|Search for content and authors|
Boehmite Synthesis by Aqueous Precipitation using Organic Complexing Agents to Control Nanoparticle Morphology: Toward Enhanced γ-Alumina Catalyst Supports
|David Chiche 1,2, Corinne Chanéac 1, Renaud Revel 2, Mathieu Digne 2, Jean-Pierre Jolivet 1|
1. Chimie de la Matiere Condensee de Paris UPMC (CMCP-UPMC), 4 place jussieu, Paris 75252, France
Transition aluminas, and especially the gamma type, are largely used as catalyst supports in refining and petrochemicals. Most studies focus on properties resulting from material texture and casting (specific surface, porous volume, pore shape and diameter). However, surface properties of alumina should be considered as well, as the catalytic activity is tightly related to the structure of exposed crystalline faces. As γ-alumina results from controlled thermal treatment of boehmite γ-AlOOH by a topotactic transformation, the nature of exposed crystalline planes is related to the starting material. Therefore, the synthesis of the oxihydroxide γ-AlOOH, and especially size and shape of these particles, is critical in determining the relevant surface properties.
We present an innovating way to control morphology of boehmite nanoparticles synthesized by soft chemistry routes. The use of organic complexing agents such as polyols, carboxylates, and hydroxycarboxylates during synthesis causes a modification of usual morphologies observed, specifically resulting in an observed increase of (101) faces (from 45% without complexing agent to 65% in the presence of tartrate). For instance in the case of polyols, we show that the variation of nanoparticles aspect ratio depends on polyol carbon chain length and stereochemistry.Material characterizations were performed using novel methods such as x-ray diffraction powder pattern simulation and zetametry in addition to transmission electron microscopy. Crystal growth mechanisms were investigated through adsorption isotherms, solid-state NMR spectroscopy and molecular simulation. We will also present our first results concerning catalytic properties of γ-alumina synthesized from these boehmite materials. Finally, we expect that this method will provide a promising way for the design of γ-alumina catalyst supports.
Presentation: Oral at E-MRS Fall Meeting 2007, Symposium A, by David Chiche
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-14 11:16 Revised: 2009-06-07 00:44