(224b) Direct Decomposition of NO Using Specialized Metal Oxides in a Novel Chemical Looping Reactor System
This study introduces a unique reaction system that counters the drawbacks of the direct catalytic NO decomposition system. The proposed system employs a chemical looping reactor that utilizes a specialized oxygen uncoupling metal oxide for NO decomposition. The flue gas stream containing NO reacts with the metal oxide in a reactor, producing N2 and oxidizing the metal oxide. The oxidized metal oxide is then regenerated at a higher temperature, releasing O2 and creating oxygen vacancies that are essential for NO decomposition in the first reactor. Thus, as the metal oxide does not get consumed in the overall chemical looping system, this technology mimics the direct decomposition reaction with a key difference that it produces N2 and O2 products in two separate streams. This enables the chemical looping system to be governed by a different reaction mechanism than the catalytic system. Several metal oxides have been experimentally screened for their activity towards NO decomposition and stability towards oxygen uptake in a thermogravimetric analyzer (TGA). The TGA weight profiles also gave an insight into the change in reaction kinetics of NO decomposition upon addition of supports and dopants. The effect of CO2 inhibition and reaction temperature have also been tested for two different composite metal oxides. These results have been supported with solid characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman Spectroscopy. Further, ab initio atomistic simulations and density functional theory calculations were performed to understand the reaction mechanism and supplement the experimental results. Finally, fixed bed reaction tests have been performed to investigate the nature of NO breakthrough curves on different metal oxide systems. Findings from this study lay the groundwork for this novel NO abatement process and will facilitate the advancement of this technology.