HYDROGEN CHEMISORPTION ON POTASSIUM-PROMOTED SUPPORTED RUTHENIUM CATALYSTS

The interaction of hydrogen on potassium promoted catalysts prepared b y both sequential and co-impregnation methods was studied by proton NM R spectroscopy. Potassium addition decreased the amounts of both hydro gen adsorbed on the metal (site blocking) and the support hydroxyl gro ups. No evidence for a ruthenium-mediated (through-metal) electronic i nteraction between potassium species and adsorbed hydrogen was found. During catalyst preparation, potassium was incorporated on the support by an exchange with the Si(OH) groups forming Si(OK) species, thereby reducing the amount of surface silanol protons. The sequential impreg nation technique proved to be more efficient in depositing potassium o n the metal surface. (C) 1994 Academic Press, Inc.