Chemical looping: To combustion and beyond

Chemical looping combustion (CLC) is a rapidly emerging technology for clean combustion of fossil and renewable fuels which allows production of sequestration-ready CO2 streams with only minor efficiency penalties for CO2 capture. While initial interest in chemical looping was almost exclusively focused on combustion, we demonstrate here that the underlying reaction engineering principle forms a highly flexible platform for fuel conversion: Replacing air with steam or CO2 as oxidizer yields the chemical looping analogue to steam and dry reforming, resulting in the production of high purity hydrogen streams without the need for further clean-up steps and a novel route for efficient CO2 activation via reduction to CO, respectively. Furthermore, by controlling the degree of carrier oxidation, incomplete, i.e. partial oxidation of the fuel to synthesis gas is attained. Finally, appropriate selection of oxygen carrier materials even allows simultaneous de sulfurization of the effluent stream, resulting in a strongly intensified process for highly efficient, low-emission conversion of S-contaminated fuel streams. Based on new results from our own research, the present paper presents a brief overview over the potential of chemical looping processes for methane conversion with a particular focus on the key role of engineered carrier materials as enablers for this class of processes. (C) 2013 Elsevier B.V. All rights reserved.