CS2 poisoning of size-selective cubooctahedral Pd particles in styrene hydrogenation

The poisoning effect of carbon disulfide on cubooctahedral palladium nanoparticles (1.5, 3.0 or 4.6 nm in mean diameter) deposited on montmorillonite was investigated in the liquid-phase hydrogenation of styrene to ethylbenzene under mild conditions. The dispersion of the metal crystallites was computed as a function of the mean diameter in terms of face atoms, of edge atoms + corner atoms, and of the total number of exposed surface atoms. A linear relationship was found between the rate of hydrogenation and the fraction of low-coordination surface sites poisoned, independently of particle size, and hydrogenation ceased when these sites were quantitatively covered by poison molecules with a nominal stoichiometry of CS2:Pd = 1:2. High-coordination terrace sites are not involved in the hydrogenation reaction.