One-Pot Room-Temperature Synthesis of Mg Containing MCM-41 Mesoporous Silica for Aldol Reactions

One-pot synthesis of Mg containing MCM-41 (Mg-MCM-41) materials was respectively carried out by a room temperature (RT) method and a hydrothermal (HT) method for aldol condensation of 4-nitrobenzaldehyde and acetone and self-condensation of acetone. The RT method can prepare MCM-41 materials containing large amounts of Mg while maintaining the structural characteristics of MCM-41 even at very low Si/Mg ratios (large Mg loadings), but the HT method cannot. The RT method can also give more active catalysts than the HT method, because the catalysts prepared by the RT method are more basic than those prepared by the HT one. The characterization indicates that Mg atoms in the Mg-MCM-41 prepared by the RT method exist as MgO disperses well on the wall surface of pores, while those in Mg-MCM-41 prepared by the HT method are included in the bulk with a smectite-like structure.