Synthesis, characterization, electronic structure and catalytic performance of bimetallic and trimetallic...

When anchored on a high-area, siliceous supports, nanoparticle catalysts, consisting of two or three different metals, but totaling no more than twenty atoms in all, exhibit exceptional activities and selectivities in solvent-free, one-step hydrogenation reactions at low temperatures (< 420 K) and much lower pressures (e.g. 30 bar) than those required in current industrial manufacture. The two selective hydrogenations illustrated here are the conversion of (a) cyclododecatriene (CDT) to cyclododecene (CD) and (b) dimethyl terephthalate (DMT) to cyclohexane dimethanol (CHDM); each of these products is extensively used in the polymer industry. All our mixed-metal nanoparticles are derived from an appropriately chosen parent (precursor) mixed-metal carbonyl having phenyl-containing tin ligands, e.g. Ru4(mu4-SnPh)2(CO)12. Various techniques are used to characterize the denuded, anchored cluster catalysts; and it is expected that aberration-corrected high-resolution electron microscopy (and other techniques, which are outlined) will be invaluable in such characterization. Density functional theory has provided important insights into the structures and electronic properties of our catalysts and their precursors.