Knoevenagel condensation reaction over acid-base bifunctional MgO/HMCM-22 catalysts

MgO/HMCM-22 catalysts were prepared by impregnation and characterized by X-ray diffraction, N₂ physical adsorption-desorption, scanning electron microscopy, Fourier-transform infrared spectroscopy, temperature-programmed desorption of NH₃, and temperature-programmed desorption of CO₂. The results show that there were no significant structural changes in the MCM-22 zeolite after modification. Increasing the MgO loading increased the strength and content of the base, whereas the strength of the strong acid decreased significantly and the amount of weak acidic sites increased slightly. Knoevenagel condensation reactions were carried out as the probe reactions over the catalysts. Both acidic sites and basic sites significantly promoted the reaction. The conversion of benzaldehyde reached 92.6% under the optimal conditions. The catalytic performance of MgO/HMCM-22 and MgO/NaMCM-22 was better than that of HMCM-22 and MgO. The MgO/HMCM-22 catalysts gave good catalytic performance for Knoevenagel condensation reactions and exhibited obvious acid-base synergetic effects.