To guide the design of chemical-looping combustion (CLC) systems, the use of accurate models is crucial. The reduction kinetics between NiO and CH4 is uncertain, in regards to the most suitable kinetic mechanism and reaction network. A framework for structural identifiability analysis is developed and applied to evaluate the candidate kinetic models for the NiO-CH4 reaction. The identifiability of kinetic parameters of different model structures is analyzed and compared. Models that lack structural identifiability of their kinetic parameters are rejected in the analysis. From a total of 160 possible candidate models, 4 kinetic models are found to be identifiable with respect to their kinetic parameters and distinguishable from different model structures. This structural identifiability analysis paves the way for model-based design of experiments, which is the subject of Part II of this work. (c) 2016 American Institute of Chemical Engineers