Catalytic Activity of ZnS Formed from Desulfurization Sorbent ZnO for Conversion of COS to H2S

“…19 The reactions between ZnO and reformate gas, a mixture of H 2 , CO, CO 2 , water, low molecular-weight hydrocarbons and trace amounts of sulfur species such as H 2 S and COS, are rather complex. The interaction between ZnO and a reformate stream at 500 1C was studied by Sasaoka et al 19,22,23 Besides the already mentioned inhibition of the sulfidation reaction in the presence of water, they found that most of COS converts to H 2 S, while a part of the COS reacts directly with ZnO and forms ZnS. 22 The ZnS on the ZnO surfaces, in addition, accelerates the COS conversion to H 2 S. 23 Up to now there have been only a few theoretical studies on the atomistic interaction of H 2 S with ZnO surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…The interaction between ZnO and a reformate stream at 500 1C was studied by Sasaoka et al 19,22,23 Besides the already mentioned inhibition of the sulfidation reaction in the presence of water, they found that most of COS converts to H 2 S, while a part of the COS reacts directly with ZnO and forms ZnS. 22 The ZnS on the ZnO surfaces, in addition, accelerates the COS conversion to H 2 S. 23 Up to now there have been only a few theoretical studies on the atomistic interaction of H 2 S with ZnO surfaces. Most of them have focused on the polar Zn-terminated (0001) surface.…”

Section: Introductionmentioning

confidence: 99%

“…In a second step the coverage dependence of H 2 S adsorption will be considered and the thermodynamic stability of different surface coverages will be analyzed as a function of the H 2 S chemical potential. Finally, since ZnS formation upon H 2 S adsorption has been observed, 23 the incorporation of sulfur atoms into the ZnO surface will be investigated. These results will provide new insights into the adsorption properties of H 2 S on ZnO that are important for a further improvement of the existing ZnO-based catalysts for desulfurization processes.…”

Section: Introductionmentioning

confidence: 99%

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The interaction of H2S with the ZnO(101̄0) surface

Goclon¹,

Meyer²

2013

Phys. Chem. Chem. Phys.

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Using density functional theory with and without Hubbard-U correction we have calculated the geometric structure and the binding energy of H2S molecules adsorbed on the main cleavage plane of ZnO. We find that H2S molecules preferentially dissociate upon adsorption, with a negligible barrier for the first and an activation energy of about 0.5 eV for the second SH bond dissociation. In the low coverage limit of individual molecules single and double dissociation are energetically almost degenerate. At higher coverage double dissociation is favored because of attractive adsorbate-adsorbate interactions. Thermodynamic analysis shows that the double-dissociated state at full saturation with a coverage of 1/2 monolayer is the most stable adsorbate structure for a wide range of temperatures and partial pressures. However, at high H2S chemical potential a full monolayer of single-dissociated H2S becomes thermodynamically more favorable. In addition, at low temperature this structure may exist as a metastable configuration due to the activation barrier for the second SH bond cleavage. Finally we show that it is thermodynamically favorable for adsorbed H2S to react with the first ZnO surface layer to form ZnS and water.

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“…The former could be catalyzed by the formed ZnS and ZnO nanoparticles [37,38]. The dominant role of the homogenous reactions (7) and (8) in Test 2 is accounted for by the fact that the high density of H 2 S and H 2 O molecules is maintained in the reactor up to the end of the reaction (Table 1).…”

Section: Participation Of Cs and Cs 2 Molecules In Zinc Sulfidationmentioning

confidence: 99%