The molecular mechanism of low-temperature decomposition of hydrogen sulfide under conjugated chemisorption-catalysis conditions

The Reaction Mechanisms of H2S Decomposition into Hydrogen and Sulfur: Application of Classical and Biological Thermodynamics

“…The second step -dissociative chemisorption of two H 2 S molecules on two adjacent cobalt atoms ( Figures 2 and 4 [16,17]. It is significant that, in the adsorbed state, two H 2 S molecules interact to one another, as is indicated by their coming together within a short distance of 2.18 Å of each other ( Figure 4).…”

“…In the absence of occluded hydrogen, H 2 S molecule is not adsorbed by a Co(II) or Ni(III) atom with d 7 electron configuration, because the 3d z2 orbital is occupied. The molecular H 2 S adsorption on the d 6 Co(III) ion is an exothermic process (∆H 298 =-12.7 kcal/mol) and occurs spontaneously (∆G 298 =-0.8 kcal/mol) [16,17], while H 2 S adsorption on the d 7 Co(II) ion is hardly possible (∆H 298 =-2.2 kcal/mol, ∆G 298 =+6.6 kcal/mol).…”

“…Actually, the adsorption energy of S 2 species on runs also spontaneously at room temperature (∆H 298 =-23.0 kcal/ mol, ∆S 298 =-53.2 cal/mol. K, ∆G 298 =-7.2 kcal/mol [16,17]) ( Figure 5). Removal of adsorbed sulfur from the catalyst surface can be realized by immersing solid catalyst into liquid solvent (see next sections).…”

“…This coupled reaction is the highly exothermic process and occurs spontaneously (∆H 298 =-78.4 kcal/mol, ∆S 298 =-116.0 cal/mol. K, ∆G 298 =-43.6 kcal/mol [16,17]). Therefore, the overall catalytic reaction: …”

Chemisorption of H2S on Copper-ETS-2: Experiment and Modeling of a Packed Column

“…16 17 Cu-ETS-2 displayed the most promising adsorbent in comparison to a fully developed commercial H 2 S adsorbent and other tested metal-exchanged ETS-2. Also, Cu-ETS-2 has the chemical environment favorable for decomposition of H 2 S. Since it has been shown that a transition-metal ion, [18][19][20][21][22][23] metal oxides 24 and TiO 2 surface 25 enhance H 2 S adsorption by facilitating its dissociation to HS − and S − ions, which may further react and form sulfide products. 26 Although several studies focused on the development of H 2 S sorbents at low temperatures and measurements of the * Author to whom correspondence should be addressed.…”