| abstract |
The invention relates to a shell catalyst having, on porous support particles, one or more metals from the group of metals comprising subgroups Ib and VIIIb of the periodic table of the elements. The shell catalyst is obtained by the following steps: at least one precursor from the group of compounds comprising metal compounds from subgroups Ib and VIIIb of the periodic table is applied to a porous support; the porous support, on which at least one precursor is applied, is then treated with at least one reducing agent. As a result, substantially mono-disperse metallic nanoparticles are obtained, which are produced in situ in the pores of the support. The thickness of the shell of the shell catalyst is > 5 mu m. According to this method, metallic compounds, preferably metal salts, placed in the pores of the support, are reduced by a reducing agent, preferably in the presence of stabilizers, giving noble metal colloids with an average particle diameter of 1-100 nm. Shell catalysts thus produced, in particular Pd/Au shell catalysts, are used to advantage in the synthesis of vinyl acetate. |