ABSTRACT
The main theme of this chapter is stated as: ability of clays to concentrate molecules about to be transformed; stabilization offered to highly reactive species; fast diffusional kinetics on clay surfaces; acceleration of ionic reactions by clay polyelectrolytes; ease with which dehydrative activation can be performed. These various assets correspond to the successive stages in the following narrative. Microscopic examination shows that clay particles are highly organized. Most often, the clay platelets are stacked vertically on top of one another, in the manner of a deck of playing cards. Numerous chemical reactions that are subject to general acid catalysis can and do benefit from the high surface acidity of clays. One example is that of a cyclohexadienone-to-phenol conversion. An industrially-important case is that of the Friedel-Crafts reaction. It allows one to substitute an aromatic ring. Benzene can be turned into toluene. And toluene can be alkylated into xylenes. Unfortunately, under conditions of homogeneous catalysis, the catalyst, aluminum chloride, say, is destroyed by the secondary reaction products.
