Efficient hydrogen supply from tetralin with superheated liquid-film-type catalysis for operating fuel cells

Abstract

A catalytic reaction pair, consisting of tetralin dehydrogenation/naphthalene hydrogenation, has newly been proposed as a storage medium of hydrogen for operating polymer-electrolyte fuel cells. The hydrogen storage capacity of tetralin (3.0 wt.%, 28.2 kg-H 2/m 3) is lower than that of decalin (7.3 wt.%, 64.8 kg-H 2/m 3), with the decalin dehydrogenation/naphthalene hydrogenation pair operated. Nevertheless, the rates of tetralin dehydrogenation and naphthalene hydrogenation to tetralin are much faster than the rates of the latter reaction pair. With respect to hydrogen storage for static or domestic use with space advantages, tetralin would be superior to decalin due to the ability of supplying hydrogen easily. Very high reaction rates and conversions of hydrogen evolution from tetralin were accomplished stationarily with “superheated liquid-film-type catalysis” by heating at 210–240 °C, in contrast to the poor results obtained with ordinary suspended catalysis. In particular, a carbon-supported nano-size platinum catalyst in the superheated liquid-film state exhibited efficient tetralin conversion as high as 95% within 25 min contact at 240 °C under distillation conditions. At the same temperature range, the dehydrogenation rates for decalin that had been obtained were ca. 3.9–6.3 times slower than those for tetralin, suggesting the excellent characteristics of tetralin as a hydrogen storage medium. In addition, carbon-supported nickel–ruthenium composite catalysts were found to give dehydrogenation activities at 240 °C comparable with those of the platinum catalyst at 210 °C.