Neutron diffraction to monitor the state of a non-stoichiometric solid employed in chemical looping

An unmixed reaction is a dynamic process in which e.g. a metal oxide (which acts as an oxygen-carrier material) is used to e.g. provide oxygen for a reaction during which the oxide itself undergoes reduction. The reduced oxide or metal is then reoxidised in a second step. Here we perform reoxidation with water in order to produce hydrogen. We intend to look at the state of reactor beds after use in chemical looping. These will be ‘frozen’ and powdered after operation under inert gas to minimise surface reorganisation and changes in bulk oxidation states. The beds for characterisation will be obtained after an oxidation half cycle, a reduction half cycle and, for reference, after 12 hours exposed to a water to hydrogen ratio of unity. This will allow us to determine the average oxidation state of surface and bulk materials after operation.