Abstract
The present work deals with the catalytic performance of a series of supported niobium oxide (1–12wt% Nb2O5) catalysts in the gas phase dehydration of glycerol. The niobium species were supported on a mesoporous zirconium doped silica (Si/Zr molar ratio of 5) by incipient wetness impregnation. The catalysts were characterized by means of XRD, N2 adsorption, NH3–TPD, Raman spectroscopy, adsorption of pyridine coupled to FTIR spectroscopy and XPS. The catalytic reaction was carried out in gas phase at 325°C. The support exhibits the highest glycerol conversion (91mol%) after 2h, but it is less selective to acrolein (25mol%). The supported niobium species do not ameliorate the glycerol conversion, but the acrolein selectivity is markedly improved, attaining a value of 45mol% after 2h for the catalyst with 8wt% of Nb2O5. This catalyst can be regenerated by thermal treatment under an air flow for 4h, although the regeneration causes a lowering of the Brönsted/Lewis acid sites ratio, thus decreasing the selectivity toward acrolein.
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