Clays and catalysis: a promising future

The main properties of cationic and anionic clays as well as their role in catalysis are discussed in light of the versatility and potential of these materials. Clays exhibit specific features such as high versatility, wide range of preparation variables, use in catalytic amounts, ease of set-up and work-up, mild experimental conditions, gain in yield and/or selectivity, low cost, etc., which may be very useful tools in the move towards establishing environmentally friendly technologies. Furthermore, the possibility of upgrading these materials by the pillaring process opens new and interesting perspectives, also considering possible shape selective advantages. Recent catalytic applications of cationic and anionic clays in organic or fine chemistry (acid- or base-catalyzed reactions, Diels-Alder reactions, reactions using metallic nitrates, etc.), environmental catalysis (DeSOx, DeNOx or contaminant oxidation) and energy exploitation (partial oxidation of methane) are discussed as very promising research subjects with a wide range of possible future developments. (C) 1999 Elsevier Science B.V. All rights reserved.