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(135b) Dopant Modified Iron Based Materials for Fuel Chemical Looping Combustion and Reforming Applications

Authors: 
Guo, M., The Ohio State University
Qin, L., The Ohio State University
Cheng, Z., The Ohio State University
Liu, Y., The Ohio State University
Fan, J. A., Stanford University
Xu, D., The Ohio State University
Fan, L. S., The Ohio State University
The chemical looping technologies have multiple applications in fuel combustion, as well as methane, coal and biomass reforming. With advantages of chemical looping process design, it can result in a dramatic reduction of capital cost required for the process and improvement of carbon utilization efficiency. Oxygen carriers’ properties are the most significant part of the success of chemical looping fuel combustion and reforming processes. The Ohio State University utilizes iron-based materials for oxygen carriers of chemical looping process. Low cost, multiple phases and environmental friendly nature of iron oxide leads to the industrial possibility of chemical looping technology utilization. However, the moderate reactivity and selectivity of iron oxide with fuel reaction still impedes the success of the commercialization of chemical looping process. In details, the low ionic diffusion of oxygen, less active sites on the surface and low adsorption energy of iron oxide hindered its reactivity and selectivity. Dopants on the surface can modify iron oxide redox reactivity by providing active sites for fuel gas adsorption and aliovalent dopants inside the bulk can alter the iron oxide oxygen ionic diffusion by creating schottky defects. In our study, we examine at the nanoscale to characterize undoped, single-dopant and binary-dopant modified iron oxides that undergo redox reactions with fuel gas, such as hydrogen, carbon monoxide and methane. Doped iron oxides are fabricated by sol gel or solid-state synthesis. Afterwards, X-ray Diffractometry (XRD), Scanning electronic microscopy (SEM)/ Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were utilized to determine the structural and morphological modification of iron oxide. The lattice parameters and surface functional groups of iron oxide variation indicate the existence and functions of these dopants. The redox reaction and temperature programming reaction (TPR) are conducted with fuel gases by thermogravimetric analysis (TGA) with Mass spectrometry (MS). The difference among the undoped iron oxide and single / binary dopant modified iron oxides will be discussed in detail. Meanwhile, density functional theory (DFT) calculation studies are used as a guideline for searching for appropriate dopants. Moreover, the understanding of fuel to syngas or fuel combustion mechanism using dopant modification provides us a methodology to improve the reactivity and recyclability of oxygen carriers, which is a promising way to build the oxygen carriers with low cost and high reactivity and selectivity for commercialization success of chemical looping technology.
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