Promotion of Pd nanoparticles by Fe and formation of a Pd 3 Fe intermetallic alloy for propane dehydrogenation
In this study, silica supported Pd (~2 nm), Pd 3 Fe (~2 nm) and Pd 3 Fe_large (~12 nm) catalysts were synthesized and tested for propane dehydrogenation at 510 °C. At the 10% conversion, Pd and Pd 3 Fe catalysts exhibited propylene selectivity of 45% and 94%, respectively. Moreover, the latter showed a turnover rate (TOR) of 0.2 s -1 , which is five times higher than that of the Pd catalyst (0.04 s -1 ). Pd K edge XAS, XRD, and CO adsorbed IR were used to characterize the geometric structure of the catalysts. By combined comparison of XRD and XAS spectra of Pd 3 Fe and Pd 3 Fe_large catalysts, we successfully identified the crystalline phase in the 2 nm Pd 3 Fe catalyst. The CO adsorbed IR suggests that the formation of Pd 3 Fe breaks the ensemble of Pd, which is responsible for the increase of selectivity. The Pd L edge XAS was used to characterize the electronic structure of the catalysts. The Pd 3 Fe catalyst exhibits an increase of the edge energy compared with the Pd catalyst, which indicates the change of d-band structure in the bimetallic catalyst. The change in the electronic structure is likely the reason for the increase in TOR.