DRIFT STUDY OF CO CHEMISORPTION ON ORGANOMETALLICS-DERIVED PD MGO CATALYSTS - THE EFFECT OF CHLORINE/

Magnesia-supported palladium catalysts were prepared from chemical vap our deposition (CVD) of [Pd(C3H5)(C5H5)] and incipient wetness impregn ation of [Pd(C3H5)Cl](2) and [Pd(acac)(2)]. DRIFT spectroscopy of adso rbed CO on prereduced catalysts indicates that the electronic state of metal particles depends on the preparation methodology and markedly o n the organometallic precursor. Inn-heptane reforming at 500 degrees C , the highest activity and selectivity were shown by the CVD-based sys tem. Chloride ions deriving from the impregnation solvent exchange wit h surface hydroxyls. Acidic Mg-Cl sites are thus formed, which induce a beneficial effect on the catalytic properties. The reforming activit y collapsed when a chlorine-containing precursor was used, due to a pa rtial coverage of the palladium surface with chemisorbed chlorine atom s.