Stability of ruthenium catalysts supported on TiO_2 or ZrO_2 in catalytic wet air oxidation

摘要

The stability of ruthenium catalysts supported onTiO_2 and ZrO_2 were studied in the wet air oxidation of aqueous solution of succinic and p-hydroxybenzoic acids taken as model effluent and on real effluents from the paper-pulp industry.Catalyst recycling experiments were conducted in batch reactor and long-term stability tests were conducted in trickle-bed reactor.In all experiments,ruthenium and support materials were perfectly stable to leaching,sintering and fouling.Ruthenium catalysts experienced a weak deactivation as they were exposed to air,e.g.,in recycling experiments however the loss of activity occurred only after the first exposure and was completely reversible upon catalyst reduction.The deactivation was attributed to an over-oxidation of the catalyst surface particularly noticeable in the case of very small Ru-clusters(1 nm).