Bioethanol steam reforming over Pt and Ag in an electrochemical CSTR reactor

The environmental problems caused by the intensive use of fossil fuels-as well as their limited availability- are increasingly demanding a more rational use of our energy resources. Among the various fuels which can be reformed to hydrogen, alcohols are highly promising candidates, because they are easily decomposed in the presence of water to generate a H2 rich mixture, suitable for feeding fuel cells. Bio-ethanol is a particularly important fuel due to its low toxicity, as well as the fact that it is an environmentally clean fuel in terms of composition. Moreover, bio-ethanol has relatively high hydrogen content, is characterized by low production cost and high availability as well as that it can be easily handled [1-2], Based on a thermodynamic and economic analysis, ethanol is considered as an alternative fuel with suitable characteristics for electricity generation in fuel cells and especially in solid oxide fuel cells (SOFCs) [3, 4]. Catalytic steam reforming of hydrocarbons is typically performed between 1023 and 1 173 K; therefore, it is compatible with SOFCs. In a direct internal reforming SOFC, steam reforming of the fuel takes place directly at the anode, thus anode material must be a suitable catalyst for the steam reforming reaction. Steam reforming is an endothermic reaction and produces only H2 and CO2 if ethanol reacts in a most desirable way. However, usually the other by-products such as CH3CHO, CO and CH4 are formed. Steam reforming of ethanol to produce only hydrogen and CO2 favours high temperatures, while by-product formation is rather dominant at low temperatures. The amount of H2 produced in the steam reforming at high temperatures is higher than that accompanied by the by-product formation at lower temperatures. However, from the standpoint of energy saving, low temperature reaction accompanied with the formation of useful by-products is preferable [5]. In the present work, the reaction of ethanol steam reforming over Pt and Ag in a continuous stirred tank (CSTR) YSZ electrochemical reactor has been investigated. The electrode-catalysts, Pt and Ag, have been separately tested at different temperature values ranging from 300 to 700oC, at different ethanol/water volumetric ratios and at different flow rates varying from 25 to 100 cc/min. The experimental results showed that the main products were H2, CO, CO2, CH4 and CH3CHO in all the investigated cases. It was found that at relatively low temperatures (