We have developed and demonstrated a novel process to overcome chemical reaction equilibrium constraints on an important reversible industrial chemical reaction by using chemical looping with a non-stoichiometric oxygen-carrier material. We have successfully probed the lattice parameters of the oxygen-carrier material along the length of a lab-scale working reactor bed (12 cm length) in full operation on ID22 at ESRF which proves the principle of operation. The ability to correctly model the thermodynamic parameters of this material will allow for industrial scale implementation of this unprecedented technique. In order to determine the local chemical potential of the solid phase along the length of the reactor bed we must establish the relationship between oxygen occupancy, lattice parameter, and chemical potential as a function of oxygen partial pressure and temperature.