Re. Lakis et al., ALUMINA-SUPPORTED PT-RH CATALYSTS .2. KINETIC CHARACTERIZATION AND SYNERGISTIC EFFECTS, Journal of catalysis, 154(2), 1995, pp. 276-287
Analytical electron microscopy was used in the preceding paper to dete
rmine the composition distribution of individual catalytically active
particles on several supported Pt-Ph bimetallic catalysts. The kinetic
performance of these catalysts for the reduction of NO with H-2 and t
he reduction of NO with CO between 25 and 300 degrees C is presented h
ere. The performance of one catalyst that contained alloy particles wi
th compositions centered at approximately 10 wt% Pt and 90 wt% Pt was
intermediate to that observed for Pt and Rh monometallic catalysts. Ad
ditional catalysts were prepared to separately test the kinetic perfor
mance of Pt-rich and Rh-rich alloy particles. One catalyst that was pr
epared at a 95/5 weight ratio of Pt to Rh contained Pt-rich alloy part
icles in the composition range of 80 wt% Pt-100 wt% Pt. Another cataly
st was prepared at a 17/83 weight ratio of Pt to Rh and contained most
ly Rh-rich alloy particles in the composition range of 70 wt% Rh-100 w
t% Ph. For both the NO-H-2 and NO-CO reactions, the 95/5 catalyst disp
layed an activity greater than that expected from the sum of the alloy
components. It is therefore concluded that for the Pt-rich alloy part
icles of the 95/5 catalyst, a synergistic effect due to particle alloy
ing is present. The kinetic performance of the Rh-rich particles in th
e 17/83 catalyst was less favorable, and less than that expected from
the sum of the alloy components for the NO-CO reaction. (C) 1995 Acade
mic Press, Inc.