COLL 131 |
| Catherine Louis, Laboratoire de Réactivité de Surface, UMR 7609-CNRS, Laboratoire de Réactivité de Surface, UMR 7609-CNRS, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05, France |
| Geus and colleagues [1-3] developed a method of preparation of oxide-supported catalysts, termed deposition-precipitation. This method is a modification of the precipitation methods in solution. It facilitates to reach high metal loading and small metal particles. Ni/SiO2 has been the system the most studied with this method. It involves the precipitation of nickel onto the silica surface by gradual and homogeneous basification of the nickel salt solution. The use of urea (CO(NH2)2) was advised because basification can be controlled through urea decomposition upon heating. This avoids local supersaturations and the precipitation of nickel hydroxide in solution. The mechanism of deposition-precipitation proposed Geus et al. [3,4] based on a kinetic and thermodynamic approach will be presented. Our approach to the mechanism at a molecular level serves to explain the chemical phenomena occurring during deposition-precipitation, i.e., the fact that 1:1 nickel phyllosilicate or nickel hydroxide may be deposited on silica, depending on the silica surface area and the deposition-precipitation time. Examples of other systems will be presented, notably the preparation of Au/TiO2 catalysts. (1) Geus, J. W. Dutch Patent Applications, 1967, 6705, 259, and 1968, 6813, 236 (2) van Dillen, J. A.; Geus, J. W.; Hermans, L. A.; van der Meijden, J. Proc. 6th Int. Congr. Catal., London, 1976, p 677. (3) Hermans, L. A. M.; Geus, J. W. Stud. Surf. Sci. Catal. 1979, 3 113. (4) Geus, J. W. Stud. Surf. Sci. Catal. 1983, 16, 1. (5) Burattin, P.; Che, M.; Louis, C. J. Phys. Chem. B 1997, 101, 7060, J. Phys. Chem. B 1998, 102, 2722, J. Phys. Chem. B 1999, 103, 6171, J. Phys. Chem. B 2000, 104, 10482. |
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The Science and Engineering of Catalyst Preparation
8:30 AM-11:55 AM, Monday, March 29, 2004 Marriott -- Orange County 3, Oral
Division of Colloid and Surface Chemistry |