STEAM EFFECTS IN 3-WAY CATALYSIS

Steam can exert two main effects in three-way catalysis (i) it is a reactant which can oxidize the carbon monoxide by water-gas shift and the hydrocarbons by steam reforming (ii) it is a major component of the exhaust gas which can affect significantly the thermal stability of three-way catalysts. The role of water as a co-reactant in oxidation reactions as well as its role in catalyst sintering are successively reviewed. Most investigations having been carried out with PtRh catalysts, no definite conclusion can be given as far as palladium catalysts are concerned.