| 1. |
- Barrientos, Javier, et al.
(författare)
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Deactivation of Ni/gamma-Al2O3 Catalysts in CO Methanation : Effect of Zr, Mg, Ba and Ca Oxide Promoters
- 2017
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Ingår i: Topics in catalysis. - : Springer. - 1022-5528 .- 1572-9028. ; 60:17-18, s. 1276-1284
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Tidskriftsartikel (refereegranskat)abstract
- Catalyst deactivation is one of the major concerns in the production of substitute natural gas (SNG) via CO methanation. Catalysts in this application need to be active at low temperatures, resistant to polymeric carbon formation and stable at high temperatures and steam partial pressures. In the present work, a series of alumina-supported nickel catalysts promoted with Zr, Mg, Ba or Ca oxides were investigated. The catalysts were tested under low temperature CO methanation conditions in order to evaluate their resistance to carbon formation. The catalysts were also exposed to accelerated ageing conditions at high temperatures in order to study their thermal stability. The aged catalysts lost most of their activity mainly due to sintering of the support and the nickel crystallites. Apparently, none of these promoters had a satisfactory effect on the thermal resistance of the catalyst. Nevertheless, it was found that the presence of Zr can reduce the rate of polymeric carbon formation.
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| 2. |
- Barrientos, Javier, et al.
(författare)
-
Fischer-Tropsch Synthesis Over Zr-Promoted Co/gamma-Al2O3 Catalysts
- 2017
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Ingår i: Topics in catalysis. - : SPRINGER/PLENUM PUBLISHERS. - 1022-5528 .- 1572-9028. ; 60:17-18, s. 1285-1298
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Tidskriftsartikel (refereegranskat)abstract
- Two Zr-modified alumina supports were synthetized containing the same amount of Zr but a different distribution of this modifier over the alumina surface. These supports, together with the unmodified alumina carrier, were used to prepare three cobalt-based catalysts which were characterized and tested under relevant Fischer-Tropsch conditions. The three catalysts presented very similar porosity and cobalt dispersion. The addition of Zr nor its distribution enhanced the catalyst reducibility. The catalyst activity was superior when using a carrier consisting of large ZrO2 islands over the alumina surface. The use of a carrier with a homogeneous Zr distribution had however, a detrimental effect. Moreover, a faster initial deactivation rate was observed for the Zr-promoted catalysts, fact that may explain this contradictory effect of Zr on activity. Finally, the addition of Zr showed a clear enhancement of the selectivity to long chain hydrocarbons and ethylene, especially when Zr was well dispersed.
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