A. Caballero et al., IN-SITU EXAFS STUDIES OF MODIFICATIONS TO SUPPORTED METALLIC CATALYSTS UNDER REACTIVE ATMOSPHERES, Catalysis letters, 20(1-2), 1993, pp. 1-13
Extended X-ray absorption fine structure (EXAFS) spectroscopy has been
used to study the structural evolution of monometallic (Pt/Al2O3) and
bimetallic (Pt-Re/Al2O3) catalysts with metal loadings representative
of those used industrially under conditions close to those seen durin
g preparation (calcination and reduction), during catalysis (under a h
ydrogen-hydrocarbon mixture), and during regeneration (simulated by cy
cles of reduction and oxidation). During the catalytic reforming of n-
heptane, the formation of bonds to carbon species is observed directly
by EXAFS. Despite the fact that only platinum-carbon bonds are observ
ed, bimetallic systems show significant differences compared with mono
metallic systems with, in the case of Pt-Re, a reduction in the temper
ature range over which carbon bonding is observed, and structural modi
fications of the metallic particles. Under the same conditions, no car
bon bonding is observed for the Pt-Sn system. In the case of Pt-Sn/Al2
O3, the EXAFS results, confirmed by transmission electron microscopy,
demonstrate the high resistance to sintering of this bimetallic system
compared to the monometallic system.