B. Gergely et al., Microcalorimetric studies of the surface reactivity of pollutant gas atmospheres on supported SnO2 and Ga2O3 catalysts, J THERM ANA, 56(3), 1999, pp. 1233-1241
The surface properties of gallium oxide and tin dioxide supported on alumin
a or titania have been studied by adsorption microcalorimetry. The differen
tial heats of adsorption of various pollutant adsorbates such as sulfur dio
xide, nitrogen monoxide, nitrogen dioxide and also ammonia were measured on
these catalytic surfaces. NH3, SO2, NO2 are strongly adsorbed while NO is
only physisorbed. The supported Ga2O3 samples show a slight decrease in aci
dity as probed by ammonia adsorption, compared to alumina or titania. The a
ddition of SnO2 decreases the number of strong acid sites but creates a few
weak and medium strength acid sites on alumina and does not modify the aci
dity of titania. In all cases, the basicity, probed by SO2 adsorption, is v
ery strongly affected by the deposition of Ga2O3 or SnO2. The differential
heats of NO2 adsorption remain nearly constant on all samples. The heats of
adsorption are discussed as a function of the coverage and of the amount o
f guest oxide.