Detecting the Genesis of a High-Performance Carbon-Supported Pd Sulfide Nanophase and Its Evolution in the Hydrogenation of Butadiene

A new procedure for preparation of palladium sulfide nanoparticles, which are deposited and anchored over highly graphitized carbon nanofibers, is presented. The preparation method is based on the use of PdSO4 as metal precursor or alternatively in the previous functionalization of the carbon surfaces with sulfonic groups by treatment with fuming sulfuric acid. Using an in situ high-energy X-ray diffraction technique, in both cases it is demonstrated that during the reduction treatment, the initially present palladium hydride is transformed into a palladium sulfide (Pd4S). The catalytic properties of these materials have been tested in the gas-phase butadiene partial reduction to butenes. Although metallic palladium nanoparticles supported in the same carbon fibers produce butane as the principal product, the supported Pd4S nanocrystals mainly yield different isomers of butenes independently of the conversion level. Furthermore, applying the same X-ray diffraction method reveals that this catalytic phase is stable during reaction.