Sol-Gel Synthesis of Supported Metals

The next step in the synthesis of supported metal catalysts via dendrimers is the immobilization of dendrimer-metal nanocomposites onto a solid support. An array of techniques exists for achieving this task. Wet impregnation and sol-gel incorporation of dendrimer-metal nanocomposites may lead to strongly adhered metal particles. Other techniques, such as functionalization of the support to facilitate dendrimer growth or adhesion, provide a route for deposition of empty dendrimers that can subsequently undergo complexation with metal precursors to form dendrimer-metal complexes and eventually zerovalent nanoparticles. Whereas the complexation and reduction phases of catalyst synthesis via dendrimers can be fairly complicated, most methods of dendrimer deposition are rather straightforward. 

Our research conducted at Cincinnati have been primarily focused on sol-gel synthesis of alumina, zirconia, titania and silica. These metal oxides not only are commonly used as adsorbent or catalyst support but also have recently emerged as excellent materials for ceramic membranes. The objective of this article is to report synthesis and properties of these sol-gel derived adsorbent materials with emphasis on development of a sol-gel granulation method and the properties of the sol-gel derived granular adsorbents. 

Kaiser A., Gorsmann C., Schubert U. Influence of the metal complexation on size and composition of Cu/Ni nano-particles prepared by sol-gel processing. J. Sol-Gel Sci. Technol. 1997 8 795-799 Kaneko E.Y., Pulcinelli S.H., da Silva V.T., Santilli C.V. Sol-gel synthesis of titania-alumina catalyst supports. Appl. Catal. A Gen. 2002 235 71-78... 

Pratap T. Patil, A. Dimitrov, J. Radnik and E. Kemnitz, Sol-gel synthesis of metal fluorides supported Pd catalysts for Suzuki coupling, J. Mater. Chem., 18,1632 1635 (2008). 

In an effort to confront these deficiencies, we have developed a procedure for the surface derivatization of small glass (sol-gel) [41] pellets and applied it to the synthesis of supported Ru catalysts [42]. As shown in Scheme 11.8, the Unker and the active metal carbene were installed in a sin e step. Treatment of (71) with allylchlorodi-methylsilane and a full equivalent of (4,5-dihydroIMES)PCy3Cl2Ru=CHPh (29) led to rapid ROCM and metaUation of the styrenyl ether (-> 72). Preweighed monolithic (smallest dimension > 1 mm) sol-gels were then added to the solution, and substi-... 

Regarding preparation procedures, the grafting of metal alkoxides on surface hydroxy groups, the co-precipitation procedure and sol-gel synthesis can lead to systems where the mixed oxides can be either close to a classical supported impregnated oxide (for sub-monolayer coverages) or close to solid solutions or multi-layered supported oxides. So the frontier between supported oxides and mixed oxides cannot be well defined. 

Our research group has studied the effect of using platinum salts in the synthesis of mesoporous silica with a view to the preparation of Pt-supported silica solids [11], which possess a high catalytic potential. In addition, this methodology could be extended to the synthesis of other metals supported on alternative materials compatible with the sol-gel route. 

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