Chemical Looping

     Increasing efforts to mitigate greenhouse gas emissions and minimize energy consumption of chemical processes are driving interest in chemical looping — a technology platform that breaks down a reaction into multiple sub-reactions using chemical intermediates (metal oxides).
     The most well-known application of this technology is in hydrocarbon combustion, in which an oxygen-laden compound (i.e., oxygen carrier) shuttles oxygen between oxidants (e.g., air) and a fuel (e.g., coal) in a cyclic manner. During the reduction step, the oxygen carrier donates oxygen to the fuel, producing concentrated CO2 and water vapor. The oxygen-deprived carrier is then replenished with oxygen via the oxidation step, which produces heat and/or hydrogen. A significant benefit of using chemical looping instead of combustion or gasification is that this approach produces a highly pure stream of CO2 that can be sequestered without further processing.
     This article introduces the concept of chemical looping, discusses the various types of chemical-looping reactions, and identifies the advantages of this technology compared to the conventional process scheme. It also discusses the development and characterization of metal-oxide particles, which shuttle oxygen between the oxidant and the fuel. In addition, the article discusses the chemical-looping technologies developed at Ohio State Univ. and their operational efficiencies, economic impacts, and process applications.