O. Dulaurent et al., Heat of adsorption of carbon monoxide on a Ru/Al2O3 catalyst using adsorption equilibrium conditions at high temperatures, APP CATAL A, 201(2), 2000, pp. 271-279
The adsorption of CO on a reduced 3.5%Ru/Al2O3 catalyst has been studied by
means of FTIR spectroscopy between 298 and 740 K at a constant partial pre
ssure P-a=1000 Pa. At 300 K, three adsorbed species were detected on the Ru
particles: a linear CO species (strong IR-band at 2047 cm(-1)), a bridged
CO species (weak IR band at 1750 cm(-1)) and a gem-dicarbonyl species (weak
IR bands at 2135 and 2080 cm(-1)). The FTIR spectra show how the coverage
theta of the linear CO species evolves with the adsorption temperature T-a.
This cannot be achieved for the bridged CO species or for the gem-dicarbon
yl species due to the weak intensities of their IR bands. At T-a>600 K, the
curve theta=f(T-a) is in very good agreement with Temkin's adsorption mode
l. Moreover, it is shown that, in the range 300-720 K, the curve agrees wel
l with an adsorption model considering (a) an immobile adsorbed species; an
d (b) a linear decrease in the heat of adsorption with the increase in thet
a. This leads for the linear CO species to the heat of adsorption E-theta,
at various coverages theta: from E-0=175 kJ mol(-1) at theta=0 to E-1=115 k
J mol(-1) at theta=1. This procedure for the determination of the heat of a
dsorption of CO on Ru particles is simple (it requires a single isobar) and
accurate (approximate to+/-5 kJ mol(-1)). It constitutes a well adapted to
ol to study the modifications of this parameter with the method of preparat
ion of the catalyst (precursor, support, particle size). (C) 2000 Elsevier
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