Study of the stabilizing effect of Al2O3 and ZrO2 in mixed metal oxides of Cu for hydrogen production through REDOX cycles

An innovative scheme consisting of two steps is an alternate process to the partial oxidation of methane (POX) for the production of hydrogen. In the first step, the required oxygen for this process is supplied through a material that stores oxygen and release it under reducing conditions. Thus, producing synthesis gas through: CH4 + MeO → CO + H2 + Me, where MeO is a metal oxide and Me is the reduced metal. In the second step, Me is re-oxidized using steam to continue producing H2 through: H2O + Me → MeO + H2. Finally, the regenerated MeO is sent back to the first step. To avoid MeO sintering, this must be stabilized by using a solid diffusion barrier to prevent particle growth and consequently loss in activity. In the present study, mixed metal oxides of CuO/Al2O3 and CuO/ZrO2 were evaluated for their performance in REDOX cycles with the aid of thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), temperature programmed reduction (TPR), BET and scanning electron microscopy (SEM). Results show that Al2O3 and ZrO2 are excellent stabilizers for CuO. REDOX activity for CuO/Al2O3 is related to the formation of CuAl2O4 spinel, while CuO/ZrO2 activity is due to the formation of a solid diffusional barrier and enhancement of the dispersion of CuO.