Investigation on ceria- and doped ceria-supported oxygen carriers for CLC applications
Conference contribution, 2011
In the area of chemical-looping combustion as a pathway to CO2 sequestration and subsequent storage, major efforts have concentrated on investigating various oxygen carriers supported on inert materials. So, it would be innovative to utilize supports that are participating in the combustion process and thus can act as a minor but additional oxygen carrier or as a facilitating oxidizing catalyst during CLC operation. One of these materials is cerium dioxide (ceria, CeO2), which is used extensively as an integral component of 3-way catalyst in automobiles. In order to exploit the synergy of a composite made up of the active carrier and the participating support, formulations consisting of two-phase mixtures of copper oxide, iron oxide and manganese oxide with pure or doped ceria were fabricated and evaluated for their reactivity in methane and syngas fuel streams. Relevant parameter of significance to CLC process, such as fuel conversion, oxygen release measurement, fluidization properties and, temperature variations during fuel and oxidation cycles, were examined.
All the samples showed very good fluidization properties during tests without any agglomeration. Copper oxide-based oxygen carriers showed nearly full conversion of methane with high oxygen release and no sign of defluidization, while iron-based systems exhibited unusually high conversion of methane together with favourable reactivity during oxidation periods after the fuel cycles. The superiority of the GDC-supported materials over those supported on ceria could be interrelated to the better oxygen transport capability of the GDC support due to the oxygen ion vacancies in it by virtue of doping.