Thermogravimetric Analysis of Copper Oxide for Chemical-Looping Hydrogen Generation

The chemical-looping hydrogen generation (CLH) system consists of reduction of metal oxide and water decomposition by oxidizing reduced metal oxide. In the present study, water decomposition by the reduction and oxidation of metal oxide (CuO) was conducted in a thermogravimetric analysis (TGA) system for the CLH process. The particles are reduced completely in an atmosphere of synthesis gas (H-2 + CO), and the fully reduced particles decompose water to produce 3.7 L of H-2 per kilogram of metal oxide. The particles prepared by the impregnation exhibits better reactivity than those by coprecipitation and the solid phase method, and the particles supported on Al2O3 exhibit better reactivity than those on SiO2. Based on the TGA, the reduction and oxidation of CuO/Al2O3 prepared via impregnation are characterized by the kinetic equations from the solid-state reaction rate models. The phase-controlled-boundary model was successfully applied to predict the initial stages of reduction and oxidation of the metal oxide, and the activation energies for reduction and oxidation are determined to be 4.13-19.5 and -55.8 kJ/mol, respectively.