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Promoted RhPt bimetallic catalyst supported on δ-Al2O3 and CeO2-ZrO2 during full-scale autothermal reforming for automotive applications: Post-mortem characterization
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.ORCID-id: 0000-0002-6326-4084
KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
2015 (Engelska)Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 491, s. 8-16Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The influence of sulfur and coke formation on the steam reforming of diesel was evaluated for two promoted RhPt bimetallic catalysts, composed of 1:1 Rh:Pt/10:10 La2O3: CeO2/ δ-Al2O3 (CAT 1) and 1:1 Rh:Pt/4:5 MgO: Y2O3/CeO2 − ZrO2 (CAT 2). The intrinsic activity is related to the total Rh and Pt area observed after the exposure to sulfur. Therefore, the degree of deactivation is related to the amount of sulfur deposited on the active metal sites. Sulfur analysis on the aged catalyst washcoat showed a decreasing sulfur concentration in the axial direction of the reformer. The estimated sulfur coverage related to metal surface area after 40 h on stream reached values of 0.145 in CAT 2, below the equilibrated sulfur coverage of 0.19 after tests with DIN 590. Thus, showing a partial deactivation due to sulfur poisoning. Further catalyst characterization on carbon deposits and thermal aging was performed by TPO, TGA, BET, CO chemisorption, and TEM analysis.

Ort, förlag, år, upplaga, sidor
Angélica González , 2015. Vol. 491, s. 8-16
Nationell ämneskategori
Naturvetenskap
Identifikatorer
URN: urn:nbn:se:kth:diva-160025DOI: 10.1016/j.apcata.2014.11.035ISI: 000349731600002Scopus ID: 2-s2.0-84916600432OAI: oai:DiVA.org:kth-160025DiVA, id: diva2:788141
Anmärkning

QC 20150327

Tillgänglig från: 2015-02-12 Skapad: 2015-02-12 Senast uppdaterad: 2017-12-04Bibliografiskt granskad
Ingår i avhandling
1. RhPt and Ni based catalysts for fuel reforming in energy conversion
Öppna denna publikation i ny flik eller fönster >>RhPt and Ni based catalysts for fuel reforming in energy conversion
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport

sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed.

In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration.

In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2015. s. xii, 100
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:10
Nyckelord
RhPt bimetallic catalysts, Ni catalysts, ceria-zirconia, potassium tungsten bronze, zirconium dioxide, autothermal reforming, biodiesel, diesel, sulfur, deactivation, tar reforming, steam reforming, biomass gasification, auxiliary power units, naphthalene
Nationell ämneskategori
Kemiteknik
Forskningsämne
Kemiteknik
Identifikatorer
urn:nbn:se:kth:diva-160026 (URN)978-91-7595-440-0 (ISBN)
Disputation
2015-03-05, F3, Lindstedtsvägen 26, KTH, Stokcholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20150213

Tillgänglig från: 2015-02-13 Skapad: 2015-02-12 Senast uppdaterad: 2015-11-23Bibliografiskt granskad

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