Effect of Hierarchical Architecture of Nickel Modified Mesoporous Catalysts on the Knoevenagel Condensation Reaction

A series of ordered mesoporous silicas (MCM-41, SBA-15 and KIT-6) were successfully synthesized and modified with nickel by incipient wetness impregnation method. The supports and catalysts were characterized by N₂ adsorption-desorption, XRD, TEM, H₂-TPR, UV vis-DR, XPS, ICP and Py FT-IR techniques. All the materials were evaluated in the Knoevenagel condensation reaction between vanillin and malononitrile under microwave irradiation. The catalytic results show the key role that the chosen porous structure plays in the deposition of the active phase and its catalytic behaviour. Thus, by designing a suitable mesoporous catalyst it was possible to carry out such Knoevenagel condensation to obtain 2-(4-hydroxy-3-methoxybenzylidene) malononitrile through a highly efficient and environmentally friendly process, without solvents and reducing reaction times by employing microwave heating.