H_3PW_(12)O_(40) supported on mesoporous MCM-41 and Al-MCM-41 materials: Preparation and characterisation

摘要

MCM-41 and Al-MCM-41 has been synthesized using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 °C for 4 h. HPW heteropolyacid supported on the mesoporous were prepared using the incipient wetness method. The characterization of materials was performed by X-ray diffraction, Transmission Electron Microscopy, N_2 adsorption, ~(29)Si Cross Polarization-Magic Angle Spinning and ~(27)Al MAS NMR. Results showed that the hexagonal structure is obtained in both cases. The Aluminium species are located inside an extraframework. The impregnation reduces the surface area of the mesoporous materials especially of the Al-MCM-41 suggesting a participation of aluminium during the impregnation. HPW is well dispersed in the mesoporous materials and is located inside the pores interacting with the silanol group of the pores wall. ~(27)Al MAS NMR measurements have showed that the impregnation causes the removal of the non-framework aluminium.