| Abstract: | The desorption and reactions of propylene and propylene oxide adsorbed on atomic oxygen covered and hydroxyl covered Ag(110)
were investigated to elucidate the effect of water on the oxidation of propylene over silver catalysts. Previous studies clearly
indicate enhancement of propylene partial oxidation by the addition of water to reactor feed streams. Propylene combustion
by oxygen adatoms on Ag(110) is completely passivated by water coadsorption on the oxygen atom covered surface (water adsorption
on O-Ag(110) results in hydroxyl groups). The desorption activation energy of propylene and propylene oxide is increased by
up to 30% by adsorbed oxygen atoms on Ag(110). The desorption activation energy for propylene and propylene oxide is reduced
on the hydroxyl covered surface relative to desorption from atomic oxygen covered Ag(110). These results suggest that the
inhibition of deep oxidation plays an important role in the previously observed water enhancement. In addition, the decreased
desorption activation energies for both propylene, the reactant, and propylene oxide, the desired product, may influence the
selectivity of this complex reaction system. Potential changes in catalytic reactivity and selectivity caused by water addition
are discussed in terms of a general catalytic reaction rate law.
This revised version was published online in July 2006 with corrections to the Cover Date. |
