DECOMPOSITION OF HYDROGEN IODIDE IN THE S-I THERMOCHEMICAL CYCLE OVER Ni CATALYST SYSTEMS

摘要

The Sulphur-Iodine thermochemical cycle for hydrogen production has been investigated by ENEA over the last five years, with a particular focus on chemical aspects. Regarding the hydrogen iodide decomposition, three γ-alumina supported nickel catalysts were produced and characterized, and then tested in terms of catalytic activity and stability by means of a tubular quartz reactor. In particular the relationships between catalytic activity and preparation procedure was investigated. From the experimental data acquired it can be concluded that two of the three catalysts tested demonstrated high catalytic activity, since hydrogen iodide conversion was almost coincident with theoretical equilibrium value. On the other side, for all the catalysts, a gradual but considerable deactivation phenomenon was observed at 500°C, while at a temperature higher than 650°C the catalytic activity was recovered.