Microcalorimetric studies of the surface reactivity of pollutant gas atmospheres on supported SnO2 and Ga2O3 catalysts

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.