Hydrogen from bioethanol: Catalytic honeycombs loaded with Co-Fe/ZnOfor small-scale energy applications
- PDF / 1,310,202 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 144 Views
Hydrogen from bioethanol: Catalytic honeycombs loaded with Co-Fe/ZnO for small-scale energy applications Cristian Ledesma1,2, Maria Roig1, Jordi Llorca1,2,* Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya. Diagonal 647, ed. ETSEIB, 08028 Barcelona, Spain. 2 Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya. Pasqual i Vila 15, 08028 Barcelona, Spain.
1
ABSTRACT Catalytic monoliths loaded with ZnO-supported Co-Fe catalysts were prepared in one step by the in situ urea method and tested in the ethanol steam reforming reaction to produce hydrogen. The most active and selective formulation was attained with a Fe/Co molar ratio between 0.05 and 0.1, which showed negligible amounts of methane among the reaction products, thus offering an active and selective material for the low-temperature steam reforming of ethanol for small-scale energy applications. INTRODUCTION Ethanol is nowadays a well established source of hydrogen via catalytic steam reforming, oxidative reforming or partial oxidation processes. Numerous reviews have been published in the last years, covering both catalytic aspects and fuel reformer concepts [1-5]. Ethanol has the advantage over other conventional substrates such as natural gas, gasoline or LPG that it is readily available, easy to obtain from biomass, CO2-neutral (bioethanol), safe to handle, and can be processed at low temperature to obtain hydrogen. Among the different processes for hydrogen production, including those outlined above as well as CO2 sorption enhanced routes, steam reforming (ESR) is the simplest for implementation and yields more hydrogen, since part of it comes from water (eq. 1). (1) C2H5OH + 3 H2O Æ 6 H2 + 2 CO2 The drawback of ESR, however, is thermal management. Steam reforming reactions are strongly endothermic and require a continuous supply of heat. In ethanol reformers, this can be provided by a combination of direct and catalytic combustion of ethanol and by burning the anode off-gas of a fuel cell [4,6]. Therefore, it is desirable to develop catalysts for lowtemperature ESR to optimize thermal management in addition to build long life and safe reformers that can be used for portable applications. A survey of the literature reveals that noble metal-based catalysts perform well for ESR [1-3,7,8]. They are stable and exhibit high activity, but only at high temperature (>800 K). The reason is that the reaction mechanism involves the decomposition of ethanol at low temperature into a mixture of hydrogen, carbon monoxide and methane (eq. 2), followed by the water gas shift reaction (WGS) at intermediate temperature (eq. 3) and, finally, the steam reforming of methane at high temperature (eq. 4) [9]. C2H5OH ' H2 + CO2 + CH4 (2) (3) CO + H2O ' H2 + CO2 CH4 + 2 H2O ' 4 H2 + CO2 (4)
Then, for small-scale energy applications, a different type of catalyst is required to operate at low temperature; in particular, a catalyst that does not yield methane as an intermediate species in the reaction mechanism, which can only be reform
Data Loading...
