Physical mixtures as simple and efficient alternative to alloy carriers in chemical looping processes

Abstract

Chemical looping combustion is a clean combustion technology for fossil or renewable fuels. In a previous demonstration, chemical looping was applied to CO₂ activation via reduction to CO with concurrent production of synthesis gas (CO + H₂) from CH₄ via rationally designed Fe-Ni alloys. Here, it is demonstrated that that a simple physical mixture can even outperform the equivalent alloy based on an intricate gas phase mediated coupling between the two metals: Ni cracks methane to carbon and H₂. The latter then reduces iron oxide carrier, forming steam, which gasifies the carbon deposits on Ni to produce a mixture of CO + H₂, thus regenerating the active Ni surface. It was suggested that the principle demonstrated here—the gas phase-mediated coupling of two solid reactants with distinct functionalities—should be applicable broadly toward oxidation reactions and hence opens a new avenue for rational design of chemical looping processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 51–59, 2017