Stable mono and bimetallic nanoparticles have been prepared from colloids developed by a simple and reproducible method, based on a reduction-by-solvent process. This method allows for the preparation of metallic nanoparticles with different compositions (i.e., Ni-Pd, Fe-Pd, Mg-Pd, Pd, and Pt) and metallic ratios, and an average size of about 2 nm. Purified and nonpurified metallic species were used in the selective hydrogenation of phenylacetylene to styrene in liquid phase under very mild conditions (1 bar H-2 pressure and T = 50 degrees C. The catalysts prepared show high selectivity and activity toward styrene at very high loadings of phenylacetylene (substrate-to-catalyst weight ratio near 7500). Therefore, these materials are highly interesting as selective hydrogenation catalysts for reactions of great industrial importance. (c) 2006 Elsevier Inc. All rights reserved.