Selectivity enhancement in acetylene hydrogenation over diphenyl sulphide-modified Pd/TiO2 catalysts

Pd/TiO2 catalysts have been exposed to diphenyl sulphide to assess the impact of the modifier on the selective removal of acetylene from ethylene rich feeds. The modified catalysts show a significantly reduced rate of ethylene hydrogenation without noticeably impacting on the rate of acetylene hydrogenation. Even after reduction at 393 K, which led to the loss of the phenyl ligands, the sulphur retained by the Pd was still capable of maintaining this enhanced selectivity of the catalyst to ethylene as opposed to ethane. Results are interpreted in terms of a templating effect on the active Pd surface as a result of the original ligand adsorption pattern that creates appropriate ensembles which allow alkyne adsorption and reaction but severely limits adsorption and reaction of the alkene. A potential contribution to this enhanced selectivity by suppression of subsurface hydrogen formation cannot be discounted.