Sulfur Poisoning of Metals

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

“…Several excellent reviews on sulfur poisoning of transition metal catalysts are available (2,3). The susceptibility to poisoning by sulfur arises from the fact that there is a strong metal-sulfur chemisorption.…”

Adsorption of hydrogen sulphide over rhodium/silica and rhodium/alumina at 293 and 873 K, with co-adsorption of carbon monoxide and hydrogen

“…Our value of 0.6:1 S:Rh is typical for sulphur adsorption on Rh/silica [7,9], as is the *1:1 correspondence between hydrogen sulphide adsorption and carbon monoxide adsorption. Carbon monoxide adsorption over rhodium can be described by three adsorbed states, linear Rh-CO, bridge-bonded Rh 2 -CO, and gem-dicarbonyl Rh I (CO) 2 . The ratio of CO:Rh obtained with the silica catalyst suggests principally bridged and linear sites, which implies a similar bonding model for sulphur.…”

“…In this study, we have examined the adsorption of hydrogen sulphide over rhodium/silica and rhodium/alumina catalysts at 293 and 873 K. At 293 K, over Rh/silica, hydrogen sulphide adsorption capacity was similar to that of carbon monoxide; however, over Rh/alumina, the carbon monoxide adsorption capacity was higher, probably due to the formation of Rh I (-CO) 2 . Over Rh/silica, the primary adsorbed state was HS(ads), which was not the case for Rh/alumina, where the H 2 :S ratio was 1:1 indicating that the adsorbed state was S(ads).…”

“…To be able to interpret quantitatively the extent and nature of poisoning by sulphur, it is essential to know the structure and bonding of sulphur to metal atoms at the surface. There are two types of sulphides that form on a catalyst, 2-D surface sulphides and 3-D bulk sulphides, the formation of which requires the metal cation to diffuse through the adsorbed sulphide layer [2] forming a new metal sulphide layer on the outer surface. This phenomenon of segregation is strongly exothermic and is therefore favoured by a reduction in temperature.…”

Chemistry of SO 2 and DeSO x Processes on Oxide Nanoparticles

“…In addition, the SO 2 produced by the combustion of sulfur-containing fuels in automotive engines poisons the catalysts that are used for the removal of CO and NO in exhaust catalytic converters (2CO + O 2 → 2CO 2 ; 2CO + 2NO → 2CO 2 + N 2 ) (4,5). When SO 2 is present in the catalytic converter at high concentrations, it dissociates on the precious-metal component of the catalyst (Rh, Pd or Pd), blocking active sites and reducing also the overall activity of the system through medium or long-range electronic effects (6,7). At the levels of 5 to 20 ppm currently present in the typical automotive exhaust, SO 2 interacts primarily with the ceria component of the catalytic converter, and the poisoning of this oxide is a major concern nowadays (8,9,10).…”