NOVEL MICROFABRICATED PD-AU SIO2 BIMETALLIC MODEL CATALYSTS FOR THE HYDROGENATION OF 1,3-BUTADIENE/

Model Pd-Au/SiO2 bimetallic catalysts were prepared via a microfabrica tion method and their catalytic activity for the hydrogenation of 1,3- butadiene was compared with thin film catalysts. The microfabricated c atalyst consisted of Pd-Au squares with various surface compositions, approximately 4 mu m in size and separated by 4 mu m on a silica/silic on support. The main advantage of the microfabricated bimetallic catal ysts is that alloy formation is guaranteed and XPS results showed that surface segregation occurred for the Au-rich compositions. The appare nt activation energies of the bimetallic catalysts were lower than tha t of the pure Pd catalyst with a minimum occurring at similar to 65 at % Pd. The bimetallic catalysts, however, have fewer active Pd sites, h ence the conversions are comparable. The microfabricated catalysts wer e more active than the thin film samples, because the thin film sample s showed evidence of a high degree of sintering after pretreatment, un like the microfabricated catalysts in which sintering did not occur.