Clays have long been used as catalysts [1] and they retain a continuing important role since they constitute the matrix of many industrial catalysts based on zeolites. Intercalated clays are a new class of materials, in which an homogeneous distribution of micropores can be obtained with pore openings varying from 4 Å to 18 Å according to the type of pillars. These solids are then attractive because they can adsorb and convert large molecules.