Ruthenium surface compounds supported on silica gel .1. Preparation and catalytic properties

In analogy to Phillips catalysts coordinatively unsaturated surface compounds of ruthenium were prepared and their catalytic potential was tested. The impregnated catalysts (RuCl3.3H(2)O adsorbed on silica gel) were activated either under oxygen (200 degrees C-600 degrees C) or under vacuum (250 degrees C-800 degrees C) and reduced with CO(250 degrees C-35 degrees C). These catalysts show activity with respect to the hydrogenation of olefins (e.g., octenes and cyclooctene) as well as to their isomerization under normal and elevated pressures. The properties of the catalysts depend on the conditions of their preparation. The activity generally increases with increasing activation temperature. The IR spectra of the catalysts activated at temperatures lower than 300 degrees C reveal the presence of carbonyl surface complexes. Their catalytic properties are relatively poor. The catalyst with the best hydrogenation activity was activated at 800 degrees C under vacuum and reduced at 350 degrees C by CO. The IR spectrum shows no CO absorption bands in the carbonyl region after preparation; however, the catalyst reversibly adsorbs carbon monoxide readily at room temperature and two carbonyl bands appear at 2130 and 2070 cm(-1). This indicates the presence of unsaturated ruthenium species on this catalyst in oxidation states > 0. In the absence of hydrogen an isomerization of 1-octene was observed at elevated temperatures (90 degrees C). Reaction mechanisms are proposed for both cases.