Bimetallic sulfided cluster catalysts for CO hydrogenation

Sulfided, bimetallic clusters Cp/sub 2/Mo/sub 2/Fe/sub 2/(CO)/sub 8/ and Cp/sub 2/Mo/sub 2/Co/sub 2/S/sub 2/(CO)/sub 4/ were prepared and deposited onto alumina. These clusters are extremely robust due to strong metal-metal bonds and the presence of bridging sulfide groups. According to infrared spectroscopic data, anchoring of these clusters on Al/sub 2/O/sub 3/ supports causes only minimal structural perturbation. Upon heating, the clusters readily lose CO and other hydrocarbon fragments stemming from the cyclopentadienyl ligands. The cluster-derived sulfided bimetallic catalysts exhibit remarkable behavior under CO hydrogenation conditions. During an induction period lasting several hours a typical Anderson-Schulz-Flory hydrocarbon product distribution is obtained. Then, the CO conversion increases into a new steady state activity accompanied by a dramatic shift in product distribution. Now, dimethylether appears as the main product besides methane. It should be noted that supported clusters quite frequently show an initial product distribution distinct from conventionally supported catalysts. In the case described here, however, the unique product distribution was sustained at steady state for hundreds of hours on stream and was reproducible over more than ten regeneration cycles