There is a controversial discussion about the possible fuel for the use in low temperature fuel cells. The most prominent candidates are hydrogen, methanol and besides petrol and heavy oils. Hydrogen is favoured because of its possible direct use, though storage and infrastructure are complicated. To overcome the problems with methanol, heavy oils and biomass other than the conventional reforming methods should be taken into accounts which are working at lower temperatures. Supercritical water is an environmentally friendly medium and it is well known in industry and science. Thermo physical properties of supercritical water such as density, viscosity, relative permittivity and hydrogen bonding are quite different from those of steam or liquid water. In contrast to the liquid state mixing of supercritical water with non-polar gases and organic compounds containing large, non-polar groups is generally possible. Gasification of hydrocarbons in supercritical water is based on the characteristics that supercritical water acts not only as a solvent but also as a reagent. Purpose of the reforming process is the fuel conversion into a hydrogen-rich product gas using supercritical water and a catalyst at low temperatures like normal reforming processes. This paper demonstrates first experiments of the reforming of hydrocarbons in supercritical water which have been carried out in a continuous flow reactor. For process simulation n-decane was used as a diesel model compound. The n-decane reforming process as investigated by different commercial catalysts to find the optimal substances for the reforming process. Four different commercial catalysts, well known from steam reforming process, were selected which differ mainly in typical feed and the weight fraction of nickel oxide. Influences of these catalysts were investigated by constant reaction conditions. The results show that n-decane can be converted to a hydrogen rich gas. Furthermore first experiments with diesel show the possibility of fuel conversion at low temperature with commercial steam reforming catalysts. Low temperature and the use of catalysts lead to inhibition of coke formation during the process. The supercritical reforming offers the possibility of a new low temperature hydrocarbon conversion process to hydrogen for fuel cell applications.
Supercritical reforming for fuel cells
Überkritische Reformierung für Brennstoffzellen
2003
8 Seiten, 5 Bilder, 2 Tabellen, 7 Quellen
Conference paper
English
Hydrogen Generation for Fuel Cells based on Supercritical Reforming
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