Knoevenagel condensation reaction over CaO/HMCM-22 with acid-base bifunction

CaO/HMCM-22 molecular sieve catalysts were prepared by impregnating the catalyst MCM-22 with an aqueous solution of Ca(NO₃)₂. Catalysts were characterized by XRD, FT-IR, TPD. The results show that no significant structural change of MCM-22 was observed after modification. CaO could be highly dispersed on the surface of MCM-22 with low loading. The strength and content of base of the catalyst increase, while its content of strong acid decreased obviously with the increase of CaO loading. However, its amounts of weak acid sites increase slightly. The Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate was carried out over CaO/HMCM-22 catalysts. It was found that, 88.9% conversion of benzaldehyde can be obtained under conditions of reaction temperature of 353 K, reaction time of 4 h, the molar ratio of benzaldehyde to ethyl cyanoacetate equal to 1:1, mass fraction of catalyst to reactants 3.0% and ethanol as solvent. The catalytic performance of CaO/HMCM-22 is better than that of HMCM-22 and CaO/MCM-22, since the catalytic benzaldehyde conversion of HMCM-22 and CaO/MCM-22 are only 6.6% and 62.4%, respectively. The novel CaO/HMCM-22 molecular sieve catalysts exhibit the acid-base coordinative catalysis obviously.