ABSTRACT
The active sites on a heterogeneous catalyst are found on its surface. The most efficient catalysts usually have a large catalytically active surface area exposed to the reaction medium. One way of maximizing the active surface of a catalyst is for it to be present as a very fine powder. However, heating powdered catalysts usually results in sintering or the agglomeration of the small particulates into larger, less efficient, entities. The extent of agglomeration is a function of the particular catalyst, the temperature and the time the catalyst is exposed to the heat. The environment of the dispersed catalyst particulates in these supported catalysts is influenced by a number of factors, primarily the relative amount of catalytically active material present, the nature of the support and the strength of the interaction between the support and the catalyst particles. Except for this interplanar area, graphite particles are essentially non- porous and thus, graphite is not commonly used as a catalyst support.
