High Thermal Stability Fe2O3-Al2O3 System to Produce Renewable Pure Hydrogen in Steam Iron Process

Abstract

The use of H2 as fuel of the future is closely linked to the development of Fuel Cells, among them Proton Exchange Membrane Fuel Cells (PEMFCs) are the most attractive. To avoid the irreversible poisoning of the platinum-based catalyst placed on the PEMFC electrodes, pure H2 (CO < 10 ppm) is required. Steam iron process (SIP) is a cyclical process which allows, at high temperature and low pressure, the direct production of pure H2 by redox cycles of iron. Syngas is generally used as reducing agent while steam water is used to oxidize iron and to produce pure H2. However, iron oxides powders suffer from deactivation in few redox cycles due to their low thermal stability. The aim of this study is to improve iron oxides resistance adding Al2O3 as high thermal stability material. Bioethanol is used as renewable sources of syngas to makes the process totally sustainable. To evaluate the effect of Al2O3 addition, different Fe2O3 / Al2O3 ratios were tested (40 wt%, 10 wt%, 5 and 2 wt%). The stability of the synthetized particles was evaluated with 10 redox cycles comparing the results with that of commercial Fe2O3 powders. Al2O3 does not behave as inert material in the process but it actively participates in the reduction step, catalysing coke formation due its acidity. With the sample 98 wt% Fe2O3- 2 wt% Al2O3 the best performances in terms of particles stability and hydrogen purity were obtained.