Development of a methanol reformer for fuel cell vehicles Bård Lindström KTH-Kungliga Tekniska Högskolan Department of Chemical Engineering and Technology Chemical Technology Stockholm 2003 PhD Thesis TRITA-KET R172 ISSN 1104-3466 ISRN KTH/KET/R-172-SE ISBN 91-7283-406-4 To Amanda and my parents Abstract Vehicles powered by fuel cells are from an environmental aspect superior to the traditional automobile using internal combustion of gasoline. Power systems which are based upon fuel cell technology require hydrogen for operation. The ideal fuel cell vehicle would operate on pure hydrogen stored on-board. However, storing hydrogen on-board the vehicle is currently not feasible for technical reasons. The hydrogen can be generated on-board using a liquid hydrogen carrier such as methanol and gasoline. The objective of the work presented in this thesis was to develop a catalytic hydrogen generator for automotive applications using methanol as the hydrogen carrier. The first part of this work gives an introduction to the field of methanol reforming and the properties of a fuel cell based power system. Paper I reviews the catalytic materials and processes available for producing hydrogen from methanol. The second part of this thesis consists of an experimental investigation of the influence of the catalyst composition, materials and process parameters on the activity and selectivity for the production of hydrogen from methanol. In Papers II-IV the influence of the support, carrier and operational parameters is studied. In Paper V an investigation of the catalytic properties is performed in an attempt to correlate material properties with performance of different catalysts. In the third part of the thesis an investigation is performed to elucidate whether it is possible to utilize oxidation of liquid methanol as a heat source for an automotive reformer. In the study which is presented in Paper VI a large series of catalytic materials are tested and we were able to minimize the noble metal content making the system more cost efficient. In the final part of this thesis the reformer prototype developed in the project is evaluated. The reformer which was constructed for serving a 5 kWe fuel cell had a high performance with near 100 % methanol conversion and CO concentrations below 1 vol% in the product stream. The results of this part are presented in Paper VII. Keywords: methanol, fuel cell, vehicle, catalyst, copper, hydrogen, on-board, steam reforming, partial oxidation, combined reforming, oxidative steam reforming, auto-thermal reforming, zinc, zirconium, chromium, aluminium oxide, manganese, characterization, temperature programmed reduction, X-ray diffraction, chemisorption, carbon monoxide, poisoning, reformer. Sammanfattning Fordon med bränsleceller som drivkälla överträffar ur miljösynpunkt traditionella bilar utrustade med bensindrivna förbränningsmotorer. Elgenererande system baserade på bränslecellteknik behöver väte för driften. Det ideala bränslecellfordonet utnyttjar rent väte som lagras ombord. Emellertid är inte lagring ombord på fordonet utförbar på grund av tekniska skäl. Väte kan framställas ombord genom att använda en vätebärare som metanol och bensin. Målet för arbetet som presenteras i denna avhandling var att utveckla en katalytisk vätgasgenerator för mobila tillämpningar genom att använda metanol som vätebärare. Den första delen av arbetet ger en introduktion till området metanolreformering och egenskaperna hos ett bränslecellbaserat kraftsystem. Artikel I ger en kritisk översikt av katalytiska material och processer som är tillgängliga för att producera väte från metanol. Andra delen av denna avhandling består av en experimentell undersökning av inflytandet av katalysatorsammansättningen, material- och processparametrar på aktiviteten och selektiviteten för produktion av väte från metanol. I artikel II-IV studeras inflytandet av bärare, substrat och driftparametrar. I artikel V genomförs en undersökning av de katalytiska egenskaperna i ett försök att korrelera materialegenskaper med prestanda för olika katalysatorer. I den tredje delen av avhandlingen genomförs en undersökning för att belysa om det är möjligt att utnyttja oxidation av vätskeformig metanol som värmekälla för en automotiv reformer. I studien, som presenteras i artikel VI, testas en stor serie av katalytiska material och vi kunde minimera ädelmetallinnehållet vilket gör systemet mer kostnadseffektivt. I den sista delen av avhandlingen utvärderades reformerprototypen som utvecklats i projektet. Reformern som konstruerats för att betjäna en 5 kWe bränslecell hade hög prestanda med nära 100 % omsättning av metanol och CO- koncentrationer under 1 vol% i produktgasen. Resultaten från denna del är presenterade i artikel VII. Nyckelord: methanol, fuel cell, vehicle, catalyst, copper, hydrogen, on-board, steam reforming, partial oxidation, combined reforming, oxidative steam reforming, auto-thermal reforming, zinc, zirconium, chromium, aluminium oxide, manganese, characterization, temperature programmed reduction, X-ray diffraction, chemisorption, carbon monoxide, poisoning, reformer. An expert is a person who has made all the mistakes that can be made in a very narrow field. Niels Bohr Publications referred to in this thesis The work presented in this thesis is based upon the following publications, referred to by their Roman numerals. The papers are appended at the end of the thesis I. Agrell, J., Lindström, B., Pettersson, L.J., and Järås, S.G. (2002). Catalytic hydrogen generation from methanol, in Spivey, J.J. (Ed.), Catalysis – Specialist Periodical Reports, Royal Society of Chemistry, Cambridge, Vol. 16, pp. 67-132. II. Lindström, B. and Pettersson, L.J. (2001). Hydrogen generation by steam reforming of methanol over copper-based catalysts for fuel cell applications. Int. J. Hydrogen Energy 26, 923-33. III. Lindström, B., Agrell, J., and Pettersson, L.J. (2002). Combined reforming of methanol for hydrogen generation over monolithic catalysts. Chemical Engineering Journal (in press). IV. Lindström, B. and Pettersson, L.J. (2002). Steam reforming of methanol over copper-based monoliths: The effects of zirconia doping. J. Power Sources 106, 264-273. V. Lindström, B., Pettersson, L.J., and Menon, P.G. (2002). Activity and characterization of Cu/Zn, Cu/Cr and Cu/Zr on γ-alumina for methanol reforming for fuel cell vehicles. Appl. Catal. A 234, 111-125. VI. Lindström, B. and Pettersson, L.J. (2003). Catalytic oxidation of liquid methanol as a heat source for an automotive reformer. Accepted for publication in Chemical Engineering and Technology. VII. Lindström, B. and Pettersson, L.J. (2003). Design and development of an auto-thermal reformer for fuel cell applications. Accepted for publication in Journal of Power Sources. Other publications Other publications and conference papers on methanol reforming 1. Lindström, B. and Pettersson, L.J. (2001). Deactivation of copper-based catalysts for fuel cell applications. Catal. Lett. 74, 27-30. 2. Lindström, B. and Pettersson, L.J. (2000). Steam reforming of methanol for fuel cell applications. Proc. 9th Nordic Symposium on Catalysis, June 4-6, Lidingö, Sweden, p. 101-102. 3. Lindström, B. and Pettersson, L.J. (2000). A study of ethanol and methanol as a fuel for onboard hydrogen generation by steam reforming on copper-based catalysts. Proc. XIII International Symposium on Alcohol Fuels, Stockholm, July 3-6, 2000. 4. Lindström, B. and Pettersson, L.J. (2000). Steam reforming of methanol for automotive applications. Proc. 2000 Fuel Cell Seminar, Portland, Oregon, October 2000, pp. 325-328. 5. Lindström, B., Agrell, J., and Pettersson, L.J. (2001). Combinatorial Reforming of Methanol for Hydrogen Generation over Monolithic Catalysts. Proc. 17th North American Catalysis Society Meeting, Toronto, June 3-8, 2001, p. 140. 6. Lindström, B. and Pettersson, L.J. (2001). Catalytic steam reforming of methanol for automotive fuel cell applications. Proc. 5th European Congress on Catalysis (EUROPACAT 5), Limerick, Ireland, September 2-7, 2001. 7. Lindström, B. and Pettersson, L.J. (2001). Steam reforming of methanol over copper-based monoliths: The effects of zirconia doping. Proc. 7th Grove Fuel Cell Symposium, London, September 11-13, 2001. 8. Lindström, B., Pettersson, L.J. and Menon, P.G. (2002). Influence of the operating conditions on the performance of a methanol reformer. Proc. 10th Nordic Symposium on Catalysis, Helsingør, Denmark, June 2-4, 2002. 9. Pettersson, L.J. and Lindström, B. (2002). Catalytic fuel processing for fuel cell cars. Proc. Fourth International Tokyo Conference on Advanced Catalytic Science and Technology, Tokyo, July 14-19, 2002 10. Lindström, B. and Pettersson, L.J. (2002). Development of a methanol fuelled reformer for fuel cell applications. Proc. Fuel Cells - Science and Technology 2002, Scientific Advances in Fuel Cell Systems, Amsterdam, 25-26 September, 2002. 11. Lindström, B. and Pettersson, L.J. (2002). Strategies for optimizing a methanol reformer for fuel cell vehicles. Proc. XIV International Symposium on Alcohol Fuels, Phuket, Thailand, 12-15 November 2002. 1. Introduction.......................................................................................................3 1.1 Background..................................................................................................3 1.2 Fuel cell technology ....................................................................................5 1.3 Fuel strategies for mobile fuel cell applications..........................................6