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Hydrogen Generation for Fuel Cells in Auxiliary Power Systems
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers.

Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts.

Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems.

The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , viii, 76 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:7
Keyword [en]
autothermal reforming, auxiliary power unit, diesel, dimethyl ether, fuel cell, fuel-flexible reformer, hydrogen, PdZn alloy, reforming catalyst, reformer design, Rh
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10024ISBN: 978-91-7415-245-6 (print)OAI: oai:DiVA.org:kth-10024DiVA: diva2:201366
Public defence
2009-03-27, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100804Available from: 2009-03-12 Created: 2009-03-04 Last updated: 2010-08-04Bibliographically approved
List of papers
1. Study of a reactor concept for hydrogen generation from diesel fuel
Open this publication in new window or tab >>Study of a reactor concept for hydrogen generation from diesel fuel
(English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045Article in journal (Other academic) Submitted
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10018 (URN)
Note
QS 20120328Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2012-03-28Bibliographically approved
2. Effect of Mn addition to CeO2-ZrO2-supported Rh and Ru catalysts on the activity for diesel reforming
Open this publication in new window or tab >>Effect of Mn addition to CeO2-ZrO2-supported Rh and Ru catalysts on the activity for diesel reforming
(English)In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879XArticle in journal (Other academic) Submitted
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10020 (URN)
Note
QS 20120328Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2012-03-28Bibliographically approved
3. Assessing the adaptability to varying fuel supply of an autothermal reformer
Open this publication in new window or tab >>Assessing the adaptability to varying fuel supply of an autothermal reformer
2008 (English)In: Chemical Engineering Journal, ISSN 1385-8947, Vol. 142, 309-317 p.Article in journal (Refereed) Published
Abstract [en]

The present paper describes the study of an autothermal reformer and its fuel-flexible capabilities. Experiments have been performed in a reactor designed to generate hydrogen by autothermal reforming for a 1-5 kW(e) polymer electrolyte fuel cell. Both logistic fuels (diesel, gasoline, and E85) and alternative fuel candidates (methanol, ethanol, and dimethyl ether) were tested in the reformer. The same catalyst composition, Rh supported on Ce/La-doped gamma-Al2O3 and deposited on cordierite monoliths, was used for all fuels. The practical feasibility of reforming each fuel in the present reactor design was tested and evaluated in terms of fuel conversion and selectivity to hydrogen and carbon dioxide. Temperature profiles were studied both in the axial and radial direction of the reformer. It was concluded from the experiments that the reformer design was most suitable for use with hydrocarbon mixtures Such as diesel, gasoline, and E85, where it represents a good basis for an optimized multifuel-reformer design.

Keyword
hydrogen; multifuel autothermal reformer; auxiliary power unit; Rh catalyst
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10021 (URN)10.1016/j.cej.2008.02.026 (DOI)000259555500009 ()2-s2.0-49649087235 (Scopus ID)
Note
QC 20100804Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2011-04-18Bibliographically approved
4. Evaluation of Pd-based catalysts and the influence of operating conditions for autothermal reforming of dimethyl ether
Open this publication in new window or tab >>Evaluation of Pd-based catalysts and the influence of operating conditions for autothermal reforming of dimethyl ether
2007 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 76, 41-49 p.Article in journal (Refereed) Published
Abstract [en]

A series of different Pd-based catalysts supported on ceramic monoliths were synthesized and tested in a screening study for autothermal reforming of dimethyl ether (DME). Alumina-supported Pd was shown to be very active for this reaction at temperatures between 350 and 400 degrees C. Adding Zn to Pd/gamma-Al2O3 decreased the activity of decomposition reactions leading to better reforming activity, and resulting in high selectivity to carbon dioxide. Pd-Zn/gamma-Al2O3 was further evaluated in a parameter study varying oxygen-to-DME ratio, steam-to-DME ratio and temperature. The effect on the reformer performance of changing the operating conditions is discussed. The Pd-Zn/gamma-Al2O3 catalyst generated carbon monoxide concentrations below 5%, and hydrogen concentrations close to 50%. The catalyst performance was significantly improved by preconditioning in hydrogen. Results from a first round of catalyst characterization studies suggest that Pd-Zn species are formed on the alumina support following reduction

Keyword
hydrogen; autothermal reforming; dimethyl ether; auxiliary power unit
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10022 (URN)10.1016/j.apcatb.2007.05.011 (DOI)000250799700006 ()2-s2.0-34948843511 (Scopus ID)
Note
QC 20100804Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2010-12-06Bibliographically approved
5. Catalytic properties of Pd supported on ZnO/ZnAl2O4/Al2O3 mixtures in dimethyl ether autothermal reforming
Open this publication in new window or tab >>Catalytic properties of Pd supported on ZnO/ZnAl2O4/Al2O3 mixtures in dimethyl ether autothermal reforming
2009 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 86, 18-26 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic properties of Pd supported on mixtures of zinc oxide, zinc aluminate, and alumina, prepared from gamma-alumina and zinc nitrate, were studied for autothermal reforming (ATR) of dimethyl ether (DME). The performance of the catalysts was tested in a small-scale reactor, using cordierite monoliths as substrate. The catalysts exhibited high activity and generated hydrogen-rich product gases with CO concentrations below 5 vol.% in the temperature range between 350 and 450 degrees C (at O-2:DME = 0.7, H2O:DME = 2.5, and GHSV = 15000 h(-1)). The highest DME conversion was obtained for a catalyst in which the support comprised mainly ZnAl2O4. Physical mixing of the catalysts with gamma-Al2O3 resulted in increased DME conversion but a lowering of the CO2 selectivity.The catalysts were characterized by CO chemisorption, liquid nitrogen adsorption, temperature-programmed desorption of ammonia, temperature-programmed reduction, transmission electron microscopy, and X-ray diffraction. It was found that decreasing surface area and decreasing number of acid sites, caused by thermal treatment during generation of the supports, did not affect the activity negatively. The high CO2 selectivity of the catalysts was correlated with PdZn alloy formation.

Keyword
Hydrogen; Dimethyl ether; Autothermal reforming; Pd catalyst; PdZn alloy
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10023 (URN)10.1016/j.apcatb.2008.07.012 (DOI)000262887700003 ()2-s2.0-58049155416 (Scopus ID)
Note
QC 20100804Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2010-12-06Bibliographically approved

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