The catalytic and surface properties of highly dispersed PtFe catalyst supported on SiO2 have been investigated by Mössbauer spectroscopy, chemisorption, isotope exchange, and hydrogenolysis of ethane and n-butane. At low iron concentration Mössbauer spectra indicate PtFe formation and at the same time an increase in the adsorption of H2, O2, and CO. A parallelism between adsorption properties and catalytic activity can be interpreted by an increase in the number of surface metal atoms as a result of Pt-Fe formation. This is supported by the constancy of activation energy and the selectivity change in the reaction of n-butane hydrogenolysis. At higher iron loading iron is enriched on the surface to some extent and the reaction parameters mentioned are characteristic of iron itself, i.e., activity and activation energies decreased. Since the activity of PtFe SiO2 is still higher by about three orders of magnitude than that of iron alone it is assumed that the activation of iron requires Pt neighbors by which either hydrogen can be supplied to iron sites or iron can be "diluted" thus retarding the deactivation process. These results are supported by the selectivity data.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry