Supported mesoporous solid base catalysts for condensation of carboxylic acids

摘要

New mesoporous base catalysts (CM-HMS and CM-MCM-41) were synthesized by generating uniform particles of cerium and manganese oxides (MnO _x/CeO_2) in situ within hexagonal mesoporous silica (HMS) and MCM-41 supports. These catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), FTIR, temperature-programmed desorption of CO_2 (CO_2-TPD), and diffuse reflectance UV-visible (UV-vis) spectroscopy. Spectroscopic studies reveal that some particles of MnO_x/CeO_2 are incorporated into the walls of the silica network of HMS and MCM-41, while others are highly dispersed onto the surface of the HMS or MCM-41. The catalytic activity of CM-HMS and CM-MCM-41 for the ketonization of carboxylic acids was confirmed; better utilization of Ce and Mn was observed than in unsupported MnO_x/CeO_2. The citrate-based preparation of MnO_x/CeO_2 catalyst supported on HMS and MCM-41 has not been previously reported in the literature.