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Catalytic partial oxidation of methane over nickel and ruthenium based catalysts under low O2/CH4 ratios and with addition of steam
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.ORCID iD: 0000-0002-3793-1197
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. UMSA Universidad Mayor de San Andres, Bolivia.ORCID iD: 0000-0001-8488-4429
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2015 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, 192-201 p.Article in journal (Refereed) Published
Abstract [en]

Catalytic partial oxidation (CPO) of methane to synthesis gas at low O2/CH4 ratios and in the presence of steam was investigated over nickel and ruthenium catalysts supported on hydrotalcite-derived materials. The influence of catalyst properties and composition on activity, temperature profile and deactivation by carbon formation was examined. All catalyst presented high methane conversions, close to the values predicted by thermodynamic equilibrium and such conversions increased in proportion to the metal surface of the catalyst tested. The temperature profiles at O2/CH4 = 0.2 and H2O/CH4 = 0.3 and a constant exit temperature of 700 °C varied depending on the catalyst type; it was possible to examine catalyst deactivation from the change in the shape of the profile of each catalyst. Since the O2/CH4 and H2O/CH4 ratios were low, the risk or potential for carbon formation was thermodynamically favorable along the entire catalytic bed; however, this potential was qualitatively higher when the temperature profile of the catalyst presented a pronounced maximum peak at the inlet of the reactor. During catalytic reaction tests and methane decomposition experiments, the ruthenium catalyst did not formed appreciable amounts of carbon while a bimetallic catalyst (Ni and Ru) form only small amounts (in comparison with the nickel catalysts). For the ruthenium catalyst, a higher O2/CH4 ratio favored conversions closer to the equilibrium value. The observations presented in this work indicate that during the CPO of methane, at low O2/CH4 ratios and in the presence of steam, the catalyst properties and composition will have a substantial influence on the extent of the combustion and reforming reactions along the catalytic bed. This will in turn define the temperature profile, and therefore the risk or potential for carbon formation; this risk might effectively be overcome by the use of ruthenium-containing catalysts.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 153, 192-201 p.
Keyword [en]
Carbon formation, Nickel, Partial oxidation of methane, Ruthenium, Synthesis gas, Carbon, Catalysis, Catalyst activity, Catalyst deactivation, Catalytic oxidation, Catalytic reforming, Methane, Oxidation, Reforming reactions, Steam reforming, Synthesis (chemical), Temperature, Temperature control, Bimetallic catalysts, Catalytic partial oxidation, Catalytic partial oxidation of methane, Methane decomposition, Ruthenium based catalysts, Thermodynamic equilibria, Catalysts
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-167689DOI: 10.1016/j.fuel.2015.03.009ISI: 000352800800024Scopus ID: 2-s2.0-84925353352OAI: oai:DiVA.org:kth-167689DiVA: diva2:816111
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20150602

Available from: 2015-06-02 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Catalytic partial oxidation of methane over nickel and ruthenium based catalysts for GTL applications
Open this publication in new window or tab >>Catalytic partial oxidation of methane over nickel and ruthenium based catalysts for GTL applications
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Gas to Liquids (GTL) process is an important alternative for monetizing natural gas through the production of long-chain liquid hydrocarbons, e.g. diesel fuel. The GTL process involves three main steps: synthesis gas production to obtain H2 and CO, Fischer-Tropsch synthesis to obtain a synthetic crude oil, and upgrading/refining to obtain final products. Since the synthesis gas production is the most expensive step, there is great interest in optimizing and exploring new routes for syngas production.

This thesis focuses on the conversion of methane, the main component of natural gas, into synthesis gas by catalytic partial oxidation (CPO). Several aspects of the CPO reaction in the context of the GTL technology are discussed. The work contributes to an increased knowledge concerning utilizing a CPO reactor as pre-reformer in the synthesis gas production process as well as the influence of catalyst properties and composition on the catalytic behavior when using nickel and ruthenium-based catalysts in the CPO reaction.

The thesis is a summary of five publications. The first two publications (Papers I and II) review the current status of both the GTL technology and the catalytic partial oxidation of methane. Paper III analyzes a process configuration comprising of a CPO pre-reformer followed by an autothermal reforming (ATR) reactor using a thermodynamic equilibrium approach. It was found that a proper manipulation of the process conditions is needed to obtain a suitable synthesis gas for GTL applications simultaneously of minimizing the risk of carbon formation in the CPO reactor; the operation of the CPO reactor demanded low O2/CH4 and H2O/CH4 feed molar ratios. Accordingly, in paper IV, the partial oxidation of methane at low O2/CH4 and H2O/CH4 ratios is investigated over nickel and ruthenium catalysts supported on MgO/MgAl2O4 and compared with a commercial nickel-based catalyst. The extent or impact of the combustion and reforming reactions along the catalytic bed are substantially influenced by catalyst properties and composition. Deactivation by carbon formation is also discussed; ruthenium-containing catalysts might positively overcome carbon formation. To gain greater insight concerning the influence of the catalyst composition and properties on carbon formation, a set of nickel and bimetallic nickel-ruthenium catalysts, supported on α-Al2O3, γ-Al2O3 and MgO/MgAl2O4, is tested in the CH4 decomposition reaction in Paper V. For these catalysts, the resistance towards carbon formation is mainly correlated with the nickel particle size. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xi, 83 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:63
Keyword
Catalytic partial oxidation, carbon formation, GTL, nickel, ruthenium, synthesis gas, thermodynamic equilibrium.
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-176424 (URN)978-91-7595-753-1 (ISBN)
Public defence
2015-11-27, K1, Teknikringen 56, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151105

Available from: 2015-11-04 Created: 2015-11-03 Last updated: 2015-11-04Bibliographically approved

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Velasco, Jorge A.

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