Study of iron oxide surface by adsorption and temperature-programmed desorption

Catalytic sites on an iron oxide surface, active in the selective oxidation of butene to butadiene, were studied by adsorption and temperature-programmed desorption of cis-2-butene, butadiene, and carbon dioxide. Three distinct types of sites were identified: isomerization site, selective oxidation site, and combustion site. Results indicate that the three sites are independent of each other. Interaction of hydrocarbons was the weakest with the isomerization site, and strongest with the combustion site. Desorption from the oxidation sites can be identified. By quantitatively determining the desorption products in the adsorption of cis-2-butene and butadiene, concentrations of the selective oxidation and the combustion sites were estimated.