Interaction of polyols with ruthenium metal surfaces in aqueous solution

Abstract

The irreversible adsorption and decomposition of glycerol and other polyhydric alcohols over ruthenium metal at 298–353 K has been examined in a recirculating microreactor system. The quantity of glycerol (GO), propylene glycol (1,2-propanediol, herein PG), ethylene glycol (EG), or 1,3-propanediol (1,3-PDO) adsorbed on a reduced and evacuated bulk Ru metal powder at saturation is 0.8 ± 0.2 μmol/g, a value approximately one-tenth that of CO adsorbed (9.0 μmol/g) on the same material. The quantity of polyol adsorbed is independent of temperature, but is strongly affected by the condition of the Ru surface—saturating the metal surface with hydrogen prior to exposure to the polyol significantly reduces the quantity of polyol adsorbed. When they are present together in solution, GO adsorbs more readily than PG, to the point of excluding PG from adsorbing when excess GO is present. Removal of adsorbed species in their original form by heating or flushing with water is not possible, but all carbon is accounted for as desorbed methane when the Ru catalyst is heated under hydrogen.