Surface investigation on thermal stability of tungstophosphoric acid supported on MCM-41 using synchrotron radiation Original Research Article

The surface of supported tungstophosphoric acid H3PW12O40 (HPW) on all-silica MCM-41 has been investigated using high-resolution X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES). The results show the interaction between HPW and MCM-41 upon impregnation. Nuclear magnetic resonance (NMR) spectroscopy results also seem to confirm the above conclusion. Heating the supported acid increased the structural damage of HPW and MCM-41. Our results also suggest the formation of tungsten oxides on the surface upon heat treatment at 400 °C.A detailed analysis of the infrared (IR) spectra showed a gradual increase in the absorbance of the WOW corner shared vibration relative to the absorbance of the other bands. This indicates that the symmetry, and hence the stability of the bulk molecules were also decreased upon heating.