Recent Advances in the Synthesis and Catalytic Applications of Pillared Clays

Abstract

New methods have been developed in recent years that are now being successfully applied in the preparation of pillared interlayered clays (PILCs). Variations in the procedures concern different parameters involved in the synthesis, such as the starting clay, the intercalating solution, the intercalation process, and the drying and calcination steps of the pillared solids, among others. In the present article, the latest results obtained when introducing modifications in the chemical aspects of PILC synthesis are reviewed. These include (1) pillaring with mixed solutions containing two or more cations, (2) using coordination or organometallic compounds, (3) using polymers and surfactants, (4) pillaring of acid-activated clays, and (5) enhancement of PILC acidity. A separate section is devoted to the specific features of preparing these solids in amounts large enough to make their manufacture on an industrial scale economically feasible. Recent developments in the catalytic applications of PILCs are also reviewed, with emphasis on the progressively more extended use of these materials as catalytic supports.

Keywords:

• Pillared clays
• Synthesis
• Catalytic supports
• Mixed pillars
• Intercalation

ACKNOWLEDGMENTS

M.A. Vicente carried out a significant portion of this work during a stay at the Laboratoire de Réactivité de Surface, Université Pierre et Marie Curie, Paris, France. Facilities given by this laboratory and by the supervisor of his stay, Dr. Jean-Francçois Lambert, are sincerely acknowledged. Financial support of the Comisión Interministerial de Ciencia y Tecnología, CICYT (ref. MAT-96-0643) is acknowledged (M.A.V.). The authors thank Professor Vicente Rives (Universidad de Salamanca) for the critical reading of the manuscript. We also sincerely thank the anonymous reviewer of this manuscript for valuable comments.