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New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth.
Phys Chem Chem Phys. 2013 Feb 07; 15(5):1532-45.PC

Abstract

Zinc oxide based materials are commonly used for the final desulfurization of synthesis gas in Fischer-Tropsch based XTL processes. Although the ZnO sulfidation reaction has been widely studied, little is known about the transformation at the crystal scale, its detailed mechanism and kinetics. A model ZnO material with well-determined characteristics (particle size and shape) has been synthesized to perform this study. Characterizations of sulfided samples (using XRD, TEM and electron diffraction) have shown the formation of oriented polycrystalline ZnS nanoparticles with a predominant hexagonal form (wurtzite phase). TEM observations also have evidenced an outward development of the ZnS phase, showing zinc and oxygen diffusion from the ZnO-ZnS internal interface to the surface of the ZnS particle. The kinetics of ZnO sulfidation by H(2)S has been investigated using isothermal and isobaric thermogravimetry. Kinetic tests have been performed that show that nucleation of ZnS is instantaneous compared to the growth process. A reaction mechanism composed of eight elementary steps has been proposed to account for these results, and various possible rate laws have been determined upon approximation of the rate-determining step. Thermogravimetry experiments performed in a wide range of H(2)S and H(2)O partial pressures have shown that the ZnO sulfidation reaction rate has a nonlinear variation with H(2)S partial pressure at the same time no significant influence of water vapor on reaction kinetics has been observed. From these observations, a mixed kinetics of external interface reaction with water desorption and oxygen diffusion has been determined to control the reaction kinetics and the proposed mechanism has been validated. However, the formation of voids at the ZnO-ZnS internal interface, characterized by TEM and electron tomography, strongly slows down the reaction rate. Therefore, the impact of the decreasing ZnO-ZnS internal interface on reaction kinetics has been taken into account in the reaction rate expression. In this way the void formation at the interface has been modeled considering a random nucleation followed by an isotropic growth of cavities. Very good agreement has been observed between both experimental and calculated rates after taking into account the decrease in the ZnO-ZnS internal interface.

Authors+Show Affiliations

IFP Energies nouvelles, Rond-point de l'échangeur de Solaize, BP 3, 69360 Solaize, France.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

23238352

Citation

Neveux, Laure, et al. "New Insight Into the ZnO Sulfidation Reaction: Mechanism and Kinetics Modeling of the ZnS Outward Growth." Physical Chemistry Chemical Physics : PCCP, vol. 15, no. 5, 2013, pp. 1532-45.
Neveux L, Chiche D, Pérez-Pellitero J, et al. New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth. Phys Chem Chem Phys. 2013;15(5):1532-45.
Neveux, L., Chiche, D., Pérez-Pellitero, J., Favergeon, L., Gay, A. S., & Pijolat, M. (2013). New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth. Physical Chemistry Chemical Physics : PCCP, 15(5), 1532-45. https://doi.org/10.1039/c2cp42988h
Neveux L, et al. New Insight Into the ZnO Sulfidation Reaction: Mechanism and Kinetics Modeling of the ZnS Outward Growth. Phys Chem Chem Phys. 2013 Feb 7;15(5):1532-45. PubMed PMID: 23238352.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth. AU - Neveux,Laure, AU - Chiche,David, AU - Pérez-Pellitero,Javier, AU - Favergeon,Loïc, AU - Gay,Anne-Sophie, AU - Pijolat,Michèle, PY - 2012/12/15/entrez PY - 2012/12/15/pubmed PY - 2013/6/5/medline SP - 1532 EP - 45 JF - Physical chemistry chemical physics : PCCP JO - Phys Chem Chem Phys VL - 15 IS - 5 N2 - Zinc oxide based materials are commonly used for the final desulfurization of synthesis gas in Fischer-Tropsch based XTL processes. Although the ZnO sulfidation reaction has been widely studied, little is known about the transformation at the crystal scale, its detailed mechanism and kinetics. A model ZnO material with well-determined characteristics (particle size and shape) has been synthesized to perform this study. Characterizations of sulfided samples (using XRD, TEM and electron diffraction) have shown the formation of oriented polycrystalline ZnS nanoparticles with a predominant hexagonal form (wurtzite phase). TEM observations also have evidenced an outward development of the ZnS phase, showing zinc and oxygen diffusion from the ZnO-ZnS internal interface to the surface of the ZnS particle. The kinetics of ZnO sulfidation by H(2)S has been investigated using isothermal and isobaric thermogravimetry. Kinetic tests have been performed that show that nucleation of ZnS is instantaneous compared to the growth process. A reaction mechanism composed of eight elementary steps has been proposed to account for these results, and various possible rate laws have been determined upon approximation of the rate-determining step. Thermogravimetry experiments performed in a wide range of H(2)S and H(2)O partial pressures have shown that the ZnO sulfidation reaction rate has a nonlinear variation with H(2)S partial pressure at the same time no significant influence of water vapor on reaction kinetics has been observed. From these observations, a mixed kinetics of external interface reaction with water desorption and oxygen diffusion has been determined to control the reaction kinetics and the proposed mechanism has been validated. However, the formation of voids at the ZnO-ZnS internal interface, characterized by TEM and electron tomography, strongly slows down the reaction rate. Therefore, the impact of the decreasing ZnO-ZnS internal interface on reaction kinetics has been taken into account in the reaction rate expression. In this way the void formation at the interface has been modeled considering a random nucleation followed by an isotropic growth of cavities. Very good agreement has been observed between both experimental and calculated rates after taking into account the decrease in the ZnO-ZnS internal interface. SN - 1463-9084 UR - https://www.unboundmedicine.com/medline/citation/23238352/New_insight_into_the_ZnO_sulfidation_reaction:_mechanism_and_kinetics_modeling_of_the_ZnS_outward_growth_ L2 - https://doi.org/10.1039/c2cp42988h DB - PRIME DP - Unbound Medicine ER -