A catalyst for the selective oxidation of hydrocarbons to unsaturated aldehydes, acids, acid anhydrides, divinyls, or styrenes has to perform several functions. First, it must supply a limited amount of oxygen to the reactant, sufficient to allow the formation of the desired product but not enough to allow complete oxidation. Further, it must provide appropriate sites for the adsorption of the hydrocarbons in deformed, reactive states. Last, the catalyst should be capable of transferring electrons from and to the reactants. These three demanding characteristics of an active catalyst impose severe limitations on the systems that can effectively perform selective oxidation reactions. Therefore catalyst selectivity, normally measured by the rate of formation of the specific product relative to that of undesired products, is sensitive to reaction conditions (temperature, feed rate, feed composition, and reactor design) and is very dependent on the details of the structure of the catalyst itself, its ...

Selective oxidation of hydrocarbons on composite oxides

Publisher Summary 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.

F.E. Massoth

Papers

Catalyst characterization studies on the ZnCrFe oxide system