Design of surface sites for the selective hydrogenation of 1,3-butadiene on Pd nanoparticles: Cu bimetallic formation and sulfur poisoning

Modifications to the selectivity during partial hydrogenation of butadiene over graphite supported Pd nanoparticle catalysts may be achieved by at least three methodologies: (1) by changing the structure of the surface ensembles that constitute the active surface sites by the incorporation of another metallic component, such as Cu in the present case, (2) by self-poisoning of the surfaces by strongly adsorbed carbonaceous intermediates, or carbon deposits, which are very sensitive to the presence of excess hydrogen in the feed during reaction, and (3) by anchoring a sulfur containing compound over the Pd surfaces. A detailed analysis of the selectivity variations yielding 1-butene, cis- or trans-2-butene and undesired butanes is presented in these three cases, and the catalytic data are related to the characterization data of these materials; transmission electron microscopy was used to determine the size of the nanoparticles and X-ray photoelectron spectroscopy to obtain the surface analysis composition. The latter indicates that some electronic modifications on Pd take place.