INFLUENCE OF THE PRECURSOR AND THE SUPPORT ON THE CATALYTIC PROPERTIES OF RUTHENIUM FOR ALKANE HYDROGENOLYSIS

The influence of the ruthenium compound used as precursor to prepare ruthenium catalysts, and of the carrier, have been investigated using the hydrogenolysis of n-hexane, 2-methylpentane and 2,2,3,3-tetramethylbutane as model reactions. Similar activities and selectivities are reproduced for catalysts obtained from Ru(NH3)6Cl3 or Ru(acac)3 and a highly crystalline alumina. When RuCl6(NH4)2 is used as precursor, the catalytic properties are shifted towards those of large particles. At similar dispersions, the catalysts obtained by deposition of Ru(acac)3 on Al2O3, MgO or TiO2 (reduced at 573 K) present similar properties. By high-temperature reduction of the Ru/ TiO2 sample, the hydrogen chemisorption decreases, but the specific activity of surface ruthenium atoms is not changed, activation energies for hydrogenolysis decrease and selectivities are shifted towards those of smaller particles. The SMSI effect on Ru/TiO2 cannot be reduced to a simple dilution of the ruthenium surface by titanium species. © 1990.