Continuous solvent-free synthesis of imines over uip--Al₂O₃-CeO₂ catalyst in a fixed bed reactor

One-pot synthesis of imines from benzyl alcohols and anilines by heterogeneous catalysis in batch reactor has already been widely studied, but its high cost and low production efficiency limit its application in the fine chemicals industry. In this work, gamma-Al2O3 balls supported CeO2 catalyst (uip-gamma-Al2O3-CeO2) was prepared by a novel unsaturated-impregnation-precipitation method, and was employed as a catalyst for continuous solvent-free synthesis of imines in a fixed bed reactor. Under the optimal technological parameter of fixed bed reactor and reaction condition, uip-gamma-Al2O3-CeO2-500 degrees C obtained remarkable 97 % yield of imine. After 20 days' continuous operation, the total isolated yield of imine and TONBA/CeO2 reached up to 81 % and 16838, respectively. Importantly, the catalyst could be reactivated in situ in the fixed reactor. Through detailed characterization, the extraordinary catalytic performance of uip-gamma-Al2O3-CeO2-500 degrees C can be attributed to the abundant acid sites of gamma-Al2O3 as well as the synergistic effect between CeO2 and gamma-Al2O3.