FTIR STUDY OF CO ADSORPTION ON PD SIO2 AND PD-CU/SIO2 TREATED WITH SULFUR-DIOXIDE/

Infrared spectra are reported of Pd/SiO2 and Pd-Cu/SiO2 exposed at 295 K to either CO followed by SO2 or SOz followed by CO. Chemisorptive i nteraction of SO2 with bridging CO sites on Pd {100} faces created cat ionic Pd sites which adsorbed CO linearly. Multibonding CO sites on Pd {111} faces and linear CO sites were poisoned by weak non-dissociativ e SO2 adsorption, and could be regenerated by evacuation. Pd/SiO2 was more resistant than Cu/SiO2 to SO2 poisoning but for Pd-Cu/SiO2 the po isoning of Pd was promoted by the presence of Cu.