Nature of the active sites of Mo-containing zeolites. XANES studies at Mo K and L_III –edges.

摘要

Zeolites Na-MFI, Na-MEL and Na-BEA prepared by sol-gel procedure and Mo/H-Zeolitesrnobtained by incipient wetness impregnation of an aqueous solution of ammoniumrnheptamolybdate using ammonium form of the above cited zeolites at low Mo loading,rnallowed as to obtain the special Mo-containig zeolites with Mo in specific geometricrnenvironment. Due to the splitting at Mo L_3-edges obtain by XANES, Mo atoms are mainly inrntetrahedral surrounding in Mo-MFI, Mo-MEL and Mo-BEA samples. Linear XANES fitrnprovide information about concentration of Mo-sites related with their Mo-coordination.rnDifferences between linear XANES fits at L_3 and K-edges can be attributed to differentrnmeasurement conditions, indicating different kind of Mo-sites according their hydrationrncapability.