Synthesis gas generation by chemical-looping reforming in a batch fluidized bed reactor using Ni-based oxygen carriers

Chemical-looping reforming (CLR) utilizes the same basic principles as chemical-looping combustion (CLC), being the main difference that the wanted product in CLR is H-2 and CO. Therefore, in the CLR process the air to fuel ratio is kept low to prevent the complete oxidation of the fuel to CO2 and H2O. Ni-based oxygen carriers prepared by impregnation on alumina have been studied in a thermogravimetric analyzer (TGA) and in a batch fluidized bed reactor in order to know its potential for CLR of CH4. In the TGA the reactivity of the oxygen carriers has been determined. In the batch fluidized bed the effect on the gas product distribution produced during reduction-oxidation cycles and on the carbon deposition of different operating conditions, as type of support, reaction temperature, H2O/CH4 molar ratio, and preparation method, has been tested and analyzed. It was found that the support (different types of alumina) used to prepare the oxygen carriers had an important effect on the reactivity of the oxygen carriers, on the gas product distribution, and on the carbon deposition. In addition, for all oxygen carriers prepared, an increase in the reaction temperature and/or in the H2O/CH4 molar ratio produced a decrease in the carbon deposition during the reduction period. Finally, it was observed that the oxygen carriers prepared by a deposition-precipitation method had higher tendency to increase the C deposition than the oxygen carriers prepared by dry impregnation. (C) 2008 Elsevier B.V. All rights reserved.