein. However, catalyst deactivation remains a serious problem that has not been studied. Here, the reaction was carried out using different temperatures, atmospheres, and reagents to probe the catalyst deactivation mechanism. The proposed mechanism was further supported by data from Fourier transform infrared and electrospray ionization tandem mass spectrometry. Based on this mechanism, kinetic study of catalyst deactivation reaction between diethylamine acetate and formaldehyde was conducted in its initial stage at 85–115 °C for 15–60 min, in order to avoid complex situations in the subsequent reaction. Moreover, the kinetics of diethylamine acetate-catalyzed Mannich reaction was examined, and the pre-exponential factor, activation energy, and reaction order of each reactant were calculated by regression. These results contribute to the industrial application of this catalyst.