Thermal stabilities of hexacarbonyl and subcarbonyls of molybdenum encapsulated in NaY and NaX zeolites

Abstract

Decompositions of Mo(CO)₆ and the resulting subcarbonyl species adsorbed on NaY and NaX zeolites have been investigated utilizing i.r., temperature-programmed decomposition and X.p.s. techniques. It was found that Mo(CO)₆ encapsulated in the NaX zeolite was considerably less stable than that contained in the NaY zeolite, while intermediate subcarbonyl species, Mo(CO)_3ads, showed a completely reversed thermal stability. The drastic difference in the stabilizing properties between X and Y zeolites is thought to result from the difference in the basic strength of the zeolite framework oxygen. The structure of Mo(CO)_3ads is proposed on the basis of i.r. spectra. The X.p.s. results suggest that the adsorbed Mo(CO)₃ species is decomposed to Mo-metal aggregates at 473 K.