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The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.ORCID-id: 0000-0003-3826-1858
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
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2016 (Engelska)Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 514, s. 91-102Artikel i tidskrift (Refereegranskat) Published
Resurstyp
Text
Abstract [en]

Abstract The present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.

Ort, förlag, år, upplaga, sidor
Elsevier, 2016. Vol. 514, s. 91-102
Nyckelord [en]
Methanation, Deactivation, Nickel carbonyl, Sintering, Heat and mass transfer, Alumina
Nationell ämneskategori
Kemiska processer
Identifikatorer
URN: urn:nbn:se:kth:diva-182353DOI: 10.1016/j.apcata.2015.12.034ISI: 000371551200010Scopus ID: 2-s2.0-84955264386OAI: oai:DiVA.org:kth-182353DiVA, id: diva2:904227
Forskningsfinansiär
EU, FP7, Sjunde ramprogrammet, 308733
Anmärkning

QC 20160330. QC 20160407

Tillgänglig från: 2016-02-18 Skapad: 2016-02-18 Senast uppdaterad: 2017-11-30Bibliografiskt granskad
Ingår i avhandling
1. Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation
Öppna denna publikation i ny flik eller fönster >>Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: US-AB, 2016. s. xii, 124
Serie
TRITA-CHE-Report, ISSN 1654-1081
Nyckelord
cobalt, nickel, Fischer-Tropsch synthesis, methanation, deactivation, carbonyl, sintering, carbon fomation. sulfur, poisoning
Nationell ämneskategori
Annan kemiteknik
Forskningsämne
Kemiteknik
Identifikatorer
urn:nbn:se:kth:diva-190593 (URN)978-91-7729-060-5 (ISBN)
Disputation
2016-09-23, F3, Lindstedtsvägen 26, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
EU, FP7, Sjunde ramprogrammet, 308733
Anmärkning

QC 20160817

Tillgänglig från: 2016-08-17 Skapad: 2016-08-12 Senast uppdaterad: 2016-08-18Bibliografiskt granskad

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Barrientos, Javier

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Barrientos, JavierLualdi, MatteoBoutonnet, MagaliJärås, Sven
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Applied Catalysis A: General
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