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Mechanism of carbon deposits removal from supported Ni catalysts

Stavros-Alexandros Theofanidis (UGent) , Vladimir Galvita (UGent) , Hilde Poelman (UGent) , Rakesh Batchu (UGent) , Lukas Buelens (UGent) , Christophe Detavernier (UGent) and Guy Marin (UGent)
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Abstract
Catalyst deactivation due to carbon deposition is a major issue in all reforming technologies. Because of the significant economic cost of catalyst replacement, catalyst regeneration is increasingly attracting attention. The regeneration mechanism of Ni catalysts, with respect to carbon removal, was investigated on support materials prepared by one-pot synthesis. The supports were classified based on their redox functionality: Al2O3, MgAl2O4 show no redox properties in contrast to MgFe0.09Al1.O-91(4) and CeZrO2 that have redox functionality. A Temporal Analysis of Products (TAP) setup was used to investigate the isothermal regeneration mechanism of Ni catalysts at 993 K by O-2. Different mechanisms were distinguished depending on the redox functionality of the support material. Two consecutive steps occur on the support that have no redox properties (Al2O3 and MgAl2O4): metallic Ni is oxidized to form NiO (oxidation step), resulting in an initial local temperature increase of 50-60 K in total, enabling metal particle migration to carbon that was initially separated from the metal and subsequent oxidation through NiO lattice oxygen (reduction step). On the other hand, the mechanism of carbon removal by O-2 from Ni catalysts on supports with redox properties does not require particle migration. Two parallel contributions are proposed: 1) Ni metal is oxidized to form NiO, where after lattice oxygen of NiO is used for the oxidation of carbon that is deposited upon the metals, 2) carbon oxidation through lattice oxygen that is provided by the support. No dependency of the carbon gasification mechanism on the exposed fraction of the metal (particle size in the nanoscale) or on the structure of the deposited carbon was concluded.
Keywords
Catalyst deactivation Catalyst regeneration Carbon removal Metal particle migration, RAMAN-SPECTROSCOPY, NICKEL-CATALYSTS, PARTIAL OXIDATION, BULK DIFFUSION, COKE FORMATION, GASIFICATION, METHANE, KINETICS, GRAPHITE, STEAM

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MLA
Theofanidis, Stavros-Alexandros, Vladimir Galvita, Hilde Poelman, et al. “Mechanism of Carbon Deposits Removal from Supported Ni Catalysts.” APPLIED CATALYSIS B-ENVIRONMENTAL 239 (2018): 502–512. Print.
APA
Theofanidis, S.-A., Galvita, V., Poelman, H., Batchu, R., Buelens, L., Detavernier, C., & Marin, G. (2018). Mechanism of carbon deposits removal from supported Ni catalysts. APPLIED CATALYSIS B-ENVIRONMENTAL, 239, 502–512.
Chicago author-date
Theofanidis, Stavros-Alexandros, Vladimir Galvita, Hilde Poelman, Rakesh Batchu, Lukas Buelens, Christophe Detavernier, and Guy Marin. 2018. “Mechanism of Carbon Deposits Removal from Supported Ni Catalysts.” Applied Catalysis B-environmental 239: 502–512.
Chicago author-date (all authors)
Theofanidis, Stavros-Alexandros, Vladimir Galvita, Hilde Poelman, Rakesh Batchu, Lukas Buelens, Christophe Detavernier, and Guy Marin. 2018. “Mechanism of Carbon Deposits Removal from Supported Ni Catalysts.” Applied Catalysis B-environmental 239: 502–512.
Vancouver
1.
Theofanidis S-A, Galvita V, Poelman H, Batchu R, Buelens L, Detavernier C, et al. Mechanism of carbon deposits removal from supported Ni catalysts. APPLIED CATALYSIS B-ENVIRONMENTAL. 2018;239:502–12.
IEEE
[1]
S.-A. Theofanidis et al., “Mechanism of carbon deposits removal from supported Ni catalysts,” APPLIED CATALYSIS B-ENVIRONMENTAL, vol. 239, pp. 502–512, 2018.
@article{8575511,
  abstract     = {Catalyst deactivation due to carbon deposition is a major issue in all reforming technologies. Because of the significant economic cost of catalyst replacement, catalyst regeneration is increasingly attracting attention. The regeneration mechanism of Ni catalysts, with respect to carbon removal, was investigated on support materials prepared by one-pot synthesis. The supports were classified based on their redox functionality: Al2O3, MgAl2O4 show no redox properties in contrast to MgFe0.09Al1.O-91(4) and CeZrO2 that have redox functionality. 
A Temporal Analysis of Products (TAP) setup was used to investigate the isothermal regeneration mechanism of Ni catalysts at 993 K by O-2. Different mechanisms were distinguished depending on the redox functionality of the support material. Two consecutive steps occur on the support that have no redox properties (Al2O3 and MgAl2O4): metallic Ni is oxidized to form NiO (oxidation step), resulting in an initial local temperature increase of 50-60 K in total, enabling metal particle migration to carbon that was initially separated from the metal and subsequent oxidation through NiO lattice oxygen (reduction step). On the other hand, the mechanism of carbon removal by O-2 from Ni catalysts on supports with redox properties does not require particle migration. Two parallel contributions are proposed: 1) Ni metal is oxidized to form NiO, where after lattice oxygen of NiO is used for the oxidation of carbon that is deposited upon the metals, 2) carbon oxidation through lattice oxygen that is provided by the support. No dependency of the carbon gasification mechanism on the exposed fraction of the metal (particle size in the nanoscale) or on the structure of the deposited carbon was concluded.},
  author       = {Theofanidis, Stavros-Alexandros and Galvita, Vladimir and Poelman, Hilde and Batchu, Rakesh and Buelens, Lukas and Detavernier, Christophe and Marin, Guy},
  issn         = {0926-3373},
  journal      = {APPLIED CATALYSIS B-ENVIRONMENTAL},
  keywords     = {Catalyst deactivation Catalyst regeneration Carbon removal Metal particle migration,RAMAN-SPECTROSCOPY,NICKEL-CATALYSTS,PARTIAL OXIDATION,BULK DIFFUSION,COKE FORMATION,GASIFICATION,METHANE,KINETICS,GRAPHITE,STEAM},
  language     = {eng},
  pages        = {502--512},
  title        = {Mechanism of carbon deposits removal from supported Ni catalysts},
  url          = {http://dx.doi.org/10.1016/j.apcatb.2018.08.042},
  volume       = {239},
  year         = {2018},
}

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