One of the most important issues for chemical looping technology is to find low-cost oxygen carriers. In the present work, for the first time, we use magnetite ore with high content of Fe3O4 as a low-cost oxygen carrier for chemical looping reforming of methane (CLRM) to coproduce syngas and hydrogen. The possible reactions and feasibility are first demonstrated by thermodynamic analysis. The reactivity of the magnetite oxygen carrier with respect to methane conversion and water steam splitting was studied by continuous operation in a CLRM prototype. In the redox experiments, the produced hydrogen and syngas in a H2/CO molar ratio of 2.0 can be stably obtained with high selectivity (ca. 95.1% for syngas and ca. 96.2% for H2). From the kinetic study via a thermogravimetric analyzer method, it is found that the reduction of original magnetite to wustite is well represented by the phase boundary-controlled (contracting cylinder) mechanism. Based on the kinetic study, ultrasonic treatment was implemented to modify the magnetite oxygen carrier, where significantly improved the activity of magnetite oxygen carrier for methane selective oxidation was achieved. Finally, the evolution of active components, the formation of carbon deposition and the interaction among different components were also discussed in detail.

Chemical looping reforming,methane,magnetite,oxygen carrier,kinetic study