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Further insights into the effect of sulfur on the activity and selectivity of cobalt-based Fischer–Tropsch catalysts
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.ORCID iD: 0000-0003-3826-1858
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
2016 (English)In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, 119-126 p.Article in journal (Refereed) PublishedText
Abstract [en]

 A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.

Place, publisher, year, edition, pages
2016. Vol. 275, 119-126 p.
Keyword [en]
Fischer–Tropsch, Sulfur, Cobalt, Deactivation, Selectivity
National Category
Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-182347DOI: 10.1016/j.cattod.2015.10.039ISI: 000382420300017OAI: oai:DiVA.org:kth-182347DiVA: diva2:904222
Note

QC 20160926

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2016-09-26Bibliographically approved
In thesis
1. Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation
Open this publication in new window or tab >>Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

            A potential route for converting different carbon sources (coal, natural gas and biomass) into synthetic fuels is the transformation of these raw materials into synthesis gas (CO and H2), followed by a catalytic step which converts this gas into the desired fuels. The present thesis has focused on two catalytic steps: Fischer-Tropsch synthesis (FTS) and methanation. The Fischer-Tropsch synthesis serves to convert synthesis gas into liquid hydrocarbon-based fuels. Methanation serves instead to produce synthetic natural gas (SNG). Cobalt catalysts have been used in FTS while nickel catalysts have been used in methanation.

            The catalyst lifetime is a parameter of critical importance both in FTS and methanation. The aim of this thesis was to investigate the deactivation causes of the cobalt and nickel catalysts in their respective reactions.

            The resistance to carbonyl-induced sintering of nickel catalysts supported on different carriers (γ-Al2O3, SiO2, TiO2 and α-Al2O3) was studied. TiO2-supported nickel catalysts exhibited lower sintering rates than the other catalysts. The effect of the catalyst pellet size was also evaluated on γ-Al2O3-supported nickel catalysts. The use of large catalyst pellets gave considerably lower sintering rates. The resistance to carbon formation on the above-mentioned supported nickel catalysts was also evaluated. Once again, TiO2-supported nickel catalysts exhibited the lowest carbon formation rates. Finally, the effect of operating conditions on carbon formation and deactivation was studied using Ni/TiO2 catalysts. The use of higher H2/CO ratios and higher pressures reduced the carbon formation rate. Increasing the temperature from 280 °C to 340 °C favored carbon deposition. The addition of steam also reduced the carbon formation rate but accelerated catalyst deactivation.

            The decline in activity of cobalt catalysts with increasing sulfur concentration was also assessed by ex situ poisoning of a cobalt catalyst. A deactivation model was proposed to predict the decline in activity as function of the sulfur coverage and the sulfur-to-cobalt active site ratio. The results also indicate that sulfur decreases the selectivity to long-chain hydrocarbons and olefins.

Place, publisher, year, edition, pages
Stockholm: US-AB, 2016. xii, 124 p.
Series
TRITA-CHE-Report, ISSN 1654-1081
Keyword
cobalt, nickel, Fischer-Tropsch synthesis, methanation, deactivation, carbonyl, sintering, carbon fomation. sulfur, poisoning
National Category
Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-190593 (URN)978-91-7729-060-5 (ISBN)
Public defence
2016-09-23, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 308733
Note

QC 20160817

Available from: 2016-08-17 Created: 2016-08-12 Last updated: 2016-08-18Bibliographically approved

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