This chapter discusses the selective oxidative dehydrogenation of butenes on ferrite catalysts. A common method for determining the existence and the densities of different active sites is selective chemisorption. A variation of the selective chemisorption technique can be used that makes use of the reactivity of the active sites. The technique is temperature programmed desorption and reaction or thermal desorption and reaction. A reactant molecule is adsorbed at low temperatures on an active site. The temperature is then raised in a controlled manner, and the evolution of the reaction products is monitored. If the various products are evolved independent of each other, they must be formed on independent sites. The separation of the two sets of desorption products may indicate that they are from different sites. As the products of the thermal desorption experiments are directly correlated with the active sites, it is possible to measure the number of active sites by measuring the quantities of desorbed products, provided that each and every active site produces only one molecule of reaction product.
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