ABSTRACT

Rhodium catalysts were synthesized (heterogenised) by hydrogen reduction at atmospheric pressure of a cationic organometallic rhodium complex in acetone medium (using [Rh(Me₂CO)_x(NBD)]ClO₄  as the metal precursor species, in which (NBD) = 2,5-norbornadiene and (Me₂CO)_x = acetone) and anchored onto modified clays: laminar and zeolitic products. The zeolitic products were synthesized under different treatment conditions and in different media, distilled water and seawater; the laminar products consisted of one pillared clay sample and homogenized montmorillonite. The rhodium catalysts were applied in the transformation of acetone. The reaction was carried out at atmospheric pressure and low temperature, after activation at different temperatures.  The effect of the structure and characteristics of the support on metal load, dispersion and catalytic behaviour was studied in the heterogeneous catalysts prepared –heterogenised Rh catalysts-. The supports were characterized by XRD, EDXRA, volumetric adsorption and surface acidity. For the precursors and catalysts, the metal load was determined by UV-VIS spectra, the reduction temperature was determined by DSC, and Rh dispersion was measured by chemisorption.

The structure of the materials used as supports had a great influence on the catalyst prepared. A higher metal content was achieved in the supports with laminar structures, while the catalysts supported on zeolitic structures showed better dispersion. Activity, selectivity and durability depend on the nature of the support used in  the preparation of  the catalyst. The acidic centres of the pillared montmorillonite favoured the formation of methylisobutylketone, whereas the other heterogeneous catalysts favoured greater selectivity towards isopropanol.