Highly dispersed heteropolyacids supported on modified MCM 41 mesoporous materials

Solid acid catalysts consisting of heteropolyacids (HPAs) H(3)PMo(12)O(40) (HPM) and H(4)PVMo(11)O(40) (HPVM) supported on mesoporous pure-silica molecular sieve MCM-41 and modified molecular sieves Al-MCM-41 and Fe-MCM-41 have been prepared and characterized by XRD, FT-IR, (31)P MAS NMR, low temperature nitrogen adsorption and scanning electron microscopy. All supported HPAs were prepared by impregnation using the incipient wetness techniques with a mixture water: ethanol = 1:1. FT-IR studies showed that HPAs anions preserved their Keggin structure after deposition on pure and modified molecular sieves supports. X-ray diffraction and SEM studies confirmed the uniformity of the distribution of active phase in the supported samples. The values of specific surface area of both HPAs were increased by deposition on molecular sieve supports. It is found that most of HPM and HPVM (active phases) in supported samples are well dispersed on the support and MCM-41 supported HPAs still keep its Keggin structure. The surface morphology of the MCM-41 supported samples is almost similar to that of MCM-41 support. A relatively uniform distribution of active phase in the support pores was evidenced by EDS analysis.