Low temperature-ethanol steam reforming over Ni-based catalysts supported on CeO2

摘要

Recent research has been focused on methods to produce hydrogen. There is growing interest in the properties of hydrogen as an energy carrier and the prospects look good for hydrogen use in fuel cell applications, especially when production processes involve clean, renewable sources. Although natural gas steam reforming is the most common way to obtain hydrogen, ethanol steam reforming (ESR) may reduce the dependence on fossil fuels and cut harmful emissions. The ESR reaction is promoted at high temperatures, being strongly endothermic, but in some cases it can be performed at low temperatures, using this process as a pre-reforming step before conventional methane steam reforming (MSR). The low temperature range could reduce: the thermal duty, costs and CO formation, making the produced hydrogen capable of being fed into a fuel cell. The performances of Ni-based catalysts for ethanol steam reforming in a low temperature range (LT-ESR) were evaluated. In particular, the activity of bimetallic samples, prepared by impregnation and coprecipitation, was monitored in both diluted and concentrated feed stream conditions. By comparing bimetallic catalysts with monometallic ones prepared at dierent Pt or Ni loadings, it was possible to identify the most suitable sample. 3%wtPt / 10wt%Ni / CeO2 obtained by impregnation achieved the highest performances in terms of both H2 yield and durability, allowing perfect agreement with thermodynamic data. However, during stability tests, reaction plugging phenomena occurred. By changing the water-to-ethanol molar ratio from 3 to 6, a considerable increase in durability was observed. The investigation of exhaust catalysts through various characterization techniques was helpful for studying in detail possible sintering or deactivation occurrence.