Direct utilization of methanol and ethanol in solid oxide fuel cells
Date
2008
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Solid oxide fuel cells (SOFC) are high temperature energy conversion devices operating with hydrogen and synthesis gas, but - in principle - they could also utilize hydrocarbons and alcohols. The objective of this study was to investigate the direct utilization of methanol and ethanol in SOFC. Based on the published literature, the following anodic compositions were considered: Me/ceria and Me/zirconia-doped ceria, (Me = Ni, Cu, CoCo ); L8-0.1Sro.3Cro.sMno.sO3_15 (LSCM); L8-0.1Sro.3 VO3_15 (LSV); and Sro.86 Y o.os TiO3_15 (SYT). In the first part of this thesis, the pyrolysis of methanol and ethanol was examined. It was found that both alcohols undergo significant decomposition, producing mixtures rich in H2, CO and CH4. The conversion depends strongly on the flow and temperature conditions, and is higher for ethanol. The production of soot was always significant for ethanol, while for methanol it became negligible above 800°C. Subsequently, the oxidation of hydrogen and carbon monoxide was investigated on nickel and on the other anode materials using 2 and 3-electrode static and dynamic techniques, combined with impedance spectroscopy measurements. Since distortions affect measurements in 3- electrode planar cells, the configurations used in this study were first validated using a theoretical model. The results obtained indicate that the oxidation of H2 on Ni is about one order of magnitude larger than that of CO. On ceria, LSCM, LSV and SYT, instead, these rates are comparable, but the perovskites alone are very poor electrocatalysts. Besides, a gradual deactivation was observed for LSCM anodes in H2, possibly as a consequence of partial reduction, whereas LSV anodes were very unstable to redox cycling. Finally, the anodes were tested directly with alcohols. The direct utilization of methanol was feasible on all metal/ceria anodes without significant coking. With ethanol metal/ceria anodes were deactivated by coking; however, on Cu/ceria base anodes the deactivation was reversible after exposure to humidified hydrogen, and the anodic microstructure was not damaged. Stability and performance of metal/ceria anodes were improved by using zirconia-doped ceria. The deactivation by coking was delayed by adding small amounts of dispersed ruthenium.
Description
Bibliography: p. 423-444
Keywords
Citation
Cimenti, M. (2008). Direct utilization of methanol and ethanol in solid oxide fuel cells (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/2052