Quantitative Differences in Sulfur Poisoning Phenomena over Ruthenium and Palladium: An Attempt To Deconvolute Geometric and Electronic Poisoning Effects Using Model Catalysts

Sulfur poisoning over noble-metal catalysts has traditionally been regarded as very complex and precluding from easy rational understanding, because of the problems of interference from using different supports, inability of controlling coverage due to nonuniform metal particle size, intrinsic size/shape effect of metal component, etc. Here, high-quality polyvinylpyrrolidone (PVP) polymer-supported ruthenium and palladium model nanocatalysts using without solid support are equivalently modified with preadsorbed mercaptoethanol over a range of surface concentrations in order to compare sulfur poisoning effects on the two important noble metals commonly used in industry. A typical consecutive hydrogenation reactions of alkyne to alkene and then to alkane is studied under mild reaction conditions in the liquid phase. The first stage alkyne hydrogenation is well-known to be surface insensitive, because of strong adsorption of alkyne on both metals. However, the second stage, surface-sensitive hydrogenation/is...